James C. Fletcher, nominated to run the embattled National Aeronautics and Space Administration, yesterday defended his earlier stewardship of the agency amid charges that he oversold the shuttle program by giving misleading and overly optimistic projections about its costs.

Fletcher, who headed NASA from 1971 to 1977 during the birth of the shuttle, acknowledged that he misjudged in 1972 when he estimated that the cost of each shuttle launching would be $10.45 million -- a figure that turned out to be $279 million per launch.

"My only answer is that something happened on the way to the bank," Fletcher said during his confirmation hearing before the Senate Commerce, Science and Transportation Committee yesterday.

Fletcher contended that these and other discrepancies cited in audit reports could be explained by inflation and technical problems that have resulted in a far less ambitious launch schedule than was originally projected. But Sen. Albert Gore Jr. (D-Tenn.) said he was concerned that the audits, recounted yesterday in a lengthy article in The New York Times, reflected on Fletcher's previous management of the agency.

Citing another example, Gore noted that Fletcher had projected the cost of lifting shuttle cargo at $100 per pound compared to current estimates of $5,264 a pound.

"The cumulative impression is not a good one and I'm quite concerned about it," Gore said. "But I don't know what to do about it. Obviously, we're on a fast track and you're the person for the job. But a lot of this occurred during your tenure."

When Fletcher said it would be difficult for him to respond to questions about early cost projections for the shuttle because he has been gone from the agency so long, Gore responded that "it may be difficult for me to evaluate your qualifications" otherwise.

Despite that exchange, Fletcher's nomination was expected to win speedy confirmation as many senators said they were more concerned about NASA going long without a permanent administrator amid the turmoil produced by the Challenger accident.

Fletcher, 66, would replace James M. Beggs, who resigned last January to fight fraud charges stemming from his earlier duties as an executive of General Dynamics Corp. The agency has been without a permanent chief since the Jan. 28 shuttle disaster.

"It's very disturbing . . . . it's been three months now," said Sen. John Glenn (D-Ohio), a former astronaut who introduced Fletcher to the panel. "You can't go along with an agency in limbo like this . . . and expect them to recover . . . . Stop flubbing along with the lack of leadership over there."

While avoiding a firm stand on most key issues facing the agency, Fletcher pledged that the shuttle will not fly again until it is proven to be a "safe and effective vehicle and if we have to slow down the flight schedule, we will."

NASA officials have projected that the shuttle will return to operation in about 18 months with a scaled-down launch schedule of nine flights a year. But Fletcher questioned whether this was achievable, saying, "Nine seems like a rather substantial number if you're talking about the first year."

On other matters, Fletcher said he supports building a fourth orbiter to replace Challenger, and moving to a "mixed fleet" of shuttles and unmanned rockets to launch commerical satellites. He said NASA should continue to launch commercial satellites but that some of those payloads booked on the shuttle could be "off-loaded" to unmanned rockets.

Fletcher, who had denounced Challenger accident inquiries as a "witchhunt," told the panel the remark was "careless" and that he wanted to publicly apologize for it.