To provide virtually unrestricted
movements in all kinds of extravehicular activities in space, a Space
Activity Suit is proposed, consisting of a powerful elastic leotard to
counter the circulatory effects of breathing oxygen at a pressure of 170
mm.Hg. The physiological basis for such a garment is discussed.
A prototype garment has been worn in
the laboratory for up to 90 minutes while breathing at pressures of 30,
60, and 100 mm.Hg. Mobility and dexterity were excellent; no circulatory
embarrassment appeared. When an arm protected with an elastic gauntlet was
exposed to less than 8 mm.Hg absolute for 20 minutes, there was no sign of
gaseous swelling, dexterity was unimpeded, and circulation was maintained.
A successful Space Activity Suit
promises these advantages over gas-filled pressure suits: complete
mobility at small metabolic cost; simplicity and greater reliability; low
risk if the garment is torn; and physiological temperature regulation
without cooling equipment.
THE FULL PRESSURE SUITS used in U.S.
and Soviet space flight are enclosures of gastight cloth, pressurized
throughout with gas at 0.25 to 0.4 atmosphere. Physiologically the full
pressure suit is correct, but mechanically it is far from satisfactory.
Gas bag suits are stiff cylinders except where specific joints or flexible
structures are located, and the resulting limited mobility and high
metabolic cost of even limited activity while wearing one of these suits
cause serious restrictions to extravehicular activity, particularly that
which will be needed on the lunar surface.
Many kinds of flexible members have
been developed in the past thirty years to make such garments somewhat
mobile, and they have been satisfactory for emergency protection in
aircraft7 or space cabins. But, in contrast, space activities
call for all kinds of movements. A man on the lunar surface must be able
to walk easily, to stoop, to climb, to engage in digging and lifting.
These motions involve all the joints and flexures of the body—twisting and
flexing of the vertebral column from head to pelvis; tilting of the
pelvis; rotation, abduction, adduction, flexion, and extension of the arms
and legs; and translation of pivot points such as the movable
ball-and-socket shoulder joint. To match these complex motions in a
gas-filled suit is a formidable job, one which has not yielded to a
concentrated and prolonged effort in research and development.
In order to overcome these problems
of awkwardness, limited mobility, and high metabolic cost—which lead to
high oxygen cost, high heat production, and rapid onset of fatigue—a new
approach to protection in a vacuum seems to be necessary. For the past two
years we have been working on such a new approach. We call it the Space
Activity Suit, or SAS.
The starting point conceptually for
the SAS is that the human skin itself is an ideal pressure suit; the skin
is essentially gastight, elastic, and obviously non-restrictive to
motion. The whole body may be exposed to a vacuum for brief periods of one
to three minutes without any protection at all, the time limit being set
primarily by hypoxia. This has been established by exposures of primates
and dogs to a nearly complete vacuum, as reported by Bancroft and Dunn2;
Cooke and Bancroft3; Koestler12; Rumbaugh and Ternes16;
and Stephens, et al.17 In the laboratory Wilson20
has exposed human hands to near vacuum conditions (5 mm.Hg absolute
pressure), and swelling from evolution of gas was not evident until at
least two minutes and often as late as eight to ten minutes after
exposure. There are a number of other reports of harmless swelling in
hands exposed to low pressures—e.g., Ernsting, et al.4 Henry,
et al.10 and McGuire.13 It would seem that the skin
in its natural state exerts a useful degree of elastic counterpressure,
and adding mechanical pressure will prevent gas from forming.
Therefore, in order to provide the
added mechanical pressure necessary to protect a man in a vacuum, the
Space Activity Suit is constructed of a tough elastic mesh, providing a
porous restraint garment conforming entirely to the contours of the body,
which supports the skin and prevents it from yielding to the potential
distortion of gas forming in the tissues. A helmet sealed to the neck
provides oxygen for respiration. The effect of positive pressure breathing
on the circulation is compensated by the mechanical counterpressure
supplied by the elastic net, this requirement in fact calling for more
counterpressure than the skin needs for support. At the same time natural
thermoregulation takes place by evaporation of sweat without any external
cooling equipment, and there should be virtually unlimited mobility at a
very small increment in metabolic cost.
