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Author Topic: Skylon Spaceplane  (Read 72018 times)

Offline SteveO

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Skylon Spaceplane
« on: September 09, 2007, 10:13:07 am »
I've seen the Reaction Engines Ltd Skylon spaceplane mentioned a few times already but I think it deserves it's own thread.

It looks cool and will only cost £10 billion(ish) to develop, so if it wasn't designed in Great Britain 'the land of lost opportunties' it would probably get built ;)

It looks pretty feasible and practical to me, what are your views on it?

Check out the website http://www.reactionengines.co.uk/ and A E Mann's fantastic artwork.

 

« Last Edit: September 09, 2007, 11:03:16 am by overscan »

Offline Orionblamblam

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Re: Skylon Spaceplane
« Reply #1 on: September 09, 2007, 10:48:32 am »
what are your views on it?

I always figured it'd snap in half on re-entry.
« Last Edit: September 09, 2007, 11:04:18 am by overscan »
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Offline flateric

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Re: Skylon Spaceplane
« Reply #2 on: September 09, 2007, 11:00:53 am »
It looks cool and will only cost £10 billion(ish) to develop

...how many times have we heard something like this...Energia Kliper estimates, for example, were '...just USD 880 mln"...interesting that this chedevre of Russian car industry, for example, was USD 2,4 bln to put into series. Other part of my wants Alan Bond to succeed, of course.
« Last Edit: September 09, 2007, 11:07:20 am by flateric »
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Offline Orionblamblam

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Re: Skylon Spaceplane
« Reply #3 on: September 09, 2007, 06:30:33 pm »
It looks cool and will only cost £10 billion(ish) to develop

...how many times have we heard something like this...

The problem here is that for Skylon to work, a number of currently unbuilt technologies would all need to be built and proven out. It'd suck to go ahead and build the thing only to find out that the engines will invariably stall out at Mach 8.3 due to some as-yet unseen physical principle. Ooops.
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Offline flateric

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Re: Skylon Spaceplane
« Reply #4 on: September 10, 2007, 12:54:51 am »
Interesting, was LACE ever operationally tested in flight ever?
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Offline Orionblamblam

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Re: Skylon Spaceplane
« Reply #5 on: September 10, 2007, 12:38:50 pm »
Interesting, was LACE ever operationally tested in flight ever?

Not as far as I'm aware. I would not be surprised if some componant testing was done... say, a KC-135 with an air liquifaction rig set up, but I'd be stunned if air was liquified, stored, and then fed into an engine to provide thrust. I'd be freakin' flabbergasted to discover that a complete LACE system that was anywhere near flightweight was ever *built,* much less flown.
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Offline Michel Van

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Re: Skylon Spaceplane
« Reply #6 on: September 10, 2007, 01:04:13 pm »
here Model of Sabre Engine



and who it sould work



back to LACE
was static Test of that engine ?
and wat of his "evil Brother" NULACE ?
NU stands for NUCLEAR  :o
I love Strange Technology

Offline SteveO

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Re: Skylon Spaceplane
« Reply #7 on: April 26, 2009, 12:14:05 pm »
Whatever we all think of Skylon I think we'll agree this video is pretty good  ;D

Skylon mission animation http://www.reactionengines.co.uk/skylon_ops_anim.html

Offline Proponent

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Re: Skylon Spaceplane
« Reply #8 on: May 04, 2009, 08:14:09 am »
It looks pretty feasible and practical to me, what are your views on it?

At first glance it seems like a no-brainer that an air-breathing vehicle makes sense.  A launch vehicle sitting on the pad is 90+ percent propellant, half or more of which is oxygen.  If you could get all of that oxygen "for free" from the atmosphere, then the lift-off weight would drop dramatically.  Not only would you not need to carry all of that oxygen and tankage for it, but for each kilo of oxygen you didn't carry, you'd need less fuel and hence smaller fuel tanks.  Now that you've got a much smaller vehicle (less than half the size), it should be cheaper to operate.

