How to achieve nanometer precision in space?
Why Hacker News recommends it
Commenters repeatedly recommend it in JWST threads as a great explanation of clever mechanical design that is accurate and long lasting.
What it is
Breaking Taps explains how the cryogenic mirror actuators on the James Webb Space Telescope achieve nanometer precision using flexures. It shows a 3D-printed replica and how one motor handles both coarse and fine motion.
Recommended by 4 HN commenters across 3 different months, 2022 to 2026.
What Hacker News said
Strong rec infogulch · 2022-03 · on “First images from James Webb telescope exceed expectations”
The actuator is a genius flexure design that is both mechanically simple and accurate. Breaking Taps 3d-prints a working replica and describes the design. I highly recommend: [this video] The actuator breaking wasn't as concerning after seeing the design.
Recommends blenderdt · 2022-03 · on “First images from James Webb telescope exceed expectations”
Here a nice video that explains the mechanism that aligns each mirror: [this video] It is amazing that this is done with only a single motor. It works something like this: one direction of the motor sets which axis to align, the other direction sets the alignment of the chosen axis.
Recommends mywacaday · 2022-03 · on “Mars helicopter Ingenuity completes 22nd flight”
This video [this video] was posted here [LINK] about how the actuators work on the James Webb telescope. It's a great watch and shows how well thought out design can produce accurate and long lasting parts.
Recommends mywacaday · 2022-04 · on “James Webb telescope's coldest instrument reaches operating temperature”
This video [this video] was posted here [LINK] about how the actuators work on the James Webb telescope. It's a great watch.
Recommends bigiain · 2026-01 · on “The (likely?) cheapest home-made Michelson interferometer”
I have a related question, how far are you turning the thumbscrews when making adjustments? I think M3 standard thread pitch is 0.5mm, so to a first approximation that almost 1000 wavelengths (if I have the SI units right in my head, and I'm not 3 orders of magnitude out?). I suspect the left/right and up/down adjustments have as fairly high lever ratio, but I can't imagine you could successfully adjust the in/out distance with any precision (not in the 690nm sense anyway)? Is the in/out distance not important so long as the beams are aligned? Dunno if you've seen it, but there's a great youtube video explaining how the actuators to align the James Webb mirrors work: [this video] including a 3D p
Cites RicoElectrico · 2022-10 · on “Achieving 3-axes of microscopy imaging with just a motor and a linear actuator”
Clever. I wonder how the mechanical realization looks like, as I can't really wrap my head around it. Reminds me of the JWST actuators which also "overload" a single axis for coarse/fine control: [this video]