Artemis II’s heat shield overcomes extreme challenges

Theo Live ScienceOrion’s heat shield had minimal scorching loss, the ceramic pieces were not cracked, and reflective heat tape was still present in many locations, helping to ensure the safety of the Artemis II crew during the plunge through the atmosphere.

“Initial investigations showed that the heat shield worked as expected, no unusual conditions were detected. Images taken by divers immediately after the landing in the sea and subsequent tests with the Orion ship showed that the loss of scorching layer that appeared during the Artemis I mission has significantly decreased in both number and size,” NASA announced this week.

Theo SpaceArtemis II mission commander Reid Wiseman and three teammates Victor Glover, Christina Koch, and Jeremy Hansen, inspected the Orion ship immediately after the landing on April 10. Visually, Wiseman said, the heat shield passed the tough test.

“As we got closer to Orion, we saw a little bit of burn loss at the shoulder, where the heat shield meets the cone structure of the spacecraft. But when we crouched down and looked at the bottom, the four of us saw that the heat shield looked very good,” Wiseman said. He also commented that the return trip to Earth was wonderful and smooth.

NASA’s new announcement determined that the Space Launch System (SLS) rocket, which had encountered many leaks and launch delays, worked well during the Artemis II mission. This agency also achieved high accuracy in calculations, similar to previous Apollo missions.

“Orion landed accurately in the sea, only 4.7 km from the target landing point. Initial assessments showed that the atmospheric re-entry speed was within an error of 1.6 km/h compared to predictions,” NASA wrote. According to the agency, the Orion spacecraft moved at nearly 35 times the speed of sound when reentering the atmosphere.

The heat shield is a protective layer on the bottom of the Orion ship, designed to prevent the ship from burning up during re-entry into Earth’s atmosphere. Time said that, like the Apollo spacecraft, Orion’s heat shield is mainly made of Avcoat material, a mixture of epoxy resin and silica fibers, which helps absorb the terrible heat when plunging into the atmosphere and slowly burns out, taking the heat away from the ship. It needs to withstand temperatures of up to 2,760 degrees Celsius, half the temperature of the Sun’s surface and significantly higher than the 1,650 degrees Celsius that spacecraft returning from Earth orbit must endure.

However, Orion’s heat shield encountered major problems during the Artemis I unmanned mission in November 2022. When salvaging the ship’s cabin from the ocean, technicians discovered the heat shield had more than 100 cracks and large dents where the Avcoat had peeled off. This leads to the risk of heat from the atmospheric re-entry process penetrating the ship’s aluminum alloy wall, taking the lives of the astronauts inside.

The unexpected damage to the heat shield caused NASA to conduct a thorough investigation that lasted many months. The agency discovered that as the ship crashed through the atmosphere, gas became trapped in some parts of the heat shield, causing pressure to gradually build up and cause cracks in the outer material layer.

Artemis I followed the re-entry route pioneered by the Apollo program, called “skip-entry”. Instead of plunging straight into the atmosphere like ships returning from Earth’s orbit at lower speeds, the Apollo spacecraft “glide” in and out, then back in again, thereby gradually reducing heat and gravitational effects.

However, this seems too harsh on the heat shield. To fix it, in the Artemis II mission, NASA uses a new version of Avcoat with higher porosity, allowing gas to escape, while adjusting the atmospheric re-entry journey in a more direct direction. Initial analysis shows that this seems to be an effective solution.

The Orion spacecraft carrying the Artemis II crew left the launch pad on the evening of April 1 (morning of April 2, Hanoi time) and returned on the evening of April 10 (morning of April 11, Hanoi time), completing NASA’s first manned mission beyond low Earth orbit after 54 years. The crew was said to “represent the world”, when for the first time women, people of color and non-American members flew to the Moon. They are estimated to have traveled a distance of 1,117,659 km during their entire journey around the Earth and Moon. Estimated total flight time is 9 days, 1 hour and 31 minutes.

The Artemis II mission is designed as a stepping stone to NASA’s Artemis program, which aims to establish a permanent human presence on the Moon. The Artemis I unmanned mission took place in November 2022, after many delays and cancellations. Next, NASA will test the Orion spacecraft and lunar landing stations in Earth orbit during the Artemis III mission in 2027. The agency aims to perform the first lunar landing in 2028 with the Artemis IV mission. By the 2030s, NASA expects to begin developing settlements, autonomous robots and cargo landing stations, aiming to establish a sustainable presence on the lunar surface.