Right now, the two dozen CubeSats in the atmosphere are fine; they retire, float for a while, then die burning up in the atmosphere. But if we want them to stay in a higher orbit (we do), they could stay there a lot longer, potentially cluttering up the orbit, or even causing collisions. To relieve any space congestion, Paulo Lozano, an associate professor of aeronautics and astronautics at MIT, has created miniature engines for the CubeSats that run on ion beams. They're small, flat squares lined with 500 microscopic tips. When the tips are hit with voltage, they emit a stream of ions, enough of which can move the CubeSat along.