Historically, biological experiments aboard rockets and satellites have
been limited to a "piggyback" and "noninterference" basis on military
rockets. For the past few years, however, as the effort toward manned
space flight leading to lunar and Martian landings increased, more
attention was devoted to experiments designed to show the effects of the
space environment on living systems. As in the balloon flight programs,
the U.S. Army, Navy, and Air Force played an important role, reaching
what might be considered a high point with the successful launch and
recovery of a ballistic rocket experiment with monkeys Able and Baker.
Aerobee rockets as well as Thor IRBM’s carried biological payloads
consisting of mice and monkeys on six launches, contributing to our
knowledge of the effects of weightlessness and radiation on higher
animals.
Van der Wal and Young ([ref.78]) used Thor-Able combinations to serve as
boosters for lifting a 20-pound biocapsule to a peak altitude of 1400
miles and over a distance of about 5300 miles from Cape Canaveral to the
west coast of Africa. Weightlessness was attained for a period of almost
40 minutes. During reentry into the atmosphere, a peak deceleration of
about 60 g was reached. Each of the three capsules flown carried one
mouse (Mouse-in-Able); two of the mice were instrumented for heart-rate
telemetry. Although all three mice were lost, the two experiments with
Laska and Benji yielded physiological results.
The experimenters designed effective instrumentation for registering the
electrical activity of the mouse’s heart through a single commutated
telemetry channel. Records were obtained for both animals during various
portions of the flight. The results indicate that both animals were
alive when the nose cones hit the water.
Two South American squirrel monkeys (Gordo and Baker) and a rhesus
monkey (Able) were launched into space from Cape Canaveral in 1958 and
1959 by U.S. Army Jupiter missiles. The vehicles reached speeds of
approximately 10 000 mph and altitudes of 300 miles on flights which
lasted about 15 min.
Time courses of cardiac and respiratory rates ([ref.80]) of the two
squirrel monkeys showed that the noise of the engine at liftoff
immediately produced an increase in their heart rates. Respiration also
increased temporarily, but slowed later with increasing acceleration.
Heart rates fluctuated considerably during launch acceleration, which
reached about 15 g at cutoff.
The period of free flight and weightlessness was characterized by
pronounced fluctuations of heart activity in the postacceleration phase.
Thereafter, the heart rate of Baker remained relatively constant,
whereas the cardiac activity of Gordo fluctuated markedly and decreased
slowly almost to the end of his flight. Slight changes, which were
transient and not pathological in nature, were also noted in the
electrocardiogram. Gordo’s respiration was very shallow during maximum
launch acceleration, when Baker’s reached its highest value, only to be
approximated again during reentry when forces of about 35 g were
encountered.
Able’s cardiac and respiratory rates indicated that, after an initial
startle reaction, the heart rate dropped transiently and then increased
steeply, reaching a maximum of 259 during the 10-second interval at peak
acceleration. Respiration increased only slightly throughout the
launching phase. There was a period of tachycardia during
postacceleration weightlessness, after which the heart rate declined
steadily and was disturbed only by several startling missile events. At
the end of the subgravity phase, Able’s cardiac rate was slightly below
normal.
Although the periods of high g force and free flight were short, the
extremes were considerable, and the changes from one state to the next
were rapid. In spite of this, the cardiovascular, hemodynamic, and
electrocardiographic phenomena were remarkably well maintained.
Apparently the animals were not in serious plight at any time. That
psychological factors entered into the observed phenomena is clearly
evident from the increase in cardiac rate associated with the noise of
the engine prior to liftoff and also from the cinematographic record of
facial expressions. Nevertheless, the integrated responses indicated
that the animals’ physiological states remained sufficiently normal to
insure a safe flight.