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When you are already getting $1.5K to $3K for regular trans-atlantic business class how do you upsell that? Actually the Brits had gotten cold feet before the first Concorde ever went into service but the French held them to their agreement to partner in the venture. They were only too happy to ground the entire fleet, forever because of an accident involving a single plane. Imagine grounding all 737's forever because one of them crashes.
I think Lighter Than Air passenger airships should make a come-back. Wouldn't that be something. I never understood why the Hindenburg ended airship use anymore than I understood the grounding of the entire fleet of SST's. The Hindenburg didn't have to use Hydrogen it was designed with Helium in mind. Hydrogen was, and is, vastly cheaper, however. I think, in 2016 safe, efficient LTA craft could be made using hydrogen lifting gas. The FAA would never allow it for passenger travel but for cargo, air-mail?
the reason the hindenburg essentially killed the dirigible, is because it exploded into flames and killed a number of people. and the reason it used hydrogen instead of helium is because the US, the largest supplier of helium in the world, would not sell it to the germans since we were still adversaries after world war one, and with hitler in power at the time, we were not going to be allies anytime soon.
I really appreciate all this information. I have always wondered why we have made lightyears of progress with other technologies but it still takes five hours to get from Philly to LA, just like it did 20 years ago. Didn't know about the sonic boom and the gasoline factor and other limitations.
The sonic boom rule is self-induced. In the 1960s a small but vocal group of people, remembering the proliferation of military sonic booms over populated areas, ensured the US SST would not be built, or at least not fly over CONUS. (I remember the booms... I grew up under a military operations area [MOA]) However, for the military, there is no restriction on supersonic flight over the continental US except in a few areas such as the Grand Canyon, Zion, Yellowstone, etc. A military aircraft can fly above Mach 1.0 above 30,000 feet nearly anywhere; the restriction applies to civilian aircraft. Any noise is so attenuated that it's largely unnoticed or even imperceptible to ground observers. When conducting functional check flights I would routinely go to 1.4 or above during an engine check, at an altitude of 40,000 feet. No one on the ground would notice. Why it can't be repealed to allow civilian supersonic flight is likely a NIMBY issue, not for this forum (go to Politics and Other Controversies) but the reality is it should be a non-event. There are a number of places where supersonic flight is allowed down to the surface (restricted areas, such as R-2301) or higher, in MOAs such as the Sells MOA.
The greater limitation, outside of rule-making, is economic; it just plain costs a lot in the way of fuel to go fast. Example, at 40,000 feet. F-16, max range, 0.83 mach fuel flow is ~ 2500 lbs/hr. MIL thrust (full throttle) results in 0.9 to 0.95 mach, depending on configuration, can push 1.00 if totally clean at ~ 4500 lbs/hr. Push it up to 5 stages of afterburner and eventually I could see 1.8 mach and a fuel flow of ~ 12,000 lbs/hr (a clean F-16 carries 7200 lbs). Not a lot of utility for that kind of speed and reduced range and endurance.
The greater limitation, outside of rule-making, is economic; it just plain costs a lot in the way of fuel to go fast. Example, at 40,000 feet. F-16, max range, 0.83 mach fuel flow is ~ 2500 lbs/hr. MIL thrust (full throttle) results in 0.9 to 0.95 mach, depending on configuration, can push 1.00 if totally clean at ~ 4500 lbs/hr. Push it up to 5 stages of afterburner and eventually I could see 1.8 mach and a fuel flow of ~ 12,000 lbs/hr (a clean F-16 carries 7200 lbs). Not a lot of utility for that kind of speed and reduced range and endurance.
now imagine four engines burning that much fuel per hour. and that is at cruise altitude. take off and getting to altitude you can burn a lot more fuel very easily.
