Apollo 13: A Mission in Trouble

North America, day and night, satellite image of the Earth
Science Photo Library - NASA/NOAA, Brand X Pictures/ Getty Images

Apollo 13 had problems (real and perceived) from the start. It was the 13th scheduled lunar space exploration mission, scheduled for liftoff at the 13th minute after the 13th hour. The Lunar landing was scheduled for the 13th day of the month. All it lacked was a Friday to be a paraskevidekatriaphobe’s worst nightmare. Unfortunately, no one at NASA was superstitious.

Or, perhaps, fortunately. If anyone had stopped or made changes to the schedule of Apollo 13, the world may have missed one of the greatest adventures in space exploration history.

Problems Began Before Launch

Apollo 13, the third planned Lunar-landing mission, was scheduled for launch on April 11, 1970. There were problems even before the launch. Just days before, Astronaut Ken Mattingly (Thomas Kenneth Mattingly II) was replaced by Jack Swigert when it was learned he may have been exposed to German measles, and did not have the antibodies necessary to be immune (Mattingly never contracted the disease.). Shortly before launch, a technician noticed a higher pressure on a helium tank than expected. Nothing was done about it besides keeping a close watch. A vent for liquid oxygen would not close at first and required several recyclings before it would shut.

The launch, itself, went according to plan, if an hour late. Shortly afterward, though, the center engine of the second stage cut off more than two minutes early. In order to compensate, controllers burned the other four engines an additional 34. Also the third stage engine was fired for an extra 9 seconds during its orbital insertion burn. Fortunately, this all resulted in a mere 1.2 feet per second greater speed than planned.

Smooth Flight - No One Watching

The first part of the flight went fairly smooth. As Apollo 13 entered the Lunar corridor, the Command Service Module separated from the third stage and maneuvered around to extract the Lunar Module. Once this was completed, the third stage was driven on a collision course with the moon. This was done as an experiment and the resultant impact was to be measured by equipment left behind by Apollo 12. The Command Service and Lunar Modules were then on "free return" trajectory, which, in the case of complete engine loss, would slingshot them around the moon and on course back to Earth.

The evening of April 13 (EST), the crew of Apollo 13 had just finished a television broadcast explaining their mission and about life aboard the ship. Commander Jim Lovell closed the broadcast with this message, "This is the crew of Apollo 13. Wish everybody there a nice evening and a, we're just about to close out our inspection of Aquarius and get back to a pleasant evening in Odyssey. Goodnight." Unknown to the astronauts, the television networks had decided that traveling to the moon was such a routine occurrence; none of this was broadcast over the air. No one was watching, though soon the entire world would be hanging on their every word.

Routine Task Goes Awry

After completing the broadcast, flight control sent another message, "13, we got one more item for you when you get a chance. We'd like you to err, stir up your cryo tanks. In addition err, have a shaft and trunnion, for a look at the comet Bennett if you need it."

Astronaut Jack Swigert replied, "OK, stand by."

Moments later, the technicians in flight control heard a disturbing message from Apollo 13. Jack Swigert said, "OK Houston, we've had a problem here.

A Dying Ship And A Crew Fighting For Life

It was three days into the mission of Apollo 13; the date was April 13th, when the mission changed from a routine flight into a race for survival.

The technicians in Houston had also noticed unusual readings on their instruments and were starting to talk amongst themselves and to the crew of Apollo 13. Suddenly, Jim Lovell’s calm voice broke though the hubbub. "Ahh, Houston, we've had a problem. We've had a main B bus undervolt."

This Is No Joke

Immediately after attempting to follow Houston Flight Control’s last order to stir the cryo tanks, Astronaut Jack Swigert heard a loud bang and felt a shudder throughout the ship. Command module pilot, Fred Haise, who was still down in Aquarius after the television broadcast, and mission commander, Jim Lovell, who was in between, gathering cables up, both heard the sound, but at first thought it was a standard joke previously played by Fred Haise. It was no joke.

Seeing the expression on Jack Swigert’s face, Jim Lovell knew immediately that there was a real problem and hurried into the CSM to join his Lunar module pilot. Things did not look good. Alarms were going off as voltage levels of the main power supplies were dropping rapidly. If power was completely lost, the ship had a battery backup, which would last for about ten hours. Apollo 13, unfortunately, was 87 hours from home.

Looking out a port, the astronauts saw something, which gave them another concern. "You know, that's, that's a significant G&C. It looks to me looking out the ahh, hatch that we are venting something." A pause… "We are, we are venting something out the, into the ahh, into space."

From Lost Landing to Struggle for Life

A momentary hush fell over the Flight Control Center in Houston as the new information sank in. Then, a flurry of activity began, as the technicians all conferred, and other experts were called in. Everyone knew that time was critical.

As several suggestions for correcting the dropping voltage were raised and tried unsuccessfully, it quickly became apparent that the electrical system could not be saved.

Commander Jim Lovell’s concern was continuing to rise. "It went from 'I wonder what this is gonna to do to the landing.' to 'I wonder if we can get back home again.'" The technicians in Houston were having the same concerns.

The call was made that the only chance they had of saving the crew of Apollo 13 was to shut down the CM entirely to save their batteries for reentry. This would require the use of Aquarius, the lunar module as a lifeboat. A module equipped for two men for two days would have to sustain three men for four.

The men quickly powered down all the systems inside Odyssey and scrambled down the tunnel and into Aquarius. The crew of Apollo 13; Jim Lovell, Fred Haise, and Jack Swigert all hoped it would be their lifeboat and not their tomb

A Cold and Frightening Journey

There were two components to the problem; first, getting the ship and crew on the fastest route home and second, conserving consumables, power, oxygen, and water. However, sometimes one component interfered with the other.

