One of paired rubber seals (primary and back-up) on the joints of a solid rocket booster for the space shuttle. The O-rings, each with a diameter of 71 mm, prevent hot gases from escaping through the joints of the rocket's four segments. An investigation revealed that the Challenger space shuttle disaster in 1986 was caused by a failure of both rings at the ‘aft field’ joint between the bottom segment and the one above on the right booster. The failure was thought to be due to a faulty design of the O-rings that proved unable to withstand the combination of previous use and the launch vehicle's dynamic bending during launch.
Subjects: Astronomy and Astrophysics.