The Coffee Can Metaphor
Though he's actually a rocket scientist, Rovey uses the metaphor of a coffee can to show how the concepts he works with are accessible to everyone. "Plasma is not some archaic thing you've never seen before," he says, "it's actually in the room right here, the fluorescent lights. That's where the light is coming from." The speed of ions in the plasma can be transferred to forward motion by using an electrically charged grid. Rovey explains that the negative charge of the grid attracts the positive ions, and as they shoot through that grid, it gives the mechanism "the transfer of momentum we need to impart a force on the spacecraft."