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Aviation History
1961
1961 - 0811.PDF
FIGHT, 15 June 1961 821 Missiles and Space flight F-l npHIS IS THE DESIGNATION of the biggest liquid-propellant I rocket engine under development outside the Soviet J__ Union. Rocketdyne Division of North American Aviationhave given new details of this powerplant in a paper read recently by David E. Aldrich, F-l programme manager, and DominickJ. Sanchini, F-l assistant programme engineer. A condensed version of their text follows.A comparison of satellite weights announced by the Soviet Union with those launched by the United States demonstrates a significantdifference in capabilities. The first two Soviet satellites weighed 184 and ],1201b, respectively; our first two weighed 31 and 3.251b, respectively.This difference in weight-lifting capability has continued at a similar magnitude. Our first artificial planet. Explorer IV, weighed about131b; the first Soviet artificial planet weighed about 3,1001b. Our Discoverer series of recovery vehicles weighed about 1,7001b. therecovery vehicles launched by the Soviet Union weighed about 10,0001b. Thus, it was quite obvious that we should "leapfrog" the next stepin booster technology and begin immediately the development of very- high-thrust engines. Manned Earth-orbital flight and instrumentedprobes of the Moon and nearby planets are planned for the early 1960s; and relatively large, manned, Earth-orbiting laboratories, mannedexploration of the Moon, and manned orbital trajectories of the nearby planets are planned for the late 1960s. Present vehicles basicallyperform reconnaissance missions with instrument payloads. For Earth- orbital missions, the payload weights will be in the order of tens ofthousands of pounds. For lunar and planetary reconnaissance, the payloads will be in the order of thousands of pounds. These demandthe Saturn series of vehicles, boosted by eight 188,0001b engines. During the late 1960s the payloads to be lifted into Earth orbit arein the order of hundreds of thousands of pounds; for lunar landings and return, and for planetary orbiting, the payloads will be in the order oftens of thousands of pounds. During this period, it is expected that manned space laboratories and lunar bases will be established whichwill require repeated missions to renew supplies and change personnel. The vehicles accomplishing these missions will be the "wagon trains" ofthe space age. These are the Nova vehicles, using clusters of F-l engines. We can illustrate the capabilities of Nova-type vehicles powered withhigh-energy upper stages by discussing several typical missions which could be accomplished with the same booster with six F-] enginesclustered for a takeoff thrust of 9,000,0001b. A vehicle of this type would be capable of lofting up to 400,0001binto a low orbit. For example, a mission could be to establish a manned laboratory for astronomical and Earth observations, as well as otherscientific and technical studies. Or large "space platforms" could be assembled in 400,0001b increments by multiple-launch and rendezvoustechniques. In addition, a large lunar vehicle, or vehicles for manned interplanetary flight, could be assembled and fuelled while in a parkingorbit. The F-l engine would considerably reduce the number of missions required. Another vehicle would be capable of launching a 65-ton* payloadinto a 24hr orbit for astronomical or weather observation, Earth sur- veillance, navigation, and radio and TV communications. Such cap-sules, capable of being repaired and maintained, could very well be an economical solution to the lofting of satellite systems. A vehicle of this type could also place up to 90.0001b into a Marsorbit. With such a payload capability, a capsule could be well equipped with instrumentation and telemetering equipment; it could launch robotprobes to the surface of the planet and relay the telemetered informa- tion back to Earth stations. Alternatively, we would be capable ofaccomplishing a manned lunar landing and return, with an Earth- landing weight of approximately 20,0001b. The Rocketdyne F-l engine, being developed under NASA contractfor a Nova-type vehicle, is the direct result of these requirements. * The authors' tons are of 2,0001b—Ed. The man at bottom centre gives scale to the vast test stand now com- pleted at Edwards for the static firing of twin F-l engines Although the contract for the development of the engine was signed inJanuary 1959, the development of a single-chamber, 1.500,0001b engine was already well started. Under the Air Force Rocket Engine Advance-ment Programme, studies of the feasibility of rocket engines up to one million pounds thrust were begun as early as 1955. These culminatedin 1957 with a detailed analysis of a single-chamber, million-pound engine, with supporting model testing and full-scale thrust chamberdesign. Later in the year the programme was realigned to include three full-scale firing attempts. These tests were concluded in March 1959with a brief mainstage test at 1,000,0001b thrust, demonstrating stable combustion. The basic components of the engine [picture on left—Ed] are atubular-wall thrust chamber, a direct-drive turbopump, a gas generator and their controls. The engine weighs approximately 15,0001b. Forsimplicity and compactness, the turbopump is mounted directly on the thrust chamber. All other components are either mounted on thesetwo assemblies, or are in the plumbing system between them. When the engine is gimballed, the high-pressure ducting is not flexed. Thrust-vector control is achieved by gimballing the entire engine. The high- pressure fuel is used as the hydraulic actuating medium. The thrust chamber assembly consists of a tubular-wall, regenerativelycooled chamber with an uncooled extension, a double-inlet oxidizer dome, four integral fuel valves, and a flat-face injector. The cooledportion extends to a 10:1 expansion area ratio. Its approximate measurements are 40in chamber diameter, 9ft 6in nozzle exit diameter,and lift length. The chamber is designed for the attachment of seg- mented, uncooled nozzle extensions to facilitate transportation, andto accommodate any area ratio required by the mission up to 16:1. Two tons per second of liquid oxygen and nearly one ton per secondof narrow-cut kerosene (RP-1) are burned in the combustion chamber. The oxygen usage rate is equivalent to that of 60m people in normalbreathing, and in 3sec of mainstage operation, the F-l uses as much fuel as the average automobile uses in one year. The oxidizer is fedthrough dual inlets to the dome to ensure even distribution to the injector. It passes through feed holes, and is injected through a patternof 2,600 orifices into the combustion chamber. The fuel is also fed through dual inlets to a chamber feed manifold.From here, the fuel flows through alternate tubes the length of the chamber, and then returns to the collector manifold. The flow contin-ues through four fuel valves, spaced at 90° around the chamber, into an injector feed manifold. This distributes the fuel through 32 spokesinto the injector, from which it passes through approximately 3,700 orifices into the combustion chamber. The location of the valves down-stream of the chamber tubes provides a greater degree of control in timing and sequencing the fuel for engine starting. It also provides arepeatable minimum cutoff impulse. In the interests of simplicity and reliability, the turbopump is adirect-drive unit. The fuel and oxidizer pumps are driven by a velocity- compounded turbine, which at rated conditions develops approximately60,000 h.p. The assembly is about 4ft in diameter, 5ft long, and weighs approximately 2,5001b. The oxidizer is supplied to the pump through asingle inlet, in line with the main shaft, and is discharged radially through dual outlets. The dual-outlet design balances centrifugalloads and minimizes pump diameter. The fuel pump has dual inlets and outlets for balanced load distribution and minimum size. The gas generator burns about 2 per cent of the total propellantsused in the engine. The partially spherical gas generator is approxi- mately lOin diameter. The gas-generator design makes use of a double-wall combustion chamber, through which the fuel flows to cool the body regeneratively. This feature eliminates a hot outer surface which couldignite leaking propellants. and it reduces heat radiation to adjacent components. Layout of the F-l is evident from the full-scale mock-up
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