HOUSTON Apollo astronauts from the first and last expedition to the Moon see far-reaching consequences rippling through Americas space program due to the loss of Columbia and its seven-person crew.

The moonwalkers urge a revamp of the human spaceflight agenda. Doing so would not only mean more robust and safer access by humans to Earth orbit, but also map out a long-term vision of where the nation should go in space.

Buzz Aldrin, Apollo 11 moonwalker, attended the first public hearing of the Columbia Accident Investigation Board, held here March 6.

Aldrin said that the key is pinpointing what caused Columbias disintegration and making the appropriate fixes. He added, however, that not finding a root cause could entail other dramatic measures.

"Its hard to conceive of standing down for that long a time, given the space station. So we may need to either have some risky shuttle flights for a limited period of time, or we are going to stand down and fly only Russian Soyuz spacecraft," Aldrin said.

Aldrin said a requirement could be that all future shuttle flights be lofted into an orbit that is compatible with that of the space station something that Columbia did not do. If an in-orbit problem arose, or need for inspection was warranted, shuttle crews would find safe-haven at the station.

Having a number of Soyuz vehicles at the ready could allow for what military strategists coin as a "surge response," Aldrin said, to quickly and safely bring down to Earth a large number of stranded astronauts.

There is one immediate problem of astronomical proportions in restricting shuttle missions to a station compatible orbit. It would curtail human servicing and eventual return of the Hubble Space Telescope that whips around Earth in a different orbit than the station.

Aldrin said that, like the on-the-pad Apollo fire in 1967 and the Challenger accident in 1986, "we have a space imperative right now. The question is how do we respond to that imperative?"

There are tough questions that need answering regarding the Columbia accident, said Harrison Schmitt, an Apollo 17 astronaut and the last man to step onto the Moon in 1972. However, the remaining orbiters in the shuttle fleet are sufficiently different from Columbia that those space planes can be technically certified for flight, in relatively short order, he told SPACE.com in a separate interview.

The Columbia catastrophe is spurring a full, independent flight readiness review of the space shuttle program. "That review has to be done because of what happened to Columbia and its crew. But it does not mean that the other three vehicles cannot be used in the national interest earlier rather than later, or not at all," Schmitt said.

"Politically and internationally, I do not think there is an option for the United States to be grounded and dependent on the Russians for space access," the retired NASA astronaut and former Senator from New Mexico warned.

Taking a longer look beyond the Columbia accident, Schmitt offered several steps to assure Americas human spaceflight gets on track.

"The continued use of the shuttle, including kits for long duration stays by many astronaut/scientists at the International Space Station, and the proper and rapid implementation of the Orbital Space Plane concept looks to me like the best path to solve our immediate political and international problem in space," Schmitt said.

Schmitt contends that work on the International Space Station (ISS) should be redefined in two ways:

-- It should become primarily a biomedical research facility, and NASA should be required to join in a true partnership with the National Institutes of Health (NIH) to use the orbiting outpost;

-- Construction and maintenance of the ISS should be re-oriented toward learning how to engineer space facilities for indefinite life rather than a finite mission life. This emphasis for ISS would make it relevant to the longer term goal of returning to the Moon to stay, as well as going onward to Mars.

A question quickly raised in the aftermath of a human spaceflight tragedy is why not utilize robots as a far better and safer alternative to human space travelers.

Schmitt, a professional geologist, draws out an answer from his own sortie on the Moon.

"The question raised about whether humans should be in space at all is an old one, usually raised by non-exploration scientists who want NASA money to go to their pet robotic projects," Schmitt said.

"I know from history and personal experience on the Moon that during exploration, humans will provide instantaneous observation, interpretation, and assimilation of the environment in which they work and a creative reaction to that environment unavailable from any other source," Schmitt said.

Schmitt emphasized that human eyes, experience, judgement, ingenuity, and manipulative capabilities "are unique in and of themselves and highly additive in synergistic and spontaneous interaction with instruments and robotic systems."

Both Schmitt and Aldrin agree that, as the nation and NASA struggles with what happened to Columbia, there is also need to better blueprint where the country is headed in the human spaceflight arena.

"Where are we going? Weve never identified where we are going once the space station is complete," Aldrin said. "There has been an absence of a vision that excites people, the public, the Congress, and the workforce. So there has been a lack of resources, attention and dedication to many things," he concluded.