|Boeing hypersonic concept|
Back in March I posted about an "American Concorde" plane that never really took off (no pun intended). Then yesterday at Instapundit, there was news of another proposed hypersonic passenger jet. Looks like we might get another airliner that could jet past the speed of sound.
Let's let Popular Mechanics explain:
I'm very much looking forward to flying on a hypersonic airliner in the near future. Though I hope it wouldn't take 20-30 years, I don't think I want to wait that long for my first overseas vacation!Boeing has revealed its first-ever concept for a hypersonic passenger plane that could cross an ocean in two hours for military or commercial customers. Debuted at an aerospace conference in Atlanta today, the design shows that the aerospace giant is ready to compete for this high-flying piece of the aviation future.“There is an inherent value in speed,” says Kevin Bowcutt, Senior Technical Fellow of hypersonics in Boeing Research & Technology....Although the airplane Boeing showed off today is just a concept and will certainly change before its possible flight in 20 or 30 years, Bowcutt can showcase the engineering decision-making that goes into such a vehicle.You don’t need (or want) to go Mach 5 during takeoff. Boeing’s designers envision using a commercial turbofan engine capable of a wide range of speeds that can be bypassed when it’s time for the airplane to really zoom. Besides, a traditional engine’s fan blades would disintegrate at such velocities. While traveling at hypersonic speeds, you don’t need fan blades to compress air anyway because the speed of the craft does that for you.That’s why most modern hypersonic jet designs rely on a ramjet, which uses the plane's forward motion to compress air, to reach truly awesome speeds. “The turboramjet would be designed to valve the air so it bypasses the (turbofan) engine and dumps into a combined afterburner ramjet,” Bowcutt says. “That same afterburner would function as a ramjet.” The ramjet would propel the vehicle to Mach 5, fast enough to get from New York to Tokyo in about 2 hours.Such speed influences the design in radical ways that can be seen in the render. For one thing, as airplanes go faster, the ratio of lift–to-drag (the thing that makes airplanes fly) drops.