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 Juno I awaiting launch with Explorer I | |
| Function | Orbitallaunch vehicle |
|---|---|
| Manufacturer | Chrysler for theABMA |
| 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 toLEO | |
| Mass | 11 kg (24 lb) |
| Launch history | |
| Status | Retired |
| Launch sites | LC-5 and26A, Cape Canaveral Missile Annex,Florida |
| Total launches | 6 |
| Success(es) | 3 |
| Failure | 3 |
| First flight | 1 February 1958, 03:47:56GMT |
| Last flight | October 23, 1959 |
| First stage –Redstone (stretched) | |
| Powered by | 1Rocketdyne A-7 |
| Maximum thrust | 42,439 kgf (416.18 kN; 93,560 lbf) |
| Specific impulse | 235 s (2.30 km/s) |
| Burn time | 155 seconds |
| Propellant | Hydyne/LOX |
| Second stage –Baby Sergeant cluster | |
| Powered by | 11Solid[1] |
| Maximum thrust | 7,480 kgf (73.4 kN; 16,500 lbf) |
| Specific impulse | 220 s (2.2 km/s) |
| Burn time | 6 seconds |
| Propellant | Polysulfide-aluminum andammonium perchlorate (Solid) |
| Third stage –Baby Sergeant cluster | |
| Powered by | 3Solid |
| Maximum thrust | 2,040 kgf (20.0 kN; 4,500 lbf) |
| Specific impulse | 236 s (2.31 km/s) |
| Burn time | 6 seconds |
| Propellant | Polysulfide-aluminum andammonium perchlorate (Solid) |
| Fourth stage –Baby Sergeant | |
| Powered by | 1Solid |
| Maximum thrust | 680 kgf (6.7 kN; 1,500 lbf) |
| Specific impulse | 249 s (2.44 km/s) |
| Burn time | 6 seconds |
| Propellant | Polysulfide-aluminum andammonium perchlorate (Solid) |
TheJuno I was a four-stage Americanspace launch vehicle, used to launch lightweight payloads intolow Earth orbit. The launch vehicle was used between January 1958 to December 1959. The launch vehicle is a member of theRedstone launch vehicle family, and was derived from theJupiter-Csounding rocket. It is commonly confused with theJuno II launch vehicle, which was derived from thePGM-19 Jupitermedium-range ballistic missile. In 1958, a Juno I launch vehicle was used to launch America's first satellite,Explorer 1.
Developed as a part of theExplorer Project, the original goal for the launch vehicle was to place anartificial satellite intoorbit. Following theSoviet Union's launch ofSputnik 1 on October 4, 1957 (and the resulting "Sputnik crisis") and the failure of theVanguard 1 launch attempt, the program received funding to match the Soviet space achievements. The launch vehicle family name was suggested in November 1957 byJet Propulsion Laboratory (JPL) DirectorDr. William Pickering, who proposed the nameJuno, after the Roman goddess and queen of the gods, as well as for its position as the satellite-launching version of theJupiter-C. The fourth stage for the Juno I launch vehicle was derived following the September 1956 test launch of a Jupiter-C for theArmy Ballistic Missile Agency, which could have been the world's first satellite launch, had a fourth stage been loaded and fueled. A fourth stage would have allowed the nose cone to overshoot the target and enter orbit.[2]
The first launch of a Juno I launch vehicle was in early 1958, with the successful launch ofExplorer 1 satellite on February 1, 1958, at 03:47:56GMT, after the Soviet Union'sSputnik 1 on October 4, 1957.[2] The launch had been scheduled for January 29, 1958, but was scrubbed twice. Explorer 1 was the first U.S. satellite, and it confirmed the existence of theVan Allen radiation belt. Following the first successful launch, five more Juno I launch attempts occurred with two successes and three failures. The final launch attempt was on October 23, 1958, fromCape Canaveral Launch Pad 5, which ended in failure.[3]
The Juno I consisted of aJupiter-C first stage, based on theRedstone missile; with three additionalsolid fuel stages based on theSergeant missile to provide the added impulse to achieve orbit.[4] The fourth stage was mounted on top of the "tub" of the third stage, and fired after third-stage burnout to boost the payload and fourth stage to an orbital velocity of 8 km/s (5.0 mi/s), with an acceleration of 25–51 g. The tub along with the fourth stage were set spinning while the launch vehicle was on the launch pad to provide gyroscopic force in lieu of a guidance system that would have requiredthrust vectoring,vernier thrusters, or areaction control system. The booster guidance package (with the tub attached) separated from the first stage after burnout to provide attitude control until second stage ignition.[2] This multi-stage system, designed byWernher von Braun in 1956 for his proposedProject Orbiter, obviated the need for a guidance system in the upper stages. It was the simplest method for putting a payload into orbit but having no upper-stage guidance, the payload could not achieve a precise orbit. Both the four-stage Juno I and three-stage Jupiter-C launch vehicles were the same height (21.2 m (70 ft)), with the added fourth-stage booster of the Juno I being enclosed inside the nose cone of the third stage.
