British Skylon Engine Passes Its Tests 172
An anonymous reader writes "The BBC reports that the SABRE hybrid (part air-breathing jet, part rocket) that is intended to power the Skylon single-stage-to-orbit space plane has passed its final technical demonstration test, and is now looking for money (only £250m!) to prepare for manufacturing. If this goes ahead, travel into orbit from local airports (ideally, those close to the equator) will be possible. And quite cheaply. But might it have the same legal difficulties flying from U.S. airports as the Concorde did?"
Only £250m! (Score:5, Interesting)
Re:Only £250m! (Score:5, Funny)
I sense a Kickstarter in the offing...
What's the incentive for my $25? A free ride on cuise missile?
YEEEEE HAAAAAA!!!
Press release (Score:4, Informative)
Hypersonic engines are up against hard physics. The ram air heats so much in the inlet that it's hard for combustion to add much energy to make it go faster out the back.
The idea behind the SABRE engines is to cool the ram air before it is compressed. The heat exchanger to do this is what the press release is all about. With not much more than a ton of mass, it sucks 400 MW of heat out of the incoming air, dropping the temperature from 1500 C to -150 C in a few inches of heat exchanger that looks much like fabric because the tubes are so tiny.
The engine cycle also uses the temperature difference between the ram air and the LH2 to run the compressor. It takes close to 2/5th of the energy from burning hydrogen to liquefy it. The engines recover much of this by running a helium turbine on the temperature difference between the ram air and the liquid hydrogen flow to the engines. The turbine powers the compressor stage that raises the pressure of the -150 C air to rocket chamber pressure.
The design is extremely clever thermodynamics which also avoids most of the metallurgical problems of high temperature. Fabricating the air to helium heat exchanger was a very hard task. They have miles of tiny tubing, tens of thousands of brazed joints and they don't leak!
Using these engines and breathing air, the vehicle reaches 26 km and about a quarter of the velocity to orbit giving an equivalent exhaust velocity (back calculate from hydrogen consumption) of 9 km/s. That's twice as good as the space shuttle main engines. It is expected to go into orbit with 15 tons of payload out of 300 or 5% even though the rest of the acceleration is on internal oxygen that only gives 4.5 km/s exhaust velocity.
Leaving out the oxygen and using big propulsion lasers to heat hydrogen reaction mass, such a vehicle would get 25% of takeoff mass to LEO, reducing the already low cost by a factor of 5. That's enough to change the economics of power satellites from being too expensive to consider to a cost substantially less expensive than any fossil fuel.
But try explaining any of this in a press release.
Re:Only £250m! (Score:5, Insightful)
Nothing odd about it. The USPTO would grant a patent on the look and feel of dog eggs as trade dress if it were submitted.
A chimp flinging turds with 'Approved' printed on them would be a better and more selective system.
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Can't the chimp throw lot's of unlabelled crap too? just so the submitters know it's crap.
Re:Only £250m! (Score:4, Interesting)
One problem (Score:3)
Last I read, developing Skylon was going to cost about ten billion pounds (or maybe dollars, though it's a big number either way). So there's a big jump from having an engine to being able to fly into space from your local airport.
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Last I read, developing Skylon was going to cost about ten billion pounds (or maybe dollars, though it's a big number either way). So there's a big jump from having an engine to being able to fly into space from your local airport.
But how much of that has already been spent?
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Indeed. Even if the engine/rocket motor works as advertised, they would still need to reuse some kind of space shuttle tech to get back down. Whilst I admire (some) of the space shuttle tech, the jury is long ago in - massive expensive fail.
Re:One problem (Score:4, Informative)
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The propulsion system is completely different. The space shuttle was designed in the 70s and used the materials and design techniques of 40 years ago. There is no comparison.
^ This. Also, the original space shuttle design was completely borked by military demands to increase its size. The shuttle basically suffered major bloat and feature creep, which was largely responsible for its ineffeciency and unreliabilty.
Re:One problem (Score:4, Informative)
Actually, the precise military design requirement that borked it was that the shuttle craft had to be capable of re-entry and landing entirely over the US continental area. They didn't want to overfly Russia, China or Europe.
That meant that it needed to have a steep descent profile, which in turn meant a hot flight, which meant expensive and sophisticated heat protection which ended up not working very well.
