President Barack Obama will scale back US space ambitions, abandoning plans to return to the moon by 2020 and confining NASA to lower orbits for years to come.
The shift will be unveiled Monday when Obama presents his 2011 budget blueprint to Congress, according to an external White House advisor.
"Constellation is dead," the advisor told AFP on Friday, referring to a program that envisioned using Earth's nearest neighbor as a base for manned expeditions to Mars.
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Under the new plan, Obama will also propose boosting the development of commercial rockets and other vehicles that can ferry US astronauts to the International Space Station (ISS).
The Constellation program was launched in 2004 by then-president George W. Bush after the Columbia space shuttle mission ended in disaster with the death of all seven crew members in 2003.
The catastrophe led the US space agency to decide it would retire its shuttle orbiter fleet by September 2010 and launch a successor program, the ultimately under-funded Orion crew exploration vehicle and Ares 1 rocket.
Financial, political support for NASA dwindles
NASA has faced growing pressure to cut its budget as the US government's debt soars and the United States buckles under the deepest economic crisis since the Great Depression of the 1930s.
The agency has also seen dwindling political support, with its White House and congressional paymasters reluctant to fund the type of expensive manned space exploration that saw the agency put 12 men on the moon.
NASA is estimated to have already spent a little over nine billion dollars on Constellation, including 3.5 billion on the Ares 1 and 3.7 billion on Orion.
Concentration to shift to commercial sector
The Obama administration plans to hike NASA's budget by 5.9 billion dollars over five years to boost commercial development, with the goal of a first commercial flight to the ISS launching by 2015, the advisor said.
In the meantime, NASA will rely on Russia's Soyuz spacecraft to ferry US astronauts to the orbiting space station after the shuttle program is retired.
Only five more shuttle flights, including an Endeavour mission scheduled for a February 7 launch, are planned.
The White House wants NASA to take on the lead innovator role it played during the 1960s with the Apollo program that put men on the moon, to help now develop a dynamic new commercial space sector.
While it may abandon for at least a decade any ambitions to fly men beyond Earth's orbit, the Obama administration also plans to boost international cooperation, noted John Logsdon, former director of the Space Policy Institute at George Washington University.
"While Constellation is dead, it does not mean human space exploration is also dead," he said, noting that NASA will work on finding a commercial solution to flying US astronauts to the ISS after September 2010.
He predicted that missions would return to the moon or to an asteroid close to Mars's moon.
But former NASA chief Michael Griffin was more pessimistic, warning that the United States would "abandon its leadership on the space frontier," ceding its place to Chinese or Russian space programs, if it halts the Constellation program.
Getting the cancellation through Congress would be "tough," Logsdon said, as lawmakers from Florida and other states with close ties to the space program would oppose moves that could threaten local jobs.
