Shuttle-C

The Shuttle-C is a proposed expendable heavy-lift variant of the Shuttle, replacing the orbiter with a cargo pod. Private investors in California have tried to raise money for a Shuttle-C facility at Vandenberg AFB. The payload to low Earth orbit (LEO) would be 70-80t, or perhaps 15t to the lunar surface using two Centaur G upper stages. As with Energia, high development costs and little interest from private investors (neither rocket can launch comsats and other commercial payloads) appears to rule out the Shuttle-C.

Designing a new launcher, even from off-the-shelf STS components, would be an expensive task. By its very nature, it would only pay off if amortized over a number of launches. However, after the first flight, putting together a shuttle-derived HLV will be well within the resources of the Artemis Project.