Of all the space accidents, only one accident is called "successful failure", that is, the Apollo 13 explosion, although the plan to land on the moon failed, but the three astronauts in the joint efforts of thousands of space workers, through the various changes of the danger, and finally successfully returned to the ground, this rescue operation let mankind know what kind of miracles human beings can create.
<h1 class="pgc-h-arrow-right" > the Apollo 13 moon landing program</h1>
After the successful landing of Apollo 11 and Apollo 12 on the moon, in 1970, the United States launched Apollo 13, and the frontmost of the Apollo series of spacecraft was the command module, which was the control center of the spacecraft and the living space of the astronauts. This is followed by the service module, which houses a rocket-engined main engine that acts as the spacecraft's travel power, providing thrust from low-Earth orbit into Earth-Moon transfer orbit and later back from the Moon. At the same time, there is a set of high-gain antennas to enhance communication capabilities.
There is also an electrical system in the Apollo service module, and the Apollo spacecraft uses a complex set of batteries and 3 large fuel cells to power all its equipment, of which the fuel battery will take on most of the power supply tasks during the flight phase.
This fuel cell works by reacting hydrogen and oxygen to produce 1.4kW of 30V DC and a small amount of water in the process. Thus, two large liquid hydrogen tanks (each containing 13 kg of liquid hydrogen) were installed in the service module of the Apollo spacecraft, as well as two liquid oxygen tanks (148 kg of liquid oxygen each inside).
The electricity generated will be used to drive the spacecraft's major systems, and the water generated will be used for the cooling of the spacecraft system, as well as for the astronauts' daily drinking, sanitation, and other uses such as adding water to dehydrated food. And the most convenient way to carry hydrogen and oxygen is to keep them in liquid
Finally, there is the lunar module, which consists of two parts, the descending segment of the lunar module is responsible for landing on the moon, and the ascending stage is the part that leaves the moon. The lunar module has to fly autonomously during the astronaut landing on the moon, so the lunar module has independent power supply, oxygen supply equipment, and engines that can provide power. The descending segment of the lunar module will remain on the moon, and the ignition of the ascending phase of the lunar module will send the astronauts back to orbit around the moon, and will dock with the command module and service module and return to Earth.
Apollo 13 carried three astronauts: Jim Lowell, Jack Swegert, and Fred Hayes. On the third day of Apollo 13's launch, the ground command center issued a command that they wanted astronaut Jack Swift to stir the liquid oxygen tank, why should they stir the liquid oxygen tank? Liquid frozen liquids such as liquid oxygen tend to be 'layered' in a microgravity environment, that is, in the absence of gravity, they tend to form different layers and diffuse around in the space in which they are located.
When this space is only the internal space of the liquid oxygen tank, this layering effect will make it very difficult to measure the amount of liquid inside the liquid oxygen tank, so it needs to be stirred to ensure that the oxygen is evenly distributed, but the moment the button is pressed, the second liquid oxygen tank in the service module explodes.
The serious failure caused the command center to immediately decide to cancel the lunar mission, and the only service propulsion system with a direct U-turn function on the Apollo 13 spacecraft was located in the aft of the service module, and the damage to the service module was unknown, igniting the propulsion system, which may cause an explosion again.
The best escape route calculated by ground personnel
Finally, ground controllers planned to use the moon's gravitational pull to return, that is, to bypass the far side of the moon to put the Apollo spacecraft into return orbit. Lowell and Hayes entered the lunar module and began the rescue work with Swift, who remained in the command module. They first imported the remaining oxygen from the service module into the command module, and then switched the power supply of the command module to the battery in the lunar module.
In order to save as much energy as possible in the lunar module, the astronauts turned off some non-essential equipment, so that the spacecraft entered a "super power saving mode", reducing the power consumption to 1/5 of the normal situation. On the spacecraft, in addition to the three astronauts who need to "drink water", there are water-cooled equipment for various electronic devices. In order to save as much water as possible, astronauts drink only one-fifth of the amount of water they normally drink each day.
