DARPA’s High-speed VTOL X-plane Passes Ground Effect Testing

Boeing subsidiary Aurora Flight Sciences is advancing the development of a high-speed vertical takeoff and landing (VTOL) military aircraft under DARPA’s Speed & Runway Independent Technologies (SPRINT) program. The SPRINT program, in collaboration with the U.S. Special Operations Command, aims to design and fly an X-plane that revolutionizes military transport with high-speed, runway-independent capabilities.

Aurora’s design is competing with Bell’s HSVTOL concept. The project involves creating a fan-in-wing design that could transform the way troops and cargo are transported. This aircraft, unlike VTOL-capable fighter planes like the F-35, will focus on high-speed transport missions, offering the ability to land virtually anywhere while significantly outperforming helicopters in speed. Aurora’s demonstrator, should it secure the contract, will be an uncrewed aircraft with a 45-foot wingspan, designed to carry up to 1,000 pounds of payload at speeds of up to 450 knots (518 mph or 834 km/h).

The key feature of Aurora’s design is the vertical lift system, which employs three fans—one in each wing and one in the fuselage. These fans, concealed by aerodynamic covers during flight, open when vertical lift is required. This system allows the aircraft to achieve VTOL capabilities while maintaining high speeds during cruise flight. Ground tests have already confirmed that the aircraft’s landing gear is high enough to avoid adverse effects during takeoff and landing.

While the initial demonstrator will be relatively small, the full-size concept envisions a much larger aircraft with a 130-foot wingspan, capable of carrying significantly more cargo. This larger version will feature four lift fans embedded in its wings, with complex slatted covers that may even provide thrust vectoring capabilities for enhanced stability and agility during hover.

Aurora’s design could also incorporate elements from another DARPA initiative, the X-65, which uses “active flow control” technology to manage an aircraft’s pitch, roll, and yaw without traditional moving control surfaces. This would involve jets of compressed air being used to control the aircraft’s movements, a futuristic approach that could eliminate the need for external moving parts.

Aurora Flight Sciences has already completed initial tests of its fan-in-wing design, using a small 4.6-foot model to validate the concept. These tests demonstrated that the aircraft’s design avoids ground effect issues like adverse pitching and “suck down effects” during vertical lift operations. Future tests will include wind tunnel testing of a 9-foot wingspan model to further refine the stability and control of the system, followed by additional aerodynamic testing using a 5.25-foot semi-span model.

The designs of both Aurora and Bell will undergo review in April 2025, with the final selection of the demonstrator expected to begin flight testing by 2027.

“The SPRINT program offers the opportunity to deliver a game-changing capability to the warfighter. High-speed, stealth, runway-independent transport could help keep warfighters safe and effective in contested environments, so no domain is out of reach for our U.S. military,” Mike Caimona, president and CEO of Aurora Flight Sciences said.