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M1 Abrams
M1A1 on a live fire exercise in Iraq, 2003
Type	Main battle tank
Place of origin	United States
Service history
Used by	United States, Australia, Egypt, Kuwait, Saudi Arabia
Wars	Gulf War, Iraq War
Production history
Designer	Chrysler Defense
Designed	1970s
Manufacturer	General Dynamics
Unit cost	US$4.35 million (M1A2)[1]
Produced	1979–present
Variants	M1A1, M1A2, M1A2SEP
Specifications
Weight	67.6 short tons (61.4 tonnes)
Length	Gun forward: 32.04 ft (9.77 m) Hull length: 26.02 ft (7.93 m)
Width	12 ft (3.66 m)
Height	8 ft (2.44 m)
Crew	4 (commander, gunner, loader, driver)
Armor	Chobham, RHA
Primary armament	105 mm M68 rifled cannon (M1) 120 mm M256 smoothbore cannon (M1A1, M1A2, M1A2SEP)
Secondary armament	1 x .50-caliber (12.7 mm) M2HB heavy machine gun 2 x M240 7.62 mm machine guns (1 pintle-mounted, 1 coaxial)
Engine	AGT-1500C multi-fuel turbine engine 1500 hp (1119 kW)
Power/weight	24.5 hp/tonne
Transmission	Allison DDA X-1100-3B
Suspension	Torsion bar
Ground clearance	0.48 m (M1, M1A1) 0.43 m (M1A2)
Operational range	465.29 km (289 mi) With NBC system: 449.19 km (279 mi)
Speed	Road: 67.72 km/h (42 mph) Off-road: 48.3 km/h (30 mph)

The M1 Abrams is a military tank produced in the United States. The M1 is named after General Creighton Abrams, former Army Chief of Staff and commander of the 37th Armored Regiment.

It is a main battle tank, one well armed, heavily armored, and highly mobile offensive mainstay of modern armored ground warfare.^{[citation needed]} Notable features of the M1 Abrams include the use of a powerful gas turbine engine, the adoption of sophisticated composite armor, and separate ammunition storage in a blow-out compartment for crew safety. It is one of the heaviest tanks in service, weighing in at close to 70 tons.

The M1 Abrams entered U.S. service in 1980, replacing the M60 Patton and M48A5. It did, however, serve for over a decade alongside the improved M60A3, which had entered service in 1978. Three main versions of the M1 Abrams have been deployed, the M1, M1A1, and M1A2, incorporating improved armament, protection and electronics. These improvements, as well as periodic upgrades to older tanks have allowed this long-serving vehicle to remain in front-line service. It is the principal combat tank of the United States Army and Marine Corps, and the armies of Egypt, Kuwait, Saudi Arabia, and as of 2007, Australia.

[edit] Background

The first attempt to replace the aging M60 series of tanks was the abortive MBT-70, developed in partnership with West Germany. The M60 Patton was itself a gradual evolution of a design starting with the World War II era M26 Pershing, with a very tall profile, and average armor and weaponry compared to the contemporary Soviet designs. The MBT-70 was very ambitious, like many American weapons programs of the 1960s. It had a gun launched missile system, kneeling suspension, a driver housed in the turret, and various other ideas that ultimately proved unsuccessful. Cancellation of this project paved the way for the much more successful M1 Abrams tank, which did not incorporate most of the troublesome innovations tried by the MBT-70.

[edit] Development

The M1 Abrams was designed by Chrysler Defense (in 1979, General Dynamics Land Systems Division purchased Chrysler Defense Division) and is currently produced by General Dynamics Corporation in Lima, Ohio, and first entered US Army service in 1980. An improved version of the M1, the M1A1, was introduced in 1985. The M1A1 has the M256 120 mm smoothbore cannon developed by Rheinmetall AG of Germany for the Leopard 2, improved armor, and a CBRN protection system. The M1A2 is a further improvement of the M1A1 with a commander's independent thermal viewer and weapon station, position navigation equipment, digital data bus and a radio interface unit. The M1A2 SEP-(System Enhancement Package) added digital maps, FBCB2-(Force XXI Battlefield Command Brigade and Below) capabilities, and an improved cooling system to maintain crew compartment temperature with the addition of multiple computer systems to the M1A2 tank.

A left front view of the XM1 Abrams tank, which replaced the M60 series, during a demonstration on the test range in 1979.

Further upgrades include depleted uranium armor for all variants, a system overhaul that returns all A1s to like-new condition (M1A1 AIM), a digital enhancement package for the A1 (M1A1D), a commonality program to standardize parts between the U.S. Army and the Marine Corps (M1A1HC) and an electronic upgrade for the A2 (M1A2 SEP).

During Operations Desert Shield and Desert Storm and for Bosnia, some M1A1s were modified with armor upgrades. The M1 can be equipped with mine plow and mine roller attachments if needed. The M1 chassis also serves as a basis for the Grizzly combat engineering vehicle and the M104 Wolverine heavy assault bridge.

Over 8,800 M1 and M1A1 tanks have been produced at a cost of $2,350,000–$4,300,000 per unit, depending on the variant.

[edit] Design features

[edit] Armor

Tankers of the 1st Armored Division drive an M1 Abrams tank through the Taunus Mountains north of Frankfurt during Exercise Ready Crucible on February 14, 2005.

The Abrams is protected by Chobham armor, a further development of British "Burlington" armor. Chobham is a composite armor formed by spacing multiple layers of various alloys of steel, ceramics, plastic composites, and kevlar, giving an estimated maximum (frontal turret) 1320-1620 millimeters of RHAe versus HEAT (and other chemical energy rounds) and 940-960 mm versus kinetic energy penetrators.^[2] It may also be fitted with reactive armor over the track skirts if needed (as in the Urban Survival Kit) and Slat armor over the rear of the tank and rear fuel cells to protect against ATGMs. Fuel and ammunition are in armored compartments with blowout panels to protect the crew from the risk of the tank's own ammunition cooking off if the tank is damaged. Protection against spalling is provided by a Kevlar liner. Beginning in 1987, M1A1 tanks received improved armor packages that incorporated depleted uranium (DU) mesh in their armor at the front of the turret and the front of the hull. Armor reinforced in this manner offers significantly increased resistance towards all types of anti-tank weaponry, but at the expense of adding considerable weight to the tank.

The first M1A1 tanks to receive this upgrade were tanks stationed in Germany, since they were the first line of defense against the Soviet Union. US-based tank battalions participating in Operation Desert Storm received an emergency program to upgrade their tanks with depleted uranium armor immediately before the onset of the campaign. M1A2 tanks uniformly incorporate depleted uranium armor, and all M1A1 tanks in active service have been upgraded to this standard as well, the armor thickness believed to be equivalent to 24 inches (610 mm) of RHA. The strength of the armor is estimated to be about the same as similar western, contemporary main battle tanks such as the Leopard 2. The M1A1/M1A2 can survive multiple hits from the most powerful tank munitions (including 120 mm depleted uranium APFSDS) and anti-tank missiles.^{[citation needed]} In the Persian Gulf War, Abrams tanks survived multiple hits at relatively close ranges from Iraqi T-72s and ATGMs. M829A1 "Silver Bullet" APFSDS rounds from other M1A1 Abrams were unable to penetrate the front and side armor (even at close ranges) in friendly fire incidents as well as an incident in which another Abrams tried to destroy an Abrams that got stuck in mud and had to be abandoned.^[3]

In addition to the advanced armor, some Abrams, are equipped with a Missile Countermeasure Device that can impede the function of guidance systems of semiactive control line-of-sight (SACLOS) wire and radio guided anti-tank guided missiles (Russian AT-3, AT-4, AT-5, AT-6 and the like) and thermally and infrared guided missiles. (ATGM)[2]. This device is mounted on the turret roof in front of the Loader's hatch, and can lead some people to mistake Abrams fitted with these devices for the M1A2 version, since the Commander's Independent Thermal Viewer on the latter is mounted in the same place, though the MCD is box-shaped and fixed in place as opposed to cylindrical and rotating like the CITV.

[edit] Armament

U.S. Marine M1A1 firing in Najaf Province, Iraq during a training exercise.

[edit] Main armament

M68A1 rifled gun

The main armament of the original model M1 was the M68A1 105 mm rifled tank gun firing a variety of high explostive anti-tank (HEAT), high explosive, white phosphorus, and a highly efficient and lethal anti-personnel (multiple flechette) round. This gun is a license-built version of the British Royal Ordnance L7 gun. While being a reliable weapon and widely used by both NATO and former Warsaw Pact nations alike, a cannon with lethality beyond the 3 kilometer range was needed to combat newer armor technologies. To attain that lethality, projectile diameter needed to be increased. The M68A1's performance in terms of accuracy and armor-piercing penetration is on par with the M256A1 up to 3000 meters out, but beyond that range the 105mm projectile lacks the kinetic energy to defeat modern armor packages.

M256 smoothbore gun

Washington Army National Guard soldier from 81st Armor Brigade, sets the sights on the main gun of an M1A1 Abrams in Mosul, Iraq on January 8, 2005.

The main armament of the M1A1 and M1A2 is the M256A1 120 mm smoothbore gun, designed by Rheinmetall AG of Germany. The M256A1 is a variant of the Rheinmetall 120 mm L/44 gun carried on the German Leopard 2 on all variants up to the Leopard 2A5. Leopard 2A6 replaced the L/44 barrel with a longer L/55. The newer M256A1 is manufactured under license in the United States by Watervliet Arsenal, New York.

Rounds like the M829A2 were developed specifically to address the threats posed by a T-90 or T-80U tank, given their high level of protection provided the tanks by kontakt-5 Explosive Reactive Armor, and HEAT shaped charge rounds such as the M830, the latest version of which (M830A1) incorporates a sophisticated multi-mode electronic sensing fuse and more fragmentation which allows it to be used effectively against armored vehicles, personnel, and low-flying aircraft. Unlike the Soviet-built tanks it was designed to go up against, the Abrams uses a manual loader rather than an automatic device, due to the belief that having a person reload the gun is faster and more reliable. This decision was proven out as the Soviet-era automatic loading system proved troublesome.^{[citation needed]} Also important in the decision to use a crewmember instead of an automatic loader during the XM-1 development was the fact that autoloaders of the day did not allow for separate ammunition storage in the turret like the M1 was developed with.

A Marine M1A1 Abrams, 2nd Tank Battalion, fires its main gun into a building to provide suppressive counter fire against insurgents in Fallujah, Al Anbar Province, Iraq during Operation Al Fajr, 2004.

The new M1028 120 mm anti-personnel canister cartridge was brought into service early for use in the aftermath of the 2003 invasion of Iraq. It contains 1,098 3/8 inch steel ball projectiles which spread from the muzzle to produce a shotgun effect lethal out to 600 m. The steel balls can be used to clear enemy dismounts, break up hasty ambush sites in urban areas, clear defiles, stop infantry attacks and counter-attacks and support friendly infantry assaults by providing cover-by-fire. The Canister round is also a highly effective breeching round and can level cinder block walls and knock man-sized holes in reinforced concrete walls for infantry raids at distances up to 75 meters.

In addition to this, the new MRM-KE (Mid-Range-Munition Kinetic Energy) is also in development. Essentially a cannon-fired guided round, it has a range of roughly 12 km and uses a KE warhead which is rocket assisted in its final phase of flight. This is intended to be the best penetrator yet, an improvement over the US 3rd generation DU penetrator (estimated penetration 790 mm).

[edit] Secondary armament

U.S. Army M1A2 Abrams tanks maneuver in the streets as they conduct a combat patrol in the city of Tall Afar, Iraq, on February 3, 2005. Note the TAGS shield installed on the loader's M240 machine gun.

The Abrams tank has three machine guns:

1. A .50 cal. (12.7 mm) M2 machine gun in front of the commander's hatch. On the M1, M1IP and M1A1, this gun is on a powered mount and can be fired using a 3× magnification sight, known as the Commander's Weapon Station (CWS for short), while the vehicle is buttoned up. On the M1A2 & M1A2SEP, this gun is on a flex mount (seen at right), the Commander having to expose himself to fire the weapon manually. With the forthcoming TUSK addon kit, an M2 or an Mk 19 grenade launcher can be mounted on the CROWS remote weapons platform (similar to the Protector M151 remote weapon station used on the Stryker family of vehicles).
2. A 7.62 mm M240 machine gun in front of the loader's hatch on a skate mount. Some of these have been fitted with gun shields during the ongoing conflict in Iraq as seen in the image at right, as well as night-vision scopes for low-visibility engagements.
3. A second 7.62 mm M240 machine gun in a coaxial mount. The coaxial MG is aimed and fired with the same computer fire control system used for the main gun.

The turret is fitted with two six-barreled smoke grenade launchers (USMC M1A1's use an eight-barreled version). These can create a thick smoke that blocks both vision and thermal imaging, and can also be armed with chaff. The engine is also equipped with a smoke generator that is triggered by the driver. The Abrams also has provisions for storing an M16 rifle or M4 carbine inside the turret in case the crew is required to leave the tank under potentially hostile conditions; while the crewmen are supplied with the M9 Beretta pistol as a personal sidearm.

[edit] Aiming

Soldiers from the 3rd Infantry Division conduct a counter improvised explosive device mission in Baghdad, Dec. 22, 2007.

The Abrams is equipped with a ballistic fire-control computer that uses data from a variety of sources, including the thermal or daylight Gunner's Primary Sight (GPS), all computing and displaying one of three components of the ballistic solution - lead angle, ammunition type, and range to the target. These three components are determined using a laser rangefinder, crosswind sensor, a pendulum static cant sensor, data on the ammunition type, tank-specific boresight alignment data, ammunition temperature, air temperature, barometric pressure, a muzzle reference sensor (MRS) that determines and compensates for barrel droop at the muzzle due to gravitational pull and barrel heating due to firing or sunlight, and target speed determined by tracking rate tachometers in the Gunner's or Commander's Controls Handles allowing for target speed input into the ballistic solution.

