Science and sci-fi

This site is IMHO an interesting overview of different sci-fi themes (weapons, spaceships, etc) and whether they can be figured out in a realistic way using science. There's a great deal of information to digest, but there's a lot of variety and ideas. Added to that is some interesting sci-fi art from various sources:<br /><br /><a href="http://www.projectrho.com/public_html/rocket/prelimnotes.php&quot; target="_blank">http://www.projectrho.com/public_html/rocket/prelimnotes.php</a&gt;