Jupiter-C IRBM

The vehicle consists of a modified Redstone ballistic missile[?] topped by three solid-propellant upper stages. The tankage of the Redstone was lengthened by eight feet 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 miles per hour.

When used as a satellite launching vehicle, the Jupiter-C is sometimes referred to as the Juno-I.

General Characteristics

• Weight (in pounds, as configured for Explorer 1 launch, loaded/empty)
  • Overall (takeoff): 64,000/10,260
  • Stage 1 62,700/9,600
  • Stage 2 1,020/490
  • Stage 3 280/140
  • Stage 1 80/31.5
• Propulsion
  • Stage 1: Rocketdyne A-7 engine
    • Thrust, 83,000 lb
    • burning time, 155 seconds
    • specific impulse, 235 seconds
    • 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 lb
    • burning time, 6.5 seconds
    • specific impulse, 220 lb-sec/lb
    • propellant, polysulfide-aluminum and ammonium perchlorate (solid propellant)
  • Stage 3: Three JPL scaled-down Sergeant rockets
    • Thrust, 5,400 lb
    • burning time, 6.5 seconds
    • specific impulse, 235 lb-sec/lb
    • propellant, same as for Stage 2
  • Stage 4: One JPL scaled-down Sergeant rocket
    • Thrust, 5,400 lb
    • burning time, 6.5 seconds
    • specific impulse, 235 lb-sec/lb
    • propellant, same as for Stage 2

Flight History

September 20, 1956: Lofted an 86.5 lb payload (including a 30 lb dummy satellite) to an altitude of 680 miles, a speed of 16,000 mph, and a range of 3,300 miles from Cape Canaveral, Florida.

May 15, 1957: Lofted an 300-pound scale Jupiter ablative nose cone to an altitude of 350 miles and a range of 710 miles.

August 8, 1957: Lofted a 1/3-scale Jupiter nose cone to an altitude of 285 miles and a range of 1,330 miles. Juno-I (four-stage configuration).

January 31, 1958: Orbited Explorer I satellite weighing 30.66 pounds with 18.35 pounds of payload, perigee 224 miles, apogee 1,575 miles. 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[?] (31.36 pounds with 18.83 pounds of payload) failed because fourth stage did not ignite.

March 26, 1958: Orbited Explorer III[?] satellite weighing 31.0 pounds with 18.53 pounds of payload, perigee 119 miles, apogee 1,740 miles. Down June 28, 1958.

July 26, 1958: Orbited Explorer IV satellite weighing 37.16 pounds with 25.76 pounds of payload, perigee 163 miles, apogee 1,373 miles. Down October 23, 1959.

August 24, 1958: Attempted orbit of Explorer V[?] satellite (37.16 pounds with 25.76 pounds of payload) failed because booster collided with second stage after separation, causing upper stage firing angle to be off.

October 23, 1958: Attempted orbit of 12-foot inflatable Beacon satellite (31.5 pounds with 18.3 pounds of payload) failed when second stage separated prematurely from booster.

Source: Data Sheet, Department of Astronautics, National Air and Space Museum, Smithsonian Institution.