INTRODUCTION TO THE SATURN PROGRAMA definite need to loft large payloads into orbit was foreseen by the Wernher von Braun organization even before the United States orbited its first artificial satellite on January 31, 1968. Initial planning for launch vehicles having Payloads of 20,000 to 40,000 pounds for orbital missions, or payloads of 6,000 to 12,000 pounds for escape missions was started in April 1957. The von Braun group, then working with the Army Ballistic Missile Agency (ABMA), submitted a "Proposal for a National Integrated Missile and Space Vehicle Development Program" to the Department of Defense in December 1957. The proposal indicated a need for a booster in the 1.5 million pound thrust class. After studies concluded that a clustered booster of 1.5 million pounds thrust was feasible, on August 15, 1958, representatives of the Advanced Research Projects Agency (ARPA) ordered the beginning of a research and development project. This project evolved into the Saturn Program.
The initial objective of the research and development program was to prove that the engine clustering technique, using existing hardware, could furnish large amounts of thrust. This was demonstrated by building and testing a single non-flight stage at Redstone Arsenal, Alabama.
Studies also showed that liquid oxygen and fuel tanks, previously developed for the Redstone and Jupiter missiles, could be modified and used for the proposed booster. It was also determined that the existing S-3D engine used on the Thor and Jupiter missile could be modified to produce an increased thrust of 188,000 pounds. Rocketdyne, a division of North American Aviation, Inc., received a contract to uprate the Thor-Jupiter engine. After redesign, simplification, and modification, the engine was identified as the H-1 engine. Initially, the thrust of the H-1 engine was 165,000 pounds; at the present time it is 200,000 pounds; in the future it will be 205,000 pounds.
Concurrent with H-1 engine development, studies were conducted to determine the feasibility of producing a large single-chamber rocket engine capable of producing very high thrust. From these advanced studies, the 1.5 million pound thrust F-1 engine was conceived, and subsequently used as the power plant for the later Saturn boosters.
In October 1968, ARPA changed from a ground test program for proving the engine clustering concept to a program requiring the development of a reliable, high-performance booster which would serve as the first stage of a multistage vehicle capable of performing advanced space missions. This vehicle was tentatively identified as Juno V. The research group also initiated a complete vehicle study so that selection and development of an upper stage could begin.
Early in 1959, the Juno V designation was changed to Saturn, a name suggested by the relationship of the planet Saturn to the planet Jupiter. As Saturn is the next planet after Jupiter in the solar system, the Saturn rocket was the next von Braun group project following the completion of the Jupiter missile development.
Late in 1959, two decisions of far-reaching significance were made:
- The Department of Defense decided that it had no immediate use for a large rocket, and in view of the emerging national space program, turned the Saturn project over to the newly-formed National Aeronautics and Space Administration (NASA).
- NASA formed a Saturn Vehicle Evaluation Committee (the Silverstein Committee) composed of NASA and Defense officials. The committee recommended that all upper stages of Saturn vehicles be powered by the high energy propellant combination of hydrogen and oxygen, and that a new hydrogen engine be developed.
Development of the J-2 engine and three upper stages resulted from these decisions. A building block approach to a series of successively larger vehicles was outlined by NASA early in 1960. The first, Saturn I, was to be a three- stage vehicle, ten of which were planned. Subsequently, by increasing the thrust of the second stage, the planned third stage was eliminated.
During 1960, Douglas Aircraft Company, inc. was selected to build the second stage of Saturn I. Designated as the S-IV stage, it was powered by six Pratt and Whitney RL10A-3 engines. Rocketdyne was chosen to develop the new hydrogen fueled J-2 engine to be used in later vehicles of the Saturn program.
In the spring of 1960, successful static firings of the S-I stage took place to verify the clustered engine technique as a basic consideration for still larger vehicles.
At mid-year 1960, the von Braun development group handling Saturn work was formally transferred to NASA, and became the nucleus of the newly created George C. Marshall Space Flight Center.
Chrysler Corporation was anwarded a contract in June 1961 to qualify and test S-I stage engine, hydraulic, mechanical, and structural components.
In May 1961, the late President Kennedy's challenge to the nation to place astronauts on the moon in this decade created an immediate necessity for a launch vehicle considerably larger than the Saturn I.
Following more than six months of intensive study, NASA announced in January 1962 that the next Saturn vehicle would be the Saturn V with a ground stage thrust of 7.5 million pounds five times that of Saturn 1. It would be capable of placing more than 120 tons into earth orbit. This larger vehicle would have two new upper stages: a new S-II second stage and S-IVB third stage, both utilizing the new J-2 engines. The S-IVB stage would be an adaptation of the S-IV stage already developed for the Saturn I.
As the project to land Americans on the moon was studied, it was determined that the nation would not build one huge rocket for a direct flight from earth to the moon's surface. Instead, two rendezvous approaches were studied:
- Bringing together two Saturn V payloads in earth orbit to form a moon ship, and then proceed to a moon landing.
- Launching a single Saturn payload into lunar orbit, from which a small landing craft would be dispatched to the moon's surface, and later rendezvous with the mother ship still in lunar orbit.
Both the earth orbital rendezvous and lunar orbital rendezvous missions would use the Saturn V launch vehicle.
Finally, in July 1962, it was announced that on the basis of cost, safety, and time, the lunar orbit rendezvous method was favored. This decision entailed the use of still another launch vehicle with a capability between the Saturn I and the Saturn V to test the complete Apollo spacecraft in earth orbit as soon as possible. The new vehicle was identified as the Saturn IB, and would be comprised of a modified Saturn I first stage (S-IB) and Saturn V third stage (S-IVB).
