Could you please give a link to the mod/program that you used to make the fuel tanks? EDIT: Found it myself xD http://forum.kerbalspaceprogram.com/showthread.php/25061-Part-generator-Version-2-X-release-open-beta
As far as I know, astroid fields contain millins of asteroids, even a small one would be arround 1000 asteroids, having so many objects would fry low-end computers
Would be cool if someone would be able to make the solar system in KSP, with the planets in the 1:1 scale, but the distances reduced (for gameplays' sake)