NASA has developed a silver, metallic-based thermal control coating for its Orion spacecraft that will protect the vehicle from extreme heat both in orbit and during its fiery return to Earth.
Orion's thermal protection system is one of the most critical parts of the spacecraft intended to facilitate human exploration of asteroids and of Mars.
It consists of the spacecraft's main heat shield that faces into the atmosphere on reentry to slow the spaceship down and also the grid of tiles known as the back shell.
During Orion's next mission atop the agency's Space Launch System rocket, called Exploration Mission-1 (EM-1), the spacecraft will be in space for more than three weeks and return to Earth under even faster and hotter conditions than during its last flight.
"As we move towards building the system for EM-1, we've been able to take advantage of what we learned from building and flying Orion to refine our processes going forward," said John Kowal, NASA's thermal protection system lead for Orion.
During EM-1, Orion will endure a more intense re-entry environment. While the spacecraft encountered speeds of 30,000 feet per second during Exploration Flight Test-1 and temperatures of approximately 2,204 degrees Celsius, it will experience a faster return from lunar velocity of about 36,000 feet per second.
The speed difference may seem subtle, but the heating the vehicle sees increases exponentially as the speed increases.
Engineering teams are preparing Orion's heat shield to perform re-entry during any of missions planned near the Moon or in high lunar orbit in the coming years.
For these future Orion missions, a silver, metallic-based thermal control coating will be bonded to the crew module's thermal protection system back shell tiles.
The coating, similar to what is used on the main heat shield, will reduce heat loss during phases when Orion is pointed to space and therefore experiencing cold temperatures, as well as limit the high temperatures the crew module will be subjected to when the spacecraft faces the Sun.
The coating will help Orion's back shell maintain a temperature range from approximately minus 101 to 287 degrees Celsius prior to entry and also will protect against electrical surface charges in space and during re-entry.
Engineers have also refined the design in ways that improve the manufacturing process and reduce the mass of the spacecraft for the upcoming exploration missions.
Instead of a monolithic outer layer, the heat shield will be made of about 180 blocks that can be made simultaneously with the other heat shield components to streamline the labour-and-time-intensive manufacturing process.
In addition, engineers have found ways to reduce the mass of the heat shield's underlying structure, which is composed of a titanium skeleton and carbon fiber skin.
Teams have optimised the thickness of the skeleton and the skin based on the pressures that different areas will experience during flight and reentry, adding more fidelity to the overall structure while allowing it to be lighter.