US Military's XS-1 Space Plane Will Be Built by Boeing (Video)

The U.S. Defense Advanced Research Projects Agency (DARPA) has picked Boeing to design and build the XS-1 military space plane, a robotic spacecraft for launching small satellites. Boeing's design, called Phantom Express, is shown here in an artist's conc
The U.S. Defense Advanced Research Projects Agency (DARPA) has picked Boeing to design and build the XS-1 military space plane, a robotic spacecraft for launching small satellites. Boeing's design, called Phantom Express, is shown here in an artist's concept. (Image credit: Boeing)

The U.S. military's new XS-1 space plane will be built by Boeing, and it's called the Phantom Express.

The Defense Advanced Research Projects Agency (DARPA) announced today (May 24) it had selected Boeing for the next phase of its XS-1 project, known as the Experimental Spaceplane, after an intense competition among aerospace companies. The XS-1 is aimed to be a completely reusable military space plane capable of launching 3,000-lb. (1,360 kilograms) satellites into orbit 10 times in 10 days. The spacecraft could dramatically reduce the cost of launches to $5 million per flight, DARPA officials said.

"The XS-1 would be neither a traditional airplane nor a conventional launch vehicle but rather a combination of the two, with the goal of lowering launch costs by a factor of ten and replacing today's frustratingly long wait time with launch on demand," DARPA program manager Jess Sponable said in a statement. "We're very pleased with Boeing's progress on the XS-1 through Phase 1 of the program and look forward to continuing our close collaboration in this newly funded progression to Phases 2 and 3 — fabrication and flight." [DARPA's Experimental XS-1 Space Plane in Pictures]

Phase 2 of the XS-1 program will have Boeing design, build and test a technology demonstration vehicle by 2019, according to the DARPA statement. A ground-based engine test will be included, to show the feasibility of firing the engine 10 times in 10 days, DARPA officials said.

The first test launches will begin with Phase 3, which aims to launch the XS-1 between 12 and 15 times in 2020.

"After multiple shakedown flights to reduce risk, the XS-1 would aim to fly 10 times over 10 consecutive days, at first without payloads and at speeds as fast as Mach 5," DARPA officials wrote in a statement. "Subsequent flights are planned to fly as fast as Mach 10, and deliver a demonstration payload between 900 pounds and 3,000 pounds [400 to 1,360 kg] into low Earth orbit." (Mach 5 means five times the speed of sound, which equates to 3,806 mph, and Mach 10, or 10 times the speed of sound, is 7,612 mph.)

Boeing's Phantom Express XS-1 design beat out concepts by two other teams: a partnership of Masten Space Systems and XCOR Aerospace, and the team of Northrop Grumman and Virgin Galactic.

Boeing's Phantom Express XS-1 space plane design is shown in launch position in this artist's concept. The autonomous spacecraft is designed to launch vertically, deploy a second stage payload in orbit and return to Earth for a runway landing. (Image credit: Boeing)

The Phantom Express XS-1 is designed to launch to the edge of space, and deploy a piggyback-mounted second stage that would carry a satellite the rest of the way into orbit. The space plane would then return to Earth to make a runway landing.

The XS-1 will launch vertically using an Aerojet Rocketdyne AR-22 engine fueled with liquid oxygen and liquid hydrogen. The AR-22 engine is a version of main engines that were used to power NASA's space shuttles, Boeing representatives said in a statement.

The Phantom Express will be built by Boeing's Phantom Works division, which also built the two robotic X-37B space planes that are currently in use by the U.S. Air Force for classified missions. The reusable X-37B space planes have flown four missions to date, each longer than the last, with the latest mission (called OTV-4) landing at NASA's Kennedy Space Center in Cape Canaveral, Florida, on May 7 after 718 days 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," Darryl Davis, president of Boeing Phantom Works, said in a separate statement.

DARPA officials said the rapid-turnaround goal of the XS-1 space plane and the technologies that make it possible won't benefit just the U.S. military. DARPA will publicly release some of its results from the Phase 2 and 3 trials, and share payload specifications for interested commercial companies, agency officials said.

"We're delighted to see this truly futuristic capability coming closer to reality," Brad Tousley, director of DARPA's Tactical Technology Office, which oversees the XS-1 project, said in the DARPA statement, "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."

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Tariq Malik

Tariq is the Editor-in-Chief of and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.