– They didn’t get to land on the moon.

If they had, it’s a good bet the 45th anniversary of Apollo 13 would come and go without anyone noticing. But the magnificent failure is celebrated because figuring out a way to return three men to Earth was as great an achievement as landing on the moon.

In hindsight, Apollo 13 Commander James Lovell said he should have anticipated trouble. On liftoff “everything went perfectly, the countdown went fine,” Lovell said this week. “Except it took off at 1313 Central Standard Time. I should have realized something would go wrong.”

Both surviving astronauts, Lovell and Fred Haise, as well as mission control veterans Gene Kranz, Milt Windler and Bill Reeves held an Apollo 13 reunion here this week.

It might be hard to believe now, but few took notice when Apollo 13 launched on April 11, 1970. Less than a year after Neil Armstrong walked on the lunar surface, the novelty had worn off and the U.S. networks didn’t carry the liftoff live.

But two days into the journey, a routine check of oxygen and hydrogen tanks caused an explosion and suddenly the crew and Mission Control were fighting for the return of the spacecraft.

Reeves told a crowd at a forum here that Apollo 13 lost an engine on liftoff, which could have blown up like the space shuttle Challenger. Fortunately the problem was quickly resolved.

“In previous missions we had about one problem per mission. On Apollo 12, we were struck by lightning on the launchpad,” said Reeves. “People said: ‘Well, Apollo 13’s one problem was the engine.’ ”

Impromptu life raft

It would have been had the oxygen tank not blown up, crippling the command module and forcing the three-person crew to use the two-person lunar module — designed to descend to the moon — as a life raft. At the time of the explosion, Mission Control was in the midst of a shift change, which meant two full flight control teams were on duty.

Reeves, a lunar module flight controller, was getting briefed by his colleague who had the previous shift “when we heard the famous words ‘Houston, we have a problem.’ ”

Mission Control watched in horror as the command module rapidly lost power. They scrambled to come up with procedures to override the computer systems on board to get power from batteries in the lunar module.

They told the astronauts to turn off as many systems as possible to conserve power — the equivalent of only enough power to operate three 100-watt light bulbs.

Still, they were not hopeful.

“We thought — we don’t think we’re going to make it,” said Reeves, explaining that they figured not enough power would likely be left to operate the spacecraft safely back to Earth. “Of course, we didn’t tell the crew that.”

The crew didn’t know what had happened at first, but they knew it was bad because warning lights in the spacecraft illuminated like a Christmas tree.

They could see that two of three fuel cells were lost and they watched the needles on oxygen tanks rapidly drop.

“I looked out the side window and could see gas escaping and knew we were in big trouble,” said Lovell.

The crew knew they had to move quickly into the lunar module. And it was readily apparent that they would not land on the moon.

“I knew that within less than a minute,” said Haise.

Problem-solving on the fly

Windler explained that teams were quickly formed to solve problems such as finding a way to scrub the carbon dioxide from the air the astronauts were breathing.

The biggest challenge was figuring out a way to get the men back by using the moon as a slingshot — a maneuver that obviously was not planned for the mission.

The flight was memorialized in the 1995 movie “Apollo 13,” starring Tom Hanks.

None of the Apollo 13 crew ever landed on the moon. Haise was supposed to command Apollo 19 but NASA ended the program with Apollo 17.

They were incredibly disappointed, but Lovell and Haise now look back four decades later with a different view. They feel fortunate to have been part of such a success.

Had there not been an explosion, Apollo 13 would have landed on the moon, collected some rocks and said forgettable things and simply be a footnote to history.

“There would be no movie and the words ‘Houston, we have a problem’ and ‘failure is not an option’ would not” be a part of the lexicon, said Lovell, adding that the catastrophe brought out the best in teamwork and leadership. “While I was sorry I didn’t land on the moon, it was probably the best thing to happen to NASA.”