(3)NASA contractors Alliant Techsystems and XCOR Aerospace are developing a rocket engine powered by liquid methane. Earlier this year the companies conducted a series of successful test firings of their 7,500 pound-thrust LOX/methane engine (pictured, video(1)). Such technology could one day allow for the exploration of deep space, as methane can be found or made on many worlds throughout our solar system. Read more at NASA.gov(2).
Photo: Mike Massee/XCOR

1. http://science.nasa.gov/headlines/y2007/images/methaneblast/testfiring.wmv
2. http://science.nasa.gov/headlines/y2007/04may_methaneblast.htm
3. http://science.nasa.gov/headlines/y2007/04may_methaneblast.htm