Reuse, Recycle...
As I described in my May 2005 column, NASA's three-year Genesis mission had a near-death experience when its Sample Return Capsule (SRC) smacked the desert in the Utah Test and Training Range at 193 mph after the drogue parachute failed to deploy. The science team recovered most of the shattered solar-wind collectors and completed most of the experiments, but it wasn't as elegant as they expected.
The Genesis MIB Report found several errors, including the "proximate cause" that nearly killed the project: the design process inverted the G-switch sensor design. In my column, I wondered if the board orientation had changed after the first layout. That's essentially what happened: ...the relay cards...were designed with the G-switch sensors in an inverted orientation as compared to how they were planned for Stardust (the heritage design).
The seven-year Stardust mission (www.nasa.gov/mission_pages/stardust/main/index .html) used a more complex spacecraft to collect dust from Comet Wild 2 (it's half-German: "vilt two") and interstellar space. The Genesis mission reused Stardust's Avionics Unit (AU) design to reduce engineering time and keep costs under control, but new functions required additional cards that the Stardust AU frame couldn't accommodate. The Genesis engineers therefore split the AU in half, rotated the cards by 90 degrees to fit within the SRC's constrained volume, and laid out new cards holding the G-switches.
The MIB observes: These changes laid out the relevant portions of the relay card printed circuit boards based on a Stardust heritage schematic that contained no indication of any sensitivity of the G-switch sensors to orientation. It also appears that the G-switch sensor part-level drawing was not understood by the layout engineer, since it contained a clear indication of the required direction of acceleration to close the switch.
Because those switches would close just once during the flight, [o]peration of the spacecraft appeared nominal until the expected deployment of the drogue parachute at approximately 108,000 ft (33 km) altitude. No drogue or parachute was observed, and the SRC impacted the desert floor...
