NASA’s OSIRIS REx mission successfully returned a sample to Earth from the asteroid Bennu back in September, three years after it was collected. However, it could so easily have gone wrong, due to a little oopsie, according to <https://arstechnica.com/space/2023/12/nasas-asteroid-mission-struck-its-target-but-then-dodged-a-bullet/>. What was supposed to happen was, at an altitude of 100,000 feet, the return capsule should have deployed its drogue chute. Then, five minutes later, the cord for this chute would be cut, allowing the main chute to unfurl, after the drogue had done its part in slowing down the capsule descent. Instead, due to a case of (literal) crossed wires, the signal sent at 100,000 feet triggered the cutting (intead of the deployment) of the drogue chute cord, while it was still packed inside the capsule. Then, at 9,000 feet, the release of the main chute caused the drogue chute to pop out first, and immediately fall away. Luckily, there was sufficient margin in the design of the main chute that it was able to cope with the higher descent speed, and bring the capsule down to a safe landing even with this complete failure of the drogue chute. And it was all down to insufficiently clear assembly instructions: "In the design plans for the system, the word 'main' was used inconsistently between the device that sends the electric signals, and the device that receives the signals," NASA said in a written statement. "On the signal side, 'main' meant the main parachute. In contrast, on the receiver side 'main' was used as a reference to a pyrotechnic that fires to release the parachute canister cover and deploy the drogue. "Engineers connected the two mains, causing the parachute deployment actions to occur out of order," NASA said. See, it’s not just software (and hardware) that needs debugging; documentation does, too.