Author Topic: The Reaction Engines Skylon Master Thread (3)  (Read 322203 times)

Online Chris Bergin

Third thread for Reaction Engines/Skylon.

Last thread got to 215,000 views, so there's a good amount of interest in this.
http://forum.nasaspaceflight.com/index.php?topic=30547.0

However, that's not an excuse to grandstand ("look at me!!"), as you normally see in large threads, when the resident "King of the Internet" starts to impose his world view on everyone.

This has to be on topic and civil.
« Last Edit: 12/31/2013 12:47 PM by Chris Bergin »

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #1 on: 12/31/2013 03:50 PM »
Thanks Chris :)

An actual "debate" discussion would be a good thin I think, and trust me I fully understand how "people" like Avron can get under everyones skin, but as Chris says lets try and stay on-topic and be civil :)

I first feel I need to correct some mistaken information:

In message: http://forum.nasaspaceflight.com/index.php?topic=30547.msg1138455#msg1138455

ChirsWilson68 wrote:
Quote from: RanulfC on 12/24/2013 03:41 PM
"Despite everything that REL has managed to do I don't see anyone in US aerospace taking the results seriously yet. I'd almost classify it as a "mental-block" but I can't tell if it is institutional, educational, or cultural..."

You left off another possibility -- the possibility that US aerospace is right not to take it seriously."

Sorry Chris but I think this and the subseqent "discussion" with JohnSmith19 is taken out of context and miss-understanding.

The US aerospace industry is not "right" in not taking RELs work seriously, and I was pointing out that this IS a serious "blinder" because of standing assumptions that are in fact not at all supported by evidence and now totally disproven by work REL has done.

Let me repeat the entire quote:
I wrote in message: http://forum.nasaspaceflight.com/index.php?topic=30547.msg1138160#msg1138160
"Seriously, the US wasn't interested in the HOTOL air-breathing tech. They had/were still getting over the NASP disaster and SCramjets were JUST becoming mentionable again but most work was back to either Turbine based or Rocket based "Combined Cycle" engines and really there was and seems to be still is a very deeply imbedded "assumption" in US engineering that ANY "air-breathing-rocket" HAS to be tied to a LACE system. Despite everything that REL has managed to do I don't see anyone in US aerospace taking the results seriously yet. I'd almost classify it as a "mental-block" but I can't tell if it is institutional, educational, or cultural..."

Note the bolded part? This refers to a still earlier message I'll also quote again:
http://forum.nasaspaceflight.com/index.php?topic=30547.msg1133775#msg1133775
I wrote:
"Re-reading "Facing the Heat Barrier" (page 110+ "Combined Cycle Propulsion Systems") notes that it was quite clear that there was a serious "miss-match" between turbocompressor pressures and those for a rocket engine. (cited example is an SR-71 turbocompressor pressure peaked at around 20psi at Mach-3 and 80,000ft yet rocket injection pressure was measured in the hundreds of psi to thousands for "high-performance-engines") The disconnect seems to have been at the time no one considered "deep-cooling" followed by compression and then injection only LACE. Similarly with the SCramjet, once it was known that supersonic combustion was possible it SEEMED to be just a short step to application, but it wasn't. They wanted to use LH2 and "air" for a rocket engine based combined cycle (various types of Ejector-Ramjet Engines) and it seemed the only way to get "air" compressed to the proper injection pressure was to liquify it and then use a rocket turbopump to inject it. And that seems to be a major "hang-up" for the LH2
series SERJ engines too as they probably incorperated a LACE cycle to feed the ejector rocket where as the lower-speed/lower weight H2O2/Kerosene SERJ did not.

SABRE deep-cools the air to a point where the compressor can build up enough pressure to inject into a rocket engine, albeit at a lower pressure than the "experts" would probably consider optimal but as we all are well aware "optimization" can and often is "overrated" when just trying to get the job done."

REL has proven that the bolded part works, you can run a functional and effective rocket engine on DEEP-COOLED and turbocompressed air and hydrogen which invalidates the "argument" based on the assumptions given. The US aerospace industry pretty much "solved" the heat-exchanger frosting issue in the mid-1960s, but because of the "focus" on requireing LACE (and in some cases Hypersonic-LACE) for the needed LIQUID oxygen to supply the "high-pressure" rocket engine the system required far to much Liquid Hydrogen for a viable flight system specifically due to the huge amount of "waste" hydrogen the system generated during operation. There were other factors as well but REL has now proven that LACE is NOT required and in fact never was, this is a significant development which no one in the US aerospace industry seems interested in.

