Slamming the Not-So-Open Window Shut
[w]hat we most urgently need to recognize now is the limited time available to us in which to begin the task [of sending manned missions to Mars].
The manned space program has languished ever since the moon missions and is currently incapable of endeavors beyond Low Earth Orbit (LEO). All current deep space work is done via robotics. Any attempt to repeat the human accomplishments of the 1969-75 era will require vast amounts of investment in infrastructure, . . .But, while the manned extra-orbital program has long since been discontinued, we have been active in LEO, as have numerous other nations, and today there are more than 2000 satellites circling the planet.
Ironically, this continued activity in space, minimal in scope as it has been, now presents us with a legacy which is potentially the greatest impediment to a continued manned space program. The opportunity to become a truly space-faring planet (i.e., beyond LEO ), contrary to popular belief, is not an empty, always open, window. It can be, and, in fact, likely will be, slammed tightly shut at any moment.
. . . With both the Challenger and the Columbia Shuttle disasters came loud calls to abandon, if not space altogether, certainly its manned exploration. But this periodical reaction to human costs pales in comparison to one potential "worst case," scenario--a very probable scenario--which demands our attention. . . .[F]or a time, the leading theory on Columbia's destruction as it reentered the atmosphere from LEO was that it had struck a piece of space junk. The danger of space junk is well known in the astronautical community. Because of their high relative velocity of thousands of miles per hour, even tiny objects (e.g., button-sized), become lethal projectiles when striking a spacecraft. As satellites have proliferated in LEO, this problem has reached a near-crisis level. As a by-product of placing those 2000+ satellites in orbit, we now also have some 8000 ancillary objects in orbit that could bring a spacecraft down. Until this junk is removed from orbit, safe access to space is far from assured, and the problem continues to grow.
A great many of the 2000 satellites in LEO are military and will certainly be targets in the next war between great powers. . . . Every targeted satellite will instantly become thousands of shards of shrapnel, forever (essentially) orbiting Earth looking for a space vessel to penetrate. Overnight, the possibility of getting humans into orbit will be severely limited, if not extinguished altogether. Such a war, even if it doesn't result in the complete breakdown of civil society on the surface of the Earth, would put so much space junk in orbit that we would never be able to send humans into space again.