Re: Climbing a ladder to geosynchronous satellite

Stephen,

That's a classic question that has been explored to some extent by numerous 
hard sci-fi writers.  (Sometimes referred to as engineering fiction rather 
than science fiction, because the technology mostly exists but hasn't been 
implemented.)

The common name for such a cable is a space elevator.

Just briefly, let's talk practicalities.  Different parts of the cable 
itself will be at different altitudes, thus having different orbital 
periods and speeds.  This will create some tremendous stresses and other 
engineering obstacles to overcome.  For simplicity, let's assume the cable 
is massless and infinitely strong.  Thus, it is nothing but a line 
connecting the satellite to the ground.
Also, these things are more reasonable if we put something a bit more 
massive than just a little satellite at the other end.  How about a small 
asteroid.  This will anchor the other end better.

Now, create an elevator car, and ride it up the cable.  You have gotten 
from the ground to space orbit without the aid of a rocket!

Also, you have overcome MOST of the Earth's gravity well.  In 
geosynchronous orbit, you have 7/10 of the velocity you need to completely 
escape the gravitational pull of the Earth.  Thus, if you docked a 
spaceship at your geosynchronous spacestation, you could easily use the 
location as a port to take cargo and passengers to and from Earth without 
expensive nonreusable rockets.  It would take a lot less fuel to get the 
spaceship away from Earth, thus allowing the spacecraft to become smaller 
and more practical.

While we are thinking about it, let's go one step further.  Build your 
cable a bit longer, so the far end is 1.26 times as far away from the 
center of the earth as it was before.  (1.26 is the cube root of two).  You 
may think this will create problems, because the orbit will no longer be 
geostationary.  However, because you have a taut cable connecting it to the 
Earth, the tension on the cable will keep it above one spot on the Earth 
just as a whirling rock on the end of a string is kept in place.
There are, of course, many practical issues to overcome here.  For 
instance, you would need to make sure you had a good solid anchor on the 
Earth and the cable would have to be very very strong to handle the tension 
on it.

So, now the cable extends 47,000 km (29,400 miles) above the ground.  At 
this altitude, if you are forcing this thing to maintain a geostationary 
orbit, it is travelling at a velocity equal to the escape velocity at that 
altitude.  So, you can ride up the cable, board a spaceship, and then 
release from the dock.  The spacecraft will be thrown into space, away from 
Earth, without the use of any engines.

Well, I hope you had fun exploring this.  I sure did.

---Bob Macke
Instructor, Bowling Green State University dept of Physics and Astronomy

REFERENCES:
Bennett, Donahue, Schneider, Voit, The Cosmic Perspective, 1998, 
Addison-Wesley Longman.  (used for Earth data in calculations)