WASHINGTON — A flurry of behind-the-scenes maneuvering took place late July 28 as opponents of a NASA authorization bill fought back efforts by leaders of the U.S. House Science and Technology Committee to bring the measure to a floor vote before lawmakers break for the summer district work period that begins Aug. 2.

House aides and political observers said Rep. Bart Gordon (D-Tenn.), who chairs the panel, is expected to meet with aggrieved lawmakers July 29 to address concerns with key elements of the measure, a three-year authorization that seeks to gut a a multibillion dollar White House initiative to foster development of commercial crew taxis.

House sources said July 28 that a floor vote on the NASA authorization could come as early as July 29, but opponents of the bill — primarily commercial space advocates — were successful in stalling the measure, which now is unlikely to be considered before July 30, sources said. Gordon is seeking to bring the measure to the House floor under suspension of the rules, a procedural tactic that prevents amendments to a bill during limited floor debate and which requires a two-thirds majority vote to pass.

The bill, H.R. 5781, would not actually fund NASA, but it would set guidelines for how much Congress can spend on the agency’s programs. House appropriators, in approving a $19 billion budget for NASA in June, fenced off most of the agency’s $4.2 billion human space exploration budget pending enactment of an authorization bill.

The House Science & Technology Committee approved H.R. 5781 with strong bipartisan support July 22, sending forward a bill that authorizes only a small fraction of the $3.3 billion NASA sought to invest in a commercial crew transportation system over the next three years, approving $150 million through 2013 and another $300 million in the form of government-backed loans or loan guarantees. The measure also would continue much of the work being done under NASA’s Constellation program, a 5-year-old effort to build new rockets and spacecraft optimized for lunar missions that President Barack Obama targeted for termination in his 2011 spending proposal delivered to Congress in February.

Commercial space advocates are working to kill the bill. For example, Space Exploration Technologies (SpaceX), the Hawthorne, Calif.-based company eager to fly NASA astronauts to the international space station aboard its Falcon 9-launched Dragon capsule, is e-mailing supporters to urge their lawmakers to vote no on H.R. 5781.

“If you care about the future of American space exploration, your urgent help is needed,” SpaceX Chief Executive Elon Musk wrote in the e-mail. “The only hope for the average citizen to one day travel to space is in danger due to the actions of certain members of Congress.”

Lawmakers are running out of time to move measures to a vote before the U.S. government’s new fiscal year begins Oct. 1.

The House is expected to break Aug. 2, when members will head home to campaign for six weeks in advance of November elections. That leaves just three weeks in September to pass legislation before the fiscal year ends Sept. 30.

During a six-hour markup of the bill July 22, Gordon said the NASA authorization would create a balanced, sustainable manned space exploration program that allows the agency to live within its means.

“We are in tough economic times, and we cannot do it all,” Gordon said, adding “some of the ‘nice-to-haves’ have had to be deferred, and worthy activities have been funded at lower levels than some of us would like.”

But a small number of Democratic House lawmakers take issue with Gordon’s bill, House aides and commercial space advocates said, including members of the California and Ohio delegations who support the president’s emphasis on private-sector initiatives and increased funding for advanced technology research that could spur a commercial space market while seeding cutting-edge exploration capabilities for exploring beyond low Earth orbit.

In a July 21 letter to Gordon, 13 California Democrats urged the committee to restore funding for commercial crew and cargo initiatives and exploration technology programs requested in Obama’s 2011 spending plan.

“These reductions will have a serious effect on California’s workforce and economy, and that of many states,” states the letter, which was spearheaded by Rep. Anna Eshoo, a Silicon Valley Democrat who has worked closely with House Speaker Nancy Pelosi (D-Calif.) on energy and technology policy initiatives in Congress. “These are areas that should be the cornerstone of NASA’s new direction because they will drive innovation and job creation across the nation.”

A companion NASA authorization bill approved by the Senate Commerce, Science and Transportation Committee July 15 also would reduce funding for commercial crew programs and continue spending on elements of Constellation, though it is touted as a compromise between Obama’s commercial direction for NASA and lawmakers who want to see the agency focused on building government-owned spacecraft for sending astronauts beyond low Earth orbit. The bill awaits floor action in the Senate, where appropriators approved July 22 a $19 billion NASA spending measure that halved the agency’s $500 million request for commercial crew and funded continued development of a government-led Orion Crew Exploration Vehicle.

Meanwhile, if Gordon’s measure is approved by the full House, it would provide guidance to House appropriators as they move forward with a 2011 spending package for NASA this fall.