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A Moon base is too far; an asteroid ship better alternative:)



 
 
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  #31  
Old March 18th 05, 06:30 AM
Kent Paul Dolan
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Joe Strout wrote:

There are no selenosynchronous orbits.


One. You're orbiting in it.

xanthian.

  #32  
Old March 18th 05, 05:33 PM
Dr John Stockton
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JRS: In article , dated Thu, 17
Mar 2005 02:07:36, seen in news:sci.space.tech, Rick Jones .
invalid.retro.com posted :

Would the dark/night side of a lunar power grid be cold enough to be
more easily (than on earth) constructed from superconducting
materials?


I believe that I have read that for an east-west line in mid-northern
latitudes it would be enough to put the cable at the south side of the
base of a trench-and-berm, in such a fashion that the cable could "see"
a large amount of "sky" without ever "seeing" either the Sun or any
surface illuminated by the Sun. Present-day "high-temperature
superconductors" would be used.

/\
/ | \
/ | \ -- direction of sun's rays
/ | \
/ |
-----------/ | /---------
| /----/
| /----/
|oo /
+---+

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  #33  
Old March 18th 05, 06:59 PM
D Schneider
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Paul F. Dietz wrote:

{...] but in vacuum you'll be
constantly generating high energy ions and electrons in the surrounding
plasma, and possibly causing runaway discharge due to their collision
with surfaces and secondary ion production.


How much plasma is there on the Moon? I would have thought that the
density of earth's atmosphere falls off rapidly after LEO (isn't drag
negligible by MEO?). Does the solar wind have enough density to produce
arcing?

/dps

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  #34  
Old March 18th 05, 10:30 PM
Gene P.
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On Wed, 16 Mar 2005, Joe Strout wrote:

1. The Lunar Power Grid + electric furnace. Who cares if the electricity
comes from solar panels on the other side of the moon or from a great big
nuclear pile a couple of miles away...


Running power lines all the way around the Moon is itself a daunting
engineering challenge (though admittedly, one probably on the same order
as a mass launcher and large-scale orbital manufactury). A reasonable
solution, but not such a trivial one as to make lunar night a non-issue.

A nuclear power plant is also a reasonable solution, but again, it
doesn't offer the same flexibility or convenience as continuous sunlight.


While admittedly not most efficient for the 1st such plant, if space based
industrial civilization takes any sort of toe hold, the moon will develop
such infrastucture in the same way that the Earth did... (i.e. Nuclear
and fossil power plants in the Southern USA sell a *lot* of power to the
the Northeast over the national power grid.)


2. Space furnace mirrors can point down at the lunar surface just as
easy as at an orbital processing facility...


Can they? From where? There are no selenosynchronous orbits.


I was thinking of Lagrange points here... but the fact is that if you
build several (3 at a minimum) sets of mirrors in lunar orbit, they can
"trade off" power duties to lunar ground targets as they pass by
overhead...

I'm basically a skeptic of human nature though... I don't think there will
ever be solar power satellites or really big solar mirror farms for the
same basic reason:

The ability to focus a power beam at any distance is equivalent to a space
weapon of incredible power. No Government will ever allow it... unless
there's been a major war and only one government has access to space.

Building big Photovolatic arrays *might* be allowed though... as long as
the facility it's attached to doesn't have a railgun.

Gene P.

--
Alcore Nilth - The Mad Alchemist of Gevbeck



  #35  
Old March 18th 05, 10:38 PM
Gene P.
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On 16 Mar 2005, David Summers wrote:

Then why don't we use such things on Earth? Nuclear power is WAY
cheaper in Mexico (or even Nevada compared to New York)!

The fact is, transmitting power via cables over long distances is
expensive. The grid uses nearby sources, not far away ones. Losses on
long distance power cables become very large very fast.


Clearly you are unaware of the fact that we *do* ship *A LOT* of power
over the grid to the Northeast and West Coasts...

That's why a generator fault near Chicago or in Canada can cause cascade
failure of the grid in New England... because without the long-haul power
imports, the local grid sources *can't* carry the load.

One of the leading exports of the south is generated power. We didn't let
our environmentalists and carping shouts of NIMBY! NIMBY! stop us from
continuing to build power plants from 1960-1990. (NIMBY = "Not In My Back
Yard")

Mississippi has more than enough Nuclear power to carry the entire
(mostly agricultural) state... Nonetheless, it *also* operates several of
the most modern and up to date fossil power plants in the nation as
well...

And the Texas sub-grid sells a lot of power to the West Coast...

Gene P.

