What if there was a better way to get to space? In 1966, the United States Air Force and Lockheed introduced the Star Clipper concept. At the time, it was "an Earth-to-orbit spaceplane based on a large lifting body spacecraft and a wrap-around drop tank."
Unfortunately, the Star Clipper design did not progress far but it did influence the then-emerging Space Shuttle design. How did it do that? Through the Space Transporation System. What was that?
After 1966, NASA began a space program that included a permanently manned space station, a small base on the moon, and the hopes of a soon-to-be crewed mission to Mars. This is where the concept of a "logistics vehicle" emerged in order to lower the cost of space station operations. The vehicle's role would be focused on changing crews on the space station on a weekly basis.
In 1967, a whole-day meeting was arranged to evaluate the logistics vehicle concept. The Air Force and NASA had already joined forces on a study of existing technologies in the "Integrated Launch and Re-entry Vehicle" project, or ILRV. The meeting resurfaced the ILRV research calling on the same industry partners to present different logistics vehicle concepts.
That's when Lockheed submitted Star Clipper while General Dynamics introduced their Triamese and Chrysler SERV. Soon, NASA's own teams joined in on the fun supporting mostly the "classic" flyback design.
Then in 1971 something happened that changed everything and brought the Star Clipper to the forefront. The maximum development budget was reduced by 50% by the Office of Management and Budget, going from a whopping $10 billion to a mere $5 billion.
This is when the Star Clipper became the most viable option as the costs for a stage-and-a-half design were much lesser because it involved the engineering of only one spacecraft. Despite this, in the end, it was not Lockheed's version that would eventually be chosen to be built, but North American Aviation's take on the concept.
For a glimpse at the spacecraft of the future, you may want to read this article.