Thousands of kilometers from Earth, an explosion put Apollo 13 on a path to disaster.
For three days, the fate of the mission hung in the balance as NASA figured out how to
get the astronauts home alive.
On April 11, 1970 - NASA launched its third mission to the lunar surface.
The crew of Apollo 13 consisted of veteran Jim Lovell and first time space flyers
Fred Haise and Jack Swigert.
The spacecraft and configuration for this mission were nearly identical
to the one used during Apollo 12.
The Command-Service Module was given the call sign Odyssey while the Lunar Module was dubbed, Aquarius.
While coasting to the moon, the crew docked Odyssey and Aquarius, sealing the tunnel that
connected the two spacecraft.
About 56 hours in, mission control instructed Swigert to perform a procedure called a "cryo-stir”
which helps monitor oxygen levels.
A flip of a switch ended with an explosion.
Back on Earth, mission control was trying to figure out the severity of the situation,
but it was becoming increasingly complicated.
What they didn’t know was that Apollo 13 launched with the makings of a bomb aboard.
The source of the explosion was one of the two cryogenic oxygen tanks
located in the Service Module.
A preflight test damaged insulation on the wiring inside the tank,
but it went unnoticed.
So when Swigert started the cryo stir, one of the damaged wires caused a spark... and boom.
The CSM was quickly losing its power and life sustaining resources.
The damaged oxygen tank caused two out of three fuel cells to shutdown.
That meant that the spacecraft was flying without its main source of electricity and water.
Once mission control figured this out, the moon was no longer an option.
Now, the goal was to salvage enough resources to just get the Command Module back to Earth.
Flight controller, Sy Liebergot, had the unpopular idea to isolate the surge tank - the small
reserve of oxygen that the crew would need for re-entry.
But doing so would require the crew to ultimately power down every system in the Command-Service
Module- making the spacecraft inhospitable.
The Lunar Module would then have to be used as a lifeboat.
This was not a perfect solution.
The lunar module was only designed to support two astronauts for a total of 45 hours as
they traveled from the CSM to the moon and back.
It definitely wasn’t equipped to support three astronauts for the 90 plus hours
needed to get home.
But because the CSM was failing, this was the crew’s only option
if they were going to survive.
First, they had to power up the Lunar Module.
This was supposed to be done using electricity from the CSM which was now on its deathbed.
So hundreds of thousands of kilometers away, the lunar module controllers had to figure
out how to hotwire the spacecraft using diagrams.
The Lunar Module’s main source of power came from these big batteries in the descent stage.
Since they relied on electricity from a switch in the Command Module, the controllers instructed
the crew to reroute electricity from the LEM’s smaller ascent batteries to the power distribution system
This hack energized the relays connected to the descent batteries and powered up the spacecraft.
The crew was safer, now that they were in the Lunar Module.
But NASA still had to figure out how they could get them home.
The explosion happened when Apollo 13 was about 300,000 kilometers from Earth.
It was unknown if the Service Modules propulsion system was damaged, so mission control decided
the best abort trajectory would utilize the moon’s gravity
to guide the spacecraft back to Earth.
Apollo 13 was not on what was known as a “free-return” trajectory.
This essentially meant that the spacecraft would miss Earth by thousands of kilometers.
So to get back on course, the spacecraft needed a big push, and it would have to come from
a relatively small engine in the Lunar Module’s descent stage.
Ordinarily, mission control used software to calculate the length and duration of engine
burns needed to produce a given trajectory.
But no one had ever planned for the LEM’s descent engine to fire while still connected
to the CSM, so engineers had to make new calculations on the spot.
And this was all primarily done without a navigation system.
Due to the loss of power, the astronauts had to instead confirm their location using the sun, stars
and the Earth’s terminator - the line which delineates between night and day.
Adding to this, the crew was facing a fatal buildup of carbon dioxide.
A problem that mission control solved… with Duct Tape.
As the spacecraft approached re-entry, the astronauts weren’t in great shape.
They hadn’t slept in days, they were running out of water and it was about 3 degrees Celsius
in the lunar module.
Despite their exhaustion, it was time to power-up the Command Module - a procedure the crew
would end up doing completely blind.
Since the damaged Service Module was no longer needed to protect the Command Module’s heat
shield, the crew released it into space
and they got a first look at the damage.
[Astronaut] There’s one whole side of that thing missing.
And then, it was time to let go of their life saving Lunar Module.
[Astronaut] Farewell Aquarius, and we thank you.
The crew was so close to home, but there was still a lot that could go wrong.
If the command module’s heat shield was cracked during the explosion,
the astronauts would burn up.
And if the parachutes froze, they would slam into the ocean.
But they just had to trust that mission control would get another miracle.
The world waited as the spacecraft entered Earth’s atmosphere - holding a collective
breath during the next three minutes of radio silence.
[Mission Control] Odyssey, Houston standing by, over.
[Mission Control] Odyssey, Houston we show you on the mains. It really looks great.
After about six sleepless days and a lot of weight lost, the crew safely made it back to solid ground.
Mission control had pulled off the impossible…again.
And while there was a lot to celebrate, NASA now had to figure out how a ticking time bomb
made it onto the Apollo 13 spacecraft in the first place,
and ensure that this mistake would never happen again.
NASA credits much of its successful failure to mission control.
If you want to learn more about the crazy calls they had to make throughout the Apollo
Program, then watch this video here.
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