An artist's concept of DARPA's Experimental Spaceplane XS-1 , a proposed robotic space vehicle that could fly 10 times in 10 days and lower the cost of putting satellites in orbit.
In early 2017, DARPA is expected to select one group to move forward with the construction of an XS-1 prototype for flight testing.
In an era of declining budgets and adversaries evolving capabilities, quick, affordable and routine access to space is increasingly critical for both national and economic security," DARPA officials wrote in a statement on the agency's website.
"Current satellite launch systems, however, require scheduling years in advance for an extremely limited inventory of available slots.
"DARPA created its Experimental Spaceplane XS-1 program to help overcome these challenges and create a new paradigm for more routine, responsive and affordable space operations, reducing the time to get capabilities to space," officials said in the statement.
DARPA announced in April that it had received funding from the Obama Administration to move into Phase 2.