Why is this important? Well first of all a major issue of contention with the idea of air-breathing "assist" of any kind to orbit has been the complexity and expense of air-breathing at high Mach speeds. LACE, though it is clearly more efficent ON PAPER adds complexity and cost due to the requirements of the systems, especially at higher Mach speeds. Much like the often "trumpted" but mostly theoretical ability of the SCramjet to "lower" space access costs these two sytems often combined in some way are literally "textbook" designs for an air-breathing space booster system or SSTO. But neither system is needed in reality and no one "bothers" to correct the textbooks, the assumptions, or the "archived" wisdom of earlier "experts". The MISTAKEN INFORMATION continues to be prepetuated throughout the system, and for this the system suffers.

Let me address another quote:
http://forum.nasaspaceflight.com/index.php?topic=30547.msg1139093#msg1139093
ChrisWilson68 wrote:
"RanulfC said the US aerospace industry doesn't take REL seriously. He listed three possible reasons. All his reasons assumed that REL was correct and the US aerospace industry was just being dumb not to see it. I suggested there's a fourth possibility: that the US aerospace industry is right not to be interested in REL's work."

First and foremost lets not put words in my mouth, I NEVER suggested teh US aerospace industry was being "dumb" I simply suggested that they have/had a "blindspot" when it comes to information they do not "see" as relevent even when it is. Point of fact really is that REL IS correct and assumptions carried forward by US and other "industry" experts has been wrong for decades. And no this is NOT "just" the US, but Europe, Russia, and India to name a few others that have been working with the wrong assumptions.

The question is not "should the US aerospace industry (or anyone else for that matter) be interested in RELs work" but rather "SHOULD they be interested in the RESULTS of that work whether they "Plan" on following up that particular path or not?" A major "assumption" that has been the basis of decades of work, millions of man-hours, and billions of dollars woth of effort has been PROVEN to be false, yet the only ones who have seemed to have taken any note is the company that did the work that proved the assumption false. Yes very much people in the industry SHOULD be interested in the results if nothing else and they should be re-examining the "assumptions" based on and around the now shown to be false assumption upon which all that previous effort was based.

Currently should REL fold tomorrow and disappear into the dust bin of history, the "false-assumption" will continue to live on as a "paper-virus" as anyone in the future looking into the subject run into that same brick wall because noone took enough interest to challenge and/or change it to reflect the truth. This has been shown over and over again, work gets repeated, results are classified as they pertain to THAT specific project and no one looks at the big picture to see if the results are applicable to a wider area. People in the industry probably "rightly" will look at what REL is doing and say "well it doesn't apply to what WE do" because it is a very specific and narrow application. On the other hand it DOES simply and forthrightly point out a VERY basic error in thinking that has led to a lot of time, money and resources being spent only to run into a dead-end that could have been avoided and SHOULD be re-examined and the new data incorporated. If only to prevent future repeats of hitting the same dead-end.

Frankly, I doubt its going to happen because the US aerospace industry considers "air-breathing" in any context of orbital launch/assist or operations for the most part to be a "dead-end" and the small segment that DOES have any interest is fixated on the SCramjet. The majority of "Launch Vehicle" people are fixated on rockets and those that are "air-breathers" are pretty much fixated on aircraft applications, so in the end neither the "rocket" folks nor the "air-breathers" will take note of what REL has done because it doesn't "apply" to them directly. True, but it DOES effect something and it is something that is a very basic and in some ways fundamental "assumption" that DID and probably will again effect SOMEONE. My major "issue" here is that even if REL is wrong and Skylon never works they have already undermined and demolished a basic yet very large "assumption" that has been in place for a very long time. If no one takes "notice" of that nor does anything about correcting the error then how many other "errors" have krept into the system that remain unquestioned and unchallenged? And how much are we missing because this is the case?

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline charliem

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #2 on: 01/01/2014 03:39 AM »
I don't think the high level of skepticism is specially directed against Skylon, more like against every SSTO proposal.

Easy to understand given the, by now, large number of initiatives in that direction that have been advanced, to die on the drawing boards when their numbers did not add up.

Understandable, but that demonstrates nothing.

