Off the coast of Baja California in December 2022, sun sparkled over the rippling sea as waves sloshed around the USS Portland dock ship. Navy officials on the deck scrutinized the sky in search of a sign. The glow appeared suddenly.
A tiny spot at first, it gradually grew to a round circle falling at a great speed from the fringes of space. It was NASA’s Orion capsule, which would soon end the 25-day Artemis I mission around and beyond the Moon with a fiery splashdown into the ocean.
Orion’s reentry followed a sharply angled trajectory, during which the capsule fell at an incredible speed before deploying three red and white parachutes. As the mission finished its trip of over 270,000 miles (435,000 kilometers), it looked to those on the deck of the USS Portland like the capsule had made it home in a single piece.
As the recovery crew lifted Orion to the carrier’s deck, shock waves ruffled across the capsule’s surface. That’s when crew members started to spot big cracks on Orion’s lower surface, where the capsule’s exterior bonds to its heat shield.
The Orion spacecraft splashed down in December 2022, marking the end of the Artemis I mission.
But why wouldn’t a shield that has endured temperatures of about 5,000 degrees Fahrenheit (2,760 degrees Celsius) sustain damage? Seems only natural, right?
This mission, Artemis I, was uncrewed. But NASA’s ultimate objective is to send humans to the Moon in 2026. So, NASA needed to make sure that any damage to the capsule– even its heat shield, which is meant to take some damage – wouldn’t risk the lives of a future crew.
On Dec. 11, 2022 – the time of the Artemis I reentry – this shield took severe damage, which delayed the next two Artemis missions. While engineers are now working to prevent the same issues from happening again, the new launch date targets April 2026, and it is coming up fast.
As a professor of aerospace technology, I enjoy researching how objects interact with the atmosphere. Artemis I offers one particularly interesting case – and an argument for why having a functional heat shield is critical to a space exploration mission.
NASA’s Orion spacecraft had a view of both Earth and the Moon during the Artemis I mission.
NASA via AP
Taking the heat
To understand what exactly happened to Orion, let’s rewind the story. As the capsule reentered Earth’s atmosphere, it started skimming its higher layers, which acts a bit like a trampoline and absorbs part of the approaching spacecraft’s kinetic energy. This maneuver was carefully designed to gradually decrease Orion’s velocity and reduce the heat stress on the inner layers of the shield.
After the first dive, Orion bounced back into space in a calculated maneuver, losing some of its energy before diving again. This second dive would take it to lower layers with denser air as…
