Little Joe (rocket)

• 1. A Roll of the Dice

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  Little Joe, a solid-fueled booster rocket built for NASA's Project Mercury, took its name from a throw of the dice. The name is attributed to Maxime Faget of NASA's Langley Research Center in Hampton, Virginia. He looked at the rocket's four large fins and thought of a slang term from craps for a roll of four. The designers' first cross-section drawings also showed four holes, which suggested a double deuce. The name was also given to the whole test program built around the booster. NASA launched Little Joe eight times between 1959 and 1961, all from Wallops Island, Virginia. Its job was to test the launch escape system and the heat shield for Mercury capsules. Why did NASA want a rocket that was simple and modest by design? How was it put together? And what happened when the tests went wrong?

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• 2. Cheaper Than Redstone

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  Atlas rockets, NASA found, would cost approximately 2.5 million US dollars each. Even the Redstone would cost about 1 million dollars per launch. Mercury's managers recognized that the many early test flights would have to use a far cheaper booster. NASA therefore designed Little Joe, which cost 200,000 dollars each. The designers kept the concept plain. It would burn solid fuel and use proven equipment wherever possible. It would carry no electronic guidance and control systems. Engineers shaped the booster to approximate the performance the Army's Redstone would have given the capsule payload. Yet Little Joe could be built for about one-fifth the basic cost of the Redstone. Its operating costs would be much lower, and it needed less time and effort to develop and deliver. Another advantage was location, because unlike the larger launch vehicles it could be fired from existing facilities at Wallops Island. The design effort behind that low price had begun on paper in January 1958.

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• 3. Sketches to Contract

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  In January 1958, Max Faget and Paul Purser worked out in considerable detail how to cluster four solid-fuel Sergeant rockets. The Sergeant was in standard use at the Wallops Flight Facility in Virginia. The cluster was meant to boost a crewed nose cone above the stratosphere. Faget's short-lived High Ride proposal suffered when it was compared with Project Adam at the time. In August 1958, William Bland and Ronald Kolenkiewicz returned to their preliminary designs for a cheap cluster of solid rockets. They wanted to lift full-scale, full-weight model capsules above the atmosphere. Drop tests of boilerplate capsules were by then producing new aerodynamic data on stability in free-fall. That made the need for matching data on the powered phase quickly obvious. In October 1958, a NASA team prepared new engineering layouts and estimates for the booster structure and a suitable launcher. During November 1958, twelve companies answered the invitations to bid on the airframe. Langley Research Center itself carried most of the administrative load in judging them. The Missile Division of North American Aviation won the contract on the 29th of December 1958. Work began at once in Downey, California. The order was for seven booster airframes and one mobile launcher, a small fleet for so many tests.

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• 4. The Cluster Design

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  Four smaller circles were later added to the original drawings to show the Recruit rocket motors. Four modified Sergeant rockets formed the core, and they were called either Castor or Pollux depending on the modification. Together with four supplemental Recruit rockets, they were arranged to fire in various sequences. Takeoff thrust therefore varied greatly, with a maximum design thrust of almost 230,000 pounds (1,020 kilonewtons). In theory that was enough to lift a spacecraft of about 4,000 pounds (1,800 kg) on a ballistic path more than 100 miles (160 km) high. The push was meant to imitate the takeoff profile that the crewed Atlas would later produce. Little Joe was the first of only two booster systems designed solely for crewed capsule qualification. It was also one of the pioneer operational launch vehicles to use the rocket cluster principle. The Little Joe I stood 15.2 m long and 2.03 m in diameter, with a fin span of 6.5 m. It weighed 28,000 lb (12,700 kg) and burned for roughly 40 seconds. The Thiokol XM33 Castor motor was 6.04 m long and 0.79 m wide. It weighed 9,753 lb (4,424 kg), produced 58,200 lbf (259 kN) of thrust, and burned for 37 seconds. The Thiokol XM19 Recruit was only 2.7 m long and 0.23 m wide. It weighed 350 lb (159 kg), delivered 37,500 lbf (167 kN), and burned for just 1.53 seconds. The engineers knew their ungainly rocket was not much to look at. They hoped it would prove the legitimacy of most ballistic capsule design concepts and earn its own honor.

