Hybrid Navigation System for the SHEFEX-2 Mission

Abstract

In October 2005 the first experiment of the DLR hypersonic SHarp Edge Flight EXperiment Program was successfully launched at the Andøya Rocket Range in northern Norway with the purpose to investigate possible new shapes for future launcher or re-entry vehicles applying a shape with facetted surfaces and sharp edges. For 2010 the execution of the SHEFEX-2 experiment is planned. It shall focus on hypersonic flight control using steerable canard fins while new thermal-protection system concepts will also be a subject of investigation. The accurate control of the vehicle using the canards requires a high accuracy in knowledge of the angle of attack and the side slip angle. Both angles can only be derived from the flight path and an accurate inertial attitude measurement. The first can be achieved by using GPS measurements. The second can not be provided by an Inertial Navigation System due to the fact that drifts due to launch vibrations are exceeding the requirement. Therefore a star tracker is foreseen to update the attitude information shortly before re-entry. Since the case of SHEFEX-2 describes a re-entry scenario which is applicable to other re-entry missions the need arises to develop an integrated navigation system which can provide the navigation solution with needed accuracy. This navigation system shall combine the measurements from inertial measurement unit (IMU), GPS receiver and star tracker. A further extension to include other sensors shall be foreseen. The paper will describe the concept of the integrated navigation. A special focus is also laid on the analysis how the star tracker can be integrated into the SHEFEX-2 probe.