More than 50 years ago, NASA made history by taking the first humans to the surface of the Moon and bringing them back safely. The first manned landing on our natural satellite, carried out during the Apollo 11 mission in 1969, required 10 training missions, the work of more than 400,000 engineers, scientists, technicians and a budget that exceeded several billion dollars. But, after all, how did the astronauts get to the Moon? And more importantly: how did they get back to Earth?
The Apollo program had a total of 17 missions. The first was, basically, tests of the equipment, and five flights successfully landed (that is, lunar landings). The first landing occurred with the Apollo 11 mission, launched on July 16, 1969, when astronauts Neil Armstrong and Buzz Aldrin walked on the Moon. After them, other men were also on our natural satellite, carrying out studies and collecting samples that continue to be analyzed by scientists until today and yielding scientific discoveries. In total, 12 astronauts went there - for now.
To accomplish all of this, NASA developed the spacecraft for the Apollo program, consisting of three parts: first, there was the command module (CM), which contained the flight controls and crew quarters, and the services module (SM) that provided propulsion and the necessary systems for the ship. When attached to each other, they were called CSM. Finally, there was also the lunar module (LM), which held up to two crew members and was used to take them to the lunar surface, support them and take them back to the CSM.
 |
| Indication of the services module, command and lunar (Image: Reproduction / NASA) |
Some vehicles were used to carry out the program's launches, such as Saturn I and Saturn IB, composed of two stages and used during manned and unmanned orbital flights in Earth orbit. Saturn V, the most powerful rocket ever launched to date with its three stages and 110 m high, was used in flights made in Earth orbit and in missions to the Moon of the Apollo era.
How the astronauts went to the moon and then returned home
In order to achieve the goal of taking a person to the Moon and bringing them back safely by the end of the 1970s, NASA needed to analyze some strategies. Among the options, the one chosen was the Lunar Orbital Encounter (LOR), which, in general, consists of launching a rocket towards the lunar orbit, descending a lander to the surface and maintaining a ship in orbit. This would have to be attached to the ship that went to the lunar surface for the crew to be able to return to Earth.
 |
| John Houbolt explaining the LOR concept for lunar landing (Image: Reproduction / NASA) |
This would be a viable option with the Saturn V rocket, but it also offered the risk that, in case they were unable to meet the module that remained in orbit, the astronauts would be left to their own devices, because they could not be rescued. The idea was created by Yuri Kondratyuk and was presented by engineer John Houbolt, who proposed to NASA that lunar missions be done by sending a ship to orbit the moon and another to land on the lunar surface.
Then, the two vehicles would meet in orbit before returning home. For that, it was necessary that each of the program's missions performed a very complex sequence of maneuvers at some level close to perfection - even Apollo 13, which ended up known as "NASA's successful failure", was an example of the accuracy of the work between the astronauts and the mission control center.
Putting it all into practice
Take the Apollo 11 mission again as an example. Two hours and 44 minutes after launch, the S-IVB stage of the rocket made a brief burn, which positioned the mission in translunar orbit. Then, the Columbia service and command module (CSM) separated from the stage, which had the adapter with the Eagle lunar module (LM). Subsequently, the CSM was coupled to the LM, followed by the separation of the S-IVB stage and the injection into the heliocentric orbit.
 |
| Representation of the maneuver in which the CM is turned to capture the LM (Image: Reproduction / NASA) |
Three days of travel later, the astronauts, the Columbia command module, the service module and the Eagle lunar module performed the first insertion maneuver into the lunar orbit. Michael Collins, who served as the pilot of the command module, repositioned the LM so that the other two were aligned correctly. The next day, Buzz Aldrin and Neil Armstrong went to the LM to descend to the lunar surface.
Meanwhile, Collins remained in the command module, orbiting the Moon. The LM had two stages: the descendant had a rocket engine in its structure to help reduce speed during the descent and was kept on the lunar surface at the end of the activities. over there. After exploring the lunar surface and collecting samples, the pair returned to the upper part of the LM, where the ascending stage was, which had a crew compartment and a rocket engine.
 |
| The Eagle lunar module in the lunar orbit landing configuration (Image: Reproduction / NASA) |
To reconnect with the command module, the astronauts activated the engine of the ascending stage on the Moon and took off, leaving the descendant behind. Then, the ascending stage coupled with the command module, which was in lunar orbit. After the astronauts entered the command module to return home, the ascending stage was programmed to crash into the lunar surface and be destroyed.
And how does the ISS round trip work?
Since the end of the Apollo program in 1975, no astronaut has been sent to the Moon so far - which could change in the not-so-distant future with initiatives like NASA's Artemis program, which aims to take the first woman and the next man over there in 2024. On the other hand, there are crews who regularly take turns staying onboard the International Space Station (ISS), which orbits the Earth at about 400 km altitude.
 |
| The Crew Dragon spacecraft attached to the ISS (Image: Reproduction / NASA / Johnson Space Center) |
In this case, the ISS return process is a little different. Consider, for example, the Demo-2 mission, in which astronauts Bob Behnken and Doug Hurley went there with the SpaceX Crew Dragon: before the return process begins, ground crews select landing locations that they can offer the greatest number of return opportunities in the event of a change in the climate, and also consider the places that require the shortest total time between decoupling and landing (when the ship falls into the water and not on the ground).
At the end of the mission, the astronauts said goodbye to their colleagues on board and went to the ship, nicknamed Endeavor, which has remained attached to the ISS since arriving there. Then, the hooks that hold the Crew Dragon came loose, followed by two short shots from the engine to separate the ship from the station. As soon as it is released, Crew Dragon automatically performs four other burns, which leave it in the right direction to return home. Shortly before the final burn, Crew Dragon separates from its cargo compartment, which is burned during re-entry into the atmosphere.
The last stage is orbit burning, which leaves the vehicle in orbit with the correct trajectory for landing. During re-entry, which is one of the most complex stages of the mission, the astronauts are incommunicado for about six minutes, traveling at a speed of 28,000 km / h. After entering the terrestrial atmosphere, two parachutes are opened to help stop the ship, until it falls into the ocean, where there are already vessels ready to recover it with the protected crew inside. Generally, the average time for decoupling and landing itself can vary from six to up to 30 hours, depending on the position of the ISS in relation to the place where the ship should descend.
Source: NASA ( 1, 2), BBC, Space.com, PopSci, Business Insider
0 Comments