I like Elon Musk's way of confronting hard engineering problems: "reason from first principles, not by analogy" (although it seems that maintaining such an open mind is hard since Musk himself has publicly declared that he does not give Skylon many probabilities for success ... and I'd be surprised to know he took the time to study it at any length, given his 100+ hour work weeks).

So, reasoning from first principles: What is needed to build an SSTO that we have not?

If I'm not mistaken just the engine. That's the last piece of the puzzle ... a big piece alright, but just one.

Does anyone doubt that if we had an engine that could operate in a vacuum, with Isp, weight, and T/W in the same order of magnitude of a jet engine, any competent rocket builder could design an SSTO based on it?

So, in my opinion the only objections worth addressing right now are those regarding the Sabre engine:

- Any show stopper with the precooler?

- How hard is to design a combustion chamber that can burn both LOX and/or compressed air with LH2?

- Will it be possible to make it work efficiently at such different pressure regimes?

- Supposed that the precooler works as intended, any problems compressing the air?

- Possible troubles with the intakes (from mach 0 to mach 5.5, that's something)?

- What about switching regimes. Could that also be a cause for concern?

- Etc.

In the previous thread some people expressed doubts, even declared right away impossible, that the Sabre engine can work as advertised, but without giving arguments, or giving pseudo arguments that only reflect ignorance of the principles on which this engine is supposed to work.

Let's be a bit more serious, please.

Offline Hanelyp

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #3 on: 01/01/2014 05:25 AM »
- Any show stopper with the precooler?
I hear the heat exchanger has been demonstrated.
Quote
- How hard is to design a combustion chamber that can burn both LOX and/or compressed air with LH2?
I suspect the greatest difficulty would be the shift in hydrogen:oxidizer ratio.  In either mode the hydrogen would be injected as a gas.  A tri-propellant setup with separate injectors for air and LOX may be favored.
Quote
- Will it be possible to make it work efficiently at such different pressure regimes?
Which assumes rocket mode will operate at a greatly different pressure than air breathing mode.  At constant pressure I expect the switch to LOX to be accompanied by a large increase in thrust.
Quote
- Supposed that the precooler works as intended, any problems compressing the air?
- Possible troubles with the intakes (from mach 0 to mach 5.5, that's something)?
A variable geometry ram intake seems likely.  The SR-71 flies with such intakes over a narrower speed range.
Quote
- What about switching regimes. Could that also be a cause for concern?
I doubt the switchover would be abrupt, but start with supplemental LOX injection as air intake drops off.  With air, LOX, and hydrogen pumps driven by independent turbines, a smooth shift in mix ratio should be workable.

The big question I have is not whether the engine can be built, but if it will deliver the performance needed for Skylon SSTO.

Offline Tass

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #4 on: 01/01/2014 01:43 PM »
Quote from: Dror
Quote from: Tass
Quote from: Avron
Like I said it will need to defy the laws of nature - name one rocket engine that launches anything to orbit running on compressed air and any fuel you wish to select ..

Why is this in the same sentence? Doing something new is not the same as breaking the laws of nature.

Anyway, to answer your question: There is none. Why the bleep would you use compressed air as propellant in a rocket? You'd get terrible isp if you had to carry all that nitrogen with you. However making a rocket stage that can reach orbit on regular fuel when starting from 30000m and mach 5 is almost trivial (insofar as anything could ever be called that in this business). Almost any stage you'd care to mention could do it.

I agree with the first sentence of your answer.
Notice that all the rest of your answer is based on your misunderstanding of Avrons question -
" compressed air and any fuel you wish to select "

I'd like to hear what you think that I misunderstood here. Avron said that you cannot get to orbit with a rocket using compressed air as an oxidizer, which is true, but a complete non sequitur as it relates to Skylon.

If you carry four times your oxidizers weight in nitrogen, the Isp gets terrible.

Did you think I thought he meant flying simply on compressed air as cold gas thruster? That would obviously be much worse still.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #5 on: 01/01/2014 03:01 PM »
I don't think the high level of skepticism is specially directed against Skylon, more like against every SSTO proposal.
There are 2 reasons why there is skepticism for  for SSTO.
1)It's impossible to be build structures and engines to do it.
2)If you do you end up with a payload of 1/3 -1/4 that of an ELV.

The first has been known to be false since the 1960's. Boeing did a phenomenal job on the mass fraction of the Saturn V 1st stage, given it had the whole rest of the stack sitting on top of it and no common bulkhead tanks.

