Shuttle-C

The Shuttle-C was a NASA proposal to turn the Space Shuttle launch stack into a dedicated unmanned cargo launcher. This would use the Space Shuttle external tank and Space Shuttle Solid Rocket Boosters (SRBs), combined with a cargo module that would attach to Shuttle hardpoints (the bipod, etc.) and include the Space Shuttle Main Engines. Various Shuttle-C concepts were investigated between 1984 and 1995.

The Shuttle-C concept would theoretically cut development costs for a heavy launch vehicle by re-using technology developed for the shuttle program. The proposal involved using, at various times, existing spaceframes, Space Shuttle Main Engines that had reached maintenance lifetime limits, and spare navigation computers. One proposal even involved converting the Columbia or Enterprise into a single-use cargo launcher. Before the loss of Space Shuttle Challenger, NASA had expected about 14 shuttle flights a year. In the aftermath of the Challenger incident, it became clear that this launch rate was not feasible for a variety of reasons. With the Shuttle-C, it was thought that the lower maintenance and safety requirements for the unmanned vehicle would allow a higher flight rate.

There were two development phases planned. The first consisted of deciding the shape and size of the cargo carrier. NASA studies showed that a small but functional carrier would be most efficient for launches.

In the early 1990s, NASA engineers planning a manned mission to Mars included a Shuttle-C design to launch six non reusable 80 ton segments to create two Mars ships in Earth orbit. After President George W. Bush called for the end of the Space Shuttle by 2010, these proposed configurations were put aside.

NASA resurrected the idea of the Shuttle-C concept in the form of the Shuttle-Derived Launch Vehicle. The proposal was for a 120 metric tonne payload with an in-line design, now known as Ares V. This design would have been significantly different in layout from Shuttle-C. Shuttle-C comes in various configurations: one variant has three Orbiter main engines, while the other has two. Only one known mock-up of Shuttle-C exists, created by Boeing for engineering development tests in 1989.

Shuttle-Derived Heavy Lift Launch Vehicle is another similar proposal based on the Shuttle-C concept which uses existing Space Shuttle systems with a new cargo vehicle, however the system would not be reusable.