We have made a prototype SAS and
tested it with -positive pressure breathing at ground level. We have also
tested subjects' arms in a near-vacuum while protected with an elastic
sleeve and glove. In this report we describe the physiological basis for
the suit design and present what assurances there are in our testing with
early prototypes that the SAS is feasible for use in the vacuum of space.
The remarkable advantages of a successful SAS will be evident from the
HISTORY AND THEORY
The idea of using an elastic cloth
to provide limb counterpressure during positive pressure breathing is not
entirely new. In the early 1940's Henry,9 who introduced the
partial pressure suit, thought of the elastic suit concept, but did not
test it Some time later, Hull,11 at the Aeromedical
Laboratories at Wright-Patterson Air Force Base, actually had such a suit
constructed, but he didn't pursue the idea further because breathing was
uncomfortable and the heavy elastic material then available was stiff and
hard to bend. But positive pressure breathing with limb counterpressure
via capstans in the partial pressure suit was eminently successful in
providing get-me-down protection when decompression occurred in aircraft.
It also provided adequate protection for brief exposures to a near-vacuum.13
How has the situation changed since
the 1940's? The need for unrestricted mobility is far greater for
astronauts than for seated pilots in aircraft. In addition there have been
impressive postwar developments in fabric technology. Twenty years ago
such fibers as spandex, a synthetic elastomer of the polyurethane group,
were unknown. Power net and stretch nylon, now
standard materials for women's foundation garments, were
nonexistent. These fabrics can be knitted or woven in a wide range of
powers, from the very lightest used in sheer support stockings to heavy
weights used in "full control" girdles and in medical support garments. We
are confident that even more powerful fabrics can be developed. By
layering these fabrics it will be entirely feasible to produce 150-170
mm.Hg counterpressure over those parts of the body that require it, while
maintaining excellent flexibility of parts.
The combination of positive pressure
breathing and full body elastic counter-pressure affects a number of
physiological systems, most importantly the mechanics of respiration, the
systemic and pulmonary circulation, and thermoregulation. Each of these
functions has been analyzed and an approach has been developed to maintain
Pressure Breathing and Circulatory Balance
—Positive pressure breathing (PPB)
without compensating counterpressure, and then with counterpressure to the
trunk and limbs, has a long developmental history in aircraft protective
equipment. Routine use of PPB without compensating pressure is limited to
20-30 mm. Hg for any length of time. With counterpressure on the neck and
trunk and partial limb pressurization, as in the British jerkin, positive
breathing pressures of 80 mm. Hg can be tolerated for 10 minutes and
140mm. Hg can be tolerated for one minute, according to Ernsting.5
The partial pressure suits developed by the Air Force in the 1950's use
breathing bladders for respiratory compensation and capstans to draw up
the non-stretch suit materials over the limbs and trunk; they provide good
protection against decompression but the time of use under maximum PPB is
limited. And when the bladders and capstans inflate they seriously
decrease mobility. The suits are uncomfortable because of uneven pressure
distribution and because extensive body coverage by bladders prevents
evaporation of sweat. But the greatest drawback has been blood pooling and
accumulation of fluid in the limbs when the suits are worn pressurized for
longer than 20-30 minutes. The capstan partial pressure suit was never
designed for prolonged wear pressurized, or for use by active men in
For active men in the full vacuum of
space, we have chosen 170 mm.Hg (3.3 psi) of oxygen as the design figure
for PPB. 150 mm.Hg would approach the sea level partial pressure of oxygen
but gives a low alveolar oxygen tension and there would be no safety
factor for regulator accuracy, CO2 flushing, and similar
equipment hazards. Since PPB to 170 mm. Hg results in a 170 mm. Hg rise in
blood pressure, the blood, being essentially a closed fluid system, is
everywhere pressurized to 170 mm. Hg Matching tissue pressure must be
created all over the body. The circulating blood would rush into any low
pressure areas and pool there; small veins offer almost no resistance to
distention. If venous engorgement continued, the pressure within the veins
and capillaries would begin to rise significantly. Once this pressure
became greater than 14 cm of water gage pressure, measurable amounts of
excess fluid would be forced through the capillary walls and would begin
to accumulate in the tissues, causing swelling (edema). Neither the blood
pooling nor the edema would be markedly uncomfortable, but this
sequestering of fluid from the main circulation would result in a decrease
in circulating blood volume. Ernsting5 has shown that as little
as 200 cc lost in this manner, combined with the psychological stresses of
PPB, caused fainting, and even the most experienced subjects withstood no
more than an 800 cc decrease in circulating blood volume.