2) is the real killer. Historically people who've favored VTOL SSTO have implicitly accepted either more launches and some kind of orbital assembly or a much bigger vehicle to carry the same payload.

By going HTOL SABRE/Skylon side steps 1 (aircraft thrust is typically about 1/3 GTOW and the mass fraction can be much larger) and delivers an ELV class payload mass (4.5% of GTOW IIRC) in an ELV sized (but reuseable) vehicle..
Quote
Easy to understand given the, by now, large number of initiatives in that direction that have been advanced, to die on the drawing boards when their numbers did not add up.

Understandable, but that demonstrates nothing.
I'd look in the back of these threads. This has been discussed at length. TL:DR There have been about two serious efforts at VTOL SSTO where both the customer and the developers really wanted to do it. One ran out of money, the other failed when transferred to a different organization.
Quote
I like Elon Musk's way of confronting hard engineering problems: "reason from first principles, not by analogy" (although it seems that maintaining such an open mind is hard since Musk himself has publicly declared that he does not give Skylon many probabilities for success ... and I'd be surprised to know he took the time to study it at any length, given his 100+ hour work weeks).
If only more aerospace engineering was done that way.  :) But I think  Musk admitted later this view was cursory, mostly due to the fact no one has ever done a winged SSTO. 

At the end of the day a Skylon will not land on Mars (although there is an REL study on how Skylon's could enable a Mars expedition and the have worked the ISRU problem, using Cynogen as quite a peppy fuel) and that remains Musk's goal. He's already working on a system to get to LEO which I think will remain his focus.
Quote
So, reasoning from first principles: What is needed to build an SSTO that we have not?

If I'm not mistaken just the engine. That's the last piece of the puzzle ... a big piece alright, but just one.

Does anyone doubt that if we had an engine that could operate in a vacuum, with Isp, weight, and T/W in the same order of magnitude of a jet engine, any competent rocket builder could design an SSTO based on it?
Yes they'd have big doubts if you're going VTOL. Bad rocket engines deliver T.W of 40:1, Merlin 1D about 160:1 and good jet engines give about 10:1. SABRE delivers around 14:1 but it's real benefit is that you don't take a huge Oxygen tank with you. REL reckon that would be about 250mt of LO2.

OTOH if you go with HTOL and wings things change quite a lot. Hence REL's preferred approach.

The TPS and structures are another issue but a good engine really opens up the options.
Quote
So, in my opinion the only objections worth addressing right now are those regarding the Sabre engine:

- Any show stopper with the precooler?
Tested in 2011/12 using a  full size module (IE 1/9 of the final design), along with a mfg line to make more of them.
Quote
- How hard is to design a combustion chamber that can burn both LOX and/or compressed air with LH2?
Good question. Note that like the SSME SABRE uses a "pre burner" to partly burn the air and add the LH2. This 2 stage process should make shifting the MR quite a bit easier. REL have also studied low NoX combustion for their M5 Cruise aircraft design LAPCAT.
Quote
- Will it be possible to make it work efficiently at such different pressure regimes?
The SSME ran from sea level to orbit with a fixed nozzle. However REL seem pretty keen on going with a high expansion altitude compensating nozzle that will give better performance, and of course it's in HTOL mode. That will be flight tested by a vehicle called "Valkarie" Note there is not altitude where the air pressure just drops to near zero. It's quite gradual, depending on climb angle.
Quote
- Supposed that the precooler works as intended, any problems compressing the air?
REL's goal has been to use the precooler and flight trajectory to give the compressor blades an airstream that does not seem to change from take off airspeed IE M0.5. The pre cooler ensures the air properties remain more or less constant, allowing a simpler turbine design. In principle that also enables lighter materials as they don't need to retain their strength at high temperatures. Historically "hot strength" has risen with density so higher inlet temperature --> heavier fan blades. With the precooler the blades could be Titanium (or possibly) carbon fibre. Without it's a super alloy.
Quote
- Possible troubles with the intakes (from mach 0 to mach 5.5, that's something)?
REL have been partnering with a company that operates a "gun tunnel" to test inlet behavior. The design is not wholly CFD based. IIRC this has been tested to M12, but the inlet should be fully closed by M5.5
Some fixed geometry ramjet designs have run with a fixed geometry up to M6. SABRE's will be variable.
Quote
- What about switching regimes. Could that also be a cause for concern?
Of course. That's likely to be a big part of the test programme for the full size ground test engine that's being designed (along with its test stand) now. Likewise the 1st (X-plane) prototype.

