Hi,

Mike -- in one of your mails you mentioned the following

The published designs for the Stanford Torus and the Bernal Sphere had the same population (10,000; you're aiming higher), so that's a basis for direct comparison. The masses listed in those studies were
10 million tons for a Stanford Torus and less than 4 million tons for a Bernal Sphere. As we scale upward, this ratio might change, but I don't really see it reversing.

This would seem to suggest that a sphere is more efficient of building materials than a torus.

For the structural masses (of the Bernal Sphere and the Stanford Torus)calculated above, what rate of rotation have you considered for both?
Are the masses 4 million tons and 10 million tons both at the same rpm or are they at different rpms, i.e., 1 for the Stanford Torus and 2 for the Bernal Sphere? Basically, I want to know that if we assume 2 rpm to be a safe rate of rotation and construct both the torus and the sphere to rotate at 2 rpm will the Bernal sphere still be more economical?

Thanks and regards
Saatvik Agarwal

The masses quoted below assume the RPMs quoted below. If we were
redesigning the Stanford Torus with the assumption that 2 RPMs was
acceptable, we could make it about half the diameter. However, it would
then have less habitable area, and hence would no longer be a direct
comparison to the Bernal Sphere.

I think the question you're trying to ask is, "All other things being
equal, which is more efficient of building material, a sphere or a
torus?" I think the answer is "sphere". I think their heightened
concern about rotation rates may have caused the Summer Study group to
go with a greater radius (1.1 miles) than they might have otherwise.
Not being able to back away from the fixed, large radius, they then
tried to minimize structural mass by going with a torus shape. But the
Torus takes a big hit when it comes to the mass of the radiation shield.
The sphere shape represents the greatest volume enclosed by the smallest
surface area.

Another thing they put a great deal of emphasis on was that some
portions of the landscape be beyond sight. They seemed to think there
would be some kind of psychological problem with being able to take in
the entire landscape at a glance. My attitude is that we can't know
this will be a problem until we perform the experiment. Personally, I
suspect wide open spaces overhead in a sphere of smaller diameter might
be less claustrophobic than a glass ceiling a few tens of meters
overhead (not that I expect even that to be a major issue).

The only other issues I can think of which might push us in the
direction of a torus is if there turns out to be some extraordinary and
unanticipated expense with providing nitrogen to High Earth Orbit. The
Bernal Sphere requires a greater volume of air, but then that greater
air volume might make the ecology more stable. And I really don't
expect the atmosphere to be one of the most expensive parts of the
habitat.

Regards,

Mike Combs

From: Saatvik Agarwal [mailto:asaatvik@...]
Sent: Thursday, October 14, 2004 11:15 PM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Stanford Torus vs Bernal Sphere

Hi,

Mike -- in one of your mails you mentioned the following

The published designs for the Stanford Torus and the Bernal Sphere had
the same population (10,000; you're aiming higher), so that's a basis
for direct comparison. The masses listed in those studies were 10
million tons for a Stanford Torus and less than 4 million tons for a
Bernal Sphere. As we scale upward, this ratio might change, but I don't
really see it reversing.

This would seem to suggest that a sphere is more efficient of building
materials than a torus.

For the structural masses (of the Bernal Sphere and the Stanford
Torus)calculated above, what rate of rotation have you considered for
both? Are the masses 4 million tons and 10 million tons both at the same
rpm or are they at different rpms, i.e., 1 for the Stanford Torus and 2
for the Bernal Sphere? Basically, I want to know that if we assume 2 rpm
to be a safe rate of rotation and construct both the torus and the
sphere to rotate at 2 rpm will the Bernal sphere still be more
economical?

Thanks and regards
Saatvik Agarwal

I think the question you're trying to ask is, "All other things being
equal, which is more efficient of building material, a sphere or a
torus?" I think the answer is "sphere". I think their heightened
concern about rotation rates may have caused the Summer Study group to
go with a greater radius (1.1 miles) than they might have otherwise.
Not being able to back away from the fixed, large radius, they then
tried to minimize structural mass by going with a torus shape. But the
Torus takes a big hit when it comes to the mass of the radiation shield.
The sphere shape represents the greatest volume enclosed by the smallest
surface area.

