Two teams
of researchers are hoping their tiny devices will mean big leaps for future
Mars-bound humans, allowing them to carry powerful computers and generate life
support materials from the planet's atmosphere.
In one
corner, NASA-funded scientists are tweaking microtechnology to produce compact
systems that produce breathing oxygen or rocket propellant, vital components of
any manned space mission.
"We're
looking at collecting the carbon dioxide from the Martian atmosphere and breaking
it down for [crew needs]," said Batelle researcher Kriston Brooks, principal
investigator of the study at Pacific Northwest National Lab (PNNL), where NASA
has awarded a contract to develop the technology.
The goal,
Brooks added, is to wrangle microtechnology into a usable system that would
generate propellant for astronauts aboard a manned mission to Mars by 2030, a
goal set by NASA's space vision of renewing human space exploration outside
Earth orbit.
"It's all
about helping to reduce the cost of missions for robotic sample returns and
even human space missions," said NASA's Tom Simon, a systems engineer for
in-situ resource utilization at Johnson Space Center. "We're hoping that the
work will be a great kick-start for using resources on Mars to enable us to
meet our budget goals and constraints for exploration."
Meanwhile,
two Purdue University researchers are adapting microchannel heat sinks - small copper
plates lined with numerous grooves each three times the width of a human hair -
with conventional refrigeration methods to build more efficient cooling systems.
"The
microchannel heat sinks are absolutely ideal for those situations," said thermal
engineer Issam Mudawar, the study's leader and a Purdue mechanical engineering
professor, in a telephone interview. "Though our immediate target is both
computer chips and defense applications."
Setting
up shop off-planet
NASA has
set aside $13.7 million for Brooks' four-year study, which engineers hope prove
useful not just for Mars missions, but also lunar spaceflights and space station
living as well.
Using local
resources could reduce the cost of a moon or Mars mission by about 40 percent
according to NASA studies, Simon told SPACE.com, adding that lunar
resource-based technology is also under scrutiny.
"We're
hoping to be able to support by 2010 a small demo mission that not only produces
just a couple of grams of oxygen, but will also be able to tell what water is
on the moon," Simon said.
Currently carbon
dioxide collected by the space station's air scrubbers and hydrogen produced by
the station's Elektron oxygen generator are currently are dumped overboard, but
Sabatier reactors - which generate methane from carbon dioxide - could help
astronauts recover oxygen from what has to date been treated as waste gas, he
added.
Microchannel
surfing
At the
heart of Brooks and Mudawar's studies are advances with microchannels,
which have allowed researchers to squeeze chemical and thermal processes into
ever-smaller packages.
"What
really got this started is microchip technology," Brooks told SPACE.com.
"We thought, 'well, if we can make microchips so small, why can't we do the same
thing chemically.'"
With
multiple grooves separated by just 200 microns or so apart, microchannel plates
offer improved heat and mass transfer rates. Since the spaces between groove
walls are so small, the effects of gravity give way to other forces, similar to
water's capillary action, making the technology apt for space applications, the
researchers said.
"You also
have the advantage of redundancy," Brooks said, adding that the processes required
to scale up from one microchannel to a 1,000-microchannel system are simpler
than other processing methods.
For
Mudawar, the differences in fluid flow between microchannels and the more
conventional tubing used for heat sinks has allowed the development of even
smaller cooling systems for electronics.
Multifaceted
MicroCATS
In order to
produce oxygen or propellant for a spacecraft, Brooks is developing a closed-loop
system of heat exchangers, condensers, phase separators and other tools into a
working microchemical and thermal system (MicroCATS) device about one cubic
foot in size.
Once the
individual components are tested, they will be integrated into a bread
board-sized system and tested in microgravity aboard NASA's KC-135 aircraft, as
well as inside atmospheric chambers to simulate the Mars atmosphere and
temperature environment.
Brooks
hopes the test will lead to a final setup, known as an In-Situ Propellant
Production system (ISPP), that could sit outside a spacecraft on the Martian
surface, absorbing carbon dioxide, then heating it up and passing it through a
series of small reactors to separate the gas into methane and water, which is
ultimately broken down into oxygen and hydrogen.
"Our goal
is to be about one-third the weight of conventional systems," Brooks said. "Hopefully,
we'd be able to catch a ride on a mission that's going to Mars and people can
test this out."
The oxygen
and methane can be cryogenically stored in separate tanks - possibly even the
same ones used to hold fuel for the trip to Mars - and later be used as propellant,
Brooks said, adding that the system could also bolster life support as well.
"For
example, on a space suit you could use it to collect carbon dioxide and
regenerate it into oxygen," Brooks said. "What they do now aboard the space
station is collect the carbon dioxide, absorb it then replace the [scrubbers]...we
need to be able to close the loop on life support."
Building
a cooler system
At Purdue
University, Mudawar and doctoral student Jaeson Lee have already demonstrated
the potential of their microchannel heat sinks.
"We really
have a working system now," said Mudawar, whose study is funded by the U.S.
Office of Naval Research.
Two research
papers based on the work appeared in a recent edition of the International
Journal of Heat and Mass. Mudawar has also tested past heat sinks aboard
NASA's KC-135 aircraft in weightless experiments for a variety of space systems.
Mudawar and
Lee were able to successfully use a one-inch square copper microchannel plate
to serve the same evaporative cooling function as the one-meter long tubing
used in a refrigerator. "The issue now is going to be packaging the cooling system
around the device."
While Mudawar's
heat sink still requires a refrigerant to function - the researchers used
R134a, which is found in household refrigerators and air conditioners - it offers
much higher performance than conventional fans or dissipation metal fins. Future
military weapons systems, such as advanced lasers, may require heat sinks capable
of dissipating up to 10,000 watts per centimeter that current methods may not
be able to handle efficiently.
"We were
very satisfied with this technology," Mudawar said.