Vernier thruster

Vernierdüsen or Verniertriebwerke serve the thrust vector control of rocket, this means that the direction of flight of a rocket can be influenced by them. They are named after the mathematician Pierre Vernier (1580-1637) named, invented the vernier scale ( vernier ), can be read very closely with the lengths and angles.

Design and operation

Vernierdüsen are self- propellant rocket engines, which can be swung in one or two axes. They are, in contrast to the main engines ignited only when a change in path of the missile is needed. This minimizes the need for cooling. To keep the ignition of the engines simple and therefore reliable, hypergolic fuels are mostly used. These ignite automatically when matching of oxidizer and fuel in the combustion chamber; a separate igniter that could possibly fail, is not necessary.

Use

In most modern missiles ( Ariane, Delta, Atlas ) no more Vernierdüsen be used. In older types of missiles, such as the spacecraft, they are used historically limited still. In the picture the 20 large nozzles of Soyuz rocket are seen. In the outlying settings each, two Vernierdüsen are present in the central stage, the four main engines of four Vernierdüsen are surrounded.

The Space Shuttle Reaction Control System in Verniertriebwerke used for the position control in orbit.

Advantages and Disadvantages

Vernierdüsen found mainly in the early days of rocketry use. This was due to the immaturity of the hydraulic servo actuators, which were mainly used for thrust vector control. By using the Vernierdüsen or the main engines could be tightly assembled. This accounted for flexible cables for supplying fuel and the gimbal of the main engine. Only the smaller Vernierdüsen had to be turned, which was done with comparatively small actuators. Due to the smaller masses and forces the control out easier.

In modern rockets usually one or more gimbaled main engine is used for thrust vector control. About hydraulic (for large aircraft) or electrical actuators (for small engines or at higher levels) are the main engines pivoted (eg Space Shuttle: 10.5 ° transverse axis, 8.5 ° yaw axis ). Due to the sophistication of the modern thrust vector actuators and the omission of the Vernierdüsen whose swivel unit and fuel supply reliability of rockets can be increased.