GoKawiilFor NASA astronomers, engineers and mission managers, the most critical point of a trip to the moon is not the maneuver around the satellite but rather a much less moment: reentry. That final effort, which lasts less than 20 minutes, may completely redefine the Artemis program.
The four Artemis II astronauts are the first to return to lunar orbit after 50 years. They are also the first to return to Earth in a new spacecraft that will reach about 11 kilometers per second—32 times the speed of sound, or nearly twice the speed of a traditional reentry from the International Space Station. During this final stage, the Orion capsule will pass through a plasma cocoon where the temperature reaches 2,700 degrees Celsius (4,900 Fahrenheit) due to friction with the atmosphere.
This is what a capsule looks like after it returns to Earth from the International Space Station. Photograph: NASA/Bill Ingalls/Getty Images
For about six minutes, the spacecraft will lose communication with NASA, endure deceleration forces of 3.9 g’s, and rely entirely on the heat shield, which is made of Avocat, a material designed to burn in a controlled manner. That shield is literally the barrier separating the crew from the incandescent exterior.
This is the second time Orion has faced that test. On its first attempt, it did not pass at all. During Artemis I, the capsule returned from the moon orbit, uncrewed, to test its heat shield under real-world conditions. Instead of showing uniform wear, the Avcoat burned unevenly and shed more material than expected, leaving erosion patterns that did not match what engineers had modeled.