750K views · Feb 7, 2022 · 11:07 · 4 HN recommenders · 6 mentions · discussed 2022–2026
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.
Why Hacker News points people here: Commenters repeatedly recommend it in JWST threads as a great explanation of clever mechanical design that is accurate and long lasting.
“I highly recommend”HN comment, 2022
“I highly recommend”
Explains JWST flexure actuators with a 3D-printed replica
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.
“Here a nice video that explains the mechanism that aligns each mirror”
Explains how one motor aligns each JWST mirror segment
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.
“It's a great watch and shows how well thought out design can produce accurate and long lasting parts.”
Shows how JWST actuators achieve accuracy and longevity
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.
“It's a great watch.”
Explains how JWST actuators work
This video this video was posted here link about how the actuators work on the James Webb telescope. It's a great watch.
“there's a great youtube video explaining how the actuators to align the James Webb mirrors work”
Explains JWST mirror actuators and offers a 3D printable version
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 printable version of them: link "This is a replica of JWST's mirror actuators. Six of these actuators are paired into a hexapod / stewart platform arrangement and used to control 6 degrees of freedom of each mirror segment (tip, tilt, roll, x, y, z translation)."
“Reminds me of the JWST actuators which also”
JWST actuators overload a single axis for coarse and fine control
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