Right, that's exactly what I meant. Since you say a sphere is more
efficient of building materials, can you give some sort of an idea about
what would be the difference between the structural mass of a sphere and
a torus (of course, keeping all other factors constant)?

Thanks once again and regards
Saatvik Agarwal

Combs, Mike wrote:

Hi
I would like to ask about the requiement of elevators in Stanford Torus. It is clear that elevators would be required in the Torus for transporting materials to and fro from the docking facilities. But I think this holds true for Bernal Sphere also as one would always require an elevator in it for the same purpose as docking facilities are once again in zero-g or micro-g region.
In this aspect, i think Bernal sphere doesn't prove to be better than Stanford Torus... What do you say ?
Regards
Anuj Madan

"Combs, Mike" wrote:
The masses quoted below assume the RPMs quoted below. If we were
redesigning the Stanford Torus with the assumption that 2 RPMs was
acceptable, we could make it about half the diameter. However, it would
then have less habitable area, and hence would no longer be a direct
comparison to the Bernal Sphere.

I think the question you're trying to ask is, "All other things being
equal, which is more efficient of building material, a sphere or a
torus?" I think the answer is "sphere". I think their heightened
concern about rotation rates may have caused the Summer Study group to
go with a greater radius (1.1 miles) than they might have otherwise.
Not being able to back away from the fixed, large radius, they then
tried to minimize structural mass by going with a torus shape. But the
Torus takes a big hit when it comes to the mass of the radiation shield.
The sphere shape represents the greatest volume enclosed by the smallest
surface area.

Another thing they put a great deal of emphasis on was that some
portions of the landscape be beyond sight. They seemed to think there
would be some kind of psychological problem with being able to take in
the entire landscape at a glance. My attitude is that we can't know
this will be a problem until we perform the experiment. Personally, I
suspect wide open spaces overhead in a sphere of smaller diameter might
be less claustrophobic than a glass ceiling a few tens of meters
overhead (not that I expect even that to be a major issue).

The only other issues I can think of which might push us in the
direction of a torus is if there turns out to be some extraordinary and
unanticipated expense with providing nitrogen to High Earth Orbit. The
Bernal Sphere requires a greater volume of air, but then that greater
air volume might make the ecology more stable. And I really don't
expect the atmosphere to be one of the most expensive parts of the
habitat.

Regards,

Mike Combs

From: Saatvik Agarwal [mailto:asaatvik@...]
Sent: Thursday, October 14, 2004 11:15 PM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Stanford Torus vs Bernal Sphere

Hi,

Mike -- in one of your mails you mentioned the following

The published designs for the Stanford Torus and the Bernal Sphere had
the same population (10,000; you're aiming higher), so that's a basis
for direct comparison. The masses listed in those studies were 10
million tons for a Stanford Torus and less than 4 million tons for a
Bernal Sphere. As we scale upward, this ratio might change, but I don't
really see it reversing.

This would seem to suggest that a sphere is more efficient of building
materials than a torus.

For the structural masses (of the Bernal Sphere and the Stanford
Torus)calculated above, what rate of rotation have you considered for
both? Are the masses 4 million tons and 10 million tons both at the same
rpm or are they at different rpms, i.e., 1 for the Stanford Torus and 2
for the Bernal Sphere? Basically, I want to know that if we assume 2 rpm
to be a safe rate of rotation and construct both the torus and the
sphere to rotate at 2 rpm will the Bernal sphere still be more
economical?

Thanks and regards
Saatvik Agarwal

From: Saatvik Agarwal [mailto:asaatvik@....uk]

> Since you say a sphere is more
> efficient of building materials, can you give some sort of an idea
about
> what would be the difference between the structural mass of a sphere
and
> a torus (of course, keeping all other factors constant)?

Well, since I'm neither a scientist nor an engineer, all I can really do
is compare published and peer-reviewed studies (the webpage calculators
others are referencing may well function beautifully, but bear in mind
that's not peer-reviewed work). Since the Stanford Torus and the Bernal
Sphere both have the same population, I think they are directly
comparable. The published figures of 10 million tons mass vs. 4 million
tons would seem to imply about a 2:1 ratio. Bear in mind that's total
mass, which would include shielding as well as structural mass. But
that's the figure for how much total mass must be processed.

