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This paper builds on a steady-state investigation of waste heat reuse in an Advanced Life Support System (ALSS) for a Mars mission with a low degree of crop growth. In past studies, such a system has been defined in terms of technology types, hot and cold stream identification and stream energy content. The maximum steady-state potential for power and cooling savings within the system was computed via the Pinch Method. In this paper, the next step is taken toward achieving a pragmatic estimate of costs and savings associated with waste heat reuse in terms of equivalent system mass (ESM). In this paper, the assumption of steady-state flows are discarded, and a proposed schedule is developed for activities that are of interest in terms of waste heat reuse. The advanced life support system for the Mars Dual Lander Transit Vehicle is the system of interest.

Solid Waste Management (SWM) systems of current and previous space flight missions have employed relatively uncomplicated methods of waste collection, storage and return to Earth. NASA's long-term objectives, however, will likely include human-rated missions that are longer in both duration and distance, with little to no opportunity for re-supply. Such missions will likely exert increased demands upon all sub-systems, particularly the SWM system. In order to provide guidance to SWM Research and Technology Development (R&TD) efforts and overall system development, the establishment of appropriate SWM system requirements is necessary. Because future long duration missions are not yet fully defined, thorough mission-specific requirements have not yet been drafted.

Long duration missions pose substantial new challenges for solid waste management in Advanced Life Support (ALS) systems. These possibly include storing large volumes of waste material in a safe manner, rendering wastes stable or sterilized for extended periods of time, and/or processing wastes for recovery of vital resources. This is further complicated because future missions remain ill-defined with respect to waste stream quantity, composition and generation schedule. Without definitive knowledge of this information, development of mission requirements is hampered. Additionally, even if waste streams were well characterized, other operational and processing needs require clarification (e.g. resource recovery requirements and planetary protection constraints). Therefore, the development of solid waste management (SWM) subsystem requirements for long duration space missions is an inherently uncertain, complex and iterative process.

To ensure that adequate water resources are available during a mission, any net water loss from the habitat must be balanced with an equivalent amount of makeup water. For a Mars transit mission, the primary sources of makeup water will likely involve water contained in shipped tanks and in prepackaged food. As mission length increases, it becomes more cost effective to increase system water closure (recovery and generation) than to launch adequate amounts of contained water. This trend may encourage designers to specify increased water recovery in lieu of higher food moisture content. However, food palatability requirements will likely declare that prepackaged foods have a minimum hydration (averaged over all food types). The food hydration requirement may even increase with mission duration. However, availability requirements for specific emergency scenarios may declare that determined quantities of water be provided in tanks, rather than as moisture in food.