Note that the fine step mode has a maximum total range much smaller than the overall range, since it uses the flexure system to add a fine displacement on top of the coarse one. Therefore they have to use the coarse adjustment to get it close, and then use the fine adjustment the rest of the way. According to the doc, the fine adjustment has a max displacement of 8 microns. By my math, the coarse actuator has a resolution of about 0.06 microns; plenty to get within range of the fine actuation.
Well, but, they weren’t even doing that. If it’s the modulus per density thing they actually meant, that’s still not strength. Eggshells are nowhere near as strong as nylon rope, but they have much higher modulus.
Kind of an interesting milestone: JWST distance to L2 orbit is now less than the circumference of the earth. Its speed, however, is now in the range of a late 1950s turboprop airliner.
Wake me up when it has the speed of an unladen swallow.
African or European?
Watched a video— Be was chosen because it is light, stiff, and thermally stable.
Brian
I haven’t watched that video yet, but beryllium
was also used in the Spitzer Space
Telescope – due to its strength and light weight.
Looks like the L2 Insertion is planned for sometime Monday. That will be something to follow in the news! Sounds kind of pornographic to me.
Beryllium, Lagrange points; it’s all coming together, Isaac!
Something very strange just happened. The distance to L2 orbit was showing as less than 5000 miles earlier this morning, and the graph showed the JWST almost at the L2 orbital insertion point. Now the distance suddenly updated to over 16,000 miles and the JWST is showing as farther away, and the timeline now has a “Day 30” (which is tomorrow). Apparently the estimated tracking data on the website was wrong.
That video isn’t great. Narrator says “It is super light weight!” when what she means is that beryllium’s density is low. And - as the comments note - no mention is made of its toxicity, which deserves at least passing mention.
Not the words I most wanted to read this morning in connection with the JWST…
I trust that this is the explanation.
The distance numbers are not real-time readings, but based on precalculated flight data. Somehow the website had inaccurate numbers. I don’t think the “distance from earth” number changed, I think what changed was the “distance to L2” number, the distance complete percentage, and the graph.
I’m guessing that maybe what someone setting up the website got wrong was the total distance the JWST had to travel. I suspect perhaps they used the distance to L2 rather than the distance to the orbital insertion point. The JWST halo orbit will be very large and the insertion point is quite far from the actual L2.
Yes, the orbit has a diameter of the order of half a million kilometers, it’s not as though they were aiming at a point. Who knows what exactly it’s counting down to - insertion burn point? That must surely be recalculated to get it precisely correct.
Or we found a wormhole.
Don’t lick the JWST should go without saying.
If you’re going to make such a nitpick - in fact I think what matters is the strength of Beryllium for a given weight. I don’t see how low density is an advantage - quite the opposite, in fact.
Well, certainly, this is what I figured when I first heard of JWST’s mirrors. Also Be has a thermal conductivity similar to aluminum (IIRC) which means a given heat flux hitting only parts of a Be component will drive smaller temperature differences over the component, and I imagine that helps too.
Like I say, its stiffness to density ratio is six times that of steel. I’d be intrigued to have a bell made of beryllium because it would ring at such a high pitch (though if you look for beryllium bells online, you find a huge number of brass musical instruments that have what they call a “beryllium bell” which is not made of beryllium and not even clearly made of an alloy that contains some beryllium). I do have some small pieces of beryllium, and they’re certainly low density, but they’re little blobs whose stiffness isn’t at all apparent when handling them. I also have a bar of beryllium copper which is, I think, 3% Be.
Beryllium is awfully toxic as an airborne powder during grinding operations, or as a fume in smelting. I think it’s safe to handle as metal parts, at least if you don’t have open sores that you rub the part into, but it’s hard to get an accurate read on this. Tools made of beryllium copper alloys don’t get any special handling. The person holding a piece wearing gloves, goggles, and a mask seems to be outlandish.
I was struck more by the howler of an error that NASA’s public facing web site contained.
As an electronicker I’ve worked with beryllium oxide ceramic heat sink ceramics and grease but not the metal. It is highly insulative, heat conducting, and stable at high temperatures, perfect for the job.
The ceramic pieces were pre-formed and required no machining or drilling so were deemed safe. After handling the grease or even the tube it came in I’d thoroughly wash my hands. It would be applied between the semiconductor piece, most frequently a TO-3 package, to maximize the surface contact with the actual heat sink and could be counted on to stay in place.
Now you tell me!?
Just did a double take on this… you mean electrical insulator and heat conductor, right?