In order to provide total body
counterpressure, adjusted in magnitude so as to prevent significant
pooling or leakage of body fluids, we construct the SAS as a complete
leotard of elastic cloth, covering fingers, toes, hands, feet, arms, legs,
and torso. We feel from our preliminary studies that the applied force
will vary from segment to segment. Probably from 100 to 150 mm.Hg (2-3
psi) of force on the limbs, with up to 170 mm. Hg on the chest and
abdomen, will suffice.
Special structures under the elastic
material are used to fill large concavities and to allow for complex
motions where the elastic material does not slide or stretch readily. Such
areas are the central back, the axilla, the groin, and the shoulder. In
these areas we place shaped soft spongy pads or liquid filled pads which
transmit the force of the elastic garment to the skin. At the shoulder,
for example, the pad invests the whole joint, its liquid normally filling
the axillary space. When the shoulder pivot slides over the chest, the
fluid redistributes, maintaining a nearly constant volume as the inner
geometry is rearranged. These pads, or "soft joints," help to maintain a
constant pressure over concave areas so that the circulatory balance is
body system that must be maintained is thermoregulation. In the vacuum of
space thermoregulation is a problem of heat dissipation. Since an
astronaut's heat production will be sizable and variable if he is to cany
out useful activities, heat dissipation should be rapidly variable and
matched to the requirement of maintaining thermal balance. In the Space
Activity Suit, heat dissipation is via the nicely regulated mechanism of
The porous net of an SAS permits
instantaneous evaporation of any water which comes through the skin.
(Overgarments for micrometeorite protection and for control of thermal
radiation can be left loose and unsealed, like normal coveralls.)
Evaporation cools the skin, heat is dissipated, and sweating decreases.
The steady diffusional water loss
(insensible perspiration) in a vacuum should not exceed about 100 grams
of water lost per hour per man, an estimate based on extrapolating the
data of Hale, et al.8 and Webb, et al.19 This
represents a heat loss of 56 kcal/ hr, which is roughly half the metabolic
heat production of a man standing at rest. If there is water produced on
the skin from thermal sweating, it will be instantly evaporated and
cooling will take place at the rate of 0.56 kcal/gm of water lost. Not
only is evaporative cooling from sweating constantly available and under
full control by the body, but also it requires no additional machinery or
power. The only limit to this cooling approach is dehydration, and this
can be prevented by drinking during rest periods. If the astronaut's
work rate were maintained at a steady 300 kcal/hr (1200 Btu/hr) for four
hours, the total loss of water would be just over 2100 grams for the whole
period. It all evaporates and cools; there is no need for the body to
secrete 1.5 to 2 times the sweat required for cooling, as is often true
in an air environment on Earth.
Fig. 1. The high heat production
(metabolic cost) of walking slowly in pressurized full pressure suits,
from data of Wortz et al21 and Roth,15 compared to
the normal heat production of walking at common speeds without encumbrance
(data of Alt-man, et al1).
