Investigations of a control surface seal for reentry vehicles

Reentry vehicles generally require control surfaces such as rudders and body flaps to steer them during flight. Control surface seals are installed along hinge lines and where control surface edges move close to the vehicle body. These seals must operate at high temperatures and limit heat transfer to underlying structures to prevent overheating and possible loss of vehicle structural integrity. Test results are presented for the baseline rudder/fin seal design for the X-38 reentry vehicle. Compressing seals at the predicted peak seal temperature of 1900°F resulted in loss of seal resiliency. The vertical Inconel rudder/fin rub surface was redesigned to account for this loss of resiliency. Room-temperature compression tests revealed that seal unit loads and contact pressures were below limits set to protect shuttle thermal tiles on the horizontal sealing surface. The seals survived an ambient-temperature 1000 cycle scrub test over sanded shuttle tiles and were able to disengage and reengage the tile edges during testing. Arcjet tests on a single seal caused a large temperature drop (ΔT = 1710°F) in the seal gap and confirmed the need for seals in the rudder/fin gap location. These test results verified that this seal is satisfactory for the X-38 application.