ROMBUS. Reusable Orbital Module Booster and Utility Shuttle. Massive. A Single Stage To Orbit (SSTO) launch vehicle from the mid-1960s, when SSTO seemed possible. We now know that the numbers don't work out very well for the SSTO concept, though there are still true believers. Engineers argue endlessly about SSTO possibilities. Rombus, featuring drop away liquid hydrogen tanks, would have emitted about 4 kilotons of water vapor into the middle atmosphere each launch. The ROMBUS mesospheric contrails would have been spectacular, perhaps lasting for days.