Large aquaria are made of acrylic, rather than glass. Acrylic windows can hold tremendous pressure, and (I believe) are more resistant to breakage from impact too.
Thank you,
- Joe
Joe Strout -- joe@...
Large aquaria are made of acrylic, rather than glass. Acrylic windows can hold tremendous pressure, and (I believe) are more resistant to breakage from impact too.
Seems like most all of the peer-reviewed space habitat designs have assumed use of glass. I strongly suspect this is because when we're talking about needing something by the square mile, we'd darn well better be talking about the cheapest substance with the simplest materials processing which can do the job. One reason why I suspect that even if habitats similar to what Marshall Savage proposes ever get built, they'll be made from steel I-beamsand glass panels, rather than the cable-reinforced silicone plastic Savage recommends.
Regards,
Mike Combs
>Behalf Of joe@...
>
>Large aquaria are made of acrylic, rather than glass. Acrylic
>windows can hold tremendous pressure, and (I believe) are more
>resistant to breakage from impact too.
>
>Has anyone looked at the possibility of manufacturing acrylic in
>space, for use instead of glass for windows that must contain
>pressure? What are the advantages and disadvantages as compared to
>glass?
>
sunlight better than plastics.
Don
> Seems like most all of the peer-reviewed space
> habitat designs have assumed use of glass. I strongly suspect this is
> because when we're talking about needing something by the square mile, we'd darn
> well better be talking about the cheapest substance with the simplest materials
> processing which can do the job.
Of course, I'm sure there are cheaper sources for bulk glass, but then that's probably true of acrylic too; I just quoted the first source I could find of sheet/bar/rod stock.
On the other hand, I have a vague idea how glass is made; I have no idea how acrylic is made and whether it would be a good fit for space processing or resources. But if the production process were a lot more expensive (on Earth) than that for glass, you wouldn't expect to be finding it so cheap.
I wonder if perhaps acrylic wasn't well known in the 1970s, so glass was assumed, and now it's just a matter of habit?
Best,
- Joe
[1] http://www.scicominc.com/plastic_sheet_stock.htm
[2] http://www.waleapparatus.com/walestore/SearchResult.aspx?CategoryID4
Joe Strout -- joe@...
Acrylic would require an extensive in space
infrastructure to manufacture as well as shipment to
orbit of large quantities of specialized materials.
Glass could be made in situ from available materials,
ie, the SiO2 in asteroids/lunar regolith and from
available solar radiation, ie, at 1400 watts/m2
there's pleanty of heat available for melting the rock
with a 100 m2 collecting surface. Check out
MythBusters use of flat mirrors to ignite a wooden
boat 100 feet away.
>
> > Seems like most all of the peer-reviewed space
> > habitat designs have assumed use of glass. I
> strongly suspect this is
> > because when we're talking about needing something
> by the square mile, we'd darn
> > well better be talking about the cheapest
> substance with the simplest materials
> > processing which can do the job.
>
> That sounds sensible, but I'm having trouble backing
> it up with figures. A square foot of 0.5" acrylic
> sheet is $10.50, which works out to about $8900/m^3
> [1]. A 15 mm rod of clear fused quartz glass is
> $26.70/foot, which works out to over $495000 (yes,
> half a million!) per m^3. A case of Pyrex glass
> rods is $111, and works out to $22000/m^3 -- a lot
> cheaper than fused quartz, but still about 2.5 times
> more expensive than acrylic.
>
> Of course, I'm sure there are cheaper sources for
> bulk glass, but then that's probably true of acrylic
> too; I just quoted the first source I could find of
> sheet/bar/rod stock.
>
> On the other hand, I have a vague idea how glass is
> made; I have no idea how acrylic is made and whether
> it would be a good fit for space processing or
> resources. But if the production process were a lot
> more expensive (on Earth) than that for glass, you
> wouldn't expect to be finding it so cheap.
>
> I wonder if perhaps acrylic wasn't well known in the
> 1970s, so glass was assumed, and now it's just a
> matter of habit?