On the ground, engineers at NASA and spacecraft contractors work day and night. Every instruction sent to the astronaut requires engineers to design it over and over again and test it on a simulator. This determines the optimal return route. Because of the times, astronauts use a telescope with a similar principle to a sextant to find stars for navigation, and flight control computers will help astronauts figure out the correct direction of the spacecraft. However, the explosion caused the navigation telescope to lose some of its function, and the astronauts finally relied on measuring the direction of the sun to find their way home.
When the spacecraft was only 218 kilometers away from the moon, Lowell activated the landing engine of the lunar module and entered the orbit around the moon. After the spacecraft flew around the moon for 21 hours, Hayes activated the ascending engine of the lunar module, allowing the spacecraft to enter the voyage back to Earth.
Because of the limited power of the lunar module, in order to ensure that they could return to Earth, the astronauts made a dangerous decision, turning off the ship's computers, navigation systems and other electrical equipment, reducing the spacecraft's current consumption to 12 amps---- equivalent to the electricity used by a home mixer. When the heating equipment was turned off, the temperature in the lunar module dropped sharply, and although they put on their astronaut boots and remaining underwear, they were still too cold to sleep.
Because of this, the small air filter in the lunar module could not handle the large amount of carbon dioxide gas emitted by the 3 astronauts, they were in danger of being poisoned to death, and under the guidance of NASA scientists, they made a rough adapter that helped the air filter work more efficiently with some sticky tape, a piece of cardboard torn from the back of the flight manual, and some plastic pieces ripped from their space underwear, and the air in the lunar module finally returned to a clean state from the toxic state.
The astronauts temporarily assembled carbon dioxide filtration devices,
It took a full 4 days for them to finally return to Earth, and when they returned to the ground, the three astronauts lost a total of 31.5 pounds due to dehydration, and Hester was hospitalized for dysuria caused by lack of water.
After returning to Earth, scientists also began to look for the cause of the accident, and eventually, scientists found that the culprit of the accident was actually a liquid oxygen tank, which was a second-hand liquid oxygen tank, which was originally built to be installed on the Apollo 10, which was launched in 1969. But just before the launch of Apollo 10, the liquid oxygen tank was dismantled for maintenance and modification, and there was a drop in the process - the tank once fell from a height of 6 centimeters.
It was also because of this fall that a section of the wire of the liquid oxygen tank was damaged, but the inspectors did not find it, so NASA assigned the second-hand liquid oxygen tank to the service module of Apollo 13 to continue to use.
Technicians again carried out strict inspections of various components before launch, and in one inspection, the liquid oxygen tank was found to be unable to properly empty liquid oxygen (the principle is to fill the gaseous oxygen into the liquid oxygen tank, squeeze all the liquid oxygen out, but due to the damage of a pipeline, it can not be completely discharged). However, the technician did not give up the liquid oxygen tank, but stubbornly wanted to fix it.
In the end, the test team decided to empty the liquid oxygen tank by means of heating. But they made a serious mistake at this point: the liquid oxygen tank itself had a heating device, which was designed to help the flow of oxygen in the piping system through proper heating.
According to the design, the heating device should be powered by the spacecraft's 28V DC power system, but the test team connected it to the 65V ground line for up to 8 hours, and as the voltage increased, the power increased in squares, so the voltage increased from 28V to 65V, and the current through the wire actually increased by 5.38 times.
As a result, the heater switch is burned, and the temperature in the liquid oxygen tank exceeds the specified 20 times, so the insulation layer of the liquid oxygen tank is destroyed and loses its effect.
Therefore, every time the astronauts activate the stirring blade of the liquid oxygen tank, the current will pass through the damaged line, and the lack of protection of the insulation layer will eventually cause an explosion. Scientists did not expect that the accident was actually because of a second-hand liquid oxygen tank.
After this incident, scientists recreated the design of the liquid oxygen tank for Apollo 14, the three astronauts could have landed on the moon, but because of such a small omission, they never returned to the moon, Swigett died of cancer in 1982, and Lowell and Hayes are still alive. This may be the regret of their lives.