I will never forget these guys setting the first footsteps
on the moon. It was a very impressive performance. Many years later when I
started to get interested in rebreathers I realised that enormous technique
had to be involved to get these astronauts there. Now with the appreciated
help of Mr. K. Culotta I managed to get pictures of this equipment. The
Portable Life Support System (PLSS) for the Apollo A7L Space suits was built
by a division of United Aircraft Corporation called Hamilton Standard (now
Hamilton Sundstrand). There are related patents issued to United Aircraft
which have relation. They are patent numbers 3,170,303; 3,289,748;
3,343,536; and 3,345,641. On the website of Hamilton you will find a huge
information source of these space systems.
The PLSS includes oxygen bottles, water storage tanks, a
sublimator, a fan/separator/pump/motor assembly, a contaminant control
cartridge, various regulators, valves and sensors, communications and the
microprocessor caution and warning system module.
System ventilation airflow enters the suit from the PLSS at
the helmet and flows from behind the head, over the face and down through
the suit. Oxygen, carbon dioxide and water vapour from breathing leave the
suit through the liquid-cooling and ventilation garment near the astronaut's
elbows and feet and return to the PLSS.
The flow first goes through the PLSS contaminant-control
cartridge, where activated charcoal and lithium hydroxide remove odours and
carbon dioxide. Next, it passes through a fan that maintains a flow of about
six cubic feet per minute. Gas flow is then routed to the sublimator, a
cooling device which condenses water vapour and permits its removal by a
slurper and by the rotary separator. The water that is removed from the gas
flow is pumped primarily into the PLSS water storage tanks for reuse in
cooling the astronaut.
The sublimator also cools the ventilation flow to about 12°
C. The oxygen then moves through a flow sensor and back to the suit inlet.
Oxygen is added, as needed, to the ventilation flow from the primary oxygen
tanks, entering the ventilation loop downstream of the flow sensor. Suit
pressure is maintained at approximately 0.7 psid (0,047 bar)(15 psid = 1
bar) above ambient pressure* in the intravehicular mode, and at 4.3 psid (0,29 bar)(15 psid = 1
bar)in the extravehicular mode. The astronaut selects the mode by manually
operating an actuator located on the display and control module.