No one was injured, but when the smoke cleared it was evident that only the capsule-and-tower combination had been launched, on a trajectory similar to an off-the-pad abort. The booster and adapter-clamp ring remained intact on the launcher. Near apogee, at about 2000 feet, the clamping ring that held tower to capsule released and the little pyro-rocket for jettisoning the tower fired.84
The accident report on LJ-1, issued on September 18, blamed the premature firing of the Grand Central escape rocket on an electrical leak, or what missile engineers were calling "transients," "ghost" voltages or currents, or simply a "glitch" in a relay circuit. The fault was found in a coil. It had been specially designed as a positive redundancy to protect biological specimens from too rapid an abort and as a negative redundancy to prevent inadvertent destruction of the test booster. Again the problem of upgrading the machines to provide safety for animal payloads as well as to ensure mission success had created unexpected problems. This first trial of the brand-new Little Joe test booster apparently had been too ambitious. Fortunately the momentum of the Little Joe test series was not disturbed by the debacle of the boilerplate payload on Little Joe No. 1.
 North American Aviation finished and shipped on September 25, 1959, its sixth and last airframe for the Little Joe booster as promised. The Space Task Group therefore had available at the beginning of October all the Little Joe test boosters it had ordered. Designed primarily to man-rate the escape system operating from a Mercury-Atlas already in flight, the Little Joe booster also was committed to perform some biological research before fulfilling its primary mission.85
More by coincidence than by design, the next three Little Joe boosters were launched from Wallops Island exactly one month apart in the autumn of 1959. Still the primary aerodynamic test objectives remained unfulfilled. But the fourth shot, in January 1960, finally worked precisely as planned. STG was satisfied that its own pilot safety provisions were viable under the worst possible aerodynamic conditions. The same kind of test on McDonnell's finished product, rather than on boilerplate demonstration capsules, perhaps could be made the following summer.
On October 4, 1959, the same booster that had been jilted by the capsule and escape rocket in August was finally fired, this time with a double dummy - an uninstrumented boilerplate model fitted with an inert escape rocket system. After the fiasco of LJ- 1, the more modest purpose of this test, which later became known as Little Joe 6 (LJ-6), was to prove the "reliability" of the whole booster propulsion cluster. All four Pollux motors, plus four smaller Recruit motors, were set to fire in sequence. Little Joe 6, 55 feet tall and weighing 20 tons at liftoff, blasted up to a peak altitude barely short of 40 miles; then it was intentionally destroyed after two and a half minutes of flight to prove the destruct system. Impact was over 70 miles from Wallops Island. All went well.86
Satisfied that Little Joe had proved itself as a booster, the supervisory team of NASA engineers, consisting of John C. Palmer from Wallops, and Roland English, James Mayo, Clifford Nelson, Charles McFall of Langley, and William M. Bland and Robert O. Piland of the Space Task Group, prepared for a new effort to check the correct operation of the abort escape system at maximum loading conditions. The region called "max q" (for maximum dynamic pressure) by aerodynamicists is the portion of the flight path at which relative speed between the vehicle and the atmosphere produces the greatest air resistance on the vehicle. Many variables were involved, but roughly both Little Joe and the Mercury-Atlas were expected to experience dynamic pressures of almost 1,000 pounds per square foot at an approximate altitude of six miles after about one minute of flight time.
For the second attempt at this primary mission, Little Joe 1-A (LJ-1A) needed to propel another dummy capsule and pylon to the max q region. Both drogue and main parachute behavior were to be carefully studied on this flight. Surprised by the insistent demands from the news media to witness these developmental flight tests, STG gave the press a careful enumeration of situations that might call for a "hold" or a "scratch" of the shot.87
On November 4, 1959, when the second Little Joe booster was successfully launched, newspapermen could see nothing wrong. The flight looked straight and  true until the rocket was out of sight. But the test engineers in the control center observed that the escape motor did not fire until 10 seconds after the point of maximum dynamic pressure. The parachutes and recovery operations performed well enough to fulfill secondary and tertiary objectives, but precisely why escape was too slow was never fully understood. Later analysis showed only that the delayed ignition of the escape rocket caused the separation of capsule from booster at a pressure only one-tenth of that programmed.88 Because the next scheduled launch of a Little Joe booster was already committed to a test for certain aeromedical objectives and was now in a late stage of preparation, the primary aerodynamic test of the escape system was postponed until January, when a third try, to be called Little Joe 1-B, could be made.
