Aerospike engine

Aero Spike (English " air spike ") is a rocket engine, the atmospheric conditions at different altitudes adapts automatically. An aerospike engine consumes low altitude 25 to 30% less fuel than traditional bell-shaped rocket engines. Aerospike engines are explored for some time and serve as the basis for many concepts of reusable spacecraft. At present there are, however, not have a functioning engine.

Principle

A traditional engine uses a large bell-shaped nozzle, to discharge the combustion gases, thereby converting the internal energy of the air flowing in the thrust supporting mass. However, the correct sizing of the nozzle cone depends on the external conditions. In high altitudes, is a much larger bell with a higher expansion ratio than needed at low altitude due to the lower external pressure ( greater difference between the combustion chamber pressure and ambient pressure).

The Aero Spike tries to circumvent this problem. Rather than shoot the combustion gases through a nozzle at the bell approach aerospike used several smaller, flat oriented combustion chambers on the outside. These generate shock waves ( the spine) are converted into thrust using a cylinder or V-shaped stem. It is formed from the sting on one side and the air flowing past on the other side a virtual bell - the air sting ( Aero - spike ).

In theory, however, an infinitely long sting would be needed to achieve ideal levels. In practice, the engine consists of only one spike approach that is open at the bottom. An air flow flowing through the spike, is used as a substitute sting so that the lower part of the virtual bell consists on both sides from an air stream.

In the altitude increases, the air pressure decreases. This allows the combustion gases to spread more and more with increasing height. The virtual bell expands and thus adapts to the changed conditions. In theory, an aerospike engine achieved a 90 percent efficiency, regardless of the air pressure. It thus surpasses any traditional rocket engine that needs to be developed for a height. For this reason, an aerospike engine is also ideally suited to be used in a single-stage reusable space shuttle as it reaches optimal performance at any altitude.

Cooling systems and fuel pumps are integrated into the inside of the spine.

Pros and Cons

Benefits

• Aero Spike consumes less fuel in theory up to 35% (low height).
• The direction control works without complicated gimbal the engines or baffles in the hot exhaust stream, as the thrust of the outer combustion chamber cells will simply be controlled accordingly different.
• The distribution of the combustion in several combustion chambers small, the risk of explosion is substantially reduced.
• An aerospike engine is lighter than a traditional and only about half as high.

Disadvantages

• The biggest problem in developing an aerospike - engine is the cooling of the central cone. A reduction of the spine reduces the effect as the surface with which the combustion gases coming into contact is reduced. However, a shortening of the spine is always associated with a reduction in performance. A second air flow in the sting can in turn counteract this effect.
• With a V-shaped linear aero - spike engines, as it is usually used to date in tests, there is by vortex formation on the sides of a power loss.

Tests and projects

A very early version of the Aero Spike was already used in the engines of the Messerschmitt Me 262.

Between 1950 and 1970, were carried out with different sizes and variants a total of 73 tests by the company Rocketdyne, NASA and the U.S. Air Force.

The engine assembly of the Soviet N1 moon rocket produced an aerospike effect.

For the NASA X-33 Venture Star project four XRS -2200 aerospike engines was based on the previous research developed and tested successfully from 1997 to 2000. The project, however, was discontinued due to excessive costs and technical problems of the X-33.

The first known test flight of an aerospike - engine was carried out on board a Lockheed SR -71 in the context of the linear aerospike SR -71 Experiment ( LASRE ).

In West Germany in the late sixties, has been working on an aerospike engine for the spacecraft Neptune.