It would be awesome if flight could be achieved in say 4 without massive complexity
You flew an F-16
Passenger planes fly normally fly at around Mach .78 to .90 or so. There is a reason they are limited to speeds just under Mach 1: While their speed of the craft itself is, say, .78, you have to remember the speed of the air over any airfoil on the plane is traveling faster than that. In fact, the primary purpose of the wing is to accelerate the air over its upper surface, which is what provides lift. So the plane itself is flying at .78, or .82, or .90, etc, the speed of air over the wing can be very close to mach 1. So if a certain plane is design-limited to .78, but then accelerates to say .85, the air over the foils can go transonic and supersonic. Big deal, right? Well it actually is. The shock waves associated with doing so imposes tremendous structural stresses and control issues due to the sudden sharp rise in drag due to the shock waves that develop when airflows become sonic. This can cause all sorts of issues: mach buffet, mach tuck, control surface snatching, etc. Modern airliners just aren't built to withstand those kinds of stresses and issues. They could of course design the wing a bit different to get that additional slight bump in speed, but there's always a trade-off, and those trade-offs aren't worth it on passenger carrying planes.
All these threads pointing out how much fuel is needed to go supersonic forget one important detail: it's been done! Supersonic flight over the Atlantic was about as routine as routine gets and while the Concorde was in operation they filled every seat. I mean... comercial jet airliners are FAR thirstier than turbo-props... if the logic that is being entertained as to why we cannot have supersonic passenger transport held all the way to the reductio ad absurdum we might as well wonder why anyone needs transcontinental flight to take 4 hours. 8 is perfectly reasonable and the fuel costs are orders of magnitude less. Can you say PROFIT boys and girls... no, fuel costs are not the reason. The reason is profit, and they are making plenty of it with the status quo. Fuel has not been as cheap as now for 20 years and looks to get even cheaper. I suspect that notwithstanding this no airline mogul will place an order to Airbus to build a supersonic airliner. Those kinds of visionaries that put the dream ahead of profit just for the sheer Sacre Bleu of it are long gone. Today's airline moguls are at the behest of shareholders and the bottom line of dividends and stock prices are all shareholders care about. If they thought they could roll us all back to tubo-props they would do it in a New York minute.
There's something called "critical Mach number", which depending on a vast bevy of variables (like wing-sweep and airfoil design), is somewhere between 0.65 and 0.9. It's a sharp rise in drag-coefficient, completely unrelated to the rise in dynamic pressure as the flight speed increases. This is why passenger-jets and military transports all cruise at more or less the same Mach number… which is around 0.8.
Some years ago, there was interest in an oblique flying wing, which theoretically has the lowest wave-drag (the part of drag that's associated with compressibility-effects, i.e., Mach number). It has awful problems with stability and control, with internal volume and all sorts of systems-integration issues.
When we say that "technology is more advanced now" than XYZ years in the past, we mean primarily electronics and computers, biology/medicine, and materials. The mantra is info-nano-bio. Mechanical engineering (civil, aeronautical, naval) really hasn't advanced much since the 1960s.
What if a Concorde II were to be built today? How would it differ from its predecessor? Well, the main difference would be… wiring! The weight of wiring and electrical-systems aboard the Concorde was a very high fraction of total gross take-off weight. Another advancement would be the reduction of something called engine TSFC, which is jargon for fuel-burn for a given amount of thrust. Annually re-running the numbers for "what if" scenarios that might finally justify a supersonic transport, has been a sort of pornographic dreamer-hobby in the aerospace industry for decades. OK, maybe now we finally have lighter materials (composites) or better wing-optimization. Well, no. We don't. At least not enough.
Quote:
Originally Posted by Leisesturm
All these threads pointing out how much fuel is needed to go supersonic forget one important detail: it's been done! ...
It has. And going to the moon has also been done. Could we do it today? What's the business-case? Who is going to pay for it?
Quote:
Originally Posted by Leisesturm
If they thought they could roll us all back to tubo-props they would do it in a New York minute.
We're doing exactly that. It's called the open-rotor, powered by a Brayton-cycle core (a jet) but spinning two rows of open blades. 10% fuel savings over an ultra-high-bypass turbofan (we think).
