Fire in the sky, O'Neill colonies and asteroids

Re ion engines- happens I worked on early ion engines.1959-64
NASA used mercury (reason ionizable fluid) AF used cesium metal (pain
in neck to handle as chemicall very acive-) BUT it ionizes on heated
tungesten- the ionization energy of Cs is lower than work function of W
so if you heat W enough to "boil" Cs off surface, it leaves as
ion)Neat way to get + ION beam- toss in electrons from TV type gun to
get neutral beam.
BUT
you do not need exotic - say Kr
Anything you can ionize will do just fine
say "lunar" dust powder
H2 and He work (lousy to ionize but work just fine)
UF6 works
the molecular weight doesn't matter at all.
We do not need expensive or rare - the only criteria is energy loss to
ionize it.
With dust you just use electrons on one one pile and accelerate - ions
appropriately.
Strip electron on other pile accelerate to same speed as above and let
them eventually neutralize each other...(total effect is mixd neutral
pair of beams.)
Jim Lawler ("Professor"-) PhD tired aerospace engineer (not re tired
just did it once)
(literally a "rocket scientist"- amused by that jargon)
Re O'neal colonies
U R right on -- if my math holds up there will be more people in space
than on earth in a "couple" (couple meaning more than 2) of centiries.
And they will be average IQ over 135 in 2006 style measurement. (you
cannot aford to launch welfare basket cases
1) lift energy alone cost too high
2) is someone were stupid enough to do that space would and will kill
all dummies.
It is not paticlarly safe place to make errors. Usually you get one
chance. No more.
3) fit survive unfit don't (to coin a "new" phrase vintage
1860's)where did I hear that b 4?




Lawrence Gales wrote:
On Wed, 15 Mar 2006, Jim Davis wrote:

Date: Wed, 15 Mar 2006 19:41:29 -0000
From: Jim Davis
Newsgroups: sci.space.policy, sci.space.tech
Subject: Fire in the sky, O'Neill colonies and asteroids

Lawrence Gales wrote:

For the 1st colony I select 1500 feet in major diameter and 43
feet in
minor diameter, so using strict scaling it should be
(1/4)*(1/10)*(1/10) = 1/400 of the mass of the Stanford
torus (the last (1/10) occurs because the tube would be
1/10 as thick as well as 1/10 as wide). This yields a
structural mass of 625 tons, but we will set it at 1000
tons to be conservative.

Some comments:

1. You've gone from 1 rpm from the original Stanford design to 2 rpm
in your scaled down design to maintain 1 g. That will probably not be
acceptable.

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Well, O'Neill believed that it was acceptable, and it is my undestanding
that most people be can be accustomed to 3 rpm, so 2 rpm should not be a
stretch

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2. 1000 tons is about 5 times the mass of ISS and yet you intend to
accomodate 200 people?



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That is the raw structural weight w/o air, water, soil, shielding, etc. I
scaled it from the Stanford Torus which had 250 times the weight, but
based
on other scalings that I saw on the Stanford Torus website (which seems to
have disappeared) it seems reasonable. Note that the 10,000 person torus
offered huge open spaces and nearly luxury living, whereas this initial
colony is more of a construction shack. It does offer nearly 1000 feet^2
per person
=====================================



3. 1000 tons is about 4 times the mass of the Airbus A380 which cost
about $12 billion to develop and build and yet you estimate your
first torus cost at $3 billion?

Jim Davis

======================================
I specifically stated that I did not include development costs -- only
production and transport costs.


-- Larry

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