NASA has pulled back on plans to launch a 737-sized subscale test vehicle (STV) by 2016 to demonstrate a next-generation airliner or cargo aircraft.
"We've taken our foot off of the gas," Fay Collier, NASA's manager for the environmentally responsible aircraft programme, said on the sidelines of the American Institute of Aeronautics and Astronautics 50th annual sciences meeting.
NASA's aeronautics branch has been preparing to launch the STV programme for several years, but funding for the project has recently evaporated. "There is no funding" for STV, Collier said.
Instead, NASA's aeronautics community has returned to advocacy mode in the hope of regaining support for the test vehicle, which is among a small handful of experimental aircraft ever proposed for validating a primarily commercial mission.
The advocacy campaign will lean on the results of Phase 1 studies by three aircraft makers - Boeing, Lockheed Martin and Northrop Grumman.
All three of the studies determined that a suite of new technologies now in development can lead to a ground-breaking new airliner with a roughly 767-sized payload by 2025.
Each of the aircraft makers compared how new airframes, structures, engines and aerodynamic techniques can cut down emissions between an advanced "tube-and-wing" and a more radical design.
In the latter category, Boeing studied two different kinds of blended-wing bodies powered by either three open rotors or two advanced turbofans. Northrop studied a flying wing resembling a scaled-up version of the B-2A bomber with embedded propulsion. Lockheed's designers considered a boxed-wing twinjet.
Although the studies proved the advanced concepts would be more efficient and quieter, the same technologies applied to conventional tube-and-wing airframes are also very effective.
NASA's study focused on applying new techniques to improve laminar airflow, advanced composites to reduce weight, ultra-high bypass engines to burn fuel more efficiently, new combustors to cut harmful emissions, and new ways of integrating engines into the airframe to shield noise levels.
As a result, fuel burn on a tube-and-wing airframe was reduced by 43%, with one-third of the improvement driven by the engine alone, Collier said.
However, the study also showed that the only way to achieve NASA's "N+2" environmental goals is to move to a new airframe configuration. The tube-and-wing concepts fall about 8% short of the fuel burn target, and up to 12dB short of the noise reduction target, Collier said.
Source: Flight International
