Ever since the first artificial satellite was launched into space in 1957 by the former Soviet Union, hundreds of millions of people have been waiting for the development of a space mission at some time. In the vast majority of cases, the public sees them as a show with an undercurrent of a certain element of risk. Because the truth is that many of the parameters involved in these missions are not what you will usually find on Earth.
The transposition, docking and extraction manoeuvre performed in the Apollo programme was an example of planning by the engineers who designed the flight.
This is where science and engineering come into play. Any space mission is highly complex because it is necessary to anticipate the involvement of countless parameters that will determine every situation that is going to arise until its completion. The skill required by the engineers who design each stage of the journey is extraordinary and we, here on Earth, should be aware of the difficulties and scale of everything that it entails.
Take, for example, one of the most exciting incidents that occurred during the Apollo 11 mission, which is now in its fiftieth anniversary year: the reorganisation of the lunar module and the command and service modules in mid-flight, at a speed approaching 40,000 km/h and without gravity.
At the time of take-off, the Apollo spacecraft was configured as follows, from top to bottom: the command module, CM (in which the crew travelled), the service module, SM (engine, fuel, life support, communications and other components) and the lunar module, LM (spider-shaped vessel, the one that landed on the surface of the Moon).
The lunar module, LM, was protected by a fairing and it was located just below the command and service modules (collectively known as the CSM) and above the second stage of the Saturn rocket (the space launch vehicle).
In mid-flight, en route to the Moon and with almost no gravity, a complex manoeuvre was performed consisting of separating the CSM and rotating it 180º so that it could be connected to the LM in a position that would allow the astronauts to pass from one spacecraft to another via an 80-centimetre hatch. The challenge was not only to perform this manoeuvre (called “transposition, docking and extraction”), but to do so at the aforementioned speed and in a hostile environment that human beings were not used to.
Also bear in mind that, in the middle of the nineteen sixties, the programming and data processing capacity was very limited compared to what we have now. The Apollo spacecraft’s guidance computer had 32 kB of ROM and 2 kB of RAM and it was responsible for performing the calculations necessary to guide the spacecraft and operate the command module’s automatic guidance system. Many of these calculations were aimed at guiding the spacecraft, while many others were intended to provide information to the astronauts, to allow them to perform certain manoeuvres or operational actions, such as this manoeuvre.
Why risk such a delicate movement?
Essentially, it was an engineering design problem in terms of how each stage of the flight had to be carried out. The problem was that, in its launch configuration, the command module had to be located in the highest part of the spacecraft so that it could be attached to the escape tower (or rescue tower). In the event of an emergency on take-off, this “small” rescue rocket was responsible for separating the command module from the rest of the launch vehicle to save the crew.
If the lunar module had been in its final position (in which it was required to reach the Moon’s orbit), the escape rocket would have had to be far larger to be able to carry the additional 15,060-kilogram mass of the LM. Facing this quandary, after three months of calculations, it was assumed that the most viable and possibly least risky solution was for the LM to be located at the bottom and to perform the aforementioned procedure in mid-flight.
The manoeuvre was performed by the CM’s pilot, Michael Collins, although Armstrong and Aldrin had also been trained to do it. According to the flight programme, the astronaut needed approximately one hour to fully complete it, although the time was not critical in this case as they had a little over two days in which to do it, from just after the trans-lunar injection (a propulsive manoeuvre performed from a low circular parking orbit around the Earth, to place a spacecraft on a trajectory towards the Moon).
Consider all of the parameters that must have been involved when performing each of these manoeuvres. We are talking about calculations involving time, space, mass and many laws of physics, and they had to be planned so that they could be performed thousands of kilometres away and in an environment with which humans are unfamiliar. A real feat of engineering.
Approximately 400,000 people worked directly and indirectly to take the Apollo spacecraft to the Moon and bring the astronauts back to the Earth safe and sound. Many of the solutions that they provided to the problems, which were necessary for a mission of this kind, had never been tried before. The engineering work, data analyses, calculations, design, programming and planning were immense because, not only were they firsts, they were needed to successfully complete the mission. It was a matter of state importance.