AKA: Reusable Orbital Module-Booster & Utility Shuttle. Status: Study 1964. Payload: 450,000 kg (990,000 lb). Thrust: 79,769.00 kN (17,932,784 lbf). Gross mass: 6,363,000 kg (14,028,000 lb). Height: 29.00 m (95.00 ft). Diameter: 24.00 m (78.00 ft). Apogee: 185 km (114 mi).
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 problems. During ascent, the plug nozzle provides automatic altitude compensation and therefore good performance at both sea level atmospheric pressure and in space. For final orbital insertion, 16 of the 36 engines would burn for 3 seconds to provide the required velocity. ROMBUS would typically spend 24 hours in orbit before the ground track passes close enough to the launch site for de-orbit. Parachutes and (beginning at 0.73km altitude-) retrorockets would be used to safely land the vehicle. The final touchdown burn would be provided by four engines running at 25% thrust for approximately twelve seconds.
To reduce the size and weight of the vehicle, the hydrogen fuel was to be stored in eight external jettisonable tanks. The tanks were jettisoned 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.
LEO Payload: 450,000 kg (990,000 lb) to a 185 km orbit at 28.00 degrees. Development Cost $: 4,088.000 million. Launch Price $: 25.000 million in 1964 dollars in 1964 dollars.
Stage Data - Rombus
|Rombus core LOx/LH2 propellant rocket stage. 36 x plug-nozzle engines (20 atm chamber pressure, 7:1 mixture ratio).|
Rombus SSTO Launch Vehicle
Credit: © Mark Wade
|Rombus Launch Site|
Rombus SSTO Launch Vehicle Cutaway
Credit: © Mark Wade