Boeing will be completing the advanced design work for the Experimental Spaceplane XS-1 programme run by the agency, which is part of the US Department of Defense.
The programme aims to create a new class of hypersonic aircraft that would bolster national security by providing short-notice, low-cost access to space.
XS-1 will allow launches to low-Earth orbit in a matter of days, compared with the months or even years of preparation currently needed to get a single satellite into orbit. Its recurring costs could be as low as $5m per launch.
Currently, the cheapest low-Earth orbit launches are provided by Elon Musk's SpaceX and can cost around $60m, depending on the mission.
The project is ambitious and requires "significant advances in both technical capabilities and ground operations," according to DARPA.
If it is successful it would "revolutionise" the US' "ability to recover from a catastrophic loss of military or commercial satellites, upon which the nation today is critically dependent."
It aims to build a fully reusable unmanned vehicle, roughly the size of a business jet, which would take off vertically like a rocket and fly to hypersonic speeds.
The vehicle would be launched with no external boosters, powered solely by self-contained cryogenic propellants.
Upon reaching a high suborbital altitude, the booster would release an expendable upper stage which could deploy a 1,360kg satellite to polar orbit - an orbit in which the satellite passes above both of the Earth's poles.
After deploying the satellite, the reusable first stage of the spaceplane would then bank and return to Earth, landing horizontally like an aircraft, and be prepared for the next flight, potentially within hours.
To test the spaceplane, DARPA and Boeing are planning to conduct a demonstration of XS-1 technology, flying 10 times in 10 days, with an additional final flight carrying the upper-stage payload delivery system.
"We're delighted to see this truly futuristic capability coming closer to reality," said Brad Tousley, director of DARPA's Tactical Technology Office, which oversees XS-1.
"Demonstration of aircraft-like, on-demand, and routine access to space is important for meeting critical Defense Department needs and could help open the door to a range of next-generation commercial opportunities."
BBC