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• 5. What to Measure

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  The altitudes of 20,000, 250,000, and 500,000 feet (6, 75, and 150 km) set the pace of the test plan. The first flights were to measure forces on the capsule in flight and at impact. Later flights would take critical readings at those progressively higher altitudes. Each group of specialists wanted firm data as early as possible, so the priorities had to be ranked. Escaping from an explosion at or during launch was the problem that worried engineers most. Capsule aerodynamics under real reentry conditions was another central concern. In late 1958, the main objectives also included testing the escape system at maximum dynamic pressure and qualifying the parachute system. A third objective was verifying search and retrieval methods. Extra studies could be added to any shot, covering noise levels, heat and pressure loads, heat shield separation, and the behavior of animal riders. The condition was that they needed only minimal telemetry. Every capsule was expected to be recovered, so onboard recording techniques could keep the whole system simple.

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• 6. Early Setbacks

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  Mercury flights carried a two-letter designation matching the launch vehicle, followed by a dash and a digit for the set of flight objectives. An optional letter marked repeat flights toward the same objectives. The first Little Joe flight was officially LJ-1. The flights did not occur in numeric order, because the schedule was adapted as the project progressed. Little Joe 1 flew on the 21st of August 1959 and lasted 20 seconds. An electrical malfunction ignited the escape tower before launch. The tower took the spacecraft with it and left the rocket on the ground. Little Joe 6 followed on the 4th of October 1959 and ran for 5 minutes 10 seconds. It tested spacecraft aerodynamics and integrity and counted as a partial success. Little Joe 1A flew on the 4th of November 1959 and lasted 8 minutes 11 seconds. It tested the escape system in flight with a boilerplate capsule. The escape tower rocket ignited 10 seconds too late, so the result was again a partial success. Recovery took place 11.5 miles southeast of Wallops Island. The flight after that carried a living passenger.

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• 7. Sam and Miss Sam

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  A rhesus macaque named Sam rode Little Joe 2 on the 4th of December 1959. The flight tested the escape system with a primate at high altitude and lasted 11 minutes 6 seconds. It reached an altitude of 53 miles (85 km) and counted as a success. Recovery came 194 miles southeast of Wallops Island, Virginia. Little Joe 1B flew on the 21st of January 1960 and lasted 8 minutes 35 seconds. It was a maximum-q abort and escape test, again with a primate and a boilerplate capsule. Maximum-q is the point of greatest dynamic pressure during ascent. This time the passenger was a female rhesus monkey named Miss Sam. The flight was another success. Her mission was the last to use a boilerplate model before the program turned to production capsules.

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• 8. Real Capsules

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  By the 21st of January 1960, five actual and attempted flights had used four of the six test boosters North American had made for NASA. They had also used five prototype capsules built in the Langley shops. Only two boosters remained for the qualification flights. North American had built seven airframes in all, but kept one at Downey for static loading tests. The Space Task Group ordered that seventh airframe refurbished, which gave it three boosters. The next flight would be the first to carry a production capsule from the McDonnell line. With it, the group moved further from research and closer to operations. Little Joe 5 flew on the 8th of November 1960 and lasted 2 minutes 22 seconds. Air pressure deflected the clamp holding the spacecraft, and the wiring was incorrect. The escape tower ignited too early and failed to separate the spacecraft from the launch vehicle. The altitude was only 10 miles, and the test was a failure. Little Joe 5A flew on the 18th of March 1961 and lasted 5 minutes 25 seconds. The tower fired 14 seconds too soon and again failed to separate the spacecraft from the rocket. It was a partial success. Little Joe 5B flew on the 28th of April 1961, also for 5 minutes 25 seconds. It was the third escape system test with a production spacecraft, and it succeeded. That flight concluded the Little Joe program. A successor, Little Joe II, would carry flight tests of the Apollo launch escape system from 1963 to 1966.

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