MER Status Report Week Ending November 30, 2002

We’ve just made our last major design decision, and now our RATs have
teeth. We settled most of the design details for our Rock Abrasion
Tool (RAT) a long time ago. In fact, the two flight RATs are built,
tested, and at JPL. But we’ve left one thing open for a long time,
and that’s the exact design of the “business end” of the RAT… the
grinding heads that will actually contact the rock and grind their
way into it.

We’ve known pretty much since the start that we were going to make
the grinding heads using diamonds, since diamonds are the hardest
materials we can possibly use. But finding the best way to use
diamonds has been a very long research project. (“Diamonds are
forever”, as we put it.) We’ve tried grinding heads encrusted with
tiny diamonds. We’ve tried big single diamonds. We’ve tried diamonds
coated with nickel. All of these have worked, but they don’t all work
equally well. We have no idea how hard martian rocks are going to be,
so we have to find the material that works the very best.

And now we seem to have found it. The best grinding heads of all have
been ones that are made of a hard resin with lots of fine diamond
grit mixed in with it. The great thing about these bits is that they
sharpen themselves. Even diamonds wear out after awhile. But the way
this resin works, it’s strong enough to hold the diamonds in place
only for awhile. Then, after they’ve been used awhile the worn
diamonds pull out and the resin wears away… exposing fresh, sharp
diamonds underneath. After a lot of testing, we’ve built about a
dozen of these bits, and we’ve now shipped them out to JPL to go into
the two flight RATs.