Properties of Human Skin—The
tensile strength of human skin is more than adequate to prevent serious
deformation or rupture in the small spaces between the strands of elastic
netting. According to Yoshi-mura,22 the average tension
required to tear adult human skin is 1600 gms/mm2, while the
maximum force of 170 mm. Hg which might be developed wearing the SAS is
2.3 gms/mm.2 The elastic materials we are now using show spaces
as big as 1 mm2 only when grossly overstretched
The skin as a barrier to gaseous
diffusion has been studied enough to permit educated guesses as how much
water vapor, oxygen, nitrogen, and carbon dioxide would be lost during
exposure to a vacuum. Our estimate of the rate of diffusion of water vapor
was given in the preceding section—about 100 gms per hour. This may well
be too generous, since the barrier layer of the skin increases its
resistance to diffusion as the skin becomes drier, and the immediate
effect of exposure to vacuum will be maximal drying of the superficial
Moyer, et al.14 feel that
the skin remains gastight when the transcutaneous pressure exceeds 760
mm.Hg. Diffusion of individual gases through the skin has been reported
by Fitzgerald6 as negligible for oxygen and about 180
ml(STPD)/hr for CO2 when there is no transcutaneous pressure
gradient. Dissolved nitrogen will be at a low value from the standard
procedure of breathing oxygen before going into the vacuum environment. We
estimate the nitrogen diffusion through the skin may be 10-20 ml/hr.
All of these estimates of gaseous
diffusion rates may have to be revised when experimental measurements can
be made during exposures to full vacuum. How-ever, on the basis of present
information, we do not expect any problem from excessively high loss by
Other Features— Reliability
of the SAS is high due to its drastic simplification compared to full
pressure suits. There are far fewer parts to fail, as witness the
elimination of cooling equipment and the absence of mechanical joints. The
backpack is simplified to a package containing only oxygen for breathing.
Safety is enhanced, since a tear in the tough elastic material would not
represent the catastrophe that a tear in a gas-filled suit means. The
complete suit (except for the outer coverall) will be small enough to tuck
into the interior of the helmet for storage.
But it must be kept in mind that the
first and major advantage of the Space Activity Suit is that it gives
total flexibility for all body parts. Since mobility essentially
unimpeded, the incremental energy cost of doing useful activities in the
SAS should be small Total mobility allows use of all the familiar actions
of body parts in carrying out a task—not the constrained and unfamiliar
motions used when "walking," for example, in a full pressure suit. The
bending forces in the elastic net are greater than those for normal
clothing, but these forces are expected to be small compared to the forces
the muscles normally generate when a man walks, climbs, stoops, digs, and
weights. We estimate that the metabolic cost of carrying out a full
schedule of walking and climbing activities will not increase by more than
10 to 20 percent in the SAS.
In contrast, the data for operating
in standard pressure garment assemblies show extreme incremental
increased with even mild activity. Some typical energy cost values for
walking at very slow speeds in pressure suits at 1 g are given in Figure
1. Increases of three times the cost of walking unpressurized are not
unusual. When we compare this metabolic cost with the anticipated 10 to 20
percent increment of the SAS, and when we recognize that many simple
activities are virtually impossible to do in conventional pressure suits,
the advantages of the SAS are compelling.
In order to demonstrate the mobility
inherent in the SAS concept and to study the effects of prolonged PPB with
elastic counterpressure, we have made an elastic leotard of several
layers so that increasing power is applied as layers are added. Initial
demonstrations of mobility, dexterity, and lack of circulatory effects
have been carried out with this prototype garment. In addition we have
exposed the arm and hand of two subjects protected with a double elastic
sleeve to a near-vacuum in an arm chamber, with no swelling and no harmful
First Prototype Garment—The
first prototype garment was carefully tailored to the individual
measurements of one subject. The power applied by donning each layer of
this garment was accurately calculated and achieved by the techniques
developed by the Jobst Institute of Toledo, Ohio, a supplier of medical
support garments. The material used was a special bobbinet woven with
cotton-covered 50-core rubber strands in the warp direction running
circumferentially around the limb and 100-denier nylon in fill. The
material has two-way stretch but the main power is developed
circumferentially in the direction of the rubber strands. Three layers
were made, each consisting of a pair of garments, one member of which ran
from the foot to the shoulders, without arms, and the other member from
the crotch to the base of the fingers, without legs. Each pair when donned
provided single coverage on the arms and legs and double coverage on the
trunk. Elastic gloves and footlets completed the assembly. The first two
pairs- of garments developed powers of 30 mm.Hg and the third pair
developed a power of 40 mm.Hg. The applied mechanical pressure of each
layer was checked and verified to be 30, 30, and 40 respectively, and the
combination gave approximately 100 mm.Hg by our technique of measurement.