The Saturn IB will permit flight testing of the complete spacecraft about one year earlier than would have been possible had NASA waited for availability of the Saturn V.
As the plan stood, the Saturn I would be used to place early, unmanned Apollo command and service modules into earth orbit; the Saturn IB would launch those two modules plus a moon landing craft, lunar excursion module, into earth orbit for astronaut training and rendezvous practice; and the Saturn V would provide power for the lunar landing. Thus, by marrying the elements of Saturn I and Saturn V to form the Saturn IB, manned earth orbital rendezvous flights could begin a year earlier without the expense of a completely new development program.
Saturn I
While plans for the lunar mission were progressing, the Saturn I project made history. On October 27, 1961, the first Saturn I booster was flight-tested successfully from Kennedy Space Center (KSC). The first flight booster with dummy upper stages was called SA-1. This vehicle was followed by successful flights of SA-2 on April 25, 1962, SA- 3 on November 16, 1962, and SA-4 on March 28, 1963.
The SA-5 vehicle, combining the first stage S-l with a S-IV stage, was successfully launched on January 29, 1964, with both stages functioning perfectly to place a 37,700 pound payload into earth orbit. SA-6, launched on May 28, 1964, and SA-7, launched on September 18, 1964, each placed "unmanned" boilerplate configurations of Apollo spacecraft into earth orbit.
SA-9, launched on February 19, 1965, was the first Saturn I vehicle to launch a Pegasus micrometeoroid detection satellite into earth orbit to measure the amount and size of space particles.
The SA-8 and SA-10 Saturn I vehicles were successfully launched from KSC on May 25, 1965, and July 30, 1965, respectively, to complete the test and launch program with an unprecedented 100 per cent record of success.
The Saturn IB
Based upon the technology of the Saturn I program, the Saturn IB uses the S-IB first stage which is a modified version of the S-I stage, together with the S-IVB second stage, an upgraded version of the S-IV stage, and an Instrument Unit originally designed for the future Saturn V launch.
The S-I first stage was redesigned in several areas by NASA and Chrysler for its expanded role as the Saturn IB booster. Basically, it retained the same shape and size, but required some modification for mating with the S-IVB stage, which has a greater diameter and weight than the S-IV stage.
Stage weight was cut by more than 20,000 pounds to increase payload capacity. This reduction was accomplished by a new fin design, removing hydrogen vent pipes and brackets unnecessary to the new design, resizing machined parts in the tail section assembly, redesigning the spider beam, and modifying the propellant tanks. The Rocketdyne H-1 engine was uprated to 200,000 pounds of thrust, compared with 188,000 pounds of thrust for each engine in the Saturn I, Block II. The engines will be uprated again to 205,000 pounds beginning with the SA-206.
Early development of the S-IVB stage to meet the schedule of the Saturn IB was possible by drawing on the technology gained from Douglas development of the S-IV stage for the Saturn I.
The 200,000 pound thrust Rocketdyne engine more than doubled the S-IV stage thrust capability. Development of the J-2 engine also drew heavily upon large-engine technology experience in hydrogen pumping acquired under AEG sponsored programs.
The Instrument Unit used on the Saturn IB is nearly identical to that intended for the Saturn V. Equipment used in the Saturn I Instrument Unit program was intended to test the concepts for design of the Saturn V Instrument Unit. There are a few carryover components; however, later Saturn I vehicles used an inertial platform and control computer similar in design and operation to that being used in the Saturn IB.
The guidance computer used in the early Saturn I vehicle was an adaptation of a computer developed by International Business Machines for use in Titan II. For the Saturn IB, it is replaced by an IBM computer of completely new design which incorporates the added flexibility and extreme reliability necessary to carry out the intended Saturn IB missions.
The equipment used in the Instrument Unit represents a unique blend of old and new technologies. Due to military requirements, early missile programs were concerned with accurate delivery of inanimate payloads after a relatively short period of powered flight. Automatic control systems were the prime requirements to provide guidance and control for these types of military vehicles.
The addition of man as an extremely important consideration in Saturn IB design meant that new systems had to be developed, while skillfully adapting the best features of older systems for longer durations, varied objectives, and an overriding concern for the safety of the human passenger.
Saturn V
Saturn V, third and largest member of the Saturn family, is a three-stage vehicle capable of sending a 45-ton payload to the moon, or boosting as much as 140 tons into low earth orbit. As the Apollo lunar launch vehicle, Saturn V will stand 364 feet high, and when fully fueled will weigh over six million pounds.
The S-IC first stage will be powered by five Rocketdyne F-1 engines, each having 1.5 million pounds of thrust, for a total of 7.5 million pounds. This stage will be 33 feet in diameter and 138 feet long, and will use liquid oxygen and RP-l (kerosene) as propellants.
The S-II second stage will also be 33 feet in diameter, with a total length of 81.5 feet, and will use liquid oxygen and liquid hydrogen propellants. This stage will have a total thrust of one million pounds provided by five 200,000 pound thrust Rocketdyne J-2 engines.
The S-IVB third stage, which also serves as the upper stage of the Saturn IB, will be 21.7 feet in diameter and 58.4 feet long, and the hydrogen-fueled J-2 engine will provide 200,000 pounds of thrust. The J-2 engine will be modified to provide an in-space restart capability to meet requirements of the Saturn V lunar launch mission.
The Saturn V Instrument Unit built by IBM is nearly identical to that used on the Saturn IB, with no change in physical dimensions or internal systems; however, minor modifications in instrumentation will be made to meet the Saturn V mission requirements.
Copyright 1997, 1998 by John
Duncan |