WASHINGTON — The U.S. House of Representatives is expected to vote on a NASA authorization bill as early as July 29 that would set funding levels and provide policy guidance to the space agency over the next three years, according to House aides.

The bill (H.R. 5781), approved by the House Science and Technology Committee July 22, fully funds NASA’s $19 billion request for the fiscal year that begins Oct. 1, but guts a White House proposal to spend $5.9 billion over the next five years fostering development of commercial vehicles to ferry astronauts to and from Earth orbit. Although the measure includes $150 million for privately developed space taxis through 2013 and another $300 million in the form of government-backed loans or loan guarantees, it would also 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 the White House has targeted for termination.

Congressional aides said the measure is expected to be brought to the House floor under a suspension of the rules, a procedural move that limits amendments to a bill during floor debate but which requires a two-thirds majority vote to pass. Senior Democratic and Republican members of the House Science and Technology Committee, which drafted the bill, have met with House leaders to discuss the bill, according to a House aide, who said the members were “reasonably confident” of obtaining the two-thirds majority vote needed to pass it.

Companion legislation approved by the Senate Commerce, Science and Transportation Committee July 15 would also reduce funding for commercial crew programs and continue spending on elements of Constellation. The Senate bill has yet to see floor action, but if the House measure is approved, it would provide guidance to House appropriators as they move forward with a 2011 spending package for NASA this fall. That measure is most likely to come in the form of a continuing resolution in late September or early October that would fund NASA at 2010 spending levels until a comprehensive 2011 appropriation is approved.