Regards,

Mike Combs

From: Anuj Madan [mailto:anujmadan_pec@....in]

> I would like to ask about the requiement of elevators in
> Stanford Torus. It is clear that elevators would be required
> in the Torus for transporting materials to and fro from the
> docking facilities. But I think this holds true for Bernal
> Sphere also as one would always require an elevator in it
> for the same purpose as docking facilities are once again in
> zero-g or micro-g region.
>
> In this aspect, i think Bernal sphere doesn't prove to be
> better than Stanford Torus... What do you say ?

I'm sure that routine traffic will use some kind of tram, or in some
simpler arrangement chair-lifts on cables. But O'Neill's point was that
if the power went out in a Bernal Sphere, you could start walking uphill
toward one of the two "poles" of the sphere. Towards the end of your
journey, you'd be more-or-less climbing straight up, but by that point
you would only weigh a few pounds, and so probably would be having no
problems continuing your ascent.

In a Stanford Torus, one might possibly have a spiral staircase or
ladder in the spokes adjacent to the elevator shafts. But that would be
a ladder half a mile long, and lord knows how much longer the spiral
staircase would be. People stopping from exhaustion would be creating
traffic jams (people ascending to the spin axis of a Bernal Sphere would
be coming in radially from all directions). Maybe if you were losing
weight with each step, it might not be as unmanageable as it would seem
from our Earthly perspective. But walking up a much shorter hill sure
sounds a lot easier.

Regards,

Mike Combs

Thanks for trying anyway.

Since a Bernal Sphere is clearly superior to the
Stanford torus I read up on it's design on the
internet. Although not as well documented as the
Stanford Torus, I did find some useful info at
www.l5news.org. While looking at some of the artists'
renditions I was confused as to whether the sphere is
flattened from the bottom or not and about how
sunlight is reflected into the sphere.

Any pointers to more detailed information (other than
what Googling for Bernal Sphere brings up) will also
be helpful.

Thanks and regards
Saatvik Agarwal

--- "Combs, Mike" wrote:

From: Saatvik Agarwal [mailto:asaatvik@...]

> Since you say a sphere is more
> efficient of building materials, can you give some
sort of an idea
about
> what would be the difference between the structural
mass of a sphere
and
> a torus (of course, keeping all other factors
constant)?

Well, since I'm neither a scientist nor an engineer,
all I can really do
is compare published and peer-reviewed studies (the
webpage calculators
others are referencing may well function beautifully,
but bear in mind
that's not peer-reviewed work). Since the Stanford
Torus and the Bernal
Sphere both have the same population, I think they are
directly
comparable. The published figures of 10 million tons
mass vs. 4 million
tons would seem to imply about a 2:1 ratio. Bear in
mind that's total
mass, which would include shielding as well as
structural mass. But
that's the figure for how much total mass must be
processed.

Regards,

Mike Combs

From: Saatvik Agarwal [mailto:asaatvik@....uk]

> Since a Bernal Sphere is clearly superior to the
> Stanford torus I read up on it's design on the
> internet. Although not as well documented as the
> Stanford Torus, I did find some useful info at
> www.l5news.org. While looking at some of the artists'
> renditions I was confused as to whether the sphere
> is flattened from the bottom or not

We had a discussion here a while back about how one could lay decking
down a couple of stories or more over the "equator" and thus increase
the amount of level land underfoot. The space between this deck and the
pressure hull could be used for shopping malls, sports stadiums, storage
warehouses, etc, which would otherwise be cluttering up the landscape.

> and about how
> sunlight is reflected into the sphere.

This diagram displays the light paths -
http://www.ssi.org/assets/images/Ch08p125.gif

Here's cross-section which might help you visualize that deck I was
talking about - http://www.ssi.org/assets/images/Ch99p302.gif

Regards,

Mike Combs

Another thing - Since only the equator of the Bernal sphere can be
occupied how can we calculate the surface area of equator of the area,
i.e. the habitable area?
Are there any formulas?

