[ExI] Inflatable tower could climb to the edge of space
spike66 at att.net
Thu Jun 11 05:06:45 UTC 2009
> ...On Behalf Of spike
> Subject: Re: [ExI] Inflatable tower could climb to the edge of space
> > -----Original Message-----
> > From: extropy-chat-bounces at lists.extropy.org
> > [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf
> Of spike ...
> > The blocks: I have imagined them as hexagonal things, like
> those old
> > fashioned six sided wooden pencils that some of us used in
> school in
> > our misspent youths, so tragically many years ago... spike
> I didn't intend to suggest making the tower of pencil sized
> blocks, but rather pencil shaped. I have in mind pressurized
> steel hexagonal cylinders about a meter in diameter and about
> 20 meters long, getting shorter as we go up. OK now I really
> do hafta scoot.
Nowthen, to help you visualize what I have in mind, let us imagine a 200:1
scale model, so that the bottom layers would be made of blocks the size of
the afore-mentioned six sided wooden pencils, which are about half a cm
diameter and about 10 cm long for this model. So to visualize the tower,
imagine placing the pencils adjacent in a ring about five meters across, so
that it would actually fit in your living room if you moved all the
furniture out of there. All the pointy ends point toward the center for
this thought experiment.
It would take 3142 pencils to complete the ring. A flat side is adjacent to
the floor, so flat sides are on top. Since the inner diameter is about 4%
less than the outer diameter, assume a special kind of pencil that is
gradually tapered, slightly smaller on the pointy end. This is important,
for if this tower is to work right, everything must touch with close
tolerances, for there is to be a direct and minimal load path to the ground,
to support all this weight.
To create the next layer, another 3142 pencils are needed, but these are all
rotated by pi/6, or 30 degrees about the long axis. They still all point to
the center but they stack on top of the previous ring. So now, on the
second layer, there are two vertical sides and two edges top and bottom.
The second layer is very slightly shorter than the first, for the thickness
of the cone surface decreases as we go up. The third layer stacks on the
second, and so on. In our 200:1 scale model, the cone is about as tall as a
three storey building. If you are attempting to make a model in your living
room, you will likely need to cut a hole in the roof.
Now back to the full scale, and a comment on the pressurized blocks. I
thought of a way to make these things. They aren't an open cylinder like a
scuba tank, but rather they are compartmented, with reinforcing surfaces
within. Imagine a block, a meter in diameter, twenty meters long, with
outer walls about one cm thick. Now imagine the cylinder divided into about
20 sections each about a meter long, by 18 internal walls, each about six cm
thick. The reason we have those is that they will carry most of the load to
ground. So each cylinder will have a volume of about 15 cubic meters, and
will contain about 1.5 cubic meters of steel, so each will weigh about 12
tons, so it can be handled with ordinary equipment.
The cool part is I have a wild idea on how to actually make these blocks.
We would create a mold with five sides, twenty meters long, the bottom
horizontal. This mold has one removable end, the slightly larger end.
Recall that we need the cylindrical blocks to be slightly larger at one end,
because the inner diameter of the ring being about 20 meters less than the
Next we make 20 thin steel cans, about 98 cm diameter and about 92 cm thick,
so they look a little like those old fashioned canteens some of us used to
carry hiking in our misspent youth, only much bigger of course, hexagonal
instead of round, but made of metal not much thicker than those old
canteens. We support them with a threaded hole from above. Remove the one
end of the mold, insert the cans so that they are about a cm from each of
the walls of the mold, replace the end of the mold. Fill the cans with
water. Pour the mold full of twelve tons of molten iron. The water boils
away out of the cans, cooling the thin metal so that it doesn't melt. After
the iron is frozen, unthread the cans and remove the big end of the mold.
The finished block can be removed from the big end of the mold.
Now you have a building block about 20 meters long with 20 separate
compartments, each with a threaded hole going in, each with a volume of
about .7 cubic meters. Let the block cool. Now you pour each compartment
about a sixth full of liquid nitrogen, or about 120 kg, into each
compartment, and thread a plug into the hole before it boils away. Then
when it reaches thermal equilibrium, you have your 150 atmospheres internal
pressure. (I did the hoop stress calcs and realized you wouldn't want to go
much above about 150 atmospheres pressure if we use steel. 150 atmospheres
below what you can put in a typical scuba tank.)
It comes out to 2.4 tons of nitrogen in that 12 ton block, so fully a fifth
of the weight of this tower would actually be gas. Cool!
Given a conic tower with an electromagnetic rail gun up the side, I think we
could hurl an ablative rocket to enough velocity to push it to orbit
velocity using Keith's laser.
Tower fans, do check my work.
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