Soviet Spaceship Slated for Repair Job in Orbit : Soyuz: Astronauts await delivery of a ladder to fix the craft damaged during takeoff.

The Soyuz spacecraft that took two Soviet cosmonauts to the space station Mir last February was damaged slightly during takeoff and is scheduled to be repaired before the cosmonauts can return to Earth, U.S. experts said Friday.

The experts stressed that the damage does not appear to threaten the cosmonauts or their mission.

Although American space officials have known about the damage to the Soyuz craft since February, the knowledge did not become public until Soviet cosmonaut Alexander Serebrov, visiting the United States, revealed it in an interview with the trade journal Aviation Week and Space Technology. The magazine’s edition dated May 21 was published Friday.

According to the experts, pieces of insulation on the outside of the Soyuz craft tore loose and are now blocking sensors that are used for aligning the craft for re-entry. But the craft has adequate backup sensors to perform the re-entry, according to James Oberg, an American expert who has written a number of books about the Soviet space program.

“There is absolutely no reason to doubt that their ship is flyable as it is,” Oberg said in a telephone interview.

But he added that the cosmonauts are preparing to make repairs before their scheduled Aug. 2 return to Earth, as soon as a resupply vehicle takes them an extendable ladder that will allow them to reach the damaged area.

The insulation is used to keep the Soyuz from growing too cold when its power is turned down for long periods while it is docked to Mir. According to former U.S. astronaut John Fabian, who was briefed in Washington by Serebrov, the Soyuz is now much colder than normal and Soviet officials fear that the cold will cause water to condense in and damage the vehicle’s electronic components.

Soviet ground controllers have ordered the two cosmonauts aboard Mir, Anatoly Soloyev and Alexander Baladin, to reposition the space station so that the Soyuz receives more sunlight in an effort to keep it warm.

The cosmonauts cannot simply climb into their spacesuits and fix the pieces of insulation batting, Serebrov said, because there are no handholds on the side of the Soyuz to which they can anchor themselves. Handholds are placed over the surface of the space station, but not on Soyuz because such protuberances on the craft’s otherwise streamlined surface would overheat from the friction of the Earth’s atmosphere and interfere with re-entry.

Without such handholds, Oberg said, “it takes an astonishing amount of effort simply to maintain your position” in a weightless environment.

The ladder is being sent to the cosmonauts in a regularly scheduled robotic resupply craft that is due to be launched at the beginning of June. Holding onto the ladder, the cosmonauts will be able either to reattach the loose ends of the fiber batting or simply to cut them free.

Surprisingly, the cosmonauts are apparently not going to use their new jet backpacks, successfully demonstrated in February, for the repair.

“They were boasting that it would allow them to inspect and perform maintenance anywhere on the space station,” Oberg said. “Now they are not going to use it. I find that curious.”

The possibility that water could get into the Soyuz craft’s electronics system is disturbing, Oberg said. “But before they unhook the ship for re-entry, they simply turn everything on and check it out,” he said, telling why there is little threat to safety. “If it’s not working, they simply send up a spare (Soyuz) ship. They have one, and have a program to do that.”

That program, called Rescue Soyuz, has a cadre of cosmonauts who could fly up to Mir, pick up the two cosmonauts and return them safely to Earth, he said. Oberg said there is no indication that Soviet officials have taken steps to activate Rescue Soyuz.

Times staff writer Rudy Abramson, in Washington, contributed to this story.