Second CMG Fails

Yes, a second control moment gyroscope failing affects my job. How? We build the carrier that takes them to orbit.

We’ve already got one carrier built and most of a second one is in our clean room. I had my [gloved] hands on it this morning, showing it to a couple NASA badges. There’s a minor mechanism question, so they wanted to see the actual hardware.

That’s a fundamental truth of flight hardware–drawings are nice, but the actual piece part is soooooo much better.

As you can see, there are four CMG’s on orbit. When all four are working everything is keen. I think two is the minimum nominal number to have running and not need to use thrusters to stay aligned.

Why is alignment a concern? Power. ISS runs on solar power, and you want your solar panels facing the sun. This means that you turn the station to keep the solar arrays pointed at the sun. If you can’t turn the station, well, then you’re out of juice, and that sucks.

How do these work? Pretty simple. Ever played with a gyroscope? Know what it’s like to turn it while it’s spinning? Yeah, you get a torque feedbacking your hand. Now when you do it on the ground, no biggie–you’re not going to move much, since your feet are on the floor. In space, when you gimbal a gyroscope, there’s nothing holding the station in attitude, so it moves in response.

These things just break. It’s they way they go.

Oh well … more work for us. Yay. The work is always good, even when it means that I’m at work at 0615 and still here at 1630. 🙂