The Skylon is entirely commercial, and will have a much more sensible re-entry profile. It will be able to slow gradually in the upper atmosphere and even, with it's unique engines, start up again and fly back into orbit should it wish....
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The shuttle basically suffered major bloat and feature creep, which was largely responsible for its ineffeciency and unreliabilty.
False. The original shuttle design was to be capable of High Earth Orbit and powered landing (i.e., could go around again if needed, just like a jet, rather than doing a dead-stick controlled crash as the shuttle-as-built did), but was Proxmired into what we got. The Dyna-Soar (the military shuttle-like design that was cancelled in favor of NASA's) was much smaller.
Re:One problem (Score:4, Informative)
Because of the low ballistic coefficient, Skylon would be slowed at higher altitudes where the air is thinner. As a result, the skin of the vehicle would only reach 1100 Kelvin (K). In contrast, the smaller Space Shuttle is heated to 2000 K on its leading edge, and so employs an extremely heat-resistant but extremely fragile silica thermal protection system. The Skylon design need not use such a system, instead opting for using a far thinner yet durable reinforced ceramic skin
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Wingspan will be based on (more or less) wing loading, which will be based on (more or less) landing speed.
Power gives you an option to go around. But any orbital space plane will carry plenty of energy as a glider.
The odd thing about the Skylon (Score:5, Funny)
Is the strobing red light on the front. Seriously, what the frak?
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Re:The odd thing about the Skylon (Score:4, Funny)
Is the strobing red light on the front. Seriously, what the frak?
It is actually a white light, but the doppler shift makes it appear red.
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And the way it's always looking for Sarah Connor.
What about India? (Score:2)
Re:What about the SGC? (Score:2)
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Screw US Airports (Score:3)
And their legal (read: environmental) difficulties.
Launch from somewhere accessible to the market via other modes, but with sane local regulations.
Problem solved.
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You will need a specially strengthened runway, so any legal trouble would be sorted out before that is built.
A normal airport would not be useful for skylon.
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New Mexico thank you, in the unfortunately named Jornada del Muerto basin.
http://en.wikipedia.org/wiki/Spaceport_America (wikipedia)
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Well you wouldn't launch from just *any* airport... you always launch eastward to gain speed from earth's rotation. And you wanna be as close to the equator as feasible, and you want lots of ocean or non-populated wasteland to the east of your launch site in case your rocket blows up. Which is why we launch from the east coast of Florida or Texas.
It would take at least a few minutes from liftoff to Mach 1, by which time the spacecraft will be over empty ocean anyways. So TFSummary about concorde noise is no
Depends (Score:2)
Well you wouldn't launch from just *any* airport... you always launch eastward to gain speed from earth's rotation.
That depends on what the purpose of your flight is. If you want to get into orbit you are correct but if you just want a sub-orbital hop between two points on the Earth's surface it doesn't really matter and given the current lack of large passenger destinations in orbit I would guess that this is the most likely initial application.
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"Well you wouldn't launch from just *any* airport... you always launch eastward to gain speed from earth's rotation. "
Actually, it takes off - and flies - like a jetliner, so orientation of the runway is not a factor. The pilot can turn the plane eastward after takeoff, and then gun the engine.
Re:Screw US Airports (Score:4, Informative)
The US "legal troubles" were a stalling tactic* back when Boeing was trying to build their own SST. The original grass roots "ban the bang" campaign was British.
*Do you really think Congress wouldn't have lifted the landing ban had the US version made it off the drafting board?
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Far from advising xenophobia, I'd still like to point out that US is a fucking big country. Most people in Europe, for example, have no idea what a "fucking big country" is. Even supposedly well of Germans [notalwaysright.com]. Given the scale of things, a "homegrown" product in the U.S. may be equivalent from something made elsewhere in Europe for someone from there, for example.
You mean Russia? (Score:4, Insightful)
Far from advising xenophobia, I'd still like to point out that US is a fucking big country. Most people in Europe, for example, have no idea what a "fucking big country" is.
You mean like Russia that is actually in Europe (at least the part that fits given that it is so large it spreads over two continents), contains 10 time zones, and has a land area almost twice that of the US?
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His point was that Europeans know about Russia, and that makes them acquinted with a "fucking big country".
