Future of the Shuttle is still "up in the air" ... final destination will be a series of museums and a couple of Billioneers.

President-elect Barack Obama's NASA transition team faces a tough early choice between extending the life of the aging space shuttle and accelerating its replacement.

Bush-administration plans call for grounding the shuttle by 2010 for budget and safety reasons. But congressional and industry critics worry that the expected five-year gap before the shuttle's replacement is prepared to blast off would lead to a crippling loss of program expertise and sap political support for manned space flights.

Federal, state and local lawmakers are distressed about losing thousands of jobs now associated with shuttle operations at the Kennedy Space Center in Florida. Some also point out that speedy retirement of the shuttle will force NASA to temporarily rely on Russian launches to reach the International Space Station.

Keeping the Shuttle flying is not without risks, however. An internal National Aeronautics and Space Administration study projects that extending the program until 2015 would cost up to an additional $13 billion and could increase the chances of accidents with astronauts aboard. Findings of the study, which has not yet been released, are likely to be discussed during a NASA news briefing on Wednesday.

Stretching Shuttle operations through 2012, according to the report, would cost an extra $4.5 billion and "likely pose the lowest technical, schedule and safety risks."

NASA officials have declined to comment on specifics of the study, but on Monday an agency spokeswoman said its findings "will have to be integrated with other studies" before definitive conclusions are reached.

Obama transition-team members are weighing various options, including speeding up development of follow-on systems and keeping the shuttle flying through 2015. Transition-team members declined to comment.

The study, prepared by managers at the Johnson Space Center in Houston to help guide the incoming administration, stresses the perils involved in delaying retirement of the shuttle. Continuing shuttle launches to the International Space Station through 2015 would add as many as 15 flights and raise the "cumulative risk" of an accident to "1 in 3.2" missions, the study says.

While the risks for a particular flight won't increase, according to the study, overall risks of malfunctions, collisions with space debris and other problems increase with the number of flights. NASA previously projected the accident risk through the beginning of the next decade as roughly one in eight missions.

As a candidate, Mr. Obama proposed beefing up NASA's budget and joined other lawmakers in urging the agency to avoid any action that would preclude extending shuttle operations past 2010.

NASA Administrator Michael Griffin has clashed with the head of the Obama transition team over its sweeping questions about the agency's current plans and assumptions. Mr. Griffin has maintained that there won't be enough funding to simultaneously extend shuttle flights to 2015 while ramping up funding for the replacement program, dubbed Constellation. Current agency spending blueprints show Constellation spending jumping to roughly $6.5 billion from $3.3 billion in fiscal 2011, the same year that spending on the shuttle is slated to decline by a corresponding $3 billion.

Mr. Griffin is expected to meet with NASA managers this week to consider speeding up work on the shuttle craft's proposed replacement, a manned spacecraft dubbed Orion, along with associated rockets. On Wednesday the agency is expected to discuss tentative plans to spend more than $2 billion to accelerate flight tests and engine development. Such efforts could lead to Orion's first manned flights in 2014, a year ahead of the current schedule, according to agency and industry officials. Partly because of previous congressional cuts, current timetables to fly the Orion vehicle are a year behind the schedule established in early 2007.

Another possible shuttle alternative, which is strongly opposed by current NASA management, envisions using existing military rockets for propulsion. Proponents contend they would be more reliable and could be developed more quickly.