In the Mercury animal test program a Redstone missile carried the
chimpanzee Ham on a ballistic flight to a height of 155 miles to provide
animal verification of the success with which the Mercury system could
be applied to manned flight. The male chimpanzee was trained to perform
a two-phased reaction task during the 16 minutes of flight. The
chimpanzee Enos was put into orbit for 3 hours and 20 minutes. Results
of the two flights gave the following information:
(1) Pulse and respiration rates during both the ballistic (MR-2) and
the orbital (MA-5) flights remained within normal limits
throughout the weightless state. Effectiveness of heart action, as
evaluated from the electrocardiograms and pressure records, was
also unaffected by the flights.
(2) Blood pressures, both arterial and venous, were not significantly
changed from preflight values during 3 hours of the weightless
state.
(3) The performance of a series of tasks involving continuous and
discrete avoidance, fixed ratio responses for food reward, delayed
response for a fluid reward, and solution of a simple oddity
problem was unaffected by the weightless state.
(4) Animals trained in the laboratory to perform during simulated
acceleration, noise, and vibration of launch and reentry were able
to maintain performance throughout an actual flight.
From the results of the MR-2 and MA-5 flights, the following conclusions
were drawn:
(1) The numerous objectives of the Mercury animal test program were
met. The MR-2 and MA-5 tests preceded the first ballistic and
orbital manned flights, respectively, and provided valuable
training in countdown procedures and range monitoring and recovery
techniques. The bioinstrumentation was effectively tested and the
adequacy of the environmental control system was demonstrated.
(2) A 7-minute (MR-2) and a 3-hour (MA-5) exposure to the weightless
state were experienced by the subjects in an experimental design
which left visual and tactile references unimpaired. There was no
significant change in the physiological state or performance of
the animals as measured during a series of tasks of graded
motivation and difficulty.
(3) Questions were answered concerning the physical and mental demands
that the astronauts would encounter during space flight, and it
was shown that these demands would not be excessive.
(4) It was also demonstrated that the young chimpanzee can be trained
to be a highly reliable subject for space-flight studies.
The suborbital ballistic flight of Ham on January 31, 1961, was the
prelude to Alan R. Shepard’s suborbital space flight, while the orbital
flight of Enos on November 29, 1961, preceded the orbital flight of John
H. Glenn.
The fact that we now categorize these events as belonging to the rather
distant past, although they occurred only about 4 years ago, serves to
emphasize the pace of development in the exploration of space. While the
chimpanzee program may pale in the light of subsequent successes, its
scientific and technological contribution should not be overlooked.
The significance of this project can be fully appreciated, and its
contribution judged, only by considering the lack of knowledge existing
at the time of its conception. In addition to its essential training
function, this project verified the feasibility of manned space flight
through operational tests of the Mercury life-support system. It
demonstrated that complex behavioral processes and basic physiological
functions remained essentially unperturbed during brief exposures to
space flight. The Mercury chimpanzee program marked the first time that
physiological and behavioral assessment techniques were combined for
evaluating the functional efficiency of the total organism in space.
Perhaps the ultimate contribution of this program was in providing the
framework of knowledge upon which future scientific experiments on
biological organisms, exposed to flights of extended durations, must be
based. Biosatellite experiments designed to seek more subtle and elusive
effects of prolonged space flight on biological functioning will require
even more refined and difficult techniques, but will depend heavily on
the groundwork laid in these early steps of Project Mercury.
A summary of the more important animal suborbital and orbital flights
during the period 1957 to 1964 is presented in table VII.
In another NASA-supported flight, _NERV_ 1, various experiments were
carried in a suborbital flight of 20 minutes. _Neurospora_ molds showed
a surprisingly high level of mutation, but the control molds also had
high rates.
The Discoverer XVII and XVIII flights, to which the Air Force
contributed, resulted in many interesting findings relative to the
responses of living systems to space flight. On the Discoverer XVII
flight, samples of human gamma globulin and rabbit antiserum specific
for human gamma globulin showed an increase in reactivity, and samples
of synovial and conjunctival cells showed no changes in their
cytological characteristics.
Discoverer XVIII was launched during a massive solar flare which lasted
for the first 13 hours of the 48-orbit, 3-day flight. _Neurospora
conidia_, nerve tissue, algae, human bone marrow, eyelid tissue, gamma
globulin, and cancer cells were put in orbit. The results indicated that
biological specimens may be able to withstand radiation from solar
flares with a minimum of shielding and that aluminum shielding may be
better than lead.
In 1949, the U.S.S.R. began a systematic, uninterrupted research program
in biological space experimentation. They have studied the effects of
physical stress, immune reactions, psychobiology and behavior, genetics,
and responses to environmental factors such as spacecraft dynamics and
ambient radiation. The organisms and biological materials included
tobacco mosaic and influenza viruses; T2 and T4 bacteriophage; _Bacillus
aerogenes_; lysogenic bacteria; _Clostridium butyricum_; _Escherichia
coli_; actinomycetes; yeasts; _Chlorella pyrenoidosa_; seeds of fir,
pine, onion, corn, lettuce, wheat, cabbage, carrot, buckwheat, cucumber,
beet, _Euonymus_, fennel, mustard, pea, broad bean, tomato, and nutmeg;
_Tradescantia paludosa_; _Ascaris_ eggs; snail spawn; _Drosophila
melanogaster_; loach roe; frog eggs and sperm; guinea pigs; mice; rats;
hamsters; rabbits; dogs; monkeys; human and rabbit skin; HeLa tissue
cultures and other tissues (refs. [ref.167] and [ref.168]).