The fire-control system uses this data to compute a firing solution for the gunner. The ballistic solution generated ensures a hit percentage greater than 95 percent at nominal ranges. Either the commander or gunner can fire the main gun. Additionally, the Commander's Independent Thermal Viewer (CITV) on the M1A2 can be used to locate targets and pass them on for the gunner to engage while the commander scans for new targets. In the event of a malfunction or damage to the primary sight system, the main and coaxial weapons can be manually aimed using a telescopic scope boresighted to the main gun known as the Gunner's Auxiliary Sight (GAS). The GAS has two interchangeable reticles; one for HEAT and MPAT (MultiPurpose AntiTank) rounds and one for APFSDS and STAFF (Smart Target-Activated Fire and Forget) ammunition. Turret traverse and main gun elevation can be accomplished with manual handles and cranks in the event of a Fire Control System or Hydraulic System failure. The commander's M2 .50 caliber machine gun on the M1 and M1A1 is aimed by a 3x magnification sight incorporated into the Commander's Weapon Station (CWS), while the M1A2 uses either the machine gun's own iron sights, or a remote aiming system such as the CROWS system when used as part of the TUSK kit. The loader's M240 machine gun is aimed either with the built-in iron sights or with a thermal scope mounted on the machine gun.

[edit] Mobility

A U.S. Army M1A1 Abrams is marshaled away from a US Air Force C-17, after being offloaded at Balad Air Base, Iraq, during Operation Iraqi Freedom.

Driving controls

The M1 Abrams is powered by a 1500 hp (1119 kW) Honeywell AGT1500 (originally made by Lycoming) gas turbine, and a six speed (four forward, two reverse) Allison X-1100-3B Hydro-Kinetic Automatic transmission, giving it a governed top speed of 45 mph (72 km/h) on paved roads, and 30 mph (48 km/h) cross-country. With the engine governor removed, speeds of around 60 mph (100 km/h) are possible on an improved surface; however, damage to the drive train (especially to the tracks) and an increased risk of injuries to the crew can occur at speeds above 45 mph (72 km/h). The tank can be fueled with diesel fuel, kerosene, any grade of motor gasoline, JP-4 jet fuel, or JP-8 jet fuel; the US Army uses JP-8 jet fuel in order to simplify logistics. The Royal Australian Armoured Corps' M1A1 AIM SA uses diesel fuel; it is cheaper and makes practical sense for Australian military logistics.

The gas turbine propulsion system has proven quite reliable in practice and combat, but its high fuel consumption is a serious logistic issue (starting up the turbine alone consumes nearly 11 gallons of fuel).^{[citation needed]} The high speed, high temperature jet blast emitted from the rear of M1 Abrams tanks makes it difficult for the infantry to proceed shadowing the tank in urban combat. The turbine is very quiet when compared to diesel engines of similar power output and produces a significantly different sound from a contemporary diesel tank engine, reducing the audible distance of the sound, thus earning the Abrams the nickname, "whispering death" during its first REFORGER exercise. Future US tanks may return to reciprocating engines for propulsion, as 4-stroke diesel engines have proven quite successful in other modern heavy tanks, e.g. the Leopard 2, Challenger 2 and Merkava. The small size, simplicity, power-to-weight ratio, and easy removal/replacement of the turbine powerpack does, however, present significant advantages over any proposed reciprocating replacement.

The Abrams can be carried by a C-5 Galaxy or a C-17 Globemaster III. The limited capacity (two combat-ready in a C-5, one combat-ready tank in a C-17) caused serious logistical problems when deploying the tanks for the First Gulf War, though there was enough time for 1,848 tanks to be transported by ship.

[edit] Combat history

In World War II, it took a Sherman Tank an average of 17 rounds to destroy an enemy tank 700 meters away. The Abrams, by contrast, can destroy certain enemy tanks by firing, on the move, a single round from 2,000 meters away.^[4] As the Abrams entered service in the 1980s, they would operate alongside M60A3 within the United States military, and with other NATO tanks in numerous Cold War exercises. These exercises usually took place in Western Europe, especially West Germany, but also in some other countries like South Korea. During such training, Abrams crews honed their skills for use against the men and equipment of the Soviet Union. However, by 1991 the USSR had collapsed and the Abrams would have its trial by fire in the Middle East.

[edit] Operation Desert Storm

Abrams main battle tanks of the 3rd Armored Division move out on a mission during Operation Desert Storm. A Bradley IFV and logistics convoy can be seen in the background.

The Abrams remained untested in combat until the Gulf War in 1991. A total of 1,848 M1A1s were deployed to Saudi Arabia. The M1A1 was superior to Iraq's Soviet-era T-55 and T-62 tanks, as well as Iraqi assembled Russian T-72s, and locally-produced copies (Asad Babil tank). The T-72s like most Soviet export designs lacked night vision systems and then-modern range finders, though they did have some night fighting tanks with older active infrared systems or floodlights — just not the latest starlight scopes and passive infrared scopes as on the Abrams. Only 23 M1A1s were taken out of service in the Gulf^[5] and none of these losses resulted in crew deaths from Iraqi fire. Some others took minor combat damage, with little effect on their operational readiness. There were only 3 tank crew members wounded beyond doubt by enemy action.

The M1A1 was capable of making kills at ranges in excess of 2500 m. This range was crucial in combat against tanks of Soviet design in Desert Storm, as the effective range of the main gun in the Soviet/Iraqi tanks was less than 2000 meters (Iraqi tanks could not fire Anti-Tank missiles like their Russian counterparts). This meant Abrams tanks could hit Iraqi tanks before the enemy got in range - a decisive advantage in this kind of combat. In friendly fire incidents, the front armor and fore side turret armor survived direct APFSDS hits from other M1A1s at the front and side armor. This was not the case for the side armor of the hull and the rear armor of the turret, as both areas were penetrated at least in two occasions by friendly DU ammunition during the Battle of Norfolk.^[6]

Nearly all sources claim that no Abrams tank has ever been destroyed as a result of fire from an enemy tank, but some have certainly taken some damage which required extensive repair. There is at least one account, reported in the following Gulf War's US Official Assessment (scan), of an Abrams being damaged by three kinetic energy piercing rounds. The DoD report indicates that witnesses in the field claimed it was hit by a T-72 Asad Babil. The KE rounds were unable to fully penetrate and stuck in the armor, but because of the external damage it was sent to a maintenance depot. This is the only verified case of an M1A1 put out of action by an Iraqi MBT.^[7]

Presumably the impacts set the storage boxes on fire. The tests at the impact point indicate the sabot shells were conventional, since no radiological trace was found there.

Six other M1A1s were allegedly hit by 125 mm tank fire in the Gulf war official report, but the impacts were largely ineffectual.^[8]

M1A1 lost to friendly fire during Operation Desert Storm in 1991.

On the night of February 26, 1991, four Abrams were disabled in a suspected friendly fire incident by Hellfire missiles fired from AH-64 Apache attack helicopters, with the result of some crew members wounded in action.^[9] The tanks were part of TF 1-37,^[10] attacking a large section of Tawakalna Republican Guard Division, their numbers being B-23, C-12, D-

Soldiers from U.S. 3d Armored Cavalry Regiment provide overwatch for troops from their M1 Abrams tank in Biaj, Iraq.

A tank is a tracked armoured vehicle designed for front-line action, combining strong offensive and defensive capabilities. For offense the tank carries a large calibre gun and machine guns while heavy armour and good all-terrain mobility provide protection for the tank and its crew.

Tanks were first manufactured during World War I in an effort to break the deadlock of trench warfare. The British Army realized that they required a vehicle that had the mobility to reach the enemy trenches over barbed wire and rough terrain, the armour to withstand small arms fire and shrapnel from artillery and the weaponry to suppress or destroy enemy infantry, machine gun nests and pillboxes.

Today, tanks are among the most formidable and versatile weapons on the battlefield. They are valued for their ability to engage a wide range of ground targets, including enemy tanks and fortifications, as well as their shock value against infantry. In the ongoing race for battlefield supremacy, tanks and armored tactics have undergone continuous evolution for nearly a century. Although the main battle tank is generally considered a key component of modern armies, recent thinking has challenged the need for such powerful and expensive weaponry in a period characterized by unconventional and asymmetric warfare.

Tanks seldom operate alone, being organized into armoured units. Despite their apparent invulnerability, without combined arms support tanks are vulnerable to specialized anti-tank artillery, helicopters and aircraft, enemy tanks, anti-tank and improvised mines, and (at short ranges) infantry.^[1]

Perhaps the greatest tribute to the impact of the tank on modern warfare is the variety of methods that have been developed to destroy or neutralise them.

[edit] History

Main article: History of the tank

[edit] World War I: The tank is born

Main article: Tanks in World War I

Video clip of World War I tanks helping the Allies with an advance in Langres, France(1918).

British World War I Mark IV tank with experimental "Tadpole Tail"

The first proposal for a tank was by the Austrian Oberleutenant Günther Burstyn who, in 1911, proposed a design for "motor artillery" (Motorengeschütz) with a turret, but his design never progressed beyond a German patent in 1912.^{[citation needed]}

Tank or "landship" development, originally conducted by the British Navy under the auspices of the Landships Committee was sponsored by the First Lord of the Admiralty, Winston Churchill and proceeded through a number of prototypes culminating in the Mark I tank prototype 'Mother'.^[2] The first tank to engage in battle was named "D1", a British Mark I, during the Battle of Flers-Courcellette on 15 September 1916.^[3] For further information on British World War I tank actions, see Tanks in World War I.

In contrast to World War II, Germany fielded very few tanks during WWI, with only 15 of the A7V type being produced in Germany during the war.^[4] The first tank versus tank action took place on 24 April 1918 at Villers-Bretonneux, France, when three British Mark IVs met three German A7Vs.

Mechanical problems, poor mobility and piecemeal tactical deployment limited the military significance of the tank in World War I and the tank did not fulfil its promise of rendering trench warfare obsolete. None the less, it was clear to military thinkers on both sides that tanks would play a significant role in future conflicts.^[2]

[edit] Interwar years: Experiments

In the inter-war period tanks underwent further mechanical development and, in terms of tactics, J.F.C. Fuller's doctrine of spearhead attacks with massed tank formations was the basis for work by Heinz Guderian in Germany, Percy Hobart in Britain, Adna R. Chaffee, Jr. in the U.S., Charles de Gaulle in France, and Mikhail Tukhachevsky in the USSR. All came to similar conclusions, but in the Second World War only Germany would put the theory into practice on a large scale, and it was their superior tactics and French blunders, not superior weapons, that made blitzkrieg so successful in May 1940.^[5] For information regarding tank development in this period, see tank development between the wars.

Germany, Italy and the Soviet Union all experimented heavily with tank warfare during their clandestine and/or 'volunteer' involvement in the Spanish Civil War, which saw some of the earliest examples of successful combined arms - such as when Republican troops, equipped with Russian-supplied medium tanks and supported by aircraft, eventually routed Italian troops fighting for the Nationalists in the seven-day Battle of Guadalajara in 1937.^[6]

[edit] World War II: Blitzkrieg and combined arms

Main article: Tanks in World War II

German Tiger I heavy tank of WWII captured in Tunis, 1943.

British Matilda II infantry tank advancing through Egypt as part of Operation Compass, 1941.

Soviet T-34 medium tanks advancing near Leningrad, 1942.

World War II was the first conflict where armoured vehicles were critical to success on the battlefield. During the German Invasion of Poland (1939) the Germans used a combination of Panzer I (a training tank), Panzer II light tanks, and captured Czechoslovakian tanks (Panzer 35(t) and Panzer 38(t)). Early war German tanks sacrificed firepower and protection for mobility and reliability. In contrast, the French had good tanks like the Somua S35 and Char B1 but employed a defensive strategy and had poor tank command and control systems, lacking radios in many of their tanks and headquarters.^[5] The French and British used a range of tank designs with different roles (see British tank classification). One of the more successful British tanks of the war was the Matilda tank.

The German doctrine of blitzkrieg or "Lightning War" made use of radios in all of the tanks to provide command and control, which made them more effective tank for tank than their Allied opponents in the Battle of France, despite the Allied machines being more than a match for the panzers one-on-one. German tanks bypassed enemy strong-points and could radio for close air support to destroy them, or leave them to the infantry on foot. A related development, mechanized infantry, allowed some of the troops to keep up with the tanks and create (for the period) highly mobile combined arms forces.

By 1941, the Germans had the newer Panzer III and Panzer IV tanks with which to invade the Soviet Union in Operation Barbarossa. In an echo of the Battle of France the Soviets had several good tanks and one superb tank design, the T-34. German crews were initially shocked by the excellent all-round performance of the T-34 and the protection and firepower of the KV-1. As before, the rigid Soviet command structure and poor leadership allowed their machines to be surrounded and destroyed in detail, but the Germans could not precipitate the same tactical and strategic panic as they had in France; instead they found an enemy that doggedly kept fighting without food, water and communications.^[7] Despite early successes against the Soviets, the Germans began up-gunning their Panzer IVs, and eventually built larger Panther and Tiger tanks to (ultimately unsuccessfully) deal with the Soviet tank threat.

When entering WWII American mass production capacity enabled her to rapidly construct thousands of relatively cheap Sherman tanks. A compromise all round, the Sherman was reliable and formed a large part of the Anglo-American combined arms forces, but they were easily destroyed by the superior German Panther and Tiger tanks. In terms of tank warfare, large numbers allowed the Americans to overrun the German forces during the Battle of Normandy. The Sherman Firefly was introduced to improve the Sherman's firepower, but concerns about protection remained.

Tank chassis were adapted to a wide range of military jobs, including mine-clearing and combat engineering tasks. Specialised self-propelled guns were also developed: artillery, tank destroyers, and assault guns were essentially cheap, stripped down tanks carrying large calibre guns, often in a fixed hull mounting. German and Soviet assault guns, like the SU-122 had the heaviest guns mounted in vehicles, but by the end of the war a gun turret was recognised as the most effective mounting for the main gun to allow movement in a different direction from firing. Improved suspension systems were developed that allowed better cross-country performance and firing while moving. Systems like the earlier Christie or later torsion bar suspension developed by Ferdinand Porsche dramatically improved the tank's cross-country performance and overall mobility.^[8]

By the end of the war all forces had dramatically increased their tanks' firepower and armour; for instance, the ten ton Panzer I had only two machine guns; at war's end, the standard German medium tank, the Panzer V or Panther tank mounted a powerful, high-velocity 75 mm gun and weighed forty-five tonnes but had mobility comparable to the Panzer I.

[edit] The Cold War: Tanks in the arms race

Main article: Tanks in the Cold War

British Centurion in service from 1946 onwards.

Polish T-55A in service from 1947 onwards.

