Re: To space without rockets ?

Anders Sandberg (
28 Oct 1997 13:04:29 +0100 writes:

> Is it possible to have a cord connected to earth as it's still freefalling?
> Well, I guess it couldnt be attached to one spot on the earth, but maybe to
> a track or separate cord that went around the earth, and have enough leeway
> that it could stop temporarily at stations along the track to upload supplies
> or whatever into the cord connecting to the object in space, well i guess it
> would have to be a tube. I dunno how it would get up there, perhaps some
> kind of suction system . There's a problem with air resistance too.

Congratulations, you have just rediscovered the beanstalk (aka orbital
tower) and the rotovator!

Start with a satelite in geosynchronous orbit; it will orbit the earth
in 24 hours, which means that it will always stay over the same place
(that is the definition of the geosynchonous orbit). Suppose you
lowered a long string from it; it would obviously hang straight down,
over the same spot of surface all the time. This is the idea of a
beanstalk; you simply connect your satelite in geosynch orbit with the
ground by a strong cable, and add a counterweight cable with (say) a
tethered asteroid beyond ao that the whole system remains stable. Of
course, the cable needs to be rather strong, but buckytubes seems to
be a real possibility.

The rotovator is a cable that rotates around the earth (its center of
mass is in a circular orbit) with a period of rotation that is a
rational multiple of its period of orbit; if implemented properly the
ends will drop down into the atmosphere almost vertically, slow down
to zero local velocity for a short while, and then move out again.

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y