We didn't know how much it cost before -- but now we do. Last year, Elon Musk and SpaceX bravely promised to cut the cost of satellite launches by 75%. Instead of the $400 million that United Launch Alliance charges to put a U.S. military satellite into space, SpaceX says it will do the job for less than $100 million, and promises similar savings on smaller satellites. But can we cut the cost even more? Boeing's version of the DARPA XS-1 space plane. Artist's concept by Boeing. To infinity and beyond Cutting satellite launch costs is precisely the mission of a new project underway at DARPA, the U.S. Defense Advanced Research Projects Agency. Last year, DARPA initiated a project it calls "XS-1." Through it, DARPA aims to design and build a "space plane" that can launch from the ground like the space shuttle, fly to the very edge of space, then lob satellites the rest of the way into orbit before returning to land back on Earth like an airplane. If all goes as planned, the XS-1 space plane should make it possible to put small satellites (1.5 to 2.5 tons) into orbit at a cost of about $5 million apiece. That's a 92% cost savings on SpaceX's list price for a basic Falcon 9 rocket launch, and as much as a 99% reduction in the cost of a ULA launch. A successful XS-1 project could conceivably cut the cost of a space launch dramatically. Northrop Grumman's competing version of XS-1. Artist's conception by Northrop Grumman. Who will build it? As far back as last August, we knew DARPA was working on XS-1, and we also knew the names of the contractors that DARPA had hired to build it: What we didn't know was what the XS-1 project meant to... More