Thanks and regards
Saatvik Agarwal
P.S.- I know you aren't an engineer but just asking :)

Combs, Mike wrote:

On Mon, 18 Oct 2004 09:09:39 -0500, Combs, Mike wrote:
> In a Stanford Torus, one might possibly have a spiral staircase or
> ladder in the spokes adjacent to the elevator shafts. But that would be
> a ladder half a mile long, and lord knows how much longer the spiral
> staircase would be. People stopping from exhaustion would be creating
> traffic jams (people ascending to the spin axis of a Bernal Sphere would
> be coming in radially from all directions). Maybe if you were losing
> weight with each step, it might not be as unmanageable as it would seem
> from our Earthly perspective. But walking up a much shorter hill sure
> sounds a lot easier.

It's fairly easy to work out how much effort it is to climb.

A climbers 'g' is directly proportional to the distance from the axis.

The energy the climber must expend varies as the g-force varies
linearly with distance from the axis.

Let distance from the central axis be 'r' and the rim radius of the
habitat be 'h', m is the climbers mass, w is the rotation rate of the
habitat in radians per second (i.e. 2 Pi times the rotation rate per
second)

The force on the climber at any point in the habitat is f=m r w^2
_ _
energy = force times distance = _| f dr = _| mrw^2 dr

= [0.5 m r^2 w^2] (0 to h) = 0.5 m h^2 w^2 - 0

Separating out 'g' (which happens to be the acceleration at rim
divided by m = m h w^2/m = hw^2)

= 0.5 m g h

This compares with the earth-based equation over the same distance
which is just mgh.

In other words, the energy you need to expend to climb from the rim to
the axis is half that of climbing the same distance at 1g. So,
climbing 1km vertically to the axis in a habitat is the same as
climbing 500 m on earth. Tiring, but fit people should have no great
problem.

A 70kg man climbing up a 1km radius habitat exerts as much as climbing
500m on earth = mgh = 70 x 9.81 x 500 = 343 kJ = 82 kCals

However peoples muscles aren't particularly efficient so you'd
actually need to eat several times that to regain the energy you lost
from the climb. I forget the inefficiency ratio. Multiply by a few.

This 'half the height' rule only works from the rim to the axis.
Obviously walking upstairs one floor isn't twice as easy, since the
gravity hardly varies.

The general rule if you climb one floor, or from say 3/4 of the rim
radius, to 1/3 way up or whatever, is to use the gravity at the
halfway point between the two points and multiply by the distance
climbed. (Proof left as an exercise to the reader.)

> Regards,
>
> Mike Combs

--
-Ian Woollard

"In theory there is no difference between theory and practice, but in
practice there is."

From: Saatvik Agarwal [mailto:asaatvik@....uk]

> Another thing - Since only the equator of the Bernal sphere can be
> occupied how can we calculate the surface area of equator of the area,

> i.e. the habitable area?
> Are there any formulas?

Oh, I'm sure that much more than just the equator of a Bernal Sphere
will be occupied. I think you'd have to get beyond 45 degrees before
people would stop wanting to develop residential properties (since
that's the angle of standard stairs).

I think O'Neill estimated that about 70% of the interior surface area of
the sphere could see residential occupancy.

And even higher, I'd anticipate tall buildings for various low-G
recreational facilities and hotels. (For example, if you had visitors
from the moon, they might prefer to stay at a place which was 5/6th's of
the way up to the spin axis.)

Regards,

Mike Combs

I went through the deck design in the message archive and checked out
the link you sent :
http://www.ssi.org/assets/images/Ch99p302.gif

Maybe I'm just way too stupid, but I didn't understand where the decks
would go in this picture. If I'm right they would go in the left and
right edges of the sphere where those small buildings are.
And what are the battleship and the zeppelin doing in the middle of the
sphere? Do they represent docking or something?

Thanks and regards
Saatvik Agarwal

Combs, Mike wrote:

From: Saatvik Agarwal [mailto:asaatvik@....uk]

> I went through the deck design in the message archive and checked out
> the link you sent : http://www.ssi.org/assets/images/Ch99p302.gif
>
> Maybe I'm just way too stupid, but I didn't understand where the decks

> would go in this picture. If I'm right they would go in the left and
> right edges of the sphere where those small buildings are.

