Future human space exploration missions present significant challenges for life support system (LSS) development. These life support systems will require incorporation of regenerative technologies to reduce or eliminate expendables and be low risk, demonstrating high reliability and long-term performance capability. A regenerative LSS for Space Station is a key step toward meeting these future space exploration requirements.
In the development of the Space Station regenerative LSS, the challenges have been both technical and budgetary. Currently, the International Space Station Alpha (ISSA) program will consist of three Phases. Phase I will be MIR/Shuttle Orbiter flights with United States (US) crews attending to the various US flight experiments on-board the MIR. Phase II will consist mostly of Russian launched modules and the United States (US) Laboratory module. Phase III will launch the US Habitat module to implement US regenerative LSS. Phase II will rely on Russian regenerative systems and Phase III will add Water Recovery Management (WRM) system closure in 2001 and Air Revitalization (AR) system partial closure in 2002.
Future human space exploration budgetary realities suggest that step-wise evolution of Space Station LSS technologies is the most prudent approach to achieve a successful regenerative LSS, rather than embarking on totally new regenerative LSS technologies development. Space Station regenerative LSS implementation will provide experience for reducing logistics, validating low-gravity hardware operation, extending component life, evaluating reduced-gravity fluid mechanics, understanding system integration issues and improving system efficiencies. The resulting LSS can also be key to evolving to an integrated physical/chemical/biological life support system to achieve more efficient closure. Additionally, regenerative LSS evolution is synergistic with Space Station LSS logistics reduction and reliability improvement objectives.
NASA is currently implementing a comprehensive technology development strategic plan to advance regenerative LSS technology. It is suggested that this plan incorporate a step-wise evolution using the Space Station regenerative LSS as the baseline for this evolution. For example, the selected Space Station regenerative WRM system has a low technology risk design, but this design has a significant logistics penalty for filter and sorbent bed replacement. Technology advancements to reduce or eliminate expendables by developing technology for regenerating sorbent beds and filters are possible. Complimenting these near-term improvements should be regenerative hardware evolution that includes development of solid waste recovery technology providing complete system closure by recovering metabolic and processor byproducts and food wastes. Both physical/chemical and biological processes are the candidates for this evolutionary step.
This paper provides a brief discussion of the Space Station regenerative closed-loop LSS development history, including the ISSA configuration, and a preview of NASA's overall life sciences research technology development strategic plan as it relates to regenerative life support.