The GAO went on to say after the planned retirement of the space shuttle in 2010, NASA will face a cargo resupply shortfall for the International Space Station of approximately 40 metric tons between 2010 and 2015. Specifically, NASA estimates that it will need a total of 82.7 metric tons of dry cargo delivered to the ISS between 2010 and 2015 to meet crew needs and to support maintenance and scientific experiments.

Commercial partners' vehicles will transport almost half of this cargo and are scheduled to fly more cargo delivery missions than the space shuttle and international partners' vehicles combined-including 14 of the last 19 missions. Delays in the availability of commercial vehicles to fill the cargo resupply gap would result in diminished usage of the space station, the GAO stated.

The ISS program office has identified the approximately 88,000 pound cargo resupply shortfall as a top program risk, and its risk summary report states that a delay in 2010 in the availability of commercial partners' vehicles would lead to a significant scaling back of NASA's use of the space station for scientific research. If there were a delay in 2011, NASA could no longer maintain a space station crew of six astronauts and its ability to conduct scientific research would be compromised, the GAO found.

Space development programs are by nature complex and rife with technical obstacles that can easily result in development delays. In our recent report on selected large-scale NASA projects, we found that 10 of the 13 projects that we reviewed had experienced significant cost and/or schedule growth from their project baselines. Commercial partners must develop and demonstrate new launch and space vehicles, launch and mission operations capabilities, and achieve integration with the space station in a 3- to 4-year period, the GAO stated.

While the challenges are obviously difficult, there are some who see the commercialization of