Roundup: U.S. military requests designs for XS-1 space plane

The U.S. military's plan to build a futuristic satellite-launching robotic space plane is moving forward. The Defense Advanced Research Projects Agency (DARPA) recently put out its official call for proposals seeking designs for its Experimental Spaceplane (XS-1), according to local media reports.

The XS-1 program aims to develop a reusable unmanned vehicle that would provide "aircraft-like access to space" and deploy small satellites to orbit faster and more affordably using expendable upper stages.

"Current satellite launch systems, however, require scheduling years in advance for an extremely limited inventory of available slots. Moreover, launches often cost hundreds of millions of dollars each, due in large part to the massive amounts of dedicated infrastructure and large number of personnel required," DARPA said in a statement on Monday.

Three groups are involved in DARPA's design efforts for the XS-1. The new announcement sets a deadline of July 22 for them to submit their design proposals. In early 2017, the agency is expected to select one group to move forward with the construction of an XS-1 prototype for flight testing.

According to the Pentagon's future-focused project's research agency, key XS-1 program technical goals include at its best performance, flying 10 times in 10 days, flying to Mach 10+ at least once and launching 3,000- to 5,000- pound (1,361 to 2,268 kilograms) payloads to orbit for less than 5 million U.S. dollars per flight.

DARPA' s been at the XS-1 program for a while. The program began in 2013 and is currently broken into three phases. DARPA announced in April that it had received funding from the Obama Administration to move into Phase II. But the latest announcement is for both Phase II and Phase III program, which overall objective is to "design, build, and flight test a reusable booster system prototype."

"What makes the new announcement stand out is that it seems almost impatient," the Popular Science reported, "space isn't necessarily hard, but it's hard to do cheap, and the cost savings are key to DARPA's whole vision of the XS-1 program".

Phase I sought to "evaluate the technical feasibility and methods for achieving the program's goals". In 2014 and 2015, during Phase 1, DARPA awarded funds to three groups working on XS-1 designs: Northrop Grumman, partnered with Virgin Galactic; Boeing, partnered with Blue Origin; and Masten Space Systems, partnered with XCOR Aerospace. The three groups have released simple, digital renderings of what their XS-1 designs would look like.

The XS-1 will not be the U.S. military' s only reusable space plane program. The Pentagon already has another reusable space plane in operation: the secretive X-37B program, looks much like NASA's retired space shuttles, only much smaller. It is boosted into orbit by a rocket and lands like an aircraft on a conventional runway.

The secretive X-37 program began as a NASA project in 1999 but was later transferred to the Pentagon. Currently, it's being run by the U.S. Air Force's Rapid Capabilities Office.

The two Boeing built X-37Bs have launched on a total of four missions over six years. Its third mission ended last October after a total time of 674 days in orbit. Just what they're doing up there is a mystery; most X-37B payloads are classified. Endit