Why Magazines are Refrigerated
by Al Wellman
Updated 05 February 2000
Modern propellants contain solvents. These will outgas if not
kept at a regulated temperature and lose their properties. The temperature
depends on the type of propellant used. Outgassing of solvents is
of concern for two reasons:
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Diminished solvent concentrations increase the burning rate of the powder,
which would at least change the anticipated projectile velocity and possibly
generate dangerous chamber pressure when guns are fired.
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Outgassed solvents (typically ethers and alcohols) may create flammable
or explosive atmospheres when powder canisters are opened.
Another advantage of refrigerating magazines is to extend the useful life
of smokeless powder. Nitrocellulose smokeless powder spontaneously
decomposes with the production of oxides of nitrogen which react with moisture
to form acids which accelerate further decomposition. The rate of
decomposition was considered acceptable at temperatures below 20 degrees
Celsius, but accelerated dangerously when temperatures exceeded 35 degrees
Celsius. Spontaneous combustion of decomposing powder was blamed
for loss of the battleships Jena in 1907 and Liberte in 1911.
Initial velocity of projectiles varies directly with powder temperature.
Maintaining a uniform powder temperature simplifies ballistic computations
and reduces dispersion of salvos fired from different magazines.
Finally, a low temperature magazine is safer because it increases the
amount of thermal energy required to initiate combustion. A heated
shell fragment or other potential ignition source may lose enough energy
in elevating the temperature of magazine walls, air and canisters to drop
its temperature below the ignition point.
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