X-Message-Number: 12111 Date: Sun, 11 Jul 1999 08:16:42 -0700 From: Rand Simberg <> Subject: Re: CryoNet #12103 - #12109 At 05:00 AM 7/11/99 -0400, Thomas Donaldson wrote: >The only possibility of asteroid destruction comes for about the first >75 years from now, when such efforts have not become routine and our >abilities to deal with such asteroids remain in a primitive state. (I >will note that nanotechnology won't be a lot of help. Asteroids are BIG, >and deflecting them will require some large forces and/or prolonged small >forces over a period of years). Well, Thomas, astronautical engineers, like myself, who are familiar with the principles of molecular manufacturing (which I assume is what you mean when you say nanotechnology), would strongly disagree. First, with respect to your last statement, assuming that it is found and dealt with early enough, the delta V required to divert an asteroid or comet from an earth collision course can be quite small (just as a one-degree course change can result in a difference of many miles at the end of a thousand mile journey). The mass of the body itself can be used as propellant, given some kind of sophisticated engine landed on it. This would be particularly easy with the ice of a comet, but even a stony-iron meteoroid could be chewed up with mining machines and fed to an accelerator. Second, since molecular manufacturing makes it easy and cheap to build extremely light and strong structures, it will in general dramatically reduce the cost of access to space (which are currently driven by the need for high mass fractions and the containment of high-power reactions). I suggest that you look at some of the work of the Molecular Manufacturing Shortcut Group (a virtual chapter of the National Space Society) for further info. In short, MM will revolutionize the development of space and our ability to manipulate its resources, so I just don't understand the above comment at all. That is not, to say, of course, that I am counting on it in any way--I believe that we can develop such capabilities without it--just that it will make it much easier. Finally, I have no idea where you come up with the magic number of 75 years. I expect that we will be moving asteroids for their resources in less than twenty, with or without MM. Rand ************************************************************************ * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=12111