Launch vehicles that weren't

This site, invaluable to space historians, collects launch vehicles, especially reusable launch vehicles (RLVs), proposed from 1963 to 2001. RLVs seem much more logical than throwaway boosters, but it turns out actually building one is very, very hard. Planners who hope to build them in the future need to apply all the lessons learned (often expensively) in the past.