DOUGLAS “R.O.M.B.U.S.” [1963]
Notes:
http://sites.google.com/site/spaceodysseytwo/space60s/rombus2.jpg>
In 1964, Phil Bono of Douglas Aircraft Co. proposed a low-cost heavy lift VTVL SSTO RLV plus lunar base as a logical follow-on to the Apollo project. Bono's "Reusable Orbital Module-Booster & Utility Shuttle" (ROMBUS) concept was based on his patented plug nozzle rocket engine design, which doubles as a heat shield during atmospheric reentry. The vehicle's base-first reentry mode assures a stable condition during recovery since the mass of the engine is very high, i.e. far aft center of gravity. The plug nozzle would be cooled by circulating liquid hydrogen through the same regenerative system used for cooling the engines and base of the vehicle while the engines are operating during ascent. Mixture ratio of liquid oxygen to hydrogen was raised to 7:1 -- about as close as one can get to the stoichiometric value of 8:1 without running into combustion chamber cooling problem. During ascent, the plug nozzle provides automatic altitude compensation and therefore good performance at both sea level atmospheric pressure and in space. Parachutes and (beginning at 0.73km altitude-) retrorockets would be used to safely land the vehicle. To reduce the size and weight of the vehicle, the hydrogen fuel was to be stored in eight external jettisonable tanks. The tanks were discarded and then recovered by parachute as they were depleted during ascent to orbit. The earlier fully reusable "ROOST" concept was thus rejected since it did not leave much margin for growth in vehicle structure mass. The total life cycle cost would have been $10 billion [1964 $'s] over 10 years including $4.088 billion for the development program. Bono mentioned the following SSTO RLV-specific advantages : increased reliability since each vehicle has a history, reduced development cost & complexity vs. multi-stage vehicles, economies of scale possible since plug nozzle engine units & tanks could be mass produced. The estimated direct launch cost was $22.4 million (=$28/lb. to a 568km orbit at 1964 economic conditions) and the planned vehicle turnaround time about 76 days. Bono also mentioned a direct operations cost goal of $12/lb (5-6 reuses) - $5/lb (>20 reuses) for a vehicle payload capability of 450t by the year 1975. In comparison, the Saturn V was then expected to cost $150-250/lb. The vehicle would have used the same Kennedy Space Center facilities as the Saturn boosters, although a new launch pad would have been required (below).
http://sites.google.com/site/spaceodysseytwo/space60s/rombus1.jpg>
Liftoff Thrust: 80.1 MN. Total Mass: 6,350.3t. Total Length: 29m.
Payload capability: 362,274kg to a 568km Earth orbit.
Stage Number 1: ROMBUS. 36 x plug-nozzle engines (3000psia pressure, 1:7 mixture ratio). Gross Mass: 6,350.3t incl. ~5,000t LOX. Empty Mass (core vehicle only): 306.175t. External fuel tank mass: (18.143t + 89.358t of LH2 fuel) * 8. Liftoff Thrust: 80.1 MN. Isp: 455s [vac.]. Length: 29m. Width: 24.4m. Propellants: LOX/LH2.
Bono, Astronautics & Aeronautics 1964/January/p.28
"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