• November 28, 2020
 Amy’s Everyday Astronomy: Apollo 13 – Alone Together

Photo courtesy NASA

Amy’s Everyday Astronomy: Apollo 13 – Alone Together

During this time of quarantine and social distancing, it’s hard for many of us to stay indoors without going stir crazy. One thing we have going for us is that we are alone together.

We have social media and cell phones for connection with others. There is internet to provide us with entertainment. We can still go outside to our yards and feel the fresh air on our skin.

But 50 years ago, three men were not so lucky. They were stranded inside a small metal can, with limited air and no power. As the temperature dropped inside their spacecraft, they wondered if they would ever again be able to walk outside and feel the fresh air upon their skin.

On the afternoon of April 11, 1970, Apollo 13 launched from Kennedy Space Center. Set to be the third manned attempt to land on the moon, everything about the mission seemed to be running smoothly. At 55 hours and 46 minutes, the crew had just finished a 49-minute TV broadcast.

Less than ten minutes later, oxygen tank number 2 blew up, causing the number 1 tank to also fail. The command module’s normal supply of electricity, light, and water was lost, leaving the crew stranded without these things at about 200,000 miles from Earth.

As the warning light came on in the module at 9:08pm on April 30th, John Swigert uttered the famous phrase: “Houston, we’ve had a problem here.”

Swigert was the backup command module pilot who replaced Ken Mattingly after he’d been exposed to German Measles.

Thirteen minutes after the explosion, James Lovell noticed a gas, later determined to be oxygen, venting out into space. Down to their last 15 minutes of power in the command module (CM), they were forced to evacuate into the lunar module (LM).

They had plenty of oxygen in the LM, so they moved the consumables over while Swigert performed the last chores aboard the CM. The main issues they had were battery life and water.

There was 2,181 ampere hours in the LM batteries. This would not be enough to get the crew home. Ground controllers carefully worked out a procedure where the CM batteries were charged with LM power. All non-critical systems were turned off, which reduced energy consumption to 1/5. This resulted in a mere 20% of LM electrical power left.

This would be the only power available to land safely back on Earth.

It was estimated that the crew would run out of water about five hours before they reached Earth. This forced them to cut down their ration to just 6oz per day which was 1/5 of the normal intake.

To make up the difference, they used fruit juices and ate wet food packs. Despite these efforts, the crew became dehydrated throughout the flight and set a record that stood up throughout the Apollo program.

Overall, the crew lost a total of 31.5lbs, nearly 50% more than any other crew.

The next issue they ran into was the removal of carbon dioxide. This gas, normally exhaled by humans with every breath we take, was filling the air and slowly poisoning the men.

The LM was designed to support two men for two days and was now supporting three men for about four days. Though they had enough lithium hydroxide canisters aboard for removing the carbon dioxide, these canisters were square and not compatible with the round openings of the LM system.

Mission control got to work and figured out a way for them to adapt the canisters using plastic bags, carboard, and tape, which were all materials the men had on board.

Another big hurdle for the crew was that of return trajectory. Before the explosion, Apollo 13 had made a normal midcourse correction that put them on a Lunar landing course. This meant that the men would have to slingshot around the moon in order to align with Earth for the return trip.

Just before reaching the moon, ground control computed a 35-second burn and fired it 5 hours after the initial explosion. A second burn was computed 2 hours after rounding the far side of the moon, this time a long 5 minute burn.

Typically, alignment procedures use an onboard sextant device, called the Alignment Optical Telescope (AOT), to find a suitable navigation star. Due to the explosion, however, a swarm of debris from the ruptured service module made it impossible to sight real stars.

An alternate procedure had to be developed to use the sun as an alignment star. Lovell rotated the spacecraft to the attitude Houston had requested. He then looked through the AOT and saw the sun right where expected. This alignment proved to be less than ½ degree off, which allowed them to complete the 5 minute P.C.+2 burn with assurance. This cut the total time of their voyage down to about 142 hours.

The last, and easily the most remarkable achievement of mission control, was in quickly developing procedures for powering up the CM after its long, cold sleep.

Flight controllers worked hard and were able to develop these unprecedented procedures in 3 days, rather than the 3 months it would normally have taken. The CM was cold and clammy at the start of power-up.

Everything was covered in water droplets, and it was suspected that the same conditions might exist behind the panels. The fear of short circuiting was high. However, thanks to safeguards put in place after the Apollo 1 fire in January 1967, no arcing took place.

The crew was able to power up for landing while staying within the 20 ampules of power left.

To safeguard the heat shield from being damaged by the cold of space, the service module wasn’t shed until just 4 hours before landing. Three hours later, the crew abandoned the LM and splashed gently down into the Pacific Ocean near Samoa. The mission was deemed a successful failure.

In the report of the Apollo 13 Review Board, it was stated:

Perfection is not only difficult to achieve; it is difficult to maintain. The imperfection in Apollo 13 constituted a near disaster, averted only by outstanding performance on the part of the crew and the ground control team which supported them.

These men buried their fear and with the enduring support and hard work of those still on the ground, performed above and beyond to ensure they would make it home.

Indeed, the lesson learned is that when we all work together to support one another, we can accomplish the seemingly impossible.

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If you have any questions about anything I’ve talked about here, or another science topic, feel free to send me an email at acooley@epheraldpost.com.

To listen to past episodes, click here.  To view past articles and content, click here.

Amy Cooley

A native El Pasoan, Amy Cooley attended Parkland High School before beginning her studies in physics at EPCC. With her love of dark skies increasing, she transferred to New Mexico Tech University where she earned her degree in Astronomy. Moving back to El Paso in 2008, she now wants to share her love of the cosmos with the city she calls home.

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