Measuring the applied power was
accomplished with small flat inflatable pads fitted with two electrical
leads and a small pneumatic connection. The flat pads, or envelopes, were
made of 10-gage vinyl sheet and were cut in a roughly oval shape measuring
¾ inches. The inside surfaces of the two layers were fitted with thin
electrical contacts. Inflation with a syringe through the pneumatic
connector caused the contacts to separate. When the pads were placed under
the elastic material and against the skin, the pressure required to break
the contacts was our index of the force applied by the elastic garment.
The suit was always worn in the
laboratory with positive pressure breathing delivered by a helmet which
was connected to a simple flow-through compressed air supply. The helmet
sealed around the face and supplied pressure to the neck and most of the
head by means of a bladder. The suit and helmet are seen as worn in Figure
A single layer of the prototype
garment developing 30 mm.Hg was worn with 30 mm.Hg PPB for 90 minutes
with complete comfort. Two layers of the prototype garment, which
together develop 60 mm.Hg pressure, have been worn twice; the first
period was 90 minutes and the second 45 minutes. During the first and
longer trial, the subject complained of fatigue of the abdominal muscles
from unusual respiratory effort. A double-layered elastic corset was
added to the lower torso to aid in respiration and this relieved the
discomfort. Three layers were worn together to develop a pressure of
approximately 100 mm.Hg for 10 minutes.
Mobility and dexterity—While
it was evident to the subject and to the observers that there was
excellent mobility in the first prototype garment with either one, two, or
three layers, we devised a simple set of body motions to demonstrate that
there was good flexibility. Since the subjects in current full pressure
suits have difficulty in keeping up with a treadmill, and greater
difficulty in stooping, climbing, and other activities involving trunk
flexion, we asked our subject to do the following things, which he did
happily for a period of about 45 minutes. First, on the treadmill, the
subject walked at 3 mph on a level, then at 3 mph up a 5 percent grade,
then at 3 mph level with a 30-lb. backpack, and then at 4 mph with a 25
percent grade with the backpack. This last heavy exercise was maintained
for 30 seconds without great difficulty. The subject donned and buckled
his own backpack. Next the subject was asked to do a number of calisthenic
Fig. 2. Subject wearing
30 mm.Hg suit with 30 mm.Hg breathing pressure via air line being attached
To demonstrate hand dexterity we
asked the subject activities including sit-ups, push-ups, trunk bends in
all directions, squat jumps; knee bends, and toe touching. Again these
were accomplished without difficulty. Finally, he was asked to shovel sand
from one container to another using a long-handled shovel; he was asked
to climb a 14-foot ladder, up and down several times; and he was asked to
crawl on the treadmill at 1.2 mph both level and up a grade. All of these
activities were carried out without difficulty. There was no excessive
increase in heart rate nor excessive respiratory distress.
While direct metabolic data were not
taken, it was clear that the metabolic cost of doing these activities,
some of which are virtually impossible in a full pressure suit, was only a
little greater than would be measured if he had had no suit on at all.
Figures 3, 4, and 5 are photographs of the subject doing some of the
Lateral trunk flexion in the 60 mm.Hg assembly.
to write on a tablet, to
fasten and unfasten Swagelok connectors and other small items of hardware
and to operate the controls of an oscilloscope, electronic amplifiers, and
similar laboratory instrument None of these requests caused any great
problem al-though the cloth of the gloves reduced his tactile sense, as
would any cloth glove of equal weight. There was no striking diminution of
dexterity because of the elastic garment.
These simple tests of mobility and
dexterity are sufficient to show that the SAS is qualitatively different
from full pressure suits and partial pressure suits.
pressure breathing was adjusted to match the applied elastic
counterpressure of the prototype garments, namely 30 mm.Hg with a, single
layer, 60 mm.Hg with two layers, and 100 mm.Hg with the three layer
assembly. In the four different wearing trials the subject was usually
quite active. However, in one portion of the 90-minute trial at 60 mm.Hg
pressure, the subject was purposely kept still in a vertical position to
see whether blood pooling was a specific problem. For 15 minutes the
subject leaned against the ladder at an angle of 70° from horizontal, and
he was asked to relax and remain as quiet as possible. This was intended
to be an exaggerated duplication of the conditions leading to parade
ground faint. There was no noticeable change in pulse rate; the subject
felt perfectly well and the blood pressure measurements did not change
during this period.
