Hi. am new here so please bear with me
all references I have heard of the mirrors for O'Neill cylinders
have them running the entire length of the cylinder
would it not be more practical to design it with 6 half length
mirrors and put the first three at 0-60 degrees, 120-180 degrees,
240-300 degrees of the first half of the cylinder. The other three
mirrors would be placed at 060-120 degrees, 180-240 degrees, and 300-
360 degrees in the second half.
This would greatly reduce mirror stress loading and almost halve
the centrifugal forces applied to these mirrors. I am posting this
to hear your opinions on this matter and to see if there is any
problems I have overlooked or am not aware of. Space settlements
start with dreamers - when the dreams are all worked out then the
adventurous step in - I am a dreamer.
Message: 6
Date: Sun, 19 Dec 2004 23:19:43 -0000
From: "levi1_ca"
Subject: redesign of ONeill cylinder mirrors
all references I have heard of the mirrors for O'Neill cylinders
have them running the entire length of the cylinder would it not
be more practical to design it with 6 half length mirrors
Over a year ago(?)when mirror length was being discussed, I suggested
rotating the cylinder 120 degrees at midlength so as to have 6 half
length mirrors....
-but got no response...
RKH
"levi1_ca" wrote:
have them running the entire length of the cylinder
would it not be more practical to design it with 6 half length
mirrors and put the first three at 0-60 degrees, 120-180 degrees,
240-300 degrees of the first half of the cylinder. The other three
mirrors would be placed at 060-120 degrees, 180-240 degrees, and 300-
360 degrees in the second half.
This would greatly reduce mirror stress loading and almost halve
the centrifugal forces applied to these mirrors.<
Yep. But I've also stated that the original O'Neill design, big enough to
house 10 million people, wouldn't be built in the first place. Except
perhaps by a government with money to burn. Or someone committing real
estate fraud.
I envision it this way: Given a dozen habitats able to house 10,000 people
and which are starting to see some housing problems. They'll band together
to build a habitat capable of supporting maybe 60,000 people to handle the
overflow from all 12 smaller habitats.
Eventually, you'll have a dozen of the larger habitats facing a similar
problem. At that point, a twin-cylinder O'Neill colony may be built. Each
cylinder might hold up to 200,000 people, maybe less.
Each cylinder would be 1.8 km x 2.4 km and have 67.824 m^2 per person.
--- In spacesettlers@yahoogroups.com, "Michael Capriola"
wrote:
> Yep. But I've also stated that the original O'Neill design, big
enough to
> house 10 million people, wouldn't be built in the first place.
Except
> perhaps by a government with money to burn. Or someone committing
real
> estate fraud.
>
> I envision it this way: Given a dozen habitats able to house
10,000 people
> and which are starting to see some housing problems. They'll band
together
> to build a habitat capable of supporting maybe 60,000 people to
handle the
> overflow from all 12 smaller habitats.
>
> Eventually, you'll have a dozen of the larger habitats facing a
similar
> problem. At that point, a twin-cylinder O'Neill colony may be
built. Each
> cylinder might hold up to 200,000 people, maybe less.
> Each cylinder would be 1.8 km x 2.4 km and have 67.824 m^2 per
person.
take this idea in a different slant though - with a 060 degess
rotation in alignemnt you can now mate two smaller cylinders
together for a one time expansion with complete light access
this would be a very desireable thing for expansion of existing
habitats - instead of having a pair of habitats 1.8km by 2.4 km you
now have a pair 1.8km by 4.8 km - this increased space/skilled
workforce would be a tremendous advantage.
G'day all you highfrontiers people,
regarding mirror placement. I've wrestled in my own mind for years
and see merit in most of the current designs. From my point of view
I hesitate to take a stand on any set of placement factors as the
reality will probably allow for the construction of multiple types.
My personal opinion is the ultimate use of the central "neon" tube
format is the one that provides the best lighting once habitats
start to spread to the outer solar system. This type allows for
internal power sources ie: fission/fusion, once old Sol is a distant
spark not capable of sustaining a habitats lighting and heating
needs.
Regarding the feasibility of large O'Neill cylinders with internal
areas capable of holding multiple millions, these are IMHO only
likely to become a reality once our race reaches the level of a
stage one civilization. Not really that far in the future, but far
enough ahead that I have to agree they are 'impractical' until such
time a population pressures build to the point they become needed.
