Little Joe
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- Little Joe was also a railroad locomotive type
| Little Joe | ||
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| Missing image Little_Joe_I_rocket.jpg Flight of a Little Joe, Mercury capsule LES test rocket. (NASA) | ||
| Stages | 2 | |
| 0 - Booster | Engines | 4 * Recruit rockets |
| Thrust | (167 kN) x 4 = (668 kN) | |
| Burn time | 1.53 seconds | |
| Fuels | Solid | |
| 1 - Sustainer | Engines | 4 * Castor rockets |
| Thrust | (259 kN) x 4 = (1,036 kN) | |
| Burn time | 37 seconds | |
| Fuels | Solid | |
| 4C version | Launch 1959 | |
| Payload | 3,000 lb (1,400 kg) | |
| Contents |
Little Joe Program
When NASA went shopping for a booster to use in the Mercury program they found that the Atlas rockets would cost approximately $2.5 million each and that even the Redstone would cost about $1 million per launching. The managers of the Mercury program recognized from the start that the numerous early test flights would have to be accomplished by a far less expensive booster system. As it turned out, the Little Joe rocket NASA designed, cost about $ 200,000 each.
In January 1958 Max Faget and Paul Purser had worked out in considerable detail on paper how to cluster four of the solid-fuel Sergeant rockets, in standard use at Wallops Island, to boost a manned nose cone above the stratosphere. Faget's short-lived "High Ride" proposal had suffered from comparisons with "Project Adam" at that time, but in August 1958 William Bland and Ronald Kolenkiewicz had returned to their preliminary designs for a cheap cluster of solid rockets to boost full-scale and full-weight model capsules above the atmosphere. As drop tests of boilerplate capsules provided new aerodynamic data on the dynamic stability of the configuration in free-fall, the need for comparable data quickly on the powered phase became apparent. So in October 1958, a NASA team prepared new engineering layouts and estimates for the mechanical design of the booster structure and a suitable launcher.
As the blueprints for this cluster of four rockets began to emerge from their drawing boards, the designers' nickname for their project gradually was adopted. Since their first cross-section drawings showed four holes up, they called the project "Little Joe," from the crap-game throw of a double deuce on the dice. Although four smaller circles were added later to represent the addition of Recruit rocket motors, the original name stuck. The appearance on engineering drawings of the four large stabilizing fins protruding from its airframe also helped to perpetuate the name Little Joe had acquired.
The primary purpose of this relatively small and simple booster system was to save money - by allowing numerous test flights to qualify various solutions to the myriad problems associated with the development of manned space flight, especially the problem of escaping from an explosion midway through takeoff. Capsule aerodynamics under actual reentry conditions was another primary concern. To gain this kind of experience as soon as possible, its designers had to keep the clustered booster simple in concept; it should use solid fuel and existing proven equipment whenever possible, and should be free of any electronic guidance and control systems.
The designers made the Little Joe booster assembly to approximate the same performance that the Army's Redstone booster would have with the capsule payload. But in addition to being flexible enough to perform a variety of missions, Little Joe could be made for about one-fifth the basic cost of the Redstone, would have much lower operating costs, and could be developed and delivered with much less time and effort. And, unlike the larger launch vehicles, Little Joe could be shot from the existing facilities at Wallops Island. It still might even be used to carry a man some day.
Twelve companies responded during November 1958, to the invitations for bids to construct the airframe of Little Joe. The technical evaluation of these proposals was carried on in much the same manner as for the spacecraft, except that Langley Research Center itself carried the bulk of the administrative load. The Missile Division of North American Aviation won the contract on December 29, 1958, and began work immediately at Downey, California, on its order for seven booster airframes and one mobile launcher.
The primary mission objectives for Little Joe as seen in late 1958 (in addition to studying the capsule dynamics at progressively higher altitudes) were to test the capsule escape system at maximum dynamic pressure, to qualify the parachute system, and to verify search and retrieval methods. But since each group of specialists at work on the project sought to acquire firm empirical data as soon as possible, more exact priorities had to be established. The first flights were to secure measurements of inflight and impact forces on the capsule; later flights were to measure critical parameters at the progressively higher altitudes of 20,000, 250,000, and 500,000 feet. The minimum aims of each Little Joe shot could be supplemented from time to time with studies of noise levels, heat and pressure loads, heatshield separation, and the behavior of animal riders, so long as the measurements could be accomplished with minimum telemetry. Since all the capsules boosted by the Little Joe rockets were expected to be recovered, onboard recording techniques would also contribute to the simplicity of the system.
Unique as the only booster system designed specifically and solely for manned capsule qualifications, Little Joe was also one of the pioneer operational launch vehicles using the rocket cluster principle. Since the four modified Sergeants (called either Castor or Pollux rockets, depending upon modification) and four supplemental Recruit rockets were arranged to fire in various sequences, the takeoff thrust varied greatly, but maximum design thrust was almost 230,000 pounds. Theoretically enough to lift a spacecraft of about 4,000 pounds on a ballistic path over 100 miles high, the push of these clustered main engines should simulate the takeoff profile in the environment that the manned Atlas would experience. Furthermore, the additional powerful explosive pull of the tractor-rocket escape system could be demonstrated under the most severe takeoff conditions imaginable. The engineers who mothered Little Joe to maturity knew it was not much to look at, but they fondly hoped that their ungainly rocket would prove the legitimacy of most of the ballistic capsule design concepts, thereby earning its own honor.
Launch Vehicle Development
As of January 21, 1960, the Little Joe series of five actual and attempted flights had expended four of the six test boosters North American had made for NASA and five prototype capsules made in the Langley shops. The primary test objectives for these solid-fuel-boosted models were an integral part of the development flight program conducted within NASA by the Space Task Group, with Langley and Wallops support. Now only two Little Joe boosters remained for the qualification flight tests. North American had manufactured seven Little Joe airframes, but one of these had been retained at the plant in Downey, California, for static loading tests. STG ordered the refurbishment of this seventh airframe so as to have three Little Joe boosters for the qualification flight program. The success of Little Joe 1-B in January 1960 meant that the next flight, the sixth, to be known as LJ-5, would be the first to fly a real Mercury capsule from the McDonnell production line. In passing from development flight tests with boilerplate models to qualification flight tests with the "real McDonnell" capsule, the Space Task Group moved further away from research into development and toward operations.
Specifications
- Little Joe I
- Thrust: 1,044 kN
- Length: 15.2 m
- Diameter: 2.03 m
- Fin Span: 6.5 m
- Weight: 12,700 kg
- Fuel: Solid
- Burn Time: ~40 s
- Recruit rocket (Thiokol XM19)
- Thrust: (167 kN)
- Length: (2.7 m)
- Diameter: (0.23 m)
- Weight: (159 kg)
- Fuel: Solid
- Burn Time: 1.53 s
- Castor rocket (Thiokol XM33)
- Thrust: (259 kN)
- Length: (6.04 m)
- Diameter: (0.79 m)
- Weight: (4,424 kg)
- Fuel: Solid
- Burn Time: 37 s
External Links
NASA - This New Ocean: A History of Project Mercury (http://www.hq.nasa.gov/office/pao/History/SP-4201/toc.htm)
| First Mission: Little Joe 1 | Mercury program | Last Mission: Little Joe 5B |
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