LJ-5A Still Premature

"The purpose of the Little Joe 5A," began the technical information summary document issued for this flight on March 6, 1961, "is to qualify the Mercury capsule, escape system, and other systems which must function during and after escape at the combination of dynamic pressure, mach number, and flight path angle that represent the most severe conditions that can be anticipated during an orbital launch on an Atlas booster." Using McDonnell's capsule No. 14, the Little Joe flight test engineers at Wallops Island were behind schedule and eager to improve on the Little Joe 5 test, which had failed on Election Day in 1960. The premature ignition of the escape rocket motor, followed by the failure of the capsule to separate from the booster, still remained unexplained. It had made the prevention of such a recurrence one of the unstated first-order test objectives of LJ-5A. Using another of the beryllium heat-sink heatshields, two Castor and four Recruit rocket motors in the booster, a special backup retrorocket system, and much better instrumentation, William Bland and his crew from STG, together with John C. Palmer, the Wallops Island range director, also hoped to get better data on the capsule's structural integrity and on its sequential, landing, and recovery systems.69 The close simulation that Little Joe 5A should have with the Mercury-Atlas configuration was shown by the following table: [327]70
LJ-5A Mercury-Atlas
Time (sec.) 34.4 60
Max. q (p.s.f.) 972 973
Mach number 1.52 1.58
Flight path angle (deg) 48.6 56.4
Altitude (ft) 30,960 34,300
On Saturday, March 18, 1961, after a four-hour delay caused by checkout problems, Little Joe 5A roared and soared up from the beach at Wallops Island at 11 minutes before noon. The takeoff looked good, but 20 seconds later and 14 seconds too early the capsule escape rocket again fired without the capsule. Warren North described this flight graphically:
At 35 seconds the normal abort signal released the capsule clamp ring. A single retrorocket, which was installed as an emergency separation device, received a premature firing signal at 43 seconds. The dynamic pressure at this point was 400 psf - ten times as great as dynamic pressure at apogee where emergency capsule separation should have taken place. The capsule tumbled immediately upon separating and narrowly missed the booster as it decelerated. The retropack and escape tower were inadvertently jettisoned or torn off as the capsule tumbled. Apparently the centrifugal force and/or the escape tower removed the antenna canister, deploying both the main and reserve parachutes. The capsule descended on both parachutes which were only slightly damaged during high q deployment.71
Postflight analyses showed that both LJ-5 and LJ-5A had failed primarily because of structural deformations near the clamp rings that fouled the electromechanical separation systems.

The impact bag on Little Joe 5A was deployed by its barostat at 10,000 feet. The capsule drifted 10 miles on both its parachutes and finally splashed down 18 miles from the launch site, almost twice as far as planned. On top of that, the parachutes fell unreleased over the capsule as it floated in the water, thereby preventing helicopters from recovering it; a Navy salvage ship made the pickup an hour later. The capsule was in fairly good condition, with only one shingle damaged from its ordeal, and parachute loads six times higher than expected had caused no significant damage to its structure.

Spectacular but disappointing had been this test. The primary objective of qualifying a Mercury capsule during a maximum-q abort had to be rescheduled four weeks later, utilizing the last Little Joe booster. Capsule No. 14 was cleaned up,repaired where necessary, and furnished with another set of sensors, instrumentation, and telemetry for the reflight coming up, the seventh in the Little Joe series and for that reason called prematurely "LJ-7." The postlaunch report for LJ-5A summarized the reason for renaming the last Little Joe flight LJ-5B:

Analysis of data show that the escape-rocket motor fired prematurely and prior to capsule release, thus precluding accomplishment of most of the first-order test objectives. The premature ignition was apparently caused [328] by unscheduled closure of at least two of the capsule main clamp ring limit switches.

Operation of a capsule backup system by ground command separated the capsule from the booster and released the tower, making it possible for the parachutes to deploy. The main and reserve parachutes were deployed simultaneously under very severe flight conditions and enabled the capsule to make a safe landing. However, in spite of the descent rate of 60 percent less than normal, the heat shield caused some damage upon recontact. Examination of the recovered capsule showed that it did not sustain any structural damage sufficient to preclude its rapid refurbishment for another flight test.72

There was no time for more contingency planning if the United States hoped to orbit a man before the end of 1961. But for the moment the question in STG was not what could be done in nine months but what might be done in nine weeks.

69 "Technical Information Summary of Little Joe 5-A (Capsule No. 14)," STG, March 6, 1961, 1-3; "Recovery Operations Requirement for Little Joe Test No. 5-A," undated; and Low comments. See pp. 291-293.

70 Table adapted from memo, Low to Administrator, "Little Joe 5A Test," March 16, 1961. See also "Mission Directive for Little Joe No. 5A," NASA Project Mercury working paper No. 177, March 7, 1961, 3-1.

71 Memo, North to Administrator, "Preliminary Flight Results, Little Joe 5-A," March 20, 1961. See also memo, Low to Dir., Space Flight Programs, "Little Joe 5-B Preparation Schedule," March 24, 1961. The fact that both primary and secondary main parachutes deployed immediately after the escape tower jettisoned complicated "quick-look" observations: see transcript, "Press Conference, Little Joe VI [LJ-5A], March 18, 1961," with Robert L. Krieger and William M. Bland, Jr., at Wallops Island.

72 Norman F. Smith and Chauvin, "Postlaunch Report for Mercury Little Joe No. 5A (LJ-5A)," STG, April 11, 1961, 1. Lewis Fisher, in comments, Sept. 15, 1965, has said that "Little Joe 5A was anything but unedifying . . . . This type of failure may have easily occurred on a Mercury-Atlas flight with very severe program impact had not the Little Joe 5 series pinpointed and fixed a marginal design condition."

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