The U.S. Defense Advanced Research Projects Agency is teaming up with Boeing to design its Experimental Spaceplane, or XS-1, the agency touted on Wednesday, May 24.

The spaceplane, called Phantom Express, combines the legacy of the Space Shuttle and the Air Force's X-37B in a new class of hypersonic aircraft able to achieve an impressive feat: launching to low Earth orbit in days, rather than months or years.

"The XS-1 would be neither a traditional airplane nor a conventional launch vehicle but rather a combination of the two," announced Jess Sponable, the agency's program manager, in a DARPA news release.

The Phantom Express will lower launching costs to as little as $5 million or less per launch, with the added advantage of facilitating "launch on demand and rapid turnaround — important military and commercial needs for the 21st century."

Why The Phantom Express Is So Unbelievably Cool

The hypersonic spaceplane is designed as a reusable unmanned aircraft that operates using liquid oxygen and liquid hydrogen fuel.

Powered by the Aerojet Rocketdyne AR-22, a modified Space Shuttle engine, the XS-1 also incorporates lightweight cryogenic propellant tanks and super-strong and durable composite wings that can handle re-entry temperatures.

After competing with Masten Space Systems and Northrop Grumman in Phase 1 of the Experimental Splaceplane program, Boeing was chosen to build and test the technology for the XS-1, which will allow the spaceplane to reach high suborbital altitudes and deploy satellites weighing up to 3,000 pounds.

Another remarkable feature of the XS-1 is that it would be able to fly at hypersonic speeds of up to Mach 10, covering more than 12,000 miles per hour.

The Phantom Express will be roughly the size of a business jet and fairly similar to the X-37B in concept. However, how it gets up into space is a different story.

Unlike the Air Force's unmanned spaceplane, which launches atop an Atlas V rocket, the XS-1 will launch vertically on its own internal engines and will mostly like act as a more improved rocket — not intended to stay in orbit but to send spacecraft in orbit.

"Phantom Express is designed to disrupt and transform the satellite launch process as we know it today, creating a new, on-demand space-launch capability that can be achieved more affordably and with less risk," states Darryl Davis, president of Boeing Phantom Works, in a company news release.

The XS-1 Could Be Launched As Early As 2020

Once Boeing has finished designing, building and testing the spaceplane in Phase 2 of the program — which is expected to last through 2019 and includes 10 test fires of the propulsion system over a period of 10 days to make sure the engine is strong enough for quick turnaround maneuvers — DARPA hopes to begin flight tests in 2020.

In Phase 3, the agency has scheduled 12 to 15 flight tests, the first few being conducted as shakedown flights to test the XS-1.

Next, DARPA and Boeing plan to launch the Phantom Express 10 times over 10 consecutive days — initially at Mach 5 speeds and without payloads, then at speeds as fast as Mach 10 to deliver a demonstration payload weighing 900 to 3,000 pounds into low Earth orbit.

According to DARPA, the success of the XS-1 would revolutionize the United States' ability to recover from a catastrophic loss of military or commercial satellites. The agency hopes the program will encourage the commercial launch sector to adopt the XS-1 technology in the future.

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