LIMITING FACTORS

While some research areas are more severely affected than others by the changes, clearly NASA’s revision of the ISS to the Core Complete configuration has drastically reduced the overall ability of the ISS to support science. The reduction, singly or in combination, of upmass capability, research facilities and equipment, and available crew time for science activities severely limits or forecloses the scientific community’s ability to maximize the research potential of the ISS. Moreover, the absence of any overarching, well-articulated goal on which to base scientific priorities that would unify or guide the downsizing process has further exacerbated the already significantly diminished capability of the ISS. The impact on the various scientific disciplines of revising the ISS to the Core Complete configuration varies but in all cases is substantial. Although NASA’s stated goal for its ISS program is to create a world-class laboratory, it is the opinion of the task group that the actions taken with regard to crew time, equipment, facilities, and logistics make this unlikely. Specifically, the task group found the following to be the most significant factors limiting the ability of the science community to maximize the research potential of the ISS:

  • Interdisciplinary priorities not in place. Decisions to cancel or greatly delay experimental facilities and equipment vital to specific scientific disciplines were made in the absence of cross-disciplinary priorities to guide the selection process. In many cases these decisions were made based primarily on what equipment had not yet been built, without any apparent weighting of the impact on overall scientific objectives.

  • Crew time. The most widespread and significant impact of ISS design revisions on the achievement of scientific objectives stems from the more than 85 percent reduction in crew time available for scientific activities.1 This limitation has an impact on every discipline examined, ranging from a potential total elimination of the ability to achieve even a modicum of meaningful work on the ISS in the areas of radiation biology, systems physiology, crew behavior and performance, and fundamental biology, to lesser impacts on disciplines such as plant science, materials science, fundamental physics, combustion science, and fluid physics. Even these potentially less seriously affected fields will probably sustain significant negative impacts when they are forced to compete with the remaining scientific complement for the minimal time available.

  • International partner participation. ISS partners will also experience major reductions in their ability to perform science on the ISS as a result of the Core Complete design. As a result, serious questions have been raised about whether international partners will continue to support ISS development at originally planned levels. Such reductions could seriously reduce the remaining science capabilities of the ISS since the international partners are responsible for elements critical to many U.S. investigators. Loss of the Japanese experiment module exposed facility, for example, would all but eliminate research in fundamental physics.

  • Science facilities and equipment. Many U.S. experiment racks have been eliminated or delayed indefinitely in the redesign of the ISS. In addition, the modules containing the functional equipment that goes into the remaining racks have also been reduced significantly in number, worsening an already dramatically reduced capability. The scientific disciplines affected most severely by these reductions are materials science, fluid physics, fundamental biology, and muscle and bone physiology.

  • Shuttle upmass capacity. The upmass and stowage volumes for many of the experiments are expected to be severely curtailed as a result of the reduction in shuttle flights and facility changes in Core Complete, and the quantity of scientific work is expected to be reduced accordingly. In fact, the constraints of meeting ISS operational needs with only four shuttle flights per year is expected to leave

1  

Since at least 2.5 crew are needed for the maintenance of the ISS, the maximum number of crew available to perform science was 4.5 or 3.5 in Rev. F and is down to 0.5 in Core Complete.



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