Juno I

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Juno I

Juno I satellite launch vehicle. (USAF)
Fact sheet
Function	Orbital launch vehicle
Manufacturer	Army Ballistic Missile Agency
Country of origin	USA
Size
Height	21.2 m
Diameter	1.78 m
Mass	29,060 kg
Stages	4
	Capacity
Payload to LEO	11 kg
Launch History
Status	Retired
Launch Sites	LC-5 and 26A, Cape Canaveral
Total launches	6
Successes	3
Failures	3
Maiden flight	February 1, 1958
Last flight	October 23, 1958
First Stage - Redstone (stretched)
Engines	1 A-7
Thrust	42,439 kgf
Specific Impulse	235 sec
Burn time	155 seconds
Fuel	LOX/Hydyne
Second Stage - Sergeant cluster
Engines	11 Solid
Thrust	7,480 kgf
Specific Impulse	214 sec
Burn time	6 seconds
Fuel	Solid
Third Stage - Sergeant cluster
Engines	3 Solid
Thrust	2,040 kgf
Specific Impulse	214 sec
Burn time	6 seconds
Fuel	Solid
Fourth Stage - Sergeant
Engines	1 Solid
Thrust	680 kgf
Specific Impulse	214 sec
Burn time	6 seconds
Fuel	Solid

The Juno I was a satellite launch vehicle, derived from, and commonly confused with, the Jupiter-C sounding rocket. It is most well known for launching America's first satellite, Explorer I.

It consists of a Jupiter-C rocket, with a fourth stage mounted on top of the "tub" of the third stage. The fourth stage was fired after the third stage burnout to boost the satellite to an orbital velocity of 18,000 mph (8 km/s). The fourth stage would also enter orbit itself.

The Juno I 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. The name derived from von Braun wishing to make the rocket appear as peaceable as the Vanguard rocket, which was not a weapon, as the original Jupiter was, but was developed from a weather study rocket, the Viking.

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.

• 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 s (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 s (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 s (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 s (2.30 kN·s/kg)
    • propellant, same as for Stage 2

[edit] Launch History

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.