[meteorite-list] Kicking the Tires on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:05 2004
Message-ID: <200401210117.RAA20293_at_zagami.jpl.nasa.gov>

http://www.latimes.com/la-sci-rover19jan19,1,934409.story

Kicking the Tires on Mars

An auto reviewer finds rover Spirit a bit pricey -- $410 million,
with destination and delivery charges -- but enthuses it really
shines off-road.

By Dan Neil
Los Angeles Times
January 19, 2004

There is a saying in robotics: You shouldn't anthropomorphize
robots. They don't like it.

Even so, it's hard not to think of the Mars Exploration Rover Spirit
as a kind of gawky, geeky geologist moving in halting steps as it
fitfully cogitates its path to the next interesting rock. All it needs is
a pith helmet.

>From my perspective as The Times' auto reviewer, I can tell you
there is nothing human at all about Spirit.

It's a car.

Like any car, it has wheels. Yes, there are six of them, but a Ford
"dualie" pickup has that many too. It's underpowered (about 0.06
horsepower), but so are many vehicles from India.

With a top speed of about 0.1 mph, the brains of an obsolete
desktop computer and the power of two light bulbs, the rover is not
what you would call a space Ferrari.

But to the men and women of the Jet Propulsion Laboratory, it's a
screaming hot rod of interplanetary science.

"It's an awesome machine," said Spirit flight director Chris
Lewicki. "It's the coolest set of wheels on Mars."

There are only two places in the universe to get behind the wheel
of a rover. One is Pasadena, the other is Gusev Crater on Mars.

I opted for Pasadena, looking over the shoulder of rover operator
Scott A. Maxwell at his keyboard cockpit as he rehearsed his first
drives in the Martian countryside.

The rover is not a luxury vehicle. That's a galactic understatement.
There are no heated seats, no in-car DVD player, no tinted
windows, no refrigerated glove box. You have to buy a Saab for
that.

For a stripped-down model, it's a bit on the expensive side -
about $410 million, with destination and delivery charges to Mars.

The first problem with driving the rover is that you can't actually
drive it. Mars is far away: 100 million miles, or 8.9 light-minutes.
To send a message and get a reply takes, at best, about 20
minutes.

The delay means that Spirit, which rolled off its lander Thursday,
cannot be "joysticked," that is, controlled from the ground in real
time. The Soviet Lunakhod moon rover - a mere 3 light-seconds
from Earth - required a five-man team to tele-operate, and it was
a handful.

"That time delay really messes us up," said Brian Cooper, one of
the rover controllers.

Spirit and its twin, Opportunity (scheduled to land on Mars on
Saturday), are point-and-shoot machines. They are imbued with a
large degree of autonomy, designed with their own
decision-making software so that they may be at home on the
Martian range.

What rover operators do is throw a lawn dart icon at a
computerized map of Mars, marking the destination the science
team back at JPL has picked out. Think of it as NASA's version
of the OnStar system.

Then, using its complex terrain visualization and guidance system,
Spirit will traverse on its own to the target through a series of
"way points."

"We tell it: 'You can get to this spot, and we don't care how you
get there and we don't care what your final orientation is,' "
Cooper said.

It's kind of like driving a Hummer in Los Angeles.

The Hummer, at least, has headlights. The rover needs three sets
of black-and-white navigational cameras to see where it's going. One
set of navigation cameras is on top of a mast, and two sets of hazard
avoidance cameras are on its "bumpers."

The three-dimensional images created are processed in two ways:
human 3-D, the kind of stereoscopic images familiar from cheesy
horror movies; and machine 3-D, a swarming cloud of data points that
model the contours of the terrain.

The human 3-D images are fed into special LCD goggles - high-tech
versions of those "Night of the Living Dead" specs - that help drivers
visualize hazards on the surface.

"It looks like you are walking on Mars," Cooper said.

Maybe, but in the dim control rooms of JPL, the rover drivers in
their dark shades look like jazz musicians grooving on a cosmic melody.

But even the most data-rich terrain map can be treacherously incomplete
because Spirit cannot see behind rocks and obstacles. It's like driving
through the desert at night. The long shadows cast by rocks and brush
are analogous to the hollows of incomplete data.

"The problem is that neither the rover nor the human planners on Earth
can see very far away," said Mark Maimone, a space robotics expert at JPL.
"It sees pretty well 10 to 20 meters out, but it falls off after that."

As a result, it's easy for the rover - and its backseat drivers at JPL -
to get disoriented, as if it were navigating an unfamiliar city at night.