Blood pressure measurements showed
that the arterial pressure increased in the amount that positive pressure
breathing was applied. Our subject normally had a standing resting
arterial pressure of 130/85. With one suit layer and 30 mm.Hg of PPB the
reading was 170/125. With 60 mm.Hg positive pressure and a 60 mm. garment
assembly, his standing resting pressure was 180/150. With 100 mm.Hg PPB
and elastic pressure applied, his standing resting pressure was 230/180.
Fig. 4. Climbing an extension ladder in the 60 mm.Hg assembly.
Fig. 5. Crawling on the treadmill at 1.2 mph in the 60 mm.Hg assembly.
There was no functional evidence,
then, of circulatory imbalance. Inspection revealed no evidence of edema
in the hands or feet. The subject had no immediate or late effects from
the wearing trials.
We had expected to see some edema or
evidence of circulatory embarrassment locally in concavities and joint
areas like the axilla. We had used padding and fills only in the inguinal
region and the center of the back. No edema appeared. Neither was there
any evidence of restriction of joint motion at the shoulder even though we
did not use a liquid filled bag with this prototype garment.
EXPOSURES TO NEAR-VACUUM
Preliminary studies have been
carried out with support from the Langley Research Center, NASA, to
demonstrate the ability of the elastic material to prevent gaseous
swelling under the skin.18
After studying various elastic
knitted and woven materials in order to find one with sufficient power to
increase the pressure of the arm tissue by approximately 100 mm.Hg, and
after testing the materials in a vacuum dessicator jar to make sure that
they did not lose their elasticity in a vacuum, we choose the bobbinet
material described previously.
After carefully measuring the arms
and hands of two experimental subjects, we had made a full-arm gauntlet
plus an oversleeve without fingers for each of the subjects. The two
sleeves together developed approximately 100 mm.Hg counterpressure by
computation. We explored the "soft joint" concept in a preliminary way,
but when we found that elbow and wrist joints did not need any aid to full
mobility, we did not use soft joints in those parts. We did, however,
mold silicone rubber pads to fit the palm and back of the hand for each
subject in order to round out those surfaces and to reduce the strong
elastic force on the edges of the hand.
In order to simulate conditions of
space for only one part of the body, we constructed a vacuum chamber into
which the arm could be sealed. We made this chamber of ½" Lucite in
the shape of a cylinder 18" in diameter and 36" long. The arm chamber was
fitted out in the interior with a number of electrical switches, knobs,
and colored lights, as shown in Figure 6. The subject tested mobility and
flexibility of his arm in the protective sleeve by manipulating these
knobs and switches.
We conducted tests in an altitude
chamber where total pressure was reduced to 155 mm.Hg (equivalent to
38,000 ft). By evacuating the arm chamber, the differential pressure was
150 mm.Hg, and the arm itself was exposed to near-vacuum conditions, or
5-8 mm.Hg total pressure. Pressure profiles of two of these experiments
are shown in Figure 7.
The results of the tests were
encouraging. The hand and arm remained perfectly flexible and dexterous,
did not show gas formation in the tissues, and apparently had adequate
circulation for 20 minutes There was no apparent increase in the metabolic
cost of doing arm and hand movements while wearing the sleeve. The
circulation seemed to be in balance; there was arterial inflow and venous
outflow in the axilla, as measured by a Doptone ultrasonic blood flowmeter
(Smith Kline Instrument Co.). There was no ischemic pain or skin damage,
and arm volume had not changed significantly after the test.
We tested again, at ground level, to
see if higher differential pressures with the same sleeve were tolerable.
When negative pressures of 150 mm.Hg and 200 mm.Hg were tried with the
same 100 mm.Hg sleeve, fluid accumulated in the arm, as evidenced by
increases in arm volume of 5 and 8 percent respectively following the
20-minute exposure. Some of this fluid leakage probably resulted from a
tourniquet effect at the point where the arm sealed to the arm chamber,
and some resulted from blockage of venous return due to the imbalances
between negative pressure and applied counterpressure. Except for a full
or tight feeling, there was no subjective discomfort, and the swelling was
gone in 8-10 hours.