Actually, it's mostly Americans who have no clue how big their country is, rich in natural resources, not densily populated and unscathed by wars, so they attribute their economical superiority merely to them being "American". Europeans know that only the EU as a whole compares to the USA.
As for your Godwin, what you call "love of government power" should be called "imperialism". Currently the only cou
Re:You mean Russia? (Score:5, Funny)
Many Europeans are terrible at geography.
Oh, the fucking irony.
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Read the last line of the OP.
.mil only (Score:2)
If this goes ahead, travel into orbit from local airports (ideally, those close to the equator) will be possible. And quite cheaply.
Misdirection. Ballistic aka spacex and competitors is always going to be cheaper. This only has .mil purposes. Excellent PR work, guys!
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Citation needed.
Why would throwing away half the craft and having to carry many tons of oxidizer, which the skylon does not need, be cheaper?
Re:.mil only (Score:4, Interesting)
Fuel is cheap: rocket designers dream of a future where fuel will be the primary cost of launching things into space. Developing a space plane is not, and you have to invest all that money before you even know if it will work.
SpaceX estimates for launches on a reusable Falcon are similar to the estimates for Skylon, and they can build up to it, starting with expendable versions that are proving the technology and making money. Skylon has the tricky 'give us ten billion and it will probably work' hurdle to jump over.
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All very good points. In addition this is NOT the time to be needing a 10 billion handout from either the UK or the EU. SpaceX is progressing incrementally to reusable staged rockets and does not need any more money than they are getting from their current workload. With the Skylon precooler only just exiting proof of concept tests & really being a barely tested hurdle, I don't see it going any further in today's economic environment.
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There will never be an economic environment that will satisfy people who don't want us to go to space. There will always be a fiscal crisis caused by people who don't want to pay taxes, worlds without end, amen. The human race also, on the vast whole, doesn't believe we are living on a planet. We're talking people, the majority, who think Jesus or Mohammed or the Messiah or the great wheel of destruction and creation is coming to end the world. They don't believe in an actual *world* - they think reality is
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Go ahead & rant against the Luddites & socialists who refuse anything new or refuse to spend on space "until X is fixed here on earth", but do note that your rant is only slightly related to my post.
Skylon is a British/European endeavor. How much the US spent on Afghanistan (or the much larger amounts spent every year on entitlements) has nothing to do with how much the UK/EU is willing to spend on a project. It's rather how much funding is left after tossing billions down the Greek sinkhole or the
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Fuel is cheap: rocket designers dream of a future where fuel will be the primary cost of launching things into space.
That will only happen, if you're not throwing away a vehicle every time you launch. Else you have to add the cost of the vehicle to the launch. This is where Skylon comes in. It's a completely reusable vehicle. What it doesn't have currently is a market which justifies spending ten billion dollars or euros. You have to have a lot of launches before the development costs become a small part of overall launch costs.
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That will only happen, if you're not throwing away a vehicle every time you launch.
Sure. But if Skylon meets the launch cost estimates I've seen, fuel will still be only a few percent of that cost.
As I understand it, they want to use air during launch to allow them to carry a bigger payload in an SSTO, not to save money.
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But if Skylon meets the launch cost estimates I've seen, fuel will still be only a few percent of that cost.
Doesn't matter. Lets say you blow $10B on R+D for a launch platform. Over the life of that platform, no matter how low the fuel cost, you MUST gross more than $10B revenue before you can dream of profit.
Competitor? Traditional tech means $2B in R+D for a launch platform. Over the life of that platform, no matter how low the fuel cost, you MUST gross more than $2B revenue before you can dream of profit.
Normally, in aerospace, you spend more money on R+D than on vehicles. So the vehicle cost doesn't real
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it can still save money and resources.
if very least, cary more into space and make less trips.
In any case it will still do more with less. which is good from all perspectives concerned.
Its like saying the burn rate in modern auto engines is higher because they want more horsepower to weight rather than fuel economy, while they get both.
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You might be onto something. Copenhagen Suborbitals is doing "damn simple" designs using common materials like steel. Sure they have different goals, but something disposable and cheap might be another approach.
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So what world do you live in where 250 million means 10 billion?
The world where space planes don't magically appear for free once you have engines for them?
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Rockets can't be cheap. They are not reusable (you can try to reuse certain parts, but you're going to disassemble and reassemble them in any case) and that is ALWAYS going to put a high lower limit for their price. In the best case, you'll be paying millions of dollars for person to get to a lower orbit.
