Bearings for a Martian Scooper
The robotic arm used by the Phoenix Mars Lander to scoop up samples of Martian soil employs thin-section bearings in its key positioning joints to keep down weight whi le managing appreciable loads.
The robot ic arm
was built by Alliance
Spacesystems of Pasadena,
Calif., for NASA’s
Jet Propulsion Laboratory.
It is designed to
trench the surface, pick
up soil and ice samples,
and deposit them in the
Lander’s instruments
for testing (electrochemistry,
conductivity,
and thermal analysis).
The 7-ft, 7-in. arm attaches
to the deck of the
Lander and has a garden-
sized trowel on its
end. A camera mounted
above the trowel sends
color photographs of
the samples to scientists
on Earth.
The arm has four types of motion: up-and-down, side-to-side, backand-
forth, and rotational. Three of the joints for these movements
use sets of custom-engineered Reali-Slim thin-section bearings from
Kaydon Corp. Bearings Div. Used partly because they are lightweight
and small enough to fit in the tight space, the bearings take a heavy
load during digging, as up to 100 lb or more of force is needed to break
through the ice and dig down about 20 in. They are made of heattreated
440C stainless steel and mechanically honed for a superfine
finish. The bearings are heated to operate in extreme cold (the joints
are designed to survive in –108°C) and use a low-outgassing lubricant
that neither gets too viscous in extreme cold nor evaporates in the thin
atmosphere, according to Kaydon officials.
The Phoenix Lander is expected to be on the job for three months,
digging for evidence that Mars could sustain life. This is the second
Mars mission for Reali-Slim bearings. They were also used in the two
2004 Mars Exploration Rovers, which are still sending geologic findings
back to Earth.
Make Contact
Kaydon Corp. Bearings Div.
kaydon.com