After months of debate, NASA has settled on plans for its next spaceship — a space shuttle hybrid that will fly twice in the next decade and cost $30 billion through 2021, according to senior administration officials and internal NASA documents.

That NASA decided to recycle elements of the shuttle is not unexpected. Last year, Congress and the White House agreed NASA should reuse equipment from old programs and the new design — which includes a giant fuel tank and two booster rockets — largely reflects that compromise. The most noticeable change is the plane-like orbiter will be replaced by an Apollo-like crew capsule atop the tank.

What is surprising — and potentially controversial — is the cost and scope of the new mission, especially since NASA largely is relying on 30-year-old technology to build the new rocket.

As scheduled, NASA will fly an unmanned test flight in 2017 and a crewed mission in 2021. If NASA stays on budget, which is far from certain given NASA's history of cost overruns, each mission would cost about $15 billion apiece, although planned missions after 2021 would reduce that average price tag.

Related NASA documents show there would be a flight every year or two after 2021.

Unknown, however, is the destination. A senior administration official, who was not authorized to speak on the record, said NASA had not picked where it planned to send either the unmanned capsule in 2017 or the crewed capsule in 2021.

Previously, administration sources had hinted the missions would loop around the moon — but not land — but the official said a moon shot was not set in stone.

The only certain goal, said the official, is that NASA still would be committed to meeting President Barack Obama's target of launching a manned mission to an asteroid by 2025.

"We have to fine-tune the system before we go off to the asteroids," said the official, who described the first two launches as test flights. "This machine and this effort will enable us to get to deep space and beyond where we have been before."

But to even get to that point, NASA must first survive a tough fiscal environment. Congress is intent on cutting the federal budget and Obama has asked agencies to submit 2013 budget requests that are 10 percent below their 2011 levels — essentially a $1.85 billion cut to NASA.

At $3 billion a year, the new spaceship could fit within a reduced NASA budget, but future cost overruns likely would mean NASA would have to cannibalize other programs to pay for it. The Congressional Budget Office previously has found that NASA cost overruns of 50 percent or more are commonplace.

Much of the new spacecraft won't be up for competition, either. NASA already has settled on a crew capsule built by Lockheed Martin. And the twin boosters for the new rocket, at least initially, would be the same shuttle boosters built by Alliant Techsystems of Minnesota.

NASA intends to hold a competition in the years ahead for the boosters. The administration official said NASA definitely would use the ATK boosters for the 2017 launch but that it could have the competition complete in time for new boosters in 2021.

That decision follows intense lobbying from the Senate earlier this year. Lawmakers from California and Alabama pushed NASA to compete the boosters, largely because they represent aerospace companies Aerojet of California and Teledyne Brown Engineering of Alabama — a team that together is expected to compete for the booster contract.

More broadly, Congress and the White House have feuded for months over the new rocket. This summer, Sens. Bill Nelson, D-Florida, and Kay Bailey Hutchison, R-Texas, accused the administration of stalling the rollout of the rocket they championed in a NASA law passed last year.

In a release, Nelson hailed the new rocket as "the most powerful history," noting that the first version will be able to lift 140,000 pounds into orbit – nearly triple the 50,000-pound capacity of the space shuttle.

"This is perhaps the biggest thing for space exploration in decades," Nelson said. "The goal is to fly humans safely beyond low-Earth orbit and deep into outer space where we can not only survive, but one day also live."

mkmatthews@tribune.com or 202-824-8222.