I've seen a lot on the forums about SSTO's (Single Stage To Orbit spacecraft). But what's the purpose? To reduce the cost of spaceflight. Here's the challenge: KSP needs a new space station in Kerbin Orbit on a tight budget, and it needs to be put there one module at a time with a single cargo craft. This craft must launch from the launchpad or runway only once. It will place a module of the space station in orbit, then return to KSC where it will be refueled, and another payload attached, all w