[ExI] skyhook elevator

Keith Henson hkeithhenson at gmail.com
Fri Feb 12 19:36:07 UTC 2010

On Fri, Feb 12, 2010 at 5:00 AM,  "spike" <spike66 at att.net> wrote:

>> ...On Behalf Of Damien Broderick
>> Subject: [ExI] skyhook elevator
>> It occurs to me (can't recall ever seeing this discussed,
>> although it must be an ancient sub-topic of skyhook dynamics)
>> that as your elevator climbs or is a shoved up the thread,
>> you'd not only be pressed against the floor but also against
>> the west wall. Maybe you wouldn't notice if the trip took a
>> couple of days, but you're going from rest to 11,000 km/hr.
>> Is that especially noticeable? What say the space gurus?
>> Damien Broderick
> Coriolis effect sounds like what you are describing, and it would be durn
> near negligible.  I will calculate it if you wish.  To give you an idea by
> using only numbers in my head and single digit BOTECs, geo is about 36000 km
> from the surface as I recall so add 6300 km earth radius and that's close
> enough to about 40,000 km so the circumference of the orbit is about 6 and
> some change times that, so 250000 km in 24 hrs, so you accelerate to 10000
> km per hour or about 3 km per second or so.
> How long do you guess it would take to haul you up to GEO?  An few hours?
> Lets say 10.  To accelerate 3 km per second eastward in 10 hrs would be
> about 0.1 meters per second, or 100th of a G.  The elevator passengers would
> scarcely notice.
> It is proportional of course.  If you theorize they get there in 1 hour,
> then the coriolis component is about a tenth of a G, but if they get all the
> way to GEO in an hour, there is some serious upward velocity involved.
> spike

Spike got it right.

Some years ago I spent some effort on this in the context of a story
and wrote a paper for an ESA conference from that work.

I analyzed a driven endless loop cable moving about 1000 mph--which
will get you to GEO in 22 hours.

Lifting 100 tons per hour it took 1.5 GW.

While the Coriolis effect isn't noticeable to a passenger, it provides
plenty of force to keep the up and down cables well separated.

The acceleration to 3 km/sec at GEO (from under 1/2 km/sec on the
surface) is "free."  The cable leans west from the rotation to the
east and extracts energy from the rotation of the earth slowing the
earth down by an extremely small amount.

Importing more than you are exporting would have the opposite effect.

People opposing to extracting rotational energy from the earth could
use the slogan "Conserve Angular Momentum!"


PS.  Lunar elevators really can be made of dental floss.

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