Computer Science – Performance
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.456h&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Computer Science
Performance
Scientific paper
Hot structures made of ceramic matrix composites (CMC) for space reentry vehicles play a key role regarding feasibility of advanced and reusable future space transportation systems. Thus realization of applicable flight hardware concerning hot primary structures like a nose cap or body flaps and thermal protection systems (TPS) requires system competence w.r.t. sophisticated know how in material processing, manufacturing and qualification of structural components and in all aspects from process control, use of NDI techniques, arc jet testing, hot structure testing to flight concept validation. This goal has been achieved so far by DLR while following a dedicated development road map since more than a decade culminating at present in the supply of the nose cap system for NASA's X-38; the flight hardware has been installed successfully in October 2001. A number of unique hardware development milestones had to be achieved in the past to finally reach this level of system competence. It is the intention of this paper to highlight the most important technical issues and achievements from the essential projects and developments to finally provide a comprehensive insight into DLR's past and future development road map w.r.t. CMC hot structures for space reentry vehicles. Based on DLR's C/C-SiC material which is produced with the inhouse developed liquid silicon infiltration process (LSI) the development strategy first concentrated on basic material properties evaluation in various arc jet testing facilities. As soon as a basic understanding of oxidation and erosion mechanisms had been achieved further efforts concentrated on inflight verification of both materials and design concepts for hot structures. Consequently coated and uncoated C/C-SiC specimens were integrated into the ablative heat shield of Russian FOTON capsules and they were tested during two missions in 1992 and 1994. Following on, a hot structure experiment called CETEX which principally was a kind of a little nose cap had been developed and tested during the EXPRESS mission in 1995. These three flight tests were the first ones in Europe carried out with such a kind of material and hot structural concept and manifold lessons learned w.r.t. material behaviour and structural design performance under the severe environment conditions of ballistic capsule reentry could be achieved. Within an ESA program called FESTIP we developed a new design concept for a rigid surface TPS based on CMC's which should be adaptable to the outer side of a cryogenic tank structure of a future SSTO vehicle. Special TPS concept features are (flat) integral stiffened CMC panels, hot CMC fasteners for outside attachment capability, thermal displacement compensation, sealing and insulation, provision of a purge gap etc. Two test samples have been constructed and manufactured in close cooperation with industrial companies and finally they were tested very successfully under realistic thermal and mechanical loading conditions. A further key technology is high temperature fastening of shell like CMC components; here two new CMC based fastener concepts featuring a combination of screwing and riveting methods could be developed and qualified even under high temperature fatigue loads within ESA and national German programs. In addition high temperature testing technology has been matured over years and some extraordinary tests of components like the EMA bearing for the X-38 body flaps designed and manufactured by MAN-T could be tested very successfully. Finally these developments put DLR in the position to develop and provide the nose cap system for X-38 from NASA and some of the most demanding basic features will be highlighted briefly (details in a separate paper). Reflecting the described developments and considering near future programs like CRV and other ongoing experimental developments it is obvious that we now entered a state of transition from basic technology development towards operational use of such kind of materials and structures.
Hald H.
Reimer T.
Weihs H.
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