For the near term I agree that smaller almost spherical 'freeholds'
containing multiple families with diameters in the range of .25
to .5 km might be the way to go.
If anyone has any further thoughts regarding habitat size I'd like
to share some of them.
--- In spacesettlers@yahoogroups.com, "Michael Capriola"
wrote:
> "levi1_ca" wrote:
>
> >all references I have heard of the mirrors for O'Neill cylinders
> have them running the entire length of the cylinder
> would it not be more practical to design it with 6 half length
> mirrors and put the first three at 0-60 degrees, 120-180 degrees,
> 240-300 degrees of the first half of the cylinder. The other three
> mirrors would be placed at 060-120 degrees, 180-240 degrees, and
300-
> 360 degrees in the second half.
> This would greatly reduce mirror stress loading and almost halve
> the centrifugal forces applied to these mirrors.<
>
> Yep. But I've also stated that the original O'Neill design, big
enough to
> house 10 million people, wouldn't be built in the first place.
Except
> perhaps by a government with money to burn. Or someone committing
real
> estate fraud.
>
> I envision it this way: Given a dozen habitats able to house
10,000 people
> and which are starting to see some housing problems. They'll band
together
> to build a habitat capable of supporting maybe 60,000 people to
handle the
> overflow from all 12 smaller habitats.
>
> Eventually, you'll have a dozen of the larger habitats facing a
similar
> problem. At that point, a twin-cylinder O'Neill colony may be
built. Each
> cylinder might hold up to 200,000 people, maybe less.
> Each cylinder would be 1.8 km x 2.4 km and have 67.824 m^2 per
person.
Michael Capriola wrote:
>
>>all references I have heard of the mirrors for O'Neill cylinders
>>
>>
>have them running the entire length of the cylinder
>would it not be more practical to design it with 6 half length
>
Why to rotate them anyway? With only twice the mirror surface you can
build them non-rotating.
Note that mirrors that large will most certainly consist of smaller
mirrors anyway.
Guess how much structural mass you can save without artificial gravity
on the mirrors?
Much more than a factor of two, I'd say.
(Buy the way, this is not my idea. Got it from the "Rosinante"-Books
written by some
Alexis A. Gilliland.)
Axel Walthelm wrote:
> Why to rotate them anyway? With only twice the mirror surface
> you can build them non-rotating.
. . .
> ([By] the way, this is not my idea. Got it from the
> "Rosinante"-Books written by some Alexis A. Gilliland.)
more than twice the area of O'Neill's rectangular ones.
--
Anton Sherwood, http://www.ogre.nu/
obsolete since 21 December 2001
From: Anton Sherwood [mailto:bronto@...]
> Rosinante have a lot more than twice the area of
> O'Neill's rectangular ones.
And what this translates into is that someone at the anti-sunward end of
the cylinder might experience near-normal levels of insolation. Someone
at the sunward end of the cylinder would be getting rapidly cooked!
Regards,
Mike Combs
--- In spacesettlers@yahoogroups.com, "Combs, Mike"
> From: Anton Sherwood [mailto:bronto@p...]
>
> > If one may pick a nit: the conical mirror-arrays of
> > Rosinante have a lot more than twice the area of
> > O'Neill's rectangular ones.
>
> And what this translates into is that someone at the anti-sunward
end of
> the cylinder might experience near-normal levels of insolation.
Someone
> at the sunward end of the cylinder would be getting rapidly cooked!
>
> Regards,
>
> Mike Combs
1. Re getting rapidly cooked.
Since the mirror would be composed of an array of small mirrors,
those [progressing toward] the sunward end would be gradually
dispersed, i.e., a pattern such as a checkerboard in which less
and less of the "squares" actually contain mirrors.
2a. Re non-rotating conical mirror.
The sheilding could also be cone shaped, non-rotating and exterior
to the mirror..
[Yes it would be Massive, but gradually thinner progressing
sunward. [same concept as above] [-this may need more thought:-]
2b. One problem would be keeping the cone mass aimed at the sun.
