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Reaction Engines plan Mach 5 Airliner
What is? writes "A British company has designed an eco-friendly airliner that could make a trip from London to Sydney in under five hours. Reaction
Engines has received funding from the
European
Space Agency to design the plane as part of the
Long-Term
Advanced Propulsion Concepts and Technologies project. The
A2
airliner would be capable of carrying 300 passengers at speeds of up to Mach
5."
First, those look like low-bypass engines (yes, I know they are "normal" jet engines), which means very high exhaust velocities. The small wing also means high wing loading and high takeoff velocities. Those two facts seem to suggest a very loud plane which might run afoul of EU regs.
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Second, I can't help but think that fuel costs will kill this idea. GIven rising energy prices (and no large-scale miracle hydrogen factories on the horizon), the fuel costs will tend to track oil and nat gas prices. Even "free" wind/solar power won't help because a hydrogen factory would need to pay a competitive price for energy, which will be tied to the rising cost of fossil fuels and the rising global demand for energy.
That said, I'd love to fly in this thing even though the artists sketch shows a lack of windows due to heat issues
Two wrongs don't make a right, but three lefts do.
Price will come down if fuel economy is reasonable and there are enough airplanes and flights to amortize development costs over. My impression (I've been following them for a while, and talked to people who should know) is that they're technically competent, and if they say they can get the price down, they can -- but that they're being overly optimistic about the market. Of course, if the government is paying for a low of the development, that helps a lot.
Noise is actually quite amenable to a technical solution. The first problem (noise near the airport) is a result of high-power, high exhaust velocity engines, combined with a need to get up to supersonic speeds quickly. If, as they claim, the airplane is efficient in the subsonic regime as well, then there is less pressure to accelerate rapidly. Efficient low-speed operation also inherently implies a lower exhaust speed (which they discuss briefly: variable high-bypass flow), which implies less noise -- for a given engine, noise power scales roughly (very roughly) linearly with exhaust velocity.
Noise from sonic booms is remarkably controllable, with sufficient work on the precise shape of the airframe. The technology to do that, high performance CFD, simply didn't exist when the Concorde was designed. They don't discuss it, but it's far too early in the design cycle for that to mean anything. Right now they're basically just trying to build the engine and convince people that a market exists at a price point they can reach. That requires design studies and concept art, but it's not yet time to be fine tuning the aerodynamics.
I'd say the technical problems, including noise, are amenable to solution if they manage to get the funding they need without too much interference. The market ones, less so. I'm sure one day we'll see supersonic airliners, but there are some *major* non-technical hurdles in the way of building anything the size of an A380.
Of course, it's wicked cool and I'd love to see it happen. Especially since the basic engine technology is also behind their Skylon SSTO spaceplane concept...
Popular Science wrote an article about this plane: Article
Yeah, it's a dual-mode engine. If you do a little research on them, you'll probably find that aerospace designers discounted such designs a long time ago. The problem they ran into was that rocket craft spend so little time in the atmosphere that the extra weight and complexity incurred through dual-mode operation ends up gaining very little over a BDB. (Big Dumb Booster)
The only time they really make sense is for nuclear engines. In the case of nuclear, you can use anything that can be heated and exhausted as fuel. This leads to three options that can be used to power a Nuclear Thermal Rocket:
1. Pass air through the reactor, heating it up and using it as rocket exhaust. This is relatively low thrust and would only be useful in combination with another booster or to maintain velocity in the atmosphere.
2. Pass air through the reactor, heating it up and using it as rocket exhaust. As the air exits the engine, add hydrogen fuel for a second reaction. This greatly improves thrust at the cost of fuel efficiency. Perfect for initial takeoff.
3. Pass a stored, lightweight material like hydrogen through the reactor, heating it up and using it as rocket exhaust. Thrust is good in this mode, but not great. Depending on the design of the craft, this could be used 100% of the time or while in space.
Creating such "Tri-Mode" engines is reasonably straightforward and has been done. (e.g. The Triton Nuclear Engine.) I'll leave it as an exercise to the reader to understand why they're not already in use.
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Actually, the hole in the ozone layer is caused by CFCs, or chlorofluro compounds, and is currently shrinking.
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Hydrogen is normally produced via steam reforming and related processes (water gas shift reaction, coal gassification, etc), not electrolysis. That is, the hydrogen and the energy to produce it both come from fossil fuels (mostly natural gas, but oil and coal can both be used -- though in the case of coal all the hydrogen is coming from the water).
And actually, there is currently a *huge* hydrogen production industry. It's just mostly used on site at large plants rather than shipped to consumers as energy storage. Ammonium nitrate fertilizer is a *gigantic* market, and it's made by combining atmospheric nitrogen and hydrogen into ammonia, and then converting some of that ammonia into nitric acid before combining the two to form AN.
The availability of hydrogen is actually only a minor detail in this design. The price and the awkwardness of handling the ultra light weight ultra cold liquid are much more relevant.