American M48 Patton in service from 1952 onwards.

During the Cold War, the two opposing forces in Europe were the Warsaw Pact countries on the one side, and the NATO countries on the other side. The Warsaw Pact was seen by the West as having an aggressive force outnumbering the NATO forces and tank development proceeded largely as it had during WWII to maintain the balance of power. The essence of tank designs during the Cold War had been hammered out in the closing months of World War II. Large turrets, capable suspension systems, greatly improved engines, sloped armour and large caliber (100mm+) guns were all introduced to tanks during WWII. Tank design during the Cold War built on this foundation and included improvements to fire control, gun stabilisation, communications and crew comfort. Armour technology progressed in an ongoing race against improvements in anti-tank weapons, especially antitank guided missiles like the TOW.

Medium tanks of WWII gradually evolved into the Main Battle Tank of the Cold War and took over all tank roles on the battlefield. This transition happened gradually in the 1950s, as it was realized that medium tanks could carry guns (such as the US 90 mm, Soviet 100 mm, and the excellent British L7 105 mm) that could penetrate any practical thickness of armour plate at long range. The WWII concept of heavy tanks, armed with the most powerful guns and heaviest armour became obsolete, since they were just as vulnerable as other vehicles to the new medium tank guns. Likewise, WWII had shown that lightly-armed, lightly-armoured tanks were of little value in most roles; speed was not a substitute for armour and firepower.

The main battle tank (MBT) thus took on the role the British had once called the 'Universal tank', filling all battlefield tank roles. Among the classic tanks of the 1950s were the British Centurion, the Soviet T-55 series, and the US M48 series. These three basic vehicles were upgraded significantly over time and formed the bulk of the armoured forces of NATO and the Warsaw Pact throughout the Cold War. Some of them remain in use in the 21st century.

Although the basic roles and traits of tanks were almost all developed by the end of WWI, the performance, firepower and protection of twenty-first century tanks has increased by an order of magnitude over the early prototypes. Tanks have evolved dramatically in response to continually changing threats and requirements and especially in response to the threat of other tanks.

[edit] The 21st century: American Operations in Iraq from 2003 onward

As of 2005, there were 1,100 M1 Abrams used by the United States army in the course of the Iraq War, and they have proven to have an unexpectedly high level of vulnerability to roadside bombs.^[9] A relatively new type of remotely-detonated mine, the explosively formed penetrator has been used with some success against American armoured vehicles (particularly the Bradley fighting vehicle). However, with upgrades to their armour in the rear, M1s have proven invaluable in fighting insurgents in urban combat (a role that tactics otherwise proscribe), particularly at the Battle of Fallujah, where the Marines brought in two extra brigades.^[10] Britain deployed its Challenger 2 tanks to support its operations in southern Iraq.

[edit] Tank design

Russian T-90 during an exercise south of Moscow

The three traditional factors determining a tank's effectiveness in battle are its firepower, protection, and mobility. In practical terms, the cost to manufacture and maintain a given tank design is also important in that it determines how many tanks a nation can afford to field.

Firepower is the ability of a tank to identify, engage, and destroy a target. Protection is the tank's ability to resist being detected, engaged, and disabled or destroyed by enemy fire. Mobility includes tactical (short range) movement over the battlefield including over rough terrain and obstacles, as well as strategic (long range) mobility, the ability of the tank to be transported by road, rail, sea, and/or air, to the battlefield.

Tank design is a compromise; it is not possible to maximize firepower, protection and mobility simultaneously. For example, increasing protection by adding armour will result in an increase in weight and therefore decrease mobility; increasing firepower by installing a larger gun will force the designer to sacrifice speed or armour to compensate for the added weight and cost.

Since WWII tank development has shifted focus from experimenting with large scale mechanical changes to the tank design to focussing on technological advances in the tank's subsystems to improve its performance.

Further information: Tank classification

[edit] Firepower

Main article: Tank gun

American M1 Abrams firing.

Camouflaged Leopard 2 of the German Army.

With respect to tanks, firepower means the ability to rapidly detect, identify, engage and destroy targets on the battlefield.

The main weapon of all modern tanks is a single, large caliber (105 to 125mm) gun mounted in a fully traversing turret. The typical tank gun is a smoothbore weapon capable of firing armour-piercing kinetic energy penetrators (KEP), also known as armour-piercing discarding sabot (APDS), and high explosive anti-tank (HEAT) shells and/or anti-tank guided missiles (ATGM) to destroy armoured targets, as well as high explosive (HE) shells for engaging soft targets or fortifications. A modern type of tank ordnance arising from the close range urban combat in Iraq is a 120mm caliber "shotgun" round for the M1 Abrams which will fire 1100 tungsten pellets.^[10]

A gyroscope is used to stabilise the main gun, reducing the effect of manoeuvring on accuracy. Modern tank guns are also commonly fitted with insulating thermal jackets to reduce gun-barrel warping caused by uneven thermal expansion, bore evacuators to minimise fumes entering the crew compartment and (less often) muzzle brakes to minimise the effect of recoil on accuracy and rate of fire.

Modern target detection relies on telescopic periscopes and sophisticated light intensification and thermal imaging equipment to improve fighting capability at night, in poor weather and in smoke. The accuracy of modern tank guns is pushed to the mechanical limit by computerized fire control systems. The fire control system uses a laser range-finder to detect the range to the target, a thermocouple, anemometer and wind vane to correct for weather effects and a muzzle referencing system to correct for gun-barrel temperature, warping and wear. Two sightings of a target with the range-finder enable calculation of the target movement vector. This information is combined with the known movement of the tank and the principles of ballistics to calculate the elevation and aim point that maximises the probability of destroying the target.

Usually, tanks carry small calibre (7.62 to 20mm) armament for short range defence where fire from the main weapon would be ineffective, for example when engaging infantry, light vehicles or aircraft. Typical mountings for these light weapons are coaxially with the main gun and on a roof mounting.

[edit] Protection

See also: Anti-tank warfare

German Panther illustrating early use of camouflage.

An M1 Abrams tank on lookout. Heat haze from the turbine engine can be seen to the rear.

A tank's protection is the combination of its ability to avoid detection, to avoid being hit by enemy fire, its armour to resist the effects of enemy fire, and to sustain damage and complete its mission, or at least protect its crew. In common with most unit types, tanks are subject to additional hazards in wooded and urban combat environments which largely negate the advantages of the tank's long-range firepower and mobility, limit the crew's detection capabilities and can restrict turret traverse. Despite these disadvantages, tanks retain high survivability against previous generation RPGs in all combat environments by virtue of their armour. By contrast, tank survivability against newer generation tandem-warhead anti-tank missiles is a concern for military planners.^[11]

[edit] Avoiding detection

A tank avoids detection using the doctrine of CCD: camouflage (looks the same as the surroundings), concealment (cannot be seen) and deception (looks like something else).

Working against efforts to avoid detection is the fact that a tank is a large metallic object with a distinctive, angular silhouette that emits copious heat and noise when mobile. Consequently, it's difficult to effectively camouflage a hull-up tank in the absence of some form of cover or concealment (eg. woods). The tank becomes easier to detect when mobile due to the large, distinctive auditory, vibration and thermal signatures of a powerplant with an output comparable to that of a diesel locomotive.^{[citation needed]} Tank tracks and dust clouds also betray past or present tank movement. Powered down tanks are vulnerable to infra-red detection due to differences between the thermal conductivity and therefore heat dissipation of the metallic tank and its surroundings. At close range the tank can be detected even when powered down and fully concealed due to the column of warmer air above the tank and the smell of diesel.

Thermal blankets slow the rate of heat emission and camouflage nets use a mix of materials with differing thermal properties to operate in the infra-red as well as the visible spectrum. Camouflage attempts to break up the distinctive appearance and silhouette of a tank. Adopting a turret-down or hull-down position reduces the visible area of a tank as well as providing the added protection of a position in defilade.

[edit] Armour

Main article: Vehicle armour

Recent modifications to the M1A2 Abrams to improve survivability in an urban environment.

When protection fails: M1A1 Abrams lost during combat against the Tawakalna Republican Guard Division, February 26 1991.

To effectively protect the tank and its crew, tank armour must counter a wide variety of anti-tank threats. Protection against kinetic energy penetrators and high explosive anti-tank (HEAT) shells fired by other tanks is of primary importance, but tank armour must also aim to protect against infantry anti-tank missiles, anti-tank mines, bombs, direct artillery hits, and (less often) nuclear, bacterial and chemical threats, any of which could disable or destroy a tank and/or its crew.

Steel armour plate was the earliest type of armour. The Germans pioneered the use of face hardened steel during WWII and the Soviets also achieved improved protection with sloped armour technology. WWII developments also spelled the eventual doom of homogeneous steel armour with the development of shaped charge warheads, exemplified by the Panzerfaust and bazooka infantry weapons which were lethally effective, despite some early success with spaced armour.

British tank researchers took the next step with the development of Chobham armour, or more generally composite armour, incorporating ceramics and plastics in a resin matrix between steel plates, which provided good protection against early HEAT weapons. Magnetic mines led to the development of anti-magnetic paste and paint, squash head warheads led to Kevlar (or equivalent) anti-spall armour linings, and KEPs led to the inclusion of exotic materials like depleted uranium in the composite matrix. Reactive armour consists of small explosive "bricks" that detonate when damaged by HEAT fire, bending or disrupting the incoming molten metallic jet. Tandem warheads defeat reactive armour by causing the armour to detonate prematurely. Grenade launchers which can rapidly deploy a smoke screen and the modern Shtora soft-kill countermeasure system provide additional protection by disrupting enemy targeting and fire control systems.

The latest generation of protective measures for tanks are active protection systems, particularly hard-kill countermeasures. The Israeli TROPHY and Iron Fist, the American Quick Kill, and the Russian Drozd and Arena systems show the potential to dramatically improve protection for tanks against missiles, RPGs and potentially KEP attacks, but concerns regarding friendly fire against dismounted crew and nearby infantry remain.

[edit] Mobility

The mobility test of Arjun MBT in a test track.

A Leclerc crossing a gap.

T-72 Ajeya of the Indian Army during an exercise. Note the reactive armour.

The mobility of a tank is described by its

A colored automobile engine

The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. This exothermic reaction creates gases at high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement of solid parts of the engine, by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.

This contrasts with external combustion engines, such as steam engines and Stirling engines, which use an external combustion chamber to heat a separate working fluid, which then in turn does work, for example by moving a piston or a turbine.

The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating piston engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as jet engines, most rockets and many gas turbines are also internal combustion engines.

[edit] History

Early internal combustion engines were used to power farm equipment similar to these models.

The first internal combustion engines did not have compression, but ran on an air/fuel mixture sucked or blown in during the first part of the intake stroke. The most significant distinction between modern internal combustion engines and the early designs is the use of compression and, in particular, in-cylinder compression.

• 1206: Al-Jazari described a double-acting reciprocating piston pump with a crankshaft-connecting rod mechanism.
• 1509: Leonardo da Vinci described a compressionless engine.
• 1673: Christiaan Huygens described a compressionless engine.
• 17th century: English inventor Sir Samuel Morland used gunpowder to drive water pumps, essentially creating the first rudimentary internal combustion engine.
• 1780's: Alessandro Volta built a toy electric pistol ([1]) in which an electric spark exploded a mixture of air and hydrogen, firing a cork from the end of the gun.
• 1794: Robert Street built a compressionless engine whose principle of operation would dominate for nearly a century.
• 1806: Swiss engineer François Isaac de Rivaz built an internal combustion engine powered by a mixture of hydrogen and oxygen.
• 1823: Samuel Brown patented the first internal combustion engine to be applied industrially. It was compressionless and based on what Hardenberg calls the "Leonardo cycle," which, as the name implies, was already out of date at that time.
• 1824: French physicist Sadi Carnot established the thermodynamic theory of idealized heat engines. This scientifically established the need for compression to increase the difference between the upper and lower working temperatures.
• 1826 April 1: American Samuel Morey received a patent for a compressionless "Gas or Vapor Engine."
• 1838: a patent was granted to William Barnet (English). This was the first recorded suggestion of in-cylinder compression.
• 1854: The Italians Eugenio Barsanti and Felice Matteucci patented the first working efficient internal combustion engine in London (pt. Num. 1072) but did not go into production with it. It was similar in concept to the successful Otto Langen indirect engine, but wasn't so well worked out in detail.
• 1856: in Florence at Fonderia del Pignone (now Nuovo Pignone, a subsidiary of General Electric), Pietro Benini realized a working prototype of the Barsanti-Matteucci engine, supplying 5 HP. In subsequent years he developed more powerful engines—with one or two pistons—which served as steady power sources, replacing steam engines.
• 1860: Belgian Jean Joseph Etienne Lenoir (1822–1900) produced a gas-fired internal combustion engine similar in appearance to a horizontal double-acting steam beam engine, with cylinders, pistons, connecting rods, and flywheel in which the gas essentially took the place of the steam. This was the first internal combustion engine to be produced in numbers.
• 1862: German inventor Nikolaus Otto designed an indirect-acting free-piston compressionless engine whose greater efficiency won the support of Langen and then most of the market, which at that time was mostly for small stationary engines fueled by lighting gas.
• 1870: In Vienna, Siegfried Marcus put the first mobile gasoline engine on a handcart.
• 1876: Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, developed a practical four-stroke cycle (Otto cycle) engine. The German courts, however, did not hold his patent to cover all in-cylinder compression engines or even the four-stroke cycle, and after this decision, in-cylinder compression became universal.