Assuming That Problem to be reasonably solvable [?] .., and:
If the mass were made sufficiently rigid and connected to the
cylinder via a bearing of some sort.. [Whew!] -The need for a
2nd counter-rotating cylinder might be eliminated. [Tending to
justify the concept.]
3. But back to the 3 [or 6 mirror concept, [-originally mine I
believe], it had occurred to me that if the mirrors were concave,
[thereby greater in area, tho not portions of a cone] with their
focus at the window, the windows could be narrower, resulting in
more land area.
RKH
From: Bob Hardman [mailto:Bsanctuary@...m]
>
> Since the mirror would be composed of an array of small mirrors,
> those [progressing toward] the sunward end would be gradually
> dispersed, i.e., a pattern such as a checkerboard in which less
> and less of the "squares" actually contain mirrors.
That would work, though we'd no longer have a natural-looking sun in the
sky (and how important an issue this is varies with taste). At the
anti-sunward end, the sun might look pretty normal, though its edges
might seem to ripple a bit. As one progressed toward the sunward end of
the cylinder, the image of the sun would break up into thousands of
brilliant tiny stars which would become steadily further apart. The
"stars" would wink on, move, and then wink out in the same circular
patch of sky.
> 2b. One problem would be keeping the cone mass aimed at the sun.
>
> Assuming That Problem to be reasonably solvable [?] .., and:
>
> If the mass were made sufficiently rigid and connected to the
> cylinder via a bearing of some sort.. [Whew!] -The need for a
> 2nd counter-rotating cylinder might be eliminated. [Tending to
> justify the concept.]
Don't think that would work. One needs something equal in mass to the
rest of the cylinder. And it must be counter-rotating at the same
speed, not simply stationary.
But then turning the rotation axis perpendicular to the orbital plane,
and then using an oval reflector "above" at a 45deg angle would solve
the problem.
> 3. But back to the 3 [or 6 mirror concept, [-originally mine I
> believe], it had occurred to me that if the mirrors were concave,
> [thereby greater in area, tho not portions of a cone] with their
> focus at the window, the windows could be narrower, resulting in
> more land area.
You'd like this design, although I think this person carries it to an
extreme, with tiny windows so hot they require constant water cooling
just so as to not melt.
http://www.nas.nasa.gov/About/Education/SpaceSettlement/Nowicki/SPBI1GH.
HTM
Regards,
Mike Combs
Combs, Mike wrote:
> . . . One needs something equal in mass to the rest of the cylinder.
> And it must be counter-rotating at the same speed, not simply
> stationary.
rate; it might have a different radial distribution of mass.
--
Anton Sherwood, http://www.ogre.nu/
obsolete since 21 December 2001
On Wed, 12 Jan 2005 14:30:28 -0600, Combs, Mike wrote:
> > If the mass were made sufficiently rigid and connected to the
> > cylinder via a bearing of some sort.. [Whew!] -The need for a
> > 2nd counter-rotating cylinder might be eliminated. [Tending to
> > justify the concept.]
>
> Don't think that would work. One needs something equal in mass to the
> rest of the cylinder. And it must be counter-rotating at the same
> speed, not simply stationary.
which is not necessarily the *same* speed.
Total angular momentum is Ic Wc + Ih Wh, and if this equals 0 then
there's no gyroscopic effect.
where Ic is the moment of inertia of cylinder=integral of mass times
(distance from axis squared), Wc is the angular velocity of cylinder
in radians/second
Ih, Wh is the same thing for the habitat.
Actually, that's kinda interesting- the centrifugal force is a square
law on 'w', whereas w is inversely proportional to I, so if you can
use heavy rock for radiation shielding to cancel the angular momentum,
you don't need much strength to stop the slower/heavier moving
radiation shielding from flying apart.
In fact the more radiation shield you have the less you have to tie
the radiation shield together. I guess that's kinda obvious with
hindsight- if you surround a habitat with a massive asteroid you can
spin the habitat against the asteroid, which will hardly rotate at
all, and won't need any strengthening.
> Regards,
>
> Mike Combs
--
-Ian Woollard
Professor Frink: "We studied traffic patterns and found that drivers
move the fastest
through yellow lights. So now, we just have red and yellow lights."
From: Anton Sherwood [mailto:bronto@...]
