21. NASA also found slight singeing of the O-ring seals of nozzle segments taken from recent back-to-back shuttle flights. 22. When the stopper is down, the O-ring seals the drain to keep water from seeping past the stopper. 23. Solid rocket boosters are recovered after each shuttle launch, and the O-ring seals are examined carefully by NASA engineers. 24. Cylinder seals are a form of impression seal, a category which includes the stamp seal and finger ring seal . 25. The obstruction turned out to be a piece of debris _ an O-ring seal from an earlier supply ship. 26. NASA's next space shuttle flight has been delayed indefinitely because of concern over O-ring seals in the rocket boosters. 27. The cylinder liners are made of centrifugally cast iron, two rubber rings seal the liners off from the crankcase. 28. Other cartridges may be difficult to eject, and some have been known to puncture the O-ring seal and create leaks. 29. O-ring seals in the booster nozzle joints of Atlantis and Discovery were singed by hot rocket gas earlier this summer. 30. Then, hot rocket gas seeped through thermal insulation surrounding O-ring seals in the solid-fuel rocket boosters of Atlantis and Discovery.
