The NASA transition team of President-elect Barack Obama is faced with a difficult decision on the Space Shuttle – to delay or accelerate its decommissioning.

The retiring Bush administration called the shuttle to be grounded by 2010 for reasons of budget and safety, but critics in congress and the industry say that the five-year hiatus until the Shuttle’s successor is ready would cause severe losses of program expertise as well as lower political support for manned space flights.

Lawmakers at local, state and federal levels worry about thousands of jobs being lost as shuttle operations at the Kennedy Space Center in Florida cease. Some also point to the fact that the shuttle’s quick retirement will force NASA to temporarily use Russian Soyuz craft to reach the International Space Station.

The alternative, keep using the Shuttle, is problematic as well. An internal study by the National Aeronautics and Space Administration predicts that giving an extension to the program until 2015 will incur a cost of $13 billion and increase the chances of accidents with astronauts on-board. The study, which has not yet been released, will likely be discussed at a Friday news briefing called by NASA.

Extending the program till 2012, says the report, would cost $4.5 billion dollars and would “likely pose the lowest technical, schedule and safety risks.”

NASA has declined to comment on the study’s specifics, but an agency spokeswoman said on Monday that the study’s findings must be correlated with other studies before drawing any definitive conclusions.

Members of the Obama transition-team are considering their options, which include speeding up development of Shuttle replacements, or keeping the shuttle going until 2015. Members of the team declined to comment.

The study was prepared by managers at Houston’s Johnson Space Center to advise the new administrations, and warns about the dangers of delaying the shuttle’s retirement. Continued shuttle launches to the ISS through 2015 would involve as many as 15 flights and increase the “cumulative risk” of accidents to 1 in 3.2 missions. The per-flight risks won’t increase, but overall risks involving malfunctions, space debris collisions and others increase with the number of flights. A previous NASA projected accident risk rate for the start of the next decade was roughly 1 in 8 missions.

Obama promised while a candidate to increase NASA’s budget and urged the agency to not take action that would prevent the Shuttle’s use beyond 2010

NASA’s administrator Michael Griffin has been at odds with the chief of the transition team for its questioning of the agency’s plans and assumptions. Griffin stresses there won’t be enough funding to extend the Shuttle’s flights and speed development for the Constellation replacement program at the same time. Current NASA spending plans show Constellation spending bumped to $6.5 billion from $3.3 billion in fiscal year 2011, while at the same time dropping shuttle spending by $3 billion.