INL’s Center for Space Nuclear Research designed nuclear-powered “hoppers” that could be more efficient than rovers — a few dozen could map the entire Martian surface in just a few years. |
INL’s
Center for Space Nuclear Research designed nuclear-powered “hoppers”
that could be more efficient than rovers—a few dozen could map the
entire Martian surface in just a few years.
Future
Mars surface missions could cover more ground with a platform that can
hop great distances in the planet’s thin atmosphere and weak gravity.
Since summer 2009, researchers and student fellows at the Center for Space Nuclear Research at DOE’s Idaho National Laboratory have been fleshing out designs for a nuclear-powered Mars hopper that can examine one Martian site, jump to another, and repeat, hundreds of times.
One hopper design is about as big and heavy as an adult emperor penguin and capable of traveling almost 200 times as far as twin Mars rovers Spirit and Opportunity did in their first five years on Mars.
The
lean, long-lived hoppers are designed to wring as much science and
exploration as possible out of every ounce. They don’t have to carry
fuel with them; they can suck up the carbon-dioxide-rich Martian
atmosphere and use it as a propellant. On cue, stored heat from a
radioisotope power source hits the propellant and rockets the hopper in
an arcing path toward its next landing site.
The
CSNR Mars hopper team has generated a variety of hopper designs
tailored to transport different payloads. The payloads range in size
from 10 kilograms to about 200 kg, the
mass of either Spirit or Opportunity with a big dog sitting on top.
A
single rocket launch from Earth could deploy several hoppers at once. A
fleet of hoppers could collect Martian rock and dust samples at the
source and deliver them to an Earthbound rocket. The CSNR team plans to
keep its hoppers simple and deploy them in large numbers so they can
cast a wide net in a search for traces of Martian life.
Original article from Idaho National Laboratory
Fleet of INL-designed Mars hoppers could swiftly explore other worlds
By Sandra Chung, INL Research Communications Fellow
Mars is our next frontier. We’d like to know whether the Red Planet ever hosted its own life forms—and where it might be able to host human explorers. The twin Mars rovers Spirit and Opportunity
have outlasted their planned three-month lifetime and given us our
closest look yet at the Martian surface. But the solar-powered rovers
have covered only 21 miles of Martian terrain in their combined 11 years
of operation, leaving most of the surface unexplored.
Future
Mars surface missions could cover more ground with a platform that can
hop great distances in the planet’s thin atmosphere and weak gravity.
Since summer 2009, researchers and student fellows at the Center for Space Nuclear Research at Idaho National Laboratory
have been fleshing out designs for a nuclear-powered Mars hopper that
can examine one Martian site, jump to another, and repeat, hundreds of
times.
“We’ve
got a little guy that we think can hop about 15 kilometers [more than 9
miles] every five to seven days,” says Steven Howe, CSNR director. He
refers to a hopper design about as big and heavy as an adult emperor penguin and capable of traveling almost 200 times as far as both rovers did in their first five years on Mars.
The
lean, long-lived hoppers are designed to wring as much science and
exploration as possible out of every ounce. They don’t have to carry
fuel with them; they can suck up the carbon-dioxide-rich Martian
atmosphere and use it as a propellant. On cue, stored heat from a
radioisotope power source hits the propellant and rockets the hopper in
an arcing path toward its next landing site. Smaller thrusts orient the
hopper and soften its landing.
A
single rocket launch from Earth could deploy several hoppers at once. A
few dozen hoppers could map the entire Martian surface in a few years,
Howe says. Hoppers could also serve as a network of weather stations
monitoring the Martian climate and could collect a trove of air, rock
and soil samples to send back to Earth.
Nuclear-powered space travel
In space travel, every ounce counts. It costs more than $2,000
just to put a pound of payload into Earth orbit, let alone get it all
the way to Mars. Whatever we send to other planets has to be as
lightweight as possible and built to last.
The
CSNR Mars hoppers are the latest in a long line of spacecraft and
robots that rely on nuclear technology to help keep them light,
long-lived and reliable. Radioisotope Thermoelectric Generators (RTGs or “space batteries”) provided steady, lasting power to the Apollo lunar science experiments; to Voyager, Viking and Pioneer space probes; and to the Cassini spacecraft currently orbiting Saturn. The New Horizons mission now en route to Pluto and the Mars Science Laboratory scheduled to launch in November 2011 will both run on RTG power sources assembled and tested at INL for the Department of Energy.
Where there’s water, there could be life. A small, nimble hopper could get down into deep cracks in the crust and take samples. |
Unlike
solar panels, radioisotopes produce steady power even at night or when
obscured by Martian dust storms. And unlike chemical fuel, which can
burn only once, the same block of radioisotope fuel could be used to
launch a hopper over and over again and run its scientific instruments
for a decade or more.
