Steam engines seem like a distinctly 19th-century technology when compared to 21st-century spacecraft. Yet, designers are turning to steam engines of a sort for use on spacecraft. Surrey Satellite Technology Ltd. (SSTL), a British developer of microspacecraft, has successfully tested a steam-powered thruster on UK-DMC, a spacecraft built by the company and launched last fall. The thruster uses a small amount of water, heated to 200 Celsius, as the propellant. The steam generates only a minute amount of thrust–a few millinewtons–but that’s enough to change the orientation of the spacecraft. SSTL believes that water could prove to be an economical and environmentally-friendly alternative to current spacecraft thrusters that use cold nitrogen gas or hydrazine.