--
Alcore Nilth - The Mad Alchemist of Gevbeck



  #36  
Old March 19th 05, 12:59 AM
Paul F. Dietz
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D Schneider wrote:

How much plasma is there on the Moon? I would have thought that the
density of earth's atmosphere falls off rapidly after LEO (isn't drag
negligible by MEO?). Does the solar wind have enough density to
produce arcing?


The concern would be that there would be a runaway discharge from
secondary ions. You wouldn't need much to get that process started.

Paul
  #37  
Old March 19th 05, 04:11 PM
Fred J. McCall
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"David Summers" wrote:

:Then why don't we use such things on Earth? Nuclear power is WAY
:cheaper in Mexico (or even Nevada compared to New York)!
:
:The fact is, transmitting power via cables over long distances is
:expensive. The grid uses nearby sources, not far away ones.

Not these days. The grid uses whatever power is there and it can come
from all sorts of places. This is why when there is a power failure
these days it usually takes down huge geographic areas of the grid

:Losses on
:long distance power cables become very large very fast.

Well, no. Ever heard of DC?

Total transmission losses and distribution losses in the US amount to
around 7.5%. This includes all the voltage step up and step down
losses as well as line losses. This is hardly 'very large'.

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territory."
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  #38  
Old March 20th 05, 03:01 AM
Sander Vesik
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Cameron Dorrough wrote:

If you were serious, you'd probably direct bury them - AIUI, moon dust is a
great insulator.


Its a great thermal insulator - this does not automaticly mean it is
also a great electrical insulator (especially if fused by the electricty
first).

--
Sander

+++ Out of cheese error +++
  #39  
Old March 20th 05, 08:52 PM
Joe Strout
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In article ,
"Gene P." wrote:

2. Space furnace mirrors can point down at the lunar surface just as
easy as at an orbital processing facility...


Can they? From where? There are no selenosynchronous orbits.


I was thinking of Lagrange points here... but the fact is that if you
build several (3 at a minimum) sets of mirrors in lunar orbit, they can
"trade off" power duties to lunar ground targets as they pass by
overhead...


Neither of those is anywhere near as easy as focusing light at an
orbital processing facility. The distance from any Lagrange point to
the Moon is huge, requiring an enormous mirror and resulting in a rather
broad hot spot. And in the case of several mirrors in low lunar orbit,
you've now got rapid tracking issues -- not insurmountable, to be sure,
but clearly not as easy as a mirror as part of your facility, facing the
sun 24x7.

I'm basically a skeptic of human nature though... I don't think there will
ever be solar power satellites or really big solar mirror farms for the
same basic reason:

The ability to focus a power beam at any distance is equivalent to a space
weapon of incredible power.


Nonsense. The microwave power beam from a solar power satellite has
half the power density of sunlight. You could walk right through it and
probably wouldn't even notice.

I don't think that mirrors could focus light on Earth's surface enough
to cause major damage, either.

,------------------------------------------------------------------.
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  #40  
Old March 20th 05, 09:04 PM
James Nicoll
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In article ,
Gene P. wrote:

I'm basically a skeptic of human nature though... I don't think there will
ever be solar power satellites or really big solar mirror farms for the
same basic reason:

The ability to focus a power beam at any distance is equivalent to a space
weapon of incredible power. No Government will ever allow it... unless
there's been a major war and only one government has access to space.

Building big Photovolatic arrays *might* be allowed though... as long as
the facility it's attached to doesn't have a railgun.


I've been thinking about this ever since I noticed that Dyson
Swarms + Phased Arrays + short wavelength beams = the ability to
evaporate Earth mass worlds in about a week anywhere in the visible
galaxy and the nearer galaxies (limited by orbital predictions). On
the one hand, it explains the Fermi Paradox but I think in the short
run, AU range beams aren't quite the centralizing force they appear
to be.

Once the range is long enough, it gets hard to nail ships
that have some kind of on-board motive power. A large enough swarm
may be able to get close enough to destroy a pesty array. Some laser
designers are less robust that others: the X-Ray lasers that were
discussed last year have 100% reflective mirrors until they are
jostled by an atomic diameter or so, for example, after which heat
losses will make the mirrors turn into plasma somewhere between
"Uh" and "Oh". Kinetic Friendship Packages are one way to make this
happen.

Arrays are big and will have huge, targetable radiators. Other
arrays can used a la MAD to limit antisocial applications of beams. In
this case, balkanization limits tyranny. If the Mercurial Power Company
and Harsh Overlords LLC starts talking about "natural monopolies", it
may be best to just open fire on their corporate HQ.

Even with terawatt beams, it takes a surprisingly long time to
evaporate even small asteroids. Dig in and invest in _good_ mirrors.

James Nicoll


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