CubeSats are one of the cheapest, most efficient ways to get to space. Each CubeSat unit measures just 10 centimeters on a side, which is usually enough room for solar panels, communications equipment, and a small science payload. It isn’t enough room for an engine, and generally, most CubeSats are dumped into orbit and left to fend for themselves, tumbling aimlessly until drag pulls them to earth after a few months or so. This makes them cheap for a spacecraft (usually a little over $100,000 each including launch costs), but places rather severe limits on what they’re able to accomplish.
In 2013, NASA funded three different groups to develop small, highly efficient propulsion systems specifically designed to enable spacecraft like CubeSats to orient themselves, maneuver, and even change their own orbits. The propulsion technology that NASA is interested in is called ion electrospray, and MIT’s prototype is a modular, eight-thruster unit just 21 millimeters thick that can change the velocity of a CubeSat by a staggering 100 meters per second.