To keep track of its position, Spirit is equipped with an inertial
measurement unit, the same hardware that helps tell an F-16 pilot which
way is up.

"It's really quite challenging in the Mars-like terrain to keep a good
idea of your position and which way you're pointed," Maimone said.

So let me get this straight: You can't really drive it. You can't really
see out of it. It's overpriced. It's like driving a Lincoln Town Car.

Now that Spirit has rolled onto the surface, the engineers and scientists
are eager to put the pedal to the metal.

"The overwhelming feeling on the engineering team is, 'Gun it,' " Lewicki
said.

Yet even at full throttle, Spirit accelerates like a Vespa scooter
dragging a mailbox.

Spirit is powered - if that's not too much of a misnomer - by six DC
motors, about the size of C batteries, situated inside the wheels. If
controllers were indeed to "gun it," the motors' total output would be
about 0.06 horsepower.

Spirit doesn't accelerate so much as stagger toward its horizon. Its
hazard-avoidance software allows the vehicle to move forward anywhere
from an inch to a yard at a time. Then the rover stops, takes more
pictures, considers the best direction to go, takes another step and
repeats the process.

So while the rover's maximum speed is about 600 feet an hour, with the
hazard-avoidance system driving Miss Daisy, the pace is a more leisurely
120 feet an hour.

"The main thing is we don't want the vehicle to get stuck on a rock, to
get high-centered," said Maimone, who wrote the obstacle-avoidance
software. "We want to be conservative."

The one place where the rover really shines is off-road - really, really
off-road.

Land Rover Defender 90? Toyota Land Crusher? U.S. Army Recon HUMVEE with
optional TOW missile launcher? Wimps.

The fuselage of the vehicle - called the Warm Electronics Box because it
provides the temperature-controlled environment for the batteries and
instruments - is double-walled with panels of alloy honeycomb and epoxy
graphite laminate, materials that wouldn't be out of place on a Formula
One car.

Between the walls is an insulating foam called Aerogel. An array of
batteries, heaters and plutonium-powered heater units keeps the interior
temperature a toasty minus 4 degrees Fahrenheit and above.

When you look at the rover (a working version resides in the testing labs
at JPL) you can't help but marvel at its utter lack of styling. As I stand
there studying it, images of a titanium Ninja dodo bird form in my mind.

The wheels' spiral design (shades of the old ZR-1 Corvette) acts as a
spring, giving Spirit enough flexibility to withstand a drop from nearly
a foot onto a hard surface. The black coating on the outside of the wheels
is anodized aluminum, not rubber.

But the thing that really gives it off-road chops is its "rocker-bogie"
suspension, aluminum and titanium linkages that support the vehicle on its
six bowl-shaped aluminum wheels. The rockers can articulate as much as 30
degrees.

To help keep the vehicle level, a geared differential connects the left
and right sets of wheels so they act in opposition: When one set of wheels
goes up, the other goes down, effectively halving the vehicle's tilt.

If the rover's suite of accelerometers and laser gyroscopes detect the
vehicle tilting at more than 30 degrees, it will order Spirit to stop
(although its tip-over point is more like 45 degrees).

Even though it's short on horsepower, it's way long on torque.

It's tractor-like gear ratio allows it to climb over 15-inch rocks, 1 1/2
times the height of the wheels. It would be like a Hummer parking on a
Lamborghini.

"I wish I could take this thing out to the canyons and go rock climbing
with it," said Don Bickler, the engineer who created the rocker-bogie
system. "This sucker will climb a wall."

And with its four-wheel independent steering, Spirit brings new meaning
to the words parallel park, able to crab sideways into a parking space
just 5 1/2 feet wide.

And if you get in a jam, just pick it up. Spirit's curb weight is 384
pounds on Earth, but only 184 pounds on Mars.

All in all, the 2004 Mars Exploration Rover Spirit, I've decided, is a
decent enough interplanetary sport utility vehicle that makes up in
ability what it lacks in curb appeal.

As I drove away from the JPL campus in a borrowed GMC Envoy XUV behemoth,
I was already missing Spirit's geeky innocence and pluck. Oh, there I go
anthropomorphizing it.

It's a car.

Like all cars, Spirit will eventually break down. Currently it's late
summer on Mars; that gives the solar-powered rover about a four-hour
workday, when its 14 square feet of solar panels are generating about
140 watts, give or take a shadow.

As the Martian summer turns to fall, and dust collects on Spirit's solar
panels, the rover will have less and less power.

One day Spirit won't start at all. And there's no AAA on Mars.
Received on Tue 20 Jan 2004 08:17:49 PM PST