> > . . . One needs something equal in mass to the rest of the
cylinder.
> > And it must be counter-rotating at the same speed, not simply
> > stationary.
>
> Equal in angular momentum. It could be a smaller mass at a high
> spin rate; it might have a different radial distribution of mass.
True.
Regards,
Mike Combs
From: Ian Woollard [mailto:ian.woollard@...m]
> *right* speed, which is not necessarily the *same* speed.
True. I didn't give much consideration to that aspect because I was
thinking that a design goal here was to have stationary mirrors. In
this case the mirrors would be rotating far faster than the rest of the
habitat, and all the objections to the O'Neill Cylinder mirror design
become stronger.
> Actually, that's kinda interesting- the centrifugal
> force is a square law on 'w', whereas w is inversely
> proportional to I, so if you can use heavy rock for
> radiation shielding to cancel the angular momentum,
> you don't need much strength to stop the slower/heavier
> moving radiation shielding from flying apart.
I think that's the assumption of the Bernal Sphere, and one of its
advantages.
For example, if the shield is 10x the mass of the rest of the habitat
sphere (I think 10x is right for the Stanford Torus; might be slightly
different for Bernal Sphere), then it would counter-rotate at only 1/5
RPM. And no part of it would experience more than 1/10 G centrifugal
force.
Regards,
Mike Combs
On Thu, 13 Jan 2005 08:44:31 -0600, Combs, Mike wrote:
> For example, if the shield is 10x the mass of the rest of the habitat
> sphere (I think 10x is right for the Stanford Torus; might be slightly
> different for Bernal Sphere), then it would counter-rotate at only 1/5
> RPM. And no part of it would experience more than 1/10 G centrifugal
> force.
is 1/10 that of the habitable area. But most of the strength of the
habitable area is to deal with the atmospheric load.
> Regards,
>
> Mike Combs
--
-Ian Woollard
Professor Frink: "We studied traffic patterns and found that drivers
move the fastest
through yellow lights. So now, we just have red and yellow lights."
--- In spacesettlers@yahoogroups.com, Asgard_97@y... wrote:
> My personal opinion is the ultimate use of the central "neon" tube
> format is the one that provides the best lighting once habitats
> start to spread to the outer solar system.
offers lots of advantages over an O'Neill design:
It maximizes the amount of living area for any given cylinder
dimensions; no area of the cylinder is needed to be used for
transparent windows.
It simplifies the problem of making the habitat radiation-shielded.
It means less heat leakage into space, which in the asteroid belt
could be a significant factor.
It could make for a more sound structure as the cylinder would be
composed of one strong material, and not half of it as glass (or
is it quartz or something else?).
The tube could be turned on and off, thus simulating a day/night
cycle. This is a more elegant solution than having to move external
mirrors around.
> Regarding the feasibility of large O'Neill cylinders with internal
> areas capable of holding multiple millions, these are IMHO only
> likely to become a reality once our race reaches the level of a
> stage one civilization. Not really that far in the future, but far
> enough ahead that I have to agree they are 'impractical' until such
> time a population pressures build to the point they become needed.
> For the near term I agree that smaller almost spherical 'freeholds'
> containing multiple families with diameters in the range of .25
> to .5 km might be the way to go.
I think the problems of making truly livable habitats in space are so
vast and numerous that it's going to be a long time before *any* of
these structures are built. In my opinion, when the ability to build
a mile-diameter habitat that actually works is there, then the
ability to build a 50-mile long 10-mile diameter habitat will not be
too far off.
By "freeholds" I assume you mean zero-G habitats, correct?
--- In spacesettlers@yahoogroups.com, "millenial70" wrote:
> offers lots of advantages over an O'Neill design:
>
> It maximizes the amount of living area for any given cylinder
> dimensions; no area of the cylinder is needed to be used for
> transparent windows.
>
> It simplifies the problem of making the habitat radiation-shielded.
>
> It means less heat leakage into space, which in the asteroid belt
> could be a significant factor.
>
> It could make for a more sound structure as the cylinder would be
> composed of one strong material, and not half of it as glass (or
> is it quartz or something else?).
>
> The tube could be turned on and off, thus simulating a day/night
> cycle. This is a more elegant solution than having to move external
> mirrors around.
