WASHINGTON — Lockheed Martin Space Systems Co. could deliver an Orion-based crew rescue vehicle for the international space station for as little as $4.5 billion if NASA relaxes some of the oversight it normally exercises on manned spaceflight contracts, according to the company’s top executive.

“If I were utterly unconstrained by funding requirements and asked to provide my best estimate of what would be a rational test program, it’s in the range of $4.5 billion to $5.5 billion,” Joanne Maguire, executive vice president of Denver-based Lockheed Martin Space Systems, said in a June 17 interview.

Maguire said hitting that price range would require a “departure” from the agency’s standard supervisory role. “We’re looking at, and really making some suggestions to NASA about how they might streamline this program,” she said. “Part of that is looking at the real value-add of some of the oversight that they were anticipating providing.”

Originally designed to carry astronauts to the space station and eventually to the Moon as part of NASA’s Constellation program, Orion was marked for termination when the White House unveiled a new direction for the U.S. spaceflight program in February. In April, U.S. President Barack Obama revised his plan, saying Orion, unlike the rest of Constellation, would be retained but scaled back for the space station crew lifeboat role.

This has not mollified increasingly skeptical U.S. lawmakers, who in recent days have stepped up their demands for documentation supporting the administration’s decision to terminate Constellation. Most recently, senior members of the House Science and Technology Committee demanded that NASA provide all of the documentation — including records, charts, e-mails and recorded voice messages — that went into the formulation of the president’s $19 billion 2011 budget request for the space agency.

The demand follows what the committee said have been repeated unfulfilled requests for information to support NASA’s change in direction. One such request came with a June 16 deadline, which NASA Administrator Charles Bolden responded to in a letter delivered to the committee late that day.

Bolden said the agency is still pulling together elements of the budget plan and that he would share details with Congress when he is ready.

“Since NASA has failed to provide the Committee with any detailed supporting materials with which Congress can judge the proposed human spaceflight plan, Congress must insist upon the production of all materials NASA relied upon in formulating its proposal,” the committee’s chairman, Rep. Bart Gordon (D-Tenn.), wrote in a June 17 letter to Bolden. The letter was co-signed by Rep. Ralph Hall (R-Texas), the committee’s ranking member, and by Reps. Gabrielle Giffords (D-Ariz.) and Pete Olson (R-Texas), the chairwoman and ranking member, respectively, of the panel’s space and aeronautics subcommittee.

The information provided by NASA should also include “any analysis of the executability of the proposed plan through 2025,” the letter said. The lawmakers also demanded all records relating to the formulation of NASA’s revised human spaceflight plan that preserves Orion as a crew lifeboat.

Any relevant records that NASA chooses not to share should be documented “item by item, with the express legal basis for the privilege claimed for each item clearly noted,” the letter said.

The lawmakers asked that NASA deliver the documents to the House Science Committee’s room in the Rayburn House Office Building no later than close of business June 25, which is a Friday.

On the other side of Capitol Hill, meanwhile, U.S. Sen. Bill Nelson (D-Fla.), chairman of the Senate Commerce science and space subcommittee, offered a sneak peek at a NASA authorization bill that would direct the agency to begin work next year on a heavy-lift rocket that takes advantage of existing infrastructure, including the space shuttle, and work performed to date on Constellation.

“The authorization bill will direct NASA to initiate development of a heavy-lift vehicle in fiscal year 2011, both to support these new human space flight activities and to serve as a contingency capability to the [international space station],” Nelson said in a June 14 letter to Sen. Barbara Mikulski (D-Md.), who chairs the Senate Appropriations subcommittee that oversees NASA spending. “The authorization will propose that both the heavy-lift and crew exploration vehicles leverage the workforce, contracts, assets and capabilities of the Shuttle, Ares 1 and Orion efforts.”

The president’s plan would scrap Constellation’s shuttle-derived Ares 1 and heavy-lift Ares 5 rockets and direct NASA to spend the next five years developing new designs for a rocket powerful enough to support deep-space exploration missions.

Nelson said the heavy-lift rocket and crew exploration vehicle he envisions would constitute “NASA’s core contributions” to future space exploration, including early missions to Lagrange points — gravitationally stable locations in space — or lunar orbit that would form a foundation for follow-on missions to other destinations, ultimately leading to Mars.

Nelson said his bill would take a “walk before you run” approach to the private-sector space-taxi services NASA proposed funding with almost $6 billion in new spending over the next five years. He said astronaut safety — which tops Mikulski’s list of concerns regarding NASA’s new direction — “will be the core component” of all commercial crew requirements, “as with any human space flight program.”

The authorizing legislation would support Obama’s plan to continue operating the space station through 2020 and provide “the logistics and support necessary to maximize the scientific return on our investment” in the orbiting outpost, Nelson said. The bill would make commercial cargo delivery “an important component of this overall strategy, and the flight of an additional space shuttle mission — the current ‘Launch on Need’ flight — will help ensure that the [international space station] remains robust until the space shuttle is gracefully retired.”

The so-called launch-on-need flight refers to the space shuttle NASA keeps at the ready to launch on a rescue mission if something goes awry during another shuttle’s mission.

In a statement issued by her office June 14, Mikulski said the elements of the authorization bill outlined in Nelson’s letter offer “an alternative framework for NASA’s human space flight program that could snap us out of the ‘stagnant quo.’”

Among the biggest concerns voiced by lawmakers — besides the loss of thousands of jobs that would result from Constellation’s cancellation — is that the money that would be spent to continue work on Orion will consume a large portion of the funding the White House has budgeted over the next five years for exploration-related technology development, including a heavy-lift rocket. Sources on Capitol Hill worry that the lower-range cost estimates are overly optimistic.

Maguire said Lockheed Martin has been discussing Orion contract options with NASA and considering ways to streamline development and test plans for the crew rescue capsule using “fewer test articles” and potentially altering the timeline for tests.

“Our original Orion program had us doing testing of the lunar version of the vehicle before the first crewed vehicle would fly,” Maguire said. She added that the test schedule could be amended and trials of the lunar Orion variant scrapped entirely.

But Maguire also made a case for continuing Orion as originally designed in an appeal that could resonate with lawmakers such as Nelson, who worry that the president’s plan defers deep-space exploration for too long.

“It’s our judgment [that] there is great value in proceeding with Orion as an exploration vehicle, but you’d need to make some kind of near-term commitment to a heavy-lift vehicle,” she said, adding that if NASA continued Orion development as planned under the Constellation program, “this lifeboat capability could be provided really for very marginal cost.”

As for the rocket needed to launch a deep-space Orion capsule beyond low Earth orbit, Maguire — who serves on the board of Denver-based United Launch Alliance, the Boeing-Lockheed Martin joint venture that builds the Delta 4 and Atlas 5 launchers — thinks there are “affordable, less-ambitious-than-Ares-5 vehicles that could be fielded in the latter half of this decade, if we get started soon.”