From: The Butterfly (salsbury_at_bootstrap.sculptors.com)
Date: 04/19/98
Date: Sun, 19 Apr 1998 18:56:21 -0700 Message-Id: <199804200156.SAA26422@bootstrap.sculptors.com> From: The Butterfly <salsbury_at_bootstrap.sculptors.com> Subject: Re: Been kinda quiet, lately...
-From: Chris_McCoy_at_sigmanet.com
-Date: Thu, 16 Apr 1998 11:20:15 -0700
-
-Airship size is only limited by the strength of structural materials.
-At 1mile in diameter, you have enough lift to build a relatively strong
-structure.
-I have heard a few people talk about using reinforced concrete members once
-a ship reaches a certain size.
UGH!
Why the hell does everyone like reinforced concrete so much? It's a
really lousy material for dynamic structures, and has almost no tensile
strength to speak of, which you'll need LOTS of in an airship, or just a
regular ship. Almost any tensile strength comes from the steel in it, not
the concrete.
Concrete is very good for *compressive* structures. When you pile
one stone on top of another. But for *tension* you want to have metals or
polymers or graphite, or something similar.
Suspension bridges are built with metal cables holding them up. Not
with concrete ropes. :-)
OK, enough materials properties lecture. It's just that, after a
decade of studying the "more with less" principles of Design Science, it
really irks me to see people equate "strong" with "reinforced concrete."
:-)
-Remember, once you get over a 2.5km diameter you are talking appx 25,000
-tons of lift!!
-If you had an airship that size, say 10km in diameter and 1km thick, you
-could concievably
-put a small town on it. Like a current high-rise construction. Companies
-could build floating
-complexes that housed thousands. If you could use standard construction
-materials, you
-could use many of the same craftsmen. The size would make it possible to
-over-engineer, and
-not worry about the payload loss.
I love the general idea, but I would point out that "standard
construction materials" like concrete and gypsum board and the like are
EXTREMELY heavy. A conventional single-family dwelling weighs in at about
45 tons. They were never designed to leave the earth, so weight was never
taken into consideration.
To redesign for flight means to step away from all that is
traditional in building construction, and to rethink everything. It's
necessary, and worth it. :-)
-Remember though, this is all fine and good, but you need to walk upright
-before you can
-fly at super-sonic speeds. We have a long way to go.
-
-Chris
Yes, and also, it's good to keep in mind that technology is
advancing at an ever-accellerating rate. To design something for the future
using todays standards is to build in obsolescense from the get-go.
Instead, I like to employ the technique of looking ahead to when
you want your finished product, and design to take advantage of
technological advances as they come. Essentially, you pick your point in
time, and design to *intercept* that point, rather than designing to carry
forward some old tech from what is now current time.
It's an odd concept, but to put it into real-world terms, think of
it this way:
If you're going to write a software program, and you think it will
take about 5 years to complete, then it makes NO sense to design it in a
way that requires it to run on a specific "state-of-the-art" architecture
when you begin. You design it open-ended, to take advantage of advances
that you know will come.
If you had started 5 years ago, you would have built in dependancy
on a 386 or 486 chip, while today we have Pentium II's.
See what I mean? If you generalize the principle, you know you'll
need gas bladders and rigid frames and outer skins that are UV-tolerant. Up
until the actual time of construction, though, the moment when you decide
to cast the design in matter, not digital models or strategic planning like
we're now doing, you probably want to avoid committing to one specific
material, since something new will come along.
--
Pat
___________________Think For Yourself____________________
Patrick G. Salsbury - http://www.sculptors.com/~salsbury/
Check out the Reality Sculptors Project: http://www.sculptors.com/
---------------------------------------------------------
Death is life's way of telling you you've been fired.
-- R. Geis