During the past half a century, engineers have generally opted to use hydrocarbons, such as kerosene, or hydrogen itself, along with oxygen liquefied at low temperature, as chemical propellants. But kerosene and hydrogen have drawbacks, according to David Riseborough of C&Space in Seongnam, South Korea. "Burning kerosene produces soot, which deposits coking residues on engine surfaces, causing blockages and reusability problems," he says. Hydrogen, meanwhile, requires costly cryogenic storage that can be hazardous to operate and large, insulated tanks that take up space and weight.
Most people know natural gas as home-heating fuel, but methane may soon be powering spaceships into orbit and beyond. Rocket researchers worldwide are now working on engines that burn methane rather than conventional liquid propellants.