I think you've got the right idea. In cross-section, we would be
enclosing a space in the shape of a long, skinny "D" laying face-down.
The deck would be a section of a cylinder. Land everywhere on its upper
surface would be level underfoot, and gravity would be slightly less
than it would be on the equator.

Let's say we left 3 stories between the deck and the equator. Sports
stadiums and shopping malls could go in the center (still talking
cross-sectional illustration here). Warehouses which might only require
2 stories height could go on either side. Light industries or other
buildings where windows to the "outdoors" aren't important might only
require 1 story and can go on either side of that.

> And what are the battleship and the zeppelin doing in the middle of
the
> sphere? Do they represent docking or something?

No, they're just there to provide a sense of scale. Although one
waggish student at the seminar I attended had decided the zeppelin was
the Hindenburg, and the ship was the Titanic (it's actually the QEII),
and wondered if there wasn't some message warning of imminent
techno-disaster! But that did prompt a discussion on the importance of
computer modeling to prevent situations which might result in resonance
frequencies and the like.

Regards,

Mike Combs

From: Combs, Mike [mailto:mikecombs@...]

all I can really do is compare published and peer-reviewed studies ... The
published figures of 10 million tons mass vs. 4 million tons would seem to
imply about a 2:1 ratio.

Mike, can you aim us at your "published and peer-reviewed studies"? I don't
doubt you; I just love to document these things for other discussions on
other lists. Thanks...

Dave
"Is a planetary surface the right place for an expanding technological
civilization?" Dr. Gerard K. O'Neill

Mike wrote,

Another thing they put a great deal of emphasis on was that some
portions of the landscape be beyond sight. They seemed to think there
would be some kind of psychological problem with being able to take in
the entire landscape at a glance....

I would support this view. To be really habitable the spacehab should be large enough.

Radius/rpm relationships for 1 g

Radius RPM
(Metres)

1 30
100 3
225 2
900 1

Hush..hhh let's keep it a secret! If the construction lobby gets wind that concrete has to be poured in space, they will set about it in right earnest: if it were not for the pesky environmentalists they would have laid a layer of concrete, 0.5M thick, on planet earth by now!.. Never doubt humanity's ability to pour concrete; the problem is not in making the 5Km dia habitat but the first one of 200M dia.

Selvaraj

From: Combs, Mike
To: spacesettlers@yahoogroups.com
Sent: Friday, October 15, 2004 7:04 PM
Subject: RE: [spacesettlers] Stanford Torus vs Bernal Sphere

The masses quoted below assume the RPMs quoted below. If we were
redesigning the Stanford Torus with the assumption that 2 RPMs was
acceptable, we could make it about half the diameter. However, it would
then have less habitable area, and hence would no longer be a direct
comparison to the Bernal Sphere.

I think the question you're trying to ask is, "All other things being
equal, which is more efficient of building material, a sphere or a
torus?" I think the answer is "sphere". I think their heightened
concern about rotation rates may have caused the Summer Study group to
go with a greater radius (1.1 miles) than they might have otherwise.
Not being able to back away from the fixed, large radius, they then
tried to minimize structural mass by going with a torus shape. But the
Torus takes a big hit when it comes to the mass of the radiation shield.
The sphere shape represents the greatest volume enclosed by the smallest
surface area.

Another thing they put a great deal of emphasis on was that some
portions of the landscape be beyond sight. They seemed to think there
would be some kind of psychological problem with being able to take in
the entire landscape at a glance. My attitude is that we can't know
this will be a problem until we perform the experiment. Personally, I
suspect wide open spaces overhead in a sphere of smaller diameter might
be less claustrophobic than a glass ceiling a few tens of meters
overhead (not that I expect even that to be a major issue).

The only other issues I can think of which might push us in the
direction of a torus is if there turns out to be some extraordinary and
unanticipated expense with providing nitrogen to High Earth Orbit. The
Bernal Sphere requires a greater volume of air, but then that greater
air volume might make the ecology more stable. And I really don't
expect the atmosphere to be one of the most expensive parts of the
habitat.

