Choosing the best approach to meet waste processing requirements for long duration space missions should be based on objective selection criteria that provide for subsystem operational availability at the lowest mission cost. Suitable criteria would include robustness, safety, and the minimization of mass, volume, power, cooling, crew time, and resupply requirements for the candidate technologies.
The best candidate technologies based on data from historical missions and preliminary data from the Solid Waste Processing and Resource Recovery Workshop (SWPRRW) have been evaluated for cost effectiveness in processing crew waste loads as defined by identified waste models. Both PC and biological approaches were considered for each of three missions: the ISS mission, a Mars transit mission, and a “concentrated exploration” mission for the Mars surface.
Results of this analysis are consistent for all three missions considered. For ISS (10-years) and Mars transit (0.49-years each way), both PC and supply based missions, the storage of waste was the most cost-effective approach. For the “concentrated exploration” mission, which assumes one plant growth chamber and a 1.64-year surface stay, storage was also the most cost-effective option, but other processes, including sterilization for planetary protection may need to be included.