Conserving Resources; Preserving Life

As an example, the guidance platform needed to be aligned. (The venting substance had played havoc with the ships attitude.) However, powering up the guidance platform was a heavy drain on their limited power supply.

The conservation of consumables had already begun with the shutting down of the Apollo 13 CM. For most of the rest of the flight, it would only be used as a bedroom. Later, they powered down all of the systems in the LM except those required for life support, communications, and environmental control.

Next, using precious power they could not afford to waste, the guidance platform was powered up and aligned.

Mission control ordered an engine burn that added 38 feet per second to their velocity and return them to a free-return trajectory. Normally this would be a fairly simple procedure. Not this time, however. The descent engines on the LM were to be used instead of the CM’s SPS and the center of gravity had changed completely.

At this point in time, had they done nothing, their trajectory would have returned them to Earth approximately 153 hours after launch. A quick calculation of consumables gave them less than an hour of consumables to spare. This margin was far too close for comfort.

After a great deal of calculating and simulating at Mission Control here on Earth, it was determined that the Lunar Module’s engines could handle the required burn. So, the descent engines were fired sufficiently to boost their speed up another 860 fps, thus cutting their flight time to 143 hours.

Chilling Out Aboard Apollo 13

One of the worst problems for the crew during that return flight was the cold. Without power in the CM, there were no heaters to maintain cabin temperatures. The temperature in the CM dropped to around 38 degrees F and the crew stopped using it for their sleep breaks. Instead, they jury-rigged beds in the warmer LM, though warmer is a relative term. The cold kept the crew from resting well and Mission Control became concerned that the resulting fatigue could keep them from functioning properly.

Another concern was their oxygen supply. As the crew breathed normally, they would exhale carbon dioxide. Normally, oxygen-scrubbing apparatus would cleanse the air, but the system in Aquarius wasn’t designed for this load, there was an insufficient number of filters for the system. To make it worse, the filters for the system in Odyssey were of a different design and not interchangeable. The experts at NASA, employees and contractors, engineered a makeshift adapter from materials the astronauts had on hand to allow them to be used, thus lowering the CO2 levels to acceptable limits.

Finally, Apollo 13 rounded the Moon and began its journey home to Earth. However, the crew’s troubles were not over

Farewell, Aquarius, We're Going Home

The crew of Apollo 13 had survived some type of explosion which resulted in lost power capabilities and loss of oxygen. With the help of experts on Earth, they had moved aboard the Lunar Module, corrected their trajectory, survived the cold and a buildup of CO2, and shortened the trip home. Now, they had a few more hurdles to overcome before they could see their families again.

A Simple Procedure Complicated

Their new re-entry procedure required two more course corrections. One would align the spacecraft more towards the center of the re-entry corridor, while the other would fine tune the angle of entry. This angle had to be between 5.5 and 7.5 degrees. Too shallow and they would skip across the atmosphere and back into space, like a pebble skimmed across a lake. Too steep, and they would burn up on re-entry.

They could not afford to power up the guidance platform again and burn up their precious remaining power. They would have to determine the attitude of the ship manually. For experienced pilots, this would normally not be an impossible job, it would just be a matter of taking star sights. The problem now, though, came from the cause of their troubles. Ever since the initial explosion, the craft had been surrounded by a cloud of debris, glittering in the sun, and preventing such a sighting. The ground opted to use a technique worked out during Apollo 8, in which the Earth’s terminator and the sun would be used.

"Because it was a manual burn, we had a three-man operation. Jack would take care of the time," according to Lovell. "He'd tell us when to light off the engine and when to stop it. Fred handled the pitch maneuver and I handled the roll maneuver and pushed the buttons to start and stop the engine." The engine burn was successful, correcting their re-entry angle to 6.49 degrees.

A Real Mess

Four and a half hours prior to re-entry, the Apollo 13 crew jettisoned the damaged Service Module. As it slowly receded from their view, they were able to make out some of the damage. They relayed to Houston what they saw. "And there's one whole side of that spacecraft missin'. A whole panel has blown out. Almost from the base to the engine. Its really a mess."

Later investigaion said the cause of the explosion was exposed electrical wiring. When Jack Swigert flipped the switch to stir the cryo tanks, the power fans were turned on within the tank. The exposed fan wires shorted and the teflon insulation caught fire. This fire spread along the wires to the electrical conduit in the side of the tank, which weakened and ruptured under the nominal 1000 psi pressure within the tank, causing the no. 2 oxygen tank to explode. This damaged the no. 1 tank and parts of the interior of the service module and blew off the bay no. 4 cover.

Two and a half hours before re-entry, using a set of special power-up procedures relayed to them by Mission Control in Houston, the Apollo 13 crew brought the CM back to life. As the systems came back on, everyone aboard, in Mission Control, and around the world breathed a sigh of relief.


An hour later, their Lunar Module lifeboat was also jettisoned. Mission Control radioed, "Farewell, Aquarius, and we thank you." Jim Lovell later said of her, "She was a good ship."

The Apollo 13 Command Module, carrying its crew of Jim Lovell, Fred Haise, and Jack Swigert splashed down in the South Pacific on April 17 at 1:07PM (EST), 142 hours and 54 minutes after launch. It came down within sight of the recovery ship, the USS Iwo Jima, who had the crew aboard within 45 minutes.

The crew of Apollo 13 had returned to Earth safely, completing one of the most exciting adventures in the history of space exploration