The Boeing Company was chose by DARPA to continue development process their version of future space plane known under XS-1 codename.
Boeing has been chosen from group of other companies which unfortunately did not reached advanced design work phase. Projects presented by Northrop Grumman Aerospace Systems and Masten Space Systems have Phase 1 have not met acceptance of DARPA. Boeing will now continue development of their vehicle through two other phases of development until first flight and putting vehicle into mass production. DARPA announced about decision on May 24.
XS-1 project started in 2013. Main objective was to create space plane able to fly ten times daily in a row; each time it should deliver to trajectory orbit 1800 kg of payload for Department of Defense. It should operate without crew and each flight should not cost more than $5 million. Space plane should be able to reach 12.5 Ma speed with construction combining composite materials and alloys.
Boeing remains one of the most experienced companies if we consider creating space planes. U.S. Air Force successfully uses their X-37 vehicle for long term space missions since 2010. Company surely will use their experience and maybe even some solutions designed for X-37 during development process of XS-1. At the moment main construction detail well known is propulsion - Aerojet Rocketdyne will deliver to XS-1 their AR-22 engine for the vehicle. XS-1 will be delivered to certain altitude on the top of the reusable booster and later it will be deployed and continuing flight with its own engine. If we consider that X-37 start mass is around 5000 kg and payload mass of XS-1 should be 1800 kg we can assume that it will be larger comparing to its predecessor with dimensions of business jet.