A Closer Look At The Orion Spacecraft & Its Heat Shield
Late last year toward the end of the Artemis 1 mission, the Orion spacecraft reentered Earth’s atmosphere before a successful splashdown in the ocean. Once recovered, NASA began taking a closer look at the spacecraft which revealed a few concerns. Specifically, engineers noted variations across the appearance of Orion’s heat shield relative to agency models and predictions.
Now toward the middle of 2023, we just got the news that a new heat shield has been installed on the Artemis II Orion spacecraft. In the coming months, we can expect to see more work on this component with the eventual addition of extra heat resistant material. While the first Artemis mission was uncrewed and could afford mistakes, the second mission cannot.
This launch will have four crew members relying on this heat shield and the various spacecraft technology to keep them safe and complete the mission. Here I will go more in-depth into the unpredicted heat shield results, the design of this component, what to expect in the coming weeks, and more.
Heat Shield Progress
With Artemis II getting closer, NASA has been providing more updates on the hardware, general infrastructure, the SLS rocket, etc. Just over a week ago on the 27th NASA tweeted saying, “The heat shield ensuring the safe return of the #Artemis II crew is installed on Orion! Up next, the spacecraft will be outfitted with some of its external panels ahead of acoustic testing later this summer.”
In this case, on June 25, 2023, teams completed installation of the heat shield for the Artemis II Orion spacecraft inside the high bay of the Neil Armstrong Operations and Checkout Building at NASA’s Kennedy Space Center in Florida. The 16.5-foot-wide heat shield is one of the most important systems on the Orion spacecraft ensuring a safe return of the astronauts on board. As the spacecraft returns to Earth following its mission around the Moon, it will be traveling at speeds of about 25,000 mph and experience outside temperatures of nearly 5,000 degrees Fahrenheit. Inside the spacecraft, however, astronauts will experience a much more comfortable temperature in the mid-70s thanks to Orion’s thermal protection system.
When ready, the upcoming tests will validate the crew module can withstand the vibrations it will experience throughout the Artemis II mission, during launch, flight, and landing. Once acoustic testing is complete, technicians will attach the crew module to Orion’s service module, marking a major milestone for the Artemis II mission.
It’s important to point out that NASA gained a bunch of valuable information from the Artemis I flight that they are applying to each and every aspect of the next mission. This especially goes for the heat shield considering they found a few unexpected results. After Artemis I, teams found variations across the appearance of Orion’s heat shield in which the ablative material that helps protect the capsule from the extreme heat of reentry wore away differently than predicted.
In a statement, the company said, “Post-flight inspection shows a significant amount of original Avcoat material remained on Orion. Thermal protection system experts have correlated the timing of descent through the atmosphere with data from hundreds of sensors as well as gathered imagery and video. Teams are assessing this set of data to understand the phenomenon. Experts also continue to assess an issue seen during the flight where latching current limiters switched open without commanding several times throughout the mission. These switches, which are circuit breaker-like devices that are part of a power conditioning and distribution unit responsible for taking power generated by the solar arrays and preparing it for distribution to systems, help control power to components in the service module. Engineers are reviewing flight data to understand the source of the issue and plan to conduct testing in a flight-like configuration” they said.
While these problems weren’t detrimental to the mission and the agency could likely get away with them in the future, NASA wants to make sure the system is perfect. After the first mission, teams extensively reviewed more than 155 gigabytes of Orion data to confirm the spacecraft’s successful performance during its journey nearly 270,000 miles beyond the Moon and farther than any spacecraft built for humans has flown. These mass amounts of data gave the agency enough to work on for a while.
Heat Shield Ablative
As partially mentioned prior, NASA just installed the heat shield however the next step is adding external panels. When the agency said it found variations across the appearance of the heat shield they were talking about the ablative material or extra layers added to the shield.
Years before Artemis I launched, technicians at NASA’s Kennedy Space Center in Florida meticulously applied more than 180 blocks of ablative material to the heat shield for the Orion spacecraft. Prior to installation, several large blocks of the ablative material called AVCOAT were produced at the agency’s Michoud Assembly Facility in New Orleans. They were then shipped to Kennedy and machined into 186 unique smaller blocks before being applied by the technicians onto the heat shield’s underlying titanium skeleton and carbon fiber skin.
When preparing for the heat shield, engineers conducted non-destructive evaluations to look for voids in the bond lines, as well as measured the steps and gaps between the blocks. The gaps are filled with adhesive material and then reassessed. The heatshield then underwent a thermal test after which it was sealed, painted and then taped to help weather on-orbit thermal conditions. Similar work is still necessary for the Artemis II heat shield which should happen not long from now. With the mission still scheduled to take place in late 2024, the agency has a lot of work left.
Assuming the heat shield is completed and ready, it won’t be used until the very end of the mission. The Artemis II crew will travel 6,400 miles beyond the far side of the Moon. From this vantage point, they will be able to see the Earth and the Moon from Orion’s windows, with the Moon close in the foreground and the Earth nearly a quarter-million miles in the background. With a return trip of about four days, the mission is expected to last just over 10 days. Instead of requiring propulsion on the return, this trajectory harnesses the Earth-Moon gravity field, ensuring that—after its trip around the far side of the Moon—Orion will be pulled back naturally by Earth’s gravity for the free return portion of the mission.
This maneuver will set the spacecraft on its trajectory back toward Earth to enter our planet’s atmosphere traveling at 25,000 mph (11 kilometers per second), producing temperatures of approximately 5,000 degrees Fahrenheit (2,760 degrees Celsius) – faster and hotter than Orion experienced during its 2014 flight test.
The mission will end with a test of Orion’s capability to return safely to the Earth as the spacecraft makes a precision landing within eyesight of the recovery ship in the ocean. Following splashdown, Orion will remain powered for a period of time as divers from the U.S. Navy and operations teams from NASA’s Exploration Ground Systems approach in small boats from the waiting recovery ship. The divers will briefly inspect the spacecraft for hazards and hook up tending and tow lines, and then engineers will tow the capsule into the well-deck of the recovery ship to bring the spacecraft home.
During Artemis I, Orion accomplished 161 test objectives to fully demonstrate every aspect of the spacecraft, including 20 objectives added mid-flight. Data shows the European-built service module generated 20% more power than initial expectations and consumed about 25% less power than predicted. All the spacecraft’s dynamic separation events, such as separation of the launch abort system during ascent and parachute deployment during landing — which involved 375 pyrotechnic devices total — were completed without issue. Splashdown, which was moved 300 miles south due to poor weather, occurred 2.4 miles from the target landing spot, well within requirements.
Upon return to Kennedy Space Center in Florida, avionics components earmarked for reuse on Artemis II were removed and refurbished for integration, including phased array antennas, a vision processing unit, GPS receivers, and inertial measurement units. All Artemis I avionics components have been integrated into the Artemis II crew module. As far as other progress, the SLS solid rocket booster motor segments and core stage will be shipped to Kennedy later this year, after the engine section and RS-25 engines are connected to the rest of the already-complete stage. The recovery team, along with personnel from the Department of Defense, completed rigorous testing of a new crew module test article in support of Artemis II efforts and will conduct open water recovery testing in the coming months to ensure the crew on board are quickly and safely removed from the spacecraft.
Conclusion
NASA just recently installed the heat shield on Orion. With this complete the agency now needs to add some external panels and complete various tests. This will ensure the heat shield is ready to safely return the crew of 4 on Artemis II. We will have to wait and see how it progresses and the impact it has on the space industry.
