Apollo 17 commander Eugene Cernan, the last man on the moon, told lawmakers Wednesday the Obama administration's plan to shift near-term manned spaceflight from NASA to private industry could result in a 10-year gap between the end of the shuttle program and the debut of reliable commercial rockets.

He also said NASA Administrator Charles Bolden, in a recent conference call, told him and Apollo 11 commander Neil Armstrong, the first man on the moon, that he was concerned NASA might have to subsidize commercial rocket companies if they run into major problems.

"This may be a sensitive point because I'm going to mention something about a dear friend who I have the ultimate respect for, Charlie Bolden," Cernan told the Senate Commerce, Science and Transportation Committee.

"Because we did have a briefing last week and it was in that briefing that Charlie expressed some concern over the potential of the commercial sector to be successful in any reasonable length of time. He indicated we might have to subsidize them until they are successful.

"And I can say with authority, because I wrote this down and I put the word 'wow' right next to it, because Charlie did say it may be a bailout like GM and Chrysler. As a matter of fact, it may be the largest bailout in history."

Earlier in the hearing, Bolden was asked if he used the word "bailout" during the briefing for Cernan and Armstrong.

"I'm not sure I said that," Bolden said. "I'm not sure who was in the room. I have always said I will do everything in my power to facilitate the success of the commercial entities in access to low-Earth orbit. ... I am a contingency planner. I have to look at the possibility that the commercial sector may have difficulties and we will do everything in my power to facilitate their success. So that's what I meant."

The president's new space policy was unveiled in the fiscal 2011 budget proposal, a sweeping change of course for NASA as the agency struggles to complete the International Space Station and retire the space shuttle by the end of the year.

Because of earlier funding shortfalls under the Bush administration, NASA already was facing a five- to six-year gap between the end of shuttle and the debut of the Ares I rocket and Orion capsule being designed as part of the Constellation moon program. NASA currently is buying seats on Russian Soyuz rockets to carry U.S. astronauts to and from the International Space Station.

The Obama administration plans to cancel the Constellation program and the Ares rockets NASA was designing to replace the space shuttle. Instead, the space agency will fund development of new commercial rockets and capsules to end the near-term reliance on Russia. No such "man-rated" rockets or spacecraft currently exist, but Bolden said Wednesday he believes the private sector can be ready to launch astronauts to the station by around 2015.

Cernan questioned that timetable, saying the gap may be much longer.

"In this proposed budget we find several billions of dollars allotted to developing commercial human access to low-Earth orbit, based upon the assumptions and claims by those competing for this exclusive contract who say that they can achieve this goal in little more than three years, and that it can be done for something less than $5 billion.

"Based upon my personal experience and what I believe is possible, I believe it might take as much as a decade, a full decade, and the cost may be two to three times as much as they predict."

While Cernan and Armstrong both said they supported development of commercial space operations, "there are a myriad of technical challenges in their future yet to be overcome," Cernan said, "safety considerations which cannot be overlooked or compromised as well as a business plan and investors that they will have to satisfy."

"All this will lead to unplanned delays which will cost the American taxpayer billions of unallocated dollars and lengthen the gap from shuttle retirement to the day we can once again access LEO (low-Earth orbit) leaving us hostage as a nation to foreign powers for some indeterminate time in the future."

Armstrong agreed, saying "I am very concerned that the new plan, as I understand it, will prohibit us from having human access to low-Earth orbit on our own rockets and spacecraft until the private aerospace industry is able to qualify their hardware under development as rated for human occupancy."

"I support the encouragement of the newcomers toward their goal of lower-cost access to space," he said. "But having cut my teeth in rockets more than 50 years ago, I am not confident. The most experienced rocket engineers with whom I have spoken believe that will require many years and substantial investment to reach the necessary level of safety and reliability."

If so, Armstrong continued, "the United States will be limited to buying passage to the International Space Station from Russia, and will be prohibited from traveling to other destinations in LEO, such as the Hubble Space Telescope, or any of the frequently mentioned destinations out on the space frontier."

"As I examine the plan as stated during the announcement and subsequent explanations, I find a number of assertions which at best, demand careful analysis, and at worst, do not deserve any analysis."

It has been asserted, Armstrong told the committee, that by "buying taxi service to low-Earth orbit rather than owning the taxis 'we can continue to ensure rigorous safety standards are met.' The logic of that statement is mystifying."

"Does it mean that safety standards will be achieved by regulation, or contract, or by government involvement?" he asked. "Does it mean that the safety considerations in the taxi design, construction and test will be assured by government oversight? ... The cost of that government involvement will be substantial and that cost must be acknowledged in the total cost of the service."

In the Obama administration's initial budget rollout, there were no concrete plans to build a new heavy-lift rocket to replace the Constellation program's huge Ares V and no firm timetables for manned flights beyond low-Earth orbit.

During a visit to the Kennedy Space Center last month, the president announced plans to proceed with development of a new heavy lift rocket in 2015 to boost future manned spacecraft out of Earth orbit to any one of a variety of deep space targets.

Both Armstrong and Cernan said they favored sticking with the Constellation program. But Committee Chairman John D. Rockerfeller, a West Virginia Democrat, said the status quo was not an option.

"The President has challenged the United States government to seek greater international collaboration, enable commercial services and develop new exploration technologies leading to human expansion beyond low-Earth orbit," he said.

"These are good priorities and should help ensure that in tough fiscal times, we build our space future in a measured, relevant, innovative, and sustainable way. This is not easy to do but we can do it - and we must. NASA cannot continue down the same path."