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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.
:(
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.
The performance section of this is most interesting though: The designed thrust/weight ratio of SABRE ends up several times higher--up to 14, compared to about 5 for conventional jet engines, and just 2 for scramjets. This high performance is a combination of the cooled air being denser and hence requiring less compression, but more importantly, of the low air temperatures permitting lighter alloy to be used in much of the engine. Overall performance is much better than the RB545 engine or scramjets.
The engine gives good fuel efficiency peaking at about 2800 seconds within the atmosphere. Typical all-rocket systems are around 450 at best, and even "typical" nuclear powered engines only about 900 seconds.
The combination of high fuel efficiency and low mass engines means that a single stage to orbit approach for Skylon can be employed, with air breathing to mach 5.5+ at 26 km altitude, and with the vehicle reaching orbit with more payload mass per take-off mass than just about any non-nuclear launch vehicle ever proposed.
Like the RB545, the pre-cooler idea adds mass and complexity to the system, normally the antithesis of rocket design. The pre-cooler is also the most aggressive and difficult part of the whole SABRE design. The mass of this heat exchanger is an order of magnitude better than has been achieved previously; however, experimental work has proved that this can be achieved. The experimental heat exchanger has achieved heat exchange of almost 1 GW/m^3, believed to be a world record. Small sections of a real pre-cooler now exist.
The losses from carrying around a number of engines that will be turned off for some portion of the flight would appear to be heavy, yet the gains in overall efficiency more than make up for this. These losses are greatly offset by the different flight plan. Conventional launch vehicles such as the Space Shuttle usually start a launch by spending around a minute climbing almost vertically at relatively low speeds; this is inefficient, but optimal for pure-rocket vehicles. In contrast, the SABRE engine permits a much slower, shallower climb, air breathing and using wings to support the vehicle, giving far lower fuel usage before lighting the rockets to do the orbital insertion. And there it is. That's why a vaporware tag might be applicable, this is still just a 'plan' and not actually in production right now. Still, it is massively safer to test prototypes of this than a scramjet or ramjet. That's one thing good going for it.
If they can pull off that precooler and heat exchanger, they're in business.
My work here is dung.
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
They're claiming a price point comparable to current business class fares. There are enough business class fares sold currently to support a small fleet of such airplanes flying a few flights on the relevant long-haul routes. Anyone willing to pay for business class is certainly willing to pay a similar amount (or probably at least a moderate premium) to cut their flight time from 12+ hours to 2-4.
I can't speak to the details of this specific airplane, mostly because those details don't exist yet, but there has been significant work lately in reducing sonic booms through careful airframe shaping. They can probably fly supersonic overland as long as they're at altitude and not near population centers -- but I certainly can't guarantee that, and it's certainly subject to regulatory issues. Of course, the market *might* be big enough even with only the transoceanic flights -- LA to Sydney, Tokyo, Beijing, NYC to Western Europe, and possibly a few others.
Like you, I think the issues are more regulatory than technical. However, I think they have a lot more to do with development schedules and costs than they do with the existence of a sufficiently large market. If they can get the money and build it on the budget they say they can, the market will be there. Of course, that's a really, really big if.
Actually, the hole in the ozone layer is caused by CFCs, or chlorofluro compounds, and is currently shrinking.
Quis custodiet ipsos custodes?
Well, the SABRE engine is definitely not vapourware (nor it's predecessor, the LACE), so prospects of them getting the SCIMITAR design refined to production level are pretty high. I'd put my money on them becoming engine manufacturers and another company designing and building the airframe, but you never know...
MODS!
I can't believe you guys gave this joke an "Informative" rating... of course, I fully expect to be modded down as a Troll for criticising the moderators, but here's some info for you clueless newbs...
Lempel-Ziv compression
Huffman compression
As you can see, these are forms of data compression, not the compression of gasses, as would be used in a ramjet engine. Please, please have an idea of what you're reading about before marking something "informative". This may deserve a "Funny" mod, but it's not "Informative" - at least, not about the topic at hand.
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
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.
There is Mechaphilia; attraction to machines.
It might be classified as a sub-variant of that.
Or would Aeromechaphilia be a better word?
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