Skylon spaceplanes can, in theory, lower that to perhaps several tens of thousands dollars. Definitely to the level of hundreds of thousands.
Re:.mil only (Score:4, Insightful)
Things are disposable _because_ they can be made very cheaply. Not the other way, generally.
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How's the reusable condom holding up?
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The junkyards are full of disposable cars and airplanes. Like the disposable razor, they last for a while then stop being useful. At that point, they're no longer economically repairable. It's just the time frame that's different.
B-52's don't fit the mould, however. I think they'll be around for the heat-death of the universe, or they run out of ECNs, whichever comes first.
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No, cars are not disposable - almost all cars work for more than 10 years (average age of a car in the US is 8.5 years). And planes most _definitely_ are not disposable - they can easily have 30-40 years of service. Most rocket components, on the other hand, are used exactly once.
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The junkyards are full of disposable cars and airplanes. Like the disposable razor, they last for a while then stop being useful. At that point, they're no longer economically repairable. It's just the time frame that's different.
Cars and airplanes aren't made to be single use or have single use components like all space launch vehicles today. Imagine what a car would cost if you needed to replace the camshaft after every trip (or even every 100KM), that's what cars would look like if they were designed like the space shuttle (yes, we'd have mass produced, drop in cam's, but they'd make motoring hellishly expensive).
What you are talking about is ordinary wear and tear. Whilst it cant be avoided but it's not a big problem as cars
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If you're paying $200,000 for a flight into space, the cost of a flight to the nearest suitable airport is noise in comparison. I'm far from convinced there's enough of a market for $200,000 London to Sydney flights to justify it as a high-speed airliner.
leaves me out (Score:2)
travel into orbit from local airports (ideally, those close to the equator) will be possible
Shucks, none of my local airports seem to be near the equator. And I don't fly since the TSA started assaulting and irritating travelers.
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Shucks, none of my local airports seem to be near the equator. And I don't fly since the TSA started assaulting and irritating travelers.
I guess the previous poster should have written "will be possible for those who are willing to make an effort".
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travel into orbit from local airports (ideally, those close to the equator) will be possible
Shucks, none of my local airports seem to be near the equator. And I don't fly since the TSA started assaulting and irritating travelers.
So take the train to orbit?
That name (Score:3)
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Re:That name (Score:5, Informative)
Good show, old chaps, but change the name. Sooner or later, a Skylon will turn on you.
No worries. The UK Ministry of Defense communication satellites are already called "SkyNet".
Misleading Title (Score:5, Informative)
The engine doesn't exist yet. This was a test of the pre-cooler. It is a critical component and it was important.
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It's a critical component, granted, but only one of several.
As an automobile analogy - this is like proving air flows through a spiffy new carburetor. Way cool, and very critical... but very, very far from a complete test of the carburetor, let alone of the complete engine.
Sabre remains a very long way away from being proven to work.
Re:Misleading Title (Score:5, Interesting)
This test used a large tank of liquid nitrogen as a heat sink.
Replacing your oxidizer tank with a coolant gas tank isn't a huge net gain. Any heat taken out of input air has to be put into the cooling system. Which is yet to be developed. The engine has to cool both the O2 and the inert parts of the air. My gut says: net loss for simply carrying coolant vs. simply carrying O2. A heat pump to fill this roll in flight is a major engineering challenge. It would require a metric assload of energy to operate.
Also note any space plane will need cooling for leading edges of flight surfaces. SR-71 did this by using pre-cooled fuel and running the fuel through heat exchangers on the leading edges just before burning.
They short circuited a huge engineering challenge by using a liquid nitrogen boiler as a heat sink.
Re:Misleading Title (Score:4, Insightful)
Hmmm, let's think. A space plane fueled by liquid hydrogen. Very cold liquid hydrogen. And lots of it. I wonder what they could use to cool the incoming air?
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Hint: The Air and hydrogen mix a fixed ratio. There will be much more air then Hydrogen (it's not pure O2). There will be more heat in the incoming air then the Liquid H2 can absorb.
Also note: in may (most) rocket designs the cold fuel/oxidizer is used to cool the combustion chamber. Already at a delicate balance.
