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Heat Shield Testing at JSC
05.23.06
 
Engineers at NASA Johnson Space Center in Houston are pushing the limits at the center's facility for testing materials that may be used on heat shields for next-generation spaceships.

Wayne Smith prepares sample for test The series of tests, which began April 19, will help engineers better determine the type of thermal protection system needed for a vehicle to return safely from low-Earth orbit and from future lunar missions.

Image to right: Wayne Smith prepares a sample of reinforced carbon-carbon for a test in the JSC Atmospheric Reentry Materials and Structures Evaluation Facility. Credit: NASA

Six NASA centers from across the country are pooling their testing facilities under the Thermal Protection System Advanced Development Project. The development project is led by NASA’s Ames Research Center for the Crew Exploration Vehicle Project Office, which is based at JSC. The final flight version of the heat shield and support systems will be designed and manufactured by the crew vehicle’s prime contractor when that contract is awarded.

JSC’s Atmospheric Reentry Materials and Structures Evaluation Facility, known as the arcjet, is used for testing materials and components under aero-thermodynamic heating conditions similar to those encountered during space flight and reentry.

Engineers at JSC are performing the tests to evaluate the performance of two different types of heat shield materials. One is LI-2200, a thermal protection tile used on space shuttle orbiters. The other is BRI-18, a tile originally developed as a potential heat shield upgrade that is just now being installed on shuttles.

“We are pushing the limits of these materials in our arcjet facility as we test tiles made from coated and uncoated LI-2200 and BRI-18,” said T.J. Kowal, Crew Exploration Vehicle thermal protection subsystem manager.

The two thermal protection tiles could be used on the CEV heat shield for the initial low-Earth orbit flights of the new vehicle. Due to the geometry of the CEV, the tiles would experience reentry heating temperatures up to 3,400 degrees Fahrenheit, about 500 degrees higher the 2,900 degrees experienced by shuttles.The increased heating is due to the capsule’s smaller surface area and steeper descent, and would be experienced for only about two minutes. These arcjet tests will determine whether the tile temperatures would be pushed too far, even for a single mission.

Wayne Smith works on arc heater Image to left: Wayne Smith of the JSC Atmospheric Reentry Materials and Structures Evaluation Facility works on the facility's arc heater. Credit: NASA

For the CEV heat shield, the tiles could only be used once versus the 100 missions they are certified for on the orbiters.

LI-2200 is a silica tile that can withstand temperatures of 2,300 degrees Fahrenheit for up to 100 orbiter missions, and temperatures as high as 2,900 degrees Fahrenheit for a single orbiter mission. The coating applied to these tiles allows 90 percent of the heat generated upon reentry to be radiated back into the atmosphere.

BRI-18, whose development was recently completed, is an advanced, high-density tile with similar temperature capability as LI-2200. BRI-18 is a stronger tile material than LI-2200 and can also be protected with a more durable coating for superior damage resistance.

JSC’s arcjet will be used in the future to help evaluate heat shield materials for the crew vehicle when it begins returning from initial moon missions in 2018. Because of the angle at which the crew capsule will reenter when coming back from the moon, the heat shield will need to be able to withstand temperatures up to 4,800 degrees Fahrenheit.
 
 
NASA's Johnson Space Center
Lynnette Madison