Engineers working on NASA’s Orion capsule are taking a different approach to building the heat shield that will fly on Exploration Mission (EM) – 1. The next version Orion heat shield will be able to withstand the extreme environments Orion will encounter on the second unmanned flight test traveling deeper into space. Engineers gathered data from Orion’s maiden flight, Exploration Flight Test (EFT)- 1, to determine the improvements that need to be made before the next unmanned test flight.
Engineers are building the next version Orion heat shield in blocks rather than in one single massive structure. The top layer of the Orion heat shield protects the crew module from the extreme temperatures experienced during reentry. The layer will be made up of about 180 blocks and built in stages to make the manufacturing process less labor-intensive. This improvement to the heat shield design will save money and cut the current manufacturing time by about two months. Valuable data from EFT-1 will ensure a successful EM-1 mission when Orion launches atop NASA’s Space Launch System (SLS) rocket on a circumlunar journey no earlier than November 2018.
“The heat shield we put to the test during Orion’s flight test last December met every expectation we had and gave us a tremendous amount of data on its thermal and mechanical performance,” said Mark Kirasich, Acting Orion Program Manager. “But the process of building the heat shield as a single piece for that flight also gave us insight into how we could improve the way we build this essential element of the spacecraft.”
Orion is NASA’s next generation spacecraft that will serve as the exploration vehicle to take astronauts Beyond Low-Earth Orbit (BLEO) and deep space. Orion is designed to carry a crew of four to distant planetary bodies, provide emergency abort capability, sustain a crew for a long duration of time, and ensure safe reentry from space. Engineers are working hard to design an Orion capsule that provides a safe environment from launch to landing and recovery.
In the future, NASA will use Orion to fly a manned mission to Mars, but before that can happen the vehicle must undergo years of intense testing. December’s unmanned flight test provided engineers with important insight on spacecraft performance and how well its systems functioned in the harshness of space. Engineers took the insight gathered from EFT-1 and applied it to the manufacturing of the next Orion set to fly on EM-1.
The heat shield is one of the most critical elements of the Orion spacecraft. It serves as a literal “shield” from the extreme temperatures experienced during reentry into Earth’s atmosphere. The Orion heat shield used on EFT-1 experienced scorching temperatures close to 4,000 degrees Fahrenheit and speeds near 80 percent of what it will meet when returning from missions close to the moon. The interior of the capsule was kept at a comfortable temperature in the mid-70s during the chaotic return. Examinations of the heat shield after EFT-1 proved that it performed well within expectations, despite previous doubts regarding the Avcoat/honeycomb structure.
The heat shield used on EFT-1 was made up of a titanium skeleton with a carbon fiber coating that provided structural support. (This also gave the crew module its circular shape on the bottom.) A fiberglass-phenolic honeycomb structure with 320,000 miniscule cells was placed on top. Each cell was filled one-by-one, by hand, with an easily eroded material called Avcoat. The material is designed to wear away during Orion’s reentry through the Earth’s atmosphere. Once the small cell was filled by hand, it was placed in an oven to be cured, x-rayed, and then robotically altered to meet thickness requirements.
During the manufacture of the heat shield for EFT-1, engineers learned that the strength of the Avcoat/honeycomb structure was “below expectations” but analysis showed that it would work. The successful flight proved that the heat shield was able to withstand the extreme stress; however, EM-1 will put Orion in colder temperatures in space and hotter temperatures during reentry. At apogee during EFT-1 Orion was 3,609 miles from Earth. EM-1 Orion will swing around the moon (nearly 239,000 miles from Earth) on a much longer journey. Engineers know that the next version Orion will require a stronger heat shield.
This is not the first announced change to occur to the Orion heat shield after EFT-1. In January, NASA and Lockheed Martin decided to include an advanced 3-D woven thermal protection fabric to the Orion heat shield for the next test flight, EM-1. This woven fabric will provide astronauts extra protection from scorching temperatures when returning from deep space. The 3-D woven textile will be placed in compression pads that fit between the Orion crew module and service module. The pads will absorb the structural loads generated during launch and spaceflight operations.
As described in a previous AmericaSpace article, the multifunctional Quartz “preform” material will be used in thermal protection system (TPS) that keeps the temperature regulated inside the spacecraft. The 2-D pads used on EFT-1 are only good for return from low-Earth orbit (LEO). The ones used on EM-1 must be able to withstand a fiery reentry at speeds near 24,000 mph. Bally Ribbon Mills of Bally, Penn., is responsible for producing the material.
More work on the Orion crew module is underway at NASA’s Michoud Assembly Facility in New Orleans, La. Lockheed Martin engineers performed the first weld on the Orion spacecraft pressure vessel for EM-1 on Sept. 5, 2015. Engineers saved 700 pounds of mass by reducing the number of welds on the pressure vessel from 33 to seven.
Orion is set to launch aloft the maiden voyage of the SLS rocket on EM-1 no earlier than (NET) November 2018. A two-person piloted EM-2 mission previously slated for August 2021 has been delayed due to budget issues with a target of NET April 2023. A critical design review for NASA’s Space Launch System was completed back in July and considered “right on track” for it’s first launch carrying EM-1 in 2018.Missions » SLS » Missions » SLS » EFT-1 » Missions » SLS » EM-1 »