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Son of Concorde
targo writes "BBC reports that EADS is considering a new generation hypersonic commercial aircraft. "Son of Concorde" would be twice as fast, carry twice as many passengers while being much quieter than its predecessor. It would get from Tokyo to Paris in just two hours, US destinations are not mentioned.
However, as Japan's failure last summer suggests, it might not happen too easily."
2 hours to cover half the world... It almost sounds like a low-earth-orbit travel arc.
Supercruise is a fairly easy-to-understand phenomenon; in effect, it requires two things:
- lots of thrust from the powerplant;
- subsonic airflow in high quantities through the engine due to the way a "conventional" turbine operates, with slightly supersonic exhaust flows.
Normally, a turbine can't attain supercruise because of the latter; the airflow needs to be slowed considerably going through the powerplant in order to stop a shock stall (where the supersonic shockwave suffocates the powerplant).The powerplant behind the F-22 (Pratt&Whitney F119-PW-200) attains this primarily though a few good engineering tricks such as single-crystal-cast blades with a slightly shallower angle of attack than most; thus allowing the engine to operate at a higher temperature and pressure internally than is "normal". It has a lower bypass ratio (the ratio of cool air passing around the engine to that going through the engine) than most fighter-class engines; thus, it needs a smaller front fan, which in turn reduces the area causing a shock stall. It also wears out quicker, but that's another matter entirely. :)
High bypass ratios are great for fuel efficiency at subsonic speeds, but by virtue of the way these turbines work and their tendency to shock-stall when confronted with a supersonic airflow, are not much good for supersonic flight, and not for the nearly-supersonic airflows that supercruise requires.
A typical mid-to-high bypass turbine used in a fighter will have a bleed air system to reduce the airspeed running through the turbine; this has to be counteracted by dumping raw fuel into the bypass & exhaust (i.e. afterburner). Indeed, to get much over M1.0 the F22 needs to employ this same trick. A low bypass turbine can operate with input airspeeds closer to M1.0, which in turn means less air needs to be bled, while still producing a slightly supersonic exhaust out the rear end.
It appears the Beeb has confused peak speed with average speed.
According to the US Department of Agriculture, the Great Circle distance from Paris to Tokyo is 6033 miles. Let's round that to 6000 mi. The speed of sound varies with temperature, but using 750mph makes the math easy (at aircraft altitudes, the speed of sound is closer to 700mph).
If it could hold the fuel, the Concorde at Mach 2 (1500mph) could do 6000 miles in four hours. If the EADS jet achieves Mach 4 (3000mph), it could do 6000 miles in two hours. If the entire distance were covered at cruising speed.
My impression (purely from being a passenger) is that it takes half an hour or so for a typical commercial airliner on a 1000 mile flight to reach cruising speed and altitude; the plane will then be at cruising speed for about 60 minutes, and then another 30 minutes is spent in deceleration. Of the 2 hours spent in the air, only half of the time is actually spent at crusing speed.
How long would it take for the EADS-SS to reach Mach 4? And how long would it take it to slow down from that speed to the typical 150mph (+/-) landing speed that current runways are designed for? I doubt the typical passenger is prepared for Michael Schumacher / John Force g-forces on takeoff and landing.
Let's say the EADS-SS takes 45 minutes to reach Mach 4, and another 45 minutes to drop back to landing speeds. Assuming linear acceleration and deceleration, that's an hour and a half spent at an average speed of 1500mph. So 2250 miles of the trip takes 1.5 hours. Transiting the remaining 3750 miles at Mach 4 (3000mph) would take another 1.25 hours, for a total trip of 2.75 hours. [Ignoring any ground taxi times or other delays.]
I would think, fuel-wise (which is basically the only marginal cost of airplane flight), that going from Mach 2 to Mach 4 is more expensive than going from Mach 1 to Mach 2. On the other hand, Mach 1 -> 2 is done in denser air than Mach 2 -> 4, so maybe not.
This could be a great question for a final exam in Engineering Analysis and Synthesis.
Concorde didn't use its afterburners while cruising.
http://www.concordesst.com/powerplant.html
Perhaps you should think before you post?
not quite. I work for an airline. A positively giddy amount of work goes into flight planning. Shortest path comes into it if you're trying to be quicker, but these days fuel burn and thus cost matters a lot. Trying to maximize your tailwind, reduce headwind, avoiding restricted airspace and following airways (like an interstate in the sky) for air traffic control reasons. This might answer the "hops" you talk about. Its navigational beacons which are often at airports.
Which brings us to tracking. If you're over the open ocean you follow tracks. Its a bit like hunt for red october going through the canyons. This speed, at this altitude through these points to maintain separation. Over land, you can be spotted within a couple hundred miles by your ground-air comms. And theres a lot of those. You are almost right on the airports, depending on where you're flying, type of aircraft and and how many engines you must be within a certain flying time of a suitable airport. Its called ETOPS.
So lots of things to worry about, including weather, but it typically starts with shortest distance.