Back in May, STG had begun planning with the Air Force School of Aviation Medicine to include some biological packages in later Little Joe flights. The booster designated No. 5 was reserved specifically to qualify all systems in the McDonnell capsule, carrying a chimpanzee occupant and escaping from a simulated Atlas explosion at the point of max q.89
After the disappointment of Little Joe 1-A, Donlan, Bland, and Piland decided to pull out the stops on Little Joe 2 and allow the aeromedical specialists to run all the experiments they wanted on a high-powered flight. The School of Aviation Medicine had made ready a biological package for its primate passenger, a small rhesus monkey named "Sam," after his alma mater. In addition to Sam's special capsule for rocket flight, the military physicians now prepared barley seeds, rat nerve cells, neurospora, tissue cultures, and insect packets to measure the effects of primary radiation, changes in appearance and capacity for reproduction, and ova and larvae responses to the space environment.
Little Joe 2 promised to be a spectacular flight if everything went as planned. The engineers could see how the capsule escape system would function under conditions of high mach number and low dynamic pressure; more important technically, they could measure the motions, aerodynamic loads, and aerodynamic heating experience of the capsule entering from the intermediate height of about 70 miles. The Air Force medical specialists might also learn about other things, but their chief interest was to see how well Sam himself would withstand weightlessness during the trip. This was also the chief interest of Alan B. Shepard and Virgil I. Grissom, who came to see this launch.90
On December 4, 1959, just before noon, the third Little Joe, LJ-2, ripped through the air under full power and burned out at an altitude of 100,000 feet. The tower and capsule separated as planned and the escape rocket gave an additional boost, throwing the capsule into a coasting trajectory that reached its zenith just short of 280,000 feet, or 53 miles. This peak height was about 100,000 feet lower than expected because of a serious windage error, so Sam experienced only three minutes of weightlessness instead of four. He survived the mild reentry, the not-so-mild impact, and six hours of confinement before he was recovered by a destroyer and liberated from his inner envelope.91
 All preliminary indications reflected a highly successful flight. For the first time Little Joe had achieved full success on all three orders of its programmed test objectives. Congratulatory letters sped around the circuit among those responsible. It was a satisfying way to close out the year. But STG engineers knew that this full-performance test of the Little Joe was not the most crucial case for man-rating the Mercury escape system. They still had to prove that at max q, where everything conspired to produce failure, the escape system could be relied upon to save the life of any man who ventured into this region aboard an Atlas.
Later evaluations of Little Joe 2 were somewhat less sanguine. Biologists were disappointed: although results were better than on any previous biological space flight, they were still not good enough. STG engineers still awaited the more crucial test of the escape system under maximum aerodynamic stress. And the Mercury managers were disappointed at the way the news media had dramatized the animal experiments at the expense of the equally significant demonstration of technological progress.92
Public information officers John A. Powers of STG and E. Harry Kolcum of NASA Headquarters tried to correct the "misplaced emphasis" in the news stories before the fourth Little Joe shot, Little Joe 1-B, occurred in January. By this time, Gilruth wished the press would note "the relatively minor role of this particular task in the context of the total Mercury program."93 But again, to the reporters the star of the event was "Miss Sam," the female counterpart to the occupant of LJ-2, whose life was at stake and whose nervous system was to be tested in psychomotor performance tasks during the short but severe flight. Some of the newsmen perhaps knew or divined that several of the astronauts wanted to ride one of the next Little Joes into space.
Finally, on January 21, 1960, with the fourth launching of the Little Joe series, the escape system performed as planned at the point of max q.94 Propelled by two Pollux main motors, Little Joe 1-B blasted up to the nominal altitude of slightly less than nine miles and attained a maximum velocity slightly over 2,000 miles per hour. Then the escape rocket kicked on the overdrive for an additional 250 feet in one second to "rescue" the Mercury replica from a simulated booster failure at that point. Over a range of 11.5 miles out to sea, Miss Sam, in her biopack prepared by medical technicians from Brooks Air Force Base and its School of Aviation Medicine, not only survived these severe g loads but also performed well (except for a 30-second lapse) at her business of watching for the light and pulling the lever. After 8.5 minutes of flight, during which the sequence system and capsule landing systems worked perfectly, Miss Sam touched down. She was recovered almost immediately by a Marine helicopter, and was returned in excellent condition to Wallops Station within 45 minutes after liftoff.95
For half a minute after the escape rocket fired, the little rhesus monkey had been badly shaken up and did not respond to stimuli, but otherwise Miss Sam acted the role of the perfectly trained primate automaton throughout the flight.  Evidence of nystagmus after escape rocket firing and after impact on the water did cause concern, for it suggested that an astronaut's effectiveness as a backup to the parachute system might be impaired. The internal noise level proved to be higher than expected, likewise causing some other worries over the provisions for communications and pilot comfort.96
To this point, 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.97 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.
84 Abraham D. Spinak et al., "Special Accident Investigating Committee Report of the Little Joe No. One Misfire on Aug. 21, 1959, Wallops Station," Sept. 18, 1959, 6.
