Hi,

I plugged in a population of 30,000 in the Belmont calculator and
surprisingly the cylinder required the least radiataion shielding.
The tours required something like 70 megaton, the sphere around 46
megaton and the cylinder only 4 (yes that's four) megaton.
Is this true or is there a bug in the calculator? If this is true why
was the cylinder eliminated for such small population sizes?

Thanks and regards
Saatvik Agarwal

Sounds like a bug. Even if they're neglecting to shield the endcaps
(perhaps not a good idea at the smaller end of the range), I still can't
see it being that big a difference.

Regards,

Mike Combs

From: Saatvik Agarwal [mailto:asaatvik@...]
Sent: Wednesday, October 20, 2004 11:11 AM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Cylinder

Hi,

I plugged in a population of 30,000 in the Belmont calculator and
surprisingly the cylinder required the least radiataion shielding. The
tours required something like 70 megaton, the sphere around 46
megaton and the cylinder only 4 (yes that's four) megaton.
Is this true or is there a bug in the calculator? If this is true why
was the cylinder eliminated for such small population sizes?

Thanks and regards
Saatvik Agarwal

Would you please supply the dimensions of the sphere and cylinder that
you're using, so that we can check the calculations?

Anyhow, the sphere beats the cylinder only if one assumes that the
population is distributed along the volume. (Because the sphere has
the highest volume-to-surface ratio.) If one assumes that the
population is distributed along the *surface*, though, then I think
that the cylinder is the best option, because in the cylinder (if you
do not consider the endcaps) the ratio of shield surface to usable
surface would be 1 and in the sphere it would be higher than 1.

So, I tend to think that spheres would be better for arcology-like
colonies - big rotating 3D cities - while cylinders would be better
for really "earth-like" colonies with forests and hills and stuff.

On Wed, 20 Oct 2004 21:41:14 +0530, Saatvik Agarwal
wrote:
>
> Hi,
>
> I plugged in a population of 30,000 in the Belmont calculator and
> surprisingly the cylinder required the least radiataion shielding.
> The tours required something like 70 megaton, the sphere around 46
> megaton and the cylinder only 4 (yes that's four) megaton.
> Is this true or is there a bug in the calculator? If this is true why
> was the cylinder eliminated for such small population sizes?
>
> Thanks and regards
> Saatvik Agarwal
(...)

Yup, it's a bug. It divides by one extra zero to convert shielding mass
from tons to megatons in case of a cylinder.
For all other shapes it divides by the normal 10^6.

Regards
Saatvik Agarwal

Combs, Mike wrote:

Saatvik Agarwal wrote:

"I plugged in a population of 30,000 in the Belmont calculator and
surprisingly the cylinder required the least radiataion shielding.
The tours[sic] required something like 70 megaton, the sphere around 46
megaton and the cylinder only 4 (yes that's four) megaton.
Is this true or is there a bug in the calculator? If this is true why
was the cylinder eliminated for such small population sizes?"

Bearing in mind that someone else has said that the calculator has a bug
(and adjust the decimal point accordingly) -- for a habitat of 30,000 people
I shrunk the size of the cylinder until it had a diameter of 1km and a
length of 1km (as wide as it is long; any wider/shorter and it'd be a torus
w/o the hole) and came up with a set of stats. I then shrank the sphere
until I had the equivalent area per person (104.5 persons per m^2 +/- in
this case, and the sphere had a radius of 705 meters) to arrive at a second
set of stats.

The totals were 24,778 kt for the cylinder, and 31,861 kt for the sphere:
total savings of 6883 kt if the cylinder design is chosen.

The cylinder had 7600 kt less in shielding than the sphere. In fact, the
only benefit to the sphere is 1112 kt less in structural mass.

I could design a cylindrical habitat for 10,000 people, but it'd be a
spinning disk. Might as well save money by making it a donut -- now you've
got a torus. But the torus is expensive to provide sheilding for, so its
back to either the sphere or the squashed cylinder.

Dont just search. Find. Check out the new MSN Search!

The calculator is misleading - you see when it calculates the are for
any shape it calculates the surface area of the entire figure, i.e. it
ends up counting area which will not be inhabited.
Now you say we can save money by making the cylinder/disk into a torus.
This is true, if you use a torus you will end up saving money. The
height of the cylinder or the outside side of the torus is actually your
floor and to make a torus into a cylinder you decrease its radius to 0
(the distance between the center and the inner edge of the torus, note
not the tube radius, we are actually increasing the tube radius). So you
get more 'height' by converting the same torus into a cylinder but not
more surface area.

What I've said is probably very confusing...just my two cents

Regards,
Saatvik Agarwal

Michael Capriola wrote:

Saatvik Agarwal wrote:

"Now you say we can save money by making the cylinder/disk into a torus.
This is true, if you use a torus you will end up saving money. The
height of the cylinder or the outside side of the torus is actually your
floor and to make a torus into a cylinder you decrease its radius to 0
(the distance between the center and the inner edge of the torus, note
not the tube radius, we are actually increasing the tube radius). So you
get more 'height' by converting the same torus into a cylinder but not
more surface area."

Actually, the cylinder/disk has a lot of wasted space because of its
'height,' but the torus design is actually MORE expensive because of
shielding requirments.