MOXIE Could Help Future Rockets Launch Off Mars
NASA's Perseverance rover carries a device to convert Martian air into oxygen that, if produced on a larger scale, could be used not just for breathing, but also for fuel.
One of the hardest things about sending astronauts to Mars
will be getting them home. Launching a rocket off the surface of the Red Planet
will require industrial quantities of oxygen, a crucial part of propellant: A
crew of four would need about 55,000 pounds (25 metric tons) of it to produce
thrust from 15,000 pounds (7 metric tons) of rocket fuel.
That's a lot of
propellant. But instead of shipping all that oxygen, what if the crew could
make it out of thin (Martian) air? A first-generation oxygen generator aboard NASA's Perseverance
rover will test technology for doing exactly that.
The Mars Oxygen
In-Situ Resource Utilization Experiment, or MOXIE, is an experimental
instrument that stands apart from Perseverance's primary science. One of the
rover's main purposes is capturing returnable rock samples that could carry
signs of ancient microbial life. While Perseverance has a suite of instruments
geared toward helping achieve that goal, MOXIE is focused solely on the
engineering required for future human exploration efforts.
Since the dawn of the space age, researchers have talked
about in-situ resource utilization, or ISRU. Think of it as living off the land
and using what's available in the local environment. That includes things like finding
water ice that could be melted for use or sheltering in caves, but also
generating oxygen for rocket fuel and, of course, breathing.
Breathing is just a side benefit of MOXIE's true goal,
said Michael Hecht of the Massachusetts Institute of Technology, the
instrument's principal investigator. Rocket propellant is the heaviest
consumable resource that astronauts will need, so being able to produce oxygen
at their destination would make the first crewed trip to Mars easier, safer,
and cheaper.
"What people typically ask me is whether MOXIE is
being developed so astronauts have something to breathe," Hecht said.
"But rockets breathe hundreds of times as much oxygen as people."
Making Oxygen Requires
Heat
Mars' atmosphere poses a major challenge for human life
and rocket propellant production. It's only 1% as thick as Earth's atmosphere
and is 95% carbon dioxide.
MOXIE pulls in that air with a pump,
then uses an electrochemical process to separate two oxygen atoms from each
molecule of carbon dioxide, or CO2. As the gases flow
through the system, they are analyzed to check how much oxygen has been
produced, how pure it is, and how efficiently the system is working. All the
gases are vented back into the atmosphere after each experiment is run.
Powering this electrochemical conversion requires a lot of
heat - about 1,470 degrees Fahrenheit (800 degrees Celsius). Because of those high
temperatures, MOXIE, which is a little larger than a toaster, features a
variety of heat-tolerant materials. Special 3D-printed
nickel alloy parts help distribute the heat within the instrument, while
superlight insulation called aerogel minimizes
the power needed to keep it at operating temperatures. The outside of MOXIE is
coated in a thin layer of gold, which is an excellent reflector of infrared
heat and keeps those blistering temperatures from radiating into other parts of
Perseverance.
"MOXIE is designed to make about 6 to 10 grams of
oxygen per hour - just about enough for a small dog to breathe," said Asad
Aboobaker, a MOXIE systems engineer at NASA's Jet Propulsion Laboratory in
Southern California. "A full-scale system geared to make (propellant for
the flight home) would need to scale up oxygen production by about 200 times
what MOXIE will create."
The Future Martians
Hecht estimates that a full-scale
MOXIE system on Mars might be a bit larger than a household stove and weigh
around 2,200 pounds (1,000 kilograms) - almost as much as Perseverance itself.
Work is ongoing to develop a prototype for one in the near future.
The team expects to run MOXIE about 10 times over the
course of one Mars year (two Earth years), allowing them to watch how well it
works in varying seasons. The results will inform the design of future oxygen
generators.
"The
commitment to developing MOXIE shows that NASA is serious about this,"
Hecht said. "MOXIE isn't the complete answer, but it's a critical piece of
it. If successful, it will show that future astronauts can rely on this
technology to help get them home safely from Mars."
More About the Mission
A key objective for Perseverance's mission on Mars is astrobiology, including the search
for signs of ancient microbial life. The rover will characterize the planet's
geology and past climate, pave the way for human exploration of the Red Planet,
and be the first mission to collect and cache Martian rock and regolith (broken
rock and dust).
Subsequent missions, currently under consideration by NASA
in cooperation with ESA (the European Space Agency), would send spacecraft to
Mars to collect these cached samples from the surface and return them to Earth
for in-depth analysis.
The Mars 2020 mission is part of a larger program that
includes missions to the Moon as a way to prepare for human exploration of the
Red Planet. Charged with returning astronauts to the Moon by 2024, NASA will
establish a sustained human presence on and around the Moon by 2028 through
NASA's Artemis lunar
exploration plans.
JPL, which is managed for NASA by Caltech in Pasadena,
California, built and manages operations of the Perseverance rover.
For more about Perseverance:
mars.nasa.gov/mars2020/
nasa.gov/perseverance
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