The chairman of the U.S. House Science and Technology Committee plans to revise draft NASA authorization legislation to remove a loan guarantee program aimed at developers of private space taxis, saying congressional budget analysts determined the market for commercial crew transportation is too uncertain to put federal dollars at risk.

In a Sept. 3 letter to Stanford University professor and former director of NASA’s Ames Research Center Scott Hubbard, Rep. Bart Gordon (D-Tenn.) described the loan guarantee approach as a creative funding mechanism that could leverage substantial additional private-sector investment for commercial crew activities through government-backed loans and loan guarantees.

However, Gordon said the U.S. Congressional Budget Office determined the financial risk to the federal government is too great — and the assumed nongovernment market for commercial crew services too uncertain — to make the loan guarantee program viable.

“As a result, we will need to remove the loan guarantee provisions from the bill,” Gordon wrote in a four-page response to an Aug. 31 letter to key House lawmakers signed by Hubbard and a group of Nobel laureates, ex-astronauts and other former NASA officials concerned the bill, H.R. 5781, substantially underfunds proposed technology development and commercial crew initiatives.

“Moving forward, we will continue to look for ways to cost effectively fund commercial crew-related activities that can benefit the whole industry while ensuring that other critical missions are supported and within the overall budgetary constraints,” Gordon wrote.

Gordon asserted the three-year authorization bill proposes spending $2.5 billion for commercial cargo and crew initiatives over three years, though only a small fraction of the funds — $450 million, including $300 million suggested for the loan program — would pay for commercial crew system development through 2013, representing an 87 percent reduction to President Barack Obama’s $3.3 billion request for privately developed crew taxis. The balance — roughly $2 billion over three years — would cover NASA spending on Commercial Resupply Services contracts the agency signed with Dulles, Va.-based Orbital Sciences Corp. and Hawthorne, Calif.-based Space Exploration Technologies (SpaceX) in 2008. Worth a combined $3.5 billion, the agreements call for Orbital and SpaceX to begin making  cargo runs to the international space station using new rockets and spacecraft being developed under NASA’s Commercial Orbital Transportation Services (COTS) program.

The White House requested $312 million for COTS next year — $300 million more than NASA previously forecast needing for the $500 million program. NASA officials say the additional money is intended to retire risk and accelerate spacecraft development. Gordon’s bill provides just $14 million for the effort, noting that the extra $300 million was not sought by the companies.

“Neither NASA nor the companies involved have stated that the commercial cargo funding augmentation is needed to meet the commercial cargo demonstration commitments laid out in the COTS demonstration program, which argues for reallocating the funds to higher priority NASA activities,” he stated in the letter, adding that the funding boost raises “a number of questions about the status of the commercial development and whether the commercial providers will meet their contractual milestones under the follow-on commercial resupply services contracts.”

Further, Gordon says the request for additional cargo funds “reinforces the view of many in Congress that it is premature to make NASA’s human spaceflight program dependent on the achievement of the significantly more difficult objective of developing commercial crew systems by a date-certain and for an assumed cost.”

“With these concerns and a tight budget, it became difficult to provide additional funds for commercial crew development,” he wrote.

Gordon also defended a decision to delay funding flagship exploration technology demonstrations and robotic precursor missions before NASA’s human exploration program has been clarified. The administration requested $5 billion for the initiatives over the next three years, though H.R. 5781 authorizes just $10 million beginning in 2013.

“One only has to look at the Administration’s robotic precursor budget request to see that it is ill-defined, e.g., a lunar lander/in-situ resource extraction demonstration mission being proposed at the same time the president is stating that he has no intention of pursuing a human lunar mission; and a proposed mission to visit a Lagrangian point, despite the fact that NASA has had Lagrangian point spacecraft operating in that environment for the past several decades,” Gordon wrote.

Gordon said H.R. 5781 shifts some of the exploration technology funding to NASA’s new space technology development account, where it is less likely to be siphoned off in an attempt to pay for higher-priority programs. Although the bill fully funds the administration’s $2.6 billion request for space technology development, Gordon’s letter does not explain how much of that money comprises exploration technology demonstration funding.