How to get great viewing at 1G?

[JoeStrout]

A colleague and I were talking this morning about how spectacular the view is in LEO (low-Earth orbit).

I've always assumed that you can't really get great viewing from the 1G areas of your habitat, but would instead go to some zero-G observation deck/bubble.  (Hmm, we should probably add such an observation deck as a part in the game!)  Even if you did have windows in your habitat, if you're rotating at say 2 RPM, I think viewers would get a bit dizzy watching the Earth and the rest of the universe rotate by.

But perhaps I've given up too easily.  Can anybody think of some clever geometry that would let you sit comfortably in 1 G, and yet watch the Earth (or whatever else is outside) without it appearing to spin?

And no fair suggesting a display screen or VR helmet... displays are certainly getting better all the time, and maybe someday they will rival a real view out the window, but for the sake of this discussion I'd like to keep it to optics — mirrors and glass, the sort of thing you could look at through binoculars to get an even better view.  Maybe mirrors or prisms that spin at the same rate as the habitat, in such a way that they produce a stationary virtual image?

Any ideas?

[JoeP]

Funny, I was going to suggest something and then I read your last paragraph - haha.

Aside from putting in fake windows that are really super HD displays with a camera outside that transmits the spin-removed images, I can't think of an obvious solution.

I guess you just have to put the observation bubble on the axis, or even a counter rotating room there.

[JoeStrout]

Yeah, the problem with a display is that it's no selling point — we want to draw tourists in partly for the amazing views, but if they can get exactly the same view at any IMAX theater on Earth, then why pay the half million bucks for a week in LEO?

And it's probably not a big deal, because if you're spending that much to go to LEO, you probably want to spend a fair amount of time in zero-G too.

But it'd be even better if the people living there and spending most of their time at 1G could somehow check out the view on their way home from work, and have it be a real view rather than a display.

[JoeStrout]

I've got it!

There is a category of prisms called "image rotation prisms" which have a curious property: as you rotate the prism, the image you see through it rotates twice as fast.  My current favorite of these is the Pechan prism, which maintains a straight line-of-sight and offers a wide field of view.

So, wherever you have a window out the side of the colony, you just need to add a large Pechan prism, set to rotate at half the colony's rotation rate.  For viewers inside, the image will appear completely non-rotating!

I can even imagine making the entire endcap of your cylinder a giant Pechan prism.  You need shielding on the endcaps anyway; and these prisms are a huge amount of glass, so they would certainly do the trick!  The problem of course is that it would be truly massive (and thus, ridiculously expensive).  Perhaps there's some way to slim it down.  Or maybe there's another trick, like an array of Dove prisms, that would work better.

Here is a good set of class notes about mirrors and prisms.  This one, too.  Both of these are from the University of Arizona, where my wife is a professor of computer science; perhaps I'll go talk to these guys at some point and see if they can help.

[JoeStrout]

This Raytheon patent seems quite applicable.  I'm a bit surprised the patent was granted, though... it doesn't appear to claim anything other than a simple Dove prism array, which I thought has been known for many years.  But perhaps I've missed something (I've only skimmed it quickly at this point).

I wish I could get my hands on a Dove prism array, but my googling hasn't turned up any source for them.  And the individual prisms are quite expensive.  I'd love to see whether these really do rotate without distortion, or whether you get a stripey effect like looking through a shower door.

If they really are distortion-free, then they would be pretty much ideal, since you can make them exactly as thick as you want them to be to provide a derotating window, and radiation shielding at the same time.

[Pye-rate]

I follow 3D.com, some of the optics are incredible. 3D printing developed flat lenses and other seemingly improbable achievements. There could be something there that is helpful.

[JoeStrout]

Hmm, can you double-check that URL? For me, 3d.com appears to be just a parked domain.

[antred]

But are you really going to have any windows so thin that anyone could get a clear view of anything outside the colony anyway? From my understanding, any "windows" would have to be very thick, both for radiation shielding and because they must be damn near impossible to break.

[Pye-rate]

Sorry, 3Dprint.com.

[JoeStrout]

(10-02-2015, 02:13 PM)antred Wrote: But are you really going to have any windows so thin that anyone could get a clear view of anything outside the colony anyway? From my understanding, any "windows" would have to be very thick, both for radiation shielding and because they must be damn near impossible to break.

If you're in low Earth orbit, the radiation shielding requirements are quite modest.  The pressure shell alone is plenty.  And yeah, you have to contain an atmosphere, but that doesn't mean you can't see through 'em — you know how thick the glass (actually, I think it's acryllic) is at a large aquarium, but you can't even tell when you're looking through it.

So yes, windows are doable.  And even without derotation (which it turns out is the proper term, even if my spell checker's never heard of it), the windows would probably be quite popular.  I don't really think anybody's going to get dizzy from watching the Earth spin at 2 RPM.

But not spinning would certainly be a plus, so we should keep exploring that, I think.