I believe consensus opinion is for the "radiation-shield 'cave'
that doesn't rotate" (ref Ian Woollard's 7-22 Radiation Fatigue?
comments). He's saying a conical glass cylinder down axis of
colony cylinder lets in light reflected from a large concave mirror.

Since incoming beam is converging I assume that is why the
conical shape is preferable over true cylindrical for this incoming
light container. Wouldn't there be a series of inclined mirrors on
inside of glass cone required to re-reflect light out to entire inside
of colony cylinder? It would have been far easier to just put a
window @ center of end cap of colony cylinder. However the
fear of a stray meteor "busting through" window makes me favor
this window in form of internal cone-cylinder.

Are we sure Panama Bob's July 8 suggestion to use fibre-optic
to let in sunlight wasn't more practical? I believe his idea was
for the ~2+ meters of regolith to be placed with a lot of fibre-
optic elements through it to let light right thru radiation shield.
If colony assigned outside orbit of Saturn perhaps both the
sources will be needed. If colony assigned around Venus
perhaps we wont need the center window at all (use only fibre-
optic light coming up through ground).

Hallelujah - Praise Spacesettlers ! ! ! Ed S.

Here are my concerns with these two suggestions for colony
illumination.

The ilumination tunnel through the center of the cyclinder will have
concentrated sunlight, which should equal earth surface intensity
when it strikes the colony living surface. Now O'Neill's solution
was to devote equal surface area to land and window, and allow the
exterior mirrors to reflect into the cylinder the sunshine directly
without any concentration. With the illumination tunnel, by what
ratio will the sunlight be concentrated and what will the
temperature of the illimunation tunnel be? I've seen reports that it
would be so hot that all materials would melt. Also, what happens to
the image of a solar disk and the transit of the sun through the
sky?

Perhaps a solution to these issues is to have a hot plasma in the
center illumination tunnel and we concentrate enough sunlight into
the plama for it to burn brightly and still be contained by either a
material that won't melt or by magnetic containment. WE'll have
light, but we won't have a solar disk. There'll just be a sun bright
cylinder running throught the center of the habitat.

I find the fiber optic solution intriguing. I used to think that
they may provide the solution, but consider the sheer volume of
cables that would have to be produced. O'Neill's solution was to
just have plain old glass windows covering half the surface area of
the habitat. To convert that surface area into fiber optics will be
an immense task.

No one has offered a critique of my suggestion in message #2236. I
think it solves a number of problems, but no one has offered their
wisdom in pointing out the flaws in the proposal.

Oh well, . . .

--- In spacesettlers@y..., "Ed Schonert" wrote:
> I believe consensus opinion is for the "radiation-shield 'cave'
> that doesn't rotate" (ref Ian Woollard's 7-22 Radiation Fatigue?
> comments). He's saying a conical glass cylinder down axis of
> colony cylinder lets in light reflected from a large concave
mirror.
>
> Since incoming beam is converging I assume that is why the
> conical shape is preferable over true cylindrical for this incoming
> light container. Wouldn't there be a series of inclined mirrors on
> inside of glass cone required to re-reflect light out to entire
inside

Ed Schonert wrote:

> I believe consensus opinion is for the "radiation-shield 'cave'
> that doesn't rotate" (ref Ian Woollard's 7-22 Radiation Fatigue?
> comments). He's saying a conical glass cylinder down axis of
> colony cylinder lets in light reflected from a large concave mirror.
>
> Since incoming beam is converging

Not quite sure why you say that; it very much could/should be
parallel.

> I assume that is why the
> conical shape is preferable over true cylindrical for this incoming
> light container.

I wasn't thinking that clearly about it. Conical would let the
light through at an angle and would be as strong or stronger.

> Wouldn't there be a series of inclined mirrors on
> inside of glass cone required to re-reflect light out to entire inside
> of colony cylinder?

I'd expect you'd want the mirrors on the vacuum side, because
they stay clean. Cleaning windows is easier

> It would have been far easier to just put a
> window @ center of end cap of colony cylinder.

Yes. On reflection you're probably right. It might be
a good idea to form it as an interior dome however, that
way you get the compression effect I mentioned before, rather
than try to make it flat.

Also, you could then put the mirrors in a cone shape, inside
the colony.

> However the
> fear of a stray meteor "busting through" window makes me favor
> this window in form of internal cone-cylinder.

I think O'Neill was right about this, it's not all that
likely. The odd window will break, but if you engineer them
right it should be ok. You'd want to fix it, but it's not
that bad. Actually that's another advantage- the windows
are smaller.

> Are we sure Panama Bob's July 8 suggestion to use fibre-optic
> to let in sunlight wasn't more practical?

It can work, but it's a lot of fiber. Fiber is only really
transparent in the infrared; although I don't have the figures
handy for the transmission coefficient in the visible.

> I believe his idea was
> for the ~2+ meters of regolith to be placed with a lot of fibre-
> optic elements through it to let light right thru radiation shield.
> If colony assigned outside orbit of Saturn perhaps both the
> sources will be needed. If colony assigned around Venus
> perhaps we wont need the center window at all (use only fibre-
> optic light coming up through ground).

Don't particularly like... light pipes are ok I guess.

> Hallelujah - Praise Spacesettlers ! ! ! Ed S.
>

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding
technological civilization?"
- Gerard O'Neill