Text 45, 118 rader
Skriven 2004-07-19 10:33:08 av Robert Comer (1:379/45)
     Kommentar till en text av Monte Davis (1:379/45)
Ärende: Re: 35 years ago today
==============================
From: "Robert Comer" <bobcomer_removeme@mindspring.com>

> Bob (and Geo) -- sorry for being snarky, I've been spending too much
> time on forums and chat groups where people proudly trot out "Gotcha!"
> objections that are either misunderstandings of the physics, or have
> been dealt with.

No problem at all, it's something you feel strongly about and I can sure see
why!  Sorry if I sounded like that group (I know the type you're talking
about), but all I really want to do is learn.

> Hint: even if the elevator cost $40 billion, the construction bonds
> would get paid off at a nice clip.

Wow is all I can say, 40 billion is nothing compared to what we would get in
return.

> Hint^2: we're not talking NASA, or even governments, any more...

That's going to become a big question later on, isn't it...

- Bob Comer



"Monte Davis" <monte.davis@verizon.net> wrote in message
news:c6gnf0h07bs1tlqiv8rmnsv6on6dul5tiu@4ax.com...
> "Robert Comer" <bobcomer@mindspring.com> wrote:
>
> >I never said they didn't consider it either or that the problem was
> >insurmountable, just trying to think of what they did come up with.
>
> Bob (and Geo) -- sorry for being snarky, I've been spending too much
> time on forums and chat groups where people proudly trot out "Gotcha!"
> objections that are either misunderstandings of the physics, or have
> been dealt with.
>
> Lightning: you need an anchor point on or near the equator. You want
> it moveable, so a few times a month you can shift the cable out of the
> way of satellites and debris big enough to hurt it (already being
> tracked). So you're talking about something like a moveable drill rig
> or the existing Sea Launch rocket facility.
>
> There are several zones (e.g. 1000 km west of Ecuador) where lightning
> is rare: a few strikes per year in 100,000 km^2. You track what storms
> do appear and move out of the way. On rare occasions, you might have
> to use cheap tethered balloons or wired sounding rockets, designed for
> *better* conductivity than the elevator cable, as sacrifices to
> discharge storm cells. Bottom line: you can reduce odds of damage well
> below the odds that lightning will destroy a passenger airliner. (Last
> time that happened was...?)
>
> (and oh yes, for SF readers -- if the cable *is* severed, nothing
> spectacular happens. The design target is <800 tons mass over 60,000
> miles, about the density of Saran wrap. It doesn't "snap" off to outer
> space at high speed or come hurtling down in a world-girdling swath of
> meteoric destruction, like the much much heavier cable in _Red Mars_.)
>
> I'm writing the book because something remarkable happened over the
> last five years. When nanotube strength figures started appearing
> after 1996, NASA commissioned a small study to see if the 100-year-old
> idea of space elevators -- always dismissed because the cable would be
> 'unobtainium' -- was becoming feasible.
>
> In 1999-2000 they concluded that an elevator deployed hundreds of
> on-beyond-Shuttle launches, with a 20-km-high base structure (no
> weather issues) and 1000-ton hyperspeed maglev bullet-train, would be
> a great idea for "late in the 21st century"... cost, IMHO, approaching
> a trillion bucks for openers.
>
> One of the participants, Dr. Brad Edwards (then at Los Alamos NL),
> wondered if it could be done quick and dirty instead, and started
> calculating and consulting others. He's made many contributions, but
> his breakthrough was hard numbers for a bootstrapping scenario:
>
> Use just a few launches to deploy a narrow, fragile 22-ton ribbon,
> then spend 2-3 years sending up progressively larger "spiders" with
> spools of additional CNT material that they attach to widen it, until
> it can handle multiple 7-ton climbers, each carrying 13 tons of
> payload.
>
> No ultra-tower at the base: pick a base site with optimum weather, and
> be agile (as above).
>
> No zoomy maglev: boring electric motors at 200 kph, a few hours to
> LEO, a week to GEO. (the latter not for people until you can lift
> heavy shielding for the Van Allen belts that are between LEO and GEO;
> the 21 Apollo astronauts who've been there passed through in <30
> minutes)
>
> No 1000-ton payloads (until you use the first elevator to take up
> materials for more and bigger ones). Above all, no huge fleet of
> heavy-lift boosters to ante up (the Shuttle costs $500 million per
> flight).
>
> The cost numbers dropped through the floor, and as Edwards says, in
> 2002 serious aerospace people stopped laughing and started asking how
> they could help. In D.C. I sat next to the system architect for
> Iridium: he knows more about lowball cost estimates and overruns for
> space projects than we ever will. Some people like him think the cost
> can be driven down to $6 billion, some say $20 billion. (Current NASA
> budget ~$15 billion; Apollo in 2004 dollars, >$300 billion)
>
> OK, private industry currently spends $37 billion a year orbiting comm
> and remote sensing satellites, and governments spend a lot more: how
> much of that would you capture the first year at one-tenth the price
> per pound? (No doubt DoD will want its own elevator for Special
> Projects launches.)
>
> Hint: even if the elevator cost $40 billion, the construction bonds
> would get paid off at a nice clip.
>
> Hint^2: we're not talking NASA, or even governments, any more...
>
> -Monte

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