Hendrik Weihs

The Shefex Flight Experiment - Pathfinder Experiment for a Sky Based Test Facility

On Thursday, October 27th, 2005 the SHarp Edge Flight EXperiment SHEFEX has been successfully launched at the Andoya Rocket Range in northern Norway. The project, being performed under responsibility of the German Aerospace Center (DLR) flew on top of a two-stage solid propellant sounding rocket. One purpose of the experiment is the investigation of possible new shapes for future launcher or re-entry vehicles applying a shape with facetted surfaces and sharp edges and to enable the time accurate investi-gation of the flow effects and their structural answer during the hypersonic flight from 90 km down to an altitude of 20 km. Additionally, the SHEFEX project is a starting point for a series of experiments which enable the acquisition of important knowledge in hypersonic free flight experimentation and which are an excellent test bed for new technological concepts. The present paper gives an overview about the philosophy and the layout of ex- periment and introduces preliminary outcomes of the post-flight analysis.

Thermal Testing of the Sharp Leading Edge of SHEFEXII

The octahedral sharp leading edge of SHEFEXII is made from C/C-SiC fiber reinforced ceramic. It is instrumented by three thermocouples and eight pressure ports. A duplicate was ground-tested in arc-heated wind tunnel L3K. Transient thermal response of the material to the load was also determined by the heat-balance method HEATS and compared to the measurement data. During ground-testing, the hermocouples measured 1179°C, whereas the maximum temperature recorded during flight was measured at 30km altitude with 848°C. The simulated data corresponds well to both thermocouple data and data from an external infrared camera. During ground-testing, the very tip of the leading edge reaches 1635°C. The nose was in good order after ground testing.

Three-Dimensional Thermal Analysis of the HIFiRE-5 Ceramic Fin

The German Aerospace Center (DLR) has developed a ceramic fin experiment (FinEx) for the HIFiRE-5 flight in order to test the performance of new structures with sharp leading edges during flight. The analysis of the thermal performance of the fin has been foreseen to be conducted by in-depth mounted thermocouples protocolling temperatures during flight. In a cooperative attempt between DLR and the Institut fur Raumfahrtsysteme (IRS) of the University of Stuttgart, the thermal behavior is studied. In this paper, an approach is presented to determine the heat flux distribution onto the surface of the three-dimensional geometry of the fin. Using the Non-Integer System Identification (NISI) method, heat flux onto different surface elements is derived from only three thermocouples mounted inside the fin. Moreover, to increase accuracy, an area-weighted inverse method is used. The principal proof of concept is given based on a finite element thermal analysis of a cube. Measurements with a backup fin are used to show the approach experimentally in a plasma wind tunnel. Finally, the in-flight data has been evaluated and heat flux onto the fins during flight is presented. It can be concluded that the method is strongly dependent on surface discretization. However, the qualitative distribution is accurately determined. This approach allows to improve heat flux measurements for sparsely equipped flight hardware.

Comparison of Faceted and Blunt Lifting Bodies for Reentry Flights

The design of a reentry vehicle strongly depends on the entry strategy of the projected mission. From the aerodynamic point of view, the layout of a hypersonic vehicle is a compromise between a vehicle being blunt enough to reduce the aerodynamic heating and sharp enough to obtain acceptable aerodynamic and propulsive efficiency. The selected flight configurations in this paper are wingless lifting bodies. Two different types of lifting bodies are compared: a sharp and a blunt body. The chosen blunt bicone is one of the Reusability Flight Experiment geometries, which were designed in the frame of the DLR, German Aerospace Center vehicle concept study of Reusability Flight Experiment. The sharp configuration is one of the DLR, German Aerospace Center Sharp Edge Flight Experiment configurations, which are a faceted body with sharp leading edge. The focus of the present study is the discussion of advantages and drawbacks of both concepts with respect to structure and aerodynamics.