U.S. space agency officials are facing sharp questions from U.S. lawmakers over a five-year gap in American spaceflight capabilities between the planned 2010 retirement of the space shuttle fleet and the anticipated development of a successor vehicle. VOA's Michael Bowman reports from Washington, where NASA administrators testified before Congress Thursday.

President Bush has instructed NASA to retire the primary workhorse of America's space fleet, the space shuttle, in September 2010, the target date for completing construction of the International Space Station. Years ago, it had been assumed that the United States would have a next-generation space vehicle ready to take over for the aging shuttles, which began service in 1981.

But NASA says the successor, called the Orion Crew Exploration Vehicle, will not be ready to go into service until 2015. In other words, there will be a five-year gap.

How will the United States fulfill its obligations to provide crew and cargo to the space station during that period? NASA Administrator Michael Griffin says the agency will, in effect, rent space on Russian spacecraft for transporting personnel and rely on Japanese and European vessels for ferrying cargo.

"I think our plan is very solid," said Griffin.

Not so, according to the Chairman of the Senate Subcommittee on Space and Aeronautics, Bill Nelson. The Florida senator noted that space ventures often suffer delays and unforeseen complications. He said NASA is banking on finishing the International Space Station - and retiring the space shuttle - by a specific deadline that may, in the end, have to be postponed.

"All of us know those kind of things [delays] will happen," said Nelson. "What we have is a $50 billion or $60 billion asset up there in space that has got to be tended to and has got to be built. And it may not come [be completed] by 2010."

Meanwhile, the ranking Republican on the committee, Texas Senator Kay Bailey Hutchison, expressed reservations about relying on the space capabilities of a partner - Russia - with whom the United States has had somewhat-frosty relations.

"If we are not able to go into space at all in a gap period because our relations with Russia are not such that we would be able to go up, the American people are going to wake up and say, 'What happened? What happened to the leadership of our country, to the leadership in Congress, and to the leadership in NASA that we would be in a hiatus from being able to go into space at a time when other countries are emerging and able to do it?'," said Hutchison.

At a time when China and other nations are galloping ahead with their own space programs, NASA officials say they are acutely aware of the need to maintain and strengthen America's space capabilities. Administrator Michael Griffin told the subcommittee he agrees entirely with those who say that the five-year gap in U.S. space transport ability is far from ideal.

"I do not want to leave this hearing or this committee with the impression that we are in a good position," he said. "We are not. The failure to plan for a successor to the space shuttle, and to bring it online in a timely way, was a failure of U.S. strategic planning. We are not in the position I would wish the United States to be in. We are, I think, doing the best that can be done."

Why not simply retain the space shuttle program until the Orion Crew Exploration Vehicle is ready for service? NASA says the shuttles require more than $2.5 billion a year to operate. Given NASA's fixed budget, sustaining the shuttle program beyond 2010 would rob funds from other ventures - including the very program to build the shuttle's successor.