• Expandable structures. This project element uses lunar regolith as part of a pressurized architecture, which is somewhat cumbersome. It is not clear that this is the best design solution because, for example, the abrasive dust in a low-gravity situation could be a menace to equipment and personnel.

  • Advanced composite structures. Exotic materials, such as lightweight composites, often promise great advantages on paper and sometimes in practice. It was not clear from the presentation of the team responsible for this element how and where these composite materials were going to be applied throughout the Constellation Program. The performance benefit or the figure of merit was not clearly identified. Composite materials may potentially provide significant advantages in weight reduction, but system trade-offs are needed in order to identify and quantify those gains.

  • Facilities. No new facilities were identified by the committee as needed to validate performance capabilities.

  • Radiation shielding kit. This technology, which proposes a type of blanket or sleeping bag approach as a portable shield, is a good fundamental research area. However, unless its specific application to various program elements is identified, it is very difficult to see its impact. The use of this kit was not traded against other competing options, and it requires figures of merit.

Alignment with the Objectives of the Vision for Space Exploration: Yellow Flag

The performance benefit to the VSE and Constellation programs from the Structures, Materials, and Mechanisms project may not be fully achieved because of an apparent lack of specific requirements coming from the Constellation Program office. There appears to be little in the way of enabling technology in this project. Therefore, a strong push for these technologies by the customer is not apparent.

02
ABLATIVE THERMAL PROTECTION SYSTEM FOR THE CREW EXPLORATION VEHICLE

Objective

Extremely large heat fluxes are experienced by the Crew Exploration Vehicle (CEV) during reentry from the Moon or Mars. An ablative heat shield is required for thermal protection. The heat shield design and thermal protection system (TPS) material qualification represent major technological challenges. The NASA team for this project stated that the present TRL is 4. The TRL needs to be advanced to 6 to support the CEV project.

Status

The project team is composed of NASA, the companies producing the materials, and the CEV contractor. The work is being carried out in a coordinated manner and, overall, is of good quality. The currently used metrics are appropriate. It appears that an upgrade to the arc-jet facility at NASA’s Ames Research Center (ARC) will take place that will improve its flow simulation capabilities.

Material test specimens and TPS materials for the primary and backup CEV heat shields are being produced by aerospace companies. The CEV contractor has built a full-scale heat shield test article and will build the flight heat shield. These developments are being directed and reviewed by NASA to ensure the coordinated consideration of reentry mechanical and thermal loads. There is no possibility of alternate technologies being developed within the ETDP. The plan is to have an acceptable TPS design by CEV Preliminary Design Review (PDR) and to have the technology matured by CEV Final Design Review (FDR).

Ratings

Quality: Yellow Flag

The heat shield is being designed using heating rate predictions from an uncoupled analysis; that is, the char surface temperatures are assumed to be radiation equilibrium temperatures rather than being calculated from a heat



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