A very large parabolic dish will focus sunlight into a point too hot to be collimated into a beam using current means as any lens will be vaporized, but...

...what if the reflector itself could create a series of focal lines or rings to keep heat below temperatures that will melt a glass lens?

I am picturing a spinning pool of mercury. Given a constant rate of rotation the mercury will naturally assume a parabola more reflective than conventional mirrors.
By introducing sound waves to the liquid mirror it should be possible to induce standing wave nodes which create circular troughs radiating outwards from the centre.
These troughs would then cause sunlight to be focused into a series of focal rings above the surface of the pool.

A heliostat would ensure that line-of-sight would not be a factor when lowering a Fresnel lens onto that series of rings letting us collimate the rings into a beam the width of the mirror which could potentially reach temperatures of several thousands of degrees.

The questions then become; how can I get my hands on that much mercury? Crowd source thermometers maybe? and...

Do you think anyone will care if I carve a happy face on the moons surface?
-- 2 fries shy of a happy meal, Dec 12 2021

Liquid Mirror https://en.wikipedi...id-mirror_telescope
Using mercury is quite an old idea. Just noticed: the first to work was in my old home town! [neutrinos_shadow, Dec 12 2021]

Why are snowflakes so symmetrical and hexagonal? https://www.youtube...watch?v=ao2Jfm35XeE
Sortof relavant, I promise. [RayfordSteele, Dec 13 2021]

So, I can sign you up to send me the first crowd sourced mercury thermometer then?

Okay. One down. Only thirty billion more to go.
-- 2 fries shy of a happy meal, Dec 12 2021


Using spinning mercury as a mirror is a Thing (linky), so that part at least will definitely work. Adding the standing waves sounds interesting, but I'm not sure you can get them the right shape (sine waves are close to parabolic at the bends, but obviously not in the "straight" bits between peak & trough).
-- neutrinos_shadow, Dec 12 2021


A few technical difficulties like gravity and such, but this is interesting enough to be bunworthy.

I was wondering the other night after watching a thing on snowflake formation whether you could create better mirror surfaces by depositing some sort of molecular structure that by the electrochemistry of its surface like an ice crystal would form a smoother surface than what could be achieved by polishing.
-- RayfordSteele, Dec 13 2021


If you're going to dream...
-- 2 fries shy of a happy meal, Dec 14 2021


I like the novelty of the standing wave approach. It'd be worth a thought experiment as to how well the focus would be in outer space.
-- RayfordSteele, Dec 14 2021


It would not be optimal for focusing the maximum amount of light for this application, but a morphing/focusing mirror bears experimentation for sure.
-- 2 fries shy of a happy meal, Dec 16 2021


Can I sign you up for the second mercury thermometer shipment then?

p.s. it was your anno on my lightbender posting that made this pop into my head.
Thought you should know.

Thanks eh.

That was my first new brain-fart in almost two years.

Seriously. Thank you. I was wondering if it would come back again... it's been a while.

Cheers.
-- 2 fries shy of a happy meal, Dec 16 2021


What matters is that they care.
-- pertinax, Dec 16 2021


//mirror bears//
I suspect this idea would work better with sun bears. Maybe a couple of mirror bears.
-- neutrinos_shadow, Dec 16 2021


Don't feed the bears. This doesn't bear saying.

...

On a side note; the folks that punched the passes through our Canadian mountains used to let their children dip their arms in jars of honey and let the bears lick it from their fingers, that's how friendly bears are...
...and where our bear problems stem from.
The pictures of this have since been removed from the internet, but the fact remains.

Shit...

...we weren't really talking about bears were we?
<heavy sigh>
-- 2 fries shy of a happy meal, Dec 17 2021


Further aside, it was said that one might overcome a fear of bears by throwing a bear a steak and a bag of donuts.

Then, watch the bear snub that steak and gobble down the bag of donuts. When you realize you taste like a steak the bear will seem more harmless.
-- reensure, Jan 21 2022


Forgive me, but is the purpose to create a multi-focal mirror, so your sunlight is concentrated into rings, or is this supposed to be the collimation after the concentration mirror.

Because the former can be done with a standard mirror, and the latter defeats the purpose of a maximally focused initial mirror.

(Also, only if you keep a bag of donuts with you at all times).
-- MechE, Jan 21 2022


Not bears, apparently.
-- pertinax, Jan 21 2022


//Forgive me, but is the purpose to create a multi-focal mirror, so your sunlight is concentrated into rings, or is this supposed to be the collimation after the concentration mirror.//

Nothing to forgive, I mean both of those things.
Focusing light into concentric rings so that it can be collimated at intensities which would normally vaporize even a diamond lens.
I know the same first effect can be achieved with standard reflective surfaces, it's just that playing with cymatics and morphing surfaces in my head is fun for me so this popped out.

Two guys out hiking see a bear in the distance and it charges them.
One guy starts changing his hiking boots for running shoes.
His buddy says; "What are you doing? Your not going to outrun the bear!"
The first guy finishes lacing up and says;

"I just gotta outrun you..."
-- 2 fries shy of a happy meal, Jan 22 2022



random, halfbakery