Review of NASA Plans for the International Space Station (2006)

This report of the National Research Council’s (NRC’s) Space Station Panel reviews NASA plans for the completion of the International Space Station (ISS) and its utilization in support of the human exploration of the solar system. At the time this report was written, no single integrated plan for the ISS was available for the panel’s review. Instead, from the information made available to it from several recent NASA planning activities relevant to ISS utilization for the new exploration missions, the panel developed broad advice on programmatic issues that NASA is likely to face as it attempts to develop an updated utilization plan for the ISS. The panel also discussed some potentially important research and testbed activities to support exploration objectives that may have to be carried out on the ISS to be successful.

According to the information presented to the panel, the ISS today is approximately 50 percent completed. NASA plans 18 or 19 more flights to finish construction of the ISS but hopes to reduce that number. The shuttle, currently the only transportation system capable of deploying the large ISS structural components and research modules, is planned to be decommissioned at the end of 2010. The panel’s understanding is that NASA still plans to deploy all previously planned rack-level research facilities except for those associated with the centrifuge accommodation module (i.e., the life sciences glove box and animal holding racks). However, it appears that much of the racks’ supporting equipment has been eliminated in concert with the NASA research programs that would have utilized the racks. The ISS currently carries a reduced crew of two, and NASA is considering scenarios for increasing it to six in 2009 or 2015, with 2008 being the earliest date that the ISS might be capable of sustaining a crew of six.

NASA currently defines the mission objectives for the ISS in support of extended crewed exploration of space as follows:

• Develop and test technologies for exploration spacecraft systems,

• Develop techniques to maintain crew health and performance on missions beyond low Earth orbit, and

• Gain operational experience that can be applied to exploration missions.

The panel agrees that these are appropriate and necessary roles for the ISS. However, the panel noted with concern that these objectives no longer include the fundamental biological and physical research that had been a major focus of ISS planning since its inception. In addition to increasing fundamental scientific understanding, much of that research was intended to have eventual terrestrial applications in medicine and industry. Previous reports^1-3 also emphasized the importance of fundamental biological and microgravity research for the development of new technologies and the mitigation of space-induced risks to human health and performance both during and after long-term spaceflight. The loss of these programs is likely to limit or impede the development of such technologies and of physiological and psychological countermeasures, and the panel notes that once lost, neither the necessary research infrastructure nor the necessary communities of scientific investigators can survive or be easily replaced.

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 criteria^a 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.

The panel saw no evidence of an integrated resource utilization plan for use of the ISS in support of the exploration missions. Presentations that covered some elements of criteria and processes for determining priorities for utilization of the ISS for different exploration missions demonstrated poor definition of those criteria and processes. In particular, the materials presented to the panel did not seem to take into account the effects that assigning high priority to one mission would have on factors such as the ability to complete another, perhaps later mission, because of depletion of necessary resources or limitations imposed by necessary lead times.

Recommendation: NASA should develop an agency-wide, integrated utilization plan for all ISS activities as soon as possible. Such a planning effort should explicitly encompass the full development of the Exploration Systems Architecture Study technology requirements, migration of current ISS payloads to meet those requirements, identification of remaining gaps unfilled by current ISS payloads, and the R&D and technology or operations payloads needed to fill those gaps. An iterative process that includes Exploration Systems Mission Directorate stakeholders and the external scientific and technical community should be employed to ensure that the as-flown experiments closely match the integrated ISS utilization plan.

Recommendation: Scheduled periodic reviews of the ISS utilization plan with the participation of a broad group of stakeholders (internal and external, scientific and operations) are needed to ensure that the plan remains appropriate and that it continues to promote an integrated approach to attaining the ultimate program goals.

The ISS represents a unique platform for conducting enabling R&D for exploration missions, particularly a Mars mission. Enabling research was not noted as an objective of ISS support for exploration missions. The panel noted with concern this apparent gap in understanding the value of the ISS for exploration missions. Even in an era of extremely limited resources, the ISS may well represent the only timely opportunity to conduct the R&D that is necessary to solve exploration problems and reduce crew and mission risks prior to a Mars mission.

Recommendation: NASA should state that the objective for ISS utilization in support of exploration missions is to conduct enabling research for (1) technologies for exploration, (2) ways to maintain crew health and performance for missions beyond low Earth orbit, and (3) development of an operational capability for long-distance flights beyond low Earth orbit.

Recommendation: Based on the involvement of a broad base of experts and a rigorous and transparent prioritization process, NASA should develop and maintain a set of research experiments to be conducted aboard the ISS that would enable the full suite of exploration missions. These experiments should be fully integrated into the ISS utilization process.

The ISS represents a unique platform with which to conduct operations demonstrations in microgravity. For a Mars mission, where significant periods of the mission will occur in microgravity because of the long travel times en route to and returning from Mars, the ISS may prove the only facility with which to conduct critical operations demonstrations needed to reduce risks and certify advanced

systems. The panel is concerned that no evidence of definition of operations demonstrations requirements for exploration missions was shown, and such requirements do not appear to be a part of the plans for utilization of the ISS for exploration missions.

Recommendation: Using a rigorous process based on formal prioritization and involvement of the operations community, NASA should develop and maintain a set of operations demonstrations that need to be conducted on the ISS to validate operational protocols and procedures for long-duration and long-distance missions such as the ones to Mars. These demonstrations should be integrated into utilization of the ISS to support exploration.

As discussed in previous NRC and IOM reports,^5-9 no three-person crew (let alone the current two-person crew) will have time to do the necessary research and testing, nor will they be able to serve for human experimentation. Six astronauts will be needed to devote adequate time and effort to the research and testing essential for human missions to Mars and beyond.

Recommendation: NASA should give top priority to restoring the crew size of the ISS to at least six members at the earliest possible time, preferably by 2008.

Given that shuttle flights are being delayed and that no future shuttle flight schedule is certain, it is possible that the planned ISS configuration will not have been completed by 2010, putting the ISS contribution to exploration research at risk. It appears that there are no plans to provide a backup alternative for delivering ISS structural components and research modules if the shuttle does not complete this process by 2010.

Recommendation: NASA should plan options and decision points for obtaining a post-shuttle logistics capability for maintaining the ISS facility, for supporting the flight crew and research, and for demonstrating the technology and operations that will enable exploration missions. NASA should establish priorities and develop back-up plans to enable the post-2010 deployment of large ISS structural components and the research facilities required to accomplish exploration mission objectives.

1. Institute of Medicine (IOM). 2001. Safe Passage: Astronaut Care for Exploration Missions. National Academy Press, Washington, D.C.

2. National Research Council (NRC). 1998. A Strategy for Research in Space Biology and Medicine in the New Century. National Academy Press, Washington, D.C.

3. NRC. 2003. Assessment of Directions in Microgravity and Physical Sciences Research at NASA. The National Academies Press, Washington, D.C.

4. IOM and NRC. 2006. A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap. The National Academies Press, Washington, D.C.

5. NRC. 2003. Factors Affecting the Utilization of the International Space Station for Research in the Biological and Physical Sciences. The National Academies Press, Washington, D.C.

6. NRC. 1998. A Strategy for Research in Space Biology and Medicine in the New Century.

7. NRC. 2000. Review of NASA’s Biomedical Research Program. National Academy Press, Washington, D.C.

8. IOM. 2001. Safe Passage: Astronaut Care for Exploration Missions.

9. IOM and NRC. 2006. A Risk Reduction Strategy for Human Exploration of Space.