Window dimensions. Forum: Spacesettlers
Thread: Window dimensions.
--- In spacesettlers@y..., "victoriatangoman"
> The problem with relying on "appeal to authority" type arguments
is
> that there is no independent verification of results. While I
admire
> the work that Dyffed Neal Dyar did on his web page, I think it is
> troubling to be relying on the physics underlying a sci-fi site.
>
> Let's look at a few numbers to try to come to a better
understanding
> of the thicknesses involved in the pressure shell and the windows.
>
> The 50 feet of mooncrete and 40 feet of windows don't ring true
for
> me. When I consider the thickness of radiation shielding for a
> nuclear power plant and compare it to the above thicknesses, I'm
led
> to believe that something is askew.
>
> Also, the mass involved is staggering. Consider:
>
> 4*pi*r2 is surface area of sphere.
> 2*pi*r*L is surface area of a cylinder
>
> r = 2 miles * 5,280 feet = 10,560 feet
> L = 20 miles * 5,280 feet = 105,600 feet
>
> Two endcaps = 1,401,885,257 ft2
> Cylinder = 7,009,426,286 ft2
>
> The endcaps have no window area so they are 50 ft thick, thus
there
> is 70,094,262,860 ft3 of material.
>
> The cylinder is half window and half shell, therefore
>
> 3,504,713,143 ft2 * 40 = 140,188,525,700 ft3 of glass
> 3,504,713,143 ft2 * 50 = 175,235,657,100 ft3 of slag.
>
> Altogether, that is a volume of material, just for the shell not
> including any buildings or support structure insided the habitat
nor
> exterior mirrors and farming modules, of 385,518,445,086 ft3 of
> material.
>
> If we assign a mass of 173.9 lbs/ft3 (lunar regolith) to that
volume
> we end up with a mass of 33,523,343,040 tons.
>
> If we assume that this material must be launched from the surface
of
> the moon over a period of 20 years, then we're launching 53.1509
> tons per second, every second for that 20 years.
>
> Considering that 1 ft3 of lunar regolith takes 374 MW of energy to
> propel up to the 3000 m/sec escape velocity, the power required to
> launch that 53 tons per second will have to be 228.6 GW.
>
> That power has to be a good portion of what is available on the
> earth right now!!
>
> ALso, if the payload size from the mass launcher is no smaller
than
> 1 ft3, then we'll have to have 611 mass launchers firing once a
> second with no downtime at all for 20 years.
>
> For me to buy into the 50 ft/ 40 ft scenario, I'd have to be
> convinced why a habitat would need more shielding that a nuclear
> power plant, and even if I was convinced on that point, I'd then
> have to conclude that an Island 3 would never be built. EVER.
> Because the economics just wouldn't work based on the scale of
> operation I've just outlined. Even if you could get 5,000,000
> people living in it. That would be, at most, a productive
workforce
> of 3,000,000 people. That would mean constructing a mass of 11,174
> tons of material per "economic person." Assign your own value to
the
> cost of that material - I just can't see it.
how about 2 cents per kilowatt hour. 1 ft3 of lunar regolith at 374
MW, would take 103.89 kilowatt hours, for a cost of energy of 2.08
dollars. 11,174 tons per person would cost $266,996.52 JUST for the
energy to propel the mass of the payloads off of the lunar surface.
Now factor in the mining, base maintenance, SMF, fabrication costs,
etc. No, the 50ft/40ft model is too scaled up. It's overkill.
>
> No, I think that Dyffed Neal Dyar is wrong with respect to his
> physics. Proposing radiation protection greater than that for
> nuclear power plants makes his whole scenario wrong. But he does
> have a nice site where he pulls together information and tries to
> address real world feasability issues. But he shouldn't be taken
as
> an authority and used to buttress arguments.
>
> --- In spacesettlers@y..., "tomexe" wrote:
> > --- In spacesettlers@y..., "Combs, Mike" wrote:
> > > From: tomexe [mailto:tomexe@a...]
> > >
> > > But I for one have found the idea of storing water over the
> windows
> > > would serve as a radiation modifier, and would probably
produce
> > > more "natural" weather patterns inside the colony.
> > >
> > > Perhaps, but if at a high-orbital construction site, between 1
> > million tons
> > > of water, and one million tons of slag, I know which is going
to
> > cost more.
> > >
> > > Regards,
> > >
> > > Mike Combs
> >
> > Well here is the thing. I have been visiting this website
> > http://silver.neep.wisc.edu/~neep533/neep533.html at the
> > University of Wisconsin for information about space
construction.
> I
> > frequently refer to the lectures of 17 Feb, and 15,17,19 March.
> Its
> > three years old now, but it still seems to be a good site. At
> least I
> > havent found a better one yet in scouring the internet.
> >
> > Acording to this, given the availability of enough electricity,
to
> > produce heat, water is not hard to come by on the moon. It can
be
> > acqured from the lunar soil.
> >
> > Slag may be what the solid areas of the colony are made out of.
> This
> > same design that has 40 foot thick glass windows also has 50ft
of
> > mooncrete or or slag bricks or both, making up the structure of
> the
> > solid panels and end caps. The actual thickness is actually more
> than
> > 50 feet because of access tunnels, but any partical trying to
get
> in
> > would have to pass through 50 feet of materaial-before coming
into
> > contact with the landscaped topsoil yet. While particles trying
to
> > get in on the windows would have to pass through 40 feet of
glass
> and
> > 4 miles of atmosphere to get to a person on the surface even
> without
> > water over the windows. Also the glass can be made denser than
> just
> > pure silicon. Leaded crystal, which mixes a couple percent of
> > powdered lead with the sand, also has good light transmission
> > qualities and would be denser.
> >
> > Water may be more expensive to gather in the short run, but it
is
> > reuseable, and has a lot of other functions than being a
radiation
> > blanket. It can be used to transport heat energy through the
> colony,
> > from the sunward endcap and the cylinders in the factory ring,
> back
> > to the cold endcap, moderating temperatures and also creating a
> > current which could be tapped to provide even more electricity.
> Using
> > the mirrors as resevours would also humidify the atmosphere
> inside,
> > producing clouds and rain, a more natural habitat for the
people,
> > plants and animals inside. The free water vapor would serve to
> > thicken the atmosphere inside and act as a further barrier to
> > radiation.
> >
> > If you go to this page:
> > http://silver.neep.wisc.edu/~neep533/LEC16/0slide.html the
> last
> > half dozen slides (47-53) have charts that explain the amount of
> > cosmic background radiation exposure that a astronaut recieves
on
> > three different missions, one to a space station, one to the
moon,
> > and one to Mars, in a "standard" spacraft hull of 2g/cm2
Aluminum