All these threads pointing out how much fuel is needed to go supersonic forget one important detail: it's been done! Supersonic flight over the Atlantic was about as routine as routine gets and while the Concorde was in operation they filled every seat. I mean... comercial jet airliners are FAR thirstier than turbo-props... if the logic that is being entertained as to why we cannot have supersonic passenger transport held all the way to the reductio ad absurdum we might as well wonder why anyone needs transcontinental flight to take 4 hours. 8 is perfectly reasonable and the fuel costs are orders of magnitude less. Can you say PROFIT boys and girls... no, fuel costs are not the reason. The reason is profit, and they are making plenty of it with the status quo. Fuel has not been as cheap as now for 20 years and looks to get even cheaper. I suspect that notwithstanding this no airline mogul will place an order to Airbus to build a supersonic airliner. Those kinds of visionaries that put the dream ahead of profit just for the sheer Sacre Bleu of it are long gone. Today's airline moguls are at the behest of shareholders and the bottom line of dividends and stock prices are all shareholders care about. If they thought they could roll us all back to tubo-props they would do it in a New York minute.
what you are forgetting though is that while the concord was in fact built, and flown commercially for a couple of decades, they LOST MONEY on just about every flight. why? because while flying .85 mach uses a lot of fuel, to go supersonic requires a lot more fuel than you realize. as sluggo noted, flying the f16 with a single engine at full military and going supersonic used 4500 lbs per hour of fuel. and that is with just ONE engine. the concord had four engines. and cruising at 60,000ft at mach 2.0, it burned 4800 GALLONS PER HOUR, which translate to 28,800lbs per hour of fuel(using the weight of 6lbs per gallon of jet fuel). so yes it WAS about fuel consumption.
I think Lighter Than Air passenger airships should make a come-back.
The very fact that you wouldn't need hundreds or thousands of acres near a populated center to board such an aircraft should make them popular.
For instance San Diego has 640 acres for their airport in the city center. Half the passengers are trying to fly to the six airports within 500 miles (Phoenix, Las Vegas, Los Angeles, San Francisco, San Jose, and Sacramento). You have one runway which is being tied up by "local traffic" when it is badly needed for flights to the rest of the country and some international destinations. For instance San Diego's aging football stadium (166 acres) is 5-6 miles from the airport (640 acres), and in the center of the interstates and on the trolley line. The NFL team will probably abandon the city next year. It's a shame there is no LTA industry which could be included in the redevelopment of the site, so that the city has "local" air transport.
All these threads pointing out how much fuel is needed to go supersonic forget one important detail: it's been done! Supersonic flight over the Atlantic was about as routine as routine gets and while the Concorde was in operation they filled every seat. I mean... comercial jet airliners are FAR thirstier than turbo-props... if the logic that is being entertained as to why we cannot have supersonic passenger transport held all the way to the reductio ad absurdum we might as well wonder why anyone needs transcontinental flight to take 4 hours. 8 is perfectly reasonable and the fuel costs are orders of magnitude less. Can you say PROFIT boys and girls... no, fuel costs are not the reason. The reason is profit, and they are making plenty of it with the status quo. Fuel has not been as cheap as now for 20 years and looks to get even cheaper. I suspect that notwithstanding this no airline mogul will place an order to Airbus to build a supersonic airliner. Those kinds of visionaries that put the dream ahead of profit just for the sheer Sacre Bleu of it are long gone. Today's airline moguls are at the behest of shareholders and the bottom line of dividends and stock prices are all shareholders care about. If they thought they could roll us all back to tubo-props they would do it in a New York minute.
While it's not been directly said, that fuel expense is one reason why supersonic flight, while technically attainable since 1947, is not economically viable on a large scale. The massive fuel requirements to feed engines producing enough thrust while not producing a lot of drag the way a high-bypass fan does do three things: Cut into the bottom line and/or raise ticket prices to the point of being available only to a select few; add weight to the aircraft, which requires more structure and increases drag and thrust requirements (vicious circle); and reduce useful load.
The cost to develop a new airliner is enormous. The Airbus 350, according to open sources, cost €12 billion (US$15 billion or £10 billion) to develop, and that's for an airframe that exists in various forms elsewhere in the Airbus line. The 787 development and manufacturing costs are $32 billion. Even the 757 and 767, developed concurrently in the late 1970s, cost $4 billion. It's a risky venture, and some great designs (CV-990, L-1011) never paid for themselves.
The Concorde (and the TU-144 Concordski) was as much about national pride as anything else. So they were propped up by subsidies; they were money pits.
Last edited by SluggoF16; 02-07-2016 at 08:14 AM..
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but for cargo, air-mail?
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