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Example: Concepts for the Fin Actuation System of the Spacecraft Technology Vehicle SHEFEX 2

During the reentry and the landing approach spacecrafts use actuation systems to deflect flaps or fins to create aerodynamic forces. The basic research and development is tested experimentally by specialised technology vehicles. A major topic (besides the aerodynamic loads) arises from the heating by the high velocity. So ceramic materials are a important technology to investigate (for the fins, but also for the ball bearings).

In this example the German Aerospace Center (DLR) converted a high-atmosphere rocket (sounding rocket) into a spacecraft technology vehicle to evaluate heat protection systems. To control the reentry flight path in the atmosphere a fin actuation system was used. The mission achieved a successful flight on 22. June 2012.

To simplify the integration into the rocket system the actuation system, the fins and the structure form a compact cylindrical module. We designed the concepts of the complete module and developed solutions for critical components.

general layout

concept of the actuator

The module has four fins. Accordingly there are four actuators (each with separate electronics) and a common power supply in the module. In order to optimise the weight we performed several investigations on the actual CAD model, how the various fin loads act on the structure.

We present the results on a reduced-complexity CAD model.

Front view of the module

Overall view of the module

Stress distribution in the module by the torsion from the aerodynamic loads