backpack. Oxygen for breathing on 
EVAs was in a pressurized tank in the 
pack. The oxygen was metered into the 
suit by a regulator that also controlled 
the suit pressure. The oxygen was circu- 
lated by a small fan driven by an electric 
motor. Gas leaving the suit contained 
the carbon dioxide exhaled by the astro- 
naut, as well as evaporated sweat and 
trace gases, such as sulfur dioxide and 
hydrogen sulfide, produced by the astro- 
naut. The trace gases were absorbed in 
the backpack by a filter bed made of 
activated charcoal. The sweat was con- 
densed by a device, called a cooling heat 
exchanger, that cooled and dehumidi- 
fied the gas before it was recirculated 
back into the suit. The carbon dioxide 
was removed by a chemical, lithium 
hydroxide. The gaseous carbon dioxide 
reacted with the hydroxide to form a 
salt, lithium carbonate. This reaction 
removed the carbon dioxide as fast as it 
was produced and the suit gas, enriched 
by oxygen from the storage tank, was 
sent back into the helmet through a 
duct. 
The LCG water that had been 
warmed by the astronaut’s body heat 
was pumped into a cooling device in the 
backpack called a sublimator. Water 
from a separate storage tank in the pack 
was also fed into the sublimator, where 
it was evaporated by exposing it to the 
vacuum of space. This evaporation pro- 
cess removed heat from the LCG water 
so that the cooled water could be recir- 
culated. The water vapor from the subli- 
mator was simply vented overboard. On 
the earth, this Apollo backpack weighs 
about 130 pounds, but on the moon it 
weighs only about one-sixth as much. 
The Apollo program demonstrated 
that space-suited astronauts can work 
routinely outside their spacecraft. The 
Skylab program, which followed in the 
early 1970s, demonstrated the useful- 
ness of EVAs. Skylab’s EVAs were 
quite different from the tasks of lunar 
surface exploration done during Apollo. 
The primary reason for the Skylab’s 
EVAs, planned prior to the launch of 
that spacecraft, was to periodically 
change film canisters in cameras 
mounted outside the cabin as part of 
earth resources and astronomy experi- 
ments. Th$ astronauts worked near the 
capsule airlock so that a life-support 
system could be maintained through an 
“umbilical” hose and an autonomous 
backpack was not necessary. The Sky- 
lab spacesuit assembly was essentially 
the same as that of the Apollo system. 
During the unmanned launch of the 
Skylab laboratory, one of the solar pan- 
els was damaged and failed to deploy in 
orbit. Part of the cabin’s exterior insula- 
tion was also damaged so that the cabin 
became very hot. If these problems had 
not been solved, the entire Skylab pro- 
gram would probably have been can- 
celed. The only solution was to have 
suited astronauts launched in another 
spacecraft manually perform the repairs 
outside the Skylab craft. The problems 
were compounded because those repairs 
required the astronauts to work 100 
miles up in space on capsule areas where 
no handrails or tether attachment points 
had been installed. Handrails are 
needed for safe movement between the 
airlock and the work site, where a tether 
could be attached to hold the astronaut 
in position while working. The first 
Skylab crew nevertheless successfully 
made the needed repairs. 
During the period between the end of 
the Skylab program in the early 1970s 
and the first shuttle flight in 1981, a new 
spacesuit was developed. For one thing, 
women were admitted into the space 
program as astronauts beginning in 
1 977. To no one’s surprise, they needed 
smaller suits than those worn by the 
male astronauts. From the initial Mer- 
cury program through the Skylab pro- 
gram, all the spacesuits had been cus- 
tom tailored to fit individual astronauts. 
But beginning with the space shuttle in 
1981, the suits have been made in sepa- 
rate units of different but standard sizes 
and were assembled for the astronauts 
more or less “off the rack.” The new 
spacesuit when assembled is similar to 
the Skylab suit, except for the torso, 
which is now made of fiberglass instead 
of rubber and fabric. The life-support 
systems in the backpack are perma- 
nently attached to the hard fiberglass 
torso, rather than being removable, as in 
Apollo. This change improved the reli- 
ability of the systems and simplified the 
hours-long checkout procedures re- 
quired before an EVA. The shuttle suit 
operates with an internal gas pressure of 
approximately one-fourth of an atmos- 
phere — the same pressure as that of 
earlier suits. The life-support system is 
functionally identical to that of the 
Early mission suits, shown here, 
were custom tailored for individual 
astronauts. Today’s suits come in 
standard small, medium, and large 
size units that are then assembled 
to give a "custom" fit. 
Apollo system, although considerable 
redesigning was required to integrate 
the systems with the hard torso. 
The shuttle spacesuit and life-support 
system will be used for the first few 
years of the shuttle program to allow the 
astronauts to perform a wide range of 
EVA tasks. Many satellites, such as the 
large space telescope, are being de- 
signed for maintenance and repair by 
suited crewmen. This is simpler and 
cheaper than trying to accomplish the 
same job with a robot. Nevertheless, 
automated systems are needed for other 
jobs, such as maneuvering large pay- 
loads in the shuttle’s cargo bay, and for 
assembling large space structures. 
The current space shuttle EVA sys- 
tem has many shortcomings that pre- 
clude its use for routine space construc- 
tion operations. About two pounds of 
56 