85 Memo, W. S. Blanchard, Jr., to Assoc. Dir., "Tentative Changes in the Langley Little Joe Support Program," Sept. 3, 1959; "Little Joe Project Progress Report," North American Aviation, Sept. 31, 1959, 6; letter, Gerathewohl to Jerome Hammack, Dec. 30, 1959; letter, Donlan to Gerathewohl, Jan. 22, 1960.
86 Memo, Low to Administrator, "First Little Joe Launching," Oct. 5, 1959. Cf. memo, Low to Administrator, "Follow-up Report, Little Joe Firing of 11/4/59," Nov. 6, 1959. See "Flight Test Report LJ-6," NASA Project Mercury working paper No. 133, April 22, 1960. See also memo, John F. Royall, Jr., to STG Assoc. Dir., "Preliminary Data from the Flight Test . . . of Little Joe No. 6, Nov. 4, 1959."
87 "Countdown for the Little Joe 1-A," STG, Nov. 4, 1959. Cf. memo, Silverstein to Dir., Office of Public Information, "Project Mercury Information Plan," July 7, 1959.
88 Letter, Donlan to Cdr., DesFlotFour, Dec. 29, 1959; "Research and Development Flight Test Program . . . Abort at High Dynamic Pressure, LJ-1A," NASA Project Mercury working paper No. 134, July 25, 1960. George Low has commented (Oct. 5, 1965) that this hangfire on LJ-1A "probably in itself made the entire Little Joe program worthwhile. Early identification of this problem certainly saved us time and avoided many headaches later."
89 "Minutes of Meeting, Bio-Paks for Little Joe Flights 2, 3, and 4, June 8, 1959, at STG," June 18, 1959. Cf. memo, Jack C. Heberlig to Gilruth, "Visit of [School of Aviation Medicine personnel, 25 men] to Discuss Bio-Paks [for Little Joe 2, 3, and 4]," April 1, 1959. Ronald Kolenkiewicz, "Minutes of Meeting Concerning Mercury Qualification Test for Little Joe No. 5, June 30, 1959, at NASA-STG, Langley Field, Va.," July 16, 1959. The preliminary operations plan for the aeromedical aspects of LJ-5 was drawn up by Richard S. Johnston on Nov. 26, 1959.
90 The possibility of flying a manned Little Joe was seriously if secretly considered during this time, but the idea was quickly discarded as technically not feasible because the dynamic pressures were too great: Walter C. Williams, interview, Houston, Aug. 23, 1965.
91 "Little Joe II," operations plan, STG, Dec. 2, 1959; memo, Low to Administrator, "Little Joe Test No. 3," Dec. 5, 1959. Cf. "Flight Test Report, LJ-2," NASA Project Mercury working paper No. 169, April 1961. "Recovery Operations for Little Joe Test No. Two," NASA Project Mercury working paper No. 122, Jan. 18, 1960. See also letter, Dryden to Gilruth, Dec. 8, 1959; letter, Otis O. Benson, Jr., to Dryden, Dec. 30, 1959.
92 Memo, George D. Smith to NASA Administrator, "Biological Experiment on Little Joe No. 2," Dec. 31, 1959. Cf. letter, Reid to STG, "In support of Project Mercury - Transmittal of Preliminary Data . . . of Little Joe 2," Dec. 31, 1959; John A. Powers and E. Harry Kolcum, "Information Plan - Little Joe Flight 1-B," Jan. 5, 1960, 2.
93 Gilruth, "Addendum to Information Plan for Firing of Little Joe 1-B," Jan. 5, 1960, 2.
94 Memo, Low to NASA Administrator, "Little Joe 1-B (Test No. 4)," Jan. 22, 1960. Cf. "Flight Test Report, LJ-1B," NASA Project Mercury working paper No. 173, March 3, 1961. "Recovery Operations for LJ Test No. One-B," NASA Project Mercury working paper No. 105, Feb. 1960.
95 Memo, Heberlig to Chief, Flight Systems Div., "Preliminary Reports of the SAM Bio-Pak Experiment in Little Joe 1-B," Feb. 3, 1960. See also letter, Gilruth to Cloid D. Green, School of Aviation Medicine, Brooks AFB, re LJ-1B biophysical aspects, April 27, 1960.
96 Memo, Harvey H. Hubbard to Assoc. Dir., STG, "Noise Measurements of Big Joe and Little Joe Mercury Vehicles," Feb. 17, 1960. Cf. letter, Donlan to McDonnell Aircraft Corp., re preliminary results of LJ-1B and LJ-2 compiled for use in production redesign, May 3, 1960. See also booklet, "Project Mercury Photographs of Press Tour, Little Joe 1-B," Jan. 20-21, 1960.
97 Minutes, Lewis R. Fisher, "Little Joe No. 5," meeting on Jan. 28, 1960.