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Hydrogen has a very high specific heat and heat of vaporization. From reading the wiki it says there is more hydrogen used for cooling than is needed for combustion. But part of the engine design has a part of the air bypass the compressor as well. The hydrogen is mixed and burned with this air outside the combustion chamber to recover some of these losses.
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So wiki agrees with my gut. Using extra fuel as coolant.
Air is about 21% O2. That leaves 79% inert gases being cooled. Also note: H2, having low atomic weight, should have relatively low specific heat vs most of the gasses in the atmosphere.
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Hydrogen has 14 times the heat capacity of air.
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Per tibits calculations below (which make sense as far as he goes), you use about 2.9% hydrogen by weight.
16*2.9=46.4%. Vaporization heat isn't enough to matter 0.45kJ/mol. As tibit says that's 1%.
So you'd have to start with much colder hydrogen, and oxidizer (near to absolute zero), and use the remaining tanks of fuel and oxidizer as heat sinks, and design one amazing trick heat exchanger to cool the helium loop, and find a way to cool the combustion chamber when you're feeding it relatively hot hydro
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Re:Misleading Title (Score:4, Informative)
Let's see. Air at atmospheric pressure has roughly 1kJ/(kg*K) heat capacity. It doesn't matter that they ram-compress thinner air, what matters is that after the ram the air will have roughly atmospheric pressure. We can assume that just to get a ballpark figure. There's about 23% by weight of oxygen in the air. When you burn hydrogen in oxygen, you join 2 mass units of hydrogen to 16 mass units of oxygen. You end up using only 2.9% of hydrogen by weight compared to weight of air, if you want a stoichiometric burn. They supposedly [wikipedia.org] cool the air down by 1140K.
So for each kg of air, you have to remove 1.1MJ of heat, and you've only got 29 grams of hydrogen to boil off. Vaporization heat of hydrogen is 0.45kJ/mol, or 0.45kJ/1g. So the boiling hydrogen can sink about 13kJ of heat, about 1% of what you need to sink. That's a no-go. It will be a no go even if all they get after the ram is 2% of atmospheric pressure, so we can be pretty sure it's no go period.
We get 286kJ/mol for combustion of hydrogen with oxygen, so we have available about 8.3MJ of heat from burning enough hydrogen to use up oxygen from a kilogram of incoming air. That may work out. Feel free to look at the Sabre cycle [wikipedia.org] and fill in the blanks as to required flow rates and temperatures, even in an idealized fashion. It should give an idea of the project's feasibility. I'm sure real engineers have already done the legwork on all that. Just that it's not as simple as "lots of very cold liquid hydrogen".
The real thing is their proprietary and at the moment confidential frost control. They've got those long tubes, they could put acoustic waves into them, hmm.
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Also, your calculation only allows for heat of vaporisation. The H2 will also be increasing in temp by about a hundred degrees, which will absorb a lot of heat also.
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Fixing my earlier mistake, it's even more: 6 times :)
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I've made a mistake, BTW, the 0.45kJ/mol is the *molecular* heat of vaporization, so that's really 0.28kJ/1g.
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My gut says...
It's the 21st century, hundreds of years into the Age of Reason.
WHY for the love of everything sane does anyone think what their gut says is remotely interesting or germane to any discussion of anything?
Announcing that you've not done any numerical analysis or quantitative reasoning regarding a purely quantitative question is a really, really bad way of convincing anyone rational you have anything interesting to say.
And as other posters have pointed out, because the people who are doing this are Not Idiots(
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And as others have pointed out, they will be wasting extra fuel because the air is hotter then the fuel is cold. Weather it is a net gain (carrying extra fuel/coolant and drag for air scoops vs. just tanking the Oxidizer) is not obvious. These people aren't idiots, but they aren't betting their own money ether.
Gut at an engineering level is about high level thought without running all the numbers. Particularly when you don't have all the numbers, but only a conceptual framework. For example: My gut tells
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My gut says: net loss for simply carrying coolant vs. simply carrying O2.
I'm no rocket scientist, but it seems that the big savings is achieved by using passing air as reaction mass in an efficient manner. From the wiki: [wikipedia.org]
Because the engine uses the atmosphere as reaction mass at low altitude, it will have a high specific impulse (around 2,800 seconds), and burn about one fifth of the propellant that would have been required by a conventional rocket.[34]
The page for the SABRE engine [wikipedia.org] lists an ISP of 3600.
