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the thermal energy storage or test
experiments will fly aboard the space
shuttle Columbia as part of NASA's
office of aeronautics and space
technology to carrier during the STS 62
mission rolled engineers at the NASA
Lewis Research Center are conducting
materials research that will lead to the
development of the next generation of
power systems for future spacecraft
fluoride salts have been selected as
test material mainly because they melt
and freeze at the high temperatures
required for effective use in a
space-based power system however a
primary concern with fluorides
is the change in volume as much as 30%
when the test material is melted this
change in volume produces a void or
bubble when the material freezes how
these voids behave under microgravity is
not entirely understood suppose that
when the salt freezes and contracts at
zero gravity the void all forms near the
surface of the container
as we move from shade to sunlight there
is no salt to conduct the heat away from
the container surface at this point the
container may be subjected to
temperatures high enough to burn a hole
on the other hand what happens if the
void forms near the center of the
container away from the surface since
the salt nears the surface will melt
first will there be enough room in the
container to allow for the expansion of
the salts from solid to liquid if not
the containers may be distorted again
hampering the entire system Oak Ridge
National Laboratory in Tennessee has
developed a three-dimensional program to
describe in space void behavior in
fluoride salts the program is named nor
vex the nor vex called predictions for
lithium fluoride salt behavior in space
must be verified with data such data at
the present time does not exist the test
experiments have been developed to
provide the low gravity data needed to
verify the Norwex code a validated
Norwex code will help lead to future
solar dynamic power systems
higher efficiency longer life and
reduced weight to separate test
experiments we'll fly aboard Columbia
they are identical except for the
composition of the fluoride salts
the experiment section has a cylindrical
canister charged with the test material
a to zone heater surrounds the cannister
the fluoride salts are melted here on
earth and allowed to solidify with the
cannister in a horizontal position
this causes a void to be located along
the canister wall at a position which is
opposite the high temperature zone of
the heater in the microgravity
environment of space the test material
will be subjected to four melt freeze
cycles the acquired on-orbit data along
with post flight data will determine the
extent of the void movement toward the
high-temperature heater zone the data
will validate analytical predictions
from the nor vex code the verified code
will help lead to improved heat receiver
designs for future solar dynamic power
systems the thermal energy storage
experiments are the first time these
materials will be tested under extended
microgravity conditions the acquired
data is needed to verify analytical
predictions for test material behavior
these test experiments will point the
way toward a reliable efficient and
low-cost solar dynamic power system for
Earth orbiting spacecraft