For the "light tube" where does the light come from?
TangoMan
victoriatangoman wrote:
> For the "light tube" where does the light come from?
is otherwise entirely shielded), and a parabolic mirror at mid axis to
distribute the light (leaving the other pole in twilight). That's not
the only possible approach!
--
Anton Sherwood, http://www.ogre.nu/
obsolete since 21 December 2001
--- In spacesettlers@yahoogroups.com, Anton Sherwood wrote:
> victoriatangoman wrote:
> > For the "light tube" where does the light come from?
>
> The "hatbox" design has a small window in one pole of the habitat
(which
> is otherwise entirely shielded), and a parabolic mirror at mid axis to
> distribute the light (leaving the other pole in twilight). That's not
> the only possible approach!
TangoMan
On Mon, 17 Jan 2005 21:51:53 -0000, millenial70 wrote:
> It means less heat leakage into space, which in the asteroid belt
> could be a significant factor.
Living in a space habitat is like living in a thermos flask. It's
actually easy to cook yourself, particularly if you present a whole
bunch of mirrors towards the sun.
--
-Ian Woollard
Professor Frink: "We studied traffic patterns and found that drivers
move the fastest
through yellow lights. So now, we just have red and yellow lights."
--- In spacesettlers, "millenial70" wrote:
> composed of one strong material, and not half of it as glass (or
> is it quartz or something else?).
Why not sapphire? Aluminum and oxygen, and if VVD'ed, should be easy
enough to deposit as sapphire.
millenial70 wrote:
> It could make for a more sound structure as the cylinder would
> be composed of one strong material, and not half of it as glass.
rather than a solid sheet.
--
Anton Sherwood, http://www.ogre.nu/
obsolete since 21 December 2001
--- In spacesettlers@yahoogroups.com, "millenial70"
> By "freeholds" I assume you mean zero-G habitats, correct?
==No actually. :)
By 'freehold' I meant farm type habitats constructed and inhabited
by interpreneur families.
My take on the situation for the near term is for multi-
family 'modified' rotating Bernal class habitats, that are in the
neigborhood of approximately .25 to .50 km in diameter and ~ 1 km in
length. These would be classical Italian hilltown type communities
with populations in the 250-1000 people range. As I see it these
will form the basis of later larger habitats.
--- In spacesettlers@yahoogroups.com, Asgard_97@y... wrote:
>
> --- In spacesettlers@yahoogroups.com, "millenial70"
> wrote:
> > By "freeholds" I assume you mean zero-G habitats, correct?
> ==> No actually. :)
> By 'freehold' I meant farm type habitats constructed and inhabited
> by interpreneur families.
> My take on the situation for the near term is for multi-
> family 'modified' rotating Bernal class habitats, that are in the
> neigborhood of approximately .25 to .50 km in diameter and ~ 1 km in
> length. These would be classical Italian hilltown type communities
> with populations in the 250-1000 people range. As I see it these
> will form the basis of later larger habitats.
Why?
TangoMan
> Asgard_97 wrote:
>> By 'freehold' I meant farm type habitats
>> constructed and inhabited by interpreneur families. . . .
> Why?
Perhaps because starting small is easier than
jumping straight to a city for many thousands.
--
Anton Sherwood, http://www.ogre.nu/
obsolete since 21 December 2001
Anton Sherwood wrote:
> > Why to rotate them anyway? With only twice the mirror surface
> > you can build them non-rotating.
> . . .
> > ([By] the way, this is not my idea. Got it from the
> > "Rosinante"-Books written by some Alexis A. Gilliland.)
>
>If one may pick a nit: the conical mirror-arrays of Rosinante have a lot
>more than twice the area of O'Neill's rectangular ones.
>
It may look like that at first ... but then think again please:
there are a lot of gaps between the mirror elements (which don't show in
the pictures you may have seen).
If rosinante would use more than twice the mirror area, the sunlight
reflected into the habitat would be much brighter at the sun-side of the
cylinder.
Okay, you need a bit of structure to keep the "small" mirrors in place, but
how much would that be in zero gravity?
Simple and elegant. Just the kind of solutions space settlements need.
Think! Think again!
I'm a bit surprised to see this discussion continued here. My browser
sorts it in a different thread. Didn't find it before writing my last
response.
