This wild DARPA CRANE X-plane could be a giant leap in aircraft design

an aircraft with triangle-shaped wings featuring a hole between the wings and the fuselage. the ground is blurry below, indicating fast movement
Artist's conception of a DARPA plane from the Control of Revolutionary Aircraft with Novel Effectors (CRANE) program. (Image credit: DARPA)

The U.S. Defense Advanced Research Projects Agency (DARPA) says it's time for some airplanes to drop elevators, flaps and rudders for flight control.

DARPA's new X-plane concept will remove these moving external control surfaces to reduce aerodynamic drag and increase fuel efficiency, contradicting a century of standard aviation design practices. But the advanced-technology branch of the U.S. Department of Defense says it has a workable alternative to keep control in the air at high speeds.

Aurora Flight Sciences received a design contract (opens in new tab) from DARPA Tuesday (Jan. 17) under the Control of Revolutionary Aircraft with Novel Effectors (CRANE) program, which seeks fly an experimental aircraft without moving joints.

The subsidiary of Boeing "will design a full-scale X-plane that relies solely on changes in air flow for in-flight maneuvers," DARPA wrote in a Tuesday tweet (opens in new tab) of Aurora's award. Should the concept succeed, officials added, the design will be "a new phase in creation of an aircraft."

Related: DARPA is exploring ways to build big things in space

Moving aircraft parts has been a necessary inconvenience for more than a century. On the one hand, control surfaces create drag and reduce fuel efficiency. Pilots, however, need to safely move the airplane around and elevators, flaps and rudders have been tried, tested and improved for decades.

DARPA is by no means the first to consider removing parts previously considered essential to flight operations. In 2018, a team at the Massachusetts Institute of Technology flew what they called (opens in new tab) the "first-ever plane with no moving parts", but that term was referring more to propulsion. MIT used an electric charge on the plane to stay aloft, an effect known as "ionic wind" — not traditional propellers or engine turbines.

Some aircraft of the past have done away with one or more traditional moving surfaces, however. "Tailless aircraft," for example, incorporate pitch and roll into the main wing but usually still require a rudder. Such aircraft have been around since at least the 1910s, with the now-retired supersonic Concorde aircraft as perhaps the most prominent example.

The last Concorde, a "tailless wing" type of aircraft, touches down at Filton airfield on November 23, 2003 in Bristol, England. (Image credit: Matt Cardy/Getty Images)

There are few details available now about how CRANE will stay stable in the air, but intriguing hints are available via a 2021 presentation (opens in new tab) by Alexander "Xander" Walan, program manager of DARPA's Tactical Technology Office.

Active flow control (AFC) uses a variety of methods such as jets of air or even electric discharges to shape or sculpt the flow of air over the aircraft, the presentation notes. DARPA seeks to use commercial parts where possible to provide affordable alternatives and to "fully explore the AFC trade space," meaning to seek technologies that could provide viable alternatives.

A slide from a 2021 DARPA presentation on the CRANE project outlining various methods for Active Flow Control (AFC). (Image credit: DARPA)

While no further details on AFC are available on DARPA's laconic CRANE website (opens in new tab), the Aurora announcement (opens in new tab) suggests their design would use "modular wing configurations that enable future integration of advanced technologies" to achieve AFC. 

That's not much to go on, but in the 2021 presentation, Aurora's bid pledged to model several conceptual wing designs to find the best one. Judging from available photos, it looks like the X-plane will use a type of "coplanar joined wing", which includes two forward wings and two aft wings instead of the traditional V-shaped wing on most commercial and military aircraft.

A DARPA graphic outlining various aircraft designs examined as part of its CRANE project. (Image credit: DARPA)

The next portion of CRANE, known as Phase 2, will entail designing and developing the controls and flight software. It will complete with a critical design review of the X-plane. DARPA may ask for a Phase 3 to fly a 7,000-pound (3,175-kg) X-plane demonstrator with AFC technology. No financial or timeline details were released.

Elizabeth Howell is the co-author of "Why Am I Taller (opens in new tab)?" (ECW Press, 2022; with Canadian astronaut Dave Williams), a book about space medicine. Follow her on Twitter @howellspace (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or Facebook (opens in new tab).

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell, Ph.D., is a staff writer in the spaceflight channel since 2022. She was contributing writer for Space.com (opens in new tab) for 10 years before that, since 2012. Elizabeth's reporting includes an exclusive with Office of the Vice-President of the United States, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and (soon) a Bachelor of History from Athabasca University. Elizabeth is also a post-secondary instructor in communications and science since 2015. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace