DOUGLAS “R.O.M.B.U.S.” & PROJECT SELENA [1963]
Notes:
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ROMBUS could fly all the way to the lunar surface and back if low Earth orbit (LEO) rendezvous & propellant transfer were used. The fully loaded LH2 tanks would be transferred from from ROMBUS tankers to the lunar landing ROMBUS, hence the need for pumping low-density hydrogen is circumvented. The tankers would also carry oxygen in their payload compartment which is pumped to the lunar vehicle tank.
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This illustration depicts an expendable ROMBUS landing on the Moon. Only two LEO tanker flights would be required for soft-landing a 4,536kg payload on the lunar surface. The empty spacecraft has a mass of 306.233t and the structure + tankage might be transformed into a lunar habitat.
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Nine LEO tanker missions would be required to land a 226.8t payload on the lunar surface and return the vehicle to Earth with 22.68t of cargo. After ROMBUS has landed on the Moon, its LH2 tanks (now empty) could be transformed into habitation modules for a moonbase. ROMBUS would have to carry more LH2 coolant (+5,670kg) to survive the high-velocity atmospheric reentry. But this difference would still be far smaller than the 313t of propellant required to propulsively cancel the 3,048m/s difference between reentry from lunar transfer orbit and reentry from low Earth orbit. The Douglas engineers did not expect the thermodynamics to cause significant problems, although they did note that the point of maximum heating on the ROMBUS plug-nozzle underside is different during lunar return: some additional LH2 might be diverted by suitable valving to cope with this problem. The underside of the vehicle would also have to be beefed up to cope with the additional dynamic pressure during reentry from lunar transfer orbit.
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Bono's Project Selena called for the establishment of a 1000-man lunar colony by 1984. The main purpose of Selena was to support three manned Mars missions by 1986 and about half of the payloads would be dedicated to the “Deimos” follow-on missions. The total mass of the lunar cargo was a staggering 3295 metric tons, requiring 1341 ROMBUS launches and 1011 cargo/propellant transfer operations in low Earth orbit over 8.5 years. A fleet of 10-15 ROMBUS vehicles would have to perform 330 lunar landing missions to deliver the crews, cargo and propellant. The estimated average vehicle lifetime was 40 flights.
"All-Purpose Moon Vehicle"
Space World 1964/December/p.16
"Reusable Booster for Logistics and Planetary Exploration"
Bono,Woodworth & Ursini, IAF XV:th INTERNATIONAL ASTRONAUTICAL CONGRESS PROCEEDINGS 1964/p.547