[extropy-chat] Space elevator numbers III

[Keith Henson]

snip

 >Incidentally, 1000 mph is  arbitrary.  But the faster the cable moves, the
 >shorter the replication time for hauling up more cable and the higher the
 >throughput.  Also the number was picked to make the transit time to GEO
 >under a day.

Space debris and Van Allen belt radiation need to be considered in the 
context of a space elevator.

The space elevator requires a counterweight outside of GEO, the size 
depends on both the mass of the elevator and the distance the counterweight 
is hung outside of GEO.  Since pieces space debris large enough to cut the 
cable have to be collected, several ion engine tugs will be needed to move 
space debris to GEO for counter weight mass.  The scope of this effort is 
not well defined.  Also, unless the satellites are maneuverable, nothing 
below the counterweight can coexist with a space elevator regime.

To some extent lower altitude satellites can be hung on the elevator pulley 
stations, but non maneuverable satellites will eventually run into the cable.

Van Allen belt radiation not only presents a radiation hazard to workers, 
but degrades solar cells and electronics.  The total mass of particles in 
the Van Allen belts is a few kg.  There has been a proposal to drain the 
inner belt, http://www.tethers.com/HiVOLT.html but in any case a project 
with a daily mass budget 3 orders of magnitude higher that the particle 
mass in the belt should be able to deal with them.

One possible way would be to release gas well below GEO from the elevator 
into the belts.  Enough gas, especially if injected retrograde, would also 
help deorbit the smaller space debris.

To be continued