Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: jr2 on November 29, 2012, 05:22:22 pm
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They figured out how to cool the air in the compressor from 1,000 degrees Celsius (1,832 Fahrenheit) to -150 degrees Celsius (-238 Fahrenheit) in 1/100th of a second, without frost forming on the heat exchanger.
from http://www.reuters.com/article/2012/11/28/us-science-spaceplane-idUSBRE8AR0V220121128 :
By Chris Wickham
LONDON | Wed Nov 28, 2012 11:39am EST
(http://s1.reutersmedia.net/resources/r/?m=02&d=20121128&t=2&i=679042980&w=460&fh=&fw=&ll=&pl=&r=CBRE8AR1A9R00)
(Reuters) - A small British company with a dream of building a re-usable space plane has won an important endorsement from the European Space Agency (ESA) after completing key tests on its novel engine technology.
Reaction Engines Ltd believes its Sabre engine, which would operate like a jet engine in the atmosphere and a rocket in space, could displace rockets for space access and transform air travel by bringing any destination on Earth to no more than four hours away.
That ambition was given a boost on Wednesday by ESA, which has acted as an independent auditor on the Sabre test program.
"ESA are satisfied that the tests demonstrate the technology required for the Sabre engine development," the agency's head of propulsion engineering Mark Ford told a news conference.
"One of the major obstacles to a re-usable vehicle has been removed," he said. "The gateway is now open to move beyond the jet age."
The space plane, dubbed Skylon, only exists on paper. What the company has right now is a remarkable heat exchanger that is able to cool air sucked into the engine at high speed from 1,000 degrees Celsius to minus 150 degrees in one hundredth of a second.
This core piece of technology solves one of the constraints that limit jet engines to a top speed of about 2.5 times the speed of sound, which Reaction Engines believes it could double.
SHROUDED IN SECRECY
With the Sabre engine in jet mode, the air has to be compressed before being injected into the engine's combustion chambers. Without pre-cooling, the heat generated by compression would make the air hot enough to melt the engine.
The challenge for the engineers was to find a way to cool the air quickly without frost forming on the heat exchanger, which would clog it up and stop it working.
Using a nest of fine pipes that resemble a large wire coil, the engineers have managed to get round this fatal problem that would normally follow from such rapid cooling of the moisture in atmospheric air.
They are tight-lipped on exactly how they managed to do it.
"We are not going to tell you how this works," said the company's chief designer Richard Varvill, who started his career at the military engine division of Rolls-Royce. "It is our most closely guarded secret."
The company has deliberately avoided filing patents on its heat exchanger technology to avoid details of how it works - particularly the method for preventing the build-up of frost - becoming public.
The Sabre engine could take a plane to five times the speed of sound and an altitude of 25 km, about 20 percent of the speed and altitude needed to reach orbit. For space access, the engines would then switch to rocket mode to do the remaining 80 percent.
IT COULD EVEN MAKE THE TEA
Reaction Engines believes Sabre is the only engine of its kind in development and the company now needs to raise about 250 million pounds ($400 million) to fund the next three-year development phase in which it plans to build a small-scale version of the complete engine.
Chief executive Tim Hayter believes the company could have an operational engine ready for sale within 10 years if it can raise the development funding.
The company reckons the engine technology could win a healthy chunk of four key markets together worth $112 billion a year, including space access, hypersonic air travel, and modified jet engines that use the heat exchanger to save fuel.
The fourth market is unrelated to aerospace. Reaction Engines believes the technology could also be used to raise the efficiency of so-called multistage flash desalination plants by 15 percent. These plants, largely in the Middle East, use heat exchangers to distil water by flash heating sea water into steam in multiple stages.
The firm has so far received 90 percent of its funding from private sources, mainly rich individuals including chairman Nigel McNair Scott, the former mining industry executive who also chairs property developer Helical Bar.
Chief executive Tim Hayter told Reuters he would welcome government investment in the company, mainly because of the credibility that would add to the project.
But the focus will be on raising the majority of the 250 million pounds it needs now from a mix of institutional investors, high net worth individuals and possibly potential partners in the aerospace industry.
STANDING START
Sabre produces thrust by burning hydrogen and oxygen, but inside the atmosphere it would take that oxygen from the air, reducing the amount it would have to carry in fuel tanks for rocket mode, cutting weight and allowing Skylon to go into orbit in one stage.