Karl Benz

• 1879: Karl Benz, working independently, was granted a patent for his internal combustion engine, a reliable two-stroke gas engine, based on Nikolaus Otto's design of the four-stroke engine. Later, Benz designed and built his own four-stroke engine that was used in his automobiles, which became the first automobiles in production.
• 1882: James Atkinson invented the Atkinson cycle engine. Atkinson’s engine had one power phase per revolution together with different intake and expansion volumes, making it more efficient than the Otto cycle.
• 1891: Herbert Akroyd Stuart built his oil engine, leasing rights to Hornsby of England to build them. They built the first cold-start compression-ignition engines. In 1892, they installed the first ones in a water pumping station. In the same year, an experimental higher-pressure version produced self-sustaining ignition through compression alone.
• 1892: Rudolf Diesel developed his Carnot heat engine type motor burning powdered coal dust.
• 1893 February 23: Rudolf Diesel received a patent for the diesel engine.
• 1896: Karl Benz invented the boxer engine, also known as the horizontally opposed engine, in which the corresponding pistons reach top dead center at the same time, thus balancing each other in momentum.
• 1900: Rudolf Diesel demonstrated the diesel engine in the 1900 Exposition Universelle (World's Fair) using peanut oil (see biodiesel).
• 1900: Wilhelm Maybach designed an engine built at Daimler Motoren Gesellschaft—following the specifications of Emil Jellinek—who required the engine to be named Daimler-Mercedes after his daughter. In 1902 automobiles with that engine were put into production by DMG.
• 1908: New Zealand inventor Ernest Godward started a motorcycle business in Invercargill and fitted the imported bikes with his own invention – a petrol economiser. His economisers worked as well in cars as they did in motorcycles.

[edit] Applications

Internal combustion engines are most commonly used for mobile propulsion in automobiles, equipment, and other portable machinery. In mobile equipment, internal combustion is advantageous, since it can provide high power-to-weight ratios together with excellent fuel energy-density. These engines have appeared in transport in almost all automobiles, trucks, motorcycles, boats, and in a wide variety of aircraft and locomotives, generally using petroleum (called All-Petroleum Internal Combustion Engine Vehicles or APICEVs). Where very high power is required, such as jet aircraft, helicopters and large ships, they appear mostly in the form of turbines.

They are also used for electric generators (i.e., 12V generators) and by industry.

[edit] Operation

Four-stroke cycle (or Otto cycle)
1. Intake
2. compression
3. power
4. exhaust

All internal combustion engines depend on the exothermic chemical process of combustion: the reaction of a fuel, typically with the oxygen from the air, although other oxidizers such as nitrous oxide may be employed. Also see stoichiometry.

The most common modern fuels are made up of hydrocarbons and are derived mostly from petroleum. These include the fuels known as dieselfuel, gasoline and petroleum gas, and the rarer use of propane gas. Most internal combustion engines designed for gasoline can run on natural gas or liquefied petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous biofuels, such as ethanol and biodiesel (a form of diesel fuel that is produced from crops that yield triglycerides such as soybean oil), can also be used. Some can also run on hydrogen gas.

All internal combustion engines must achieve ignition in their cylinders to create combustion. Typically engines use either a spark ignition (SI) method or a compression ignition (CI) system. In the past, other methods using hot tubes or flames have been used.

[edit] Petroleum internal combustion engines

Main article: Petroleum

[edit] Gasoline Ignition Process

Electrical/gasoline-type ignition systems (that can also run on other fuels, as previously mentioned) generally rely on a combination of a lead-acid battery and an induction coil to provide a high-voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery can be recharged during operation using an electricity-generating device such as an alternator or generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress to less than 185 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder.

[edit] Diesel Ignition Process

Diesel Engine ignition systems, such as the diesel engine and HCCI engines, rely solely on heat and pressure created by the engine in its compression process for ignition. The compression that occurs is usually more than three times higher than a gasoline engine. Diesel engines will take in air only, and shortly before peak compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air and fuel but continue to rely on an unaided auto-combustion process due to higher pressures and heat. This is also why diesel and HCCI engines are also more susceptible to cold starting issues, though they will run just as well in cold weather once started. Most diesels also have battery and charging systems; however, this system is secondary and is added by manufacturers as luxury for ease of starting, turning fuel on and off (which can also be done via a switch or mechanical apparatus), and for running auxiliary electrical components and accessories. Most new engines, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions.

[edit] Energy and pollution

Once ignited and burnt, the combustion products—hot gases—have more available energy than the original compressed fuel/air mixture (which had higher chemical energy). The available energy is manifested as high temperature and pressure which can be translated into work by the engine. In a reciprocating engine, the high-pressure gases inside the cylinders drive the engine's pistons.

Once the available energy has been removed, the remaining hot gases are vented (often by opening a valve or exposing the exhaust outlet) and this allows the piston to return to its previous position (top dead center, or TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any heat not translated into work is normally considered a waste product and is removed from the engine either by an air or liquid cooling system.

[edit] Engine Efficiency

Engine efficiency can be discussed in a number of ways but usually involves a comparison of the total chemical energy in the fuels and the useful energy abstracted from the fuels in the form of kinetic energy. The most fundamental and abstract discussion of engine efficiency is the thermodynamic limit for abstracting energy from the fuel defined by a thermodynamic cycle. The most comprehensive is the empirical fuel economy of the total engine system for accomplishing a desired task, for example miles per gallon.

Internal combustion engines are primarily heat engines and as such the phenomenon that limits their efficiency is described by thermodynamic cycles. None of these cycles exceed the limit defined by the Carnot cycle which states that the overall efficiency is dictated by the difference between the lower and upper operating temperatures of the engine. A terrestrial engine is usually fundamentally limited by the upper thermal stability of the material used to make the engine. All metals and alloys eventually melt or decompose, there is significant research into ceramic materials that can be made with higher thermal stabilities and desirable structural properties. Higher thermal stability allows for greater temperature difference between the lower and upper operating temperatures and thus greater thermodynamic efficiency.

The thermodynamic limits assume that the engine is operating in ideal conditions. A frictionless world, ideal gases, perfect insulators, and operation at infinite time. The real world is substantially more complex and all the complexities reduce efficiency. In addition real engines run best at specific loads and rates as described by their power curve. For example a car cruising on a highway is usually operating significantly below it ideal load. The engine is designed for the higher loads desired for rapid acceleration. The application engines are used for contribute drag on the total system reducing overall efficiency, for example wind resistance for vehicles. These and many other losses result in a engines real world fuel economy, usually measured in the units of miles per gallon (or kilometers per liter) for automobiles. In the MPG the miles represents a meaningful amount of work and the volume of hydrocarbon implies a standard energy content.

Most steel engines have a thermodynamic limit of at most 37%. Even when aided with turbochargers and stock efficiency aids most engines retain an average efficiency of about 20% ^[1][2].

There are many inventions concerned with increasing the efficiency of IC-Engines. In general, practical engines are always compromises, or trade-off´s, between different properties, such as efficiency, weight, power, response, exhaust emissions, noise etc. etc. Sometimes economy also plays a role, not only as the cost of manufacturing the engine itself, but also manufacturing and distribution of the fuel. Increasing the engine efficiency brings a better fuel economy, but only if the fuel cost per energy content is the same.

[edit] Air and noise pollution

Internal combustion engines—particularly reciprocating internal combustion engines—produce air pollution emissions, due to incomplete combustion of carbonaceous fuel. The main derivatives of the process are carbon dioxide CO₂, water and some soot, also called particulate matter (PM). The effects of inhaling particulate matter has been widely studied in humans and animals and include asthma, lung cancer, cardiovascular issues, and premature death. There are however some additional products of the combustion process that include nitrogen oxides and sulfur and some uncombusted hydrocarbons, depending on the operating conditions and the fuel/air ratio.

The fuel does not get completely burned in the engine and passes through the exhaust unchanged. The primary causes of this are the need to operate near the stoichiometric ratio for gasoline engines in order to achieve combustion (the fuel would burn more completely in excess air) and the "quench" of the flame by the relatively cool cylinder walls. Quenching is commonly observed in diesel (compression ignition) engines that run on natural gas, when running at lower speed. It reduces the efficiency and increases knocking and sometimes causes the engine to stall. Increasing the amount of air in the engine reduces the amount of the first two pollutants but tends to encourage the oxygen and nitrogen in the air to combine to produce Nitrogen Oxides (NOx), demonstrated to be hazardous to both plant and animal health. Further chemicals released are Benzene and 1,3-Butadiene that are particularly harmful. Not all the fuel burns up completely, so Carbon Monoxide (CO) is also produced.

Carbon fuels contain sulfur and impurities, leading to sulfur oxides (SOx) and Sulphur Dioxide (SO2) in the exhaust, promoting acid rain. One final element in exhaust pollution is Ozone (O3). This is not emitted directly but made in the air by the action of sunlight on other pollutants to form "ground level Ozone", which, unlike the "Ozone Layer" in the high atmosphere, is regarded as a bad thing if levels are too high. Ozone is actually broken down by Nitrogen Oxides, so one tends to be lower where the other is higher.

For the pollutants described above (Nitrogen Oxides, Carbon Monoxide, Sulphur Dioxide, and Ozone) there are accepted levels, set by legislation, at which no harmful effects are observed even in sensitive population groups. For the other three (Benzene, 1:3 butadiene and particulates) there is no way of proving they are safe at any level, so the experts set standards where the risk to health is "exceedingly small".

Finally, significant contributions to noise pollution are made by internal combustion engines. Most of this noise produced is due to automobile and truck traffic operating on highways and street systems.

[edit] Parts

An illustration of several key components in a typical four-stroke engine

For a four-stroke engine, key parts of the engine include the crankshaft (purple), one or more camshafts (red and blue), and valves. For a two-stroke engine, there may simply be an exhaust outlet and fuel inlet instead of a valve system. In both types of engines, there are one or more cylinders (grey and green), and for each cylinder, there is a spark plug (darker-grey), a piston (yellow), and a crank (purple). A single sweep of the cylinder by the piston in an upward or downward motion is known as a stroke. The downward stroke that occurs directly after the air/fuel mix passes from the carburetor or fuel injector to the cylinder where it is ignited is known as a power stroke.

A Wankel engine has a triangular rotor that orbits in an epitrochoidal (figure 8 shape) chamber around an eccentric shaft. The four phases of operation (intake, compression, power, exhaust) take place in what is effectively a moving, variable-volume chamber.

A Bourke Engine uses a pair of pistons integrated to a Scotch Yoke that transmits reciprocating force through a specially designed bearing assembly to turn a crank mechanism. Intake, compression, power, and exhaust occur in each stroke.

[edit] Classification

At one time, the word "engine" (from Latin, via Old French, ingenium, "ability") meant any piece of machinery — a sense that persists in expressions such as siege engine. A "motor" (from Latin motor, "mover") is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines," but combustion engines are often referred to as "motors." (An electric engine refers to locomotive operated by electricity).

However, many people consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work.

[edit] Principles of operation

A 1906 gasoline engine

Reciprocating:

• Crude oil engine
• Two-stroke cycle
• Four-stroke cycle
• Six stroke engine
• Hot bulb engine
• Diesel engine
• Poppet valves
• Sleeve valve
• Atkinson cycle
• Free-piston engine

• Proposed
  • Bourke engine
• Improvements
• Controlled Combustion Engine

Rotary:

• Demonstrated:
  • Wankel engine
  • Nutating disc engine
• Proposed:
  • Differential-Stroke Cycle (D-Cycle) Engine
  • Orbital engine
  • Quasiturbine
  • Rotary Atkinson cycle engine
  • Toroidal engine
  • Trochilic engine

Continuous combustion:

• Gas turbine
• Jet engine
• Rocket engine

[edit] Engine cycle

[edit] Two-stroke

Main article: Two-stroke cycle

Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh charge in the crankcase, which is then blown through the cylinder through ports in the cylinder walls.

Spark-ignition two-strokes are small and light for their power output and mechanically very simple; however, they are also generally less efficient and more polluting than their four-stroke counterparts. However, in single-cylinder small motor applications, cc for cc,(cc meaning cubic centimeter), a two-stroke engine produces much more power than equivalent 4 strokes, due to the enormous advantage of having 1 power stroke for every 360 degrees of crankshaft rotation (compared to 720 degrees in a 4 stroke motor).

Small displacement, crankcase-scavenged two-stroke engines have been less fuel-efficient than other types of engines when the fuel is mixed with the air prior to scavenging, allowing some of it to escape out of the exhaust port. Modern designs (Sarich and Paggio) use air-assisted fuel injection, which avoids this loss, and are more efficient than comparably sized four-stroke engines. Fuel injection is essential for a modern two-stroke engine in order to meet ever more stringent emission standards.

Research continues into improving many aspects of two-stroke motors, including direct fuel injection, amongst other things. Initial results have produced motors that are much cleaner burning than their traditional counterparts.

Two-stroke engines are widely used in snowmobiles, lawnmowers, weed-whackers, chain saws, jet skis, mopeds, outboard motors, and many motorcycles.

The largest compression-ignition engines are two-strokes and are used in some locomotives and large ships. These engines use forced induction to scavenge the cylinders. An example of this type of motor is the Wartsila-Sulzer turbocharged 2 stroke diesel as used in large container ships. It is the most efficient and powerful engine in the world, with over 50% thermal efficiency. For comparison, the most efficient small 4-stroke motors are around 43% thermal efficiency (SAE 900648), and size is an advantage for efficiency due to the increase in the ratio of volume to area.

[edit] Four-stroke

Main article: Four-stroke cycle

Engines based on the four-stroke or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger boats, some motorcycles, and many light aircraft. They are generally quieter, more efficient, and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the Atkinson and Miller cycles. Most truck and automotive diesel engines use a four-stroke cycle, but with a compression heating ignition system. This variation is called the diesel cycle. The steps involved here are:

1. Intake stroke: Air and vaporized fuel are drawn in.
2. Compression stroke: Fuel vapor and air are compressed and ignited.
3. Combustion stroke: Fuel combusts and piston is pushed downwards.
4. Exhaust stroke: Exhaust is driven out. During the 1st, 2nd, and 4th, stroke the piston is relying on power and momentum generated by the other pistons. In that case a four cylinder engine would be less powerful than a six or eight cylinder engine.

[edit] Five-stroke

Engines based on the five-stroke cycle are a variant of the four-stroke cycle. Normally the four cycles are intake, compression, combustion, and exhaust. The fifth cycle added by Delautour^[3] is refrigeration. Engines running on a five-stroke cycle are claimed to be up to 30 percent more efficient than equivalent four-stroke engines.

[edit] Six-stroke

The six stroke engine captures the wasted heat from the 4-stroke Otto cycle and creates steam, which simultaneously cools the engine while providing a free power stroke. This removes the need for a cooling system, making the engine lighter while giving 40% increased efficiency over the Otto Cycle.

Beare Head Technology combines a four-stroke engine bottom end with a ported cylinder, which closely resembles that of a two-stroke: thus, 4+2 = six-stroke. It has an opposing piston that acts in unison with auxiliary low pressure reed and rotary valves, allowing variable compression and a range of tuning options.

