The US Defense Advanced Research Projects Agency (DARPA) is funding work on a second X-plane demonstrator that is expected to demonstrate concepts necessary for a “transformational combination of aircraft speed and runway independence.”
The program is dubbed Sprint and is a collaboration between DARPA and the US Special Operations Command (USSOCOM). The broad agency announcement with which DARPA is soliciting proposals said the goal of Sprint is to reach first flight of the demonstrator no more than 42 months from contract award.
This is the second “X-plane” program DARPA has started recently. A demonstrator named Crane is poised to demonstrate that it can fly without traditional moving flight controls on the exterior of the wings and tail. The agency has already contracted Aurora Flight Sciences for the second phase of the program that will demonstrate an aircraft design based on active flow control, a technology that enables on-demand addition of energy into a boundary layer for maintaining, recovering, or improving vehicle aerodynamic performance.
The Sprint demonstrator is not intended as a pre-production aircraft for a specific operational capability but as a proof-of-concept technology demonstrator. The project will seek to validate technologies and integrated concepts that can be scaled to different size military aircraft, provide these aircraft with the ability to cruise at speeds from 400 to 450 knots at relevant altitudes and hover in austere environments (near unprepared surfaces).
Among the requirements listed by DARPA for Sprint are the ability to cruise at or over 400 knots at a relevant altitude and perform basic forward flight maneuvers in a stable manner. It will also have to demonstrate the ability to hover and perform hover maneuvers in a stable manner.
The transition between hover, forward flight and high-speed forward flight modes in both directions in a stable manner is also among the requirements.
According to DARPA, the Sprint demonstrator will have to be based on existing engines/propulsion systems and should ideally have flight test endurance of over 1.5 hours and a flight radius of over 200 nautical miles.
The Sprint X-Plane is expected to have useable flight hours left after the DARPA flight demonstration and will likely transition to SOCOM for further evaluation, DARPA said. The SOCOM evaluation may include integration of a mission package, which means the X-plane should have allocations for space, weight and power for the mission package.