Research under NASA’s Environmentally Responsible Aviation (ERA) program has established that conventional tube-and-wing configurations will simply not cut it when it comes to meeting its noise, emission and fuel burn goals for the mid-2020s and beyond.
So it was with some interest that delegates gathered here at the American Institute of Aeronautics and Astronautics aerospace sciences conference in Orlando, Fla, viewed the finalists in NASA’s N+2 preferred system concepts competition. ‘N+2’ refers to a second generation of technology beyond today, and encompasses technology that could be in service around 2025. Boeing, Lockheed Martin and Northrop Grumman won contracts, and a finalist will be selected by year-end.
Blended wing concepts with open rotor and geared turbofans form Boeing's bid. (Boeing/NASA)
Boeing is proposing a blended wing body and, more interestingly, is configuring it with either two Pratt & Whitney geared turbofans, or the option of three General Electric/CFM Leap-X based open rotors. Lockheed Martin - revealing its most-progressive new home-grown airliner concept in three decades - gains points with a radical-looking option. Configured with a non-traditional, laminar flow, modified box-wing, the engines are tail-mounted. Northrop Grumman presents a notional double-fuselage study and says its final concept will “fall out of the study”.
Lockheed Martin is offering a highly-modified box-wing concept. (Lockheed Martin/NASA)
The coming year will focus on five main tasks, says ERA chief engineer Mark Mangelsdorf. The first will be to evaluate a full-scale concept, starting with studies of how the contenders could best fit into the FAA’s NextGen airspace plan. Task 2 will focus on meeting the preferred performance requirements. For example, the passenger vehicle should be able to carry a 50,000-lb. payload 8,000 nm. while the freighter should be able to carry a 100,000-lb. payload 6,500 nm. Each contender will compile concept data packages together with comparisons to a conventional baseline design.
Northrop Grumman's notional double-fuselage concept will likely be superseded by a less radical proposal. (Northrop Grumman/NASA)
Task 3 will sketch out a detailed 15-year technology maturation roadmap, while task 4 will focus on the “long poles”, or the critical technology demonstrations for the second half of the ERA program in 2013-15. “We’re also interested in technologies that apply to N+1 (nearer term single aisle concepts, or retrofitable to current 737/regional jet-class models),” Mangelsdorf says.
But it is Task 5, the conceptual design of a subscale test vehicle (STV), that really captures the imagination. With the same configuration as the full-scale concepts, and capability to fly at the same Mach cruise speeds, it will have retractable gear and be big enough “to demonstrate noise, emissions and fuel burn goals.” Initial feedback from teams suggests a “sweet spot” around 65% full-scale to enable, intriguingly, the use of “the thrust class of engines for the 737RS size,” Mangelsdorf says. What’s more, should NASA proceed with the STV, it could have a 20-year career as a testbed for other projects, including integrating unmanned platforms in the US National Airspace System.