The space shuttle Columbia suffered far more stress than anticipated on liftoff last May, forcing changes in launch procedures that will cost the space agency more than $5 million.

The strains on the winged spaceship came after its two solid rocket motors ignited on the launch pad at Cape Canaveral, causing a sudden increase in atmospheric pressure around the 98-ton shuttle. The pressure caused the hydraulic-operated inboard elevons, located on the shuttle's wings, and the body flap just under the main engines, to move a few inches and then snap quickly back into place. It also bent four of the struts that support two forward fuel tanks and crumpled a fifth.

The shuttle has two sets of elevons on each wing, one pair inboard and a second outboard. They are used to maneuver the spacecraft on landing, to give it lift, and to point it down when it is about to touch down on the runway.

The elevons were not damaged by the flexing at liftoff. If they had been, astronauts John Young and Robert Crippen might not have been able to land Columbia safely.

"We didn't damage the vehicle, but we didn't do it any good either," Shutte Project Manager Robert H. Gray said yesterday at the Kennedy Space Center in Florida. "These are unacceptable conditions for the next flight."

While nobody knows why the ignition of the solid rocket motors caused an "overpressure" around Columbia, Gray said that shuttle engineers believe they know how to pevent it from happening again. Gray said that pipes and pumps will be installed at the base of the shuttle launch tower to pump 70,000 gallons of water a minute into the holds just below the solid motors to damp out the pressure waves caused by the sudden ignition of the engines.

"We haven't fully made up our minds, but tis is the way we're thinking right now," Gray said.

Gray said that technicians have begun assembling parts for the water-spray nozzels on the launch pad and are working overtime to have it ready for the shuttle's second flight.

It is scheduled for Sept. 30, and will take astronauts Joe H. Engle and Richard H. Truly on 84 orbits aroun the Earth during a flight expected to last for five days and five hours.

Gray said that when the two solid rocket motors ignitied just before liftoff, the combustion forced a sudden expansion of the air around the shuttle that forced atmospheric pressure to rise from its normal 14.5 pounds per square inch to 16.5 pounds per square inch.

Gray said that movies taken by remote cameras on the launch tower showed the inboard elevons on the wings moving six to eight inches at the time of firing, even though they were locked in place.