Jupiter-C (rocket)

The Jupiter-C Intermediate Range Ballistic Missile (IRBM) was designed by the Army Ballistic Missile Agency (ABMA).

The vehicle consists of a modified Redstone ballistic missile with three solid-propellant upper stages. The tankage of the Redstone was lengthened by 8 ft (2.4 m) to provide additional propellant. The instrument compartment is also smaller and lighter than the Redstone's. The second and third stages are clustered in a "tub" atop the vehicle, while the fourth stage is atop the tub itself. The second stage is an outer ring of eleven scaled-down Sergeant rocket engines; the third stage is a cluster of three scaled-down Sergeant rockets grouped within. These are held in position by bulkheads and rings and are surrounded by a cylindrical outer shell. The webbed base plate of the shell rests on a ball-bearing shaft mounted on the first-stage instrument section. Two electric motors spin in the tub at a rate varying from 450 to 750 rpm to compensate for thrust imbalance when the clustered motors fire. The rate of spin is varied by a programmer so that it does not couple with the changing resonant frequency of the first stage during flight.

The upper-stage tub was spun-up before launch. During first-stage flight, the vehicle was guided by a gyro-controleld autopilot controlling both air-vanes and jet vanes on the first stage by means of servos. Following a vertical launch from a simple steel table, the vehicle was programmed so that it was travelling at an angle of 40 degrees from the horizontal at burnout of the first stage, which occurred 157 seconds after launch. At first-stage burnout, explosive bolts fired and springs separated the instrument section from the first-stage tankage. The instrument section and the spinning tub were slowly tipped to a horizontal position by means of four air jets located at the base of the instrument section. When the apex of the vertical flight occurred after a coasting flight of about 247 seconds, a radio signal from the ground ignited the eleven-rocket cluster of the second stage, separating the tub from the instrument section. The third and fourth stages were fired in turn to boost the satellite and fourth stage to an orbital velocity of 18,000 mph (8 km/s).

This method of orbiting a payload obviated the need for a guidance system in the upper stages, and was invented by Wernher von Braun in 1956 for his proposed Project Orbiter, which would have been just like the Jupiter-C but using the even smaller solid-fuel upper stages which were the only ones available at that time. His method was the simplest and most immediate method for putting a payload into orbit, but as it had no upper-stage guidance, it was not put into a precisely specified orbit. When used as a satellite launch vehicle, von Braun referred to the Jupiter-C as the Juno or Juno-I, to make it appear as peaceable as the Vanguard rocket, which was not a missile, that is, a weapon of war, but was developed from a weather study rocket. Sometimes the Jupiter-C is still so referred.

Americans cheered on the orbiting of these early Explorer satellites, not realizing that it was by a means inferior to that of the Russians - or of the U.S. Navy's Project Vanguard. Von Braun had the method used again in the Juno II, which used a real Jupiter first stage rather than a Redstone. No other nation has since used this method.

The Jupiter-C was used as a testbed for testing re-entry nosecones that were later to be deployed on the more advanced Jupiter IRBM mobile missile. Calling a Redstone-based rocket a Jupiter to show that something was getting done for the money paid for the Jupiter project is typical of the changes-of-name that take place in military industries.

General characteristics

• Weight as configured for Explorer 1 launch, loaded/empty
  • Overall, takeoff: 64,000 lb (29,000 kg)/10,260 lb (4650 kg)
  • Stage 1 62,700 lb (28,400 kg)/9,600 lb (4,400 kg)
  • Stage 2 1,020 lb (460 kg)/490 lb (220 kg)
  • Stage 3 280 lb (130 kg)/140 lb (64 kg)
  • Stage 4 80 lb (36 kg)/31.5 lb (14 kg)
• Propulsion
  • Stage 1: Rocketdyne A-7 engine
    • Thrust, 83,000 lbf (370 kN)
    • burning time, 155 s
    • specific impulse, 235 lbf·s/lb (2.30 kN·s/kg)
    • propellants, liquid oxygen, as oxidizer, and "Hydyne" (60% unsymmetrical, dimethylhydrazine and 40% diethylenetriamine), as fuel
    • propellant feed, turbopump type
    • turbopump drive, 90% hydrogen peroxide decomposed by catalyst bed to produce steam
  • Stage 2: Eleven JPL scaled-down Sergeant rockets
    • Thrust, 16,500 lbf (73 kN)
    • burning time, 6.5 s
    • specific impulse, 220 lbf·s/lb (2.16 kN·s/kg)
    • propellant, polysulfide-aluminum and ammonium perchlorate (solid propellant)
  • Stage 3: Three JPL scaled-down Sergeant rockets
    • Thrust, 5,400 lbf (24 kN)
    • burning time, 6.5 s
    • specific impulse, 235 lbf·s/lb (2.30 kN·s/kg)
    • propellant, same as for Stage 2
  • Stage 4: One JPL scaled-down Sergeant rocket
    • Thrust, 1,500 lbf (8 kN)
    • burning time, 6.5 s
    • specific impulse, 235 lbf·s/lb (2.30 kN·s/kg)
    • propellant, same as for Stage 2

The Redstone, Jupiter-C and Mercury-Redstone launch vehicles compared

Flight history

September 20, 1956: Lifted an 86.5-lb (39.2 kg) payload (including a 30-lb (14 kg) dummy satellite) to an altitude of 680 mi (1,100 km), a speed of 16,000 mph (7 km/s), and a range of 3,300 mi (5,300 km) from Cape Canaveral, Florida.

May 15, 1957: Lifted an 300 lb (140 kg) scale Jupiter ablative nose cone to an altitude of 350 mi (560 km) and a range of 710 mi (1,100 km).

August 8, 1957: Lifted a 1/3-scale Jupiter nose cone to an altitude of 285 mi (460 km) and a range of 1,330 mi (2,140 km). Juno-I (four-stage configuration).

January 31, 1958: Orbited Explorer I satellite weighing 30.66 lb (13.91 kg) with 18.35 lb (8.32 kg) of payload, perigee 224 mi (360 km), apogee 1,575 mi (2,535 km). Explorer I ceased transmission of data on May 23, 1958, when its batteries died, but remained in orbit for more than 12 years. It made a fiery reentry over the Pacific Ocean on March 31, 1970.

March 5, 1958: Attempted orbit of Explorer II weighing 31.36 lb (14.22 kg) with 18.83 lb (8.54 kg) of payload failed because fourth stage did not ignite.

March 26, 1958: Orbited Explorer III satellite weighing 31.0 lb (14.0 kg) with 18.53 lb (8.41 kg) of payload, perigee 119 mi (192 km), apogee 1,740 mi (2,800 km). Down June 28, 1958.

July 26, 1958: Orbited Explorer IV satellite weighing 37.16 lb (16.86 kg) with 25.76 lb (11.68 kg) of payload, perigee 163 mi, apogee 1,373 mi (2,210 km). Down October 23, 1959.

August 24, 1958: Attempted orbit of Explorer V satellite 37.16 lb (16.86 kg) with 25.76 lb (11.68 kg) of payload. It failed because booster collided with second stage after separation, causing upper stage firing angle to be off.

October 23, 1958: Attempted orbit of 12 ft (3.7 m) inflatable Beacon satellite 31.5 lb (14.3 kg) with 18.3 lb (8.3 kg) of payload. It failed when second stage separated prematurely from booster.

Source: Data Sheet, Department of Astronautics, National Air and Space Museum, Smithsonian Institution.nl:Jupiter-C pl:Jupiter C