The Perfect Airplane
Fast, green, and quiet. Come on, brainiacs, you can do it.
- By Ed Regis
- Air & Space magazine, September 2009
Reaction Engines Ltd/Adrian Mann
(Page 3 of 4)
But if the A2 is not quite quiet and not quite green, at least there are nearer-term alternative technologies being developed and tested—the Quiet Supersonic Platform, for instance, which originated in 2000 as a Defense Advanced Research Projects Agency program. Its objective was to reduce the sound of a sonic boom to the point that supersonic flight over populated areas would become unobjectionable. To that end, DARPA contracted with Northrop Grumman, which proposed modifying the nose section on one of its F-5E fighters, thereby shaping the sonic boom into one less disruptive to the ear. (The classic sonic boom is a pressure wave with two sharp peaks in rapid succession, like a capital “N.” A shaped wave would have the first peak looking more like the lowercase version: n.)
Northrop Grumman conducted its Shaped Sonic Boom Demonstration out of Palmdale, California, on August 27, 2003, with mixed results. According to the bevy of microphones in place near Harper Lake (an hour’s drive northeast of Edwards Air Force Base), the resulting boom was measurably less intense than that of an unmodified jet of the same type that flew through the same airspace moments later (see “The Boom Stops Here,” Oct./Nov. 2005).
On the other hand, the reduction in intensity wasn’t perceptible to a mere human. “I was out there and listened with my own ears,” says an experienced NASA sonic boom listener (who wishes to remain anonymous to preserve his relationships with NASA contractors), “and to tell you the truth, I couldn’t hear all that much difference.”
Progress in the boom-busting business has been slow and incremental. But even if the sonic boom could be changed from a loud clap to the sound of rolling thunder (nobody thinks it can be eliminated entirely), the public’s stomach for even soft sonic booms is an unknown and is further subject to the vagaries of politics.
“Politicians have overdone these things,” says Joseph Schetz. “In the public mind, the sonic boom was going to mow down buildings and knock over cows, kill whales. It’s literally like slamming a door.”
Matters are even worse when it comes to the touchy matter of alternative fuels. Researchers have proposed all sorts of sources—soybeans, sunflower seeds, babassu nuts, coconuts, palm oil, and algae—for biofuels. Some of these wild potions have even been tested in flight, in genuine, honest-to-God airliners.
In December 2008, an Air New Zealand Boeing 747 departed Auckland carrying a blend of 50 percent Jet-A and 50 percent jatropha oil. (The jatropha plant’s seeds, when crushed, yield an oil usable as fuel.) Over two hours, one of the jet’s four engines ran on the blend and performed normally. A little over a week later, on January 7, 2009, a Continental Airlines Boeing 737 accomplished essentially the same feat over Houston, Texas. (Its particular blend was 50 percent Jet-A, 47.5 percent jatropha oil, and 2.5 percent algae.) Separately, Japan Airlines was planning to launch a Boeing 747 running on a biofuel component blended of one percent algae, 15 percent jatropha, and 84 percent camelina oil. (Camelina oil comes from an oilseed plant that also produces vegetable oil and animal feed.) Air France, to complete the picture, was contemplating the most radically chic and stylish fuel of all, made from little Roquefort cheese morsels rolled in crushed walnuts. (Not really.)
“The most attractive one, but at high cost, is algae,” says Schetz. “It grows very fast. It would be genuinely renewable. Plus, if you tailor your feedstock, you might end up with even more attractive fuel. You can’t tailor what’s in crude oil.”