NASA is working on a concept for a next-generation aircraft called STARC-ABL (single-aisle turboelectric aircraft with an aft [at the rear of the aircraft] boundary-layer propulsor).
It looks similar to a traditional jet aircraft, say a Boeing 737, but with slightly smaller engines. Not a dramatic design departure, but STARC-ABL’s tail features a “T-tail” horizontal stabiliser configuration with a boundary-layer ingesting (BLI) ducted fan on the tail, which is driven purely by electric power derived from generators mounted to the underwing engines.
The wing-mounted engines supply 80 per cent of the thrust required during takeoff and 55 per cent at cruise, while the tail-mounted, all-electric BLI turbofan accounts for remaining thrust. Researchers predict a potential fuel consumption improvement of roughly 10 per cent using this system.
“I feel we are at a tipping point in commercial aviation,” says Jim Heidmann, manager of NASA’s Advanced Air Transport Technology Project (AATT). “We are exploring and developing game-changing technologies and concepts for aircraft and propulsion systems that can dramatically improve efficiency and reduce environmental impact and accelerate the introduction of new aircraft.”
Several vehicle-level development challenges remain: how to balance aerodynamic efficiency, appropriately optimise the engines and aft BLI fan, validate the BLI benefits, store energy, compensate for additional weight, and meet safety and operational requirements.
NASA is now looking to industry and academic expertise for solutions. It has awarded 12-month contracts to Boeing, teamed with Georgia Tech; and Liberty Works with ES Aero, to develop preliminary single-aisle, 150-seat aircraft designs using promising electric-enhanced propulsion and vehicle configuration concepts.
The year-long study will also reveal new development approaches and any unforeseen technological hurdles, as well as any safety and flight certification challenges that could get an aircraft like STARC-ABL or other next-generation, hybrid or turboelectric aircraft concepts aloft within 20 years.
The final reports will outline hybrid-electric and conventional single-aisle aircraft concept designs, technology roadmaps for the major electrical systems and aircraft subsystems, and the evaluation of the concepts’ performance against NASA aircraft metrics.
[The fan on the tail ingests and accelerates the boundary layer air, creating thrust. Image: NASA]