Juno I was launched six times byABMA in 1958, intending to place satellites inLEO.[4][5]
Following the successful launch ofExplorer 1 on February 1, 1958, the first U.S. satellite, Juno I made five more launches before being retired in favor ofJuno II.[4] Although Juno I's launch of theExplorer 1 satellite was a huge success for the U.S. space program, only two of its remaining five flights were successful,Explorer 3 andExplorer 4,[1] giving the Juno I vehicle a mission total success ratio of 50%.[4] The Juno I vehicle was replaced by theJuno II in 1959.
The designation painted on the sides of the rocket was inherited from Jupiter-C, where the sequence of manufacture of the rockets (which are not necessarily launched in order, and may be uprated as solutions to technical problems are worked out in tests) was considered a military secret. So the designation employed a simple transformation cypher based on the name of the design and test base:Huntsville, Alabama, giving HUNTSVILE, with duplicated letters dropped. This way H was used for 1, U for 2, ..., E for 9 and X for 0. Thus the "UE" painted on the side of the Juno I that launchedExplorer 1 indicates it was S/N 29 (U→2, E→9).[6][7]
The American public was happy and relieved that America had finally managed to launch a satellite after the launch failures in the Vanguard andViking series. With the relative success of the Juno I program, von Braun developed theJuno II, using aPGM-19 Jupiter first stage, rather than a Redstone.
| Flight No. | Date / time (GMT) | Rocket | Launch site | Payload | Payload mass | Outcome | Comments |
|---|---|---|---|---|---|---|---|
| 1 | February 1, 1958 03:47:56 | Juno I RS-29 (UE) | LC-26A | Explorer 1 | 22 kg | Success | Maiden launch of Juno I. First American satellite launched. Explorer 1 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. |
| 2 | March 5, 1958 18:27:57 | Juno I RS-26 (UV) | LC-26A | Explorer 2 | 23 kg | Failure | Fourth stage did not ignite. |
| 3 | March 26, 1958 17:38:03 | Juno I RS-24 (UT) | LC-5 | Explorer 3 | 23 kg | Success | Decay from orbit on June 28, 1958. |
| 4 | July 26, 1958 15:00:57 | Juno I RS-44 (TT) | LC-5 | Explorer 4 | 29 kg | Success | Decay from orbit on October 23, 1959. |
| 5 | August 24, 1958 06:17:22 | Juno I RS-47 (TI) | LC-5 | Explorer 5 | 29 kg | Failure | Booster collided with second stage after separation, causing upper stage firing angle to be off. |
| 6 | October 23, 1958 03:21:04 | Juno I RS-49 (incorrectly labeled HE instead of TE) | LC-5 | Beacon 1 | 23 kg | Failure | Five stage version, Second stage separated prematurely from booster. |
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