Fig. 6. The Lucite arm chamber with beveled armhole in the near end.
Internal switches and lights are visible on the floor and walls. Scale in
Fig. 7. Pressure profiles of two experiments in the altitude chamber with
the protected arm at near-vacuum conditions in the arm chamber.
There are bound to be problems
ahead. Some of the problems which worried us originally have re-solved
themselves in trying the first laboratory prototypes; for example, most
small concavities do not need filling. Looking far ahead to possible
operation from a spacecraft, we are concerned about several things.
Donning the powerful elastic leotard
may be a real problem unless some clever solutions are found. The present
multi-layered assembly, with strategically placed zippers in the legs and
torso, is manageable, and can be donned unassisted, with practice, in
about 10 minutes. To achieve the full counterpressure needed for PPB at
170 mm.Hg we may have to use several layers of a more powerful fabric, and
the more power per layer the harder it is to pull the garment on. Donning
aids may be necessary, and they must be devised. Special tensioning
devices may also be helpful, e.g. speed lacings pulled tight after the
garment is on. Another solution would be to include blind gas-filled
bladders under the elastic material which would expand when the astronaut
leaves the spacecraft, thereby increasing the tension of the garment.
This would represent something of a compromise to the original SAS
principle, and we shall probably stay with elastic materials for the
present to see if the pure form of an SAS will be workable.
As we develop suits with higher
elastic power, we may lose some of the flexibility of the first SAS
prototypes. The more layers, the stiffer the garment feels. But elastic
fabrics with spandex yarns are significantly lighter than rubber core
fabrics of equal power. We should be able to achieve the necessary elastic
counter-pressure with fewer layers or lighter fabric.
Some elastic fibers lose their
elasticity on prolonged exposure to a hard vacuum. Our preliminary
testing, and information we have from manufacturers, are encouraging. One
of the spandex yarns particularly has shown excellent resistance both to
vacuum and to ultra-violet radiation.
Finally, there are serious potential
problems in the smooth application of adequate elastic counterpressure to
all parts of the body. We have already learned that some concavities, like
the trough over the lumbo-dorsal spines, need to be filled. It is
difficult to apply the elastic material in the axilla and over the
scrotum. So far, the tight fit of the prototype garment and padding over
the inguinal and femoral canals seems to have been adequate; we
have not seen edema or evidence of venous obstruction in the axillae.
More work will be needed with liquid-filled bags and with open-cell foams.
But beyond these problems with special body sites, we cannot be certain at
this stage that we can adequately compensate for the circulatory
imbalances caused by prolonged breathing at high positive pressure. We
are encouraged by our preliminary experiments, but we realize that at
even higher breathing pressures the problem will increase. The pooling of
blood, with loss of circulating blood volume, has not been easy to prevent
in partial pressure suits, and this is critical. Our hope is that new
elastic materials and carefully engineered tailoring will provide the
The concept of positive pressure
breathing at 170 mm.Hg with full body counterpressure from an elastic
leotard appears to be feasible and physiologically sound. This garment
should adequately protect an active man in a vacuum.
Mobility and dexterity are virtually
unhampered in the first prototype garments, and many extravehicular
activities which are either difficult or impossible in full pressure suits
should be easy to manage in the Space Activity Suit.
Assuming the satisfactory resolution
of the problems already foreseen, the Space Activity Suit promises major
additional advantages in simplicity, reliability, reduced accessory
equipment, and safety.
The work described in the section "Arm Exposures to a Near-Vacuum" was
accomplished under the terms of contract NAS1-6872 with the Langley
Research Center, National Aeronautics and Space Administration.
James Annis and Jerome Westin, M.D., gave generously of their energies and
skill in the laboratory studies. Altitude chamber studies were conducted
in the facilities of the Aero-medical Research Laboratory, Department of
Preventive Medicine, the Ohio State University.
major contribution was made by the Jobst Institute, Toledo, Ohio,
whose competence in the application of
biomechanicial pressure and whose enthusiasm for the project were
ingredients in fashioning the prototype garments.
