NASA started the Space Shuttle design process in 1968, with the vision of creating a fully reusable spaceplane using a crewed fly-back booster. This concept proved expensive and complex, therefore the design was scaled back to reusable solid rocket boosters and an expendable external tank. The Shuttle was more expensive to operate over its 30-year lifetime than an expendable launch system would have been. Space Shuttle "Columbia" launched and landed 27 times and was lost with all crew on the 28th landing attempt; "Challenger"