Hi again, everybody.
use a 45 degree mirror to shine light back down onto other
reflectors, and then into the station. In the designs where the
second reflectors are exterior to the station, so the light comes
from large windows on the outside of the station, no provision is
being made to block out the sun's rays coming in directly, on each
side of the second reflector. This will allow sunlight that's
hitting the station directly, instead of from the first reflector, to
shine into the interior of the station. This will generate a
pulsating light, where a couple times per rotation the ambient light
level doubles. This occurs as soon as a clear light path exists from
where you are standing, to the sun. To each side of the reflector,
there exists a clear shot to an outside view. The sun will appear
sweep through this area as the station spins.
To prevent this maddening effect, much like trying to live next to a
flashing neon sign, there should be another reflector, or some other
opaque structure, between the station and the sun. This will assure
that only light coming off the first reflector will provide
illumination.
P.S. I went back over my previous data on skylight thickness. A
worse problem with the small windows may be the need for 8000 miles
of vacuum sealant, to seal the edges of all those 6'x6' windows.
Larger windows reduce this, but require thicker glass. If costs were
known, a lowest-cost size would be easily calculated, balancing glass
cost versus sealing and mounting costs.
Trying to place the glass under tension, in a cylindrical or
spherical shape, doesn't seem to help any, once the diameter gets big
(past a hundred or so feet). To try and treat the station-3 windows
as a pressure cylinder results in glass that's many, many feet
thick. However, if glass fiber were included, the strength increase
might offset this problem.
There's bound to be a clever design solution to this mess. But on
the bright side, there's less need to recycle, since if you can ship
this much glass to a station, it's the equivalent of 100,000
residents throwing away a six-pack of bottles every day, for several
decades.
P.P.S. My previous cost estimates are likely to be high, since I was
using Pyrex, which is very expensive. Float glass would be much
cheaper, though I think we'd have to use tempered glass, which gives
a very large increase in allowable stress.
Best Regards,
George Turner
From: Gturner6PPC@... [mailto:Gturner6PPC@...]
use a 45 degree mirror to shine light back down onto other
reflectors, and then into the station. In the designs where the
second reflectors are exterior to the station, so the light comes
from large windows on the outside of the station, no provision is
being made to block out the sun's rays coming in directly, on each
side of the second reflector.
I'll assume you're referring to the Stanford Torus design.
It's actually not a problem, because the body of the torus blocks the light
from the windows. The torus rotates in the plane of the ecliptic. All the
windows face inward. Thus, no sunlight can enter the windows directly.
I have seen one design that your proposal for a habitat-shading sun shield
reminded me of:
http://www.ssi.org/assets/images/Ch06p088.gif
but here I think the concern is more about not contributing to unwanted heat
buildup than about preventing direct sunlight from entering windows.
Regards,
Mike Combs
From:
Gturner6PPC@... [mailto:Gturner6PPC@...]
I was looking at the stations that have their axis oriented 'up', and
use a 45 degree mirror to shine light back down onto other
reflectors, and then into the station. In the designs where the
second reflectors are exterior to the station, so the light comes
from large windows on the outside of the station, no provision is
being made to block out the sun's rays coming in directly, on each
side of the second reflector.
I'll assume you're referring to the Stanford Torus design.
It's actually not a problem, because the body of the torus blocks the light from the windows. The torus rotates in the plane of the ecliptic. All the windows face inward. Thus, no sunlight can enter the windows directly.
I have seen one design that your proposal for a habitat-shading sun shield reminded me of:
http://www.ssi.org/assets/images/Ch06p088.gif
but here I think the concern is more about not contributing to unwanted heat buildup than about preventing direct sunlight from entering windows.
Regards,
Mike Combs
Some window manufacturers offer a "wire reinforced glass" (c.f., do a
yahoo search on this term) product. You can see it in old school windows
and in prisons. Perhaps this or other types of reinforced glass might
come into play in large habitat windows.
******
Gturner6PPC@...
11/08/01 02:52 PM
Please respond to spacesettlers
To: spacesettlers@yahoogroups.com
cc:
Subject: [spacesettlers] Station needs solar shade
Hi again, everybody.
