Artemis II to put new reentry plan to the test after heat shield crack

EDWARDS, Calif. — Artemis II astronauts are scheduled to return from their mission on Friday. moonshot. When they do this, they will crash into Earth’s atmosphere at more than 32 times the speed of sound, and they will do so using a re-entry technique that has not yet been tested in real-world scenarios.

In 2022, NASA sent the uncrewed Artemis I test mission to the moon. The capsule, which penetrated the Earth’s atmosphere on its return, was damaged unexpected damage This prompted NASA scientists to rethink what was needed to keep Artemis II astronauts safe as they headed back home.

Tons of work has been done to prepare for this moment – but the truth is that scientists won’t know exactly how the heat shield will behave until they test it in a bona fide reentry.

That’s why a team of scientists and test pilots from NASA and the Department of Defense are poised to collect detailed data on how the heat shield is performing as the capsule hurtles through the sky; As the capsule heads toward the sky, it transforms the atmosphere around it into a bright fireball half as hot as the sun’s surface before splashing off the coast of San Diego.

Test pilots assigned to Southern California military bases will take turns chasing the capsule in a complex, high-speed powertrain: first a NASA business jet, then a Navy surveillance plane, then another NASA jet, and finally a NASA weather research plane. Teams on the ground will monitor the Artemis II capsule and send accurate speeds and coordinates to test pilots who follow the fireball across the sky. Meanwhile, the researchers behind the planes will follow the capsule with telescopes and sensors.

Center Director Bradley C. Flick (left) gives a high five to project manager Robert Navarro at NASA Armstrong Flight Research Center at Edwards Air Force Base on March 18.

(Genaro Molina / Los Angeles Times)

“Threading the needle multiple times is an exciting task,” said Robert Navarro, project manager at NASA’s Armstrong Flight Research Center in Edwards, Calif., who was responsible for the critical third part of the relay. “Because of the short time period they need to collect the data, it needs to be precise. They need to be exactly on target.”

After splashdown, a separate Armstrong Flight Research Center team will collect a reinforced sensor affixed to the exterior of the capsule designed to closely examine the heat shield.

“I’m really excited for my team to be a part of such an important mission,” said Patty Ortiz, assistant project manager for the capsule sensor project at the center. “This is definitely a turning point for me as I have been working on it since 2019.”

The center has pushed the boundaries of human flight for decades and collected vast amounts of data while doing so.

“We think of our planes as flying laboratories; maybe we’ll do things that haven’t been done before,” said Brad Flick, who retired as the center’s director on March 20 after nearly four decades at the research facility.

Robert Navarro, Armstrong Flight Research Center project manager, passes the Gulfstream III aircraft that will be used in the Artemis II mission.

(Genaro Molina / Los Angeles Times)

In the 1960s, engineers at the Flight Research Center helped design and test a model of the Apollo lunar lander that Neil Armstrong used to practice landing on Earth before flying to the moon. (The center was later renamed after the first person to walk on the lunar surface.)

The center had been preparing to study the Artemis II reentry for years, but the study became even more important when NASA discovered problems with the heat shield after the Artemis I test mission.

NASA directed the Artemis I capsule to first just skim the Earth’s atmosphere, then briefly exit back into space, and then complete the final re-entry. This new approach reduced the forces astronauts would face on reentry and helped NASA more precisely maneuver the capsule to its landing point in the Pacific, regardless of where or when it returned from the moon.

This mission appeared to be successful, but when the crew began examining the heat shield at the bottom of the uncrewed capsule after landing, they noticed a problem.

After NASA’s Orion spacecraft was recovered at the end of the Artemis I test flight and transported to NASA’s Kennedy Space Center in Florida, the heat shield was removed from the crew module inside the Operations and Control Building and returned for inspection.

(NASA)

The heat shield is designed to slowly erode (or “destroy,” as NASA puts it) to keep conditions in the capsule habitable during re-entry, while air a few inches away can reach nearly 5,000 degrees Fahrenheit: The outer layer of the shield routinely heats up, then sheds off in the form of gas and charcoal chunks, which remove that heat from the capsule as it dissipates into the atmosphere around the capsule.

The problem with Artemis I was that the new reentry approach NASA was trying seemed to disrupt this ablation process.

Because Artemis I returned to space between the initial dive into the atmosphere and the final re-entry, there was a brief period of heat exposure; This meant that the hot interior of the heat shield continued to produce gases, but the exterior was no longer shedding material fast enough to allow those gases to escape. Pressure built up, cracking the heat shield and ultimately causing larger pieces to break off during the final re-entry.

NASA scientists determined that they would have survived if there had been a crew on board; but they did not want to expose the Artemis II astronauts to unnecessary risk.

This left two options: First, replace the already constructed Artemis II heat shield with a new design that could withstand the reentry path attempted with Artemis I. Second, change the reentry path to bypass the initial plunge into the atmosphere and go straight in to eliminate the conditions that created the problem in the first place.

The agency ultimately deemed replacing the Artemis II heat shield too much of a logistical headache and opted for the second, simpler approach. On Friday, NASA astronauts will put this decision to the test. Armstrong Flight Research Center scientists stand by to watch.