-Defining the Army/Navy Jupiter
–Jupiter in Cape Canaveral Hanger
As it began work on Jupiter, GMDD was expanded, to 1,600 personnel, and in February 1956 renamed Army Ballistic Missile Agency (ABMA). ABMA, still based at Redstone Arsenal near Huntsville, Alabama, maintained a core of 500 scientists and engineers, of whom about 100 were German émigrés, in its Development Operations Division. Major General John B. Medaris took command of ABMA. Wernher von Braun was the Director of the Development Operations Division, reporting to Medaris.
More than half a dozen “Laboratories” reported to Dr. von Braun. Among them were the Structures and Mechanics Lab headed by Willy Mrazek, the Fabrication Lab headed by Hans Maus, the Guidance and Control Lab headed by Dr. Walter Haeusserman, the Test Lab headed by Karl Heimburg, and the Missile Firing Lab based at Cape Canaveral and headed by Kurt Debus.
A “Research Projects Office”was headed by Dr. Ernst Stuhlinger beginning in 1959. Dr. Stuhlinger was involved in guidance system development prior to that assignment. Within the Structures and Mechanics Lab was the Preliminary Design Section, headed by Dr. Heinz-Hermann Koelle. The basic “system level” designs of Jupiter, Juno, and Saturn would be conceived by this group.
Jupiter began life as a joint Army-Navy project, a result of the negotiations that won its approval. The liquid propellant missile was to be capable of flight from either mobile land launchers or from ships at sea.
As originally conceived for mobile U.S. Army use, the IRBM would have been more than 28 meters (92 feet) long and 2.41 meters (95 inches) in diameter. The U.S. Navy wanted a missile no greater than 15.24 meters (50 feet) in length.
To shorten Jupiter, ABMA increased its diameter to 2.67 meters (105 inches), but was unable to shrink it down to 15.24 meters length. An early plan to start with a 18.29 meters (60 foot) long, 52.16 tonne (115,000 pound) missile and gradually reduce its length and weight toward 15.24 meters and 38.56 tonnes (85,000 pounds), as operational experience was gained and propulsion was improved, was shelved. ABMA considered a 16.77 meter (55 foot) fixed length, but this would only guarantee 2,408 to 2,593 km (1,300 to 1,400 nautical mile) range. In the end, the length was increased to 17.68 meters (58 feet) to guarantee 2,778 km (1,500 nautical mile) range.
The Navy, never happy with such compromises, understandably reluctant to handle large quantities of liquid propellant on board ships, and aided by further substantial reductions in warhead weight announced by the Atomic Energy Commission in September 1956, was soon speeding up efforts to develop a solid fuel missile, originally named “Jupiter S” that would eventually lead to its “Polaris” operational missile.
In December 1956 the Navy dropped its involvement in Jupiter and the program was transferred to U.S. Air Force control. ABMA was still in charge of development, but the Air Force would control deployment.
Air Force Gains Control
Unassembled Jupiter Tank Structure Visible as Secretary of Defense McElroy Tours Redstone Arsenal
Although the Navy requirements were now moot, only minimal changes could be made to the design given its state of development. The missile length was increased from 16.68 meters (58 feet) to 18.29 meters (60 feet) to provide a performance buffer, but it was too late to change the diameter. Plans for a backup radio-inertial guidance system were dropped in favor of all-inertial guidance.
During most of 1957, Jupiter’s future was uncertain. The Air Force already had Thor and wanted to shelve Jupiter. For months the Air Force did not respond to ABMA requests for information on things like deployment plans. Missile production was halved to one per month.
A review comparing the two missile systems, aimed at determining which to eliminate, was begun.
Jupiter’s end seemed near when, in October 1957, Sputnik shocked the world and settled the matter. Now cancelation was out of the question. There would be two IRBMs, and both would be developed and deployed as rapidly as possible.
The Army’s plans for a fully road mobile missile system were initially maintained, but would eventually, in November 1958, be shelved to be replaced by Air Force plans for static deployment. Static deployment, which tethered missiles to fixed launch sites, meant that Jupiter had to be ready to fire within 15 minutes, to avoid destruction.
The number of test and development missiles was eventually limited to 31. An additional 63 operational missiles would also be manufactured and delivered during 1958-59. ABMA would build the initial missiles at Redstone. Contractor Chrysler would gradually take over production at its Michigan Ordnance Missile Plant in Detroit, Michigan.
The Design
Jupiter was designed to carry a 726 kg (1,600 lb) payload to a target 2,778 km (1,500 nautical miles) distant and impact within 1,500 meters (0.81 nautical miles) of that target. The missile consisted of three main assemblies: the nose cone, the aft unit, and the thrust unit. When the nose cone and aft unit were combined, they were called the “body unit”.
