Upside-Down Sensors Caused Proton-M Rocket Crash
Michi writes "According to Anatoly Zak, the crash of the Russion Proton rocket on 1 July was apparently caused by several angular velocity sensors having been installed upside down. From the source: 'Each of those sensors had an arrow that was supposed to point toward the top of the vehicle, however multiple sensors on the failed rocket were pointing downward instead.' It seems amazing that something as fundamental as this was not caught during quality control. Even more amazing is that the design of the sensors permits them to be installed in the wrong orientation in the first place. Even the simplest of mechanical interlocks (such as a notch at one end that must be matched with a corresponding projection) could have prevented the accident."
A review of the quality control procedures used by the contractors responsible is underway.
...aren't so amazing when you look at the track record of Russian manufacturing.
Murphy's Law is still in effect. Like the snippet says make sure that they can only be installed one way mechanically, because you won't catch 100% of the errors in QA.
The US once sent a probe all the way to mars, only to have it fail because the ground computer was in imperial units while the orbiter was in SI units.
Getting everything correct is hard... really hard. For most projects you have elaborate "fail gracefully" modes which rely on external agents to notice the problem and take action. A doctor or pilot can take appropriate action, but it's hard to do with rockets.
For comparison, I wrote the software for the altimeter that goes into some 747 aircraft. Total of about 21,000 lines of C, about 40% comments so figure 12,000 lines of code. The testers (and I) worked really hard to find all bugs in the system, knowing that a mistake could knock a plane out of the sky. There were elaborate internal checks both in software and process, and Boeing did their own testing on top of ours. Everything passed, all requirements were met, things looked good.
The device had 1 bug, found after installation. A software typo which wasn't caught by QA even though it had a specific testing requirement. No one was negligent, it just slipped by despite best efforts.
Multiply this by all the devices in an aircraft, and add in the other engineering disciplines like electronics and mechanical. It's really hard to get everything right all at once, and on the first try.