So, very well, you are really thinking about it :*)
>Three points;
>
>1. Re getting rapidly cooked.
>
> Since the mirror would be composed of an array of small mirrors,
> those [progressing toward] the sunward end would be gradually
> dispersed, i.e., a pattern such as a checkerboard in which less
> and less of the "squares" actually contain mirrors.
>
Thanks for pointing this out.
>2a. Re non-rotating conical mirror.
>
> The sheilding could also be cone shaped, non-rotating and exterior
> to the mirror..
>
> [Yes it would be Massive, but gradually thinner progressing
> sunward. [same concept as above] [-this may need more thought:-]
>
Yes, no saving of mass on this idea. Only that you can use any "dirt"
without structural strength.
>2b. One problem would be keeping the cone mass aimed at the sun.
>
> Assuming That Problem to be reasonably solvable [?] .., and:
>
I think its not too difficult to rotate the shield once per year,
assuming the habitat is in solar orbit.
Rotating it every week or so might need some added structural strength.
> If the mass were made sufficiently rigid and connected to the
> cylinder via a bearing of some sort.. [Whew!] -The need for a
> 2nd counter-rotating cylinder might be eliminated. [Tending to
> justify the concept.]
>
Well, axes of rotaton of cylinder and shield would be perpendicular.
You're sure this works out? I have a feeling direct coupling could
result in some nasty
precession or tumbling effects...
Ian Woollard wrote:
>which is not necessarily the *same* speed.
>
>Total angular momentum is Ic Wc + Ih Wh, and if this equals 0 then
>there's no gyroscopic effect.
>
Ah, I see, the idea is to rotate the shield around two axes. Or more
precise to counter-rotate
the shield around the sun-ward axis and rotate all of the habitat around
an axis perpendicular to that.
Yes, that might work, but unless you use a lot of mass for shield, this
will put quite some
pseudo-gravity on the shield, which after all takes away it's biggest
advantage: almost no structural strength necessary.
Combs, Mike wrote:
>
>>1. Re getting rapidly cooked.
>>
>> Since the mirror would be composed of an array of small mirrors,
>> those [progressing toward] the sunward end would be gradually
>> dispersed, i.e., a pattern such as a checkerboard in which less
>> and less of the "squares" actually contain mirrors.
>>
>>
>
>That would work, though we'd no longer have a natural-looking sun in the
>sky (and how important an issue this is varies with taste). At the
>anti-sunward end, the sun might look pretty normal, though its edges
>might seem to ripple a bit. As one progressed toward the sunward end of
>the cylinder, the image of the sun would break up into thousands of
>brilliant tiny stars which would become steadily further apart. The
>"stars" would wink on, move, and then wink out in the same circular
>patch of sky.
>
Maybe you would like to think of it like an approximation to a
semitransparent mirror.
Or like a picture composed of pixels on your computer display.
I doubt you could look into the sun and see those thousand stars.
Think of it as a transparent mirror and you realize the sun won't appear
larger on the sunward side.
As for the rippling, it depends on the size, spacing and quality of the
mirrors.
I'd say it could be much cheaper to have it built the way you describe it,
but if you (or the rich people having this habitat built for them) can
order to make the mirrors
better and the sun look more natural.
Hm, maybe the bending of the conical structure may tend to have an
enlarging effect.
Maybe you can compensate by swinging the small mirrors forth and back a
little in
synchronization with the cylinders rotation. Even more expensive...
I for myself do not intend to look into the sun. It's unhealthy to the
eyes. ;*)
Maybe a star-field-like distributed sun is what gives a more comfortable
light in the end...
victoriatangoman wrote:
>
>>victoriatangoman wrote:
>> > For the "light tube" where does the light come from?
>>
>>The "hatbox" design has a small window in one pole of the habitat
>>
>>
>(which
>
>>is otherwise entirely shielded), and a parabolic mirror at mid axis to
>>distribute the light (leaving the other pole in twilight). That's not
>>the only possible approach!
>>
>>
>
>What's to stop the window material from melting?
>
Hm, active cooling?
Put some turbines in between the window and the radiators and you have a
powerful power station.
(Wasn't this discussed some months ago?)