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-foot wingspan and a 1,000-pound payload, as officials stated in an October announcement. The demonstrator will utilize an “off-the-shelf turbofan and turboshaft engines” to achieve a speed of 450 knots, exceeding the minimum requirement by 50 knots. These components will be integrated into an innovative “fan-in-wing” system, a blended wing body design that combines stealth, vertical flight, and enhanced payload capabilities.

This basic design could potentially be scaled up for various medium- and heavy-lift aircraft. Aurora officials mentioned plans for a manned aircraft with a 130-foot wingspan featuring four lift fans and a 40-foot payload bay. They claim that this FIW aircraft could meet or exceed the traditional payload capacities, ranges, and speeds of fixed-wing military aircraft while providing the tactical advantage of true vertical takeoff and landing.

Meanwhile, Bell Textron, the other contractor with a SPRINT contract, announced last month that it has completed wind-tunnel tests on its “Stop/Fold rotor system.” This technology will enable an aircraft to use rotors for vertical takeoff, which can then be folded backwards to switch to a different, likely faster and more fuel-efficient propulsion system. A related demonstration of this system took place in February 2023 at Holloman Air Force Base.

The SPRINT program, officially known as the Speed and Runway Independent Technologies program, is overseen by the Defense Advanced Research Projects Agency (DARPA) in collaboration with U.S. Special Operations Command. It aims to develop a proof-of-concept technology demonstrator capable of supporting military aircraft that can cruise at speeds of 400 to 450 knots and operate from unprepared surfaces in austere environments. A preliminary design review is scheduled for April 2025, with flight testing anticipated for 2027.

Analyst Jon Hemler from Forecast International noted that the program’s requirements highlight an urgent need for U.S. decision-makers, especially concerning future aircraft designed to meet extensive operational challenges in the contested Pacific region. As all four U.S. service branches are set to operate tiltrotor aircraft as the U.S. Army FLRAA fielding approaches the decade’s end, the stakes for delivering an effective design are notably high.