NASA is not abandoning efforts to develop a new heavy lift booster in the wake of the Obama administration's decision to cancel NASA's moon program, agency Administrator Charles Bolden said Saturday. But he added that any such rocket, even one using subsystems planned for the canceled Ares 5, is unlikely to fly before the 2020s at best, implying U.S. manned missions beyond low-Earth orbit are one to two decades away.

But even that long-range, somewhat nebulous goal is uncertain as NASA and congressoinal lawmakers struggle to understand the implications of the Obama administration's new direction for the civilian space agency.

That new direction, laid out in the administration's fiscal 2011 budget, calls for NASA to operate the International Space Station through at least 2020 and to buy commercial rockets and capsules to ferry astronauts to and from the lab complex in low-Earth orbit.

The Constellation moon program, developed by NASA during the Bush administration, was canceled and while the space agency will get an additional $6 billion over the next five years to spur development of a commercial manned launch capability, a long-range goal for exploration beyond low-Earth orbit was not specified.

Many critics of the president's plan have complained about the lack of emphasis on a heavy lift rocket to boost spacecraft into deep space. But Bolden insisted Saturday that NASA has not abandoned heavy lift development. He argued some form of a powerful new rocket likely would fly before the Ares 5 could have launched given Constellation budget shortfalls.

He said he hopes he can convince Congress in the weeks and months ahead "that we can put ourselves on a path to obtain a heavy lift launch capability within the next couple of decades."

"Ideally, I would like to be flying a heavy lift launch capability between 2020 and 2030," he said. "Whether or not we've matured to the point by then that the next NASA administrator will feel comfortable that it's OK to put humans on that heavy lift launch vehicle, I can't say right now."

In the near term, the most critical step is defining what destinations make the most sense and Bolden said he believes Mars should be the ultimate goal. But any target beyond low-Earth orbit will require a powerful new rocket.

"I haven't talked to anybody, whether it's in OMB (Office of Management and Budget), the White House or anywhere that doesn't believe the nation needs a heavy lift launch vehicle capability," he said. "We need it for science, we need it for intelligence, we need it for DOD and NASA definitely needs it if we're going to talk about sending humans beyond low-Earth orbit.

"So the need for a heavy lift launch vehicle, I don't think there's any disagreement on the part of anybody," he said. "How do we evolve there? We take the lessons learned from Constellation. If I'm able to negotiate with Congress appropriately, we may actually end up carving out some subsystems that are in the current Constellation program because they are advanced technology and they are things we will need to develop any heavy lift launch system.

"So while we will phase out the Constellation program per se, I don't want to throw away the baby with the bathwater, if you will. We want to try to capture technologies and capabilities that are resident in the present Constellation system and use them as we migrate toward a new heavy lift launch vehicle."

Bolden defended the controversial push to develop a private sector manned launch capability and said different levels of oversight would be applied to companies with different levels of operational experience.

He also said he expects a debate about the future role of astronauts in the new program, saying it was not yet clear whether the government would, in effect, hire a commercial crew to carry out a specific task or use government astronauts on a commercial rocket.

He said while many Americans "idolize" astronauts, "there is a small contingent of people on the outside who really have a great disdain for astronauts. They feel because there is this elite astronaut corps, that we have stopped others from being able to go into space. So if they can just get rid of the elite astronaut corps, then everybody else can go fly.

"That's a discussion we need to have," he said. "When we start using commercial capabilities to get people to low-Earth orbit, does that mean the astronaut office goes and says 'I want to rent a spacecraft to take a crew of six to the international space station?' Or 'I want to rent a crew to go to ISS to do six months of work?' There's a distinct difference between that operational mode. And that's the discussion we need to have."

Even so, Bolden, citing the experience of chief astronaut Peggy Whitson as an example, said space station astronauts require a high degree of training and "I contend that I can't go out here and pick Joe Schmuck up off the street and send them to Johnson Space Center or here to the Kennedy Space Center for six weeks and they're going to be a Peggy Whitson. Ain't going to happen."

"So we need to have the discussion of what the future, the next generation of astronauts will be like. And our international partners have a lot to say about that, because they happen to like the elite astronaut corps. So we need to have the discussion of how important is it to have a career astronaut contingent as opposed to none. But we'll do whatever the American public wants."