The Artemis II mission, humanity’s first crewed mission to the vicinity of the Moon since 1972, will wait longer to get off the ground. Originally planned for September 2025, Artemis II will now fly no earlier than April 2026 but will fly with the original Orion command module and heat shield.
A heat shield replacement would likely have caused a year’s slip to Artemis II and an 18-month slip to Artemis III from their revised dates. The Artemis III mission to perform the first human landing on the Moon in over half a century has also been pushed to mid-2027 due to the program’s forward path decisions.
Besides resolving the heat shield issue, Artemis III is also dependent on a successful uncrewed demonstration by the SpaceX Starship-based lunar lander as well as a successful inflight fueling demonstration.
The SLS Artemis II core stage is being moved into the VAB on July 23, 2024. (Credit: NASA)
NASA Administrator Bill Nelson announced that Artemis II will fly with its original heat shield but there would be modifications to the reentry flight path. The Orion’s life support and environmental systems need to be checked as well, which is also a driver for the launch date change.
The administrator prefaced his remarks by noting that space is hard, and quoted JFK’s speech announcing his challenge to America to “send a man to the Moon, and to return him safely to the Earth.” He also stated that NASA would not fly until it is ready, and stressed that Artemis I was a test flight.
After Artemis I’s return to Earth in December 2022, the heat shield performed differently than NASA expected due to issues with permeability on the Avcoat heat shield blocks. Artemis I conducted a first-of-its-kind “skip entry” to reduce the spacecraft’s velocity, as opposed to Apollo’s reentries from the Moon which entered directly into the atmosphere.
During Artemis I’s skip entry gases formed and became trapped in the heat shield during the reentry. This led to uneven wear and shedding of parts of the heat shield, and divots were noted in the heat shield after the flight.
Testing of Avcoat blocks during activity to determine root cause of Artemis I’s heat shield issue. (Credit: NASA)
The gas formation was ironically caused by the lower velocity the Artemis I spacecraft was able to use, combined with a lack of permeability on a number of Avcoat blocks. The heat shield was tested at high heating rates and performed as expected, but the less severe heating on the actual flight slowed charring while still allowing gases to form.
These gases cracked the Avcoat and caused the divots that were seen. Some blocks of Avcoat on the Artemis I heat shield were permeable and these blocks allowed gas to vent, preventing a buildup and cracking of those blocks. Future heat shields are being produced with permeable Avcoat to prevent this issue.
NASA associate administrator for the Moon and Mars program Amit Kshatriya noted that the Artemis I spacecraft performed very well with regard to its flight path and the accuracy of its splashdown near the USS Portland. However, the heat shield was not designed to liberate charred material at the rate that it did, and that was an unacceptable result.
Artemis I at its farthest distance from the Earth and the Moon during its flight in late 2022. (Credit: NASA)
However, since Artemis II is conducting a free return flyby of the Moon, it was determined that the flight path on reentry could be adjusted safely. The skip entry allows for a much higher “cross range” with flexibility on splashdown sites as opposed to Apollo’s entries, but shorter skips will be used for Artemis II. The shorter skips will lead to shorter launch windows, cutting out up to 50 percent of each monthly window.
Kshatriya also noted that batteries related to the abort system needed to be fixed, and that the fix has been qualified and finished. The life support system on Orion needed work on valves and the carbon dioxide removal system, and testing of the system has taken longer than thought.
The agency conducted 121 tests on the heat shield’s thermal properties, using the arc jet facility and the interaction heating facility at the Ames Research Center, the hypersonic wind tunnels at the Langley Research Center, the Advanced Light Source test facility at the Lawrence Berkeley National Laboratory, and other facilities throughout the country.
The Artemis I mission’s aft booster segments prior to full booster stacking. (Credit: Stephen Marr for NSF)
An independent team led by former NASA shuttle flight director, leader of NASA’s mission operations directorate, and current Aerospace Safety Advisory Panel member Paul Hill reviewed NASA’s findings and agreed with them.
The stacking of Artemis II’s boosters and launch vehicle is expected to begin soon. The aft center segments of the boosters are scheduled to move to the Vehicle Assembly Building on Dec. 6, while the Artemis II core stage is scheduled to move into High Bay 2 on Tuesday, Dec. 10.
While the year-long “clock” for the solid rocket boosters would start when the aft center segments are stacked onto the aft segments, Kshatriya noted that the propellant stability of the boosters would not expire until 2028. He also believes the life of stacked solid rocket boosters could be up to 18 or even 24 months.
During the wait for the launch date, the Artemis II crew will be training on ascent and launch after the software load is conducted for their simulator, and they will be focusing on the last year of training activities.
The Artemis II crew L to R: Victor Glover, Reid Wiseman, Jeremy Hansen, and Christina Koch. (Credit: NASA)
Administrator Nelson also noted that China was going to send humans to the Moon and stated that it was important for the United States to do so as well. The administrator expected that the Artemis program would continue, noting that Artemis IV would fly a SpaceX lander and Artemis V would fly a Blue Origin lander.
(Lead image: The Artemis I heat shield seen after its flight. Credit: NASA)
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