Encyclopedia Astronautica

Rombus SSTO
Rombus SSTO Launch Vehicle
Credit: © Mark Wade
Rombus Launch Site
Credit: NASA
Rombus SSTO
Rombus SSTO Launch Vehicle Cutaway
Credit: © Mark Wade
American SSTO VTOVL orbital launch vehicle. Bono original design for ballistic single-stage-to-orbit (not quite - it dropped liquid hydrogen tanks on the way up) heavy lift launch vehicle. The recoverable vehicle would re-enter, using its actively-cooled plug nozzle as a heat shield.

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

  • Stage 0. 8 x Rombus Tank. Gross Mass: 107,501 kg (236,999 lb). Empty Mass: 18,143 kg (39,998 lb). Thrust (vac): 0.0000 N ( lbf). Isp: 455 sec. Burn time: 130 sec. Isp(sl): 359 sec. Diameter: 7.62 m (24.99 ft). Span: 7.62 m (24.99 ft). Length: 30.49 m (100.03 ft). Propellants: Lox/LH2. No Engines: 0. Engine: None. Status: Study 1964. Comments: 8 of these liquid hydrogen tanks would be mounted around the core of Rombus and stage in pairs at 130 seconds, 196 seconds, and 300 seconds after launch.
  • Stage 1. 1 x Rombus. Gross Mass: 5,102,041 kg (11,248,075 lb). Empty Mass: 306,175 kg (675,000 lb). Thrust (vac): 101,900.000 kN (22,908,000 lbf). Isp: 455 sec. Burn time: 215 sec. Isp(sl): 359 sec. Diameter: 16.00 m (52.00 ft). Span: 24.39 m (80.01 ft). Length: 28.96 m (95.01 ft). Propellants: Lox/LH2. No Engines: 1. Engine: Plug-Nozzle Rombus. Status: Study 1964. Comments: 36 x plug-nozzle engines (20 atm chamber pressure, 7:1 mixture ratio).

AKA: Reusable Orbital Module-Booster & Utility Shuttle.
Status: Study 1964.
Gross mass: 6,363,000 kg (14,028,000 lb).
Payload: 450,000 kg (990,000 lb).
Height: 29.00 m (95.00 ft).
Diameter: 24.00 m (78.00 ft).
Thrust: 79,769.00 kN (17,932,784 lbf).
Apogee: 185 km (114 mi).

More... - Chronology...

Associated Countries
Associated Spacecraft
  • Project Selena American manned lunar base. Study 1964. Bono's enormous ROMBUS booster could fly all the way to the lunar surface and back if low Earth orbit rendezvous and propellant transfer were used. He therefore proposed using the booster to establish a lunar base. More...
  • Project Deimos American manned Mars expedition. Study 1964. Project Deimos was a Mars expedition proposed by Philip Bono in the mid-1960's. It would use the huge Rombus single-stage-to-orbit booster, refueled in earth orbit, as the propulsion system to Mars and back. More...

Associated Engines
  • None Indicates that the stage shown is a propellant tank. The engine on another stage is drawing propellants from this tank. Performance shown is for that of the engine on the other stage. First flight 1964. More...

See also
  • SSTO Category of launch vehicles. Single Stage To Orbit. More...
  • VTOVL The concept of a reusable single-stage-to-orbit Vertical Take-Off Vertical Landing (VTOVL) launch vehicle that would reenter and return to its launch site for turnaround and relaunch was first proposed by Philip Bono in the 1960's. The appealing simplicity of the concept has been offset by the technological risk in developing it. The problem with any single-stage-to-orbit concept is that if the empty weight of the final vehicle has been underestimated it will not be able to deliver any payload to orbit, or even reach orbit. Since weight growth of up to 20% is not unknown in aerospace projects, this is a very real threat which has made both NASA and private investors reluctant to invest the billions of dollars it would take to develop a full-scale flight vehicle. More...

Associated Manufacturers and Agencies
  • Douglas American manufacturer of rockets, spacecraft, and rocket engines. Boeing Huntington Beach, Huntington Beach, CA, USA. More...

  • Gatland, Kenneth and Bono, Philip, Frontiers of Space, Macmillan, New York, 1969.
  • Bono, Woodworth & Ursini, "Reusable Booster for Logistics and Planetary Exploration", IAF XVth International Astronautical Congress Proceedings, 1964/p.547.
  • "All-Purpose Moon Vehicle", Space World, 1964/December/p.16.
  • Bono, Philip, "ROMBUS concept", Astronautics & Aeronautics, 1964/January/p.28.

Associated Stages
  • Rombus Lox/LH2 propellant rocket stage. Loaded/empty mass 5,102,041/306,175 kg. Thrust 101,900.00 kN. Vacuum specific impulse 455 seconds. 36 x plug-nozzle engines (20 atm chamber pressure, 7:1 mixture ratio) More...
  • Rombus Tank Lox/LH2 propellant rocket drop tank. Loaded/empty mass 107,501/18,143 kg. Vacuum specific impulse 455 seconds. Eight of these liquid hydrogen tanks would be mounted around the core of Rombus and stage in pairs at 130 seconds, 196 seconds, and 300 seconds after launch. More...

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