1. ALTMAN, P. L., GIBSON, J. F., Jr., and WANG, C. C.: Hand-
book of Respiration. WADC TR 58-352. Aero Medical Laboratory,
Wright-Patterson Air Force Base, Ohio, August 1958.
R. W., and
J. E., II.; Experimental Animal
Decompressions to a Near Vacuum Environment.
cooke, J. P., and
bancroft, R. W.: Some
Cardiovascular Responses in Anesthetized Dogs During Repeated De-
compressions to a Near Vacuum. Aerospace Med., 37: 1148-1152, 1966.
nagle, R. E., and
parry, D. J.: The Boiling
of Tissue Fluids at Low Barometric Pressures. J. Physiol., 142:50P,
ernsting, J.: Some Effects
of Raised Intrapulmonary Pres-sure in Man. Technivision, Maidenhead,
fitzgerald, L. R.:
Cutaneous Respiration in Man. Physiol.
gell, C. F.,
hays, E. L., and
correale, J. V.:
Develop-mental History of the Aviator's Full Pressure Suit in the U. S.
Navy. J. Aviat. Med,, 30:241-250, 1959.
hale, F. C., WESTLAND,
R. A., and taylor,
C. L,. Baro-metric and Vapor Pressure Influences on Insensible Weight
Loss. J. Appl. Physiol., 12:20-28, 1958.
henry, J. P.: Personal
J. P., GREELEY, P. 0.,
meehan, J. P., and DRURY,
D. R.: A Case of Sudden Swelling of the Hands Occur-ring at 58,000 Feet
Simulated Altitude. Comm. Av. Med. Report No. 393, National Research
Council, Washington, D. C., 1944.
11. hull, W. E.: Personal
12. koestler, A. G.,
Editor: The Effect on the Chimpanzee of Rapid Decompression to a Near
Vacuum. NASA CH-329. National Aeronautics and Space Administration,
Washington, D. C., 1965.
13. McGUIRE, T. F.: Physiology and Operational Comparison of MC-1 and MC-3
(MC-4) Partial Pressure Suits. WADC TR 57-536 (I). Wright Air Development
Division. Wright-Patterson Air Force Base, Ohio, 1960.
14. MOYER, C. A.,
dillon, J. S., and
butcher, H. R.: Function of
Human Skin in Relation to its Macromolecular Structure. Arch.
Surg., 92:222-242, 1966.
15. roth, E. M.:
Bioenergetics of Space Suits for
Lunar Exploration. NASA SP-84,
National Aeronautics and Space Administration, Washington, D. C., 1966.
16. rumbaugh, D. M., and
ternes, J. W.: Learning-set
Performance of Squirrel Monkeys after Rapid Decompression to Vacuum.
Aerospace Med., 36:8-12, 1965.
17. stephens, L.,
hartman, J. L.,
lewis, 0. F.. KOESTLER, A.
G., and rhodes, J. M.:
of Chimpanzees During Rapid Decompression. Aerospace Med.,38:694-698,
18. webb, P. and
annis, J. F.: The Principle
of the Space Activity Suit. NASA CR-973. National Aeronautics and Space
Administration, Washington, D. C., 1967.
19. webb. P..
garlington, L. N., and
SCHWARZ, M. L.: Insensible
Weight Loss at High Skin Temperatures. J.
11:41-44, 1957. 20. wilson,
C. L.: Production of Gas in Human Tissues at
Low Pressures. Report No. 61-105, School of Aerospace
Medicine, USAF Aerospace Medical Center, Brooks Air
Force Base, Texas, 1961.
21. wortz, E. C.,
edwards, D. K.,
diaz, R. A.,
prescott, E. J., and
browne, L. E.: Study of
Heat Balance in Full Pressure Suits. Aerospace Med., 38:181-188,
22. YOSHIMURA, H.: Organ
Systems in Adaptation: the Skin. Chapter 8 in Dill, D. B., Adolph, E. F.,
and Wilber, C. G. (eds.), Adaptation to the Environment; Section 4,
Handbook of Physiology. American Physiological Society,
Washington, D. C., 1964.