The engineers' work to save astronauts Jim Lovell, Fred Haise and Jack Swigert was to be recognized Tuesday by a company that runs an engineering search engine. Engineers, astronauts and flight controllers were expected for a ceremony at the space center.

"It was actually a fair bit of very, very quick engineering work that they had to radio up," said John Schneiter, president of GlobalSpec, the New York-based company planning to honor the engineers. "They had to make it right the first time. ... It had to work and son of a gun, it did."'

Sunday marked the 35th anniversary of the spacecraft's return to Earth. It was crippled by an oxygen tank that overheated and exploded, raising concerns the carbon dioxide the astronauts expelled from their lungs would eventually kill them. Two of Apollo's three fuel cells, a primary source of power, also were lost.

Ed Smylie, who oversaw NASA's crew systems division in 1970 and is now an aerospace consultant, is glad the engineering side of the mission will be recognized.

"The guys in the front room are the ones who are in the front lines and get a lot of attention," he said. "Those of us who are in the back room don't get a lot of attention."

Smylie said he was at home watching television when he learned there was a problem aboard Apollo 13. Within minutes, he was at the space center trying to come up with a solution to save the crew.

The crew had lithium hydroxide canisters to cleanse their spacecraft of carbon dioxide, but some of the backup square canisters were not compatible with the round openings in the lunar module, where the astronauts had moved from the command module to conserve power for re-entry.

"This was equivalent to being on a sinking ship," Schneiter said. "In this case, you are on a ship that was mortally wounded, and you were simply not going to be able to breathe in a couple of days."

Smylie and other engineers soon had a proposed solution to retrofit the canisters, but it took another day or two to build a mock-up and get instructions to the crew.

Among the biggest concerns was whether the astronauts had duct tape, Smylie said. He later learned duct tape was commonly used on the spacecraft to clean filters and for other tasks, such as taping bags of food to heating lamps.

"I felt like we were home free," he said. "One thing a Southern boy will never say is 'I don't think duct tape will fix it.'"

While those within the agency may have been concerned, no one showed it, he said.

''If you saw the movie, it wasn't like that,'' Smylie said, adding there wasn't any hollering and screaming. ''Everything is pretty calm, cool and collected in our business.''

Haise said the device was tricky to build but it worked.

''Had someone not figured that out, we wouldn't have survived,'' he said.

The astronaut said he and his crew members remained calm despite the numerous problems they faced. ''We had confidence the right people had been brought in and would work it out,'' he said.

Looking back, Smylie said, Apollo 13 turned out to be one of the space program's proudest moments.

''What could have been a horrible disaster turned out to be a great achievement,'' he said.