Behind The Black – Robert Zimmerman

Damage to Orion heat shield caused during re-entry in 2022,
including “cavities resulting from the loss of large chunks”

Because the damage to the heat shield on the Orion capsule that flew around the Moon in late 2022 remains somewhat unexplained, NASA is considering delaying the next SLS/Orion mission, presently planned for September 2025 and intended to be the first Artemis flight to carry humans and take them around the Moon.

The heat shield, already installed at the base of the Orion spacecraft, will take the brunt of the heating when the capsule blazes through Earth’s atmosphere at the end of the 10-day mission. On the Artemis I test flight in late 2022, NASA sent an Orion spacecraft to the Moon and back without a crew aboard. The only significant blemish on the test flight was a finding that charred chunks of the heat shield unexpectedly stripped away from the capsule during reentry as temperatures increased to nearly 5,000° Fahrenheit (2,760° Celsius).

The spacecraft safely splashed down, and if any astronauts had been aboard, they would have been fine. However, the inspections of the recovered spacecraft showed divots of heat shield material were missing.

Two years later, despite extensive investigation and analysis, it appears NASA has not yet identified the root cause of the damage. The ablative material used on Orion was similar (though not identical) to the material used successfully on numerous other heat shields since the 1960s, yet it did not perform as expected.

NASA is presently facing three options. Do nothing and fly the next mission as planned, with four astronauts. It could rethink the trajectory used during re-entry, though this would likely not change things significantly unless the astronauts don’t go around the Moon as planned. Or it could change the heat shield itself.

The first two options are very risky, considering the unknowns. The latter involves a major delay of at least two years.

A decision must be made soon however. To meet the agency’s schedule it must begin stacking SLS’s two solid-fueled strap-on boosters next month. Those boosters have a limited life expectancy originally estimated to be one year. In the first unmanned Artemis test flight in 2022, NASA because of other delays stretched that life span to two years, and had no problems with the launch. If it stacks the boosters now and then has to delay for two more years to redesign Orion’s heat shield, those boosters will have been stacked for three years when launched.

Considering how seriously NASA is taking the issues with Starliner, which are likely not as serious as a heat shield that doesn’t work reliably, it would seem insane for NASA to launch Orion manned without fixing its own problem. And yet, for more than two decades NASA has consistently not demanded the same safety standards for SLS that it has demanded for the private commercial rocket startups. We shall see if this pattern now persists.

I continue to believe that the first Artemis lunar landing will not take place before 2030 (at least six years behind schedule). This heat shield dilemma only strengthens that prediction.