Mars 2020 Launch Locks

If you had to send a delicate piece of space hardware to Mars, you would want some launch locks. It's a rough ride at both ends and the hardware has to work afterward. I've done them for a couple missions now. The principles are pretty simple but it can be tricky fitting them into a design because you get to the party late and there's not a lot of room.

The mission launched on 7-30-2020 and landed succesfuly at Jezero Crater on 2-18-2021. We were all thrilled to know that our stuff got there in one piece, but finding out if our arm was working took weeks. You might imagine that Mission Control room at JPL... "Waiting for confirmation of DCS telemetry Delta Golf Whiskey Fifty Six on Maxar's SHA arm... Telemetry confirmed! The SHA arm works, and that means if you have parts on it, your stuff works! Yay Maxar!"

It was more like 2012 all over again:
"Did you hear anything from the Cog E?"
"No."
"Well, she's probably really busy."
"Yeah. Hey. Here's a picture in the news of our 2012 arm taking a picture of our 2020 arm."
"Yeah. Looks like it's deployed."
"Yeah. I guess your launch locks work."
"Looks that way. Looks like your Z stage works, too."
"You going to lunch?"

The Design
This arm had launch locks for the linear Z stage and at the end of the forearm. It was difficult because JPL required us to use NEA-9100 releases. I needed a pin puller, but the 9100s are pin let go-ers. It was also an extremely tight design space. Instead of cables this one had arms and pivots and bellcranks and friction everywhere.
Of course I overengineered it. These were mission critical. It turned out the main springs would operate even if the trigger spring wasn't used. JPL asked what the margin was on the trigger. "Once you let it go, it's self propelled. So the margin is infinite." Well, that answer wasn't going to do. They understood the design and came back with a request for me to determine the friction coefficient where the margin met their requirements. One more spreadsheet, one more powerpoint, and I was done.

Update:
JPL has finally put their Mars 2020 Adaptive Caching Assembly out there for all to see, so you get to see it here. It's a bottling factory in the front belly of the rover and our stout little SHA arm is the conveyor belt.