Apollo 13 was launched on 11 April 1970. It was the third moon-landing mission in the Apollo programme. It carried a crew of three: Jim Lovell, Commander; Fred Haise, Lunar Module Pilot; and Jack Swigert, Command Module Pilot.
Writing later, Jim Lovell noted: “I had never felt more confident. On my three previous missions, I had already logged 572 hours in space…” But it was not long before disaster struck Apollo 13.
“Hey Houston, we have a problem here”
On its outward journey from Earth, faulty wiring caused an electrical short and a subsequent explosion in one of the oxygen tanks in the Service Module. This crippled the spacecraft, causing depletion of the oxygen supply and the loss of electrical power to the Command Module.
At 200,000 miles from Earth Jack Swigert calmly communicated to Spacecraft Communicator (CAPCOM) Jack Lousma in Houston, “Okay Houston, we’ve had a problem here.” When asked to confirm, Lovell responded: “Houston, we’ve had a problem.”
Over the coming days, the world held its breath. The moon-landing was forgotten as three astronauts and teams on Earth battled to save the mission. The Lunar Landing Module was pressed into service as a “lifeboat,” providing life support and electrical power. It had been tested in this role during training simulations but no one ever imagined it would be needed for real.
However the Lunar Module was only designed to carry two crewmen for a period of about 30 hours. The three-man crew of Apollo 13 would need upwards of 90 hours. Soon dangerous levels of carbon dioxide began to build up inside the spacecraft.
The ground team were forced to improvise a means of filtering the air or the crew would surely die. But they could only use what the crew had available to them. The eventual solution involved, among other things: a roll of grey duct tape; a bungee cord; and a pair of socks.
“The knot tightened in my stomach,” recalled Jim Lovell, “and all regrets about not landing on the Moon vanished. Now it was strictly a case of survival.” But how exactly were the crew going to get back to Earth?
Firstly, they were set on a course for lunar-landing. They needed to correct their trajectory to travel around the far side of the moon instead. It was decided that they would use the Lunar Module’s descent engine for this purpose, something it had never been designed for.
But they faced another problem. They only had sufficient consumables (food, water, air etc) for just over 150 hours. They would need to carry out a second burn of the descent engine during their journey around the moon in order to speed up the return journey to just over 140 hours.
As the Lunar Module passed behind the moon, the crew got their first and last views of its surface on this mission. Lovell even chastised Swigert and Haise for taking photographs when they should have been running through the procedures designed to get them back to Earth. Using the sun to calculate the accuracy of their alignment, the crew carried out a second burn of the descent engines successfully setting them on a course for home.
Before reentering the Earth’s atmosphere the crew jettisoned the damaged Service Module and moved back into the Command Module, which successfully powered up after having been dead for several days.
The crew splashed down in the Pacific Ocean at 1.07pm on 17 April. They were picked up by the aircraft carrier Iwo Jima.
What caused the problem?
Apollo 13’s fate was sealed by an explosion and rupture of oxygen tank no. 2 in the service module. The explosion caused damage to no.1 oxygen tank, which began to lose oxygen.
No. 2 oxygen tank had been installed in Apollo 10 but was removed and damaged before Apollo 10 launched. The damage went unnoticed and this same tank was installed on Apollo 13. The tank showed anomalies during testing and wouldn’t empty properly. Prior to testing, the fixtures in the tank had been altered to allow it to accept 65 volts of power rather than 28 volts. However one part had been overlooked – the heater thermostatic switches.
In an attempt to solve the emptying issues during testing, the excess oxygen was “boiled off” using 8 hours of 65 volt power. This was too much for the switches, which may have welded shut allowing the temperature inside the tank to rise to over 1000 degrees F damaging the teflon insulation on the tank’s wiring.
When the Apollo 13 crew carried out a “cryo-stir” of the tanks 56 hours into their mission, the wires shorted and the teflon insulation caught fire. The resulting pressure in the oxygen tank could do little else but end in an explosion.