April 10, 2020
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11.4.1970: The Apollo 13 crew went through a frightening second.
They were heading for the moon to look for geologically interesting rocks in the crater-rich Fra Mauro highlands.
Apollo 11 showed that the moon landing is technically feasible, Apollo 12 made a precision landing on a predetermined point. Apollo 13 was to be the first in a series of missions that focused on the scientific output, especially geology.
Engine failure!
The startling moment mentioned at the beginning was not (yet) the known misfortune during the flight, but happened just a few minutes after take-off. The Saturn V again developed a “pogo effect”, ie a strong vibration in the longitudinal direction, similar to the first unmanned test flight of the rocket. The effect was reinforced by a “stuttering” fuel pump.
The strong vibrations caused the middle of the five engines of the second stage to shut down a good two minutes early. Fortunately, since Apollo 10, the control software had been adapted so that it left the remaining engines running longer in the event of an engine failure. 35 additional seconds for the second stage and nine seconds for the third led Apollo 13 to reach the planned Earth orbit almost perfectly.
The history
In December 1970, the rocket assembled in the huge “Vehicle Assembly Building” was rolled onto the launch pad on the gigantic “Crawler Transporter”. The command capsule was given the name “Odyssey” and the lunar landing craft was christened “Aquarius”. The start was planned for March 1970, but was later postponed to April. The reason was the budget cut for the Apollo program, which led to the cancellation of the last three missions (Apollo 18-20) and the extension of the schedules for the remaining missions.
After some changes, the crew was determined for Apollo 13 in August 1969: Jim Lovell as commander, Fred “Freddo” Haise as pilot of the Lunar Module (Lunar Module, LM) and Ken Mattingly as pilot of the Apollo capsule (the Command Module, CM).
The astronauts invested over 1000 hours of training specifically for the mission – more than five times the actual mission duration. Almost half of the training took place in the simulator, partly with the involvement of the crew in the ground control center. No crew had ever trained so intensely for the mission.
The doctors sound the alarm
Charlie Duke, a member of the replacement crew, was infected with rubella a few days before the start. He was in contact with Lovell’s crew. Mattingly was the only one not immunized by this. The incubation period is approximately one week. If the disease had broken out at Mattingly, he would have gotten it directly on the moon, with serious consequences for the mission. It was decided two days before the start to replace Mattingly with a member of the reserve crew, Jack Swigert.
In such cases, NASA regulations provided for the exchange of the entire crew, which was hardly possible in view of the short time. The exchange of a crew member from a crew that had been rehearsed for months did not meet with undivided approval. It later turned out that Mattingly was not infected. He was able to fly to the moon with Apollo 16 in 1972.
Moonquake via Saturn V
Two hours after the start, the third stage of Saturn V ignited again and brought the team on the way to the moon. Swigert uncoupled the CM as usual, turned it 180 °, coupled it to the LM still attached to Saturn and pulled it out of the cover.
Then the Saturn V was brought on a collision course towards the moon. When it hit there three days later, it triggered a moonquake that was recorded for three hours by the seismometer left by Apollo 12. But that no longer really interested the public, at that point the catastrophe was already in full swing.
Disinterest on TV
It is estimated that the Apollo 11 landing has followed a billion viewers worldwide. With Apollo 12, there were significantly fewer. And with Apollo 13, the public viewed moon landings as a matter of routine. Not a single TV station broadcast the live broadcast from the space capsule, where Jim Lovell explained it in detail. His wife Marilyn had to go to the control center VIP room to see the broadcast. That changed abruptly after the following events on board made survival of the crew extremely unlikely.
The calm before the storm
A few minutes after the TV broadcast, Apollo 13 was about 330,000 km away from Earth. In the hours before, there had been multiple problems with the pressure display from the oxygen tank. The ground control wanted to try to solve these problems by stirring the tank. This was normally done only once a day to avoid layering of liquid and gaseous oxygen.
Houston: “We’ll have something to do as soon as you have time. We want you to stir the tanks. “
Lovell: “OK, wait a little”.
Haise reached for the switch and flipped it.
The storm
A few seconds later, the crew reported a problem:
Haise: “Okay, Houston, …”
Swigert (interrupts Haise): “I think we just had a problem here”
Houston: “Please repeat”
Lovell: “Houston, we just had a problem. The power supply in circuit B has broken down ”.
…
Haise: “… We had a pretty loud bang here, and at the same time the” Master Alarm “started.”
The events rolled over. Initially, the instruments showed values that made no sense to either the crew or the ground control. But then it became more and more clear that the problem was bigger than feared. Circuit A was also de-energized. Two of the three fuel cells no longer worked. The space shuttle ran on battery, which was actually only intended for re-entry.
So the moon landing was out of reach. Now it was all about saving the lives of the three crew members. What followed was still one of NASA’s success stories.
That night, hundreds of technicians flocked back to the control center to “safely bring Apollo 13 back to Earth,” as President Kennedy promised in his famous speech.
By Alois Regl
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