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Little Joe 2



Little Joe 2 (LJ-2) was the third successful launch in a series of suborbital flights designed to test various components of the Mercury flight systems. The primary objectives of the Little Joe booster missions were to: (1) study capsule dynamics at progressively higher altitudes; (2) test the capsule escape system at maximum dynamic pressure; (3) qualify the parachute system; and, (4) verify the search and retrieval methods.

Specific goals of the LJ-2 launch were to: (1) carry out a planned escape of the spacecraft from the booster at high altitude just prior to main booster rocket burnout; (2) ascertain spacecraft entry dynamics for an uncontrolled entry; (3) check spacecraft dynamic stability on descent through the atmosphere without a drogue parachute; (4) determine the physiological and psychological effects of acceleration and weighlessness on a small primate; (5) obtain reliability data on the operatoin of the Mercury parachute; (6) obtain more data on Mercury spacecraft floatation characteristics in sea areas typical of those planned for use as a recovery area; and, (7) obtain additional operational experience of spacecraft recovery by a surface vessel.

Along for the ride on the LJ-2 flight was a rhesus monkey named Sam. Sam's name was derived from the initials of the institution that was responsible for designing the various biological packages to be used in the Mercury test flights, the U.S. Air Force School of Aviation Medicine. Also included in the special capsule for Sam's flight were a variety of other biological specimens, among them barley seeds, rat nerve cells, neurospora, tissue cultures, and insect packets, in order to measure the effects of radiation, changes in appearance and capacity for reproduction, and ova and larvae responses to a space environment. Although there was considerable interest in the performance of the capsule and associated systems, a primary focus was to see how well Sam would fare as a result of his trip and exposure to weightlessness. This was also of interest to the two Mercury astronauts who attended the launch, Alan Shepard and Gus Grissom.

Launch of LJ-2 occurred just before noon. The Little Joe booster burned out at an altitude of about 96,000 feet. The abort sequence was initiated by timers after 59 seconds of flight time, putting the capsule into a trajectory that reached an apogee of 53.03 statute miles. This peak height was about 100,000 feet lower than expected due to higher than expected winds. As a result, Sam only experienced 3 minutes and 13 seconds of weightlessness rather than the anticipated 4 minutes. The remaining sequences occurred as planned, with Sam experiencing a mild reentry and a not-so-mild splashdown. The total flight time was 11 minutes and 6 secons with the spacecraft landing 194.40 statute miles downrange. The spacecraft was located about 2 hours following launch, but a total of 6 hours were to pass before its ultimate recovery by a destroyer and Sam's subsequent release from his inner envelope.

Alternate Names

  • LJ-2
  • LittleJoe2
  • Mercury Little Joe 2

Facts in Brief

Launch Date: 1959-12-04
Launch Vehicle: Little Joe
Launch Site: Wallops Island, United States

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • Engineering
  • Life Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. Edwin V. Bell, II



NameRoleOriginal AffiliationE-mail

Other Sources of LJ-2 Information/Data

LJ-2 information (NASA KSC)
MR-1 Press Release images (NASA JSC)

Project Mercury Drawings and Technical Diagrams (NASA History Office)

On-line version of Project Mercury: A Chronology (NASA History Office)

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