Feel free to comment with your own jokes.
This is by XKCD, aka Randal Monroe, a PHD physicist, who used it in a whimsical study on the practicality of using the recoil from an A-10 30mm rotary cannon as a method of propulsion.
Orion's Cold Fire
All the Secrets of the Universe and Some Really Important Stuff Too!
He’s driving distracted?
another from XKCD