Although it seems unlikely that the ISS will have to play a critical research role in support of lunar sorties (because of their short duration and capability for rapid return), the panel concluded that the ISS provides an essential platform for research and technology testing in support of long-term human exploration, including lunar outpost missions and, most especially, the human exploration of Mars. Indeed, it is uncertain whether the risks involved in sending humans on long-term exploration missions can be mitigated to acceptable levels without precursor experimentation and testing aboard the ISS. Understanding cumulative biological and psychological effects in long-term space environments and the impact of microgravity on the physical phenomena on which spacecraft systems depend, as well as long-term verification of hardware and biological countermeasures and life-cycle testing, will all require the ISS as the only capability available to allow tended experiments in a free-fall environment for periods of time that approximate the duration of a Mars outpost mission.
Given the lack of a single defined research plan for the ISS, the panel could not verify that specific areas it had identified as critical to exploration were in fact gaps in NASA’s current planning. A number of broad areas of research important to exploration have been identified in past studies, and this report discusses several of these as examples of research and testing that may prove critical to fulfilling NASA exploration goals. As described in the report, these priority areas of research on the ISS include:
Effects of radiation on biological systems,
Loss of bone and muscle mass during spaceflight,
Psychosocial and behavioral risks of long-term space missions,
Individual variability in mitigating a medical/biological risk,
Fire safety aboard spacecraft, and
Multiphase flow and heat transfer issues in space technology operations.
This list is by no means comprehensive and includes at least some areas that have been considered, if not necessarily implemented, in one more of the NASA ISS planning studies reviewed by the panel.
The panel noted that risk-based criteriaa are conspicuously missing from the decision support tools presented to the panel. This weakness is particularly troubling in light of the need to prioritize what work can and must be done with respect to time limitations and other resource limitations such as cost, crew time, and so forth.
Recommendation: As has been discussed elsewhere,4 the characterization of risk should be clearly communicated, along with concrete go/no-go criteria for missions, so as to achieve a rational and supportable allocation of ISS resources.