Pat Flannery wrote:
I was looking at some cutaways of spacecraft, and am trying to figure
something out.
Both Gemini and Apollo incorporated significant cooling radiators in
the designs (external on the Apollo SM, mounted inside the skinning
of the Gemini equipment module), but how was cooling handled on
Mercury? There aren't any radiators on its exterior, and although
you could use water boil-off for cooling on fairly short flights,
the 34 hour long Faith 7 flight would seem to need a lot of water to
make this concept work for that period of time.

The first hit I got on a web search for "Mercury Capsule Cooling" was:

http://ntrs.nasa.gov/search.jsp?R=14153&id=8&qs=Ns%3DHarvestDate%257C0% 26N%3D4294967096%26Ne%3D25

For which the abstract reads:

The approach to orbital thermal control of the Project Mercury
capsule environment is relatively unsophisticated compared with
that for many unmanned satellites. This is made possible by the
relatively short orbital flight of about 4 1 2 hours and by the
presence of the astronaut who is able to monitor the capsule
systems and compensate for undesirable thermal conditions. The
general external features of the Mercury configuration as it
appears in the orbital phase of flight are shown. The conical
afterbody is a double-wall structure. The inner wall serves as a
pressure vessel for the manned compartment, and the outer wall, of
shingle type construction, acts as a radiating shield during
reentry. Surface treatment of the shingles calls for a stably
oxidized surface to minimize reentry temperatures. The shingles
are supported by insulated stringers attached to the inner
skin. Areas between stringers are insulated by blankets of
Thermoflex insulation. This insulation is especially effective at
high altitude due to the reduction of its thermal conductivity
with decreasing pressure. As a result of the design of the
afterbody for the severe reentry conditions, the heat balance on
the manned compartment indicates the necessity for moderate
internal cooling to compensate for the heat generation due to
human and electrical sources. This cooling is achieved by the
controlled vaporization of water in the cabin and astronaut-suit
heat exchangers.

Not sure if there is an online copy, you may have to order paper. I
notice they mention 4 1/2 hours vs the 34 of that other flight. Might
have to get the paper to resolve that one. Maybe they just left the
rest of the capsule (un)insulated "just enough?"

rick jones
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