Probably born of the minds of futurists in the 50s or 60s, jet packs fit neatly in a small category of "Things that work way better in space than on Earth." Our gravity is terribly oppressive. The amount of energy needed to move an individual any reasonable distance off the ground is so immense that it becomes prohibitive, as the more propellant you carry around, the more weight you are required to lift.
There's also the whole "roasting the back of your legs" problem.
Regardless of the physics of these things, one thing will always be true: I love drawing jets of flame.
Or pine trees. Same thing.
I feel like I did the contour lines totally wrong. Instead of using simple diagonal cross hatches, I should've gone in the direction of the curvature of the tube. Also, the ends of the tubes needed more dimension, which I could've done better had I thought about the actual geometry of a cylinder.