³ From [ref.169].
The space environment offers a unique opportunity to study the basic
properties of living Earth organisms with new tools and opens up new
areas of research for which biological theory fails to provide adequate
predictions. Unique components of the space environment of biological
importance are weightlessness or greatly decreased gravity, the
imposition of an environment disconnected from Earth’s 24-hour rotation
(particularly its effect on biorhythms), and cosmic radiation with
energies and particle sizes unmatched by anything produced artificially
on Earth ([ref.169]).
As progress is made in the manned exploration of space, the biological
effects of its unique environmental factors become of greater
importance. It is essential to determine the effects of space
environment on man’s ability to perform physical and mental tasks. In
addition, it is necessary to develop those systems required for his
survival and for his physiological and psychological well-being, both in
space and in his subsequent resumption of normal life patterns. Despite
nearly a century of research and development in environmental
physiology, a number of phenomena will be encountered in long-term space
flight with which we have had neither the experience that would enable
us to predict the effects nor to develop the necessary protective or
remedial measures ([ref.170]). Many of the experimental programs in
bioscience are being carried out or planned so that the deleterious
effects of these phenomena may be determined, predicted, or avoided
before they are encountered in manned flight.
Biological experimentation has been carried out in orbiting spacecraft
by Soviet and American scientists preparatory to manned space flight.
These first-generation exploratory experiments had the following
objectives:
(1) To discover whether complex organisms could survive space
conditions and to test life-support systems
(2) To determine whether complex organisms (dogs and primates) could
survive launch, orbital space flight, reentry, and recovery
(3) To determine the effects of space radiation and any obvious
effects of weightlessness on biological organisms
These biological studies indicate that manned space flight was
practicable, and the various cosmonaut and astronaut flights have proven
the validity of the results.
The National Academy of Sciences’ Space Science Board summer study
([ref.171]) recommended that—
NASA should exploit special features of the space environment as
unique situations for the general analysis of the
organism-environment relationships including, especially, the
role environmental inputs play in the establishment and
maintenance of normal organization in the living system. NASA
should support studies in ground-based and in orbiting
laboratories [biosatellites] on the biological effects of
gravity fields both above and below normal. This should be
considered a major responsibility of NASA in the area of
environmental opportunities. NASA should support studies of
biological rhythms in plants and animals including man as part
of its effort in environmental biology. Investigate by
observation of rhythms in organisms in space in (_a_) polar and
equatorial low orbits; (_b_) orbits less than, equal to and
greater than 22,000 miles. Properly designed experiments should
be conducted to explore the effects of different environmental
factors when these impinge simultaneously on test organisms.
The Panel on Gravity of the Space Science Board ([ref.67]) stated that
the major effects of low gravity would be expected in heterocellular
organisms that develop in more or less fixed orientation with respect to
terrestrial gravity and which respond to changes in orientation with
relatively long induction periods, including the higher plants. On the
other extreme are the complex primates which respond rapidly, but whose
multiplicity of organs and correlative mechanisms make the occurrence of
malfunction and disorganization probable, but not certain. The Panel
recommended emphasis on early embryogenesis and histogenesis,
particularly of plants during exposure to low gravity, and anatomical
studies after low gravity. They stated that perturbations of the
environment to which the experimental organism is exposed must be
limited or controlled to reduce uncertainties in interpretation of
results. At the same time, the introduction of known perturbations may
assist in isolating the effects due solely to gravity. Ground-based
clinostats and centrifuges should be used in conjunction with the
experiments, and an attempt should be made to extrapolate effects of low
gravity with the clinostat.
The study of the effects of unique or unknown space environmental
factors will probably yield unexpected results which may drastically
modify future technical approaches. The results from these biosatellite
studies will have broad application to longer term, manned space flight,
including manned space stations and lunar and planetary exploration.
The biosatellite program is a second-generation series of carefully
planned and selected experiments, including some highly sophisticated
experiments which have required several years of baseline study and
equipment development. These orbiting recoverable biosatellites will
provide opportunities for critical testing of major biological
hypotheses in the areas of genetics, evolution, and physiology.
The scientific community showed great interest in the biosatellite
program, and scientists from universities, industry, and Government have
submitted 185 flight experiments involving primates and other mammals,
vertebrate and invertebrate animals, micro-organisms, and plants.
The selected biosatellite experiments include studies at the cellular,
tissue, and organism levels, including embryological development and
growth experiments at the tissue level and physiological, behavioral,
reproductive, and genetic studies at the organism level. The experiments
are divided into six categories:
(1) Primates
(2) Mammals (nonprimate)
(3) Animal, cellular, and egg
(4) Plant morphogenesis, photosynthesis, and growth
(5) Biorhythm
(6) Radiation
Twenty experiments have been selected for flight to study the effects of
weightlessness and decreased gravity during 3- to 30-day orbital
periods. The experiments include a wide variety of plants and animals
from single-celled organisms to higher plants and animals. The effects
of weightlessness on the primate will be studied, especially the central
nervous, the cardiovascular, and the skeletal systems during 30-day
orbits.
Experiments have been selected to study the genetic and somatic effects
of weightlessness combined with a known source of radiation (Sr⁸⁵) to
determine if there are any antagonistic or synergistic effects
([ref.172]). Experiments are also included for studying the effects of
the unique environment of the Earth-orbiting satellite and removal from
the Earth’s rotation in relation to biological rhythms of plants and
animals.
Six biosatellites are included in the presently approved program, with
the first flight in 1966. They will be launched from Cape Kennedy by the
improved two-stage, thrust-augmented Thor-Delta into a nearly equatorial
circular orbit at an altitude of 180-200 miles for periods up to 30
days. Recovery will be by Air Force airplane during capsule/parachute
descent. The spacecraft weigh 1000-1200 pounds, have a 280-pound
recoverable capsule and, while in orbit, will not experience greater
than 1/10 000 g of acceleration. The life-support system will provide an
environment at sea-level pressure of 80 percent nitrogen, 20 percent
oxygen, and no more than 0.5 percent carbon dioxide with a temperature
of 75° F ±5° F.
All experiments are in various stages of development or testing and
flight test hardware has been and is being constructed. The experiments
and hardware are being subjected to preflight tests simulating launch
and recovery stresses. Rhesus, pigtail, and squirrel monkeys have been
subjected to the dynamic forces of the simulated flight under conditions
of complete, partial, and no restraint. Three types of centrifuges have
been used to simulate the flight profile. Primates were fully
instrumented with deep brain electrode implants, implanted catheters,
and other implanted sensors. During centrifugation, motion pictures were
taken. These primates were semirestrained in form-fitted couches which
allowed movement of the body while facing the accelerative force in a
ventrodorsal position (eyeballs in). In this series of tests, all
primates were normal following the tests and exhibited no unusual
behavior or effects. X-rays showed that implanted catheters and
electrodes remained in place, and there were no movements causing tissue
damage. However, when the primates were placed with their backs toward
the accelerative force, dorsoventral (eyeballs out), the animals
suffered visible damage. At 6 g there was no visible stress, but at 8 g
swelling of the lower eyelids was noticeable. At 11 g both eyelids were
swollen shut. In the biosatellite program, primates will be placed in
the semirestraint couches in a position facing accelerative forces,
ventrodorsal (eyeballs in), to prevent these effects.
chapter 7
_Manned Space Flight_