A bit more than halfway to the final-design deadline in DARPA’s SPRINT vertical-takeoff program, the two contractors have revealed new details about their candidates.
Aurora Flight Sciences is preparing an uncrewed demonstrator with a 45-ft wingspan and 1,000-pound payload, officials said in an October statement. The demonstrator will include an “off-the-shelf turbofan and turboshaft engines” to drive the aircraft to 450 knots, some 50 knots past the minimum requirement, the statement said.
These off-the-shelf components will be harnessed in the innovative “fan-in-wing” system that Aurora announced when the program launched last May: a blended wing body design that the company says will combine stealth, vertical flight, and fixed-wing payload and speed.
This basic design could be scaled up for a range of medium- and heavy-lift aircraft—say, “a manned, 130-ft wingspan aircraft with four lift fans and 40-ft payload bay,” Aurora officials said in their October statement. “The FIW aircraft could meet or exceed the payloads, ranges, and speeds typical of fixed wing military transport aircraft while delivering the tactical advantage of true vertical takeoff and landing.”
Meanwhile, Bell Textron, the other company with a SPRINT contract, said last month that it has completed wind-tunnel tests on its “Stop/Fold rotor system,” which will enable an aircraft to use rotors to take off vertically, then fold them backwards to allow a different, presumably faster and more fuel-efficient propulsion system to take over. (Here’s a February 2023 video of a Stop/Fold rotor assembly doing its thing on a test track.)
The SPRINT effort—formally, the Speed and Runway Independent Technologies program run by the Defense Advanced Research Projects Agency with U.S. Special Operations Command— seeks a proof-of-concept technology demonstrator whose technologies and concepts can power military aircraft of various sizes that can cruise at 400 to 450 knots and operate from unprepared surfaces in austere environments. Preliminary design review is scheduled for April 2025, with flight testing planned for 2027, according to the Aurora release.
The program’s requirements “underline an urgent need for U.S. decision makers eyeing future aircraft built for the vast range and distance challenges posed by operations in the contested Pacific region. With the U.S. Army FLRAA fielding set near the decade’s end, all four U.S. service branches will soon operate tiltrotor aircraft,” Forecast International analyst Jon Hemler wrote in a recent post. “In view of the long-term future of DOD aircraft acquisitions and likely every military branch as a customer on the line, the stakes to deliver an effective design are high.”
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