This paper presents the results of the design verification tests for the SLA-561V backshell and back interface plate (BIP) of the Stardust Discovery Class Mission Sample Return Capsule (SRC). The Stardust spacecraft will fly by Comet Wild-2, collect cometary and interstellar dust and return them back to earth in the SRC at the fastest earth re-entry to date. The SLA-561V material, manufactured by Lockheed Martin Michoud, will be used on the backshell and BIP of the SRC. The cometary particles and interstellar dust will be collected in a tray filled with the novel aerogel material, which will be designed and built by the Jet Propulsion Laboratory (JPL). The SRC is designed as a clamshell to allow the extension of the aerogel tray during the collection period. The SRC clamshell will remain open for several years and then close and seal before re-entry to earth. Therefore, it is important to test the seal design of the joint between the PICA forebody and the SLA-561V backshell. The verification tests were performed in three NASA Ames Arc Jet facilities. The objectives were to verify designs of the seal and several penetrations in the backshell and BIP, such as the vents, electrical cable interface, the pushoff pad, and the attachment point, at the predicted peak heat flux and heat load conditions.

This paper presents the development of the light weight Phenolic Impregnated Carbon Ablators (PICA) and its thermal performance in a simulated heating environment for planetary entry probes. PICA material was developed as a member of the Light Weight Ceramic Ablators (LCAs) family, and since then, the manufacturing process of this material was significantly unproved. The density of PICA material ranges from 0.224 to 0.321 g/cc having uniform resin distribution within the fibrous substrate. Surface densification was also developed to improve the ablation characteristics of PICA against extremely high stagnation pressures. The thermal performance of PICA was evaluated in the Ames arc jet facility at cold wall heat fluxes from 425 to 3360 W/cm and surface pressures of 0.1 to 0.43 attn. Heat loads used in these tests varied from 6,245 to 33,600 J/cm and are representative of the entry conditions of several proposed Discovery missions. Surface and in-depth temperatures were measured by using optical pyrometers and thermocouples. Surface recession was also measured by using a template and a height gage. The ablation characteristics and efficiency of the PICA is quantified by using the effective heat of ablation, and the thermal penetration response is evaluated by the thermal soak data. In addition, comparison of the thermal performance of standard and surface densified PICA is also discussed.

New Light Weight Ceramic Ablators (LCAs) were produced by using ceramic and carbon fibrous substrates impregnated with silicone and phenolic resins. Special infiltration techniques (patent pending) were developed to control the amount of organic resin in the highly porous fiber matrices, so that the final densities of LCAs range from 0.224 to 0.30 g/cu cm. This paper presents the thermal and ablation performance of the Silicone Impregnated Reusable Ceramic Ablators (SIRCA) in a simulated Mars entry heating environment. Testing was conducted in the Ames 60 MW Interaction Heating Facility (IHF) and 20 MW Aerodynamic Heating Facility (AHF). Test results show that the ablation characteristics of SIRCA are divided into three regimes: non-receding, surface coalescent, and receding. Four different Reusable Surface Insulation (RSI) substrates were used in the production of SIRCA to determine the effect of substrate compositions on the ablation performance. SIRCA with high-purity silica fibers generally performed better at high heating rates. Samples of SIRCA were tested at heating rates ranging from 45 to 550 W/sq cm and at stagnation pressures of 0.02 to 0.47 atm. Several samples were also tested at a heating environment simulating the Mars Aerocapturing mission, which generally consists of a low heating rate and a very high heat load. Material characterizations were also conducted to evaluate the material's mechanical, thermal, and optical properties. The effective thermal conductivity of SIRCA is comparable to that of the RSI substrates, and the emissivity of the charred SIRCA was measured to be about 0.92. Several samples of SIRCA were also exposed to the same heating condition for five cycles, and no additional significant mass loss or recession was observed. (Author)