Scramjets on test vehicles like the U.S. Air Force Waverider also use atmospheric air to create thrust but they have to be accelerated to their operating speed by normal jet engines or rockets before they kick in. The Sabre engine can operate from a standing start.
If the developers are successful, Sabre would be the first engine in history to send a vehicle into space without using disposable, multi-stage rockets.
Skylon is years away, but in the meantime the technology is attracting interest from the global aerospace industry and governments because it effectively doubles the technical limits of current jet engines and could cut the cost of space access.
The heat exchanger technology could also be incorporated into a new jet engine design that could cut 5 to 10 percent - or $10-20 billion - off airline fuel bills.
That would be significant in an industry where incremental efficiency gains of one percent or so, from improvements in wing design for instance, are big news.[/hr]
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HEAT TRANSFER
THERMODYNAMICS
HOLY ****
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I like the 5-10% savings when you use the tech with standard air turbines.
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HEAT TRANSFER
THERMODYNAMICS
HOLY ****
As I said in #bp, this is what the Shivans use to dump BFRed heat. :p
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Now hang on a second, let's see here. This is going to be pretty rough since I don't remember if or how much the heat capacity of air changes with pressure and temperature and stuff and I'm just grabbing data off google here, but this should at least put is in some kind of ballpark...
0.886 kJ/(kg*K) * ~1088 kg/s * (1000 C + (-150 C)) ≈ 1.1 MJ/s
or something. That's a lot of heat getting sucked out really fast if I'm even close to correct here. :eek:
e: Need to start adapting these for refrigerators, kthx.
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I heard of Skylon first over 20 years ago. The fact that we haven't sunk more money into it is the prime example of how pathetic British science funding has become in the past few years.
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Skylon
Sky lon
Skynet
Cylon
:shaking: :shaking: :shaking: :shaking: :shaking: :shaking: :shaking: :shaking: :shaking:
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I heard of Skylon first over 20 years ago. The fact that we haven't sunk more money into it is the prime example of how pathetic British science funding has become in the past few years.
This is, sadly, why we invent much, but export little, because we usually sell the idea rather than fund it to completion. We try to market ourselves as an 'ideas country', but no-one ever stopped to think that you can sell a working theory once, or you can apply it and sell the product hundreds of times over.
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Skylon
Sky lon
Skynet
Cylon
my thought exactly.
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there was a bbc documentary on skylon i found awhile back.
*youtubes*
http://www.youtube.com/watch?v=vZ_a21fPkYM
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Skylon
Sky lon
Skynet
Cylon
my thought exactly.
Same here.
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Now hang on a second, let's see here. This is going to be pretty rough since I don't remember if or how much the heat capacity of air changes with pressure and temperature and stuff and I'm just grabbing data off google here, but this should at least put is in some kind of ballpark...
0.886 kJ/(kg*K) * ~1088 kg/s * (1000 C + (-150 C)) ≈ 1.1 MJ/s
or something. That's a lot of heat getting sucked out really fast if I'm even close to correct here. :eek:
e: Need to start adapting these for refrigerators, kthx.
Or about 1 MW, which is not really that much, power plants easily go over 100 MW :P The main issue with those is that they are extremely bulky and heavy, and require a lot of pumping power cause a high pressure loss in the flow - which is exactly the opposite of what you want for aerospace applications. If these guys have indeed made a compact, lightweight, low-pressure-loss heat exchanger, there's a lot of people who'll want to know how they did it.
For this specific application, the large temperature difference adds to the engineering challenge - just imagine the thermal expansion/contraction all the components will be going through. And the fact that they avoided frosting at -150 deg is an additional achievement. All in all, even if they don't make it into space, there will definitely be quite a few interesting spinoffs from this project. But of course, single-stage-to-orbit takes the cake!
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the 1 MW reactor at NC State is cooled with a 7 hp pump.
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the 1 MW reactor at NC State is cooled with a 7 hp pump.
Hmm, yeah, let me rephrase that part of my post. Due to the large surface-to-volume ratio inherent to heat exchangers, the loss of total pressure in the air flow boundary layer is significant. If this happens in the intake of a jet engine, this translates to a direct loss in engine efficiency. If it happens in a closed cycle, it means you need a stronger pump to drive the system.
But that's for the gassy part of the heat exchanger. In the fluid part, Reynolds numbers are generally much lower, hence so are boundary layer losses. Which explains how a 7hp pump can drive a 1MW heat exchanger.
