Astronomy

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baseline Europa mission. Louisiana State
University is working on several projects,
including the Sub-glacial Polar Ice
Navigation, Descent, and Lake
Exploration (SPINDLE). The autonomous
cryobot melts through dense ice to
explore the lake below. Plans call for
SPINDLE to deploy a second-stage probe,
called a hovering autonomous underwater
vehicle (HAUV), into the water. Another
LSU probe design, the Environmentally
Non-Disturbing Under-ice Robotic
Antarctic Explorer (ENDURANCE), can
travel untethered under ice and create
three-dimensional maps of its underwater
surroundings. The probe can obtain sam-
ples of microbes, and it has already done
so in an 80-foot-deep (25 meters) frozen
lake in Wisconsin. Designers plan to soon
send it to its next stop: a permanently ice-
covered lake in Antarctica.

Why a submarine?

After f lyby and orbital missions, the first

surface probes to Europa will probably be

stationary landers, perhaps outfitted with

coring devices to sample the shallow

ice. It’s a good start, but the chances of

finding extant microbial life on Europa’s

surface, or even within the first 10 feet

(3 meters), are slim, given the radiation

environment. “But if you can get through

to the ocean,” says Stone, “that’s a whole

different story.”

Stone’s cosmic hot-dog robot — or

any other probe type — will follow a

general four-step itinerary on its mari-

time journey:

Phase One: Getting into the ice. This

problem has been approached using a

variety of solutions, all with limitations.

Phase Two: The cruise. The entry

borehole closes behind the descending

probe as vapor pressure builds above.

Phase Three: Obstacle avoidance.

Meteoritic impact debris that has worked

its way down to random locations,

or dense brine deposits, could end

the mission.

Phase Four: Breakthrough.

The probe delivers the submarine to the

sea. As the submarine hits the ocean,

how does it deploy? How does it

communicate?

One of the most efficient ways to cut

through the ice in a place like Earth’s

polar caps is a hot water jet. The design is

simple: Heat hot water in a diesel-fired

burner, pump it down a hose to a

weighted nozzle, and let the water jet out

just short of boiling. “It cuts through ice

like butter,” Stone says. This has been

done successfully in Antarctica, but there

is a problem: It takes 1,000 metric tons of

Stone Aerospace

recently sent a

team to Alaska

to test VALKYRIE,

an ice-penetrating,

submersible robot.

Engineers are

exploring these

“cr yobots” to

determine if they

could bore through

Europa’s thick

ice crust to the

liquid ocean below.

This is an artist’s

concept of one

such cryobot. NASA