[ExI] Written for another list

[Keith Henson]

On Wed, Aug 1, 2012 at 4:01 AM,  "J.R. Jones" <mrjones2020 at gmail.com> wrote:

> We need space elevators, plain n simple*.

Unfortunately, space elevators seem really unlikely.  Not impossible
but (short of nanotechnology) really, really hard.  Not only do we
have the cable problem, but we will have to clean out all the
satellites that can't maneuver around the cable.

That didn't keep me from proposing a constant diameter cable that used
pulleys to get the taper.  Did that years ago, the ESA talk about how
to do it is on Eugen Leitl's site.  Wrote the talk after working out a
model for chapter, UpLift Incorporated, in the same series as "The
Clinic Seed."  Here is the first page.

June 2025

On the hangar deck of the former aircraft carrier Enterprise, amid a
maze of electrical cables, water and sewer pipes, there were a hundred
lashed-down house trailers.  Mohawk-ironworker families from Ontario
and upstate New York occupied most of them.  Marc Leaf, his wife Minny
and their children lived in an outside trailer on the port side.
The Enterprise was anchored eleven miles south of Baker Island, in the
Western Pacific doldrums, just inside the only territorial waters of
the US that came within a few miles of the equator.  The location made
the UpLift suits happy though Marc could not imagine why.  Nobody was
going to attack the huge ship half way between Hawaii and Australia.
In Marc's opinion, the monotonous weather—no storms--was the reason.

The kids were in bed and Marc and Minny were at the rail holding hands
and looking out at the equatorial ocean in bright moonlight.  No
matter how bright, moonlight scenes are black and white.  Marc thought
back to a nearly silent hike he had made when a teenager in a light
snowstorm under a full moon.

It had been just below freezing that night.  Marc, his brother, his
father, his uncle, a cousin and his grandfather had walked several
miles up Willow Creek in the middle of the night.  The cloud cover was
thin; the full moon brilliantly illuminated the fresh snow, leaving
pockets of pitch black under trees and in the water.  The effect was
surreal, intensely beautiful.

Dressed in warm boots and a military surplus jacket Marc had had no
problem staying warm.  There was certainly no problem staying warm
here.  The only thing that kept it from being unbearably hot was a
constant breeze from the east.  The breeze blew through the hangar
deck and carried away the heat from trailers' purring air
conditioners.

In the background was the vibration of the 31-foot diameter driver
wheels turning at 900 rpm, the whip-cracking sound of the supersonic
space elevator cable, reminding Marc of a flag flapping in a strong
wind, and the occasional run down and run up of the variable speed
cable.  The elevator was mostly lifting parts now, but over its life,
more than ninety percent of the capacity of the elevator had raised
more cable and counterweight.  Four more doublings would take it from
its current capacity of 125 tons a day to its design capacity of 2,000
tons per day.

> From: Eugen Leitl <eugen at leitl.org>
>
> On Tue, Jul 31, 2012 at 10:09:51PM -0400, J.R. Jones wrote:
>
>> We need space elevators, plain n simple*.
>
> You need radiant power propulsion in order to lift
> the mass for the elevators.

If you use the constant diameter cable, you can lift almost all of the
elevator from the ground.

> And you pretty much want to build the elevator on the
> Moon first, not Earth.

As someone said 3 years ago at the elevator conference, you can build
a lunar elevator out through L1 out of dental floss.  (Spectra, 4.3
GPa and a density of slightly less than water.)

> One of the ways to provide power is to build terrestrial
> PV arrays which double als realtime targetable microwave
> phased array for line of sight vehicles (whether low-altitude
> low-velocity or high-altitude high-velocity). You'd be charged
> for the time slot.

> The additional expense for the added aerials and timing
> circuitry as well as simple coils or capacitors (which would
> double for power inverters) are negligible.
>
> Not sure about the target spot.

Dr Kevin Parkin has worked extensively on this.  I have done some
work.  The problem is the that it is hard to focus microwaves on a
small, far away target.  Same problem as getting power down from power
sats using microwaves, even at 110 GHz.

> It's obviously far more
> diffuse than a battery of solid state lasers groundside,
> so more suitable for large low-flying targets.

I don't think the phase stability over miles of transmitter is within
the state of the art, but it's a good idea.  Next time I see Dr Parkin
I will mention it.

Keith