Space Shuttle It weighed 3.4 metric tons (7,500 lb) less than the last run of lightweight tanks, allowing the Shuttle to deliver heavy elements to ISS's high inclination orbit. As the Shuttle was always operated with a crew, each of these improvements was first flown on operational mission flights. The solid rocket boosters underwent improvements as well. Design engineers added a third O-ring seal to the joints between the segments after the 1986 Space Shuttle "Challenger" disaster. Several other SRB improvements were planned to improve performance and safety, but never came to be. These culminated in the considerably simpler, lower cost, probably
Space Shuttle at Edwards Air Force Base, California, or use one of the multiple alternate landing sites around the world. A landing at any site other than Kennedy Space Center meant that after touchdown the Shuttle must be mated to the Shuttle Carrier Aircraft and returned to Cape Canaveral. Space Shuttle "Columbia" (STS-3) once landed at the White Sands Space Harbor, New Mexico; this was viewed as a last resort as NASA scientists believed that the sand could potentially damage the Shuttle's exterior. There were many alternative landing sites that were never used. An example of technical risk analysis for a STS