While the Space Shuttle program failed to achieve its stated goals of rapid, low-cost reuse of orbital spacecraft, it was nonetheless an extremely successful program, filling a niche role and allowing the further development of reuse technology.
One of the Space Shuttle’s biggest selling points was that it could be a “space pick-up truck” – it could carry both crew and oversize cargo into orbit, allowing for cargo to be serviced or installed in orbit after it was delivered. This capability was used extensively for the delivery and installation of modules of the International Space Station.
The Shuttle carried many ISS modules into orbit, and provided astronauts to complete the modules’ installation on the station. While the ISS could have been built without the Shuttle, it would have required autonomous docking of all the modules, a technology which at the time the United States did not possess. Given the value of the International Space Station as a research and technology test bed, this contribution in itself justifies the success of the Shuttle program.
This is not the only major contribution of the Shuttle program, however. As an experimental foray into spacecraft reuse, it allowed scientists to learn valuable lessons to make reuse successful and economically viable in the future. Lessons learned from attempts at reuse of the Shuttle’s Solid Rocket Boosters led to the powered, return-to-launch-site landing techniques employed today by SpaceX and Blue Origin, both of whom have successfully reflown boosters. It’s new heatshield and unique reentry profile also helped scientists develop a greater understanding of hypersonic and high-altitude flight, allowing for the development of more advanced air and spacecraft, like the Air Force’s X-37B.
While the Shuttle no longer has a place in modern spaceflight, it was in fact the Shuttle itself that helped create the technologies that led to its obsolescence. Despite its shortcomings, the Space Shuttle program made a major contribution to the advancement of human spaceflight, and should be regarded as a success as a result.