The committee deliberating America's future in human spaceflight is beginning to narrow down an expansive list of alternatives to be presented to the White House at the end of this month.

File photo of Norman Augustine, chairman of the Review of U.S. Human Space Flight Plans Committee. Credit: NASA

The panel discussed a preliminary list of seven paths for the space program, which included conservative, affordable scenarios and ambitious options that would put astronauts on Mars.

Edward Crawley, a committee member and MIT professor of engineering, presented the tentative alternatives at a public hearing Wednesday in Washington, D.C.

But it was clear the list will be refined in the coming days and weeks. Others on the panel expressed concern with the options and proposed other choices during questioning.

The options were divided into two groups. Three paths would fit inside the projected $80 billion budget between 2010 and 2020. Four more alternatives would not be covered by NASA's funding forecasts in President Obama's fiscal year 2010 budget.

"We intend to look at it both ways, constrained by the budget and not constrained by the budget," Crawley said.

Part of Wednesday's discussions centered on how much money NASA can reasonably expect to execute the plans.

"There's no sense in proposing things that are dead on arrival," said Norman Augustine, the review board's chairman.

The less costly options included stretching out NASA's Constellation program to a more manageable pace, focusing on the International Space Station and deferring exploration, or giving up the agency's work in low Earth orbit and immediately starting a program to "dash out of LEO."

The first two scenarios, continuing with the Constellation and station programs, were the only choices presented that included the Ares 1 rocket.

Four other options would likely be more expensive.

NASA could extend the space shuttle program beyond its scheduled retirement in 2010 or 2011. That decision is practical only if the Ares 1 and Ares 5 architecture is abandoned in favor of a future shuttle-derived system.

"There are many things that have to work together to make this option make sense," Crawley said.

Three more alternatives would take astronauts on deep space missions to nearby asteroids, the lunar surface, or Mars.

Crawley outlined eight decision points that will guide the committee and President Obama:

• What is the fate of the space shuttle?
• What should be done with the space station?
• How much heavy-lift capacity is needed?
• Should the next government launch system be based on the shuttle or expendable rockets?
• How should crew be carried to low Earth orbit?
• What should be the plan for in-space refueling and depoting?
• What is the first destination for exploration?
• What is the role for commercial entities?

Augustine, a former aerospace industry executive, stressed the importance of a heavy-lift vehicle as the hearing adjourned.

"Don't skimp on the heavy-lift part," Augustine said. "I think as we go through our recommendations here, that's one of the things we want to keep in mind."

The board will spend another week evaluating the alternatives and their costs before convening another public hearing next Wednesday.

The final report is expected by Aug. 31.

"We have our work cut out for us," Augustine said.

The White House is also reviewing the National Space Policy, an overarching document that guides the U.S. military, civil government and commercial space programs.

President Obama is expected to make a decision later this year on the future course of human spaceflight.