Bearings go on mission to Mars
Muskegon, MI -- The Phoenix Mars Lander that began scooping up samples of Martian soil June 4, 2008, uses thin-sect...
Muskegon, MI — The Phoenix Mars Lander that began scooping up samples of Martian soil June 4, 2008, uses thin-section bearings to position its robotic arm for digging in the planet’s permafrost.
This is the second Mars mission for Reali-Slim bearings, manufactured by Kaydon Corporation’s Bearings Division. The bearings were also used in the two 2004 Mars Exploration Rovers, which are still sending geologic findings back to Earth from some 171 million miles away.
The robotic arm was built by Alliance Spacesystems of Pasadena, CA 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 2.3-metre-long arm is attached to the deck of the Lander, with a garden-sized trowel on the end and a camera mounted above it that sends colour photographs of the samples to scientists on Earth.
The arm has four types of motion: up-and-down, side-to-side, back-and-forth, and rotating. Three of the joints that accomplish these movements feature sets of custom-engineered thin-section bearings from Kaydon. According to Richard Fleischner, mechanical engineering group supervisor at Alliance, they were specified for several reasons.
“The Kaydon bearings give us plenty of load capacity, even though they are lightweight and small enough to fit in the tight space,” he said. “They also have a full complement of balls to withstand the force and vibration of the launch. And we get good engineering support and a reasonable lead time from Kaydon.”
Fleischner said the bearings take a heavy load during digging, as up to 45 kg or more of force is needed to break through the ice and dig down about 50 cm. They are made of heat-treated 440C stainless steel and mechanically honed to achieve a super-fine finish and improve torque. The bearings are heated to operate in extreme cold (the joints are designed to survive in -108C) and use a low-outgassing lubricant that neither gets too viscous in extreme cold nor evaporates in the thin atmosphere.
The Phoenix Lander is expected to be on the job for three months, digging for evidence that Mars could sustain life.
The Kaydon Bearings Division, which invented the thin-section bearing in 1943, is headquartered in Muskegon, MI.