>
> Best,
> - Joe
>
> [1] http://www.scicominc.com/plastic_sheet_stock.htm
> [2]
>
http://www.waleapparatus.com/walestore/SearchResult.aspx?CategoryID4
Maybe there are some VVD fans here who can ponder this weird idea I've
gotten.
depositing sapphire? If not, is there anything I can do to my vacuum
vapor depositing maching, or to the vapor it deposits, so that it IS
depositing sapphire? I occurs to me that sapphire might be a
wonderful material for certain uses, such as windows.
What about this: deposit multiple layers of sapphire, until it is
about ten microns thick, then wrap the structure (I'll assume a
Stanford Torus spoke) in a ten micron diametre strand of anhydrous
glass. Wind it tight, and go over it again with the VVD machine until
you've built up another ten microns of sapphire, then wind it tight
with...
Do this until you have a ten centimetre thick shell. Then put a
millimetre thick coating of regular aluminum on the inside and outside
surfaces. Or maybe not. Hey, would this composite glass/sapphire
material be transparant?
Acrylics contain a lot of hydrogen and carbon. If lunar resources are used these are relatively scarce.Asterodal materials would make acrylics more doable.
From Wikipedia---
"To produce 1 kg of PMMA, about 2 kg of petroleum is needed. In the presence of air, PMMA ignites at 460 C and burns completely to form only carbon dioxide and water"
> Seems like most all of the peer-reviewed space
> habitat designs have assumed use of glass. I strongly suspect this is
> because when we're talking about needing something by the square mile, we'd darn
> well better be talking about the cheapest substance with the simplest materials
> processing which can do the job.
That sounds sensible, but I'm having trouble backing it up with figures. A square foot of 0.5" acrylic sheet is $10.50, which works out to about $8900/m^3 [1]. A 15 mm rod of clear fused quartz glass is $26.70/foot, which works out to over $495000 (yes, half a million!) per m^3. A case of Pyrex glass rods is $111, and works out to $22000/m^3 -- a lot cheaper than fused quartz, but still about 2.5 times more expensive than acrylic.
Of course, I'm sure there are cheaper sources for bulk glass, but then that's probably true of acrylic too; I just quoted the first source I could find of sheet/bar/rod stock.
On the other hand, I have a vague idea how glass is made; I have no idea how acrylic is made and whether it would be a good fit for space processing or resources. But if the production process were a lot more expensive (on Earth) than that for glass, you wouldn't expect to be finding it so cheap.
I wonder if perhaps acrylic wasn't well known in the 1970s, so glass was assumed, and now it's just a matter of habit?
Best,
- Joe
[1] http://www.scicomin c.com/plastic_ sheet_stock. htm
[2] http://www.waleappa ratus.com/ walestore/ SearchResult. aspx?CategoryID= 134
Joe Strout -- joe@...
http://www.verex. com/
You might be onto something with the plastic idea. There are people at
NASA-MSFC doing research on a variation of polyethylene that's good
both for structural uses and radiation shielding:
http://www.firstscience.com/site/articles/plasticspaceships.asp
radiation shielding. According to the article, lighter elements make
better radiation shields. Hydrogen or water are ideal, but polyethylene
is the best solid material. (Also according to the article, magnetic
shields could be less massive, but the technology isn't quite ready,
and the electric field based shields that have been getting a lot of
attention lately have approximately zero chance of being feasible.)
It's possible to produce transparent polyethylene, so it might make
good windows?
-Phil
There is one possible problem with using plastic rather than glass. I have
had dealings with armoured cars and the ballistic "glass" in the windows is
made from a polycarbonate. We had to build sun shades for the cars to be
parked under when not used in order to extend the life of the polycarbonate
because it degrades in the sunlight, I seem to recall reading that it is the
UV in the sunlight that does it. In orbit the sunlight will be stronger and
the UV very much stronger. Are there any transparent plastics that are not
effected by UV light? If not, perhaps a layered system will need to be used,
high strength plastic with a layer of UV protection above it.
Glass is better made in zero-G
http://science.nasa.gov/headlines/y2003/14apr_zeroglass.htm?list945567
Acrylic isn't as heat resistant as glass.. easily loses its shape at 200 degrees.
