James O. Arnold

Multilayer Film Assembly of Carbon Nanotubes

An approach to assemble multilayers of carbon nanotubes on a substrate is resented. Chemical vapor deposition using a transition metal catalyst formulation is used to grow the nanotubes. Results show a bilayer assembly of nanotubes each with a different density of tubes.

Development of Thermal Protection Materials for Future Mars Entry, Descent and Landing Systems

Entry Systems will play a crucial role as NASA develops the technologies required for Human Mars Exploration. The Exploration Technology Development Program Office established the Entry, Descent and Landing (EDL) Technology Development Project to develop Thermal Protection System (TPS) materials for insertion into future Mars Entry Systems. An assessment of current entry system technologies identified significant opportunity to improve the current state of the art in thermal protection materials in order to enable landing of heavy mass (40 mT) payloads. To accomplish this goal, the EDL Project has outlined a framework to define, develop and model the thermal protection system material concepts required to allow for the human exploration of Mars via aerocapture followed by entry. Two primary classes of ablative materials are being developed: rigid and flexible. The rigid ablatives will be applied to the acreage of a 10x30 m rigid mid L/D Aeroshell to endure the dual pulse heating (peak approx.500 W/sq cm). Likewise, flexible ablative materials are being developed for 20-30 m diameter deployable aerodynamic decelerator entry systems that could endure dual pulse heating (peak aprrox.120 W/sq cm). A technology Roadmap is presented that will be used for facilitating the maturation of both the rigid and flexible ablative materials through application of decision metrics (requirements, key performance parameters, TRL definitions, and evaluation criteria) used to assess and advance the various candidate TPS material technologies.

Thermal Protection for a Supersonic Inflatable Aerodynamic Decelerator Cover Panel System

This paper describes the development and design of the thermal protection for a cover panel system meant to insulate an inflatable decelerator from aerodynamic heating during entry into the Martian atmosphere. The inflatable decelerator, stowed just behind the shoulder of the entry capsule, is to be deployed during the supersonic descent portion of flight. Three options - named “hard”, “medium”, and “soft” - are considered in the design of the cover panel system. In each design cycle, requisite aerothermal environments are generated using a combination of high-fidelity computational fluid dynamics and engineering tools. The choice of a thermal protection system material for the cover panel system is based on the predicted maximum margined heat flux, and sized to the predicted maximum margined heat load along an entry trajectory. It is shown that the predicted aerothermal environments are benign enough to consider use of flexible thermal protection system materials with Space Shuttle flight heritage. Finally, recommendations are made for maturation of flexible material technology for this application and reduction of design analysis cycles.