By Philip Ball Brian Gilchrist’s design for a rocket ship sounds like a bad joke. For a start, its engine is about the size of a single bacterium. And for thrust it relies on the equivalent of chucking microscopic beer cans out of the spacecraft’s rear window. Gilchrist, an electrical engineer at the University of Michigan, Ann Arbor, is not joking though. He proposes to harness the latest nanotechnology to create an engine that will make its way across the solar system by firing out minute metal particles like so much nano-sized grapeshot. Needless to say, it will take more than just one of these nanoscale motors to drive a spacecraft; Gilchrist envisages arrays of many millions of them being bolted onto a space vehicle. Even then they will not have nearly enough oomph to launch a craft into orbit. Yet once up in space Gilchrist’s “nanoparticle field emission thrusters”, or nanoFETs, will come into their own. Little by little, they should be able to accelerate spacecraft and propel them across the cosmos more efficiently than ever before. They promise to be far more versatile than existing thrusters, capable of getting a crewed mission to Mars, say, yet also allowing the crew to precisely control the craft’s position when it arrives in orbit. NASA seems to believe Gilchrist could be onto something. It has supplied $500,000 funding for his project from its Institute for Advanced Concepts (NIAC) in Atlanta, Georgia. If all goes to plan, his tiny engine could end up going a very long way indeed. Gilchrist’s exotic idea has a simple motivation: is there a way to build spacecraft more cheaply?