Two companies – Gulfstream and Aerion – have announced new developments bringing them closer to a viable design for a supersonic business jet, although neither company has yet committed to developing and producing such a plane.
There are several obstacles to be overcome in designing a viable supersonic jet. Such a plane would need to be cost effective, and would need to be able to fly economically at both subsonic and supersonic speeds.
Most of all, the ‘Holy Grail’ of supersonic design is to come up with a plane that has an unobtrusive and inoffensive sonic boom. Currently, most countries prohibit planes from flying at supersonic speeds overhead, due to concerns (be they imaginary or real) about the impact of sonic booms. Gulfstream say they are “getting real close” to all of the requirements for an aircraft to meet a perceived noise level of 70dB while flying supersonic over land, and are lobbying international regulators (the ICAO) to get this set as a standard for acceptable sonic boom noise levels.
The noise threshold, which Gulfstream and NASA came to independently, can be compared to closing a good car door or a refrigerator.
The Gulfstream jet would cruise at Mach 1.7, which is about twice the speed of typical passenger jets at present. This does not mean that flight times would be halved. Flights would still be subject to all the normal taxi time and ground delays, and all planes operating below 10,000 feet are required to fly no faster than 250 miles an hour. In other words, a flight that is currently timed to take about one hour from engine start to engine stop would probably still take one hour. But a five hour flight might reduce to three hours, and a 10 hour flight might reduce to 5 1/2 hours.
Here is an interesting article, although fairly technical.