Juno I
Juno I satellite launch vehicle carrying Explorer 2. (USAF)
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| Function | Orbital launch vehicle |
|---|---|
| Manufacturer | Chrysler for the ABMA |
| Country of origin | United States |
| Size | |
| Height | 21.2 m (70 ft) |
| Diameter | 1.78 m (5 ft 10 in) |
| Mass | 29,060 kg (64,070 lb) |
| Stages | 4 |
| Capacity | |
| Payload to LEO | 11 kg (24 lb) |
| Launch history | |
| Status | Retired |
| Launch sites | LC-5 and 26A, Cape Canaveral Missile Annex, Florida |
| Total launches | 6 |
| Successes | 3 |
| Failures | 3 |
| First flight | January 31, 1958 (First orbit: Explorer 1 January 31, 1958) |
| Last flight | October 23, 1959 |
| First stage - Redstone (stretched) | |
| Engines | 1x Rocketdyne A-7 |
| Thrust | 42,439 kgf (416.18 kN; 93,560 lbf) |
| Specific impulse | 235 sec |
| Burn time | 155 seconds |
| Fuel | Hydyne/LOX |
| Second stage - MGM-29 Sergeant cluster | |
| Engines | 11 Solid |
| Thrust | 7,480 kgf (73.4 kN; 16,500 lbf) |
| Specific impulse | 214 sec |
| Burn time | 6 seconds |
| Fuel | Solid - polysulfide-aluminum and ammonium perchlorate |
| Third stage - MGM-29 Sergeant cluster | |
| Engines | 3 Solid |
| Thrust | 2,040 kgf (20.0 kN; 4,500 lbf) |
| Specific impulse | 214 sec |
| Burn time | 6 seconds |
| Fuel | Solid - polysulfide-aluminum and ammonium perchlorate |
| Fourth stage - MGM-29 Sergeant | |
| Engines | 1 Solid |
| Thrust | 680 kgf (6.7 kN; 1,500 lbf) |
| Specific impulse | 214 sec |
| Burn time | 6 seconds |
| Fuel | Solid - polysulfide-aluminum and ammonium perchlorate |
The Juno I was a four-stage American booster rocket which launched America's first satellite, Explorer 1, in 1958. A member of the Redstone rocket family, it was derived from the Jupiter-C sounding rocket. It is commonly confused with the Juno II launch vehicle, which was derived from the PGM-19 Jupiter medium-range ballistic missile.
The Juno I consisted of a Jupiter-C rocket, with a fourth stage mounted on top of the "tub" of the third stage, which was fired after third stage burnout to boost the payload and fourth stage to an orbital velocity of 8 kilometres per second (29,000 km/h; 18,000 mph). The tub along with the fourth stage were set spinning while the rocket was on the launch pad to provide gyroscopic force in place of a guidance system that would have required vanes, gimbals, or vernier motors. This multi-stage system, designed by Wernher von Braun in 1956 for his proposed Project Orbiter, obviated the need for a guidance system in the upper stages, proving to be the simplest and most immediate method for putting a payload into orbit; but as it had no upper-stage guidance, it could not inject the payload into a precise orbit. Both the four-stage Juno I and three-stage Jupiter-C launch vehicles were the same height (21.2 meters), with the added fourth-stage booster of the Juno I being enclosed inside the nose cone of the third stage.
The rocket family is named for the Roman goddess and queen of the gods Juno for its position as the satellite-launching version of the Jupiter-C. The name was proposed by JPL Director Dr. William Pickering in November 1957. The September 1956 test launch of a Jupiter-C for the Army Ballistic Missile Agency could have been the world's first satellite launch. Had the fourth stage been loaded and fueled, the nose cone would have overshot the target and entered orbit. Such a launch did not occur until early 1958 when a Juno 1 successfully launched the first United States satellite, Explorer 1, as part of Project Vanguard, after the Soviet Union's Sputnik 1 in October 1957.
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