balance for the ablating heat shield. The injection of the pyrolysis gases and char oxidation products (which may significantly change the prediction of the heating rate) is ignored. This approach does not represent the current state of the art and could lead to either an over- or underprediction of the bond-line temperatures late in the entry.

While industry has been involved in producing candidate TPS material, there is no significant involvement of the national laboratories. However, organizations such as Sandia National Laboratories as well as other Department of Energy (DOE) and Department of Defense (DOD) laboratories could contribute to this effort.

Effectiveness in Developing and Transitioning: Yellow Flag

Even though 40 years have elapsed since the Apollo 4 flight test and the state of the art in heat shield design has advanced significantly during that time, the ability to simulate a lunar-return Earth entry in ground-based facilities still does not exist. The planned ground-test arc-jet facility improvements are desirable, but they will not provide an adequate approximation of all flight conditions and cannot be scaled to the full heat shield dimensions. Within the present state of the art, it is not possible to build ground test facilities that will duplicate (or even adequately approximate) flight conditions. Only a reentry flight test at lunar-return velocity and at a scale sufficient to assess the effects of joints and gaps between the heat shield panels will qualify the heat shield for use on a crewed lunar-return mission. Because NASA had not made a decision at the time that the committee was carrying out its data gathering, the committee was not clear as to whether an uncrewed flight test is planned; if not, the effectiveness with which this project is being developed and transitioned would be labeled with a red flag.

Alignment with the Vision for Space Exploration: Yellow Flag

Planetary-return heating rates are much higher than lunar-return heating rates. A CEV-like vehicle entering at 13 km/s from Mars will experience peak stagnation-point heating rates (convective and radiative) three times greater than the lunar-return values. Furthermore, at 13 km/s the stagnation-point heat load is approximately 70 percent radiative, whereas for lunar-return entries it is less than 25 percent. Therefore, an entirely different heat shield design may be required for reentry from Mars; hence the present technology does not fully support the entire VSE.

03
LUNAR DUST MITIGATION

Objective

Dust was an issue for the Apollo astronauts, and it continues to be an issue for the Mars Exploration Rovers (MERs). Dust presents both a health risk (e.g., from inhalation and damage to spacesuits) and a mission risk (e.g., for its obscuring of landing sites, causing equipment to overheat, and covering solar arrays). In response to these dust issues, NASA established the Lunar Dust Mitigation project, with the goal of providing the “knowledge and technologies (to TRL 6) required to address adverse dust effects to humans and to exploration systems and equipment, which will reduce life cycle cost and risk, and will increase the probability of sustainable and successful lunar missions.”5

Status

The Lunar Dust Mitigation project has clearly defined requirements that have been delineated into well-stated project plans to bring the TRL to 5. The development objectives of each of these plans were understood by the team members as clearly stated deliverables. Interaction within the NASA organizations involved in the project seems appropriate. The expertise of dealing with regolith resides within NASA, but outside sources are being sought in appropriate areas where industrial cooperation can benefit the program. The extensibility to Mars appears to be assumed, as the Moon is the current focus. The team seems to be motivated and enthusiastic about achieving its

5

National Aeronautics and Space Administration, Exploration Technology Development Program. Technology Development Project Plan. Dust Management Project Plan, Document No. DUST-PLN-0001, NASA Glenn Research Center, Cleveland, Ohio, November 2007.



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