Space plane designs needed

The U.S. military's plans to build a satellite-launching robotic space plane are moving forward. On May 23, the Defense Advanced Research Projects Agency (DARPA) put out its official call for proposals for the futuristic space plane design. The goal of the Experimental Spaceplane (XS-1) project is to build a reusable space plane that, at optimal operation, should be able to fly 10 times in 10 days, at a cost of no more than 5 million per flight. Typically, space vehicles are not fully reusable, and the pieces that are reused need to undergo time-consuming safety checks between flights. XS-1 would be used primarily as a cheap and fast way to deliver satellites to orbit, DARPA officials said.