Regards,

Mike Combs

From: Saatvik Agarwal [mailto:asaatvik@...]
Sent: Thursday, October 14, 2004 11:15 PM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Stanford Torus vs Bernal Sphere

Hi,

Mike -- in one of your mails you mentioned the following

The published designs for the Stanford Torus and the Bernal Sphere had
the same population (10,000; you're aiming higher), so that's a basis
for direct comparison. The masses listed in those studies were 10
million tons for a Stanford Torus and less than 4 million tons for a
Bernal Sphere. As we scale upward, this ratio might change, but I don't
really see it reversing.

This would seem to suggest that a sphere is more efficient of building
materials than a torus.

For the structural masses (of the Bernal Sphere and the Stanford
Torus)calculated above, what rate of rotation have you considered for
both? Are the masses 4 million tons and 10 million tons both at the same
rpm or are they at different rpms, i.e., 1 for the Stanford Torus and 2
for the Bernal Sphere? Basically, I want to know that if we assume 2 rpm
to be a safe rate of rotation and construct both the torus and the
sphere to rotate at 2 rpm will the Bernal sphere still be more
economical?

Thanks and regards
Saatvik Agarwal

From: Saatvik Agarwal [mailto:asaatvik@...] wrote:
> Since you say a sphere is more efficient of building materials, can you
>give some sort of an idea
about
>what would be the difference between the structural mass of a sphere
and
>a torus (of course, keeping all other factors constant)?

"Combs, Mike" responded:

"Well, since I'm neither a scientist nor an engineer, all I can really do
is compare published and peer-reviewed studies (the webpage calculators
others are referencing may well function beautifully, but bear in mind
that's not peer-reviewed work). Since the Stanford Torus and the Bernal
Sphere both have the same population, I think they are directly
comparable. The published figures of 10 million tons mass vs. 4 million
tons would seem to imply about a 2:1 ratio. Bear in mind that's total
mass, which would include shielding as well as structural mass. But
that's the figure for how much total mass must be processed."

There's also the mass of the atmosphere to take into account. But the only
way I can calculate all this is to use the webpage calculator linked to the
NASA/Stanford "Space Settlements" site. Phred only knows if it's accurate
or not.

So here are the stats I just ran, curtesy of www.belmont.k12,etc and Tug
Sezen/Al Globus, based on populations of 10,000 at 68m^2 per person....

Torus: Sphere:
shielding -- 9.787 Mt, shielding -- 6.32 Mt,
nitrogen mass -- 25.41 kt, nitrogen mass -- 53.9 kt,
oxygen mass -- 16.9 kt, oxygen mass -- 35.9 kt,
structural mass -- 151.06 kt structural mass -- 478.7 kt

The torus rotates at 1.037 rpm and the sphere at 1.645 rpm.
The torus has a major radius of 830 m and a m inor radius of 65 m.
The sphere has a radius of 330 m.

Both habitats require 200 tons of water and 31 tons of food daily.

Adding up the figures, I find that most of the extra 3.467 Mt of shield for
the torus makes up the 3.09 Mt difference between the two habitats. In
everything else -- nitrogen, oxygen, structural mass -- the torus uses less
than the sphere.

This is because the torus has more surface area that needs to be shielded --
2,127,701 m^2 compared to 1,367,784 m^2 for the torus.

From: Combs, Mike [mailto:mikecombs@...]

We had a discussion here a while back about how one could lay decking
down a couple of stories or more over the "equator" and thus increase
the amount of level land underfoot. The space between this deck and the
pressure hull could be used for...

Very nice... several good ideas... Another thing that'd work well in this
`in-between' zone would be water tanks. Although most folks think of heavy
materials for the job, water is a great radiation shield. Large tanks (of
any liquid, by why not oh-so-usable water?) could also act to stabilize the
spin of the habitat.

Wow, it's so great to be on a list where (almost!) everyone is thinking in
terms of O'Neill's and other space habitats, instead of just jumping back
down another (Lunar, Martian, etc.) gravity well.

Dave
"Why get excited about anything that doesn't go straight up?" Arthur C.
Clarke, 1952

From: Ian Woollard [mailto:ian.woollard@...]

"It's fairly easy to work out how much effort it is to climb."

(Calculations snipped)

"In other words, the energy you need to expend to climb from the rim to
the axis is half that of climbing the same distance at 1g."

A good, simple rule of thumb to remember. Thanks. However...

