Already the Russians had demonstrated that animals could survive in space. Between 1949 and 1952 they had carried out six experiments with dogs, reaching a maximum altitude of 55 nautical miles. By 1956 another nine flights, to a maximum altitude of 115 nautical miles, had been achieved.

Following Sputnik I, the Soviets had orbited a small dog, Laika, in Sputnik II (which weighed over 1,100 pounds). Laika had been equipped with a comprehensive array of telemetry sensors which gave continuous physiological information to tracking stations. The cabin conditioning system maintained sea-level atmospheric pressure within the cabin, and Laika survived 6 days before depletion of the oxygen stores caused asphyxiation. The Laika flight demonstrated that space flight was tolerable to animals. It indicated, too, that Soviet interests extended to the use of manned satellites. According to Fryer, who has summed up the situation very well indeed:
 

The really major problem which remained was that of reentry and the Russian Intention of exploring this was made clear in August 1958 by their sending of two dogs on a ballistic flight to an altitude of 280 miles with the successful recovery by ejection of the dog container during the descent.⁴

In the United States, meanwhile, on January 31, 1961, Mercury-Redstone 2 was fired carrying Ham, a 37-pound chimpanzee. He had received 219 hours of training in behavioral task performance over a 15-month period. Prior to flight, he had been subjected to Redstone launch profiles on the centrifuge at the U.S. Air Force Medical Laboratory, Dayton, Ohio.⁵ The spacecraft reached an altitude of 155 statute miles, landed 420 statute miles downrange, and was recovered. By the time it was recovered it was nearly filled with water because some small holes had been punctured in the lower pressure bulkhead at landing. Ham was rescued before the spacecraft had taken on too much water.⁶ From the engineering and operations point of view, the flight was a success except for the leaking spacecraft. The flight had demonstrated the validity of the Mercury spacecraft.

Life scientists, however, raised immediate, questions about the advisability of proceeding with the first suborbital manned flight because of the biological information telemetered back to tracking stations during the flight. As previously noted, both inside and outside NASA there had been those who, from the very beginning, had questioned the advisability of early manned space flight prior to extensive animal experimentation. As early as January 1959, when the Joint AF-NRC Committee on Bioastronautics had visited the Space Task Group at Langley, there had been a lively discussion about the need for such experimentation, not merely to test the life-support system of the spacecraft, but to determine the effects of combined stresses upon man. According to the résumé of the briefing given by STG:
 

The formal part of this briefing was well received and was followed by a rather lively discussion period. The main subject of the discussion was the need for animal flights preceding any manned flights in the proposed program. Many members of the group were strong in their opinion that any new mission involving a man could not be justified unless the mission had been previously validated by successful recovery of animals.⁷

At this briefing, representatives of the Space Task Group had pointed out that animal flights were involved in the program, but that the flights were "oriented directly at the Mercury objectives," that is, testing the system itself. The visiting AF-NRC Committee, it was reported, "felt that this approach was satisfactory," but "emphasized that our animal program should be pursued aggressively in that large lead times are involved." The résumé of the briefing concluded: "A rather definite impression was obtained that this group felt we should be utilizing animal validations to a greater extent than the briefing indicated."⁸

During the following months planning had proceeded as outlined by the Space Task Group to provide a limited number of animal flights prior to each progression in manned flight leading from suborbital to orbital flight. Prior to the establishment of the formal Mercury animal program, however, NASA was to make available a limited amount of space for the Air Force to carryout bio-pack testing in the Little Joe series. This may have resulted from the previous urging of the AF-NRC Committee on Bioastronautics. In any event, the animal program for Project Mercury was to consist of two phases: Flights of small primates in the Little Joe spacecraft, and flights of medium-size primates in Mercury spacecraft launched by Redstone and Atlas vehicles.⁹
 
These have already been discussed in connection with the sequence of testing carried out by NASA prior to manned flight. In the first phase, space had been made available to the USAF School of Aviation Medicine, Brooks AFB, Tex., for bio-packs containing American-born rhesus monkeys weighing 6 to 7 pounds. Although not an essential part of the Mercury program, these tests were to provide important data. Specifically, there was a biomedical evaluation of the accelerations expected during the abort of a Mercury flight at liftoff and shortly after liftoff. This test phase was successfully completed with the Little Joe flights on December 4, 1959, and in January 1960.

Following the initiation of the Little Joe bio-pack program, representatives of NASA and the McDonnell Aircraft. Corp., together with Navy, Army, and Air Force biomedical specialists, planned a further series of flight tests with animals to provide (1) animal verification of the feasibility of a manned flight, (2) data on the level of mental and physical activity that could be expected during a flight, and (3) a dynamic test of countdown procedures and training of support personnel in handling the biological aspects of manned flight. Briefly, it was agreed that existing Mercury spacecraft life-support, environmental-control, and instrumentation systems should be used without modification.

Responsibility for training the animals, preparing them for flight, and handling them after recovery was assigned to the 6571st Aeromedical Research Laboratory at Holloman Air Force Base. A NASA representative would serve as coordinator to integrate the animal flights into the total flight program. Two Air Force physicians were to be closely identified with the program. Lt. Col. James P. Henry, who served as NASA representative, had long enjoyed an international reputation in aviation medical research. His work had included high-altitude research in the late 1940's and the 1950's, including research to support the Air Force BOSS concept. Now, in 1959, he was a member of Dr. White's aeromedical team at STG. Dr. Hessberg, the second Air Force physician, directed the animal program at the 6571st Aeromedical Research Laboratory at Holloman AFB.