[edit] Bourke engine

Main article: Bourke engine

In this engine, two opposed cylinders are linked to the crank by a Scotch yoke. The Scotch yoke mechanism prevents side thrust, preventing any piston slap, allowing operation as a detonation or "explosion" engine. This also greatly reduces friction between pistons and cylinder walls. The Bourke engine uses fewer moving parts and has to overcome less friction than conventional crank and slider engines with poppet valves. However no independent testing of this engine has ever borne out any of these claims.

[edit] Controlled Combustion Engine

Main article: Controlled Combustion Engine

These are also cylinder-based engines, which may be one or two-stroke but use, instead of a crankshaft and piston rods, two gear-connected, counterrotating concentric cams to convert reciprocating motion into rotary movement. These cams practically cancel out sideward forces that would otherwise be exerted on the cylinders by the pistons, greatly improving mechanical efficiency. The number of lobes of the cams (always an odd number not less than 3) determines the piston travel versus the torque delivered. In this engine, there are two cylinders that are 180 degrees apart for each pair of counterrotating cams. For single-stroke versions, there are as many cycles per cylinder pair as there are lobes on each cam, and twice as many for two-stroke engines.

[edit] Wankel

Main article: Wankel engine

The Wankel engine (rotary engine) does not have piston strokes, so is more properly called a four-phase, rather than a four-stroke, engine. It operates with the same separation of phases as the four-stroke engine, with the phases taking place in separate locations in the engine. This engine provides three power 'strokes' per revolution per rotor (while it is true that 3 power strokes occur per ROTOR revolution, due to the 3/1 revolution ratio of the rotor to the eccentric shaft, only 1 power stroke per shaft revolution actually occurs), typically giving it a greater power-to-weight ratio than piston engines. This type of engine is most notably used in the current Mazda RX-8, the earlier RX-7, and other models.

[edit] Gas turbine

Main article: Gas turbine

Gas turbines cycles (notably jet engines) do not use the same system to both compress and then expand the gases; instead, separate compression and expansion turbines are employed, giving continuous power. Essentially, the intake gas (normally air) is compressed and then combusted with a fuel, which greatly raises the temperature and volume. The larger volume of hot gas from the combustion chamber is then fed through the gas turbine, which is then able to power the compressor. The exhaust gas may be used to provide thrust, supplying only sufficient power to the turbine to compress incoming air (jet engine); or as much energy as possible can be supplied to the shaft (gas turbine proper).

[edit] Disused methods

In some old noncompressing internal combustion engines: In the first part of the piston downstroke, a fuel/air mixture was sucked or blown in. In the rest of the piston downstroke, the inlet valve closed and the fuel/air mixture fired. In the piston upstroke, the exhaust valve was open. This was an attempt at imitating the way a piston steam engine works. Since the explosive mixture was not compressed, the heat and pressure generated by combustion was much less, causing lower overall efficiency.

[edit] Fuels and oxidizers

Nowadays, fuels used include:

• Petroleum:
  • Petroleum spirit (North American term: gasoline, British term: petrol)
  • Petroleum diesel.
  • Autogas (liquified petroleum gas).
  • Compressed natural gas.
  • Jet fuel (aviation fuel)
• Coal:
  • Most methanol is made from coal.
  • Gasoline-like fuels can be made from coal.
• Biofuels and vegoils:
  • Peanut oil and other vegoils.
  • Biofuels:
    • Biobutanol (replaces gasoline).
    • Biodiesel (replaces petrodiesel).
    • Bioethanol and Biomethanol (wood alcohol) and other biofuels (see Flexible-fuel vehicle).
    • Biogas
• Hydrogen

Even fluidized metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines, and those that use liquid hydrocarbons are called oil engines. However, gasoline engines are also often colloquially referred to as 'gas engines.'

The main limitations on fuels are that it must be easily transportable through the fuel system to the combustion chamber and that the fuel releases sufficient energy in the form of heat upon combustion to make use of the engine practical.

Diesel engines are generally heavier, noisier, and more powerful at lower speeds than gasoline engines. They are also more fuel-efficient in most circumstances, and are used in heavy road vehicles, some automobiles (increasingly so for their increased fuel efficiency over gasoline engines), ships, railway locomotives, and light aircraft. Gasoline engines are used in most other road vehicles, including most cars, motorcycles and

Ford
Type	Public (NYSE: F)
Founded	June 17, 1903
Founder	Henry Ford
Headquarters	Dearborn, Michigan, USA
Area served	worldwide
Key people	Henry Ford, Founder Alan Mulally, President and CEO William Clay Ford, Jr, Chairman
Industry	Automotive
Products	mainstream/performance vehicles, Automotive parts,
Services	Automotive financing and services
Revenue	▲ US$173.9 billion (2007)[1]
Operating income	▲ US$126 million (2007)[1]
Net income	▼ US$2.665 billion (2007)[1]
Employees	245,000 (2007)[1]
Divisions	Ford Credit Ford division Lincoln Mercury Premier Automotive Group
Subsidiaries	Automotive Components Holdings Volvo (cars only)
Website	www.ford.com

Ford Motor Company is an American multinational corporation and the world's third largest automaker based on worldwide vehicle sales. Based in Dearborn, Michigan, a suburb of Detroit, the automaker was founded by Henry Ford and incorporated on June 16, 1903. Ford's overseas business encompasses only one truly global brand (Volvo of Sweden) other than the Ford brand itself, but it also owns a one-third controlling interest in Mazda of Japan and a small holding in former subsidiary Aston Martin of England. Its former UK subsidiaries Jaguar and Land Rover were sold to Tata Motors of India in March 2008, both companies having been through many changes of ownership in the recent past. Lincoln and Mercury are also Ford's aspirational brands in the USA, but not in the rest of the world. Ford also sold the brand names of Daimler (excluding certain rights sold to Germany's Daimler AG), Lanchester, and Rover to Tata Motors of India.

In 2007, Ford became the third-ranked automaker in US sales after General Motors and Toyota, falling from the second-ranked automaker slot for the first time in the previous 56 years. Ford was also the overall seventh-ranked American-based company in the 2007 Fortune 500 list, based on global revenues in 2006 of $160.1 billion.^[2] In 2007, Ford revenues increased to $173.9 billion, while producing 6.553 million automobiles and employing about 245,000 employees at around 100 plants and facilities worldwide.^[1] Also in 2007, Ford received more initial quality survey awards from J. D. Power and Associates than any other automaker, with five vehicles ranking at the top of their categories,^[3] and fourteen vehicles ranked in the top three.^[4]

Ford introduced methods for large-scale manufacturing of cars and large-scale management of an industrial workforce, using elaborately engineered manufacturing sequences typified by moving assembly lines. Henry Ford's methods came to be known around the world as Fordism by 1914.

History

Henry Ford (ca. 1919)

1896 Ford Quadricycle

Main article: History of Ford Motor Company

Ford was launched in a converted factory in 1903 with $28,000 in cash from twelve investors, most notably John and Horace Dodge (who would later found the their own car company). During its early years, the company produced just a few cars a day at its factory on Mack Avenue in Detroit, Michigan. Groups of two or three men worked on each car from components made to order by other companies. Henry Ford was 40 years old when he founded the Ford Motor Company, which would go on to become one of the world's largest and most profitable companies, as well as being one to survive the Great Depression. As one of the largest family-controlled companies in the world, the Ford Motor Company has been in continuous family control for over 100 years.

Corporate governance

Ford World Headquarters in Dearborn, Michigan, known as the Glass House.

Members of the board as of early 2007 are: Chief Sir John Bond, Richard Manoogian, Stephen Butler, Ellen Marram, Kimberly Casiano, Alan Mulally (President and CEO), Edsel Ford II, Homer Neal, William Clay Ford Jr., Jorma Ollila, Irvine Hockaday Jr., John L. Thornton and William Clay Ford (Director Emeritus).^[5]

The main corporate officers are: Lewis Booth (Executive Vice President, Chairman (PAG) and Ford of Europe), Mark Fields (Executive Vice President, President of The Americas), Donat Leclair (Executive Vice President and CFO), Mark A. Schulz (Executive Vice President, President of International Operations) and Michael E. Bannister (Group Vice President; Chairman & CEO Ford Motor Credit).^[5] Paul Mascarenas (Vice President of Engineering, The Americas Product Development)

Recent company developments

During the mid to late 1990s, Ford sold large numbers of vehicles, in a booming American economy with soaring stock market and low fuel prices. With the dawn of the new century, legacy healthcare costs, higher fuel prices, and a faltering economy led to falling market shares, declining sales, and sliding profit margins. Most of the corporate profits came from financing consumer automobile loans through Ford Motor Credit Company.^[6]

By 2005, corporate bond rating agencies had downgraded the bonds of both Ford and GM to junk status ^[7], citing high U.S. health care costs for an aging workforce, soaring gasoline prices, eroding market share, and dependence on declining SUV sales for revenues. Profit margins decreased on large vehicles due to increased "incentives" (in the form of rebates or low interest financing) to offset declining demand. ^[8]

In the face of falling truck and SUV sales, Ford moved to introduce a range of new vehicles, including "Crossover SUVs" built on unibody car platforms, rather than body-on-frame truck chassis. Ford also developed alternative fuel and high efficiency vehicles, such as the Escape Hybrid.^[9]. Ford announced that it will team up with Southern California Edison (SCE) to examine the future of plug-in hybrids in terms of how home and vehicle energy systems will work with the electrical grid. Under the multi-million-dollar, multi-year project, Ford will convert a demonstration fleet of Ford Escape Hybrids into plug-in hybrids, and SCE will evaluate how the vehicles might interact with the home and the utility's electrical grid. Some of the vehicles will be evaluated "in typical customer settings," according to Ford. ^[10][11]

In December 2006, the company raised its borrowing capacity to about $25 billion, placing substantially all corporate assets as collateral to secure the line of credit ^[12]. Chairman Bill Ford has stated that "bankruptcy is not an option" ^[13]. In order to control its skyrocketing labor costs (the most expensive in the world), the company and the United Auto Workers, representing approximately 46,000 hourly workers in North America, agreed to a historic contract settlement in November of 2007 giving the company a substantial break in terms of its ongoing retiree health care costs and other economic issues. The agreement includes the establishment of a company-funded, independently-run Voluntary Employee Beneficiary Association (more commonly known as a VEBA) trust to shift the burden of retiree health care off of the company's books, thereby improving its balance sheet. However, this arrangement will not begin to take effect until January 1, 2010. The agreement also gives hourly workers the job security they were seeking by having the company commit to substantial investments in most of its factories.

The automaker reported the largest annual loss in company history in 2006 of $12.7 billion, ^[14] and estimated that it would not return to profitability until 2009.^[15] However, Ford surprised Wall Street in the second quarter of 2007 by posting a $750 million profit. Despite the gains, the company finished the year with a $2.7 billion loss, largely attributed to finance restructuring at Volvo.^[16]

In March 2008, Ford announced that it has reached agreement to sell its Jaguar and Land Rover operations to Tata Motors for $2.3 billion. The sale is expected to be completed by the end of the second quarter of 2008.^[17] It is understood that Ford Motor Company Ltd. will not retain any shareholding in either the Jaguar or Land-Rover companies, unlike Aston Martin where on its sale a small shareholding was retained; when the total sum to be paid in cash by Tata Motors of approximately US$2.3 billion, Ford will then contribute up to US $600 million to the Jaguar Land Rover pension plans.

In January of 2008, Ford launched a website listing the 10 Built Ford Tough Rules as well as a series of webisodes that parodies the show COPS (TV Series).

"The Way Forward"

Main article: The Way Forward

In the latter half of 2005, Chairman Bill Ford asked newly-appointed Ford Americas Division President Mark Fields to develop a plan to return the company to profitability. Fields previewed the Plan, dubbed The Way Forward, at the December 7, 2005 board meeting of the company; and it was unveiled to the public on January 23, 2006. "The Way Forward" includes resizing the company to match current market realities, dropping some unprofitable and inefficient models, consolidating production lines, and shutting fourteen factories and cutting 30,000 jobs. ^[18].

These cutbacks are consistent with Ford's roughly 25% decline in U.S. automotive market share since the mid-late 1990s. Ford's target is to become profitable again in 2009, a year later than projected. Ford's realignment also includes the sale of its wholly owned subsidiary, Hertz Rent-a-Car to a private equity group for $15 billion in cash and debt acquisition. The sale was completed on December 22, 2005. A joint venture with Mahindra and Mahindra Limited of India ended with the sale of Ford's 15 percent stake in 2005.

Chairman and Chief Executive Officer Ford also became President of the company in April 2006, with the retirement of Jim Padilla. Five months later, in September, he stepped down as President and CEO, and naming Alan Mulally as his successor. Bill Ford continues as Executive Chairman, along with an executive operating committee made up of Mulally, Mark Schulz, Lewis Booth, Don Leclair, and Mark Fields.

Online

The domain ford.com attracted at least 11 million visitors annually by 2008 according to a Compete.com survey.

Brands and marques

Today, Ford Motor Company manufactures automobiles under several names including Lincoln and Mercury in the United States. In 1958, Ford introduced a new marque, the Edsel, but poor sales led to its discontinuation in 1960. Later, in 1985, the Merkur brand was introduced to market Fords from Europe in the United States; it met a similar fate in 1989.

Ford has major manufacturing operations in Canada, Mexico, the United Kingdom, Germany, Turkey, Brazil, Argentina, Australia, the People's Republic of China, and several other countries, including South Africa where, following divestment during apartheid, it once again has a wholly owned subsidiary. Ford also has a cooperative agreement with Russian automaker GAZ.

Since 1989, Ford has acquired Aston Martin (which it sold again on March 12, 2007^[19], but it will retain a $77 million stake in the sports car maker^[20]), and Volvo Cars from Sweden, as well as a controlling share (33.4%) of Mazda of Japan, with which it operates an American joint venture plant in Flat Rock, Michigan called Auto Alliance. It has spun off its parts division under the name Visteon.

Ford's FoMoCo parts division sells aftermarket parts under the Motorcraft brand name.

Ford's non-manufacturing operations include organizations such as automotive finance operation Ford Motor Credit Company. Ford also sponsors numerous events and sports facilities around the nation, most notably Ford Center in downtown Oklahoma City and Ford Field in downtown Detroit.

