T-RADical solution to TPS repair

by Chris Bergin

A futuristic solution to repairing the Shuttle Orbiter’s Thermal Protection System (TPS) on orbit will see Astronauts tackle a damaged ship with a backpack and pressure gun.

The T-RAD (Tile Repair Ablator Dispenser) is based on the concept of a smaller STA-5 applicator, which was part of a scrapped CIPAA (cure in place ablator applicator) back pack system.


According to documents acquired by this site, the concept is undergoing an ‘aggressive development schedule for STS-121’ given the lack of options that will fly on Discovery next month. It is hoped that ‘limited testing’ will be a possible on that mission as part of NASA’s pursuing of ‘safe-to-use certification.’

Despite the size of the device, it can be stowed in a single mid deck locker, ready to be unpacked in the event of damage being spotted in specific areas of the orbiter’s protective tiled skin.

Consisting of a canister, pressurized with CO2, that can be attached to the astronaut’s suit, or can be carried freely behind, and a hand held gun, the option uses the ablator material ‘STA-54’ as a sealant for the landing gear doors – a major weak point in the orbiter’s TPS.

A recent PRCB document noted NASA is ‘evaluating STA-54 as Door Seal & Penetration repair for tile,’ with the note ‘recommend STA-54 with new applicator (T-RAD) for Door Seal & penetrations.’

The canister of liquid CO2 has a weight of approximately 38 lbs when filled, while the Gun and Swivel assembly is borrowed from CIPAA concept that was deemed unavailable after STS-114 last summer.

Such repair requirements are a contingency, one of several that are now open to a crew on a damaged orbiter. Even after a repair is carried out, the work would have to undergo a huge amount of analysis by engineers on the ground before the vehicle is allowed to attempt a trip back home.

Even then, should they be any doubt, the mission would take the option of ‘safe haven’ – where the orbiter would remain docked while the crew take up residence on the International Space Station. A rescue shuttle would be launched to bring the stricken crew home, while the damaged orbiter would automatically undock.

The fate of the damaged vehicle will depend on how she copes on re-entry, although the option is now available where she can – through a series of wires and modifications – complete a landing at Edwards Air Force base in Californian on her own. Problems during re-entry would led to a ditching in the Pacific ocean.

Related Articles