The nose cone was an ablative heat shielded unit that housed the warhead with its fusing and arming systems. At separation, the nose cone with its 750 kg (1,653 pound) W-49 warhead weighed 1,187 kg (2,617 pounds).
The W-49 thermonuclear warhead was rated at 1.45 megatons TNT equivalent. The nose cone was 1.651 meters (65 inches) diameter at its base and 2.477 meters (97.5 inches) long. It had a rounded nose and a convex bulkhead at its base.
The 2.236 meter (88 inch) long aft unit was mounted below the 1.651 meter diameter nose cone and above the 2.668 meter (105 inch) diameter thrust unit. When connected to the nose cone the aft unit created the larger cone shaped body unit. The aft unit contained the missile’s guidance and control equipment, vernier engine, spin rockets, and jet nozzles for attitude control.
The vernier engine was a 227 kgf (500 pound) thrust solid motor that could burn for up to 20 seconds, or until its thrust was terminated by guidance command. Thrust termination was provided by squibs blowing off the motor nozzle. Initial development missiles used a liquid vernier that channeled steam produced when hydrogen peroxide was passed through a solid catalyst.
Body unit attitude control was provided by eight nitrogen gas jets on the aft unit. A pair of solid propellant spin motors mounted on the aft unit would fire to impart a 60 rpm roll to the entire body unit just before the nose cone separated from the aft unit.
ABMA developed Jupiter’s ST-90 all-inertial guidance system platform in-house. Ford Instrument produced the guidance systems, which used air bearing gyroscopes and accelerometers. The system included guidance and control computers. The first ST-90 was delivered in January 1957.
The thrust unit was a 2.668 meter (105 inch) diameter, 12.8 meter (42 foot) long cylinder consisting of a forward RP-1 kerosene fuel tank, aft liquid oxygen (LOX) oxidizer tank, and a tail section housing the main engine. Jupiter’s kerosene tank shared a common bulkhead with its liquid oxygen tank. The tanks were a monocoque aluminum structure with internal ring stiffeners.
A North American Aviation Rocketdyne NAA-150-200-S-3D engine provided Jupiter’s main propulsion. The engine produced 68.03 tonnes-force (150,000 pounds) thrust at sea level and burned for 157.8 seconds. A LOX/RP-1 “Mark 3” fuel-rich gas generator powered two gear-driven turbopumps. One fed RP-1 and the other LOX into the engine’s combustion chamber.
The turbopump was mounted to the engine, allowing it to swivel up to 7 degrees to provide pitch and yaw control during its burn. Roll control was provided by a swiveling turbopump exhaust nozzle mounted to the side of the tail section. Early development missiles dispensed with this roll control in favor of a fixed exhaust
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Jupiter Nose Cone
Jupiter’s tail section used a corrugated thin shell monocoque aluminum stringer skin attached to ring stiffeners. The corrugated design, by Willy Mrazek’s Structures and Mechanics Laboratory, provided a high strength to weight ratio. Early development missiles used a simplier structure with external stiffeners.
The load-bearing tail section extended aft to hide most of the engine’s nozzle. This design allowed the missile to stand on a simple ring-shaped launch platform, allowing for both road mobile and naval deployments.
The base of the missile had a circular cutout through which the engine nozzle extended. A flexible “flame curtain” was used to block the opening, allowing the engine to gimbal. Early development missiles had a square cutout.
Total flight time for a maximum range Jupiter flight was 1,016.9 seconds. The missile, weighing 49.37 tonnes (108,840 pounds) at liftoff would rise and quickly pitch toward its target.
During its 157.8 seconds of main propulsion, it would experience a maximum of 13.69 G’s acceleration as it burned most of its 44.39 tonnes (97,854 pounds) propellant load. Main engine cutoff would occur 134.5 km (72.6 nautical miles) downrange at an altitude of 123 km (66.4 nautical miles) at 4,563.5 meters per second (14,968.3 feet per second) velocity.
Four seconds after main engine cutoff, the thrust unit and the body unit would separate. Two seconds later the vernier engine would ignite. The vernier phase would nominally last for 12 to 14 seconds, with cutoff determined by the missile’s guidance system.
The body unit would then coast while the aft unit attitude control system positioned the nose cone for reentry. Spin motors would fire and, 339.3 seconds after liftoff, the spin-stabilized nose cone would separate from the identically spinning aft unit.
550 seconds after liftoff, the nose cone would reach its peak 660 km (356.4 nautical mile) altitude, 1,414.5 km (763.8 nautical miles) downrange from its launch site. About 400.5 seconds later, reentry would begin as the nose cone slammed into the atmosphere at 4,660 meters per second (15,284.7 feet per second).
Only 66.4 seconds after beginning reentry, the nose cone, having endured massive 44 G deceleration to slow to less than 166 meters per second (544.5 feet per second), would reach its target some 2,844 km (1,535 nautical miles) from its launch site.
Author:
by Ed Kyle, Updated 6/29/2011
