Aerospace & Defense Technology - June 2022 - 6

Military Space Technology
HAT/FP Thermostatic
Drain Valve.
perature regulation
unit for human-operated
vehicles to
avoid potentially
damaging thermal
variation.
Outer Space
We've already
discussed the extreme temously
frigid,
or simply susceptible
to cold weather. These mechanically
operated valves are normally closed.
Once temperatures dip towards freezing,
the valve will automatically open
to bleed off the cold water from the
supply lines and prevent freezing. The
valve will close again once it senses the
warmer backfilled water, conserving
the supply. These valves will keep operating
systems running and minimize
system interruptions, no matter how
cold it gets.
Extreme Heat
On the other end of the Kelvin scale
are environments with extreme heat.
Death Valley is the hottest place on
Earth, with a highest recorded temperature
of 134 °F (56.6 °C). Most machinery
will be able to operate normally in
these conditions, with little requirements
for design modifications. The
main consideration for Earth-based deserts
is in relation to small particles of
dust and sand entering systems and
causing component degradation. To
avoid shortened operating lifespans,
designers should ensure minimal access
points into a device's interior and an IP
rating of at least IP66, otherwise known
as " dust tight. "
Death Valley is not overly hot compared
to the heat found outside of our
planet's atmosphere. Without the ozone
layer as protection to filter out the Sun's
heat, those directly in its rays can expect
temperatures to reach 250 °F (121 °C).
As outer space's ambient temperature
can quickly vary from extreme cold to
extreme heat, devices and ships must be
well insulated from all temperatures
depending on whether one is facing the
Sun or not. Design engineers should
include thick, insulated walls and a tem6
peratures
found in space and how
designers can prepare for them, but the
intricacies of space travel are not limited
to extreme thermal variation. For
systems sent into the upper atmosphere
and beyond into the stars, considerations
must be made for reducing payload
weight, prolonging service life, and
minimizing battery drain.
First, weight: As a rule of thumb, the
cost to launch 1 lb. of anything into
space - food, medical supplies, etc. - is
$1,000. (To put this into perspective, a
single block of butter that is in your
kitchen right now is 1 lb.) Designers
must do all they can to keep payload
weight down. This is primarily achieved
by swapping out raw materials for
lighter ones, such as high-strength
7075 forged aluminum in place of steel
and designing components as compactly
as possible.
Next, service life: Unless it is a rocket
being used for a joyride into space, most
systems sent up are intended to stay in
the atmosphere for more than 24 hours
- think satellites, the International
Space Station, and the Mars Rover - so
they must be designed with a long service
life in mind. Designers should
include high-quality parts that have
extensive cycle tests to withstand many
modulations and constant operation
over years or even decades. In addition,
for eventual human-crewed long-haul
space voyages, vital components should
be designed to be easily swapped out
with a spare, without having to dissect
and disassemble the entire system in
which it resides.
Finally, batteries: Electricity in space
is generated from a single source that is
consistently available - solar power via
the Sun. Like on Earth, this is collected
via solar panels and is stored in a normal,
albeit large, battery. These systems
do not have an infinite lifespan. Solar
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ADT Feature 1 Military Space Technology 0622_1.indd 6 Intro
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panels crack, and batteries eventually
refuse to hold a charge.
Designers should consider using
mechanically operated thermostatic
valves in their temperature regulation
systems to reduce strain on critical
power supplies. These valves operate
with no power source, based solely on
thermal variations, and thus do not put
a strain on central power sources. Unlike
electrical components, thermostatic
actuators monitor and respond to temperature
variations in media such as air,
water, glycol, steam, and others.
An example of thermal actuator technology
in action would be a space vehicle
that uses a self-powered mixing
valve to regulate cabin air temperatures.
When the circulated air temperature is
below the valve's " set-point, " the internal
spool adjusts to maintain the desired
setting. This is accomplished by the
valve's internal actuator, which senses
the change and adjusts accordingly via
a phase change technology incorporated
into the thermal actuator. By utilizing
a self-contained thermal actuator
triggered by real-time and continuous
temperature variations, power needs for
cabin air temperature regulation are
eliminated, thereby reducing overall
strain on onboard batteries.
Wet And Salt-Wet
Both fresh and salt water are notorious
for quickly rusting metals and
degrading all other materials. Any product
or machinery to be used on or near
water must be designed with the damaging
effects of wet and salty conditions
in mind or risk severely shortened operating
life spans.
Saltwater's corrosiveness can be mitigated
by using the proper metals on
any water-based systems that come
directly into contact with it. Designs
should use corrosive-resistant metals
and steer away from iron, as it is especially
prone to immediate rusting.
While the use of unique, high-grade
materials that resist the effects of salt
water are often costly, their inclusion
extends operating life and reduces
maintenance rates. For example, most
boats use a sacrificial zinc anode block
(due to its low nobility on the galvanic
series chart) to counteract the effects of
Aerospace & Defense Technology, June 2022
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Aerospace & Defense Technology - June 2022

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