Getting Into the Flow on the International Space Station
December 2, 2015 - 12:52 PM
HOUSTON, TX - Think about
underground water and gas as they filter through porous materials like
soil and rock beds. On Earth, gravity forces water and gas to separate
as they flow through the ground, cleaning the water and storing it in
underground pools. Gravity's role is significant in the process, both in
nature with ground water and in chemical processes such as water
How this filtering works on Earth is well understood, even when the flow
consists of different fluids. The process is still a mystery in
"There are a lot of different types of reactors," said Dr. Brian Motil,
principal investigator, PBRE, NASA's Glenn Research Center. "When you
have a single phase, just a liquid or a gas, it behaves pretty much the
same on Earth as it does in microgravity. However, when you get two
different phases, like gas-liquid where the densities are very
different, you end up with some very different behavior when you go from
the ground to space."
The Packed Bed Reactor Experiment (PBRE) is a basic science
investigation designed to fill in the missing information as to how
two-phase mixtures flow through porous media in microgravity. PBRE,
which is scheduled to launch on the next Commercial Resupply Services
mission to the International Space Station Dec. 3, could provide answers
that would help design more efficient reactors for space, particularly
for those long-duration missions like trips to Mars.
Reactors used on the space station and in space missions are critical.
Without them, life in space would not be possible. They reclaim water,
clean air, and provide many of the life-sustaining processes we take for
granted. Because of the gap in our knowledge about how two-phase
systems work in microgravity, designers don't have the necessary tools
to create more efficient systems.
"In general, what we've done at NASA is try to avoid two-phase
reactors," said Dr. Enrique Rame, project scientist, NASA Glenn. "It's a
complex problem, but we can't always avoid two-phases. Sometimes gas
bubbles come out of a solution and you end up with two phases even
though you don't want them in the reactor. That causes problems for
people who are designing water reclamation, air revitalization and those
types of systems."
PBRE will be conducted over eight weeks on the space station in the
Microgravity Science Glovebox (MSG), a self-contained, suit-case sized
lab. At 324 pounds (147 kilograms), PBRE is the heaviest and largest
experiment in the MSG to date.
While PBRE will look at hydrodynamics, it will not include any chemical reactions.
"The PBRE has the capability to provide a wide range of water and air
flows through two randomly packed test beds. The packing is 3 mm
spherical beads," said Cathy Frey, PBRE operations lead, NASA Glenn.
Using two types of beads will allow researchers to measure flow through
materials that have different levels of "wetting", a liquid's ability to
maintain contact with a surface. One test bed will be packed with a
glass beads, wetting, while the other will have non-wetting Teflon
The experiment will measure pressure and flow rates. Two high-speed,
high-resolution cameras will capture images of the flow conditions.
"After the initial testing is complete, PBRE will be available for
additional research," said Motil. "The test section and diagnostics are
replaceable to allow for any type of air-water experiment, allowing for
NASA or industry to test any type of component or subsystem."
PBRE will develop and validate scaling and design tools for future
two-phase reactors in microgravity. It will also identify strategies to
recover single-phase packed beds from undesired gas bubbles. Results
from this experiment may lead to the ability to operate reactors in
space at greater efficiency than we can on Earth, thus benefiting future
deep space missions.
You don't have permmission to comment, or comments have been turned off for this article.