President Barack Obama has unveiled plans to end Nasa's moon programmes, turn over space transportation to commercial companies and jump-start technologies needed for future human exploration of Mars and other destinations.
The plan is part Mr Obama's budget for the fiscal year to September 30th, 2011, which was unveiled today and must be approved by the US Congress.
Nasa, which currently receives about $18 billion a year, has been working to develop a replacement for the space shuttles, which are being retired this year after five more missions to complete construction of the orbiting International Space Station, a $100 billion project of 16 countries.
Nasa currently spends more than half of its budget on human space programmes.
Mr Obama's budget ends work on the shuttle follow-on vehicle, known as Orion, as well as a pair of rockets developed to fly astronauts to the space station, the moon and other destinations in the solar system.
"We are proposing canceling the program, not delaying it," Peter Orszag, director of the Office of Management and Budget, told reporters during a conference call.
Funds previously earmarked for the Constellation programme, initially intended to return US astronauts to the moon by 2020, instead would be used for research projects that include robotics and other technologies needed to prepare for an eventual human mission to Mars, Mr Orszag added.
Nasa already has spent $9 billion on Constellation and likely would owe millions more to cancel existing contracts. Prime contractors on the Ares rocket programme include ATK Launch Systems, Pratt & Whitney Rocketdyne and Boeing. Lockheed Martin is the lead contractor on the Orion capsule.
A space advisory panel, tasked by Mr Obama with reviewing the Constellation programme, determined that without a $3 billion-a-year budget boost, it was doomed.
The board also recommended Nasa help commercial firms develop space taxis to ferry crewmembers to and from the space station, a service the United States currently is paying Russia to provide at a cost of $50 million a seat. Mr Obama apparently has decided to take its advice.
Advocates say turning over space transportation to the private sector will create more jobs per dollar because the government's investment would be leveraged by millions of dollars in private investments.
"Nasa investment in the commercial spaceflight industry is a win-win decision," Bretton Alexander, president of the Commercial Spaceflight Federation, said in a statement. "Commercial crew will create thousands of high-tech jobs in the United States, especially in Florida, while reducing the spaceflight gap and preventing us from sending billions to Russia.”
Nasa already has contacts with Space Exploration Technologies and Orbital Sciences Corp to deliver cargo to the station. SpaceX and other firms also are developing spaceships that can carry passengers to orbit and back.
Some members of Congress, anticipating the announcement to cancel Constellation, last week launched pre-emptive strikes. "I, for one, intend to stand up and fight for Nasa, and for the thousands of people who stand to lose their jobs," said Senator Bill Nelson from Florida, the base of the space shuttle programme.