On this day in 1970: Apollo 13 returns safely to Earth after reporting: “Houston, we’ve had a problem here”

The Apollo 13 mission was meant to be the third lunar landing but the operation was aborted due to serious technical issues, and could have ended in disaster.

The objective was to visit the Fra Mauro crater, to collect samples as NASA believed the material was different to what had been brought back on the 11 and 12 missions.

On April 11 1970 just before 2:15 p.m. Apollo 13 was launched from Kennedy Space Center in Cape Canaveral, Florida with three astronauts on board: Jim Lovell (Commander), Jack Swigert (Command Module Pilot) and Fred Haise (Lunar Module Pilot).

The first signs that all was not well occurred when the second-stage, S-II center engine shut down too early five and a half minutes into flight, but that would be the least of the problems.

The crew settled in for the three-day trip. Amid the tension there was one light-hearted moment. Swigert, drafted in as a late replacement for original crew member Ken Mattingly who had gone down with measles, remembered he had failed to file his tax return and would miss the April 15 deadline. Laughter could be heard back at Mission Control Center in Houston, Texas, who told him not to worry - he’d be granted an extension for being out of the country.

Things took a new turn 55 hours into the mission, when Apollo 13 was about 180,000 nautical miles from Earth. One of the liquid oxygen tanks started to malfunction, giving an off-scale high reading, indicating a failed sensor.

What caused the Apollo 13 mission to fail?

Lovell later recalled that the oxygen tank had originally been constructed for the Apollo 10 mission but had been accidentally dropped, landing on the factory floor. It was repaired, re-serviced and reserved for Apollo 13. “They checked it to see if it could do its job - deliver oxygen to the spacecraft for breathing and making electrical power. Everything worked fine,” he told USA Today in 2014.

“But the tank had a second function. There was a tubing in that tank, so arranged that, after a test, they could remove the liquid oxygen by blowing gases through the fill line and it would be forced out the vent line. That tube had been damaged when the tank was dropped - they did not check whether that would function or not,” he added.

The thermostats inside the oxygen tank should have been upgraded to ones capable of handling 65v power but weren’t. Worse still, a test two weeks before the launch date caused the tank to overheat and melted all the protective wiring, exposing it to further damage.

At 10:08 p.m ET on April 13, as Apollo 13 was preparing to land on the moon, Swigert hit a switch to turn on the heater and oxygen tank 2 blew up.

Swigert relayed a message to Mission Control: “Okay, Houston, we’ve had a problem here.”

The flight controller (CAPCOM) Jack Lousma in Houston replied: “This is Houston. Say again, please.”

Lovell reiterated: “Houston, we’ve had a problem. We’ve had a main B bus undervolt.”

Apollo 13 mission aborted

With both oxygen tanks running low, instruments giving false readings, and stranded in space, Apollo 13 aborted its mission. Lousma told the crew to make their way into the Lunar Module and prepare for an abort maneuver, looping around the moon before beginning a free return course to bring the capsule back to Earth - a journey that would take about four days.

Almost six days after launch on April 17, severely dehydrated but still alive, tragedy turned to triumph as the Apollo 13 command module splashed down safely in the South Pacific Ocean...

“It wasn’t until we were safely on the water and I could see droplets in the window, that I knew that we had come back to Earth. And unless the task force was some place else, I think we were in pretty good shape,” Lovell concluded.

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