Note that SABRE operates with a "pre burner." That means that the amount of heat energy in the burnt propellant, and the drive power to the drive turbines of the pumps can be varied independently of the heat extracted from the airstream.

I think it's also likely that by now REL have a detailed model of SABRE which they've been using to work out (simulated) ignition, transition, cruise and shut down sequences on. They will also be aware of the issues of the SSME regarding the precision needed in data collection.
Quote
In the previous thread some people expressed doubts, even declared right away impossible, that the Sabre engine can work as advertised, but without giving arguments, or giving pseudo arguments that only reflect ignorance of the principles on which this engine is supposed to work.

Let's be a bit more serious, please.
Happily.  :)
« Last Edit: 01/01/2014 03:21 PM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline DMeader

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #6 on: 01/01/2014 03:44 PM »
Must you all do these massive quote-a-thons?

Offline Tass

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #7 on: 01/01/2014 04:40 PM »
Must you all do these massive quote-a-thons?

How else would you answer a lot of questions while keeping it clear what you are responding to?

Offline charliem

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #8 on: 01/02/2014 01:23 AM »
I think DMeader has a point. Many of the posts in the previous thread were clearly too long. I'll try to restrain myself.

To clarify my position. I've been following Sabre and Skylon for some years. I think I've studied all the documents REL has released about them until now, and I'm a big supporter of their efforts (even contributed with a few bits to the Skylon article in Wikipedia). I'm reasonably optimistic, but what I'm NOT is 100% sure that Sabre/Skylon is guarantied to work (from an engineering point of view, let's forget about politics and economics for now).

Does anyone doubt that if we had an engine that could operate in a vacuum, with Isp, weight, and T/W in the same order of magnitude of a jet engine, any competent rocket builder could design an SSTO based on it?
Yes they'd have big doubts if you're going VTOL. ..... OTOH if you go with HTOL and wings things change quite a lot. Hence REL's preferred approach.

John you are being picky :), and you wont have to convince me, as I've already said I'm reasonably optimistic about Sabre/Skylon, but maybe you are not being totally fair with "them" (AKA old space).

Anyone can apply the rocket equation to any modern transcontinental airliner, and see how they are capable of giving more than enough delta-V to reach LEO, or even Mars ... pity they can't operate in a vacuum  ;)

On the other hand I'm convinced that any problem with avionics, structure, TPS, operations, etc, can be solved without having to resort to R&D any new technology.

And about the extended skepticism, from my point of view it's just that no one has ever built one, and the aerospace sector have been in such a roller-coaster of hope and disappointment, and for so long, that now nothing short of seeing one fly is going to convince most of them.

So, are we in agreement? The engine is THE piece we don't have yet. Right?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #9 on: 01/02/2014 08:27 AM »
I think DMeader has a point. Many of the posts in the previous thread were clearly too long. I'll try to restrain myself.
Likewise
Quote
On the other hand I'm convinced that any problem with avionics, structure, TPS, operations, etc, can be solved without having to resort to R&D any new technology.

And about the extended skepticism, from my point of view it's just that no one has ever built one, and the aerospace sector have been in such a roller-coaster of hope and disappointment, and for so long, that now nothing short of seeing one fly is going to convince most of them.
No. The engine is a necessary part of the puzzle, but not sufficient. If it was Skylon could be designed with much better known (but heavier) materials, rather than needing a SiC reinforced glass skin over a carbon fibre truss structure. SABRE helps a lot but it's not the whole answer.

Solving the SSTO problem needs people to consider the whole architecture, and what it's made out of.

NB I'm sure REL have studied the STS and its lessons. I said heavier because while the STS TPS is an existence proof that long slow descent TPS is possible it was a maintenance nightmare, and a major contributor to costs, hence not viable for companies that want to make an actual profit.

Note the corner case. SABRE underperforms and the skin and structure are overweight. Ifthat happens then the chances are that Skylon will not meet it's payload target to orbit. That would trigger either a SABRE re-design or a Skylon re-design with backup material selections  :( While I believe SABRE has a lot of margin that does not mean infinite margin.  :( I do not believe that SABRE will substantially underperform or that the Skylon design will be substantially over its target weight, but that's my opinion.

