Cape Canavarel, Fla. ? A debate is raging over how much longer America’s workhorse of space can struggle on.

National Aeronautics and Space Administration Administrator Michael Griffin has vowed to end the program by 2010. He is setting the space agency’s future on a next-generation shuttle, known as the Crew Exploration Vehicle, which won’t be operational before the current fleet retires.

That plan could create a gap of several years when the U.S. would not be capable of space flight, while Russia and China would continue flying.

Some scientists and congressional supporters of the shuttle say pushing the craft into retirement would be an unacceptable blow to American research and prestige.

Others caution that extending the service life of the three remaining shuttles without major investments and upgrades would raise serious safety issues.