Re: starship-design: HIGHLY OPTIMIZED TOLERANCE

[John Bean <johnbean@ebard.com>]

Ben Franchuk <bfranchuk@jetnet.ab.ca> wrote:
>
>I disagree -- you have to carry a boot strap able system.
>
>All that stuff could fit in a large space craft the catch is it is not
>economic
>to have small systems and you may have to reduce operating perimeters.
>
>Take solid state logic... A portable chip processing plant could
>be table top size, but may have to use 2 inch wafers, be limited to 64kb
>x 1
>dynamic ram,16 bit processors ,or smaller and only produce 256 chips a
>day.
>
I don't know if I agree with the make-everything-myself idea when it comes
to really complicated processes that are really expensive such as chip
making. At some point you need to repair/replace the "table top wafer fab"
and the technology to do that would have to be carried. Then that
technology needs to be repaired so you need the technology to do that. This
goes on forever with each iteration adding weight, complexity and cost.

Also making chips is not as simple as a wafer lab according to the guys who
are making custom chips for me. The process is big by nature, requires lots
of energy, lots of chemicals and consumables, very skilled people and
ultra-high tech ultra expensive equipment. These guys snicker or drool
whenever you talk about a small or inexpensive or easy prototype machine
like you are discussing.

Even if you could create this machine and have it weigh 100 pounds with 100
pounds of support stuff, excluding consumables, and 100 pounds of spare
parts and equipment it becomes really heavy and would cost millions of
dollars. I don't know how to figure out the weight of the person to operate
this or the supplies he needs. This also ignores the toxicity of some of
the processes.

A better suggestion may be to design a "generic" logic module using modern
technology. I'm not suggesting a few gates on a board as in the 80s I am
suggesting a 32 Bit ARM processor, a DSP, 160k of program flash, 8Mbits of
data flash, 12k of RAM, a USB port, an IRDA port, some A/D channels, some
D/A channels, somer general purpose IO pins. This could be built on a 2x3
board that uses very low current (50ma with both CPU and DSP cooking at
22/80 mips) at 3.0 volts using available (off the shelf) technology for $20
a board in medium volumes at about 2 oz a board.

In place of your 300 lbs of machine you could carry 2400 spares for $48000.
Considering a desk-top fab will probably cost Millions, which excludes the
packaging and testing equipment also required.

The real difference is that you have to get used to the concept that in
some things, such as modern electronics, you are often better off to throw
a bunch of parts at a simple task than to make something custom.

If you need to interface a full keyboard use one of these boards and also
use one to interface to a single switch. The idea is to have so many of
them that it just doesn't matter. If the initial design used this approach
there would be thousands of these boards in a starship spread through
critical (life-support) and non-crital (personal entertainment) systems.
Take some multiplier of these as spares and you would be covered for many
decades.

Since many of the boards will be used for different types of tasks a
particular failure on one part of the board would not prevent the board
from being used in another location. For instance if an AD failed switch
that board to some task that doesn't use the ADs and take the one from the
task that didn't use the AD. This provides some redundancy without even
reaching into the spares.

This approach can be applied to other technology issues also. For instance
only use two kinds of displays, a big one and a small one, and make sure
the big one can do the job of the small one. Then carry spares, mostly of
the big ones.

Another way to extend the mission duration is to send supply ships ahead,
or send them faster from behind with some replacement stuff. Since "stuff"
doesn't need gravity or environmental controls or oxygen or food or water
it can be moved much faster and much cheaper than we can move people.
Although re-supply may be distasteful to "pure" starship travel the
reallity is that even here on earth it was, and is, considered normal.
Aircraft carriers and submarines and space stations do it, the only
difference is distance.

Considering FTL isn't going to happen soon, if ever, it is probably safe to
assume that we would go pretty slow in a colony ship. If a supply ship can
go 1.5 times faster at 8 months we send one with the first resupply
reaching us at the 1 year point. Assuming engines will keep getting better
perhaps the next supply ship is launched at 18 months and reaches us in 2
years. Radio will still be effective so we can provide them with a shopping
list even if it is taking weeks or months for it to reach earth.

Personally I don't think we will be going to reach the stars soon. However,
I think starting to travel is critical to our survival just like setting
out in doughouts was to most early sea fareing nations. I think that our
travelers, now in space for 15 years, will be stuned when some kid pulls up
in his dads Mach5 with his FTL Quantum drive with the Window's logo on it
and says "haven't you heard, Bill Gates bought NASA, now everyone has an
Intel FTL drive in their family car. Other than having to turn it back on
every hour and the occasional warping into a star it works great"