Frank Siebe

Experimental Verification of Heat-Flux Mitigation by Electromagnetic Fields in Partially-Ionized-Argon Flows

This paper describes an experimental study on heat-flux mitigation within high-enthalpy ionized-argon flows by application of an external magnetic-induction field. Two different axially symmetric test models containing water-cooled magnet coils have been investigated. The models have been made of a material with low thermal conductivity to visualize surface-temperature distribution.The latter has been measured by infrared thermography. Heat-flux rates have been derived from measured front- and rear-surface temperatures, taking into account temperature-dependent material characteristics and considering radiative-cooling exchange to the environment. Flowfield properties have been quantitatively characterized by laser-induced fluorescence, microwave interferometry, emission spectroscopy, electrostatic probes, and pitot probes. In addition, high-quality video recordings and photographs have been taken for shock-layer visualization. Remarkable measured surface-temperature reductions (16 and 44%) and derived heat-flux mitigations (46 and 85%) have been observed in the presence of an externally applied magnetic-induction field.

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.

Hot-Gas Side Jet in a Supersonic Freestream

The present paper reports on the interaction of a hot side jet in a supersonic freestream and compares the effects with results from cold-gas jet investigations. With high-speed schlieren videos, a significant enlargement of the separation area has been ascertained upstream from the hot-gas jet and quantitatively confirmed with wall pressure measurements. The schlieren videos also show a strong oscillation of the separation and bow shock. By using an algorithm that analyzes the similarity of neighboring images, the oscillation frequency of the separation and bow shock has been measured to be 11.3 kHz. As a consequence of the dominant shocks in the area in front of the jet, the hot jet plume is screened off strongly from the freestream, thus resulting in an upstream inclination. Finally, high-speed videos have revealed large-scale structures in the hot-gas jet and their convection velocities have been analyzed. According to the shocks, the large-scale structures oscillate at 11.3 kHz. Jet oscillation is thus excited by the interaction of the hot-gas jet with the freestream and not by resonances from the combustion chamber.

Instrumentation of the SHEFEX-II Flight Experiment and Selected Flight Data

The SHEFEX-II hypersonic flight experiment was launched from Andoya rocket range in Norway on 22.06.2012 consisting of an extensively instrumented scientific payload on top of a two-stage rocket configuration. With an apogee of about 177 km, the vehicle achieved flight velocities up to 2790 m/s corresponding to Mach numbers up to 9.3. Almost all heat flux, temperature and pressure sensors provided very clear data during ascent and descent phases. Measured pressure data from sensors at different locations of the scientific payload show consistent results concerning the aerodynamic behavior on the vehicle along the complete trajectory. Pressure fluctuations measured during ascent, show a good correlation to angle of attack variations. Calculated pressure coefficients from a CFD analysis at selected trajectory points are in good agreement with the measured pressure data.

Aerothermal Postflight Analysis of the Sharp Edge Flight Experiment-II

The aerothermal instrumentation of the Sharp Edge Hypersonic Flight Experiment SHEFEX-II, which was launched from Andoya Rocket Range on top of a two-stage rocket configuration, provided very useful flight data. Complementary to the pressure data, heat flux rate and surface temperature were measured at selected locations on the payload along the complete ascent and descent trajectory. Measured heat flux rate and pressure fluctuations show excellent correlation with angle-of-attack variations. Calculated heat flux evolution using a hypersonic boundary-layer code along the trajectory is in reasonable agreement with measured heat flux data during flight. Boundary-layer transition was measured at a boundary-layer edge Reynolds number of approximately 3·106 for both ascent and descent phases. The complementary analytical and numerical study for the flight rebuilding at selected flight points provided very useful data and allowed better understanding of the physical phenomena. Finally, a combined analytical–num...

Main Achievements of the Rocket Technology Flight Experiment ROTEX-T

Based on experience gathered during the hypersonic flight experiments SHEFEX-I and SHEFEX-II the German Aerospace Center (DLR) performed the extensively instrumented flight experiment ROTEX-T (ROcket Technology EXperiment-Transition). ROTEX-T was successfully launched on 19th July 2016 at 06:05 am CEST from the Esrange Space Center near Kiruna in northern Sweden. Students of the RWTH Aachen University supported the design of the project with numerical simulations. ROTEX-T was a low cost flight experiment mission without inertial measurement unit, reaction control and parachute system. The payload reached an altitude of 183 kilometers, performed a ballistic re-entry with a total flight time of approximately 446 seconds and was afterwards recovered by helicopter. An unique and modular data acquisition system with sampling rates of 20 Hz, 1 kHz, 10 kHz and 2000 kHz was developed for ROTEX-T to study also instationary aerothermal phenomena.