Artemis II, like the entire program, is a mission led by NASA, the space agency of the United States. But it is also an international effort in which scientists from dozens of countries have participated. A distinguishing element of this mission, moreover, is that for the first time NASA has ceded to a foreign agency the construction of a critical and crucial element for the mission. The European Space Agency has built the Service Module of the spacecraft. The Orion is made up of the crew module (where the astronauts traveled and which they themselves nicknamed Integrity) and the European Service Module, which is responsible for supplying electricity, water, oxygen, and also the propulsion to move the spacecraft. An essential part of the spacecraft that has been built by Airbus and includes a Thermal Control Unit, a very important device that regulates the temperature inside the crew capsule, which has been built at the factory that Airbus Crisa has in Tres Cantos, Madrid.
The most risky moment of the Artemis II mission arrives: entering Earth's atmosphere at 40,000 km/h
A historic mission to the Moon concludes, kicking off the "Artemis generation"
BarcelonaIn all space missions, there is an evident risk to the lives of astronauts. And the most delicate moments are always takeoff and landing. But in Artemis II, NASA's mission that concludes this Friday after ten days of travel, the return to Earth is undoubtedly the most risky moment. To begin with, because during takeoff the astronauts had an ejection system in case of emergency (which would have expelled them to save them in case of an explosion), but above all because the re-entry into the Earth's atmosphere this time presents some extra challenges compared to previous missions.
Artemis II will enter the atmosphere at a higher speed than any other spacecraft: about 40,000 kilometers per hour (the record is currently held by Apollo 9 with 38,000 km/h and returns from the International Space Station usually enter at about 27,000 km/h). This high speed will require Orion's heat shield to withstand temperatures of up to 2,700 °C during re-entry into the atmosphere. And here lies the most delicate point, because this shield was tested in Artemis I (unmanned) and did not perform as well as expected. Some pieces of material detached during entry. At that time, the Artemis II capsule was already built with the same type of shield, and changing it would have significantly delayed the mission.
But after a thorough review of those results, NASA scientists concluded that the problem had been the entry trajectory and decided that the solution was to change it. Artemis I made an entry into Earth with some skips (skip reentry), that is, entering and exiting the atmosphere to avoid reaching excessively high temperatures, but Artemis II will not make these skips but will enter all at once and at a steeper angle. And that is why it will reach the highest speed at which a manned spacecraft has ever entered Earth.
"NASA's crewed spacecraft reliability is very high, probably over 99%, but that means there's always a certain probability that something can go wrong," Xavier Luri, director of the Institute of Space Studies of Catalonia (IEEC) and professor of physics at the UB, explains to ARA.
In fact, a report published by NASA's Inspector General last month indicates that the "accepted risk threshold" for the Artemis missions is a one in thirty probability of losing the crew (that's 3.3%) during the entire mission and one in forty during lunar operations (2.5%). "Risk always exists, but when they are crewed missions, all systems are developed and tested, qualified and overqualified, and then overqualified again, to minimize this risk as much as possible," reassures Andrea Jaime, an engineer assigned as a scientist in the reserve crew for the Hipatia 3 mission, which simulates life on Mars. In fact, the risk for the Apollo missions to the Moon was one in ten.
The re-entry to Earth of the Orion spacecraft carrying the four Artemis II astronauts is scheduled for 1:53 AM on Friday night to Saturday morning, Catalan time (7:53 PM in the eastern United States). Once inside the atmosphere, up to 11 parachutes will be deployed in various phases to gradually reduce the descent speed from 40,000 km/h to 27 km/h at the moment of impact in the Pacific Ocean (splashdown), off the coast of San Diego (California), scheduled for 2:07 AM Catalan time. There, US Marines ships and helicopters will be waiting to pick them up and perform initial medical checks before transferring them to Houston.
This will conclude a historic mission that has succeeded in bringing human beings to the Moon for the first time since 1972. "There are many firsts," summarizes Andrea Jaime: "For the first time, a woman has traveled beyond low Earth orbit (Christina Koch), and for the first time, there was also a woman as launch director (Charlie Blackwell-Thompson), unlike the Apollo missions where only men were in the control room." Also for the first time, a Black man and a Canadian have left Earth orbit: let's remember that until now only 24 astronauts from the Apollo missions had reached this far, all of them white men from the United States.
"We are the Artemis generation"
"As someone who didn't live during the Apollo generation, I believe we are now the Artemis generation and are living through a historic milestone, even though many other news stories in the international context are overshadowing it," says Andrea Jaime.
The four crew members of Artemis II are already the humans who have traveled furthest from Earth in history. On April 6, they reached a distance of 406,771 kilometers, surpassing the record of 400,171 km held by Apollo 13 (1970). Shortly after surpassing that record, they performed the spectacular flyby: flying over the far side of the Moon. "They didn't manage to enter lunar orbit, but rather entered the Moon's gravitational influence area, without being captured," explains Luri, and using the gravitational forces of attraction from Earth and the Moon, they gained momentum to return to our planet, "unlike the Apollo missions which had a thruster" to orbit the Moon and then exit that orbit to return to Earth.
The observation of the far side of the Moon – which has left us with spectacular images – was not an unprecedented event; Apollo astronauts had already been able to observe this part and had also seen the Earthrise behind the Moon. Robotic probes have flown over various areas of the Moon in recent years to collect data, and China even managed to land a probe on this far side of the Moon in June 2024. "The only thing that has happened is that in this mission, photography and live transmission of images has improved tremendously, and even the astronauts were using their mobile phones," recalls Luri. The "glows" or flashes of light they could see on the lunar surface during the 41 minutes of silence – without communication with Earth due to the Moon's blocking – are also not scientifically relevant: it was already known that the lunar surface is constantly subjected to meteorite impacts, as it has no atmosphere to protect it.
So, what was the point of this mission to the Moon? "Apollo was about surviving in space, now Artemis wants to study how to live in space," summarizes the Valencian engineer from Hipatia. The objective was to test the new technologies that are intended to make life outside Earth "comfortable and sustainable." This will include measuring how the body reacts to the high levels of radiation in space, where the protection of the atmosphere disappears and the irradiation from the sun or possible solar storms can be harmful to health, explains Jaime.
"Artemis II should not be looked at in isolation, it is part of the Artemis program," says Luri, who also sees "many parallels with Apollo." "This was a systems test mission, one more step on a longer path that should lead to a continuous human presence in space," agrees the director of IEEC, adding: "The interest in the Moon is as a stepping stone to explore the solar system, this is the key to the Artemis program."