What effect will radiation have on the structure of the habitat?

Consider that space vehicles degrade in performance as a function of
time the radiation they receive.

Will the habitat need to be maintained like a ship (40 years between
major overhauls or scrapping) or an airplane (also about 40 years
before metal fatigue necessitates structural replacement.)

What effect will the radiation in space have on the crystal bonds
within the metal or concrete of the shell?

Do you think that the shielding will degrade but that won't matter
because it won't serve a structural function and the shell of the
habitat will be protected by the shielding?

What does this say about designs that may want to incorporate the
mass of shielding into the structure of the habitat rather than have
it seperate?

Do you think that the habitat will have the maintenance problems of
ships and aircraft? I don't mean the sewer, electrical etc. I mean
the actual structure of the habitat. If so, then I fear it may be a
white elephant. Can you imagine having to repurchase the land your
house, business is on every 40-100 years? That's what a major
overhaul would amount to.

From: "victoriatangoman"
To:
Sent: Friday, July 19, 2002 12:08 PM
Subject: [spacesettlers] Radiation Fatigue?

> What effect will radiation have on the structure of the habitat?
>
> Consider that space vehicles degrade in performance as a function of
> time the radiation they receive.
>

Ok, but this performance degrade is due to the impact of radiation in
electronics (I think), not structure.

> Will the habitat need to be maintained like a ship (40 years between
> major overhauls or scrapping) or an airplane (also about 40 years
> before metal fatigue necessitates structural replacement.)
>

I tend to think more of habitats made of concrete or (in the case of very
large ones) "unobtanium" (carbon nanotubes or other supermaterial yet to
become popular) rather than metal. The classical argument favoring concrete
colonies are: (a) metal structures typically last decades, while
stone/concrete structures last centuries and (b) in case of decompression,
metal containers have a tendency to "pop", while concrete containers
preserve their shapes and the extension of fissures. Finally, on Earth at
least economics also favors concrete: the Petrona Towers, for instance, are
the tallest building in the world, but their construction cost was lower
than the WTC, because they are made of a new kind of "superconcrete". (If I
remember correctly.)

My gut feeling is that a metallic colony would need constant maintenance,
while a concrete one would be something to last "forever".

> What effect will the radiation in space have on the crystal bonds
> within the metal or concrete of the shell?
>

I really don't know. However, the gut feeling based on the little knowledge
that I have of chemistry/materials science tells me that crystal (ionic)
bonds tend to rearrange themselves, while covalent (molecular) bonds don't
get together again after disruption. Is my gut feeling wrong or right?

> Do you think that the shielding will degrade but that won't matter
> because it won't serve a structural function and the shell of the
> habitat will be protected by the shielding?
>

I tend to prefer designs where the shielding enveloped the whole colony
(including its structure) and does not rotate, or rotates at a much slower
speed. That decreases a little the structural requirements and also shields
the structure (not only against radiation, but also against impacts) as a
side effect.

> What does this say about designs that may want to incorporate the
> mass of shielding into the structure of the habitat rather than have
> it seperate?
>

I don't know, I have only the aforementioned gut feelings. ;-)

(...)
Lucio Coelho

--- In spacesettlers@y..., Lucio de Souza Coelho wrote:
> From: "victoriatangoman"
>
> > Do you think that the shielding will degrade but that won't matter
> > because it won't serve a structural function and the shell of the
> > habitat will be protected by the shielding?
> >
> I tend to prefer designs where the shielding enveloped the whole
colony
> (including its structure) and does not rotate, or rotates at a much
slower
> speed. That decreases a little the structural requirements and also
shields
> the structure (not only against radiation, but also against
impacts) as a
> side effect.
>
> > What does this say about designs that may want to incorporate the
> > mass of shielding into the structure of the habitat rather than
have
> > it seperate?
> >
> I don't know, I have only the aforementioned gut feelings. ;-)
>
> (...)
> Lucio Coelho

If you are going to build a concrete shield, the inside of the shield
must be built to very tight tolerances, to minimize chances of
impacts with the inner metal hull. The slabs needed will also be
huge. If you are going to all of the trouble of making the shield
anyhow, then you may as well build the whole structure out of
concrete. In the long run it is probably cheaper,in maintenance
costs alone.

:) ed

Our problem is that we haven't settled on a basic shape for the first
few colonies. Will they be spheres, toroids, dumb-bells or cylinders?

If we go right to the large cylinder for first colonies I believe the soil
for
the land area can provide the shield. Circumferential tension cables
can contain the atomosphere & the centrifugal force tending to make
whole thing fly apart. This is analogous to how suspension bridges
use far less steel than truss bridges for the same span.

If the radiation turns out to cause metal fatigue in the cables they could
be put "above" ground with radial cables thru soil to outer skin every
few meters.

