Jose Longo

The Sharp Edge Flight Experiment SHEFEX II, a Mission Overview and Status

After the successful flight of SHEFEX I the next mission is under development. Within this paper the basic goals and architecture of the SHEFEX II mission will be presented. Also launched by a two staged sounding rocket system SHEFEX II will be a consequent next step in technology test and demonstration. Considering all experience and collected flight data obtained during the SHEFEX I Mission, the test vehicle will be re-designed and extended by an active control system, which allows active aerodynamic control during the re-entry phase. Thus, ceramic based aerodynamic control elements like rudders or flaps, mechanical actuators and an automatic electronic control unit will be implemented. Special focus will be taken on improved GNC Elements. In addition, some other experiments including an actively cooled thermal protection element, advanced sensor equipment, high temperature antenna inserts etc. are part of the SHEFEX II experimental payload.

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.

Aerothermodynamics - A critical review at DLR

Abstract The paper presents the results of a study done for the German Aerospace Center, DLR. 1 The goal of the study is to identify the required design capabilities in external hypersonic aerothermodynamics for future space transportation vehicles. Lessons learned from the latest German program on Technologies for Reusable Future Space Transportation Systems, TETRA, as well as experiences collected from past European technology programs and flight vehicles are taken into account. The study does not go in to details since it pretends to be a reference for future research programs in aerothermodynamics. The potentials and shortcomings of the major prediction tools for aerothermodynamics, i.e., computational fluid dynamics and wind tunnels are shortly highlighted. Overviews of the most relevant external flow problems encountered during the design of space vehicles are presented. Research fields that require serious improvements are also identified.

X-38 integrated aero- and aerothermodynamic activities

Abstract The characterisation of the aeroshape selected for the X-38 [Crew Return Vehicle (CRV) demonstrator] is presently being performed as a co-operative endeavour between NASA, DLR (through its TETRA Program), and the European Space Agency (ESA) with Dassault Aviation integrating the aerodynamic and aerothermodynamic activities. The methodologies selected for characterizing the aerodynamic and aerothermodynamic environment of the X-38 are presented.

Computational Comparisons of the Interaction of a Lateral Jet on a Supersonic Generic Missile

*† ‡ The paper deals with the comparison of computations made at DLR and ISL on the interaction between a lateral jet issuing from a generic missile body and the oncoming supersonic cross-flow. Steady-state numerical simulations are carried out by 3D, viscous, turbulent, Reynolds-Averaged Navier-Stokes codes; at DLR, a hybrid mesh is used for the TAU calculation, whereas at ISL a hexahedral mesh is used for the CFX computation. Experimental data acquired in the DLR wind tunnel TMK in Cologne act as references for the computations. Calculations are made for a cross-flow Mach number of 2.8, for angles of attack of -5, 0 and 10 degrees and for a jet ejection pressure ratio of 100. The test model is a cone-cylinder-flare body with a side-jet nozzle located in the cylindrical part, representing a simple generic high-speed missile configuration. Surface pressure measurements were carried out in order to validate the corresponding computations. The agreement between the computations and the experiments in terms of pressure distribution is obtained with a high degree of accuracy by the codes, in spite of some small discrepancies.

Considerations on CFD modeling for the design of re-entry vehicles

Abstract The paper focuses on the importance of a good geometrical representation of re-entry vehicles for hypersonic flow simulations by means of CFD. Based on investigations carried out by DLR throughout past re-entry programs, it is shown that in many cases geometrical simplifications of configurations used for CFD evaluation introduce errors in aerodynamic and aerothermodynamic quantities comparable or even higher than those arising from numerical accuracy or lack of physical modeling of the respective code. Since it is very often not possible to upgrade an already existing configuration due to layout incompatibilities of the grid, a good practice is to include as many details as possible in the initial grid design.

Advanced Flight Analysis of SHEFEX-I

The first SHarp Edge Flight EXperiment of DLR has been established to demonstrate the feasibility of space vehicles with facetted Thermal Protection System (TPS). This study presents the thermodynamic behaviour of SHEFEX-I during the re-entry flight range of 60 km down to 20 km using a multidisciplinary simulation. Major effects like influence of the thermocouple position, overhang of the glue, and contact condition between the heat flux sensor and the TPS are analysed. The results of numerical calculations agree well with the experimental data.

Numerical study of hypersonic missiles with lattice wings using an actuator disk

A missile with lattice wings is numerically investigated. In order to reduce drastically the computational cost for such a geometry the actuator disk technique is used. Therefore, lattice wings are replaced by artificial boundary conditions. At the actuator disk location, the forces involved by the grid fin are interpolated from an experimental database. Firstly, in order to validate the methodology this technique has been applied to an isolated grid fin and the numerical results have been compared with experiments. Then, the actuator disk has been coupled with a body to investigate a complete missile. The configuration has been computed for different Mach numbers and angles of attack and the predictions of forces and moments compared against experimental data. This validated the method and showed its potential for vehicle design.

Aerodynamic optimization of re-entry capsules

Abstract Methods for aerodynamic design and optimization based on linear theory are not well suited for modelling non-linear phenomenons. Their results only represent approximations of real optima. In the present study a new method based on non-linear theory, i.e. the solution of the Euler/Navier–Stokes equations, has been applied to improve these approximations. The structure of the system as well as the incorporated modules are described. Aerodynamic optimizations of a biconic re-entry capsule with respect to the lift-to-drag ratio, the effective volume and the stability are presented and discussed. The method proves to be a robust and relative efficient tool for aerodynamic design of modern aerospace vehicles. An increase in the performance of computer systems will result in an increase in the efficiency as well. It is shown that the method keeps and sometimes expands the established knowledge base of experienced engineers but reduces the design cycle times significantly.

Aerothermodynamics issues of the DLR hypersonic flight experiment SHEFEX-I

Here is presented an overview of the hypersonic experiment on sharp edge concepts, SHEFEX-I. The project, being performed under responsibility of the German Aerospace Center (DLR), is aimed to investigate the behavior and the possibilities of an improved shape for aerospace vehicles considering sharp edges and facetted surfaces. It is a basic in-flight experimentation research on hypersonic technologies for future launcher vehicles but not a re-entry experiment. Additionally, the SHEFEX-I project is the 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 experiment which successfully flew on top of a two-stage solid propellant sounding rocket on October 27th, 2005 from Andoya Rocket Range in northern Norway, enabled time accurate investigation of the flow effects and their structural answer during a hypersonic flight Ma~6 from 90 km down to an altitude of 20 km. The present paper gives an overview about the aerothermodynamic philosophy and introduces some main outcomes of the post-flight analysis.