Also consider that the mirrors on James Webb space telescope need to account for both deformation from gravity when they are manufactured but also that they are manufactured at room temperature and will be operated at cryo temperatures. But JWST is also special since they have actuators to put stress on the mirror segments to be able to reshape them slightly on-orbit to focus.
(He also worked on the TEAL AMBER and TEAL BLUE satellite surveillance systems, and probably others that he never even talked about.)
Having gone to school in LA where, at the time, ALL of the EE jobs were in the Defense sector, I specifically moved up to the Bay Area to work on cool stuff I could actually talk about with others[1].
One thing of note is that ageism is MUCH less of an issue in jobs that require security clearances. So a number of engineers who are suddenly perceived as "too old" to contribute to the latest hot startup find themselves recruited by the Raytheons and General Dynamics type companies that recognize their skills are valuable.
[1] As an new college grad [NCG] I was not yet aware of the myriad ways in which employers would use non-disclosure agreements to thwart such conversations.
it's sad to me that most SV focus now is about how to sell more stuff to people whether that's through direct advertising or creating "social" platforms where people get to "influence" you into buying something or paying for something
Some congressmen had not heard of this technology and were working to fund a completely different (iirc, civilian) program intending to develop essentially the same capabilities. They had to go give a few TS briefings to the congressmen to dissuade them from writing the redundant funding into the next defense spending bill.
I make telescope mirrors.
This problem was well understood since the time of Herschel. We just have better solutions now.
The fact that this is a space scope is irrelevant to the fact that gravity will cause issues. For any telescope, you have to account for differences in the way the mirror is deformed in manufacturing vs in actual usage, and the ways the deformation will change in usage as the scope is leaning at different angles. That is always a thing.
What is particular to the Hubble is that the load in usage is zero (which is unusual), so you have to think about it that way in manufacture. But deformations in manufacture are always an issue you have to account for somehow.
Look at it this way: there is an ideal shape that the mirror needs to have, usually a revolution surface of some conic section (parabola, hyperbola, ellipse, circle). The performance of the mirror will track the difference between the ideal surface and the actual mirror. The error allowance depends on the wavelength λ of the observed radiation.
Telescopes where the error is greater than λ/4 just suck, and are unusable. Good performance begins around λ/8. A great mirror may do better than λ/20.
For visible light, λ/4 is 100 nm, or 0.1 microns. That's 10 thousand times less than 1 mm. On that scale, the mirror is made of jelly. If you put it on a rough surface, it will deform. If you put your thumb on it, hold it for a minute so it heats up from your skin, then pull away, there will be a "mountain" left behind on the mirror, under your thumb, until it cools off again.
In many cases, the support structures for large mirrors are complex mechanisms that ensure the force is uniformly distributed across a large number of points on the back of the mirror. Even amateur telescopes built using the Dobsonian template use passive self-balancing support with 3, 6, 9, 18, or even more points, depending on the size / thickness ratio.
Telescope mirrors might be a nice setting for teaching a lot of interwoven physics and material science stories.
A lot of engineering is like that. I wonder how we might start systematically collecting and organizing such stories, for eventual use in education?
The phenomena are pretty intricate. E.g. in the initial stages, grinding the mirror is a physical process: you use some very hard material to carve the glass into the desired shape.
But when it gets to polishing (smoothing the surface to optical perfection), it's far more complex. The granules of the agent are microscopic, and the process is in that grey area between physics and chemistry. You end up slicing off only a few layers of molecules at each pass.
It goes on and on like this. It's very addictive if you like Physics. :)
And given a firm grasp of size, and of atoms, it might perhaps be possible to support an integrated and broad modern material science foundation. Maybe... but I'm not being very successful at finding opportunities for exploratory discussion of that. :/
It seems like it could be great fun though.
[1] a couple of old test videos https://twitter.com/mncharity/status/1377384282633596935
I think a simple way to explain what your grandfather should feel proud of, is they documented the construction process so thoroughly that they were able to _precisely_ figure out what they did wrong, and fix it, on their first try!
https://en.wikipedia.org/wiki/Hubble_Space_Telescope#Origin_...
For some reason I had thought this (gravity stuff) was the problem. What was the actual problem?
I wonder how often retired NASA engineers are consulted. Imagine as an Engineer having to troubleshoot something which launched into space before you were born.
Of course there must be perfect documentation, SOP along with replicas on land.
One thing he would point out, that I never see discussed, was that at the time they built the mirror, there was an expectation that it may not be perfect, on account of how the Earth's gravity would slightly deform the mirror during manufacturing. As he tells the story, they'd tried to factor that into the design, but had less confidence in it. This, of course, was not the reason for the eventual problems, but to illustrate that this kind of thing was understood.
The big picture of the failure relates to the Shuttle program as well. At the time Hubble was being developed, its mission was supposed to allow for a lot more around the "shuttle" aspect: not just that it could be reused, but that it could be reused in an actual shuttling capacity, like an orbital pickup truck. So it was supposed to be possible to bring the telescope up into orbit (away from gravitational stresses), see how it worked, and if necessary, bring it back down for corrections. Since the end result of the Shuttle design cut down significantly in its capabilities in this regard, the Hubble program was left without its "Plan B".