The International Space Station program has three key goals: (1) maintain a permanent human presence in space, (2) conduct world-class research in space, and (3) enhance international cooperation and U.S. leadership through international development and operations of the space station. Each of the partners is to provide hardware and crew, and each is expected to share operating costs and use of the station. On-orbit assembly of the space station began in November 1998 and, since October 2000, two to three crew members, who maintain and operate the station and conduct hands-on scientific research, have permanently occupied the space station. The space station is composed of numerous modules, including solar arrays for generating electricity, remote manipulator systems, and research facilities. The station is being designed as a laboratory in space for conducting experiments in near-zero gravity. Life sciences research on how humans adapt to long durations in space, biomedical research, and materials-processing research on new materials or processes are under way or planned. In addition, the station will be used for various earth observation activities. Figure 1 shows the International Space Station on-orbit. Since its inception, the station program has been plagued with cost and schedule overruns. When the space station’s current design was approved in 1993, NASA estimated that its cost would be $17.4 billion. By 1998, that estimate had increased to $26.4 billion. In January 2001, NASA announced that an additional $4 billion in funding over a 5-year period would be required to complete the station’s assembly and sustain its operations. By May 2001, that estimated cost growth increased to $4.8 billion. Since fiscal year 1985, the Congress has appropriated about $32 billion for the program. In an effort to control space station costs, the administration announced in its February 2001 Budget Blueprint, that it would cancel or defer some hardware and limit construction of the space station at a stage the administration calls “core complete.” The administration said that enhancements to the station might be possible if NASA demonstrates improved cost-estimating and program management, but the administration is only committed to the completion of the core complete configuration. In July 2001, the NASA Administrator appointed an independent International Space Station Management and Cost Evaluation Task Force to assess the financial management of the station program and make recommendations to get costs under control. The task force published its report in November 2001 and recommended that the program (1) extend crew rotations from 4 to 6 months and reduce the number of shuttle flights to 4 per year; (2) consolidate the number of contracts and reduce government staff in station operations and sustaining engineering; (3) establish an Associate Administrator for space station at NASA Headquarters, with total responsibility for engineering and research; and (4) prioritize research to maximize limited resources. NASA implemented most of the recommendations, and the task force reported in December 2002 that significant progress had been made in nearly all aspects of the program, including establishing a new management structure and strategy, program planning and performance monitoring processes, and metrics. NASA was postured to see results of this progress and to verify the sufficiency of its fiscal year 2003 budget to provide for the core complete version of the station when the Columbia accident occurred. In response to the task force’s recommendations, the Office of Management and Budget (OMB) imposed a 2-year “probation” period on NASA to provide time to reestablish the space station program’s credibility. Activities that are to take place during this period include establishing a technical baseline and a life-cycle cost estimate for the remainder of the program, prioritizing the core complete science program, and reaching agreement with the international partners on the station’s final configuration and capabilities. OMB, with input from NASA, is developing criteria that are to be used for measuring progress toward achieving a credible program. NASA provided its input to OMB in June 2003, but as of August 2003, OMB and NASA had not reached agreement on the success criteria. The grounding of the U.S. shuttle fleet has presented a number of operational challenges for the space station program. With the fleet grounded, NASA is heavily dependent on its international partners— especially Russia—for operations and logistics support for the space station. However, due to the limited payload capacity of the Russian space vehicles, on-orbit assembly has been halted. The program’s priority has shifted from station construction to maintenance and safety, but these areas have also presented significant challenges and could further delay assembly of the core complete configuration. While some on-board research is planned, it will be curtailed by the limited payload capacity of the Russian vehicles. The space shuttle fleet has been the primary means to launch key hardware to the station because of the shuttle’s greater payload capacity. At about 36,000 pounds, the shuttle’s payload capacity is roughly 7 times that of Russia’s Progress vehicle and almost 35 times the payload capacity of its Soyuz vehicle. With the shuttle fleet