Yes, ion drives have a strange Cache.
First, I think 'ion' just sounds cool, and NASA has been talking about ion rives for ages. But also there was a specific Star Trek episode that touted the ion drives of some space ship that ambushed them and captured Spock, erm, Spock's brain, and I think that stuck in the popular imagination. While the exhaust speed of an ion drive is far greater than any current chemical rocket the thrust is very small and so the rate of acceleration is also very small. This high exhaust speed makes for great efficiency, though, so once you are out of the atmosphere it is a better thing to have for long-range probes that cannot come home and tank-up like a plane or ship can on earth. You get much more total thrust out of a given weight of propellant but it takes much longer to take effect. I don't think an ion drive can even operate within our atmosphere. They have to test them in a vacuum chamber.
Oleg -- Yes, treknobabble is garbage. I've made a distinction in my own mind between Science Fiction and 'Techno-drama'. Real SciFi actually has a plot that turns on the effects of scientific issues on how we see the universe and our place in it. Techno-drama is just soap opera with technological stage props and techno-babble. All but a handful of Star Trek episodes are nothing but Techno-drama.
[ 11 May 2002, 01:15: Message edited by: Baron Munchausen ]