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i have my concerns about the fragility of the heat exchangers. things like birds and even insects getting sucked in at take off could seriously damage the heat exchanger. the individual tubes appear very weak structurally. so il wait till they have a complete engine system before i completely drop the skepticism. fortunately a scaled down test engine is their next step, and they will probibly get the funding for that.
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i have my concerns about the fragility of the heat exchangers. things like birds and even insects getting sucked in at take off could seriously damage the heat exchanger. the individual tubes appear very weak structurally. so il wait till they have a complete engine system before i completely drop the skepticism. fortunately a scaled down test engine is their next step, and they will probibly get the funding for that.
If birds really are a problem you could still piggyback it on a carrier plane to altitudes where no bird has gone before :)
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Bah, birds can pose any jet engine a problem, heat exchanger or not. As for insects, I doubt they'd do any real damage (beside clogging up the pipes a little): they're tiny, and it's not like they're going through the heat exchanger at supersonic velocity either.
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Bird strikes were pretty much always a problem, even in prop-driven aircraft, IIRC. Ingesting a bird is never good for any engine. Insects shouldn't matter for Skylon, they're too small and fly too low.
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Ran across this comment, thought it interesting:
http://science.slashdot.org/comments.pl?sid=3280735&cid=42135799
On another list someone asked me to explain the press release. Here is my try.
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.
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You posted a slashdot comment from November, in a comment thread from an article from November, 4 Months after the topic died?
I mean.
This is info that is available for anyone who can wiki; it's nothing new. Why the **** did you do this?
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I stumbled across it and found it interesting. I would rather have seen it when I found the original article. Hence; I figured anyone who saw my first post but didn't have the inclination to go searching would find this info useful.
Basically, if I was reading my own post as someone else and was uninformed, I would appreciate it being done for me. If I was actually informed, it would just be background noise and I wouldn't really mind.
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You're either not seeing or ignoring the point.
You were necroing this thread for basically no good reason, ou did not post information that was in any way new. Presumably, given that we have no running discussion about Skylon's tech, I would have assumed that everyone who wanted to know about it back when this topic was current has already informed himself.
You bringing this topic back from the dead is a nono. Don't do it again.
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Is there a way to update your posts without marking it as new/edited? I actually would have done that if I knew how. I didn't bother to edit the first post because it will just show up in the updated topics anyways.
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For the record, I thought that was an interesting snippet that I would not have been looking for at this time, jr2. Thank you.
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i think their next step is actually building a complete engine, which is going to take time. then they are likely going to o through a validation process before they start building the ship.
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Hmm, so they're using helium as an intermediary, rather than cooling the air directly with LH2? Interesting, anyone have an idea on the advantage of that? I just see it adding weight and complexity... Most of today's rocket engine nozzles are cooled with LH2 as well, so it'd not like it couldn't be done (although the use case here is different, of course).
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jesus christ E, calm down. i found it interesting and i'm glad he posted it. unlike your responses to him.
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Hmm, so they're using helium as an intermediary, rather than cooling the air directly with LH2? Interesting, anyone have an idea on the advantage of that? I just see it adding weight and complexity... Most of today's rocket engine nozzles are cooled with LH2 as well, so it'd not like it couldn't be done (although the use case here is different, of course).
the helium loop is essentially a heat engine. heat sucked out of the air is used to power turbo pumps and the compressor. you still use a lot more lh2 to cool the helium than the engine can burn. even that is put to use in a ring of ramjets who's job is not to produce usable thrust but to reduce intake drag by accelerating surplus intake air. this engine design is ****ing awesome.
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I finally got around to watching that BBC documentary you posted back-in-the-day, Nuke. I think the engine actually might be even more f-ing awesome if they used an annular aerospike nozzle for the exhaust.
As per helium... it is heavier than hydrogen, and thus less likely to escape its containment. Being as active a gas as it is, well, it will still do a lot of escaping. But it's also non-reactive. If your heat exchangers are as fragile as they are, and they're being used to channel mass amounts of air to be combusted... you probably do not want to use a highly active, reactive gas like hydrogen to pump through the exhangers. Granted, carrying a separate set of gas tanks is a bit lossy, but when it comes to mitigating disaster, the weight gain is really worth it.
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they are using an expansion-deflection nozzel (http://en.wikipedia.org/wiki/Expansion_deflection_nozzle) called stern. i cant find any information on this particular nozzel. but it will have some of the features of an aerospike engine. both nozzels have altitude compensation features.