grounded, current space station operations are solely dependent on the Soyuz and Progress vehicles.Because the Soyuz and Progress vehicles’ payloads are significantly less than that of the U.S. shuttle fleet, operations are generally limited to transporting crew, food, potable water, and other items, as well as providing propellant resupply and reboosting the station to higher orbits. On-orbit assembly of the station has effectively ceased. Maintaining the readiness of ready-to-launch space station components has also presented a number of operational challenges, as in the following examples: A logistics module, which carries research facilities and life support items to the station, that was scheduled and ready for launch in March 2003 had to be opened and unpacked (see fig. 2). Several racks were removed to provide the proper preventative maintenance of the contents until they can be rescheduled on a future flight. In addition, crew-specific items had to be removed in anticipation of crew changes for the next shuttle flight. This module requires more than 2 months to be repacked and tested prior to launch. One of the solar array wings scheduled for launch in May 2003 was approaching its 45-month prelaunch storage limit. Due to the launch delay, the wing had to be removed from the truss section and replaced with a new wing (see fig. 3). The removed wing was shipped to the contractor for deployment testing, which NASA hoped would result in a lengthening of the prelaunch storage limit to at least 60 months. However, according to NASA officials, preliminary results were very positive, and the storage life certification could be extended to as much as 8 years or more. The performance of the batteries on the truss sections that were ready for launch has also raised concerns. Prolonged storage at ambient temperatures could shorten the overall life of the battery. According to NASA officials, a process has been developed to charge the batteries periodically without removing them from the trusses during storage, then to provide a charge capability on the launch pad just prior to launch. This process, however, will require a new device to be developed and expending resources not previously planned for this function. Station program managers are resolved to meet these challenges and have station components ready for flight when the next shuttle is ready for launch. In addition, NASA is using this longer storage time to determine the feasibility of adding new testing procedures. For example, NASA is developing tests to apply power to some elements and may also perform additional leak tests. The grounding of the shuttle fleet has also hampered NASA’s ability to correct known safety concerns on-board the station. For example, NASA has had to delay plans to fly additional shielding to the space station to adequately protect the on-orbit Russian Service Module from space debris. NASA’s analysis of the problem shows the probability of orbital space debris penetrating the module increases by 1.6 percent each year the shielding is not installed. NASA accepted this risk by issuing a waiver for the noncompliance with a safety requirement, but planned to have the shielding installed within 37 months of the module’s launch in July 2000. Six of the required 23 panels have been installed on the module, and NASA is negotiating with the Russian Aviation and Space Agency to manufacture the 17 remaining panels. NASA officials told us that they are studying alternatives for launching and installing the debris protection panels earlier than originally planned. In addition, there will be delays in analyzing the failure of an on-orbit gyro—one of four that maintain the station’s orbital stability and control. According to NASA, a shuttle flight planned for March of this year was to carry a replacement gyro to the station and return the failed unit for detailed analysis. Because the shuttle flight was canceled, the failed unit was not returned. Consequently, NASA is unable at this time to provide a definitive analysis of the reasons for the failure of the unit or to know if the problem applies to the remaining units. NASA had planned to assemble the core complete configuration of the station by February 2004. NASA officials have maintained that assembly delays will be at least a “month for month” slip from the previous schedule, depending on the frequency of flights when the shuttles resume operations. At best, then, the core complete configuration would not be assembled before sometime in fiscal year 2005. While the space station crew’s current responsibility is primarily to perform routine maintenance, the two-crew members will conduct some research on-board the station. An interim space station research plan developed by NASA details the amount and type of research that will be conducted. Further, NASA states that although the crew has been reduced from three to two members, more crew time will be available to carry out research tasks because no assembly or space walks are planned. Regardless, the limited payload capability of the Russian vehicles directly affects the extent of research that can be conducted, as illustrated in the following examples: Outfitting of U.S. research facilities halted: Lacking the shuttle fleet’s greater lift capability, the amount of research hardware transported to and from the station has been significantly limited.