NASA hooked on commercial shuttle robots
Replace John Glenn with a robot? That might seem far-fetched today. But NASA wants to use more robots aboard spacecraft in the not-too-distant future, and it's testing candidates now. The Mars Pathfinder proved last summer that robots built with off-the-shelf computer equipment could accomplish successful space missions, opening the floodgates for a new generation of NASA robots--including Ranger, Pathfinder's likely successor.
Replace John Glenn with a robot? That might seem far-fetched today. But NASA wants to
use more robots aboard spacecraft in the not-too-distant future, and it's testing
candidates now.
The Mars Pathfinder proved last summer that robots built with off-the-shelf computer
equipment could accomplish successful space missions, opening the floodgates for a new
generation of NASA robots--including Ranger, Pathfinder's likely successor.
"For the Ranger robot, the question is not what components are off-the-shelf, but
what components aren't," said Dave Akin, director of the University of Maryland's
Space Systems Laboratory, where new NASA robots get their first workouts. "Almost
everything in Ranger is a commercial component."
Ranger is poised to become NASA's next big star. NASA and University of Maryland
scientists are putting the robot through its paces at the Neutral Buoyancy Laboratory in
College Park, Md.
To simulate zero gravity, the lab uses a circular pool that runs 25 feet deep and 50
feet across. Although not perfect, it's the closest that earthbound scientists can get to
weightlessness.
NASA wants to use Ranger on the space shuttle as part of an experiment to test how well
robots and humans interact.
The space agency will use the test results to design maintenance robots and other
complex robotic creations for the International Space Station.
Ranger is scheduled to fly with the shuttle sometime in early 2000.
Ranger is about 10 feet across; most of its bulk is from propellers and motors that
help it navigate underwater.
Eighty percent of the bulk will be removed for the robot's space mission, for which it
will use a single leg to propel itself in zero gravity.
From the ground up, Ranger is chock-full of commercial components. There are 17 386
processors in its arms alone. Each processor controls a specific joint and is more
advanced than the 286 processor that was Pathfinder's main brain.
So far, Ranger has cost NASA $6 million, about one-fifth of what it spent to develop
Pathfinder.
Aboard the space shuttle, Ranger will be connected to a 10Base-T Ethernet cable. The
connection will let astronauts control the robot's actions in real time. To simulate the
connection back at the lab, a long, orange umbilicallike cord dips into the water and is
pulled behind Ranger as it swims around the pool.
On the shuttle flight, a Silicon Graphics Inc. O2 workstation will accompany Ranger as
its control interface. SGI officials said the workstation is priced at about $5,000 and
will be the first uncustomized SGI machine in space.
Ground technicians will also be able to control Ranger, giving astronauts in space a
backup pair of hands. Ranger is one of the first NASA robots with mechanical hands that
can do maintenance work in space.
Ranger uses a standard TCP/IP connection to communicate with technicians on the ground.
It can simultaneously handle tasks for different users, but lab managers said that's
unlikely to happen during a shuttle flight because it is a NASA policy breach.
Ranger's handlers on the ground will experience a communications delay of at least
three seconds. Although the 128-kilobit/sec connection between Earth and space would be
fast on the ground, the distance the data must travel causes a delay.
Because the flight controllers use virtual reality software running on five SGI Indigo
2 machines to command the robot, any delay will be awkward, the Ranger R&D officials
said. But the software helps them compensate.
"On the ground control stations, a ghost image will show where controllers just
told the robot to move," lab research assistant Phil Churchill said. "Then the
real image will catch up as the robot does in space."
Ranger will do well in space despite being almost completely designed with commercial
parts, Akin said.
Akin, an aerospace engineer, said he can remember the days when all hardware and
software was built to custom specifications.
"The big revolution was the microchip," he said. "You can do so much
more with less now. It's not like the days when we had to solder transistors
together."
But Churchill said there are problems with relying too heavily on commercial software.
"The advantage is cost and time savings," Churchill said. "But one of
the problems is incompatibility. Sometimes we tell developers what features we would like
to see in the products and they add them. Other times, they won't."
But both men agreed that space robots of the future will be built quicker and more
cheaply using commercial components. The R&D team built Ranger in just under two
years.
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