DARPA has selected Aurora Flight Sciences to move into the detailed design phase of the Control of Revolutionary Aircraft with Novel Effectors (CRANE) program:
This follows successful completion of the project’s Phase 1 preliminary design, which resulted in an innovative testbed aircraft that used active flow control (AFC) to generate control forces in a wind tunnel test. Phase 2 will focus on detailed design and development of flight software and controls, culminating in a critical design review of an X-plane demonstrator that can fly without traditional moving flight controls on the exterior of the wings and tail.
The contract includes a Phase 3 option in which DARPA intends to fly a 7,000-pound X-plane that addresses the two primary technical hurdles of incorporation of AFC into a full-scale aircraft and reliance on it for controlled flight. Unique features of the demonstrator aircraft will include modular wing configurations that enable future integration of advanced technologies for flight testing either by DARPA or potential transition partners.
“Over the past several decades, the active flow control community has made significant advancements that enable the integration of active flow control technologies into advanced aircraft. We are confident about completing the design and flight test of a demonstration aircraft with AFC as the primary design consideration,” said the CRANE Program Manager Richard Wlezien. “With a modular wing section and modular AFC effectors, the CRANE X-plane has the potential to live on as a national test asset long after the CRANE program has concluded.”
The AFC suite of technologies enables multiple opportunities for aircraft performance improvements, such as elimination of moving control surfaces, drag reduction and high angle of attack flight, thicker wings for structural efficiency and increased fuel capacity, and simplified high-lift systems.
There are few details available now about how CRANE will stay stable in the air, Elizabeth Howell at Space.com notes, but a 2021 presentation by Alexander “Xander” Walan, program manager of DARPA’s Tactical Technology Office, provides some hints:
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.
Seems like an obvious usecase for electric propulsion; specifically, acceleration of air through ionization. Could be implemented via striations on and or through the wings and other structures, which could be used to enhance lift and velocity at a minimum, in addition to the possibility of finer aerodynamic control.