I was looking at the stations that have their axis oriented 'up', and
use a 45 degree mirror to shine light back down onto other
reflectors, and then into the station. In the designs where the
second reflectors are exterior to the station, so the light comes
from large windows on the outside of the station, no provision is
being made to block out the sun's rays coming in directly, on each
side of the second reflector. This will allow sunlight that's
hitting the station directly, instead of from the first reflector, to
shine into the interior of the station. This will generate a
pulsating light, where a couple times per rotation the ambient light
level doubles. This occurs as soon as a clear light path exists from
where you are standing, to the sun. To each side of the reflector,
there exists a clear shot to an outside view. The sun will appear
sweep through this area as the station spins.
To prevent this maddening effect, much like trying to live next to a
flashing neon sign, there should be another reflector, or some other
opaque structure, between the station and the sun. This will assure
that only light coming off the first reflector will provide
illumination.
P.S. I went back over my previous data on skylight thickness. A
worse problem with the small windows may be the need for 8000 miles
of vacuum sealant, to seal the edges of all those 6'x6' windows.
Larger windows reduce this, but require thicker glass. If costs were
known, a lowest-cost size would be easily calculated, balancing glass
cost versus sealing and mounting costs.
Trying to place the glass under tension, in a cylindrical or
spherical shape, doesn't seem to help any, once the diameter gets big
(past a hundred or so feet). To try and treat the station-3 windows
as a pressure cylinder results in glass that's many, many feet
thick. However, if glass fiber were included, the strength increase
might offset this problem.
There's bound to be a clever design solution to this mess. But on
the bright side, there's less need to recycle, since if you can ship
this much glass to a station, it's the equivalent of 100,000
residents throwing away a six-pack of bottles every day, for several
decades.
P.P.S. My previous cost estimates are likely to be high, since I was
using Pyrex, which is very expensive. Float glass would be much
cheaper, though I think we'd have to use tempered glass, which gives
a very large increase in allowable stress.
Best Regards,
George Turner
--- In spacesettlers@y..., rmenich@m... wrote:
> Some window manufacturers offer a "wire reinforced glass" (c.f., do
a
> yahoo search on this term) product. You can see it in old school
windows
> and in prisons. Perhaps this or other types of reinforced glass
might
> come into play in large habitat windows.
>
> Ron
> ******
>
> Gturner6PPC@y...
> 11/08/01 02:52 PM
> Please respond to spacesettlers
>
> To: spacesettlers@y...
> cc:
> Subject: [spacesettlers] Station needs solar shade
>
> Hi again, everybody.
>
> I was looking at the stations that have their axis oriented 'up',
and
> use a 45 degree mirror to shine light back down onto other
> reflectors, and then into the station. In the designs where the
> second reflectors are exterior to the station, so the light comes
> from large windows on the outside of the station, no provision is
> being made to block out the sun's rays coming in directly, on each
> side of the second reflector. This will allow sunlight that's
> hitting the station directly, instead of from the first reflector,
to
> shine into the interior of the station. This will generate a
> pulsating light, where a couple times per rotation the ambient
light
> level doubles. This occurs as soon as a clear light path exists
from
> where you are standing, to the sun. To each side of the reflector,
> there exists a clear shot to an outside view. The sun will appear
> sweep through this area as the station spins.
>
> To prevent this maddening effect, much like trying to live next to
a
> flashing neon sign, there should be another reflector, or some
other
> opaque structure, between the station and the sun. This will
assure
> that only light coming off the first reflector will provide
> illumination.
>
> P.S. I went back over my previous data on skylight thickness. A
> worse problem with the small windows may be the need for 8000 miles
> of vacuum sealant, to seal the edges of all those 6'x6' windows.
> Larger windows reduce this, but require thicker glass. If costs
were
> known, a lowest-cost size would be easily calculated, balancing
glass
> cost versus sealing and mounting costs.
>
> Trying to place the glass under tension, in a cylindrical or
> spherical shape, doesn't seem to help any, once the diameter gets
big
> (past a hundred or so feet). To try and treat the station-3
windows
> as a pressure cylinder results in glass that's many, many feet
> thick. However, if glass fiber were included, the strength
increase
> might offset this problem.
>
> There's bound to be a clever design solution to this mess. But on
> the bright side, there's less need to recycle, since if you can
ship
> this much glass to a station, it's the equivalent of 100,000
> residents throwing away a six-pack of bottles every day, for
several
> decades.
>
> P.P.S. My previous cost estimates are likely to be high, since I
was
> using Pyrex, which is very expensive. Float glass would be much
> cheaper, though I think we'd have to use tempered glass, which
gives