Beauty of this approach is that we can forget that 1 kg of regolith shield
per square cm skin area in Al Globus's 7-18 forwarded message.
I hate to see waste & if we build toroid, sphere or dumb-bell shaped
colonies with all that radiation shield then switch to cylindrical with no
radiation shield wouldn't it have been a great waste?

Hallelujah - Praise Spacesettlers ! ! ! Ed S.

Actually, I'm currently thinking a cylindrical or cone-shaped
window running down the central axis of a island 3 shape might
be a good design.

That way, the radiation shielding of the metal/ground is all
around you, and the glass is in a compressive loading rather
than tensile loading (I think it would like that better; then
any cracks will probably hold together, whereas with O'Neills
concept of having it around the edge- it tends to explode
outwards- tends to, although you try to stop it of course.) The
air pressure keeps it in place rather like a huge glass arch-
and the rotation forces are negligable anyway.

You'd let the sunlight in through one end- probably a parabolic
mirror outside would give you a controlled amount of light.

Gains you lots of land, and helps with the radiation problems
too.

Ed Schonert wrote:

> Our problem is that we haven't settled on a basic shape for the first
> few colonies. Will they be spheres, toroids, dumb-bells or cylinders?
>
> If we go right to the large cylinder for first colonies I believe the soil
> for
> the land area can provide the shield. Circumferential tension cables
> can contain the atomosphere & the centrifugal force tending to make
> whole thing fly apart. This is analogous to how suspension bridges
> use far less steel than truss bridges for the same span.
>
> If the radiation turns out to cause metal fatigue in the cables they could
> be put "above" ground with radial cables thru soil to outer skin every
> few meters.
>
> Beauty of this approach is that we can forget that 1 kg of regolith shield
> per square cm skin area in Al Globus's 7-18 forwarded message.

Still, air pressure is atleast twice that... And it might be
easier to just put the habitat in a radiation-shield 'cave'
that doesn't rotate.

> I hate to see waste & if we build toroid, sphere or dumb-bell shaped
> colonies with all that radiation shield then switch to cylindrical with no
> radiation shield wouldn't it have been a great waste?

Not necessarily greatly so. Always melt it all down and start
again. The automation to do this is a wonderful thing.

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

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

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

Do you think that my proposal in message #2236 addresses your
issues. There is also a crude diagram in the files section.

I seem to recall, perhaps incorrectly, that the temperature in the
central "window" cylinder would be immense and that a suitable work-
around has not yet been found. If this isn't the case, then this is
indeed a very elegant solution.

It was this concern that led me to conceptualize my approach.
Granted, it is more complex in design and technology to achieve the
same result as your window cylinder, but it avoids the problem of
the heat from all of the concentrated sulight.

--- In spacesettlers@y..., Ian Woollard wrote:
> Actually, I'm currently thinking a cylindrical or cone-shaped
> window running down the central axis of a island 3 shape might
> be a good design.
>
> That way, the radiation shielding of the metal/ground is all
> around you, and the glass is in a compressive loading rather
> than tensile loading (I think it would like that better; then
> any cracks will probably hold together, whereas with O'Neills
> concept of having it around the edge- it tends to explode
> outwards- tends to, although you try to stop it of course.) The
> air pressure keeps it in place rather like a huge glass arch-
> and the rotation forces are negligable anyway.
>
> You'd let the sunlight in through one end- probably a parabolic
> mirror outside would give you a controlled amount of light.
>
> Gains you lots of land, and helps with the radiation problems
> too.
>
> Ed Schonert wrote:
>
> > Our problem is that we haven't settled on a basic shape for the
first
> > few colonies. Will they be spheres, toroids, dumb-bells or
cylinders?
> >
> > If we go right to the large cylinder for first colonies I
believe the soil
> > for
> > the land area can provide the shield. Circumferential tension
cables
> > can contain the atomosphere & the centrifugal force tending to
make
> > whole thing fly apart. This is analogous to how suspension
bridges
> > use far less steel than truss bridges for the same span.
> >
> > If the radiation turns out to cause metal fatigue in the cables
they could
> > be put "above" ground with radial cables thru soil to outer skin
every
> > few meters.
> >
> > Beauty of this approach is that we can forget that 1 kg of
regolith shield
> > per square cm skin area in Al Globus's 7-18 forwarded message.
>
> Still, air pressure is atleast twice that... And it might be
> easier to just put the habitat in a radiation-shield 'cave'
> that doesn't rotate.
>
> > I hate to see waste & if we build toroid, sphere or dumb-bell
shaped
> > colonies with all that radiation shield then switch to
cylindrical with no

Neat idea, but I don't like taking up the 0g space at the center. It's
too important for recreation. I imagine there must be some way around
this though ...

