When the Space X23 rocket launches on August 28th to resupply the
International Space Station, it will carry two experiments designed to
sustain humans as they go farther and stay longer in deep space: A physical
science investigation known as DEvice for the study of Critical Liquids and
Crystallization—Directional Solidification Insert-Reflight (DSI-R), and a
space biology experiment known as the Advanced Plant EXperiment-08
(APEX-08).
While DSI-R's full title may be long, its purpose is succinct: How can
material scientists make metal alloys stronger, and last longer under
various gravity conditions? The answer may lie in a series of computational
models that researchers hope to refine as a result of this experiment. Dr.
Rohit Trivedi, a senior scientist at Ames Laboratory and a professor of
materials science and engineering at Iowa State University in Ames Iowa is
the principal investigator: Dr. Alain Karma, a professor of physics at
Boston's Northeastern University is the Co Investigator. They explain what
they hope to observe and learn.
Dr.: Trivedi says, "We will be using the Device for the Study of Critical
Liquids and Crystallization (DECLIC) which allows you to actually see what
happens when a liquid alloy begins to harden to become a solid. As it does
so, it forms branched microscopic crystals known as dendrites. In a perfect
world, all the dendrites would be uniform in size and grow in the same
direction towards the hot liquid in the mold. But we know that doesn't
happen. Groups of dendrites grow in different directions leaving behind
crystal defects in the solidified material that impact its mechanical
properties. The question is then why do these casting defects occur and how
do we prevent them? The DECLIC is a wonderful scientific instrument that was
built by France's CNES. It's basically a rack mounted mini lab that allows
us to conduct experiments from the ground where we can use the Directional
Solidification Insert DSI to control key variables such as alloy
composition, which was increased for the reflight experiments (DSI-R), the
temperature gradient and solidification rate and visualize in situ how
crystals form and grow without fluid flow induced by gravity."
Dr. Karma says, "Once we make these observations and get this new data, we
can test and refine our computational models to help predict how to make
metallic alloys stronger, lighter and long lasting. This is important both
for long term space flights and here on Earth. For materials processing in
space or the lunar surface and long term space flight, we'll most likely be
using 3D printers to manufacture replacement parts for our spacecraft. In
simple terms we can take metal powders and apply a laser to them to make the
part we need. But multiple variables in the manufacturing process means
trial and error is not optimal. Instead, these new computational models will
help us narrow down the choices. We'll also use those models to tell us how
to manufacture these parts under various gravity conditions from the Moon to
Mars to deep space itself. Back on Earth, these same computational models
will help us produce superior structural metallic alloys to use in our
infrastructure projects. And remember, there are new materials yet to be
discovered—for example alloys with the capacity to operate at higher
temperatures under extreme environments. It's very exciting to participate
in the research that will lead to the discovery of these new materials."
The APEX-08 is another example of the "make it, don't take it" approach to
future space travel. Like humans, plants grown in space for consumption can
experience stress when exposed to microgravity conditions. Since compounds
known as polyamines contribute to the plant stress, APEX-08 will examine the
role these compounds play, specifically in the plant: Arabidopsis thaliana,
aka thale cress. The experiment's results may provide insights into the
mechanisms plants use to modulate the stress of microgravity.
Source: Link
Tags:
Space & Astrophysics