WASHINGTON (Reuters) -- NASA trumpeted five years of human flight on the international space station on Thursday, at a time when U.S. astronauts need Russian vehicles to get there and space agency finances are under fire for mismanagement.Former residents of the orbiting outpost gathered at NASA's Johnson Space Center in Houston to reminisce about their voyages in a televised briefing featuring video clips of weightless space voyagers caroming around with such props as bite-size candies, a guitar and Hawaiian shirts.The first station crew arrived at the complex on November 2, 2000. Ed Lu, a member of the first two-person crew to travel to the station after the fatal disintegration of space shuttle Columbia in 2003, described his impressions."We closed the hatch ... Yuri (Malenchenko, Lu's Russian crewmate) and I looked at each other and said to each other, 'What have we gotten ourselves into? You're stuck with me and I'm stuck with you for the next six months. I hope this goes well,'" Lu said. "As it turned out, it went extremely well. It went by much faster than I ever thought it would go."The cost of the ISS, including its development, assembly and operation, could well exceed $100 billion, shared between the participating nations.Only one shuttle has traveled to the station since the Columbia accident, which killed all seven shuttle crew members. With the shuttle fleet grounded until at least May 2006, Lu and Malenchenko were ferried aloft by a Russian Soyuz space taxi, currently the only mode of human transport to the station.Both houses of the U.S. Congress had to pass legislation to ensure that Americans will continue to have a ride aboard Soyuz until 2011, because of the Iran Nonproliferation Act, which bars the U.S. use of most Russian space technology as long as Russia exports nuclear and missile technology to Iran.President George W. Bush is expected to sign a waiver to the act that allows astronaut travel to the station aboard Russian space ships. The waiver would cover astronauts until the shuttles are phased out in 2010 after the completion of the space station.First envisioned in the 1980s, the 16-nation project has been repeatedly scaled down as costs rose. At this point, NASA figures it will take 18 shuttle flights -- down from 28 -- to complete construction. No station construction flights will occur until after next May's mission, while NASA tackles a persistent problem with falling debris on liftoff.The U.S. space agency must deal with physical challenges, including unexpected delays prompted by recent hurricanes, but it also must get its finances in order.A report issued on Thursday by Congress' General Accountability Office found a long-term high risk for waste, fraud and abuse at NASA, largely due to the lack of reliable information on how much it spends on contractors and how well the contractors perform.In 2003, NASA's independent auditors found the agency could not reconcile a $1.7 billion difference between what NASA thought it had and what was actually in its balance in the U.S. Treasury.That difference was whittled to $46.6 million by the end of September, according to Gwendolyn Sykes, the space agency's chief financial officer, in testimony at a congressional hearing on NASA's finances."The testimony we've heard has been depressing, totally depressing," said Rep. Dana Rohrabacher, a California Republican. "NASA has an image of overcoming challenges that are preventing humankind from going into space. It seems that NASA has been unable to overcome the challenge of good financial record-keeping."Copyright 2005 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.