Hey,

Do you mean an hardware rendering smoke? Because i have a problem with harware rendering. I also posted a message for it and people say that it's because my computer graphics are too low...
But they also told me that there are ways to make a missile trail with software rendering.

If you are not talking about an hardware smoke then remind me that i have to take a look to the maya book a little more

Thank you in advance for your interest.

TheWebAgent