When he returned to Earth after seven days in space aboard the shuttle Challenger, Air Force Col. Frederick D. Gregory said of the liftoff from Cape Canaveral:

"Nothing prepared me for the sensation of those main engines starting and those solids lighting up underneath us. That son-of-a-gun really rattles and rolls when it takes off."

That "rattle and roll" underscores a new concern of shuttle managers as they plan the manifest for the next five years. The question is: Does the space shuttle give its passengers and cargo such a rattling good ride that the noise and vibration damage goods in the cargo bay?

The space agency maintains that the shuttle is no rougher a ride than the Titan launch vehicle the shuttle replaced four years ago. But the first shadows of doubt are creeping into the minds of people planning the shuttle program.

There were the two communications satellites -- Westar VI and Palapa B -- deployed by the shuttle that were retrieved and returned to Earth after drifting aimlessly in space for almost a year. There is the Syncom satellite that might be retrieved by a shuttle crew in August, now lying dead in space after its launch in April.

Trouble arose again on Gregory's flight this month. The astronauts couldn't open the scientific air lock on the Spacelab to position a wide-field camera for a look into space. The latch that would have released the air lock was badly bent -- possibly because of a rough ride.

One experiment to measure fluid dynamics in weightlessness in the $1 billion Spacelab refused to work until the fifth day of the seven-day flight, mostly because of a short circuit in one power line that could have been caused by a jolt to a wire during ascent.

Another Spacelab experiment to measure molecules of synthetic chemicals that could be attacking the Earth's protective ozone layer quit after four days, mysteriously losing all pressure in the laser spectrometer that was the heart of the experiment. "Was this failure launch related?" asked Dr. Barney Farmer of California's Jet Propulsion Laboratory, where the experiment was built. "I think it had to be. It certainly wasn't careless engineering."

Shuttle managers are quick to defend the $1 billion spaceliner, whose record so far is not hard to defend. Columbia, Challenger and Discovery have flown 17 times in four years without a serious accident on takeoff, in orbit or landing. At least two of the three satellites that failed in space did so because of onboard rocket engine difficulties, not because the shuttle was too rough.

One shuttle crew was able to fix the Solar Max satellite in orbit and return it to service after almost four years. Another brought two crippled satellites back to Earth, avoiding what otherwise would have been an $85 million disaster. Said shuttle program manager Glynn S. Lunney: "If we didn't have astronauts flying the shuttle, we never would have been able to perform those rescue missions. The shuttle and her crew made them possible."

"We've flown 17 times, four test flights and 13 operational flights," Johnson Space Center Director Gerald D. Griffin said in an interview. "If this were an airplane, we'd still be in the test part of the program, we'd be nowhere near operational."

Griffin concedes that "occasional" mistakes have led to mishaps in the shuttle program, but he insists that "we are not repeating our mistakes." He used as an example the Syncom satellite, deployed in April with no power to raise it to a permanent orbit 22,300 miles above the equator.

"I think we'll learn something from this," Griffin said. "If Syncom's problem was due to vibration or noise on liftoff, I think we'll learn something that we can apply to a fix so we can better isolate satellites in the cargo bay or shield them from whatever caused the Syncom problem." Griffin said he also believes that it is time for a change in the way NASA does business with its satellite customers. He said the Syncom would never have been deployed without any power if NASA had insisted that Hughes Communications Corp., Syncom's owner, install a device that flashed a warning to the shuttle's cockpit that it had no power.

"We've always insisted our customers adhere to our safety standards to protect the crew and the shuttle, but we've never insisted they do anything else," Griffin said. "We don't want to be 'Big Brother' but we're beginning to think that some of their the customers' design features are not good for us. I'd like to see more data in the cockpit."

Griffin said he does not believe that the shuttle gives its satellite cargo too hard a ride. "It's no harder than the Titan," NASA's and the Air Force's workhorse launch vehicle for years, he said.

The astronauts also defend the shuttle's ride. Marine Col. Robert F. Overmyer, who commanded Challenger on its last flight, said, "Our flight into orbit was as smooth if not smoother than any flight I've been on. I flew the fifth shuttle mission and I know this one the 17th was smoother than the fifth."

NASA knows a great deal is riding on what lies ahead. Discovery is scheduled in June to carry three communications satellites into orbit, one for AT&T, another for Mexico and the third for Saudi Arabia. A second Discovery flight in August is even more crucial. Not only will there be another Syncom aboard, but also the crew will probably attempt to retrieve the stranded Syncom.

"I think it's worth it, if just for insurance reasons," Griffin said. "They'll have to pay us for the retrieval, but it's like paying for your dented fender out of your own pocket just to keep the insurance rates down."