The decision to use chimpanzees rather than other primates for the Mercury animal program was aimed at providing the highest level of performance short of human. As described later by Henry and Mosely¹⁰ restraint would be minimal so as to make possible the performance of psychomotor tests. The electrocardiograms, body temperature, and respiratory movement would be recorded by the techniques planned for use with human astronauts. If possible, arterial pressure would be recorded. Urine would be saved for a study of steroid output and there would be photography of the subject.¹¹

Although the Aeromedical Research Laboratory at Holloman possessed animals, veterinarians, and space physiologists, it lacked facilities to obtain behavioral measurements of the animals. Accordingly, arrangements were made to train several chimpanzees under contract with the Wenner-Gren Aeronautical Research Laboratory, University of Kentucky. Subsequently, Air Force personnel were transferred from the Unusual Environments Section of the Aerospace Medical Laboratory, Aerospace Systems Division, Wright-Patterson AFB. Also, arrangements were made with the Walter Reed Army Institute of Research to aid in the establishment of a comparative psychology branch at AMRL. Training of eight chimpanzees began with the use of standard operator conditioning equipment and special restraint chairs.

As training progressed, the Veterinary Services Branch of AMRL was collecting normal baseline data on an entire colony of immature chimpanzees.¹² Study was also begun by specialists in ecology to determine the temperature and humidity tolerances of the chimpanzees. Concurrently AMRL personnel were designing and fabricating methods of restraint. A series of simulated flights was made on the centrifuge at the laboratory to determine the effects of acceleration and vibration on the chimpanzee, and also to evaluate the complete chimpanzee couch system. Medical recovery plans—described in the previous chapter—were being formulated by the Manned Spacecraft Center (formerly STG) at Langley, the Office of the Staff Surgeon, Patrick Air Force Base, and the Aeromedical Research Laboratory. A total of 35 veterinary technicians and 10 veterinary officers were trained. Lt. Col. Walter E. Brewer, USAF (VC), as previously noted, headed the program at Cape Canaveral.

This then, had been prelude to the MR-2 flight on January 31, 1961. Now, in the weeks following the animal suborbital flight which had tested the spacecraft system, STG prepared for the first manned suborbital flight.

4.  D. I. Fryer. "The Medical Sciences and Space Flight," R.A.E. News, Feb. 1964. See also Y. I. Gazdovsky, "Biological Experiments on Rockets and Artificial Earth Satellites," a paper presented at the Rocket and Satellite Symposium during the Fifth Revision of the Comité Spéciale, Année Geophysique Internationale, Moscow, July 30-August 9, 1958; Washington, D.C., National Academy of Sciences-National Research Council. See also A. G. Kousnetzov, "Some Results of Biological Experiments In Rockets and Sputnik II." J. Aviation Med., vol. 29, no. 11, Nov. 1958, pp. 781-784. See also N. M. Sisakyan, ed., Problems of Space Biology, Vol. 1, NASA TT F-174, 1963.

5.  Frederick H. Rohles, Jr., Marvin E. Grunzke, and Richard E. Belleville. "Performance Aspects of the MR-2 Flight," ch. 5 in Results of the Project Mercury Ballistic and Orbital Chimpanzee Flights, NASA SP-39, 1963. Mercury-Redstone 1, the first unmanned Redstone booster flight, had been fired Nov. 21, 1960. A premature engine cutoff activated the emergency escape system, but the spacecraft was recovered for reuse. The shot was repeated successfully on Dec. 19,1960.

6.  Walter C. Williams, Kenneth S. Kleinknecht, William M. Bland, Jr., and James E. Bost, "Project Review," in Mercury Project Summary Including Results of the Fourth Manned Orbital Flight, May 15 and 16, 1963, NASA SP-4.5,1963.

7.  Charles W. Mathews, Aeronautical Res. Engineer, Memo for Director of Project Mercury, Feb. 10, 1959.

8.  Ibid.

9.  Information is based on (1) Paul E. Purser, Spec. Asst. to Director, Project Mercury, Memo for File, Subj.: Additional Background Material on Project Mercury, Mar. 23, 1959; (2) James P. Henry, "Project Mercury—Status of the Animal Test Program," NASA Project Mercury Working Paper No. 1.58, Oct. 20,1960.

10.  James P. Henry and John D. Mosely, "Antecedents and Planning Aspects of the MR-2 Flight," ch. 2 in Results of the Project Mercury Ballistic and Orbital Chimpanzee Flights, NASA SP-39,1963.

11.  It was also decided that various types of performance would be required of the subjects to simulate the tasks of the human operator. These, Henry and Mosely reported further, Involved simple movements of the arms and hands, discrimination of visual signals, and acts requiring judgment. In the longer orbital flights the difficulty of the task would be raised to a level "that would approximate the man's task as closely as possible within the animals' capability."

12.  This program, carried out for the Air Force at the Univ. of Texas, represented one of the truly unique scientific resources of the nation. NASA was to continue its dependence on this resource as the space program progressed.