“It’s hard to overstate how impressive it is to do so much on the first flight, given the historic track record of new rockets,” said John Gedmark, executive director of the Commercial Spaceflight Federation.

Senator Kay Bailey Hutchison, Republican of Texas, who opposes the president’s space plans, was not swayed. “Make no mistake,” she said in a statement, “even this modest success is more than a year behind schedule, and the project deadlines of other private space companies continue to slip as well.”

She added, “This test does not change the fact that commercial space programs are not ready to close the gap in human spaceflight,” with the space shuttles scheduled to be retired after two more flights and Mr. Obama proposing the cancellation of NASA’s follow-on rocket program.

Suzanne M. Kosmas, a Democratic congresswoman whose district includes the Kennedy Space Center and who has also been skeptical of the proposed NASA changes, issued a more complimentary statement: “The successful test launch of SpaceX’s Falcon 9 rocket,” she said, “is a significant step in the development of the commercial space industry.”

But Ms. Kosmas argued that commercial rockets should be a complement to a NASA-led program, not a replacement.

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Debate on the future of NASA’s human spaceflight program will continue through the summer as the administration and Congress try to arrive at a compromise.

In recent weeks, SpaceX has tried to play down the significance of the first Falcon 9 launching. “I hope people don’t put too much emphasis on our success,” Mr. Musk said Thursday at a news conference, “because it’s simply not correct to have the fate of commercial launch depend on what happens in the next few days. But it certainly does add to the pressure. There’s more weight on our shoulders because of that. I wish there weren’t.”

After the flight, Mr. Musk said it was “to a significant degree a vindication of what the president has proposed.”

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SpaceX is aiming to launch a second Falcon 9 this summer to demonstrate its capabilities for NASA before it gets the go-ahead to take cargo and supplies to the International Space Station. That flight will include an operational version of the Dragon capsule, which will hold cargo and, eventually, astronauts. That capsule would not go to the space station but would demonstrate orbital maneuvers and return to Earth.

The third Falcon 9 flight has been pushed back about five months to March 2011 at the earliest. However, Mr. Musk said he would like to expand its objectives so that the Dragon capsule could go all the way to the space station, perhaps even carrying cargo. That objective had been scheduled for the fourth flight.

SpaceX won a $278 million contract from NASA in 2006 for the demonstration flights, and, if successful, it would move on to a $1.6 billion contract for 12 flights to take supplies to the space station.

Friday’s maiden flight held a mock-up of the capsule. The engines all appeared to fire properly, but the second stage started a slow spin that accelerated as it reached orbit, more than what was expected. “We certainly want to investigate it carefully,” Mr. Musk said.

The only other aspect of flight that did not go quite as planned was the hoped-for recovery of the first stage, which was to descend by parachute into the water. “The feedback we’ve gotten thus far is that the stage broke up on re-entry,” Mr. Musk said.

SpaceX has said it can build a version for astronauts in three years, once it has a contract.