The SPRINT aircraft must demonstrate glide stability, an efficient transition between hover and forward flight, and a distributed energy system that powers all propulsion systems during this transition.
The Defense Advanced Research Projects Agency ( DARPA ) is developing an innovative vertical take-off and landing aircraft: SPRINT.
This initiative, called SPRINT (Speed and Runway Independent Technologies), involves a collaboration with prominent aeronautical companies such as Aurora Flight Sciences, Bell Textron, Northrop Grumman and Piasecki Aircraft Corp. With an initial budget ranging between $15 and $20 million, the goal is to develop a prototype aircraft by 2027 that offers significantly higher speeds and operational capabilities in areas without traditional runways.
DARPA’s SPRINT project: Exceeding the speeds of the Osprey
Navy Commander Ian Higgins, director of the SPRINT program, highlights that speed is a crucial requirement for this new aircraft. The SPRINT aircraft is expected to reach speeds between 400 and 450 knots (460 to 520 mph), far exceeding the V-22 Osprey’s top speed of 270 knots.
This increase in speed represents a considerable challenge, given that the aim is to surpass the Osprey by more than 100 knots, which implies overcoming physical limitations with innovations in the propulsion system.
Additionally, the SPRINT aircraft must demonstrate glide stability, an efficient transition between hover and forward flight, and a distributed energy system that powers all propulsion systems during this transition. This approach does not focus on survivability or potential payload but rather on overcoming existing technical barriers in vertical take-off and landing aviation.
Regarding operational freedom, DARPA allows participating companies to decide on critical aspects such as the crew, autonomy and semi-autonomy of the aircraft. This openness in the design reflects the project’s innovative approach, where “everything has yet to be decided,” according to Higgins.
Divergent approaches in design and technology for the SPRINT aircraft
The proposals of the companies participating in the SPRINT project reveal a diversity of approaches and technologies. For example, Bell Textron introduced a tiltrotor design for an unmanned aircraft, combining a helicopter’s hover capabilities with a jet aircraft’s speed and survivability. Bell is actively testing technologies such as the folding rotor and flight control at Holloman Air Force Base in New Mexico.
Aurora Flight Sciences, a subsidiary of Boeing, is developing a high-lift, low-drag fan-wing aircraft using a mixed-wing body and integrated engines for forward flight, along with integrated fans for vertical flight. This design is inspired by projects such as the Boeing X-48 and the Excalibur unmanned aircraft, which uses jet vertical lift with retractable electric fans.
SPRINT contracts cover an initial six-month conceptual design phase. By May 2024, companies will have to demonstrate the viability of their concepts to advance to the next phase, where the completion of the preliminary design and a reduction in the number of participants is expected.
Potential military applications and prospects of the SPRINT aircraft
Commander Higgins highlights the wide range of potential applications for high-speed vertical lift aircraft in the military context. These include special operations, mobility and logistics, personnel recovery, medical transport and evacuation missions. In future war scenarios, the ability to take off and land in unconventional environments, such as streets or open fields, and then quickly withdraw could be crucial.
Currently, the technologies under development for SPRINT are not intended for any specific project, and although they may not materialize in an existing program, DARPA hopes that technological advances derived from the project can be integrated into future programs. Higgins emphasizes that DARPA focuses on tackling difficult problems that may or may not be feasible, thereby exploring the current state of the art in military aviation.
