XS-1 (spacecraft)

[5] After several years of refinement and proposals, in May 2017, the Defense Advanced Research Projects Agency (DARPA)[6] selected Boeing for Phase 2/3 to build and test an XS-1 spacecraft (now called the Experimental Spaceplane program).

They promoted concepts such as reaching a Low Earth orbit within days, unmanned reusable rockets, external boosters being replaced by internal, self-contained cryogenic propelled boosters, the ability to deploy 900 to 3,000 lb (410 to 1,400 kg) payloads into polar orbit, composite-metallic wings that could withstand suborbital hypersonic flight and temperatures exceeding 3,000 °F (1,600 °C), autonomous flight technology developed by DARPA's Airborne Launch Assist Space Access (ALASA) program, and reaching Mach 10.

DARPA's last attempt was the Responsive Access, Small Cargo, Affordable Launch[10][11] (RASCAL) program in the early 2000s with the goal of placing 300 lb (140 kg) payloads in orbit for less than $750,000.

DARPA stated that the XS-1 was more feasible due to better technologies, including light and low-cost composite airframe and tank structures, durable thermal protection, reusable and affordable propulsion, and aircraft-like health management systems.

Unlike other DARPA programs that were handed off to parts of the United States military once proven successful, this initiative was designed from the start to be a direct partnership between the agency and industry.

In August 2015, Boeing, Northrop Grumman, and Masten Space Systems all received additional funding from DARPA to continue their design concepts for Phase 1B of the program.

[14] In July 2016, DARPA stated that they believed "the time is right for a renewed effort, one that began in 2013/14, but [in 2016 was] ramped up through a solicitation process, allowing for several industry concepts to be created.

The team also leveraged technologies developed during related projects for DARPA, NASA, and the U.S. Air Force Research Laboratory to give the government "return on those investments."

Their concept included a clean-pad launch[clarification needed] using a transporter erector launcher with minimal infrastructure and ground crews, highly autonomous flight operations, and horizontal landing and recovery on standard runways.

[16][clarification needed] The Boeing design was a vertical takeoff, horizontal landing (VTHL) craft[7] called Phantom Express, intended to increase the nation's access to space.