But when you start to think about the details, things don't look so rosy.  IIRC, scramjet SSTO designs usually switch from scramjet mode to rocket mode at a few kilometers per second, well below orbital velocity.  Things are better than they seem for the scramjet, because a conventional rocket will have burned more than half of its propellant just to get to, say, 1.5 km/s, but we're still a long way from orbit at the stage that a rocket has to take over anyway.

Then there's the fact that launch vehicles try to get out of the atmosphere quickly, to avoid drag losses and heating.  A scramjet-based vehicle, on the other hand, must remain in the atmosphere longer.  It will suffer higher drag losses and its structure will need to cope with substantial heating.

There is a fundamental limitation on how much the scramjet can help.  Getting to orbit is a matter of lifting yourself up to, say, 200 km and accelerating to about 7 km/s.  The first takes an energy of about (9.8 m/s2) * (200,000 m) or about 2 MJ/kg.  The second takes about 0.5 * (7,000 m/s)^2 or about 25 MJ/kg.  Now just think about all of that oxygen that your scramjet scoops up.  It is stationary with respect to the earth's surface.  Hence, although you don't have to lift the oxygen, you do have to accelerate it to your own speed, just to avoid slowing down, and then you have to accelerate it some more in order to get some thrust out of it.  Taking oxygen from the air helps with the 2 MJ/kg of lifting that has to be done to reach orbit, but it doesn't help with the much larger 25 MJ/kg's worth of accelerating that has to be done.

Even though scramjet SSTO designs switch from air-breathing mode to rocket mode at relatively low speeds, the stationarity of the air reduces the efficiency of the engine.  Suppose we're burning hydrogen, which gives us an exhaust velocity of about 4,000 m/s in a rocket engine, where the oxygen that is delivered to the combustion chamber is more or less stationary with respect to the chamber.  At 4,000 m/s, the oxygen atoms in the exhaust contain a kinetic energy of about 0.5 * (4,000 m/s)^2 = 8 megajoules per kilogram.  That's about how much useful energy we're extracting from combustion.  In the case of the scramjet, our oxygen come screaming in at, say, 1,500 km/s, so it has a kinetic energy of 1.125 MJ/kg.  Now we add 8 MJ/kg through combustion (assuming we can burn as efficiently as in a rocket engine, which is unlikely) to get a specific energy of 9.125 MJ/kg, corresponding to an exhaust velocity with respect to the atmosphere of 4,270 m/s.  So, with respect to the vehicle, the exhaust velocity is not 4,000 m/s, but just 4,272 m/s - 1,500 m/s = 2,770 m/s.  The simple fact that the oxygen we scoop up is stationary makes our engine less efficient.  [NB: This quick-and-dirty analysis ignores the hydrogen in the mass-energy balance, but it's a modest fraction of the total mass.]  The faster we go, the worse this problem gets.  The problem will be worse, too, if we use a hydrocarbon fuel, which has a lower exhaust velocity.  And this ignores the fact that the air we scoop up is mostly nitrogen, not oxygen.  I know there are ways of dealing with the nitrogen, but they add complexity and inefficiency.


IMHO scramjets are interesting and deserve further research.  But for SSTO applications, scramjet technology will have to be very much more mature than it is now to be worth the trouble.

Offline Simon666

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Re: Skylon Spaceplane
« Reply #9 on: May 05, 2009, 01:44:47 am »
The simple fact that the oxygen we scoop up is stationary makes our engine less efficient. 
Are you confusing ramjets and scramjets? Throughflow in a scramjet engine is supersonic, to avoid the heat and pressure generated as compared to slowing to subsonic in a ramjet.

