Thrust vectoring

A thrust vector control allows steering movements by selectively directing the exhaust jet of a drive. It is mostly used in military aircraft and missiles, in order to improve maneuverability. This can be achieved by thrusters, deflectors at the nozzle outlet, or pivoting of the entire nozzle.

In addition to conventional take-off planes landing thrust vectoring is also used whiz; Here the aircraft is supported by vertically directed downward thrust during vertical takeoff. For the horizontal flight, the nozzle be rotated in the appropriate position, to enable the aircraft propulsion, lift is generated in a conventional manner by the vanes.

Technology

What is needed is a thrust vector control for long-range missiles, since during the start-up phase as well as in the vacuum of space an aerodynamic control is not possible. For smaller missiles and fighter aircraft they can support or replace to increase the maneuverability of the rudder. In an aircraft, it allows much higher angle of attack, so controllable flight conditions beyond the critical angle of attack are possible. In the German - American Rockwell - MBB X-31 project were achieved angle up to 70 ° without loss of control of the aircraft, for example.

The biggest problem in mass production of air and spacecraft with 3D thrust vector control is the thermal load on the nozzle, which calls for materials that are available at reasonable prices since the end of the 20th century.

The same principle also jet drives work in shipbuilding. Thermal stress is in shipbuilding naturally not relevant. The thrust vector control was used here already about 50 years ago.

2D and 3D control

The thrust vector control is divided into 2D and 3D versions. If the exhaust jet is deflected in one plane only, this is referred to as 2D thrust vectoring, whereas with a swiveling nozzle in all directions is called a 3D thrust vectoring. The reverse thrust for braking aircraft is defined in part as a kind of 2D thrust vectoring and has been used since the late 1950s in civil aviation (the first civil aircraft with a standard thrust reverser was the Boeing 707).

One of the first machines were allocated a 2D thrust vectoring, was the British Hawker P.1127 VTOL aircraft. This formed the basis for the later Harrier, which also used the 2D thrust vectoring for vertical takeoffs and landings. As can also be started at any intermediate position of the thrust vectoring, are at high payload requirements, so-called jump- starts with a short Anrollstrecke possible. On board an aircraft carrier, this may involve the use of " jumps ". In modern fighter aircraft, the 2D thrust vectoring, in addition to the advantages for takeoffs and landings, primarily used to improve air combat skills in " Dog Fight ". The pitching motion can be improved as well as the rolling movements when the machine has at least two engines. On the other hand, a 2D yaw thrust vector control has no effect. The first standard with such a control series equipped fighter aircraft was put into service in the 2005 American F- 22 Raptor. The delivered since 2002 Su- 30MKI of the Indian Air Force is retrofitted with a 2D thrust vectoring since 2006 by Hindustan Aeronautics.

A 3D thrust vector control also supports the yaw motions of a machine as opposed to 2D models. Although, such a control has already been tested on a variety of testing platforms, inter alia, at the German -American research aircraft X -31, there is currently no standard machine that comes standard with a 3-D derivative. This may change with the Russian Su- 35BM is their planned service provision for the year 2012. Also for the Euro Fighter Typhoon Tranche 3B is a 3D thrust vector control in development.

Technology in rocket

When rockets are two types of thrust vector control systems have mainly enforced:

• Tilting of the complete rocket engine in two axes, which is gimbaled
• Pivoting the nozzle, it will be used predominantly in solid boosters (for example, the Space Shuttle Solid Rocket Booster ), because a pivoting of the entire booster is not possible.

The following other types of thrust vector control lists, which have had only a limited distribution:

• Small swiveling thrusters, called Vernierdüsen (eg Soyuz )
• Injection of liquid into the side part of the nozzle, by the evaporation of the liquid influences the extent of the combustion gases and thereby manipulate the thrust vector. ( UGM -27 Polaris )
• Rotatable thruster in the exhaust stream (A4)
• Injecting air into the side part of the nozzle by the change in pressure will also change the thrust vector.
• The exhaust gases of the gas generator ( a device that burns fuel to provide energy for the turbo pumps provide ) is redirected to a swiveling nozzle, which in turn generates a variable thrust vector.

Actuators

To pivot the nozzle predominantly hydraulic or electric actuators are used. For very large engines (both the first stage of Ariane 5, Delta IV, Atlas, Space Shuttle ) are due to the required high forces used hydraulic actuators. In the upper levels ( for example, the Ariane 5 and Delta IV ) Electrical actuators are for use, since this energy use more efficient and easier to store and install are (no hydraulic oil).

Energy sources for thrust vector systems

As the power source for hydraulic thrust vector actuators mostly chemically driven pumps come into play (eg Space Shuttle ). The Saturn V rocket, the entire thrust vector control system was driven by the fuel system, the already existing turbo pump as supplied the energy needed and replaced a separate drive system. However, the weight reduction was offset by the requirement that the entire hydraulic system, in particular the seals had to be compatible with the fuel.

Another energy source for the thrust vector control are hydraulic accumulators. So sets the Ariane 5, a spherical tank one containing the hydraulic fluid and pressurized by nitrogen under pressure. The existing pressure is sufficient to provide enough energy for a launch. The unused oil is burned in the exhaust jet.

Platforms

Below warplanes are listed, which have a thrust vector control.

1 The steering effect of a thrust vector control system is composed of the motion, and the thrust of the engines. It acts orthogonal to the flight axis, and can be determined by the following equation:

FS - steering effect of the thrust vector control at maximum deflection FT - Maximum thrust of the engine in afterburner B - Maximum possible deflection angle of the thrust vector control