The future research productivity of the International Space Station (ISS) rests on the delayed startup of U.S. commercial resupply missions within the next year, experts from NASA and the agency’s oversight panels told the House Science, Space and Technology Committee March 28.

The transition from space shuttle resupply to private cargo providers that began with NASA’s six-year-old Commercial Orbital Transportation Services (COTS) initiative must be in full swing by mid-2013 if the space agency is to avoid research and possible staffing reductions aboard the six-person orbiting science laboratory, according to testimony from representatives of the Government Accountability Office (GAO) and a NASA Advisory Council (NAC) task force.

The U.S.-led, 15-nation ISS partnership is committed to station operations through 2020.

Even the short-term projection assumes the success of scheduled unmanned cargo deliveries by the European Space Agency’s Automated Transfer Vehicle, Japan’s H-II Transfer Vehicle and Russia’s Progress, which experienced a launch failure last August.

“If you have delays that extend into 2013 and beyond, you will see a lot of impacts on the space station and scaling back of research,” Cristina Chaplain, GAO’s director for acquisition and sourcing management, told the House panel.

Under current scheduling, NASA anticipates up to five test and delivery missions by the agency’s two COTS partners, SpaceX and Orbital Sciences Corp., by year’s end. They start with the April 30 launch of the SpaceX demonstration mission that includes plans for an early May station docking and a small cargo delivery.

A half-dozen additional Progress, ATV and HTV flights are slated for the remainder of 2012 as well, including Europe’s anticipated ATV-3 arrival at the station late March 28.

Much is at stake, as the U.S. space station partnership turns its focus from the station’s assembly, which drew to a close in mid-2011, to research and technology demonstrations.

“We are starting to begin serious use of the ISS,” said William Gerstenmaier, associate administrator for human exploration and space operations, who told the panel he anticipates at least one or two successful commercial cargo deliveries this year.

“Ultimately if we don’t get the cargo in the time frame we need, we will need to cut back on research first and then ultimately go to the survival mode,” he said. As few as two astronauts could maintain the station.

“In the near term, NASA’s plans are adequate,” testified Thomas Stafford, the former Apollo astronaut who chairs the NAC’s ISS Operational Readiness Task Force. However, he cautioned that the COTS initiative has been plagued by chronic overoptimism and remains vulnerable to lapses in management and contractor oversight.OVERSIGHT??

“Beyond the mid part of 2013, NASA becomes increasingly dependent for its projected flow of spare parts and resupply needs on the planned fleet of cargo vehicles,” Stafford said.

He credited NASA with the foresight to equip the space station with critical spare parts, food and research gear on its final shuttle missions, STS-134 and STS-135, in May and July 2011.

“Without those two shuttle missions, right now we would be in a serious situation and probably be considering how we could de-crew the space station,” Stafford told the panel.

As the station construction period drew to a close, the ISS partners counted 1,250 science investigations over the 13-year assembly period. Since October 2011, the count has grown by 259 investigations, reflecting the shift in priorities.

“While we talk about the promise offered by the ISS for enabling future space exploration as well as carrying out research that can benefit life on Earth, the fulfillment of that promise is not assured,” said Rep. Eddie Bernice Johnson (Texas), the panel’s ranking Democrat. “In reality, the ISS is a perishable commodity. The future of the ISS is really now.”