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Total sample containment is an absolute requirement for Mars sample return missions, derived from the requirement to protect against uncontrolled introduction of potentially hazardous foreign material into the earth's biosphere. These constraints of planetary protection comprise one of the major remaining hurdles to low cost implementation of sample return missions. It is suggested here that to spread the costs of the program, the first mission should consider sterilizing the samples and canister surfaces while still in space during the return to Earth.

Total fluid volume in a hydroponic bioregenerative life support system for in space use is a critical design parameter because it drives system mass and the design of control systems. Total fluid volume, thermal effects, nutrient solution buffering capacity, and pH setpoint have been examined theoretically and experimentally in a Bioregenerative Life Support Test Bed (BLSTB). Aqueous solution pH control loop responses were characterized for simulated loads from growing lettuce plants, and tuning parameters developed for minimal overshoot and offset. Results are discussed that indicate these parameters play a significant role in designing sensor and control systems to maintain stable characteristics in minimized nutrient solution volumes.

The galactic and solar flare radiation environments associated with human travel to the Moon and Mars present hazards that can best be countered by shielding. This work examines some of the alternatives for achieving this shielding at modest cost to the space mission.