Overall the Ford Motor Company controls the following operational car marques: Ford, Lincoln, Mazda, Mercury, and Volvo.

Global markets

Initially, Ford models sold outside the U.S. were essentially versions of those sold on the home market, but later on, models specific to Europe were developed and sold. Attempts to globalize the model line have often failed, with Europe's Ford Mondeo selling poorly in the United States, while U.S. models such as the Ford Taurus have fared poorly in Japan and Australia, even when produced in right hand drive. The small European model Ka, a hit in its home market, did not catch on in Japan, as it was not available as an automatic. The Mondeo was dropped by Ford Australia, because the segment of the market in which it competes had been in steady decline, with buyers preferring the larger local model, the Falcon. One recent exception is the European model of the Focus, which has sold strongly on both sides of the Atlantic.

From 2003, Toyota outsold Ford Motor worldwide.^[21] From the second quarter 2006, Toyota has passed Ford as the #2 automaker, by sales, in the United States.^[22]

The Ford Motor Company is in partnership talks to license hybrid technology from the Toyota Motor Corporation in a deal that could help establish Toyota's system as a standard for the industry.^[23]

Europe

At first, Ford in Germany and the United Kingdom built different models from one another until the late 1960s, with the Ford Escort and then the Ford Capri being common to both companies. Later on, the Ford Taunus and Ford Cortina became identical, produced in left hand drive and right hand drive respectively. Rationalization of model ranges meant that production of many models in the UK switched to elsewhere in Europe, including Belgium and Spain as well as Germany. The Ford Sierra replaced the Taunus and Cortina in 1982, drawing criticism for its radical aerodynamic styling, which was soon given nicknames such as "Jellymould" and "The Salesman's Spaceship."

Increasingly, Ford Motor Company has looked to Ford of Europe for its "world cars," such as the Mondeo, Focus, and Fiesta, although sales of European-sourced Fords in the U.S. have been disappointing. In Asia, models from Europe are not as competitively priced as Japanese-built rivals, nor are they perceived as reliable. The Focus has been one exception to this, which has become America's best selling compact car since its launch in 2000.^{[citation needed]}

In February 2002, Ford ended car production in the UK. It was the first time in 90 years that Ford cars had not been made in Britain, although production of the Transit van continues at the company's Southampton facility, engines at Bridgend and Dagenham, and transmissions at Halewood. Development of European Ford is broadly split between Dunton in Essex (powertrain, Fiesta/Ka, and commercial vehicles) and Cologne (body, chassis, electrical, Focus, Mondeo) in Germany. Ford also produced the Thames range of commercial vehicles, although the use of this brand name was discontinued circa 1965. Elsewhere in continental Europe, Ford assembles the Mondeo range in Genk (Belgium), Fiesta in Valencia (Spain) and Cologne (Germany), Ka in Valencia, and Focus in Valencia, Saarlouis (Germany) and Vsevolozhsk (Russia). Transit production is in Kocaeli (Turkey), Southampton (UK), and Transit Connect in Kocaeli.

Ford also owns a joint-venture production plant in Turkey. Ford-Otosan, established in the 1970s, manufactures the Transit Connect compact panel van as well as the "Jumbo" and long wheelbase versions of the full-size Transit. This new production facility was set up near Kocaeli in 2002, and its opening marked the end of Transit assembly in Genk.

Another joint venture plant near Setubal in Portugal, set up in collaboration with Volkswagen, formerly assembled the Galaxy people-carrier as well as its sister ships, the VW Sharan and Seat Alhambra. With the introduction of the third generation of the Galaxy, Ford has moved the production of the people-carrier to the Genk plant, with Volkswagen taking over sole ownership of the Setubal facility.

Ford Europe has broken new ground with a number of relatively futuristic car launches over the last 50 years.

Its 1959 Anglia two-door saloon was one of the most quirky-looking small family cars in Europe at the time of its launch, but buyers soon became accustomed to its looks and it was hugely popular with British buyers in particular. It was still selling well when replaced by the more practical Escort in 1967.

The third incarnation of the Ford Escort was launched in 1980 and marked the company's move from rear-wheel drive saloons to front-wheel drive hatchbacks in the small family car sector. It also offered levels of style, comfort and refinement which were almost unmatched on comparable cars of this era. It was a huge success all over Europe and it was Britain's most popular car for most of its 10-year production life.^{[citation needed]}

The fourth generation Escort was produced from 1990 until 2000, although its successor - the Focus - had been on sale since 1998. On its launch, the Focus was arguably the most dramatic-looking and fine-handling small family cars on sale, and sold in huge volumes right up to the launch of the next generation Focus at the end of 2004.

The 1982 Ford Sierra - replacement for the long-running and massively popular Cortina and Taunus models - was a style-setter at the time of its launch. Its ultramodern aerodynamic design was a world away from a boxy, sharp-edged Cortina, and it was massively popular just about everywhere it was sold. A series of updates kept it looking relatively fresh until it was replaced by the front-wheel drive Mondeo at the start of 1993.

The first two incarnations of the Mondeo were well-built, refined and reliable family cars that attracted strong sales, but the third incarnation (launched in 2007) took the large family car market to new heights in terms of build quality, refinement, comfort, equipment, driver appeal and value for money.^{[citation needed]}

The rise in popularity of small cars during the 1970s saw Ford enter the mini-car market in 1976 with its Fiesta hatchback. Most of its production was concentrated at Valencia in Spain, and the Fiesta sold in huge figures from the very start. An update in 1983 and the launch of an all-new model in 1989 strengthened its position in the small car market. The second generation Fiesta was significantly updated twice before an all-new model was launched in 2002, and over the years it has become more refined, spacious, better-built and more enjoyable to drive.^{[citation needed]}

Asia Pacific

Ford dealership in Ho Chi Minh City, Vietnam (August 2005)

In New Zealand and Australia, the popular Ford Falcon was long considered the average family car and is considerably larger than the Mondeo, Ford's largest car sold in Europe. Between 1960 and 1972, the Falcon was based on a U.S. Ford of that name, but since then has been entirely designed and manufactured locally. Like its General Motors rival, the Holden Commodore, the 4.0 L Falcon retains rear wheel drive. High performance variants of the Falcon running locally-built engines produce up to 365 hp (272 kW). A ute (short for "utility," known in the US as pickup truck) version is also available with a similar range of drivetrains. In addition, Ford Australia sells highly-tuned Falcon sedans and utes through its performance car division, Ford Performance Vehicles. These cars produce 390 hp (291 kW) and are built in small numbers to increase their value as collectors' cars.

In Australia, the Commodore and Falcon have traditionally outsold all other cars and comprise over 20% of the new car market. In New Zealand, Ford was second in market share in the first eight months of 2006 with 14.4 per cent.^[24] This is all set to change with a shift away from local manufacturing and assembly: 2007 second quarter has seen Ford Australia cut their prestige (LWB) models and more recently, announced closure of their key engine manufacturing. This is due partly to drops in sales with stiff competition from Toyota's new Aurion and an updated Mitsubishi 380, both taking a large piece of the local family sedan market. Ford is betting on growth in small car sales with the Focus which it plans to assemble locally, and the popular Territory (Falcon-based) SUV.

Ford's presence in Asia has traditionally been much smaller. However, with the acquisition of a stake in Japanese manufacturer Mazda in 1979, Ford began selling Mazda's Familia and Capella (also known as the 323 and 626) as the Ford Laser and Telstar. The Laser was one of the most successful models sold by Ford in Australia, and outsold the Mazda 323, despite being almost identical to it. The Laser was also built in Mexico and sold in the U.S. as the Mercury Tracer, while the 1991 (and on through the end of the model in the early 2000s) American Ford Escort (and 1991-on Tracer) was based on the Laser/Mazda 323, assembled in the US and Mexico.

Through its relationship with Mazda, Ford also acquired a stake in South Korean manufacturer Kia, which built the (Mazda-based) Ford Festiva from 1988-1993, and the Ford Aspire from 1994-1997 for export to the United States, but later sold their interest to Hyundai. Kia continued to market the Aspire as the Kia Avella, later replaced by the Rio and once again sold in the US. Ironically, Hyundai also manufactured the Ford Cortina until the 1980s. Ford also has a joint venture with Lio Ho in Taiwan, which assembled Ford models locally since the 1970s.

Ford came to India in 1998 with its Ford Escort model, which was later replaced by locally produced Ford Ikon in 2001. It has since added Fusion, Fiesta, Mondeo and Endeavour to its product line.

South America

In South America, Ford has had to face protectionist government measures in each country, with the result that it built different models in different countries, without particular regard to rationalization or economy of scale inherent to producing and sharing similar vehicles between the nations. In many cases, new vehicles in a country were based on those of the other manufacturers it had entered into production agreements with, or whose factories it had acquired. For example, the Corcel and Del Rey in Brazil were originally based on Renault vehicles.

In 1987, Ford merged its operations in Brazil and Argentina with those of Volkswagen to form a company called Autolatina, with which it shared models. Sales figures and profitability were disappointing, and Autolatina was dissolved in 1995. With the advent of Mercosur, the regional common market, Ford was finally able to rationalize its product line-ups in those countries. Consequently, the Ford Fiesta and Ford EcoSport are only built in Brazil, and the Ford Focus only built in Argentina, with each plant exporting in large volumes to the neighboring countries. Models like the Ford Mondeo from Europe could now be imported completely built up. Ford of Brazil produces a pick-up truck version of the Fiesta, the Courier, which is also produced in South Africa as the Ford Bantam in right hand drive versions.

Africa and Middle East

In Africa Ford's market presence has traditionally been strongest in South Africa and neighboring countries, with only trucks being sold elsewhere on the continent. Ford in South Africa began by importing kits from Canada to be assembled at its Port Elizabeth facility. Later Ford sourced its models from the UK and Australia, with local versions of the Ford Cortina including the XR6, with a 3.0 V6 engine, and a Cortina 'bakkie' or pick-up, which was exported to the UK. In the mid-1980s Ford merged with a rival company, owned by Anglo American, to form the South African Motor Corporation (Samcor).

Following international condemnation of apartheid, Ford divested from South Africa in 1988, and sold its stake in Samcor, although it licensed the use of its brand name to the company. Samcor began to assemble Mazdas as well, which affected its product line-up, which saw the European Fords like the Escort and Sierra replaced by the Mazda-based Laser and Telstar. Ford bought a 45 per cent stake in Samcor following the demise of apartheid in 1994, and this later became, once again, a wholly owned subsidiary, the Ford Motor Company of Southern Africa. Ford now sells a local sedan version of the Fiesta (also built in India and Mexico), and the Focus and Mondeo Europe. The Falcon model from Australia was also sold in South Africa, but was dropped in 2003.

Ford's market presence in the Middle East has traditionally been even smaller, partly due to previous Arab boycotts of companies dealing with Israel. Ford and Lincoln vehicles are currently marketed in ten countries in the region.^[25] Saudi Arabia, Kuwait, and the UAE are the biggest markets. Ford also established itself in Egypt in 1926, but faced an uphill battle during the 1950s due to the hostile nationalist business environment ^[26]. Ford's distributor in Saudi Arabia announced in February 2003 that it had sold 100,000 Ford and Lincoln vehicles since commencing sales in November 1986. Half of the Ford/Lincoln vehicles sold in that country were Ford Crown Victorias.^[27] In 2004, Ford sold 30,000 units in the region, falling far short of General Motors' 88,852 units and Nissan Motors' 75,000 units.

Environmental Record

Record of Ford's environmental decisions

Ford has a mixed record on environmental issues, consisting of both positive and negative reports. In 2003, Ford discarded its goal of improving mileage on sport-utility vehicles by 25 percent by 2005, considering that it would boost mileage of all vehicles instead. However, this plan had neither specific target nor goal. ^[28]

William Clay Ford Jr., the chairman and chief executive of the Ford Motor Co., commented in 2002 that a credibility gap on environmental issues has eroded America's love for cars. "During the nearly 25 years I've worked in the industry, the love affair that people have had with automobiles has in some ways grown stale, and some would say it's even dying," Ford said. "If you remember, in California, people used to write songs about T-Birds and Corvettes. Today, they write regulations. " ^[29]

For the 2007 model year, Ford has 13 U.S. models that achieve 30 miles per gallon or better (based on the highway fuel economy estimates of the U.S. Environmental Protection Agency (EPA)) and several of Ford’s vehicles were recognized in the EPA and Department of Energy Fuel Economy Guide for best-in-class fuel economy.Also, Ford has eliminated nearly 3 million pounds of smog-forming emissions from our U.S. cars and light trucks over the 2004 to 2006 model years.^[30]

Alternative fuel vehicles and hybrids

Mulally (second from left) with President

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. ^[1] The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty. A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they simply call "vacuum" or "free space" in this context, and use the term partial vacuum to refer to real vacuum. The Latin term in vacuo is also used to describe an object as being in what would otherwise be a vacuum.

The quality of a vacuum refers to how closely it approaches a perfect vacuum. The residual gas pressure is the primary indicator of quality, and is most commonly measured in units called torr, even in metric contexts. Lower pressures indicate higher quality, although other variables must also be taken into account. Quantum theory sets limits for the best possible quality of vacuum, predicting that no volume of space can be perfectly empty. Outer space is a natural high quality vacuum, mostly of much higher quality than can be created artificially with current technology. Low quality artificial vacuums have been used for suction for millennia.

Vacuum has been a frequent topic of philosophical debate since Ancient Greek times, but was not studied empirically until the 17th century. Evangelista Torricelli produced the first laboratory vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. Vacuum became a valuable industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes, and a wide array of vacuum technology has since become available. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general.

A large vacuum chamber

[edit] Uses

Light bulbs contain a partial vacuum, usually backfilled with argon, which protects the tungsten filament

Vacuum is useful in a variety of processes and devices. Its first widespread use was in the incandescent light bulb to protect the filament from chemical degradation. Its chemical inertness is also useful for electron beam welding, cold welding, vacuum packing and vacuum frying. Ultra-high vacuum is used in the study of atomically clean substrates, as only a very good vacuum preserves atomic-scale clean surfaces for a reasonably long time (on the order of minutes to days). High to ultra-high vacuum removes the obstruction of air, allowing particle beams to deposit or remove materials without contamination. This is the principle behind chemical vapor deposition, physical vapor deposition, and dry etching which are essential to the fabrication of semiconductors and optical coatings, and to surface science. The reduction of convection provides the thermal insulation of thermos bottles. Deep vacuum promotes outgassing which is used in freeze drying, adhesive preparation, distillation, metallurgy, and process purging. The electrical properties of vacuum make electron microscopes and vacuum tubes possible, including cathode ray tubes. The elimination of air friction is useful for flywheel energy storage and ultracentrifuges.