There is substantial risk outside the engine.  :( I think it's recognized and can be managed, but only time will tell.
« Last Edit: 01/02/2014 08:28 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline grondilu

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #10 on: 01/02/2014 10:30 AM »
The engine is a necessary part of the puzzle, but not sufficient. If it was Skylon could be designed with much better known (but heavier) materials, rather than needing a SiC reinforced glass skin over a carbon fibre truss structure. SABRE helps a lot but it's not the whole answer.

As a Skylon fan I must admit that this is a fair point.  It's true that the design of Skylon is unconventional not just because of the engine.  The material they want to use for the skin will have to prove itself.

But you know what this makes me think of?  Well, this is going to come out of nowhere, but this makes me think of Starlite.  I almost hate Maurice Ward for dying without revealing his secret.  What a stupid waste.
« Last Edit: 01/02/2014 10:32 AM by grondilu »
Space is pretty much literally an astronomically-high hanging fruit.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #11 on: 01/02/2014 03:18 PM »
But you know what this makes me think of?  Well, this is going to come out of nowhere, but this makes me think of Starlite.  I almost hate Maurice Ward for dying without revealing his secret.  What a stupid waste.
Only if you've never read James Follets techno thriller "Sabre."   :) In it Skylon is recast as an Anglo French commercial consortium to build a passenger carrying ballistic/orbital transport (anywhere to anywhere in <45 mins). "Starlite" enables the Skylon of the book to be made out of Aluminium alloys, like Concorde.

Sadly the only documentary on Ward and Starlite I'm aware of was a rather whimsical affair which drew parallels with the film satire "The Man in the White Suit," including a narration by Sir Alec Guinness (the star of the film) and appropriate sound effects.

Ward's death was a blow. Ward did IRL what Robert Downey's Tony Stark only does in fiction. A breakthrough engineering material created in a garden shed and on a kitchen table. And it seems we can't duplicate it either.  :( I don't think anyone is even sure if it was the structure of the material or its chemical composition that gave the results.  :(

I think the only hope of its rediscovery is that enough people become aware of its capabilities to inspire them to re-create it because they have an existence proof that those capabilities are possible and were independently verified.  :(

But sadly Starlite is unavailable, so it looks like they will be going with PyroSiC. It may not have the performance, but at least it has a more TPS sounding name.   :)
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline charliem

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #12 on: 01/03/2014 02:18 AM »
The engine is a necessary part of the puzzle, but not sufficient. If it was Skylon could be designed with much better known (but heavier) materials, rather than needing a SiC reinforced glass skin over a carbon fibre truss structure. SABRE helps a lot but it's not the whole answer.

Right, the Sabre engine is not the only new tech in Skylon, but I doubt the level of difficulty in making work engine and TPS are comparable, and more important, the consequences of a failure in development might be quite different.

With most other subsystems in Skylon there are alternatives to the present design, but to the engine? I don't think so.

Once/if this engine reaches TRL 9, it wouldn't be surprising if some other company/ies came out with alternative designs for a spaceplane based on it. Kind of like with turbofans and airliners.

On the other hand, if the Sabre engine R&D ends in failure it's getting back to square one for RLV-SSTOs ... again.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #13 on: 01/03/2014 03:15 AM »
Right, the Sabre engine is not the only new tech in Skylon, but I doubt the level of difficulty in making work engine and TPS are comparable, and more important, the consequences of a failure in development might be quite different.
Ceramic and carbon fiber reinforced turbine blades have been coming "real soon now" in gas turbines for decades. AFAIK I know they have not even made it to missile use.
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With most other subsystems in Skylon there are alternatives to the present design, but to the engine? I don't think so.
Or the skin. If there were materials with a better experience base backing them, REL would use them. 
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Once/if this engine reaches TRL 9, it wouldn't be surprising if some other company/ies came out with alternative designs for a spaceplane based on it. Kind of like with turbofans and airliners.
There is a design study from IIRC the University of Strathclyde. One of the SABRE design goals was not to need the sort of very close engine/vehicle integration that SCRamjets seem to need and which has proved very sensitive to the details of the structure (and hence to changes in that structure).
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On the other hand, if the Sabre engine R&D ends in failure it's getting back to square one for RLV-SSTOs ... again.
True.  :(
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Offline charliem

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #14 on: 01/04/2014 01:38 PM »
With most other subsystems in Skylon there are alternatives to the present design, but to the engine? I don't think so.
Or the skin. If there were materials with a better experience base backing them, REL would use them. 