On Monday, July 22, 2002, at 06:31 PM, Ian Woollard wrote:

> Actually, I'm currently thinking a cylindrical or cone-shaped
> window running down the central axis of a island 3 shape might
> be a good design.
>

Space tourism could be our ticket to the stars. Save your pennies,
suborbital flights for $100,000 may start in 2005! See
http://www.spaceadventures.com/suborbital for details.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

From: "Al Globus"
To:
Sent: Tuesday, July 23, 2002 2:11 PM
Subject: Re: [spacesettlers] Radiation Fatigue?

> Neat idea, but I don't like taking up the 0g space at the center. It's
> too important for recreation. I imagine there must be some way around
> this though ...
[snikt]

You can always put a (lets say) spherical zero-g module behind the mirror,
connected to the one-g module by spokes or something like that.

Lucio Coelho

On Monday, July 22, 2002, at 12:05 PM, Ed Schonert wrote:

> If we go right to the large cylinder for first colonies I believe the
> soil
> for
> the land area can provide the shield. Circumferential tension cables
> can contain the atomosphere & the centrifugal force tending to make
> whole thing fly apart. This is analogous to how suspension bridges
> use far less steel than truss bridges for the same span.
>
The biggest problem, in my mind, with cylinders is that rotation around
the long axis is unstable. A rotating cylinder with more-or-less
uniform mass distribution wants to rotate around the short axis -- this
is not good. One way around this is to hang weights on long cables so
the mass balance favors rotation around the long axis, but don't let
your spacecraft run into these! The could be used as a transportation
system though -- you go out along one to the right place, let go at the
right time, and you've got a lot of velocity in the (hopefully) desired
direction.

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect and
deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Now believe first colonies should be toroid shaped but eventually
we must go to cylindrical to get more land area per ton of structure.
Believe Al Globus' 9-25 comments are saying there's danger the
spin may start to wobble & revert to end-over-end all by itself
throwing everyone to end of cylinder.

Would this danger still exist if cylinders in pairs spinning in
opposite directions? Plate 1 of O'Neill's "The High Frontier"
doesn't show any rigid struts at ends of cylinders to keep them
spaced a fixed distance apart but wouldn't these be required?

Hoping someone can further expand on these aspects.

Hallelujah - Praise Spacesettlers ! ! ! Ed S.

Al Globus wrote:

>The biggest problem, in my mind, with cylinders is that rotation around
>the long axis is unstable. A rotating cylinder with more-or-less
>uniform mass distribution wants to rotate around the short axis -- this
>is not good.
>
Yes, but as O'Neill pointed out, this issue goes away if you have two
counter-rotating cylinders and connect them with a bar at each end.

And they're not THAT unstable anyway individually, I suspect that
there's lots and lots of ways to stabilise them in fact.

> One way around this is to hang weights on long cables so
>the mass balance favors rotation around the long axis, but don't let
>your spacecraft run into these! The could be used as a transportation
>system though -- you go out along one to the right place, let go at the
>right time, and you've got a lot of velocity in the (hopefully) desired
>direction.
>
Possibly, however the rim has a lot of velocity anyway, and the cables
have issues that they are at higher than 1g, which may make them
unpleasant to use.

From: Ed Schonert [mailto:ESchonert@...]

> Plate 1 of O'Neill's "The High Frontier"
> doesn't show any rigid struts at ends of cylinders to keep them
> spaced a fixed distance apart but wouldn't these be required?

There's supposed to be a cable under tension at one end, and a tower under
compression at the other end. But these may be too thin to be legitimately
visible at the range the artist's impression assumed. O'Neill said the
cable under compression would only be about the diameter of a teacup, and
even the tower under compression would be comparable to a radio antenna
mast.

Regards,

Mike Combs

On Wednesday, September 25, 2002, at 11:20 AM, Ed Schonert wrote:

> Would this danger still exist if cylinders in pairs spinning in
> opposite directions? Plate 1 of O'Neill's "The High Frontier"
> doesn't show any rigid struts at ends of cylinders to keep them
> spaced a fixed distance apart but wouldn't these be required?
>

Those pictures are artist conceptions. One should not try to draw ANY
technical inferences from them.

The International Space Station (ISS) most important legacy may be
jump-starting space tourism. Consider: the first space tourist, Dennis
Tito, was supposed to go to the Soviet era Mir space station. Under
pressure from NASA, Russia de-orbited the Mir which resulted in Mr. Tito
going to the ISS instead. Now the Mir was old, smelly, crowded and
probably not all that nice. The ISS was brand new, shinny, much more
roomy, etc. Mr. Tito came back to Earth with glowing accounts of how
great space is. Would his experience have been as good on Mir?

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html