NASA hopes to use commercial vehicles to match the cost of flying astronauts to the International Space Station on Russian Soyuz vehicles or to do slightly better. But even if U.S.-built commercial vehicles are ready to fly crews in 2016 as planned, the agency probably will need a longer exemption on the law that otherwise would keep it from doing business with Moscow.

William Gerstenmaier, associate administrator for human exploration and operations, told the House Science Committee Wednesday that if the agency gets the $850 million it has requested for commercial crew development in fiscal 2012, and if the companies developing commercial crew vehicles can deliver on their promises, NASA won’t need to buy any more Soyuz seats to get U.S., European, Japanese and Canadian astronauts to the ISS.

“We’ve purchased all the things that we can up to the period where we will need an exception to the Iran, North Korea, Syria Non-proliferation Act if we’re going to do any additional purchases,” he said. “At this time I think it’s too early to say exactly whether we’re going to make those purchases or not with Russia. We need to start into this program, see what funding levels we get, see how good a progress these commercial companies can make … We think we need an exemption for that even for basic sustaining engineering for [the] space station, independent of transportation.”

Gerstenmaier said NASA is working with the White House on any future exemptions to the Non-proliferation Act, and is hopeful that it will be able to begin using commercial services even before the exemption expires in June 2016. Companies developing crew vehicles under the second round of the agency’s Commercial Crew Development (CCDev-2) program told skeptical committee members they would be able to fly within three years and begin routine operations in 2016.

“I have yet to be convinced that there is a sufficient commercial market that will sustain multiple, private, for-profit commercial companies through the duration of America’s commitment to the International Space Station,” said Rep. Ralph Hall (R-Texas), the science panel’s chairman, in remarks that reflected broad wariness of the commercial-crew concept among committee members. “NASA seemingly takes the position of ‘build it and they will come;’ that by starting these companies first, business will soon follow.”

At least two companies developing vehicles with CCDev-2 and their own funding – Boeing and Sierra Nevada – said their business plans close with only the two flights per year to the ISS that NASA will need to rotate six crewmembers. Other potential sources of revenue, such as additional flights to the ISS funded by nations unable to afford their own spaceflight infrastructure, and to the inflatable commercial habitats proposed by Bigelow Aerospace, would be an additional source of income, according to John Elbon, Boeing’s vice president and general manager for space exploration.

Elon Musk, CEO of Space Exploration Technologies, Inc., whose SpaceX Falcon 9 is likely early next year to become the first commercial vehicle to reach the station, said he would personally guarantee a crew-delivery cost of $140 million per flight with seven crewmembers on board.

Other companies testifying were United Launch Alliance, which is using its own funds to develop a failure-warning system for its Atlas V that would trigger spacecraft abort systems on vehicles supplies by Boeing, Sierra Nevada and Blue Origin, and ATK, which has teamed with Europe’s EADS Astrium on the proposed Liberty launch vehicle for crew missions. That vehicle would marry an Ariane V upper stage with the five-segment solid-fuel first stage that ATK developed for the terminated Ares I crew launch vehicle.

Gerstenmaier said if NASA’s appropriation for commercial crew vehicles comes in below the requested $850 million, the agency does not believe the commercial companies will be able to deliver transportation services to the ISS in 2016, which will necessitate additional Soyuz-seat purchases. To hold down costs, the agency wants to see at least two vehicles through to preserve competition in the operational phase, a hope complicated by the companies’ desire to have some government indemnification for third-party damages in case of a failure.

“It seems to me we’re running on a course of eventually the taxpayers subsidizing a monopoly, and my worry about that is that in subsidizing a monopoly we will end up footing an even bigger bill than we can anticipate in the beginning because there will be no other horse in the race,” warned Rep. Donna Edwards (D-Md.).