Well, remember that the skin material for the present version of Skylon (System2 SiC fiber reinforced glass ceramic) was their second choose, at first they contemplated C/SiC FRGC because of its better properties (higher temperature limit, lower density). I think the switch was due to cost and easy of manufacturing considerations.

If there are two suitable materials, maybe there is a third (?)

And then there are other possibilities. What about an ablative TPS?

Sure that it would increase operational costs and imply the necessity for refurbishment. In fact I'm not at all in favor of a solution like that, I'm just playing devil's advocate to show that TPS tech is not necessarily a show stopper.

By the way, given the low heat loads the skin is expected to have to endure I wonder how thick and how heavy a NASA's PICA skin for Skylon should be if we set the requirement of needing refurbishment only once every, say, ten flights?

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #15 on: 01/04/2014 02:01 PM »
Drinking my morning “cup of Joe” I had an amusing thought. Wouldn’t it funny if the U.S. lack of interest in the engine technology be due that they already had one operating in one of their “black” programs... Just sayin’, how would we know..?
"The laws of physics are unforgiving"
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Offline 93143

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #16 on: 01/04/2014 05:01 PM »
What about an ablative TPS?

As I recall, X-15 tested ablative TPS and found that it ruins the aerodynamics once it starts actually ablating.

In addition, using enough TPS to last 200 flights would probably be contraindicated by mass considerations, and it would be a huge pain to apply ablative TPS over the entire skin (yes, you'd still need a skin) of something like Skylon, especially since you'd likely have to remove the charred mess that used to be the old TPS before starting...

I also wonder how an ablative TPS that large would deal with aero loading and thermal expansion issues.

Offline Avron

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #17 on: 01/04/2014 07:08 PM »
Thanks Chris :)

An actual "debate" discussion would be a good thin I think, and trust me I fully understand how "people" like Avron can get under everyones skin, but as Chris says lets try and stay on-topic and be civil :)


Hi Randy.

What part go under your skin.. the lack of Oxygen in an Rocket engine ?  or lack of an "Air" breathing engine example, i.e.you cannot burn Nitrogen, well not yet.

One more showstopper.. the highest levels of Ozone are found in the stratosphere(15-50km ) for the vision to work it would need to burn Ozone, as the levels of O2 at that level are lower. That will go down well with the EPA or like gov. group in your part of the planet.


Avron

 

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #18 on: 01/04/2014 07:48 PM »
Well, remember that the skin material for the present version of Skylon (System2 SiC fiber reinforced glass ceramic) was their second choose, at first they contemplated C/SiC FRGC because of its better properties (higher temperature limit, lower density). I think the switch was due to cost and easy of manufacturing considerations.

If there are two suitable materials, maybe there is a third (?)
AFAIK the current material is called PyroSiC. However it's original properties were below that of System 2 and they have been working with the supplier to bring its properties up.
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And then there are other possibilities. What about an ablative TPS?

Sure that it would increase operational costs and imply the necessity for refurbishment. In fact I'm not at all in favor of a solution like that, I'm just playing devil's advocate to show that TPS tech is not necessarily a show stopper.

By the way, given the low heat loads the skin is expected to have to endure I wonder how thick and how heavy a NASA's PICA skin for Skylon should be if we set the requirement of needing refurbishment only once every, say, ten flights?
Ablatives work best with short intense heat loads. The flight of an X15 with an ablative coating (which IIRC took weeks to apply) was not very successful. It was also a fall back option for STS.

TPS and structure are key components of the architecture and failure to survive (or survive for the necessary length of time) will be major setbacks.

Please note that all this comes under the Skylon part of SABRE/Skylon and I suspect REL don't want to be seen to be treading on the toes of the airframe partner.  :) . that said I noted that one of the presentations that has been given by either Hempsell or Bond was very detailed in the weight allowances for skin panels, rivets etc.

This suggests some structural test work has been done to get those numbers.  What cannot be tested is how well such structure stands up to a 200 flight test programme, and how difficult field replacement of those panels will be. Will it be a case of a couple of panels a flight? a few ever every few flights? Half of them every flight? No one knows.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

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Re: The Reaction Engines Skylon Master Thread (3)
« Reply #19 on: 01/04/2014 08:04 PM »
Ozone makes a powerful rocket propellant... But makes fluorine look benign.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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