WASHINGTON - As investigators sort through the wreckage of the space shuttle Columbia, Congress is preparing a major re-evaluation of the space program's budget, its mission and its future course.

Key lawmakers are seeking a detailed account of what caused the shuttle to break apart 39 miles above the Earth's surface, killing all seven crew members and scattering shards of its fuselage over at least two states.

But congressional leaders are planning to go beyond fact-finding to take a tough look at the future of space exploration and the 22-year-old shuttle program, including whether to speed up efforts to find a newer, safer and less expensive vehicle to take humans into outer space.

Congress will continue to support the shuttle program and human space flight, lawmakers and aides said, but it will struggle in the coming weeks and months to balance the need to make NASA's three remaining shuttles safer with a mandate to develop new technologies to reduce the agency's reliance on the shuttles.

"There's two pods here," said Sen. Sam Brownback, a Kansas Republican, emerging from a closed-door briefing yesterday evening with NASA Administrator Sean O'Keefe, who did not comment.

"There's what happened, why, how do we prevent it from happening in the future, and then also I think this is a good time for us to step back and look at the overall space program, and say how should we proceed?" said Brownback, who chairs the Commerce, Science and Transportation Committee's space subcommittee.

Brownback says the United States is "locked in" to the space shuttle program because of its need to support the continuing development of the International Space Station, at least in the short term. The shuttle ferries supplies, personnel and provisions from Earth to the space station.

But some members of Congress say the Columbia disaster has convinced them that NASA should pour more resources into developing the so-called Orbital Space Plane - envisioned as a modern, multipurpose vehicle that would be launched by an expendable rocket - to take crews to and from the space station and perform other missions.

"This will accelerate what was already recognized as an important shift away from dependence on the shuttle as the workhorse of the space program," said Rep. Dana Rohrabacher, the California Republican who has chaired the House Science Committee's space panel for the past six years.

"We'll have to continue to fly shuttles [but] you've got to move out of the '60s and '70s when the space program was in its glory days, and develop new ways, a new generation, of doing that," he added.

The Science Committee has launched an investigation of the loss of the Columbia, as it did in 1986 after the explosion of the space shuttle Challenger. In addition, the Senate Commerce, Science and Transportation Committee plans to hold a series of hearings on the Columbia disaster, beginning with a session next week in which O'Keefe is expected to testify on the status of his agency's two investigations of the accident.

Two NASA panels are probing the loss of the Columbia: the internal Mishap Investigation Board and an external committee chaired by retired Navy Adm. Harold W. Gehman Jr.

Senior lawmakers, some of whom have long expressed concern about the adequacy of NASA's budget and planning efforts for space exploration, have many questions of their own about what went wrong, and whether decisions by Congress and executive branch officials might have played a role in the accident.

Many are asking whether the level of funding devoted to NASA and its shuttle program in recent years has been adequate to ensure safety.

"You can't have a space budget that stays flat for the last 12 years," said Sen. Bill Nelson, a Florida Democrat and former astronaut who traveled aboard the Columbia in 1986.

Critical changes, such as installing high-pressure fuel pumps on engines and auxiliary power units, have been delayed for lack of funding, Nelson said.

"I think we've cut the budget too much," said Sen. Kay Bailey Hutchison, a Texas Republican and senior member of the Commerce Committee. "If we are going to fulfill our mission, we're going to have to do it by defining the mission carefully, and then funding it."

Those concerns were the subject of a critical report last March in which NASA's Aerospace Safety Advisory Panel concluded that: "The current and proposed budgets are not sufficient to improve or even maintain the safety risk level of operating the space shuttle and [the International Space Station]. Needed restorations and improvements cannot be accomplished under current budgets and spending priorities."

The report stressed that shuttle safety had not yet been compromised, but at a House space subcommittee hearing one month after its release, Richard Blomberg, who headed the panel when the report was prepared, told lawmakers he had grave concerns.

"In all my years of my involvement," Blomberg testified, "I have never been as worried for space shuttle safety as I am right now. All of my instincts suggest that the current approach is planting the seeds for future danger."

Bush released yesterday his proposed 2004 budget that would provide $15.5 billion for NASA, a $500 million increase - or about 3 percent - over what he asked for in 2003. The budget, completed before Saturday's catastrophe, includes a $600 million boost for the shuttle program.

"NASA's budget numbers are now entirely meaningless. There's going to have to be a major re-examination of all those numbers," said Heidi Tringe, a spokeswoman for the House Science Committee.

Mitchell E. Daniels Jr., Bush's budget director, said it is too early to say whether the Columbia disaster will affect NASA's funding. Bush has increased the agency's budget since taking office, Daniels said, and there is no guarantee that more funding would improve safety or prevent disasters.

"If there's a lesson in the last couple days, it's, I suppose, another sad example that more money alone can't always avoid very sad setbacks," Daniels told reporters yesterday.

The administration's budget documents, meanwhile, contained some criticism of NASA: "Shuttle operations are well managed but investments to improve the shuttle suffer from inadequate planning and poor cost management."

Congress has not completed negotiations on the budget for the current fiscal year. Nelson said Congress should include at least "a few tens of millions" for shuttle upgrades as part of a midyear supplemental spending measure it is expected to pass this spring. Daniels suggested that is unlikely.

One issue lawmakers are certain to probe is NASA's response to evidence it found shortly after liftoff showing that a piece of insulating foam had fallen from Columbia's big external fuel tank, hitting the orbiter and possibly damaging thermal tiles on its left wing. The problem had occurred before on other missions, NASA has said.

"One of the first things we need to ask is, if it did happen before, how could it possibly have happened again?" Rohrabacher said.

The Senate unanimously passed a resolution yesterday to honor the shuttle mission, saying it "commemorates, with deep sorrow and regret, the fate of the Columbia."