The famous phrase, “Houston, we have a problem,” just turned 50 years old on April 13, and although a large majority of people in the world have heard this phrase at least once in their lives, many people still do not know exactly what happened that day and what the problem was that was communicated to Houston at that time.
The Apollo 13 mission began on April 11, 1970, when at 19:13 (GMT) it took off from launch area 39A at the Kennedy Space Center in Florida. The mission: to return to the Moon after the successful and historic Apollo 11 moon landing and the subsequent Apollo 12 mission landing.
Houston, we have a problem
The mission of Apollo 13 (yes, the same one that a rather boring movie was made in 1995 with Tom Hanks), was to return to the Moon once again and, in fact, it was a mission that started without any kind of Setbacks, as Apollo 13 commander James A. Lovell himself explained to National Geographic, explaining that at any one time, at the mission’s control center, it was all nothing but boredom.
For this trip to the Moon, a Saturn V rocket was used as the launch vehicle, weighing about 950,000 kilograms. It was in fact the heaviest vehicle NASA had ever sent into outer space up to that point, largely because it carried an extra load of propellant to carry out various missions that would be developed and would need much more fuel.
As in previous missions, there were several lunar modules, including the command module, the service module (called Odyssey) and the lunar module (LM-7, called Aquarius). The engines of the first phase would generate a total thrust of 440,000 newtons, slightly less than the thrust generated in the Apollo 12 mission, but still meeting the minimum requirements of this new mission.
The crew included, in addition to Commander Lovell, the pilots John L. “Jack” Swigert Jr. (from the command module) and Fred W. Haise Jr. (from the Lunar Module). The three had their sights set on the Fra Mauro lunar region until, as NASA reports, five and a half minutes after takeoff the crew felt a small vibration, and about 55 hours later they warned Houston that they had a problem, exactly at 21:08 local time on April 13, 1970.
And then you heard “boom”
As explained by NASA itself, the problems began at take-off when the central engine of the second phase (S-II) was shut down about two minutes ahead of schedule. This was due to the fact that very violent oscillations were occurring due to unstable combustion of the propellant carried by the Saturn V, which caused variations in the pressure in the chamber and triggered that automatic safety mechanism that “turned everything off” if necessary.
This meant that, in compensation, the four external engines and the third stage (S-IVB) had to be run for longer (34 seconds and 9 seconds more than expected respectively) in order to put Apollo 13 into orbit. After this, the mission continued without further problems until they found themselves about 325,000 kilometres from Earth, just a few minutes after making a televised transmission.
At that time, a pressure sensor in one of the service module’s oxygen tanks appeared not to be working properly. To try and fix this, the astronauts were asked to activate the fans that removed the liquid oxygen because this allowed for more accurate readings, but 95 seconds after the fans were activated, the astronauts heard a “pretty large bang”.
The explosion was accompanied by fluctuations in electrical current and communications with the Earth were lost for just under two seconds. The system automatically recovered when the high-band directional antenna was changed from narrowband to broadband, and the famous communication was broadcast.
“Houston, we’ve had a problem. We’ve had a Main B Bus undervolt”. James A. Lovell.
Tank number two
Tank number 2, with serial number 10024X-TA0009, is a tank that was previously installed in the service module of the Apollo 10 mission, and when an attempt was made to apply a modification to it, it was damaged and had to be returned to the workshops to be checked and repaired.
What happened with this tank is that it did not drain correctly, and after some discrepancies between the engineers in charge, it was decided to resort to heating the excess oxygen with an electric heating system, which finally “worked” and achieved the dissipation of the oxygen, but without solving the problem of draining the tank. Despite this, it was considered that the solution adopted would serve to go into space, and all this happened just a few weeks before take-off.
The problem itself was that the heating systems had been upgraded to operate at 65 volts instead of the previous 28 volts normally used, but the thermostats that controlled these systems were not replaced to be functional with that change. This caused the wiring to be damaged in the last tests, and the thermostat switches to melt when high temperatures were reached for more than eight hours, not to mention that aluminum and Teflon were used to insulate the electrical parts, which are highly flammable in the presence of pure oxygen. In short, the tank number 2 that would go into space was a time bomb ready to explode and NASA did not yet know it.
Once in space and after the accident occurred, abnormal tank level readings were recorded: tank no. 1 was gradually decreasing while tank no. 2 was completely empty. When Lovell looked out of one of the hatches of the space module, he said:
“I think by looking out the hatch we’re losing something, we’re releasing something into space.” That something that Lovell saw was nothing more and nothing less than the oxygen that he and his companions needed to be able to breathe.
Oxygen is not only a precious commodity for humans in space: the fuel cells would also need it to function, so once tank number one was completely empty these cells would also stop functioning. So the only source of energy for the control and service module would be the batteries and the oxygen reserve tank of the lunar module, where the astronauts had to move.
Lovell would tell National Geographic that this oxygen reserve served as a lifeline for the astronauts, but that they made great sacrifices to conserve both water and electricity: “We reduced the daily water ration to 30 milliliters, one-fifth of normal intake. We drank fruit juices and ate hot dogs and other water-rich foods“. They still suffered from dehydration and weight loss, and could not sleep because of the cold, as they had no source of heat when the electrical systems were turned off, leaving them at a temperature of less than 3 degrees Celsius.
The other problem, and perhaps one of the most serious, was the very breathing and exhaling of carbon dioxide. The module they were in only had lithium hydroxide cans (which were used to clean the CO₂ of the lunar module) to sustain two people for two days and they were going to need much more than that to be able to survive the three crew members for four more days.
In the midst of this life-and-death situation, Houston came up with a solution to the problem: adapting the lithium hydroxide cans on the lunar module to the command module using plastic bags, cardboard and duct tape. This saved the lives of the astronauts, since the lithium hydroxide cans on the command module did not fit on the lunar module because of their different shape.
When they could breathe, they still had to go home
With the spacecraft “at half gas”, returning to Earth was not going to be an easy task, especially since the Lunar Module’s navigation system was not prepared for this situation. Under normal conditions, the alignment of the spacecraft with a star would have been checked using the optical alignment telescope (the AOT), but the problem was that there were hundreds of “false stars”, as Lovell called the metal debris that accompanied the spacecraft’s trajectory and shone in the sunlight.
Hence, it was not possible to differentiate the real stars from the debris, except for the Sun itself. And of course, that being the only viable option, Houston chose it to verify the accuracy of the spacecraft’s alignment so that it could enter the Earth again without endangering the lives of the astronauts.
“I turned the spacecraft around as Houston had indicated. If our alignment was accurate, the Sun would be centered on the sextant. The alignment proved to be less than half a degree of accuracy, which was good enough for everyone”. James A. Lovell.
When they reached the Earth’s atmosphere, they had to return to the command module because the lunar module was not in condition to withstand that final leg of the journey, and after separating it from the command module, they landed what was left of Apollo 13 to the southeast of American Samoa. It was on April 17, 1970, at 18:07 (UT), when this accidental mission that lasted 142 hours, 54 minutes and 41 seconds was terminated and would go down in history as a “successful failure”, for all the experience that was extracted from that rescue.
From that time until now, the famous “Houston, we have a problem” has never been heard again.