[rendall]

I read your comment before I read the article, and it gave me context for this passage:

> After extensive tests and analyses, Boeing engineers concluded the helium leaks were the result of slightly degraded seals exposed to toxic propellants over an extended period....

> The thruster problem, testing indicated, was caused by high temperatures that, in turn, caused internal Teflon seals to deform in poppet valves, restricting the flow of fuel.

> The high temperatures, the engineers concluded, were largely the result of manual flight control tests that caused the jets to fire hundreds of times in rapid-fire fashion while the craft was oriented so those same jets were in direct sunlight for an extended period.