​On December 11, 2022, the Orion capsule passed through the Earth’s atmosphere at a speed of almost 40,000 km/h, leaving the lunar orbit and finally ending up in the waters of the Pacific Ocean, not far from the coast of California. The Artemis 1 mission ended successfully, and everyone celebrated not only the success of the new and controversial SLS rocket, but also the smooth operation of the Orion capsule, which made an autonomous unmanned trip to the Moon and back to Earth. the first test of the ambitious Artemis program.

In the days that followed, NASA engineers began examining the capsule and noticed something they hadn’t expected: The heat shield designed to protect the capsule’s structural integrity was more corrosive than expected, and no one understood why. Now, nearly a year after the Artemis 1 mission ended, the investigation into the Orion capsule’s heat shield is far from over, and no more Orion capsules will be launched until NASA figures out exactly what happened.

The Artemis 2 mission, scheduled for late next year, will take a crew around the moon: Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen will be the first humans to reach the moon since the Apollo 17 crew in 1972. The launch could be delayed until 2025 if the heat shield research drags on as NASA takes all the necessary steps, especially if it’s a manned space flight. NASA said the mission is currently scheduled for late 2024, but they won’t fly until everything is clear.

The four astronauts will not land on the moon, only as part of the Artemis-3 mission, which is currently scheduled for 2025, but there are several signs that lead us to believe that this deadline will not be met: delays in the Starship tests (which are supposed to prove that they can go into orbit and carry propellants in zero gravity), possible delays in the manufacture of suits for extravehicular activities (made by Axiom Space and Collins Aerospace), and now detailed studies of the heat shield of the Orion capsule.

Unlike the space shuttles, which used ceramic plates attached to the fuselage to protect the vehicle, and therefore the crew, from the heat generated during reentry, the Orion capsule uses a so-called ablation shield. This is due to the fact that the vehicle is exposed to higher temperatures, because the entry into the atmosphere from the lunar trajectory occurs at a higher speed than from the orbit of the Earth, where the space shuttles moved. In addition, Orion canisters do not need to be reused, so the ablation shield is the best solution.

Ablative means that some of it is consumed by the plasma that forms around the vehicle, and much of the screen is burned away, but the structure of the vehicle remains intact. In this respect, the Orion capsule resembles the Apollo capsule, which also used this type of ablation shield for safe return to Earth (Starship uses ceramic pads).

The Orion capsule from the Artemis 1 mission arrived safely on Earth and if there were astronauts on board they would not have been harmed, but the problem discovered by NASA is that the shield arrived much more damaged than they initially thought expected, and no one explains why what in. Fortunately, spaceships are designed with a fairly large margin of safety, so there were no problems this time.

The Orion capsule consists of 3 modules: during launch, a Launch Abort System (LAS) fuel rocket is attached to the capsule, which is activated in the event of a launcher disintegration, and the capsule with the crew is removed from danger; the crew module, the only part that returns to Earth at the end of the mission, the one equipped with a heat shield, and the European service module (made by ESA), which provides the electrical current and propulsion necessary for maneuvers into outer space during the mission.

Orion is theoretically a reusable capsule (crew module), but for each mission NASA requests a new capsule from Lockheed Martin. Capsule 002, used in last year’s Artemis-1 mission, is no longer scheduled for spaceflight, and 4 new capsules are in various stages of assembly for Artemis 2, 3, 4, and 5 missions.

Also, it shouldn’t have surprised anyone: any space mission scheduled for the end of the year means it will fly within the next year. This, if you like, is an axiom of space flight.

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