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NASA NTRS2012

Passive Thrust Oscillation Mitigation for the CEV Crew Pallet System

The Crew Exploration Vehicle (CEV) was intended to be the next-generation human spacecraft for the Constellation Program. The CEV Isolator Strut mechanism was designed to mitigate loads imparted to the CEV crew caused by the Thrust Oscillation (TO) phenomenon of the proposed Ares I Launch Vehicle (LV). The Isolator Strut was also designed to be compatible with Launch Abort (LA) contingencies and landing scenarios. Prototype struts were designed, built, and tested in component, sub-system, and system-level testing. The design of the strut, the results of the tests, and the conclusions and lessons learned from the program will be explored in this paper.

Sammons, Matthew↗

NASA NTRS2011

Design and Analysis of Mirror Modules for IXO and Beyond

Advancements in X-ray astronomy demand thin, light, and closely packed thin optics which lend themselves to segmentation of the annular mirrors and, in turn, a modular approach to the mirror design. The functionality requirements of such a mirror module are well understood. A baseline modular concept for the proposed International X-Ray Observatory (IXO) Flight Mirror Assembly (FMA) consisting of 14,000 glass mirror segments divided into 60 modules was developed and extensively analyzed. Through this development, our understanding of module loads, mirror stress, thermal performance, and gravity distortion have greatly progressed. The latest progress in each of these areas is discussed herein. Gravity distortion during horizontal X-ray testing and on-orbit thermal performance have proved especially difficult design challenges. In light of these challenges, fundamental trades in modular X-ray mirror design have been performed. Future directions in module X-ray mirror design are explored including the development of a 1.8 m diameter FMA utilizing smaller mirror modules. The effect of module size on mirror stress, module self-weight distortion, thermal control, and range of segment sizes required is explored with advantages demonstrated from smaller module size in most cases.

McClelland, Ryan S.↗