The us National Aeronautics and Space Administration (Nasa) has scrapped its high-speed research programme aimed at creating a new supersonic transport. The project's chances looked good until last summer, when Boeing released a new study that showed a supersonic airliner would be much harder to build than expected. Instead of simply meeting the noise rules anticipated for the year 2010, according to Boeing, the supersonic airliner would have to be as quiet as future subsonic jets. These, the company says will be much quieter than today's aircraft. The French company Dassault has put its supersonic business jet on hold. Designers have found it would need a new and expensive engine ( Popular Science , Vol 254, No 6).