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Space power systems include power source, storage, and management subsystems. In current crewed spacecraft designs, solar cells are the power source, batteries provide storage, and the crew performs any required load scheduling. For future crewed planetary surface systems using Advanced Life Support, we assume that plants will be grown to produce much of the crew's food and that nuclear power will be employed. Battery storage is much more costly than nuclear power capacity and so is not likely to be provided. We investigate scheduling of power demands to reduce the required peak power generating capacity. The peak to average power ratio is a good measure of power capacity efficiency. We can easily schedule power demands to reduce the peak power below the potential maximum, but simple scheduling rules may not achieve the lowest possible peak to average power ratio.

How much integrated system level test should be performed on a spacecraft before it is launched? Although sometimes system test is minimized, experience shows that systems level testing should be thorough and complete. Reducing subsystem testing is a less dangerous way to save cost, since it risks finding problems later in system test, while cutting systems test risks finding them even later on orbit. Human-rated spacecraft test planning is informal, subjective, and inconsistent, and its extent is often determined by the decision maker's risk tolerance, decision-making style, and long-term or short-term view. Decisions on what to test should be guided by an overall mission cost-benefit analysis, similar to the risk analysis used to guide development efforts.