Wood Fibre Materials on Hot Sounding Rocket Structures

Throughout the history of aviation as well as space flight, wooden materials played a major role in the construction of primary as well as secondary structures. Being one of the first construction materials used in that field, it does not only offer low density and good relative strength properties, but also easy handling, simple production processes, low costs and last but not least a green, renewable resource. With its unique characteristics the worlds lightest and biggest aviation vehicles heavier than air were created. Because of its relatively low thermal conductivity and good ablative behaviour wooden materials are taken into consideration for the use of hot structures such as the leading edges of sounding rocket stabilising fins. As a mandatory and thus flight critical structure of ballistic flying vehicles, fins need to be aerodynamically effective, lightweight, stiff and heat resistant on its foremost front end, where high temperatures may arise from fluid stagnation and friction. In order to gain a deeper understanding and assess the usability of modern wood fibre materials being appropriate in that field jointly, a cooperation with the Technische Universität Dresden (TUD) and the German Aerospace Center (DLR) has been established. This paper describes the motivation of the research as well as the structural application with its functionality and boundary conditions. The choice of materials and its rationale for selection in combination with various screening test results are the core of this research. First impacts on the components´ design and an outlook for future research conclude this paper

Bio-based ablative thermal protection materials for space application

In the context of a growing bioeconomy, green renewable resources are of interest for the space industry. Because of its relatively low density, low thermal conductivity, easy handling and good ablative behaviour bio- and wood-based materials are taken into consideration for the use as a thermal protection system (TPS) material on hot structures such as the leading edges of stabilising fins, fairings, nose cones and other TPS applications. As a mandatory and thus flight critical structure of launch vehicles, these parts need to be aerodynamically effective, lightweight, stiff and heat resistant on its foremost front end, where high temperatures may arise from gas kinetic effects. In order to gain a deeper understanding and assess the applicability of modern bio- and wood-based materials, a systematic literature and patent analysis of bio- and wood-based materials in spaceflight has been conducted as a starting point for the research. To set a framework for the application of a bio-based material in space, functionality and boundary conditions have been analysed and form requirements for the development of the bio-based TPS material. Further, prototype materials with varying ingredients of natural fibres, binders and additives have been developed and characterised by a thermogravimetric analysis (TGA) to determine their general suitability as a TPS material. The materials have been additionally screened in more detail via the analyses of bulk density, thermal conductivity and specific heat capacity. Measurements under real environmental conditions in a plasma channel were carried out for further investigation and form the core of this work. With the defined requirements and results from screening tests and plasma channel tests a selection of the best-performing prototype material could be made. First impacts on launch vehicle’s design and an outlook for future research on bio-based TPS conclude this contribution

Sounding Rockets for Entry Research: SHEFEX Flight Test Program

Within research for space vehicles with Re-entry capability and hypersonic airplane development in the last decade sounding rocket systems became a major and important test bed. This paper will present an overview of the national development and flight test program SHEFEX (SHARP EDGE FLIGHT EXPERIMENT) of the German Aerospace Center DLR. After 2 successful flight campaigns in 2005 and 2012 DLR is now preparing the next test vehicle SHEFEX III, which is planned for launch in 2016. The paper will focus on the strategic test approach and scientific experiments on board in interaction and possibilities of the sounding rocket system. Also some spin off effects will be prescribed which will enhance the performance of the rocket system also outside re-entry research

SHEFEX II Mission Overview and Forst Results

Main goal of re-entry experiments is to verify technologies, mainly for thermal protection systems, and simulation tools regarding hypersonic gas flow and structural response. A full scale re-entry test flight is expensive and needs in general a launch system with orbital capacity. To simplify and to reduce costs a step by step approach seems to be practicable and less risky. Thus, sounding rockets are a very attractive vehicle to perform related research. Even, they do not cover the whole performance to accelerate the entry vehicle to real re-entry conditions; they allow generating interesting flight conditions to verify aerodynamic simulation tools. On June 22nd 2012 the second flight within the SHEFEX (Sharp Edge Flight Experiments) development program was successfully performed at Andoya Rocket Range in Norway. Despite of the loss of the hardware, 95% of the expected flight data was collected. This paper will present a short overview of the mission and the first results of the on board experiments. Most of the experiments were related to thermal protection systems and aerodynamic parameters with their structural response, but also innovative concepts for GNC and structural technology for some parts of the launch system could be demonstrated during the SHEFEX II flight. The detailed assessment and evaluation of the flight data will cover a couple of years and PhD’s

The SHEFEX Flight Test and Development Program

Within SHEFEX the step by step development results in stepwise increasing velocity and test duration. SHEFEX I performs a Mach 6 flight for 20 Seconds. SHEFEX II reaches Mach 10-11 for 45 Seconds. SHEFEX III is aimed to reach Mach 20 for 15 minutes, a significant and ambitious step which require a big sounding rocket which is currently not available, but under development in Brasil. Thus, the growing complexity of SHEFEX III is the right milestone within the Re-entry technology development road map to implement strategic co-operations and partnerships. On the test vehicle side, DLR leads the development with ASTRIUM as a strong industrial partner. On the launcher side, Brasil leads the VLM-1 Microlauncher development with DLR as a partner for the first application of the launch system within the SHEFEX III flight. But SHEFEX is not only a single path development for Re-entry. In the field of hypersonic aircraft and air breathing propulsion development the SHEFEX launch systems could be a standard rocket family for flight tests. The improvements in high temperature stable stabilizers, huge lift fairings to cover complex vehicles and high accurate pointing and control systems are applicable especially to such kinds of flight tests, which partially is already done within the HiFire and Scramspace Programs and could be used within the ESA HEXAFLY proposal. This paper will give an overview of the running SHEFEX III project and the related REX Free Flyer study. Also some related Spin off activities will be discusse

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

Key Experiments within the Shefex II Mission

After the successful hypersonic flight of SHEFEX I the next mission is under development. Within this paper the basic goals, architecture and key experiments 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 a FADS system, an actively cooled thermal protection element, advanced sensor equipment, high temperature antenna inserts etc. are part of the SHEFEX II experimental payload

SHEFEX II - Aerodynamic Re-Entry Controlled Sharp Edge Flight Experiment

In this paper the basic goals and architecture of the SHEFEX II mission is presented. Also launched by a two staged sounding rocket System SHEFEX II is 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 has been 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, ailerons and flaps, mechanical actuators and an automatic electronic control unit has been implemented. Special focus is 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 ofthe SHEFEX II experimental payload. A final 2 stage configuration has been selected considering Brazilian solid rocket boosters derived from the S 40 family. During the experiment phase a maximum entry velocity of Mach around 10 is expected for 50 seconds. Considering these flight conditions, the heat loads are not representative for a RLV re-entry, however, it allows to investigate the principal behaviour of such a facetted ceramic TPS, a sharp leading edge at the canards and fins and all associated gas flow effects and their structural response