Offline Proponent

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Re: Skylon Spaceplane
« Reply #10 on: May 05, 2009, 02:52:24 am »
The simple fact that the oxygen we scoop up is stationary makes our engine less efficient. 
Are you confusing ramjets and scramjets? Throughflow in a scramjet engine is supersonic, to avoid the heat and pressure generated as compared to slowing to subsonic in a ramjet.

My quick-and-dirty analysis is the best-case scenario, in which there are no losses due to slowing of the inflow as it passes through the engine.  As you point out, scramjets will operate closer to this limit than ramjets can, but they are still subject to it.

Offline PMN1

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Re: Skylon Spaceplane
« Reply #11 on: October 07, 2009, 09:09:30 am »
Interesting news in this month’s Spaceflight

The British spaceplane developer Reaction Engines celebrated its 20th anniversary in mid-August and revealed that it is planning to fly its Skylon spaceplane for the first time in 2018.

Also

Preliminary studies have begun to develop a larger version of the Skylon design. Skylon D1 will be capable of carrying a 25 percent larger payload into orbit than the current design. It will also be approximately 340 tonnes in weight at take off compared with the current 275 tonnes.
« Last Edit: October 07, 2009, 09:11:40 am by PMN1 »

Offline FutureSpaceTourist

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Re: Skylon Spaceplane
« Reply #12 on: April 17, 2010, 01:50:03 am »
A few months ago Reaction Engines released issue 1 of a 52 page Skylon User Manual for prospective clients! You can download it from http://www.reactionengines.co.uk/downloads/SKYLON_User_%20Manual_rev1%5b3%5d.pdf.

Offline aemann

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Re: Skylon Spaceplane
« Reply #13 on: May 13, 2010, 02:51:20 pm »
The SABRE engine is neither a Ramjet nor a Scramjet - "The SABRE engine is a combined cycle engine which air-breathes like a jet engine but with a pre-cooler heat exchanger in front of the turbine compressor. There is a secondary bypass ramjet in the nacelle, but this is subsonic combustion and so not a Scramjet."

The key to making it work is the heat exchanger, and the associated frost control. The engines can't stall at M 8.3, as they transition from air breathing to rocket mode at about M5.

They've been testing the pre-cooler heat exchanger at their test facility, and it's looking very good indeed. The only other major hurdle was demonstrating that a rocket can be cooled with LOX, and there's just been a successful test by EADS Astrium. They're currently refining the the design from the C1 config that is in all the illustrations, to the D1. Even I haven't seen that yet, but it will apparently be sufficiently different that you won't have to be a rivet counter to see the changes.

Surely it makes more sense to invest in technology like this - unproven or otherwise - than going back to building yet another missile and capsule system? Whatever happens, it'll create something new, or new ways of thinking about these problems at least. And you know what, it might just work... imagine that! A proper reusable system, on demand, with a decent payload that'll make access to space truly routine. I'm so disappointed that someone like Elon Musk with all his cash, has the 'vision' to build... a missile with a capsule. Here - build this instead, and change the world forever.

Offline Orionblamblam

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Re: Skylon Spaceplane
« Reply #14 on: May 13, 2010, 03:05:41 pm »
Surely it makes more sense to invest in technology like this - unproven or otherwise - than going back to building yet another missile and capsule system?

It depends greatly on what your end product and schedules are. if your goal is to have a relatively inexpensive manned launch system within a decade, then clearly you want to go with known technologies. If your goal is to spend lots and lots of money in the hope that several decades down the line you *might* develop a new piece of technology that will do something that simpler tech already does, then hey, by all means, invest in the unproven.

Rocket engines work. SABER engines, scramjets, liquid air cycle engines, MHD ramjets... don't. Not yet at any rate. And there's no good evidence that spending X millions will make them work, and even less evidence that after all that time and expense you'll have a technology that will make operations any cheaper, never mind procurement costs.
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And so the endless circle of life comes to an end, meaningless and grim. Why did they live, and why did they die? No reason. Two hundred million years of evolution snuffed out, for in the end Nature is horrific and teaches us nothing