Beyond the Osprey: DARPA wants high-speed vertical takeoff X-plane

Stephen Losey

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The Defense Advanced Research Projects Agency is working with four companies to design an experimental vertical-takeoff-and-landing aircraft that can fly at speeds far faster than the V-22 Osprey.

The collaboration comes as the U.S. military considers how it might operate aircraft in areas that lack traditional runways.

DARPA calls its program SPRINT, for Speed and Runway Independent Technologies. In November, the agency awarded contracts to Aurora Flight Sciences, Bell Textron, Northrop Grumman and Piasecki Aircraft Corp. to start honing their ideas. The total value for these four deals, which cover the initial phase, could be worth $15 million to $20 million, depending on what options the agency exercises.

By spring of 2027, DARPA wants one of those companies to have finished designing and prototyping their aircraft, built it, and carried out its first flight.

Navy Cmdr. Ian Higgins, SPRINT’s program manager, said in a Dec. 15 interview that speed is one of the key requirements for this aircraft. When the SPRINT aircraft flies forward, DARPA wants it to reach speeds between 400 and 450 knots, or about 460 to 520 mph. The V-22 Osprey has a maximum speed of 270 knots.

“What we ... want to be able to achieve is higher-end speeds,” Higgins said. “We’re going another 100-plus knots beyond [the Osprey], which itself challenges physics if you were just to use the propulsion system that’s in the Osprey.”

Higgins said the SPRINT aircraft also must be able to hover and be stable, transition between hovering and forward flight, and have a distributed power system during that transition that effectively powers all the propulsion systems. Higgins said SPRINT is not focusing on the survivability or potential payload of these concepts.

When it comes to achieving those goals, DARPA is giving the competing companies wide latitude. For example, he said, companies can decide whether their aircraft should be crewed or uncrewed, or flown autonomously or semi-autonomously.

“Right now, it’s all over the place,” Higgins said.

Bell Textron will compete for the Defense Advanced Research Projects Agency's SPRINT X-Plane program. (Bell Textron)

Concept art so far released suggests the range of strategies companies might employ for their SPRINT submissions. In a Nov. 27 release, Bell Textron revealed art showing an Osprey-like tiltrotor design on an apparently uncrewed aircraft, hovering above a platform at sea.

Bell said its SPRINT submission will blend a helicopter’s hover capability with the speed, range and survivability of a jet aircraft. The company also plans to leverage its previous work on high-speed VTOL technology. Bell is conducting risk-reduction testing of its folding rotor, integrated propulsion and flight control technologies at Holloman Air Force Base in New Mexico.

Aurora, a Boeing subsidiary, said in its own release that it is designing a high-lift, low-drag, fan-in-wing aircraft that uses a blended wing body and embedded engines for forward flight, as well as embedded lift fans linked to its engines for vertical flight.

The concept image Aurora released shows its aircraft’s proposed blended wing body, not far off from the Boeing X-48 design. Aurora said it is also using ideas from its Excalibur uncrewed aircraft, which used jet-borne vertical lift with electric lift fans that retract into the wing during forward flight.

The SPRINT contracts so far awarded cover the initial six-month conceptual design phase. By May 2024, the companies will have to convince DARPA that their concept will work and can lead to a first flight in 2027.

DARPA will then cut at least one contender and move to the next 12- to 15-month phase. At that point, DARPA expects the companies to have their preliminary design complete, and the field will be further winnowed.

The potential uses for high-speed vertical lift aircraft are vast, Higgins said. They could include use by special operations forces, and for mobility and logistics operations, personnel recovery, medical transport, and evacuation missions, he added — anything that requires an aircraft to quickly move in and out of unusual areas. And in a future war, Higgins said, the military might need aircraft able to take off and land from streets, open fields, cratered flightlines or other locations without traditional runways — and then get away quickly.

“It really does open up the possibility of [being used in] all those mission sets,” Higgins said.

Right now, the technologies that would be used for SPRINT aren’t earmarked for any existing project. Higgins acknowledged the project may not turn into anything, but he hopes the tech could one day be folded into a program of record.

“The beauty of DARPA is we pose these challenging problems that may or may not be achievable, and we see what the current state of the art is,” Higgins said.