Daniel

(for future reference: these people did a really great job, and dodgy test jigs are totally standard. I'm just poking fun at the contrast.)

They ended up launching without discovering the cause, with some procedural changes. The door opened normally on orbit.

(from SAFER battery runaway analysis https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180003204.pdf …)

"All possibilities focused on the properties of Viton adhering to the gold surface of the door seal under various conditions."

"despite the best efforts of many able people, we were not able to clearly identify the failure mechanism. In fact, it sometimes seemed as if the failure could not have occurred, but it had."

"This team was initially given two weeks to complete these activities, based on the (optimistic) assumption that the failure mechanism would be easily identified and rectified. In the end, the team was to operate for almost one year..."

"...arranged a Tiger Team which included members from NASA MSFC, the Chandra external review committee, MIT, Lockheed Martin, STARSYS, TRW and SAO..."

Later tests showed completely normal torque values on the exact same unit.

The motor had a torque/pressure burst disk that could only have burst at 10.9 N*m, but no tests had ever yielded values above 3 N*m.

(Heck, wouldn't it be cool if NASA worked doomed programs just for the lessons learned? Oh wait, Project Morpheus.)

The door reported being stuck half-way open. They couldn't re-pressurize with the door open for fear of contamination. In the end, they warmed the whole spacecraft back up, destroying evidence of the cause; the door was still sealed.

Paraffin actuator on sensor array pressure door on priceless flight unit worked flawlessly 23 times in every possible circumstance over months, plus hundreds of acceptance tests, until one fateful therm-vac test of the entire observatory.

'Lessons Learned' reports are so fascinating. It's like a murder mystery! This one by the Chandra Observatory team reads like condensed panic: (ACIS Door Failure Investigation and Mitigation Procedure https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000048380.pdf …)

The Canadian equivalent of a hangar collapsing on Buran: "Ready for testing long-duration flights, field mice attacked the SHARP aircraft while it was in storage, and the flights never took place."