Materials for Structural and Thermal Preservation of Sample Return Payload During Earth Entry and Landing, Phase II

To maximize reliability, Earth entry/landing vehicles for robotic sample return missions will comprise an aeroshell, a crushable layer that will absorb the energy of the ballistic impact landing, and a sample container inside the crushable layer; parachutes will not be used. Lightweight cellular solids are being considered for the crushable layer, but many other engineered foams with different strengths and energy absorption capacities are available. By using foams of different materials with different mechanical properties and different relative densities, the crush behavior of the layer can be tailored. In addition to brittle crushing of carbon foams or ductile collapse of metallic foams, other energy-absorbing mechanisms are available, some of which have previously been tested at high strain rates for use as underbody armor on military vehicles to mitigate blast effects from improvised explosive devices. In this project, high strain rate compression test data for Ultrametrsquo;s engineered foams will be used to mature the technology for impact absorption applications, with both brittle and ductile foams as a key element. The candidate impact absorption material database will be expanded via additional split Hopkinson bar testing, more detailed characterization of foam behavior will be performed, and an engineering model will be developed to quickly and easily determine the optimal foam architecture for a given set of mission (e.g. spacecraft and Earth impact) parameters. The results will be used to design and fabricate subscale and full-scale prototypes that will incorporate a minimum-mass, low thermal conductivity crushable layer that can be used for sample return missions with high impact velocities. The subscale unit and one full-scale unit will undergo drop testing to verify performance.