Saturday, November 28, 2009
Welt has an interesting article in German from yesterday on a number of possible successors to the Concorde, which still remains the fastest civilian jet in history but eventually became unworkable and also had a really loud sonic boom that made it impossible to fly over populated areas. Newly proposed jets are a great deal smaller than the Concorde with seating for only a bit over a dozen people, but the sound they make is minimal. In fact, their smaller size may ensure more successful sales since the private business airplane market is full of people that would gladly spend more money for an airplane that would result in a savings of a few hours per flight. This includes not just businesspeople but also leaders and politicians from relatively small countries.
The article itself is fairly long, and here's one part of it.
It is the first civil supersonic jet after the Concorde, it's called QSST (Quiet Supersonic Transport), and on the pre-order list for this airplane is an impressive list of determined buyers. Above everything else though, this QSST is the first example of a new generation of private supersonic business machines for 10 to 50 passengers, all of which must overcome a crucial obstacle: an unobtrusive (i.e., mostly silent) breaking of the sound barrier.
The Concorde sounded on its last flight in 2003 over the Atlantic like a hammer of God: "Ba-BAam!" to the eardrums of sailors or whales. No wonder that it was unwelcome over populated areas, at least at supersonic speed.
The newly constructed and much smaller QSST from the American manufacturer SAI (Supersonic Aerospace International LLC) on the other hand is so quiet, that the American government could repeal the supersonic flight ban over the United States, or at least the manufacturers hope.
SAI ensures that the transition to supersonic speed at a height of 18,000 meters is only audible at a level of 65 dB. This is one hundredth that of the sonic boom produced by the Concorde, and is comparable to the sound made by a passing car at 100 km/h, or a conversation. The QSST costs 80 million dollars, and provides places for 16 passengers. The machine should be capable of flight in 2014, and delivery is expected in 2016.
Another model with a nearly identical price is Aerion Corporation's Supersonic Business Jet (SBJ). This long, cigar-shaped airplane is designed to efficiently fly very near the sound barrier at Mach 0.98, which would enable it to fly over the US without needing a change in the law.
The manufacturer also says that up to a speed of Mach 1.1 no boom can be heard on the ground, in what is known as a "boomless cruise". This is sigfinicant because unlike the US, many countries have existing rules that allow supersonic flight as long as no boom can be heard from the ground. Over the ocean the SBJ can fly at a speed of Mach 1.6 about double that of current airplanes. To bring all their conflicting requirements under one roof, the SBJ uses thin miniature wings instead of the typical delta wing design.
A third American project is currently progressing in the darkness: the Gulfstream Quiet Supersonic Jet (QSJ). There are no pictures of this one, except those produced by a wind canal test at NASA. An engineer there holds a strange combination of arrow-shaped wings and an long, pointed nose in the air stream. This lance-shaped nose is to extend to a length of over eight metres during flight, and at supersonic speeds splits the bow shock wave into several small, shallow waves. The company calls it the "Gulfstream Whisper" and shows an audio simulation of the expected noise heard on the ground as it passes over, to hundreds of environmentalists, politicians, critics and interested parties. Gulfstream is confident that the sound emitted at supersonic levels will be 10,000 times quieter than that of the Concorde, effectively making it no louder than normal ambient background sounds.
Europe to also make its own new supersonic aircraft
The French manufacturer Dassault is also working with 37 partners on a High Speed Aircraft (HISAC) quite similar to those proposed by the Americans: 8 to 16 passengers, modern environmental technology, a range of up to 9000 km and like the QSST, quiet enough that the sound heard on the ground as it passes overhead is no more than 65 dB. The model's form resembles that of the Concord. Even Japan's space agency JAXA is looking at an eventual successor to the Concorde, a small supersonic jet for about 30 to 50 passengers.