From: Chris_McCoy_at_sigmanet.com
Date: 04/20/98
From: Chris_McCoy_at_sigmanet.com Message-ID: <882565EC.00607E40.00@sweb_notes.sigmanet.com> Date: Mon, 20 Apr 1998 11:18:21 -0700 Subject: Re: Been kinda quiet, lately...
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.
***Point taken. I would have to agree with you as far as tensile strength,
but the flaw
is in assuming that I was endorsing it. I was stating a fact. Wether I
agree with it or not
is another matter. In this case, I want to see as many people in the air as
possible.
Concrete is very heavy. If I use a lighter material, I can add more people.
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.
***When I say materials, I should have been more specific. Josh can back me
up here.
Off the shelf is my real meaning. You will see me use this term often. If
any idea like this
comes into existence, you want to spend your money on making it, not
researching
wether nanotubes will hold up to a plus/minus stress of xG's when built in
a certain config.
Off the shelf means cutting-edge, but with enough data do eliminate
excessive failures.
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.
*** This goes back to my last comment. Any technology, sufficently
advanced, appears
as magic to the layman. If you design any product around a laboratory
result, you have to
be prepared to completely scrap that product and start over when imperical
evidence
proves the original hypothesis incomplete or wrong.
*** If you had decided to design your ship in the 60's, you might have
decided that titanium
would have been the cornerstone of your construction materials. All reports
were that it was
stronger than steel and that engineers would find easy ways to shape and
use it by the time you
actually built. You would have measured everything out for a hull made of
titanium. Lift, passengers,
payload are now all fixed items, perfectly calculated. Then you show your
"cutting edge"
design to an investor, who is willing to spend $x.xx to build this ship.
You get the go ahead, but
need to wait a few more years, as titanium is still too hard to shape and
use due to it's brittle nature.
You wait a few more years, then find out that the process will be too
expensive for at least
another ten years. Now your investor is getting impatient. You are forced
to try a re-design.
In the end your design must use aluminium, be heavier, and carry less. Your
discouraged
investor cut's his losses, and pulls the plug. Had you used aluminium, and
it's scores of data,
you would be able to have a "build now" attitude. Had titanium proved to be
better, it would be
easier to UPGRADE your design and reap the benefits then DOWNGRADE, and
loose
performance.
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.
***This is an ideal, not the way it actually works. You code with the
language in mind.
The kernal used was the same until W95. That kernel is still the standard.
Thats 3 years
with no significant change.
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.
*** But by then, it may be too late.
Chris