Advanced
heat storage and transfer technologies allow the CSNR hoppers to use
their radioisotope heat source for both power and propulsion. A hopper
would run some heat from the radioisotope through a highly efficient Stirling engine
and generate electricity to power both onboard scientific instruments
and the propellant capture system. The propellant system would freeze
and concentrate Martian air into a solid form for convenient storage,
eliminating the need for the hopper to carry tanks of propellant from
Earth.
Meanwhile, a beryllium
core would store radioisotope heat. Once the hopper engine contained
enough propellant for another hop, channeling the stored heat directly
into the propellant would send the hopper soaring over the Martian
surface.
“Nuclear
energy is the enabling technology. The isotope allows you to keep doing
this for years,” says Robert O’Brien, a CSNR research scientist.
CSNR
has provided fertile collaborative grounds for researchers to refine
and expand the nuclear-thermal hopper concept that O’Brien and Howe
launched in summer 2009. The center works with other DOE labs,
universities and NASA to help find ways to put INL’s national leadership
in nuclear expertise to work for space exploration. NASA scientists and CSNR summer fellows
from around the country have put their heads together with INL
engineers to analyze hopper engines and design hopper missions to
explore other planets. Researchers from University of Idaho, Utah State
and Oregon State University are contributing to CSNR hopper research.
Howe and O’Brien also presented their hopper concept to collaborators at
the University of Leicester in the UK. They went on to describe a similar idea in the Proceedings of the Royal Society.
Leaping tall buildings in a single bound
The
CSNR Mars hopper team has generated a variety of hopper designs
tailored to transport different payloads. The payloads range in size
from 10 kilograms to about 200
kilograms, the mass of either Spirit or Opportunity with a big dog
sitting on top.
William
Taitano, an INL nuclear engineer, has calculated how much thrust each
hopper design can generate. Taitano says a mid-sized hopper, about as
heavy as an average American male, could travel five or six kilometers,
or more than three miles, in a single bound. At the peak of its leap,
the hopper would be soaring more than a kilometer over the Martian
surface—easily high enough to clear the tallest Earth building and jump in and out of Martian craters.
The
scientific community will ultimately decide what the hoppers will
carry, Howe says. While the Mars rovers employ an armada of tools such
as cameras, drills and spectrometers that allow them to photograph,
sample and analyze the Martian environment, small hoppers might only
carry one or a few tools apiece.
Howe
envisions having different universities around the world competing to
design their own hopper payloads and experiments. “You can have 10 to 20
universities from around the world, hopping around Mars,” he says.
But
Howe and his team aren’t focusing on what the hoppers will take to
Mars. They’ve put a lot more thought into what the hoppers might help
bring back.
A piece of Mars
Every
once in a while, a piece of Mars makes its way to Earth and falls to
the ground as a meteorite. At least one of them contains chemical traces and fossil-like shapes
that some scientists believe are evidence of ancient, microscopic
Martian life.Scientists can’t afford to wait for more Mars rock with
fossils in them to fall to Earth. So a mission to retrieve samples
directly from Mars has become the planetary science equivalent of
bringing home the Holy Grail.
“Everybody wants a piece of Mars,” says O’Brien.
The Mars hopper could play a key role in a sample return mission. A fleet of hoppers could collect Martian rock and dust samples at the source and deliver them to an Earthbound rocket.
The
CSNR team plans to keep its hoppers simple and deploy them in large
numbers so they can cast a wide net in their search for traces of
Martian life.
“They’re
small, they’re cheap, and therefore you can risk the nooks and
crannies,” Howe says. “If you find a crevice that might have water
coming from underneath the surface—then the hopper can get down
there.”
Where there’s water, there could be life.
Last summer’s CSNR student fellows examined the potential to use
modified hoppers to explore Jupiter’s large moon Europa. A vast ocean of
liquid water may lie beneath the moon’s thick, icy crust. Small, nimble
hoppers could get down into deep cracks in the crust and take samples
of any seawater that wells up into the cracks.
A trip to Europa
is pretty far in the future. But a functioning nuclear Mars hopper may
be much closer. INL researchers have already done extensive work on most
of the hopper technologies, including radioisotope batteries, Stirling
generators, heat transfer, and sturdy engine materials that can
withstand the sudden impacts and high temperatures associated with
hopper operations. Parts of the beryllium heat transfer core have been
manufactured and are waiting to be tested. Within two years, Howe and
his collaborators hope to take a prototype hopper engine out to the INL
desert site for a test hop.
Taitano
is looking forward to that first hop. When asked to rate the coolness
of the hopper project on a scale from 1 to 10, he didn’t hesitate to
answer: “It’s a 20.”
After collecting Martian rock and dust samples at the source, a fleet of hoppers could deliver them to an Earthbound rocket. |