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Thrust vectoring is a form of attitude or directional control that can be designed into any vehicle capable of moving in three dimensions through powered thrust, such as an aircraft, spacecraft, or submerged underwater vehicle. The tendency for a vehicle powered by rocketry or jet engines is to move in a direction exactly opposite that of the exhaust exiting from its rear-facing thrust nozzle. When this thrust is channeled to exit the vehicle at a different angle than the angle of the vehicle in reference to the horizon or its intended direction of travel, it can aid in rapid turns instead of simply relying on aerodynamic control surfaces or breaking rockets in spacecraft to do so.
Several advanced aircraft currently use thrust vectoring as of 2011 including the Russian Sukhoi SU-30 MKI which has also been sold to India, the F-22 Raptor fighter deployed by the US Air Force, and the EF or Eurofighter 2000 built for military service in the UK, Germany, Italy, and Spain. The AV-8B Harrier II jet is also an example of a thrust vectoring aircraft that was originally developed in the UK and has been in operation since 1981 by several participating North Atlantic Treaty Organization (NATO) nations, including Spain, Italy, and the US. The United States and Israel also worked on a program for the F-16 fighter aircraft known as multi-axis thrust vectoring (MATV) in the early 1990s.
Thrust vectoring has also been used on several rocket and spacecraft systems with notable recent examples in the 21st century being that of the Japanese Mu rocket and the European Space Agency (ESA) Small Missions for Advanced Research and Technology (SMART-1) moon mission launched in 2005. Earlier systems that have used thrust vectoring include the US Space Shuttle as well as the US Saturn V moon rockets of the 1960s. Several strategic nuclear missile systems in the US are also known to employ the technology, including the land-based Minuteman II intercontinental ballistic missile (ICBM) and submarine launched ballistic missiles (SLBMs) deployed on nuclear submarines.
Several different approaches have been taken to achieve thrust vector control. With aircraft, a typical approach is to tie the movement of the exhaust nozzle into the pilot's controls so that, not only do aircraft surfaces like the rudder and ailerons respond to his or her vector changes, but the exhaust nozzle moves in tandem with them. On the US F-22, the exhaust nozzle has freedom of movement within a 20-degree range, which gives the aircraft an increased roll rate of 50%. Roll rate is the ability of the aircraft to deviate in pitch — up and down — or yaw — left and right — from its central axis of movement while in flight. The Russian SU-30 MKI has an exhaust nozzle that can rotate 32 degrees in the horizontal plane and 15 degrees in the vertical, which allows the aircraft to perform high-speed banking maneuvers in 3-4 seconds at air speeds of around 217 to 249 miles per hour (350 to 400 kilometers per hour).
In spacecraft or rockets, thrust vectoring can involve moving the entire engine assembly within the body of the vehicle, known as gimballing, which was done with the US Saturn V rocket, or key components of the exhaust system can be moved in tandem. Solid propellant rocket motors like the Japanese Mu space launch vehicle cannot alter the direction of the thrust fuel, so they instead inject a cooling fluid along one side of the exhaust nozzle that forces hot exhaust gas to exit on the opposite side to provide a vectoring effect. This is also done in the solid-fueled Minuteman II missile deployed by the US, where its liquid-fueled Trident SLBMS use a hydraulic system to move the nozzle itself.
In spacecraft meant to leave the gravity well of the Earth, often the main thrust engine is separated from attitude control rockets or thrust vectoring systems, and each system can use different types of propulsion methods and fuels. Attempts have been made in space missions as of the early-21st century to tie these two propulsion systems together into one commonly fueled one. In the ESA SMART-1 mission, this was known as an all-electrical design for joint operation, referred to as the attitude and orbit control system (AOCS). The European Student Moon Orbiter (ESMO) planned for launch between 2014 to 2015 also uses thrust vectoring as part of a sophisticated ion propulsion system.
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