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... big savings is achieved by using passing air as reaction mass ...
Oh man, bad choice of words. Sorry.
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The point of this discussion is where will they sink the heat of the incoming air. H2 fuel will not have anywhere close to enough cooling capacity. So they have to boil off something to cool the air (which is only 1/5 O2). Might as well just tank the O2 and skip the complications.
They could dump some more heat into the remaining fuel and oxidizer (to be used later in pure rocket mode). I still don't think it will have enough heat capacity.
As I said, it seems like perpetual motion with heat.
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As I said above. Clearly more heat in the air then heat capacity of cold liquid H2. Also liquid H2 is typically used to cool the combustion chamber.
Dumb Question (Score:2)
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Why does the input air need to be chilled? Does this have something to do with using hydrogen in a turbine engine?
Design considerations. The front of the engine intake is where they keep all the Coors Light.
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Coors light is not beer.
Re:Dumb Question (Score:5, Informative)
Why does the input air need to be chilled? Does this have something to do with using hydrogen in a turbine engine?
Covered here [wikipedia.org]. It's actually an interesting read. Put succinctly, as speed increases, the temperature of the air increases, reducing efficiency.
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Reducing efficiency, and imposing limits on materials.
What limited the speed of an SR-71 was that the compressor inlet temperature could not exceed 427 Celsius. Try to go too fast, and the inlet compression will heat up the incoming air too much.
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clip from online article regarding this intercooler:
But its success depends on the Sabre engine's ability to manage the very hot air entering its intakes at high speed.
These gases have to be cooled prior to being compressed and burnt with the onboard hydrogen.
Skylon would do the job of a big rocket but operate like an airliner from a conventional runway
REL's solution is a module containing arrays of extremely fine piping that can extract the heat and plunge the inrushing air to about -140C in just 1/100th o
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Because otherwise, once you further compress the air to pressures needed for rocket propulsion, it'll be way too hot to handle by any known materials.
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In your basic gas turbine thermodynamic cycle, the Brayton Cycle, combustion takes place on incoming gas that has been compressed. That's what your compressor stage is for in a jet engine. In a ramjet the kinetic energy of the air is converted to pressure by a converging-diverging compression shock nozzle. (We notice Sabre has a ramjet-type compression inlet). The process is so fast its adiabatic (no heat goes in or out). The more compression you can get before combustion the higher the efficiency.
Adiabatic
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Most rocket engines take advantage of the cold liquid H2 to cool their combustion chambers.
If the H2 is already heated the combustion chamber will melt.
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Boiling of the liquid hydrogen, if you don't want to dump any unburned H2 overboard, will absorb about 1% of the heat needed to be removed from the incoming airstream :)
life immitates art? (Score:2)
Hmm. Looks like kinda a mash-up of Serenity and the Pan Am Space Clipper.
(Is it too late to say "geek alert"?)
Who cares about US airports! (Score:3)
This is a very neat concept, and it has implications in regular jet travel as well as space travel. The ability to cool air and compress it that much in a regular jet engine could increase efficiency astronomically! The fact that this concept works could mean we see more economical jets before we see this in space travel.
I want the pre-cooler ... (Score:2)
... for use in global warming summers to get cool air. -140C sounds terrific.
The direction space travel should've taken (Score:5, Interesting)
Many years ago in high school I think, I wrote a report on the X-15 rocket plane. The impression I got was that, while vertical rocket technology got us further faster in the short term, a more gradual development of hypersonic planes would've been better in the long run. We might have had a whole generation of space planes lobbing satellites and even space tourists capsules cheaper, more safely, and with faster turn-around time. I'm not an engineer, so I could be completely full of crap, too.
posters are losing their touch (Score:2)
Nobody posted "....oops I thought it said 'Cylon' ..." yet.
fooey
Get real for a second (Score:2)
The FAA won't certify airplane engines to run on unleaded fuel because of the potential hesitation and reliability problems. They're not going to certify this. Oh maybe in a hundred years.
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I wonder if the engines could be useful even without the plane?
Strap a bunch of them, some disposable LH2 tanks and a parachute onto the side of a Falcon and drop them when you hit Mach 5. Should improve the mass ration no end.