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CX2SA > TECH 23.06.06 23:25l 128 Lines 7564 Bytes #999 (0) @ WW
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Subj: The spacesuit (2/2)
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Sent: 060623/2119Z @:CX2SA.LAV.URY.SA #:15673 [Minas] FBB7.00e $:15673_CX2SA
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HISTORY OF SPACESUITS
=====================
The Mercury spacesuit was a modified version of a U.S. Navy high altitude jet
aircraft pressure suit. It consisted of an inner layer of Neoprene-coated
nylon fabric and a restraint outer layer of aluminized nylon. Joint mobility
at the elbow and knees was provided by simple fabric break lines sewn into the
suit; but even with these break lines, it was difficult for a pilot to bend
his arms or legs against the force of a pressurized suit. As an elbow or knee
joint was bent, the suit joints folded in on themselves reducing suit internal
volume and increasing pressure.
The Mercury suit was worn "soft" or unpressurized and served only as a backup
for possible spacecraft cabin pressure loss--an event that never happened.
Limited pressurized mobility would have been a minor inconvenience in the
small Mercury spacecraft cabin.
Spacesuit designers followed the U.S. Air Force approach toward greater suit
mobility when they began to develop the spacesuit for the two-man Gemini
spacecraft. Instead of the fabric-type joints used in the Mercury suit, the
Gemini spacesuit had a combination of a pressure bladder and a link-net
restraint layer that made the whole suit flexible when pressurized.
The gas-tight, man-shaped pressure bladder was made of Neoprene-coated nylon
and covered by load bearing link-net woven from Dacron and Teflon cords. The
net layer, being slightly smaller than the pressure bladder, reduced the
stiffness of the suit when pressurized and served as a sort of structural
shell, much like a tire contained the pressure load of the innertube in the
era before tubeless tires. Improved arm and shoulder mobility resulted from
the multilayer design of the Gemini suit.
A Spacesuit for Apollo Moon Walking
-----------------------------------
Walking on the Moon's surface a quarter million miles away from Earth
presented a new set of problems to spacesuit designers. Not only did the Moon
explorers' spacesuits have to offer protection from jagged rocks and the
searing heat of the lunar day, but the suits also had to be flexible enough to
permit stooping and bending as Apollo crewmen gathered samples from the Moon,
set up scientific data stations at each landing site, and used the lunar rover
vehicle, an electric-powered dune buggy, for transportation over the surface
of the Moon.
The additional hazard of micrometeoroids that constantly pelt the lunar
surface from deep space was met with an outer protective layer on the Apollo
spacesuit. A backpack portable life support system provided oxygen for
breathing, suit pressurization, and ventilation for moon walks lasting up to 7
hours.
Apollo spacesuit mobility was improved over earlier suits by use of bellows
-like molded rubber joints at the shoulders, elbows, hips and knees.
Modifications to the suit waist for Apollo 15 through 17 missions added
flexibility making it easier for crewmen to sit on the lunar rover vehicle.
From the skin out, the Apollo A7LB spacesuit began with an astronaut-worn
liquid-cooling garment, similar to a pair of "long-johns" with a network of
spaghetti-like tubing sewn onto the fabric. Cool water, circulating through
the tubing, transferred metabolic heat from the Moon explorer's body to the
backpack and thence to space.
Next came a comfort and donning improvement layer of lightweight nylon,
followed by a gas-tight pressure bladder of Neoprene-coated nylon or bellows
-like molded joints components, a nylon restraint layer to prevent the bladder
from ballooning, a lightweight thermal super-insulation of alternating layers
of thin Kapton and glass-fiber cloth, several layers of Mylar and spacer
material, and finally, protective outer layers of Teflon coated glass-fiber
Beta cloth.
Apollo space helmets were formed from high strength polycarbonate and were
attached to the spacesuit by a pressure-sealing neck ring. Unlike Mercury and
Gemini helmets, which were closely fitted and moved with the crewman's head,
the Apollo helmet was fixed and the head was free to move within. While
walking on the Moon, Apollo crewmen wore an outer visor assembly over the
polycarbonate helmet to shield against eye damaging ultraviolet radiation, and
to maintain head and face thermal comfort.
Completing the Moon explorer's ensemble were lunar gloves and boots, both
designed for the rigors of exploring, and the gloves for adjusting sensitive
instruments.
The lunar surface gloves consisted of integral structural restraint and
pressure bladders, molded from casts of the crewmen's hands, and covered by
multi-layered super insulation for thermal and abrasion protection. Thumb and
fingertips were molded of silicone rubber to permit a degree of sensitivity
and "feel." Pressure-sealing disconnects, similar to the helmet-to-suit
connection, attached the gloves to the spacesuit arms.
The lunar boot was actually an overshoe that the Apollo lunar explorer slipped
on over the integral pressure boot of the spacesuit. The outer layer of the
lunar boot was made from metal-woven fabric, except for the ribbed silicone
rubber sole; the tongue area was made from Teflon-coated glass-fiber cloth.
The boot inner layers were made from Teflon-coated glass-fiber cloth followed
by 25 alternating layers of Kapton film and glass-fiber cloth to form an
efficient, lightweight thermal insulation.
Spacesuits for Skylab and Apollo-Soyuz Nine Skylab crewmen manned the Nation's
first space station for a total of 171 days during 1973 and 1974. They wore
simplified versions of the Apollo spacesuit while doing the historic repair of
the Skylab and changing film canisters in the solar observatory cameras.
Jammed solar panels and the loss of a micrometeoroid shield during the launch
of the Skylab orbital workshop necessitated several spacewalks for freeing the
solar panels and for erecting a substitute shield.
The spacesuit changes from Apollo to Skylab included a less expensive to
manufacture and lightweight thermal micro-meteoroid over-garment, elimination
of the lunar boots, and a simplified and less expensive extravehicular visor
assembly over the helmet. The liquidcooling garment was retained from Apollo,
but umbilicals and astronaut life support assembly (ALSA) replaced backpacks
for life support during spacewalks.
Apollo-type spacesuits were used again in July 1975 when American astronauts
and Soviet cosmonauts rendezvoused and docked in Earth orbit in the joint
Apollo-Soyuz Test Project (ASTP) flight. Because no spacewalks were planned,
U.S. crewmen were equipped with modified A7LB intra- vehicular Apollo
spacesuits fitted with a simple cover layer replacing the thermal
micrometeoroid layer.
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