But it all depends on what you want to use it for.
For the hull of space crafts and adding radiation shielding ANYTHING can be used for shielding if you have enough of it.
For suits and crafts and vehicles that must move around and join or enter another larger craft, the ideal shielding would be Gold which is abundant on many asteroids and asteroid Gold is near 100% pure 24 karat. Easy to process, mold, etc.
To compare Acrylic to Glass for hull making, you need to find out what thickness of each attains the same shielding strength and then compare the costs of each. Of course, if launching from earth, the cost figuring is heavily colored in one shade or another.
Manufacturing would start out much the same as earth and develop further with testing of different applications of zero-G, multiple spinning speeds and concepts, etc.
George
cygo.com
There is one possible problem with using plastic rather than glass. I have
had dealings with armoured cars and the ballistic "glass" in the windows is
made from a polycarbonate. We had to build sun shades for the cars to be
parked under when not used in order to extend the life of the polycarbonate
because it degrades in the sunlight, I seem to recall reading that it is the
UV in the sunlight that does it. In orbit the sunlight will be stronger and
the UV very much stronger. Are there any transparent plastics that are not
effected by UV light? If not, perhaps a layered system will need to be used,
high strength plastic with a layer of UV protection above it.
Darren
Gold would be a very bad material to use as radiation
shielding, due to the secondary radiation that would
be induced. It would be much better to use lighter
elements like silicon, carbon, hydrogen, and oxygen.
Water, paraffin and plain old lunar regolith would
probably be the best materials to use in terms of
limiting secondary radiation.
first discovery of large amounts of gold found on
asteroids would be sufficient to start a gold rush,
which would be the incentive to start large scale
space colonization.
Ed
I'm sorry, Ed, but Gold is the best, then Lead. Lead is excellent for X-ray and Gamma radiation. Actually, you can use most anything. Earth has miles of atmosphere. You just, for example, can't put two meters of regolith between your fingers. It just doesn't work.
In space, more valuable than Gold and PGM, or anything, is water.
George
cygo.com
Gold would be a very bad material to use as radiation
shielding, due to the secondary radiation that would
be induced. It would be much better to use lighter
elements like silicon, carbon, hydrogen, and oxygen.
Water, paraffin and plain old lunar regolith would
probably be the best materials to use in terms of
limiting secondary radiation.
However, gold would have its uses. I think that the
first discovery of large amounts of gold found on
asteroids would be sufficient to start a gold rush,
which would be the incentive to start large scale
space colonization.
Ed
George, Gold and Lead are the absolute worst radiation
shields you could come up with. Sure, they will stop
the primary high-energy particles and radiation;
however, the act of stopping those high energy
particles and radiation creates a shower of secondary
particles that will cook you in seconds. When a high
energy particle (say an alpha particle from the solar
wind) strikes an atom of Lead, the initial particle is
stopped, but the Lead nucleus is shattered, sending a
cascade of lower-energy (but still lethal) particles
and radiation into your habitat. The absolute best
radiation shielding is made of low atomic weight
materials, and lots of them. That way you stop the
primary radiation without generating secondaries. The
radiation shielding would have to be much thicker if
it was made of hydrogen (or more likely: water,
hydrocarbons, or silicates), but the total mass per
square meter of surface area would be the same.
Ummm, gold, soft and yellow,,,
was a great discovery. Had it stayed there it might
have been. But the recovery and transport of gold to
Spain resulted in economic collapse, as the price of
gold tumbled. Gold and other rare earths are valuable
ONLY because they are rare. Quadruple the supple and
the price drops proportionately.
Gold has few industrial applications. Most is used in
jewlery and there are only so many people to buy it.
All resource value is dependent upon rarity and the
energy to extract, refine and transport is all that
makes it costly.
In space, the energy is free. It just costs money to
convert it to an industrially useful form.
In space, all recources are free. It just takes energy
to get to them.
The energy investment to produce, transport etc is the
sole basis for cost/value and should be the basis of
any economy.
,,,it ALL comes back to energy,,,and the knowledge to
use it.
GAry 7