Astronauts no longer need to find fridge space for both
drinks and experiments, after a sample-filled freezer on the International Space
Station made its return trip to Earth on the shuttle Discovery last week.
The cryogenic freezer can typically maintain a
temperature of -160 degrees C (-256 degrees F) and support up to 22 pounds of
research samples. And for the first time, it provides serious cooling for such
samples during trips to and from the
space station.
"It has achieved -160 [degrees C] during performance
testing pre flight," said David Ray, a project manager for the General
Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) at the
University of Alabama at Birmingham.
Ray added that GLACIER only needed to maintain -95
degrees C (-139 degrees F) for the samples that returned with Discovery, well
within the unit's capabilities.
Discovery landed Saturday after a 13-day mission that
delivered new solar wings to the space station. Packed inside its GLACIER
freezer were about 75 vials of blood samples and cell cultures representing
some five months of experiments by astronauts aboard the space station.
Cold science
The first GLACIER freezers launched on space shuttle
Endeavour last November, with one ending up installed on the space station and
one carrying back biological samples on the shuttle. Astronauts took advantage
of their new hardware by repurposing a smaller, older fridge to cool
their drinks for the first time in eight years on the orbiting lab.
Discovery's crew members carried a third GLACIER to the
space station to replace the first freezer, which has now made the trip home.
GLACIER joined several other cold storage units, including
the Minus
Eighty-degree Laboratory Freezer (MELFI) on the space station and the
Microgravity Experiment Research Locker/Incubator (MERLIN).
However, GLACIER came with new features for both the
space shuttle and International
Space Station (ISS), particularly the ability to carry frozen samples back
to Earth. The older MELFI refrigerator cannot provide powered cooling on the
shuttle's middeck, whereas GLACIER can operate within the middeck size
constraints. And the MERLIN fridge can only achieve 4 degrees C (39 degrees F)
on the shuttle middeck.
"It was difficult to design a payload that would
meet the sample requirements for temperature, volume and weight while remaining
within dimensional envelope of a double middeck locker equivalent," Ray noted.
GLACIER is less than two feet long on all sides, while
MELFI stands at a height closer to that of household refrigerators. MERLIN sits
at roughly half the size of GLACIER, but with lesser cooling capacity.
GLACIER's design incorporates two insulated door layers
to keep its contents cold, with its inner door divided into four
insulated compartments that provide easy access for astronauts. It can also
operate in either fridge or freezer modes, with a range of 4 degrees C (39
degrees F) all the way down to -185 degrees C (-301 degrees F).
Priceless samples
Astronauts check GLACIER twice daily when it is riding on
a space shuttle, but otherwise Mission Control can keep an eye on how things
are running by watching telemetry beamed down to Earth.
"While aboard the ISS, GLACIER health and status
telemetry is monitored continuously at the [NASA] Huntsville Operations Support
Center," Ray said. He added that control centers at NASA's Johnson Space
Center in Houston and the University of Alabama at Birmingham also keep watch.
Such careful monitoring reflects the
"priceless" nature of frozen samples from microgravity experiments
that now have a way to return to Earth, said Julie Robinson, NASA's station
program scientist.
"Pretty much now every flight we're bringing home a
large number of samples," Robinson told SPACE.com. "We
often have bins of frozen storage that are coming home and they may have two or
three experiments in one freezer."
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