Vacuums are commonly used to produce suction, which has an even wider variety of applications. The Newcomen steam engine used vacuum instead of pressure to drive a piston. In the 19th century, vacuum was used for traction on Isambard Kingdom Brunel's experimental atmospheric railway.

[edit] Outer space

Main article: Outer space

Outer space is not a perfect vacuum, but a tenuous plasma awash with charged particles, electromagnetic fields, and the occasional star.

Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. It has effectively no friction, allowing stars, planets and moons to move freely along ideal gravitational trajectories. But no vacuum is truly perfect, not even in interstellar space where there are still a few hydrogen atoms per cubic centimeter. The deep vacuum of space could make it an attractive environment for certain industrial processes, for instance those that require ultraclean surfaces; however, it is much less costly to create an equivalent vacuum on Earth than to leave the Earth's gravity well.

Stars, planets and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 1 Pa (10^-3 Torr) at 100 km of altitude, the Kármán line which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the sun and the dynamic pressure of the solar wind, so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre.

But although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region called low earth orbit and must fire their engines every few days to maintain orbit. The drag here is low enough that it could theoretically be overcome by radiation pressure on solar sails, a proposed propulsion system for interplanetary travel. Planets are too massive for their trajectories to be affected by these forces, although their atmospheres are eroded by the solar winds.

All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos. The current temperature of this radiation is about 3 K, or -270 degrees Celsius or -454 degrees Fahrenheit.

[edit] Effects on humans and animals

See also: Human adaptation to space

This painting, An Experiment on a Bird in the Air Pump by Joseph Wright of Derby, 1768, depicts an experiment performed by Robert Boyle in 1660.

Humans and animals exposed to vacuum will lose consciousness after a few seconds and die of hypoxia within minutes, but the symptoms are not nearly as graphic as commonly shown in pop culture. Blood and other body fluids do boil when their pressure drops below 6.3 kPa, (47 Torr,) the vapour pressure of water at body temperature.^[2] This condition is called ebullism. The steam may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture. Ebullism is slowed by the pressure containment of blood vessels, so some blood remains liquid.^[3][4] Swelling and ebullism can be restrained by containment in a flight suit. Shuttle astronauts wear a fitted elastic garment called the Crew Altitude Protection Suit (CAPS) which prevents ebullism at pressures as low as 2 kPa (15 Torr).^[5] Rapid evaporative cooling of the skin will create frost, particularly in the mouth, but this is not a significant hazard.

Animal experiments show that rapid and complete recovery is the norm for exposures shorter than 90 seconds, while longer full-body exposures are fatal and resuscitation has never been successful.^[6] There is only a limited amount of data available from human accidents, but it is consistent with animal data. Limbs may be exposed for much longer if breathing is not impaired.^[2] Robert Boyle was the first to show in 1660 that vacuum is lethal to small animals. In 1942, in one of a series of experiments on human subjects for the Luftwaffe, the Nazi regime tortured Dachau concentration camp prisoners by exposing them to vacuum in order to determine the human body's capacity to survive high-altitude conditions.

Cold or oxygen-rich atmospheres can sustain life at pressures much lower than atmospheric, as long as the density of oxygen is similar to that of standard sea-level atmosphere. The colder air temperatures found at altitudes of up to 3 km generally compensate for the lower pressures there.^[2] Above this altitude, oxygen enrichment is necessary to prevent altitude sickness, and spacesuits are necessary to prevent ebullism above 19 km.^[2] Most spacesuits use only 20 kPa (150 Torr) of pure oxygen, just enough to sustain full consciousness. This pressure is high enough to prevent ebullism, but simple evaporation of blood can still cause decompression sickness and gas embolisms if not managed.

Rapid decompression can be much more dangerous than vacuum exposure itself. Even if the victim does not hold his breath, venting through the windpipe may be too slow to prevent the fatal rupture of the delicate alveoli of the lungs.^[2] Eardrums and sinuses may be ruptured by rapid decompression, soft tissues may bruise and seep blood, and the stress of shock will accelerate oxygen consumption leading to hypoxia.^[7] Injuries caused by rapid decompression are called barotrauma. A pressure drop as small as 100 Torr, (13 kPa,) which produces no symptoms if it is gradual, may be fatal if occurs suddenly.^[2]

Some extremophile microrganisms, such as Tardigrades, can survive vacuum for a period of years.

[edit] Historical interpretation

Historically, there has been much dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers did not like to admit the existence of a vacuum, asking themselves "how can 'nothing' be something?". Plato found the idea of a vacuum inconceivable. He believed that all physical things were instantiations of an abstract Platonic ideal, and he could not conceive of an "ideal" form of a vacuum. Similarly, Aristotle considered the creation of a vacuum impossible — nothing could not be something. Later Greek philosophers thought that a vacuum could exist outside the cosmos, but not within it.

Hero of Alexandria was the first to challenge this belief in the first century AD, but his attempts to create an artificial vacuum failed.^[8] The philosopher Al-Farabi (872 - 950 CE) appears to have carried out the first experiments concerning the existence of vacuum, in which he investigated handheld plungers in water.^[9] He concluded that air's volume can expand to fill available space, and he suggested that the concept of perfect vacuum was incoherent.^[10]

Torricelli's mercury barometer produced one of the first sustained vacuums in a laboratory.

In the Middle Ages, the Catholic Church held the idea of a vacuum to be immoral or even heretical. The absence of anything implied the absence of God, and harkened back to the void prior to the creation story in the book of Genesis. Medieval thought experiments into the idea of a vacuum considered whether a vacuum was present, if only for an instant, between two flat plates when they were rapidly separated. There was much discussion of whether the air moved in quickly enough as the plates were separated, or, as Walter Burley postulated, whether a 'celestial agent' prevented the vacuum arising. The commonly held view that nature abhorred a vacuum was called horror vacui. This speculation was shut down by the 1277 Paris condemnations of Bishop Etienne Tempier, which required there to be no restrictions on the powers of God, which led to the conclusion that God could create a vacuum if he so wished.^[11] In spite of this, opposition to the idea of a vacuum existing in nature continued into the Scientific Revolution, with scholars such as Paolo Casati taking an anti-vacuist position. Jean Buridan reported in the 14th century that teams of ten horses could not pull open bellows when the port was sealed, apparently because of horror vacui.^[8]

The Crookes tube, used to discover and study cathode rays, was an evolution of the Geissler tube.

The belief in horror vacui was overthrown in the 17th century. Water pump designs had improved by then to the point that they produced measurable vacuums, but this was not immediately understood. What was known was that suction pumps could not pull water beyond a certain height: 18 Florentine yards according to a measurement taken around 1635. (The conversion to metres is uncertain, but it would be about 9 or 10 metres.) This limit was a concern to irrigation projects, mine drainage, and decorative water fountains planned by the Duke of Tuscany, so the Duke commissioned Galileo to investigate the problem. Galileo advertised the puzzle to other scientists, including Gaspar Berti who replicated it by building the first water barometer in Rome in 1639.^[12] Berti's barometer produced a vacuum above the water column, but he could not explain it. The breakthrough was made by Evangelista Torricelli in 1643. Building upon Galileo's notes, he built the first mercury barometer and wrote a convincing argument that the space at the top was a vacuum. The height of the column was then limited to the maximum weight that atmospheric pressure could support. Some people believe that although Torricelli's experiment was crucial, it was Blaise Pascal's experiments that proved the top space really contained vacuum.

In 1654, Otto von Guericke invented the first vacuum pump and conducted his famous Magdeburg hemispheres experiment, showing that teams of horses could not separate two hemispheres from which the air had been evacuated. Robert Boyle improved Guericke's design and conducted experiments on the properties of vacuum. Robert Hooke also helped Boyle produce an air pump which helped to produce the vacuum. The study of vacuum then lapsed until 1855, when Heinrich Geissler invented the mercury displacement pump and achieved a record vacuum of about 10 Pa (0.1 Torr). A number of electrical properties become observable at this vacuum level, and this renewed interest in vacuum. This, in turn, led to the development of the vacuum tube.

While outer space has been likened to a vacuum, early theories of the nature of light relied upon the existence of an invisible, aetherial medium which would convey waves of light (Isaac Newton relied on this idea to explain refraction and radiated heat).^[13] This evolved into the luminiferous aether of the 19th century, but the idea was known to have significant shortcomings - specifically that if the Earth were moving through a material medium, the medium would have to be both extremely tenuous (because the Earth is not detectably slowed in its orbit), and extremely rigid (because vibrations propagate so rapidly). An 1891 article by William Crookes noted: "the [freeing of] occluded gases into the vacuum of space".^[14] Even up until 1912, astronomer Henry Pickering commented: "While the interstellar absorbing medium may be simply the ether, [it] is characteristic of a gas, and free gaseous molecules are certainly there".^[15]

In 1887, the Michelson-Morley experiment, using an interferometer to attempt to detect the change in the speed of light caused by the Earth moving with respect to the aether, was a famous null result, showing that there really was no static, pervasive medium throughout space and through which the Earth moved as though through a wind. While there is therefore no aether, and no such entity is required for the propagation of light, space between the stars is not completely empty. Besides the various particles which comprise cosmic radiation, there is a cosmic background of photonic radiation (light), including the thermal background at about 2.7 K, seen as a relic of the Big Bang. None of these findings affect the outcome of the Michelson-Morley experiment to any significant degree.

Einstein argued that physical objects are not located in space, but rather have a spatial extent. Seen this way, the concept of empty space loses its meaning.^[16] Rather, space is an abstraction, based on the relationships between local objects. Nevertheless, the general theory of relativity admits a pervasive gravitational field, which, in Einstein's words^[17], may be regarded as an "aether", with properties varying from one location to another. One must take care, though, to not ascribe to it material properties such as velocity and so on.

In 1930, Paul Dirac proposed a model of vacuum as an infinite sea of particles possessing negative energy, called the Dirac sea. This theory helped refine the predictions of his earlier formulated Dirac equation, and successfully predicted the existence of the positron, discovered two years later in 1932. Despite this early success, the idea was soon abandoned in favour of the more elegant quantum field theory.

The development of quantum mechanics has complicated the modern interpretation of vacuum by requiring indeterminacy. Niels Bohr and Werner Heisenberg's uncertainty principle and Copenhagen interpretation, formulated in 1927, predict a fundamental uncertainty in the instantaneous measurability of the position and momentum of any particle, and which, not unlike the gravitational field, questions the emptiness of space between particles. In the late 20th century, this principle was understood to also predict a fundamental uncertainty in the number of particles in a region of space, leading to predictions of virtual particles arising spontaneously out of the void. In other words, there is a lower bound on the vacuum, dictated by the lowest possible energy state of the quantized fields in any region of space.

[edit] Quantum-mechanical definition

For more details on this topic, see vacuum state.

In quantum mechanics, the vacuum is defined as the state (i.e. solution to the equations of the theory) with the lowest energy. To first approximation, this is simply a state with no particles, hence the name.

Even an ideal vacuum, thought of as the complete absence of anything, will not in practice remain empty. Consider a vacuum chamber that has been completely evacuated, so that the (classical) particle concentration is zero. The walls of the chamber will emit light in the form of black body radiation. This light carries momentum, so the vacuum does have a radiation pressure. This limitation applies even to the vacuum of interstellar space. Even if a region of space contains no particles, the Cosmic Microwave Background fills the entire universe with black body radiation.

An ideal vacuum cannot exist even inside of a molecule. Each atom in the molecule exists as a probability function of space, which has a certain non-zero value everywhere in a given volume. Thus, even "between" the atoms there is a certain probability of finding a particle, so the space cannot be said to be a vacuum.

More fundamentally, quantum mechanics predicts that vacuum energy will be different from its naive, classical value. The quantum correction to the energy is called the zero-point energy and consists of energies of virtual particles that have a brief existence. This is called vacuum fluctuation. Vacuum fluctuations may also be related to the so-called cosmological constant in cosmology. The best evidence for vacuum fluctuations is the Casimir effect and the Lamb shift.^[11]

In quantum field theory and string theory, the term "vacuum" is used to represent the ground state in the Hilbert space, that is, the state with the lowest possible energy. In free (non-interacting) quantum field theories, this state is analogous to the ground state of a quantum harmonic oscillator. If the theory is obtained by quantization of a classical theory, each stationary point of the energy in the configuration space gives rise to a single vacuum. String theory is believed to have a huge number of vacua - the so-called string theory landscape.

[edit] Pumping

The manual water pump draws water up from a well by creating a vacuum that water rushes in to fill. In a sense, it acts to evacuate the well, although the high leakage rate of dirt prevents a high quality vacuum from being maintained for any length of time.

Main article: Vacuum pump

Fluids cannot be pulled, so it is technically impossible to create a vacuum by suction. Suction can spread and dilute a vacuum by letting a higher pressure push fluids into it, but the vacuum has to be created first before suction can occur. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes the volume of the lungs to increase. This expansion reduces the pressure and creates a partial vacuum, which is soon filled by air pushed in by atmospheric pressure.

To continue evacuating a chamber indefinitely without requiring infinite growth, a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded again. This is the principle behind positive displacement pumps, like the manual water pump for example. Inside the pump, a mechanism expands a small sealed cavity to create a vacuum. Because of the pressure differential, some fluid from the chamber (or the well, in our example) is pushed into the pump's small cavity. The pump's cavity is then sealed from the chamber, opened to the atmosphere, and squeezed back to a minute size.

A cutaway view of a turbomolecular pump, a momentum transfer pump used to achieve high vacuum

The above explanation is merely a simple introduction to vacuum pumping, and is not representative of the entire range of pumps in use. Many variations of the positive displacement pump have been developed, and many other pump designs rely on fundamentally different principles. Momentum transfer pumps, which bear some similarities to dynamic pumps used at higher pressures, can achieve much higher quality vacuums than positive displacement pumps. Entrapment pumps can capture gases in a solid or absorbed state, often with no moving parts, no seals and no vibration. None of these pumps are universal; each type has important performance limitations. They all share a difficulty in pumping low molecular weight gases, especially hydrogen, helium, and neon.

