Accelerating from 0 to 60, then slowing down for a stop light is no problem for an ordinary automobile. But if you were piloting a rocketship, it wouldn't be so easy. Most rocket engines are designed to burn full-on (liftoff!) or full-off (coasting through space) with no in-between. And that can be a problem--namely, how do you land this thing? In today's story we learn how engineers are developing technology for throttling next-generation lunar landers.