Mars life support systems

Abstract

Background: A critical element of planning human missions to Mars involves life support systems. The requirements for air, food, water and waste disposal materials in human missions to Mars total well over 100 metric tons and possibly as much as 200 metric tons. Translated back into an equivalent mass required in low Earth orbit, this figure would increase by at least a factor of seven, depending on mission architecture, requiring at least half a dozen heavy-lift launches solely for life support, and thus driving the cost and complexity of human missions to Mars beyond any reasonable limit. Recycling and possibly in situ utilization of indigenous Mars water resources are therefore critical enabling capabilities for human missions to Mars. Previous "design reference missions" assumed that high-performance life support systems would function flawlessly for the ~ 2.7 year round trip to Mars. However, life support systems developed for the International Space Station do not appear to have the longevity and reliability needed for Mars. As NASA moves forward with the current human exploration initiative, we need some means of estimating the required mass of life support system that goes beyond wild optimistic guesses. NASA's Advanced Life Support (ALS) project has been advancing the technology of recycling of water and air resources in human space missions for some time. Emphasis has been placed on recovery percentage and trace contaminant removal. Method: Mass estimates for physical plant and back-up caches are provided by NASA. A critical review was carried out based on NASA reports dealing with life support systems and these were judged in the context of "design reference missions" for humans making the round trip to Mars. Conclusion: ALS estimates of masses of life support systems are based on research and analysis, but the sources of reported performance data are not traceable to experimental data, and the reliability and lifetime of these systems is very uncertain. These estimates are optimistic, and when translated into engineering systems requiring margins, spares and fail-safe performance, are likely to increase significantly. Nevertheless, even these optimistic estimates require a significant initial mass in low Earth orbit, estimated as 210 metric tons. Life support remains at best, a significant mass, cost and risk factor for human missions to Mars, and at worst a major show stopper.