Halfway through the last test flight of the space shuttle Columbia, astronauts Thomas K. Mattingly and Henry W. Hartsfield had wrung so many wrinkles out of the 100-ton spaceliner that flight directors began saying today that the shuttle was ready for routine operations this fall.

"We're ready to go," Flight Director Harold Draughon said at the Johnson Space Center where Columbia's flight around the earth is directed. "This flight has been the most benign to date, we don't have any significant problems to work on in the control center."

About the only thing that has gone wrong on the flight was corrected today. A canister the size of a garbage can in Columbia's cargo bay that's nicknamed the "getaway special" after an airline commercial and houses 10 experiments devised by students at Utah State University would not turn itself on no matter how many times Mattingly and Hartsfield tried since last Sunday.

Trouble-shooting the failure in the back rooms at the Johnson Space Center turned up a scheme: The getaway special was turned on today in the same way that thieves start up a car they are about to steal.

"It was similar to hot-wiring a car," Draughon said after Mattingly opened a control panel and crossed two wires. "He just jumped the ground wire into the signal lead and everything worked just fine."

"That was one small switch for NASA," astronaut Michael Coats called up from the Mission Control Center after Mattingly succeeded in hot-wiring the Utah State experiments, "and one giant turn-on for them," the Utah State students.

For a while today, it looked as if one of Columbia's cargo bay doors may have warped. The door has been in the cold while the spacecraft kept its bottom to the sun to bake out any water that may have collected in its tiles while the shuttle was battered by two hours of hail and rain its last night on earth last Saturday.

Flight directors feared that water left under the tiles' protective coating might freeze in the dark side of space, then steam up from the heat of reentry when the spacecraft returns to earth on Sunday.

This might crack open the tiles and expose the shuttle's aluminum fuselage to the high temperatures of reentry. Engineers have figured that as many as 400 tiles on the wings, tail and speed break were soaked through with almost 100 pounds of water by the time Columbia left the earth for space last Sunday.

By early today, flight directors felt that all the water had been baked out of the tiles. Sensors under the tiles along the fuselage were reading temperatures along the entire spacecraft that were almost identical, at about 30 degrees Fahrenheit.

Sitting in space with its bottom to the sun cooled off the top side of the shuttle where the cargo bay doors are located. The new fear of flight directors was that too much time in the cold may have shrunk the latches and the fittings in the aluminum bay doors.

The forward half of the port side door closed, latched and locked, but the latches on the rear half did not function properly. It appeared as if the edge of the rear half of the door was overlapping the bulkhead on the port side.

"The latch mechanism may not be allowing the door panel to slide forward enough to give us the clearance we need," Flight Director Charles (Chuck) Lewis said, "and it looks like that door overlaps the bulkhead."

Instead of leaving Columbia with its tail still aimed at the sun, flight directors told the astronauts to rotate the spaceliner in what they call the "barbecue mode" for 10 hours in the sun starting early tonight to warm up the top side that had been in the cold.

Before televising the closing of the doors, Mattingly and Hartsfield gave viewers a cook's tour of their cockpit as they prepared their lunch. They removed plastic food pouches from their freezer, explained why they added water to the pouches and grinned as they placed the pouches in a tiny electric oven.

They gave demonstration after demonstration of how things float through the cabin when they get loose, declaring that they have to carry more paper towels on a mission than anything else to catch the fluids that spill and float through the cabin.