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Mercury Redstone 2



Mercury Redstone 2 (MR-2) was the third attempted flight of the Mercury/Redstone launch configuration and the first to include a living organism, a 17 kg chimpanzee named Ham (in honor of Holloman Aerospace Medical Center). The objectives of MR-2 were to: (1) obtain physiological and performance data on a primate in ballistic space flight; (2) qualify the Environmental Control System (ECS) and aeromedical instrumentation; (3) qualify the landing bag system; (4) partially qualify the voice communication system; (5) qualify the mechanically actuated side hatch; and, (6) obtain a closed-loop evaluation of the booster automatic abort system.

During the flight, the thrust controller ran above nominal performance, depleting the propellant 0.5 s before deactivation of the abort pressure sensor. The abort system detected the early shutdown and aborted the spacecraft. The higher-than-normal cut-off velocity coupled with the thrust of the escape engine resulted in the capsule landing well beyond the recovery area. The abort properly signalled the requisite Mayday message to the recovery forces, putting them in motion for a computed rendezvous point further downrange.

Because of the overperformance of the launch vehicle and the added velocity of the escape engine, MR-2 achieved a velocity of about 9,400 km/hour (as opposed to the intended 7,000 km/hour) and an altitude of 250 km (rather than 185 km). Ham's trip took 2 minutes and 24 seconds longer than intended (16 minutes and 39 seconds total flight time) and went 670 km downrange (205 km further than planned). His peak g-load during reentry was 14.7, almost 3g more than planned.

Problems also occurred with regard to the cabin pressure when, just prior to the abort, at 2 minutes and 18 seconds into the flight, it dropped from 5.5 psi to 1 psi. The problem was ultimately traced to the air inlet snorkel valve. Vibrations had loosened the pin which held the valve closed, thus allowing the valve to open, an event which was normal only after the main parachute was deployed. Ham did not suffer from this sudden depressurization of the cabin. However, the open valve contributed to problems after splashdown.

Ham's performance during the flight went well, with reaction times for his required tasks of lever pulling comparable to his pre-flight testing despite his vehicle's performance problems.

When MR-2 splashed down no ships had yet reached the vicinity, having landed some 100 km from the nearest recovery ship, the destroyer USS Ellison. A P2V search plane located the capsule about 27 minutes after splashdown. Helicopters were dispatched from the USS Donner as at least two additional hours were still required for the Ellison to arrive. Although when the search plane had located the capsule it was floating upright, by the time the helicopters arrived they found MR-2 on its side and taking on water. It was determined that the beryllium heatshield had skipped on the water on impact, bouncing against the capsule bottom and puncturing two holes in the titanium pressure bulkhead. In addition, the plastic landing bag had worn badly, resulting in the heat shield being torn free. Water entering the cabin became worse when the capsule capsized, allowing more water to enter via the open cabin pressure valve. When the helicopter latched onto the capsule, the pilot estimated an extra load of nearly 800 pounds due to the sea water. Ham was retuened safely to the Donner, apparently no worse for the wear. Sometime later, after his flight, he was shown the spacecraft and it was visually apparent he had no further interest in cooperating with the program.

Alternate Names

  • MR-2

Facts in Brief

Launch Date: 1961-01-31
Launch Vehicle: Redstone
Launch Site: Cape Canaveral, United States

Funding Agency

  • NASA-Office of Manned Space Flight (United States)


  • Engineering
  • Life Science

Additional Information

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


Selected References

Grimwood, J. M., Project Mercury: A chronology, NASA, SP-4001, Wash., D.C., 1963.

Henry, J. P., Ed., and J. D., Ed. Mosely, Results of the project Mercury ballistic and orbital chimpanzee flights, NASA, SP-39, Wash, DC, 1963.

Other Sources of MR-2 Information/Data

MR-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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