The U.S. human spaceflight program is "strained to the limit," NASA's chief said Thursday, warning against any long gap between the end of the shuttle era and the first flight of a planned new spaceship.
"The United States risks both a real and a perceived loss of leadership on the world stage if we are unable to launch our own astronauts into space for an extended period of time when other nations possess their own capabilities to do so," NASA Administrator Michael Griffin told a congressional committee.
Griffin acknowledged that NASA already expects a gap between the shuttle's planned retirement in 2010 and the start-up of a new crew exploration vehicle in 2013 or 2014.
But he said extending this gap would over-stress an already stretched program.
"Our human spaceflight program is not an optional program," Griffin told members of the House Science Committee. "We are already strained to the limit."
Griffin fielded pointed but largely sympathetic questions about the Bush administration's $16.8 billion budget request for NASA for fiscal 2007.
"I am extremely uneasy about this budget," Rep. Sherwood Boehlert, a New York Republican who chairs the committee, told Griffin. "This budget is bad for space science, worse for Earth science and possibly worse for aeronautics."
A large slice of the U.S. space agency's resources are focused on achieving President Bush's ambitious plan to return U.S. astronauts to the moon by 2020 and eventually send humans to Mars.
But before that can happen, NASA must satisfy its commitments to finish building the orbiting International Space Station by 2010, and that cannot occur without a working space shuttle fleet.
The shuttles have been grounded — except for one shakedown flight last year — since the fatal Feb. 1, 2003, break-up of Columbia. The next shuttle flight, considered a test of safety improvements, is tentatively set for May.
The U.S. mission to send humans back to the moon for the first time since 1972 will not occur until 2018, Griffin said, barring any unforeseen program delays. He warned that any further slips in this schedule would risk a loss of critical expertise at NASA.
If there is an extended hiatus between the end of the shuttle program and the start-up of the crew exploration vehicle, Griffin said the space agency could permanently lose its key staff.
"Then when we choose to resume human spaceflight at a later date, we will have to retrain this cadre of people, create new subcontractors," he said. "We will resume our progress in a very stumbling and halting way."
He declined to give a cost estimate for NASA's human mission to Mars.
"If we were sitting here today with the capabilities that this nation had purchased as of the end of the Apollo program, we could go to Mars within a decade," Griffin said. "We have decades worth of hard work in front of us just to be able to get back to where we were. And then Mars will be the decade after that."