"So, climbing 1km vertically to the axis in a habitat is the same as
climbing 500 m on earth. Tiring, but fit people should have no great
problem."

Hmmm... Either I'm missing something, or your "500 m on Earth" translates
into about 150 stories of stairs. Unless your definition of "fit people"
refers to `Iron Man' triatheletes, it's not a physical undertaking to
be set aside casually. Possible... but *very* difficult. Have you tried
climbing the stairs of the Sears Tower, or the Empire State Building?

Dave

The study which produced the Stanford Torus is available on the web
here:
http://lifesci3.arc.nasa.gov/SpaceSettlement/75SummerStudy/Design.html

I don't know that I ever got to see the study which produced the Bernal
Sphere. I think everything I know about it comes out of The High
Frontier. I know that the 4 million ton figure I quoted came from that
book.

Regards,

Mike Combs

From: Dave Logsdon [mailto:templar@sound.net]
Sent: Monday, October 18, 2004 4:49 PM
To: spacesettlers@yahoogroups.com
Subject: RE: [spacesettlers] Stanford Torus vs Bernal Sphere

From: Combs, Mike [mailto:mikecombs@...]

all I can really do is compare published and peer-reviewed studies ...
The published figures of 10 million tons mass vs. 4 million tons would
seem to imply about a 2:1 ratio.

Mike, can you aim us at your "published and peer-reviewed studies"? I
don't doubt you; I just love to document these things for other
discussions on other lists. Thanks...

From: Michael Capriola [mailto:capcartoonist@hotmail.com]

> Adding up the figures, I find that most of the extra 3.467 Mt of
shield for
> the torus makes up the 3.09 Mt difference between the two habitats.
In
> everything else -- nitrogen, oxygen, structural mass -- the torus uses
less
> than the sphere.
>
> This is because the torus has more surface area that needs to be
shielded --
> 2,127,701 m^2 compared to 1,367,784 m^2 for the torus.

That sounds right to me. I get the impression the calculator is making
a slightly bigger sphere than what O'Neill proposed. It could be that
he was assuming a slightly greater population density. I know he
compared it to some of the older parts of Europe.

Regards,

Mike Combs

Hi
If the power goes out, why would one need to go to the dock or zero-g regoin. We cannot afford for the power to go out... coz if it goes out, there will be no communication with space vehicles and hence docking will not be possible, be it Bernal sphere or torus. Hence no use of a space settlement, if the power goes out.... coz all the activities will come to a standstill, so we will need to have a backup system and that can be used for elevators too.

I think one should not choose Bernal sphere keeping in mind this constraint coz sphere seems to be useless... its such a waste of area and remeber....... major cost of such a large settlement will be building it (material wise) coz we need to take things from earth to L5 or L4 which will prove costly... moreover, more nitrogen requirement means more rounds to and fro from earth.
Regards
Anuj Madan

"Combs, Mike" wrote:
From: Anuj Madan [mailto:anujmadan_pec@...]

> I would like to ask about the requiement of elevators in
> Stanford Torus. It is clear that elevators would be required
> in the Torus for transporting materials to and fro from the
> docking facilities. But I think this holds true for Bernal
> Sphere also as one would always require an elevator in it
> for the same purpose as docking facilities are once again in
> zero-g or micro-g region.
>
> In this aspect, i think Bernal sphere doesn't prove to be
> better than Stanford Torus... What do you say ?

I'm sure that routine traffic will use some kind of tram, or in some
simpler arrangement chair-lifts on cables. But O'Neill's point was that
if the power went out in a Bernal Sphere, you could start walking uphill
toward one of the two "poles" of the sphere. Towards the end of your
journey, you'd be more-or-less climbing straight up, but by that point
you would only weigh a few pounds, and so probably would be having no
problems continuing your ascent.

In a Stanford Torus, one might possibly have a spiral staircase or
ladder in the spokes adjacent to the elevator shafts. But that would be
a ladder half a mile long, and lord knows how much longer the spiral
staircase would be. People stopping from exhaustion would be creating
traffic jams (people ascending to the spin axis of a Bernal Sphere would
be coming in radially from all directions). Maybe if you were losing
weight with each step, it might not be as unmanageable as it would seem
from our Earthly perspective. But walking up a much shorter hill sure
sounds a lot easier.

