An old means of propulsion may power the commercial airliners of the future, if the National Aeronautics and Space Administration is successful in redesigning the propeller.
NASA is developing propeller blades with a curved design that makes the turboprop engine it plans look something like a window fan. Unlike the old design, the tips of this propeller will be able to go at supersonic speeds, NASA says. That will allow it to push a commercial-sized aircraft quietly at about the same speed as today's jet engines.
But the main attraction of the newfangled prop will be its ability to conserve fuel. NASA predicts the new planes will be able to achieve high speeds while saving nearly 40 percent of the fuel that today's jets use.
''Propellers are just a more efficient way of producing thrust,'' said Paul Johnson, manager of NASA's advanced turboprop program. ''Compared to the aircraft of today, it would be a 35 to 40 percent improvement in fuel efficiency. Compared to the advanced jets now being designed, it would save 15 to 20 percent.''
NASA is working on the propeller design because aircraft manufacturers could not risk the money or time to develop such an untested system, Johnson said. It hopes to have a research aircraft ready before the end of the decade, he said, and then private aircraft manufacturers can decide if they want to make a commercial model.
''It's up to NASA to show the concept is feasible,'' he said, ''so that the manufacturers can put up the big money to develop the aircraft.''
While much of the rest of NASA's budget is being trimmed, Johnson said Congress is interested in accelerating work on the new turboprop. The House Committee on Science and Technology asked NASA to prepare a report on what would be required to advance the project by two years.