NASA's future in space needs clarity of vision and purpose. For America's space adventure to move forward, a number of tough choices are ahead.

"To be successful, any 'vision' will have to be concrete and financially sustainable, and it will have to have broad and deep support within the Administration, Congress and the public at large. That hasn't happened for more than 30 years," Boehlert said in prepared remarks provided to SPACE.com.

While the lawmaker acknowledged that a human presence in space is valuable and should be an aspect of the nation's space program, "space science and earth science programs are a higher priority," Boehlert said. "They have more scientific benefit, expand our horizons further -- literally and figuratively -- and accomplish more at less risk and less cost than do human space flight programs," he said.

Any vision has to come with an affordable price tag, Boehlert said. Significant new missions could be accomplished with a NASA budget that ramped up to about $20 billion a year and remained at that level. Witnesses testifying before his Committee have made such estimates in the past.

"That's still a hefty increase -- 33 percent -- but it's in the range of the possible over time," Boehlert noted.

Another point raised by Boehlert is a look at existing aspects of the human spaceflight program. While backing the idea of taking on ambitious new human missions, he said indefinitely perpetuating those existing elements should not happen.

Boehlert added that the country should not commit to any new projects in human space flight until there is a better sense of what the country is trying to accomplish. That means knowing how long the shuttle and station will be in use, and of how much the nation is willing to spend over the long haul, he said.

"We need a date certain to stop flying the space shuttle and to decommission the International Space Station. Obviously, both will remain in use until the end of this decade and probably beyond. But while they're in use, we need to ensure that they are, to the greatest extent possible, contributing to our longer-range missions," the House Committee on Science Chairman said.

Boehlert also called for "a full, open and honest debate on how to proceed." NASA needs to be far more accurate in describing capabilities, risks and costs, the Congressman said. "We all need to take this opportunity to put NASA -- and the nation -- on a path that will be challenging, exciting and probing, and at the same time realistic, sustainable and productive."

That's a difficult balance, Boehlert remarked, "but it can allow a range of ambitious activities - whether those involve going to Mars or returning to the Moon or increasing the commercial exploitation of space."

"But none of that can happen without a clear-eyed appraisal of what we're accomplishing now and how we can best move into the future," Boehlert concluded.