Nasa’s Artemis II crew are approaching the most dangerous stage of their historic Moon mission, with the astronauts set to endure a high-speed re-entry into Earth’s atmosphere aboard the Orion capsule in what will be a critical test of the spacecraft’s safety systems.
Before splashing down in the Pacific Ocean, the four astronauts must survive a fiery descent using a heat shield that has previously shown flaws during testing.
Orion Crew Prepare for High-Risk Earth Re-entry
The Orion capsule is scheduled to re-enter Earth’s atmosphere before splashing down off the coast of California at 10.07pm BST on Friday.
The four Artemis II astronauts – Christina Koch, Jeremy Hansen, Reid Wiseman and Victor Glover – are nearing the end of their 10-day, 700,000-mile mission around the Moon and back.
During re-entry, the spacecraft will hit Earth’s atmosphere at nearly 25,000mph, travelling bottom-first at roughly seven miles per second.
The immense speed will generate temperatures exceeding 2,760C around the capsule, subjecting Orion to one of the most extreme environments any crewed spacecraft can face.
Heat Shield Under Scrutiny After Artemis I Concerns
The astronauts’ safety will depend on Orion’s 3in-thick heat shield, designed to protect the capsule by gradually burning away and dispersing heat during descent.
However, concerns remain after Artemis I, the uncrewed 2022 test mission, revealed unexpected problems with the shield.
More than 100 areas of the heat shield suffered debris loss during that flight, with chunks of material breaking away and bolts partially melting.
A subsequent Nasa investigation found trapped gases inside the Avcoat heat shield material had caused cracking and fragmentation.
Although Nasa has since redesigned the material to improve gas venting, the upgraded version was not ready in time for Artemis II.
As a result, the crew will fly with an earlier version of the shield, which is understood to be less permeable than the one used during Artemis I.
Nasa Alters Re-entry Plan to Reduce Heat Exposure
To mitigate the risk, Nasa has changed Orion’s descent profile for Artemis II.
Skip Re-entry Dropped for New Trajectory
During Artemis I, Orion used a “skip entry” manoeuvre, briefly dipping into the upper atmosphere before rising back out, helping to reduce G-forces and improve landing precision.
For Artemis II, Nasa has abandoned that approach.
Instead, the capsule will follow a steeper, faster descent designed to shorten the amount of time spent in the most intense heat.
While Nasa says modelling indicates the revised trajectory is safer, the profile has never been tested in flight.
Experts Raise Questions Over Certification and Safety
Nasa maintains it has full confidence in Orion’s heat shield and says internal flight data from Artemis I indicates the crew would have remained safe despite the material loss.
Jared Isaacman, Nasa administrator, said he had “full confidence” in the spacecraft’s safety.
However, some experts have voiced concern.
Last year, the Nasa Office of Inspector General warned that unexpected behaviour in the Avcoat heat shield created a risk that it may not adequately protect the crew during future missions.
Former Space Shuttle astronaut and heat shield specialist Charles Camarda has also criticised Nasa’s assessment, arguing the revised re-entry plan may not sufficiently reduce the danger.
Final Hurdle Before Splashdown
Even after surviving the heat of re-entry, the mission will face one final critical phase.
Eleven parachutes and drogues must deploy in precise sequence to slow Orion to under 20mph before splashdown.
Investigators have also noted concern that debris from the heat shield could damage the parachute system if fragments strike the upper part of the capsule.
The full descent from atmospheric re-entry to ocean landing is expected to last around 16 minutes.
Conclusion
For Artemis II, a successful splashdown will mark not only the safe return of the first crewed Moon mission in more than half a century, but also a vital step towards Nasa’s long-term plans to return astronauts to the lunar surface.
Until Orion reaches the Pacific intact, however, the mission’s most perilous challenge still lies ahead.
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