Regards,

Mike Combs

On Tue, 19 Oct 2004 17:19:55 +0100 (BST), Anuj Madan
wrote:
(...)
> If the power goes out, why would one need to go to the dock or zero-g regoin. We cannot afford for the power to go out... coz if it goes out, there will be no communication with space vehicles and hence docking will not be possible, be it Bernal sphere or torus.
(...)

There could be manual docking options for emergencies like a total
power shutdown. As far as I vaguely remember, along much of the 60's
docking oif spaceships was manually/visually guided and the mechanisms
of many air locks were also manual. Oh, and communication was of an
awful analogical kind. :-)

> From: Lucio de Souza Coelho [mailto:lucioc@...]

> There could be manual docking options for emergencies like a total
> power shutdown. As far as I vaguely remember, along much of the 60's
> docking oif spaceships was manually/visually guided and the mechanisms
> of many air locks were also manual. Oh, and communication was of an
> awful analogical kind. :-)

I imagine that if power went out they'd use battery or wind up radios.

ANTIcarrot.

From: Anuj Madan [mailto:anujmadan_pec@....in]

> If the power goes out, why would one need to go to the
> dock or zero-g regoin.

To get the heck out. What's being thought about here is a scenario of a
catastrophic disaster which requires evacuation of the population under
conditions where we may or may not be able to count on the electrical
utilities.

> We cannot afford for the power to go out... coz if it
> goes out, there will be no communication with space
> vehicles and hence docking will not be possible, be it
> Bernal sphere or torus.

In a situation like this, we wouldn't be thinking about ships coming in
and leaving with people. We'd be thinking about getting to life boats
of some type.

> I think one should not choose Bernal sphere keeping in
> mind this constraint

I'd agree that constraint all by itself should not be a reason to make
such a decision. I just threw it out as one more thing O'Neill didn't
care for about the torus.

> coz sphere seems to be useless... its such a waste of
> area

On that point I would have to beg to differ. I think you're thinking
that any of the sphere's inner surface beyond 45 degrees will be
useless. It may not see residential development, but I would still
argue there's reason to expect buildings housing low-G areas which will
provide both entertainment and practical uses. As an example of the
latter, wouldn't it be nice if a facility for the care of the infirm
only had 1/4 or 1/5 gravity?

> and remeber....... major cost of such a large
> settlement will be building it (material wise)

Which might well be an argument for the shape which encloses the maximum
amount of volume with the minimum amount of surface area. The lion's
share of our material budget will be for the radiation shield, and that
will vary by the surface area.

> coz we
> need to take things from earth to L5 or L4 which will
> prove costly... moreover, more nitrogen requirement
> means more rounds to and fro from earth.

Perhaps, but perhaps not. If we go the NEO route rather than the lunar
one, there may be sufficient supplies of nitrogen from asteroidal
material to eliminate, or at least vastly reduce, the requirement for
shipment from Earth.

We may find that with a larger volume of air relative to our population
that it's easier to maintain a balanced ecology without rapid swings in
air composition.

I have no doubt that a person would feel more like they were "outside"
with wide open spaces overhead than with the Stanford Torus' glass
ceiling only a few meters overhead, despite the Bernal Sphere's smaller
diameter. How many times have we heard space habitats disparaged as
"like living in a shopping mall for the rest of your life"? I guarantee
you those making that disparagement are looking at the Stanford Torus
design, not the other ones.

Regards,

Mike Combs

Combs, Mike wrote:

"I have no doubt that a person would feel more like they were "outside"
with wide open spaces overhead than with the Stanford Torus' glass
ceiling only a few meters overhead, despite the Bernal Sphere's smaller
diameter. How many times have we heard space habitats disparaged as
"like living in a shopping mall for the rest of your life"? I guarantee
you those making that disparagement are looking at the Stanford Torus
design, not the other ones."

Wouldn't it be kind of weird to have people above your head, i.e. on the
other side of the sphere?
Also, if we construct decks as you proposed won't only a fraction of
people (the ones who live/work on the uppermost deck) get to see the
open space above them, i.e., the sky?

Thanks and regards
Saatvik Agarwal