The lowest pressure that can be attained in a system is also dependent on many things other than the nature of the pumps. Multiple pumps may be connected in series, called stages, to achieve higher vacuums. The choice of seals, chamber geometry, materials, and pump-down procedures will all have an impact. Collectively, these are called vacuum technique. And sometimes, the final pressure is not the only relevant characteristic. Pumping systems differ in oil contamination, vibration, preferential pumping of certain gases, pump-down speeds, intermittent duty cycle, reliability, or tolerance to high leakage rates.

In ultra high vacuum systems, some very odd leakage paths and outgassing sources must be considered. The water absorption of aluminium and palladium becomes an unacceptable source of outgassing, and even the adsorptivity of hard metals such as stainless steel or titanium must be considered. Some oils and greases will boil off in extreme vacuums. The permeability of the metallic chamber walls may have to be considered, and the grain direction of the metallic flanges should be parallel to the flange face.

The lowest pressures currently achievable in laboratory are about 10^-13 Torr.^[18] However, pressures as low as 5×10^-17 Torr have been indirectly measured in a 4 K cryogenic vacuum system.^[19]

[edit] Outgassing

Main article: Outgassing

Evaporation and sublimation into a vacuum is called outgassing. All materials, solid or liquid, have a small vapour pressure, and their outgassing becomes important when the vacuum pressure falls below this vapour pressure. In man-made systems, outgassing has the same effect as a leak and can limit the achievable vacuum. Outgassing products may condense on nearby colder surfaces, which can be troublesome if they obscure optical instruments or react with other materials. This is of great concern to space missions, where an obscured telescope or solar cell can ruin an expensive mission.

The most prevalent outgassing product in man-made vacuum systems is water absorbed by chamber materials. It can be reduced by desiccating or baking the chamber, and removing absorbent materials. Outgassed water can condense in the oil of rotary vane pumps and reduce their net speed drastically if gas ballasting is not used. High vacuum systems must be clean and free of organic matter to minimize outgassing.

Ultra-high vacuum systems are usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials and boil them off. Once the bulk of the outgassing materials are boiled off and evacuated, the system may be cooled to lower vapour pressures and minimize residual outgassing during actual operation. Some systems are cooled well below room temperature by liquid nitrogen to shut down residual outgassing and simultaneously cryopump the system.

[edit] Quality

The quality of a vacuum is indicated by the amount of matter remaining in the system, so that a high quality vacuum is one with very little matter left in it. Vacuum is primarily measured by its absolute pressure, but a complete characterization requires further parameters, such as temperature and chemical composition. One of the most important parameters is the mean free path (MFP) of residual gases, which indicates the average distance that molecules will travel between collisions with each other. As the gas density decreases, the MFP increases, and when the MFP is longer than the chamber, pump, spacecraft, or other objects present, the continuum assumptions of fluid mechanics do not apply. This vacuum state is called high vacuum, and the study of fluid flows in this regime is called particle gas dynamics. The MFP of air at atmospheric pressure is very short, 70 nm, but at 100 mPa (~1×10^-3 Torr) the MFP of room temperature air is roughly 100 mm, which is on the order of everyday objects such as vacuum tubes. The Crookes radiometer turns when the MFP is larger than the size of the vanes.

Vacuum quality is subdivided into ranges according to the technology required to achieve it or measure it. These ranges do not have universally agreed definitions, but a typical distribution is as follows:^[20][21]

• Atmospheric pressure is variable but standardized at 101.325 kPa (760 Torr)
• Low vacuum, also called rough vacuum or coarse vacuum, is vacuum that can be achieved or measured with rudimentary equipment such as a vacuum cleaner and a liquid column manometer.
• Medium vacuum is vacuum that can be achieved with a single pump, but is too low to measure with a liquid or mechanical manometer. It can be measured with a McLeod gauge, thermal gauge or a capacitive gauge.
• High vacuum is vacuum where the MFP of residual gases is longer than the size of the chamber or of the object under test. High vacuum usually requires multi-stage pumping and ion gauge measurement. Some texts differentiate between high vacuum and very high vacuum.
• Ultra high vacuum requires baking the chamber to remove trace gases, and other special procedures. British and German standards define ultra high vacuum as pressures below 10^-6 Pa (10^-8 Torr).^[22][23]
• Deep space is generally much more empty than any artificial vacuum that we can create. It may or may not meet the definition of high vacuum above, depending on what region of space and astronomical bodies are being considered. For example, the MFP of interplanetary space is smaller than the size of the solar system, but larger than small planets and moons. As a result, solar winds exhibit continuum flow on the scale of the solar system, but must be considered as a bombardment of particles with respect to the Earth and Moon.
• Perfect vacuum is an ideal state that cannot be obtained in a laboratory, nor can it be found in outer space.

[edit] Examples

外太空堪稱最接近真空的空間

外太空並非完全真空的空間

「真空」是一種不存在任何物質的空間狀態，是一種物理現象。在「真空」中，聲音因為沒有介質而無法傳遞，但電磁波的傳遞卻不受真空的影響。事實上，在真空技術裡，真空係針對大氣而言，一特定空間內部之部份物質被排出，使其壓力小於一大氣壓，則我們通稱此空間為真空或真空狀態。真空常用帕斯卡（pascal）或托爾（Torr）做為壓力的單位。目前在自然環境裡，只有外太空堪稱最接近真空的空間。現代許多高精密度的產品在製造過程中的某些階段必需使用程度不一的真空才能製造，如半導體、硬碟機、鏡片。在實驗室和工廠中製造真空的方法是利用泵在密閉的空間中抽出空氣以達到某種程度的真空。在真空技術中按照壓力的高低我們可以區分為：

1. 粗略真空 (Rough Vacuum) 760 ~ 1 Torr
2. 中度真空 (Medium Vacuum) 1 ~ 10^-3 Torr
3. 高真空 (High Vacuum) 10^-3 ~ 10^-7 Torr
4. 超高真空 (Ultra-High Vacuum) 10^-7 Torr以下

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豊富なパリエーションを満足させ、特にハイテク品質要求にサポート致します。

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（６）ダイヤモンド・

Bewise Inc. www.tool-tool.com Reference source from the internet.

研磨材（けんまざい）は、相手を削り研ぎ磨くのに使う硬い粒ないし粉で、研削材ともいう。研磨研削作業には、古くから石榴石（ざくろ石）、 エメリーなど天然鉱物が使われてきたが、19世紀末にそれらよりも硬い人造研削材が工業生産され、現在は人造品が主流である。

こまかい研磨材は磨き粉に使える。ハートの形の穴を切り抜いたゴムシートを石材に貼り、研磨材をサンドブラストすれば、その形の窪みが彫れる。結合剤を加えて研削砥石に仕上げ、グラインダーで回せば、包丁の刃こぼれをなおせる。身近なところでは、炊事用のスポンジタワシの裏側にも研磨材が入っている。不織布の研磨布紙である。

[編集] 種類

[編集] 基本的な4種類と使い分け

現在使われている人造研削材は、次の4種類に大別できる。

表の ヌープ硬度は単結晶の結晶面の値で、低純度の、あるいは焼結品の微結晶コランダム質研削材の硬度は、この値より低い。

ダイヤモンドは周期表のIV族の一番上の炭素が共有結合していて、最も硬い。立方晶窒化ホウ素は炭素の左隣のホウ素と右隣の窒素との化合物で、すこし硬度が低い。なお、同じ化学式でも常圧で安定な六方晶窒化ホウ素は、固体潤滑剤に用いられる軟らかいすべすべの物質である。

炭化ケイ素は、ダイヤモンドとケイ素との「あいのこ」で、ダイヤモンドより軟らかくケイ素より硬い。コランダムはIII族とVI族との化合物で、Al³⁺イオンとO^2-イオンとが、イオン結合している。

物質を磨き削る研磨材は硬いほどよい、となればダイヤモンド万能となるが、経済的な事情がまずある。炭化ケイ素およびコランダム質研削材の1kg当たりの価格は、ダイヤモンドおよび立方晶窒化ホウ素の1カラット当たりの価格と同じ桁である。カラットは0.2gである。

次に、ダイヤモンドと炭化ケイ素とは、鉄と鋼の研削研磨には向かないという化学的な宿命がある。磨きあるいは削る仕事は、むしる側とむしられる側との激しい接触のもとに行われ、鉄鋼は、銑鉄の 組成の4.25%まで炭素を含有できるので、ダイヤモンドや炭化ケイ素の砥石で研削研磨すれば、鉄鋼は炭素を吸収し、砥石を急激に減耗させる。鉄鋼は炭化 ケイ素中のケイ素も吸収する。量的に重要な相手先である鉄鋼に対しては、立方晶窒化ホウ素とコランダム質研磨材の出番となる。

表の4種類のほか、ラッピングなどの磨きの作業には、湿式に析出させた粉末状の、酸化クロム、酸化鉄II、アルミナなども使用される。

なお、立方晶窒化ホウ素がボラゾン（Borazon）、炭化ケイ素がカーボランダム（Carborundum）、コランダム質研磨材がアランダム（Alundum）と呼ばれることがあるが、それらはそれぞれを最初に工業化した会社の商品名である。

[編集] コランダム質研磨材の種類

コランダム質研磨材にはいくつかの種類がある。

白色電融アルミナ

粉末のアルミナをアーク炉で融解後、冷却し凝固させ、その塊を粉砕整粒する。酸化クロムなどを加え、ピンクないしルビー色を付けたのもある。

褐色電融アルミナ

ボーキサイトをアーク炉で融解し、還元してアルミナ分を高めたのち、冷却し凝固させ、その塊を粉砕整粒する。Tiイオン、Mgイオンほかの固溶により、いくぶん強靱になる。

アルミナ-ジルコニア

Al₂O₃- ZrO₂二元系は、たがいに若干の固溶限を持つ共晶系で、共晶点に近いジルコニア約40重量％と、ジルコニア約25％との、2種類の電融研磨材がある。共晶の微細組織を持つため、強靱である。

解砕型アルミナ

アルミナ質原料をアーク炉で融解し冷却凝固させるが、その際、粉砕機にかけずに、結晶粒ごとに解砕できるよう、工夫する。粒の破壊の起点になる傷を持たないため、減耗しにくく、精密仕上げ用砥石の原料に使われる。

焼結アルミナ

アーク炉で融解せず、粉末のアルミナあるいはボーキサイトを粒状に焼結させる。硬度は低いが、微晶の粒なので、減耗しにくい。樹脂結合の砥石にして、圧延前のステンレス鋼の傷とりに、もっぱら使われる。必要な粒度ばかりを製造できる利点がある。

[編集] 製造法

研磨材用のダイヤモンドと立方晶窒化ホウ素とは、主に 静的高温高圧法で、炭化ケイ素は抵抗型の電気炉で、電融コランダム塊はアーク炉で、製造される。

そうして作った素材には、未反応原料、副産物、装置材料などの不純物が混ざるので、相応する選別、精製処理を行う。

研 磨材は、数mmから数µmの範囲で数十種類の粒度に分けられた粒体ないし粉体であるから、大きい素材は、そのサイズに応じて階梯的に、各種の粉砕 機で細かくしてゆく。細かい粒度の粉砕では、たとえば、コランダム質の粉をつぶすのにコランダム質のライニングとアルミナ質ボールとのボールミルを使う、というような汚染防止もできるが、それに先立つ粗い粒はほとんど鉄鋼の刃板の粉砕機で粉砕するので、混入する鉄分を除去する工程が、付帯的に必要となる。磁力選別、酸洗などである。

研磨材の重要な性状のひとつは、粒度の正しさである。粒度がずれていると削る作業の勝手が狂う。粗い粒が混入していると、磨く表面に致命的な傷をつける。

炭 化ケイ素およびコランダム質研磨材につき、[JIS R6001:1998 研磨材の粒度]は、径約4mm強から径約50µmまでの「粗粒」の範囲で26段階、径約50µm強から径約3µmまでの「一般研磨材用微粉」の範囲で11 段階、径約60µmから径約1µm強までの「精密研磨用微粉」の範囲で18段階、の粒度を定め、それと別に、「JIS R6010:2000 研磨布紙用研磨材の粒度]は、径約2mmから径約60 µm強までの研磨布紙用研磨材「粗粒」の範囲で15段階の、粒度を定めている。径約と苦しくいうのは、研磨材の径は決してパチンコのタマのように一様でなく、正規分布的な幅をもつからである。

JISのいう「粗粒」の範囲の粒度分け（分級という)は、ふるい（篩）で行う。

JISのいう「微分」の範囲の粒度分けは、一個の球形固体粒子が無限に広い流体中を沈降する場合、その沈降速度は粒子径の2乗に比例するというストークスの式にしたがい、水中の沈降速度の差を利用して行う。

[編集] いくつかの仕上げ処理

粒形処理

力 ずくで相手を削る砥石用の研磨材は、密に詰る形の、すなわち、球に近い形の方がいい。そのために、研磨材をボールミルなどで共摺りしたりする。 逆に、サラサラと軽く仕上げる砥石用の研磨材は、尖った形の方がいい。また、研磨布紙に研磨材を埋めこむには、あらかじめ接着剤を塗った布紙を下向きに し、下に敷いた研磨材との間に静電圧をかけて研磨材を跳び上がらせるので、この場合も、尖った形の方がよい。跳び上がって、長径が垂直の向きに貼りつくの で、製品の切れ味がよい。粉砕機の機種で、粉砕された粒の形を変えることができる。また、横向きの気流の中に研磨材を注げば、細長い形の粒は、遠くへ飛 ぶ。

表面処理

粒の電気伝導度の高い方が、静電界で跳び上がりやすい。炭化ケイ素は問題ないが、コランダム質研磨材は、薬品を散布して跳び上がりやすくすることもある。また、砥石に作るときの、結合剤とのなじみをよくするため、研磨材に表面被膜を付けることも、広く行われる。

熱処理

褐色電融アルミナの研磨材は、加熱すると壊れにくくなる。粒内の非晶質が表面に滲み出し、破壊の起点となる傷を埋めるためである。

[編集] 用途

• サンドブラスト、バレル研磨、バフ仕上げ、ラッピングなどの加工作業には、そのままの姿で使われる。
• 研削砥石の原料に使われる。
• 研磨布紙の原料に使われる。
• 研磨テープの原料に使われる。

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