I’d like to sort of freeze everything at the point where the rocket is just starting to take off and the smoke is pouring out onto the landing pad and turn the ico sphere particles into a mesh. Is that possible? This part of the rocket tutorial is what I’m talking about: https://cgcookie.com/lesson/simulating-the-launch-smoke
Go to the Modifiers tab and press the Convert button in the Particle System Modifier:
Note that there also is the Particle system left now! To remove the Particle System you can Apply the Modifer (dropdown arrow or CTRL+A while hovering over the Modifer):