3. Because the engineers worked in inches, we lost the Mars climate orbiter.
The Lockheed Martin team that built the jet thrusters in 1999 followed the imperial system for measurements rather than the metric system. They did not inform NASA about this. It’s listed as ‘assumed loss’.
4. A loose bolt caused the destruction of Soviet N1 moon rocket
In 1969, the Soviets were aiming for the moon with the N1 rocket. A single loose bolt got sucked into the fuel pump and just after 20 seconds of it’s flight, the rocket exploded.
