President Obama delivered his budget request for fiscal year 2011 to Congress on Monday, proposing sweeping changes to NASA's spaceflight program while increasing the agency's overall budget. As had been rumored for days, Obama's blueprint for NASA would cancel the Constellation program, the family of rockets and hardware now in development to replace the aging space shuttle, and would call instead on commercial vendors to fly astronauts to orbit.

Since 2005 the U.S. has spent roughly $9 billion developing the Constellation program's Ares rockets and Orion crew capsule, which were originally supposed to return astronauts to the moon by 2020. Constellation took shape in the wake of the 2003 Columbia disaster as a safer, longer-range successor to the space shuttle, which is slated for retirement this year. But Constellation's costs have ballooned and its timeline has slipped; an independent panel convened by the Obama administration and chaired by former aerospace executive Norman Augustine estimated last year that the Ares rocket system would not be ready for manned missions before 2017, with a lunar return sometime in the mid-2020s, even under the most favorable circumstances.

By scrapping the troubled program—along with its focus on a moon landing—and leaning on the private sector, the agency thinks it will actually accelerate efforts to loft astronauts beyond low Earth orbit, the farthest reach of the shuttle. NASA Deputy Administrator Lori Garver declined to specify a preliminary target for exploration in a teleconference Monday afternoon but mentioned near-Earth asteroids as a potential stepping-stone on the path to ultimately exploring Mars and its moons. She also pointed out that, although the agency will relax its focus on the moon, lunar exploration remains on the table. "We're certainly not canceling our ambitions to explore space," Garver said. "We're canceling Constellation."

Garver tried to put the new approach in context, calling Constellation's stated goal of a moon landing in 2020 "wishful thinking." By stepping back from that unrealistic timeline, she said, the U.S. would be free to undertake more ambitious exploration. "We had lost the moon," Garver said, "and what this program does is give us back the solar system."

Sources revealed the contents of the budget request to various newspapers last week, spurring a wave of condemnation from Michael Griffin, a former NASA administrator and tireless Constellation champion, and from members of Congress who represent states with major NASA centers focused on the human spaceflight program—Texas, Florida, Alabama. Those lawmakers will have their say when the houses of Congress hammer out their own budgets in the coming weeks.

In Monday's teleconference, NASA Administrator Charles Bolden expressed support for the budget request, saying that he was "excited" to present the president's proposal, which would add $6 billion to NASA's total outlay over the next five years. Bolden said that he and Obama agreed that Constellation was in an untenable position. "The truth is, we were not on a sustainable path to get back to the moon's surface," Bolden said. He applauded the decision to delegate the development of launch capabilities to commercial providers while, he said, "NASA firmly focuses its gaze on the cosmic horizons beyond Earth."

In addition to spurring the development of commercial rockets, Obama's budget is designed to extend the life of the International Space Station, still under construction, to at least 2020. It would also fund a replacement for the Orbiting Carbon Observatory, the CO2-tracking satellite that failed to reach orbit in a February launch.

Sally Ride, the first U.S. woman in space and a member of the Augustine commission, which cast Constellation's future in a fairly unflattering light, called Obama's budget request "a significant vote of confidence for NASA." The proposal, Ride said, "puts NASA on a sustainable path toward the future."

Bolden, also a former astronaut, vowed that tapping private spaceflight companies for manned launches would not diminish NASA's commitment to safety. He seemed to become choked up as he spoke of losing friends in both the Challenger and Columbia accidents, the latter of which occurred exactly seven years to the day before Monday's budget announcement. "No one cares more about safety than I," Bolden said. "I give you my word that these vehicles will be safe."