NASA Selects Material for Orion Spacecraft Heat Shield

April 19, 2009 // Published as a news service by IHS

Orion is part of the Constellation Program that is developing a spacecraft system for exploration of the moon and other destinations in space.

Orion will face "extreme" conditions during its voyage to the moon and back. On the return through Earth's atmosphere, the module will encounter temperatures as high as 5,000 degrees Fahrenheit, according to NASA.

Heating rates may be up to five times more extreme than rates for missions returning from the International Space Station, experts said.

Orion's heat shield, the dish-shaped thermal protection system at the base of the spacecraft, will endure the most heat and will erode, or "ablate," in a controlled fashion, transporting heat away from the crew module during its descent through the atmosphere, according to NASA.

To protect the spacecraft and its crew from such conditions, the Orion Project Office at NASA's Johnson Space Center identified a team to develop the thermal protection system heat shield.

For more than three years, NASA's Orion Thermal Protection System Advanced Development Project considered eight different candidate materials including the two final candidates, Avcoat and Phenolic Impregnated Carbon Ablator (PICA).

Avcoat was used for the Apollo capsule heat shield and on select regions of the space shuttle orbiter in its earliest flights. It was put back into production for the study.

It is made of silica fibers with an epoxy-novalic resin filled in a fiberglass-phenolic honeycomb and is manufactured directly onto the heat shield substructure and attached as a unit to the crew module during spacecraft assembly.

PICA, which is manufactured in blocks and attached to the vehicle after fabrication, was used on Stardust, NASA's first robotic space mission dedicated to exploring a comet and the first sample return mission since Apollo.

The NASA Ames Research Center led the study in cooperation with experts from across the agency. Engineers performed thermal, structural and environmental testing on both candidate materials, experts said.

The team then compared the materials based on mass, thermal and structural performance, life cycle costs, manufacturability, reliability and certification challenges. NASA, working with Orion prime contractor Lockheed Martin, recommended Avcoat as the more robust system.

In partnership with the material subcontractor, Textron Defense Systems, Lockheed Martin will continue development of the material for Orion. While Avcoat was selected as the better of the two candidates, more research is needed to integrate it completely into Orion's design, according to NASA.

The Orion crew module, which will launch atop an Ares I rocket, is targeted to begin carrying astronauts to the International Space Station in 2015 and to the moon in 2020.

Source: NASA.