Asri-unix.1347
net.space
utzoo!decvax!cca!KING@KESTREL@sri-unix
Tue Apr 27 14:46:33 1982
projectile pollution in space
	From time to time  someone proposes electric reaction  engines
for deep space manouvering, based on the ejection of large numbers  of
small projectiles.  Such a proposal recently appeared in this forum.
	I made  back-of-the-envelope calculations  on the  effects  of
using a billion such projectiles  (100 per second for several  months;
hardly an implausible launch  schedule).  This might  be used, say, to
move 1/e of an e-million-ton asteroid (100 meters diameter) into Earth
orbit (delta-v  of  10  KM/sec) using  a  billion  1-KG.  projectiles.
Making reasonable assumptions about the  volume of space in the  Solar
System that these projectiles will spread out into, we get an exposure
of 1/10e6 KM^2-yr. from this one asteroid movement.
	This seems like a meager increase, but it seems unlikely  that
this system will only be used once, to move a single relatively modest
asteroid.  It  also seems  unlikely that  our space  exposure will  be
forever limited to  1 KM^2.  I  rather assume that  in the future  our
exposure will be "on the order of" thousands of square KM, and that we
will move thousands of asteroids (or bigger ones).
	To make  a  long story  short,  do proposals  for  deep  space
propulsion by reaction motors  ejecting projectiles properly  consider
the  pollution   problem?    How   does   the   artificial   meteoroid
concentration compare with that of the natural population?  With  that
of the natural  population in  meteor showers?   How nonuniform  would
these non-uniform meteoroid swarms be after (say) a year?
	I'll do more  calculations unless  someone can point  me to  a
reference in which this point has already been considered.


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