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General Discussion => Advanced Concepts => Topic started by: Chris Bergin on 02/18/2015 11:15 AM

Title: The Reaction Engines Skylon Master Thread (5)
Post by: Chris Bergin on 02/18/2015 11:15 AM
Fifth thread for Reaction Engines/Skylon.

Previous: The Reaction Engines Skylon Master Thread (4)
http://forum.nasaspaceflight.com/index.php?topic=34964.0

This has to be on topic and civil. This is for sensible debate and updates. Anything trivial or stupid will be deleted without notice.
Title: Yield (on bonds, investments, and so on)
Post by: jrc14 on 02/18/2015 02:47 PM
Just to clarify a point on 'yield' that seems to be causing misunderstanding, and responding to recent posts (in thread #4) by t43562, francesco nicoli and others ...

Why I think I know the answer: I have been working in investment banks building quant models (including models of bonds and other investments) for the past 25 years
Why it's important: thanks, in part, to imprecise wording in the investopedia article on 'Yield', forum readers might misunderstand how 'yield' is calculated - and so they'll get a wildly misleading view of how the Skylon business case works (or does not work)
What the answer is: when people quote 'bond yield' or 'return on investment' or 'interest' as a percentage figure, that is always an annual figure (its units being "quantity per cent per year").
The answer in tedious detail:
Suppose that somebody issues, and that I buy, a ten year bond paying a yield of 8%, and that I buy $100 of this bond.  The financial outcome is:
I pay today $100
I receive 1 year from now $8 (interest, also known as coupon)
I receive 2 years from now $8 (interest, also known as coupon)
...
I receive 10 years from now $108 (being repayment of my initial $100 plus $8, being the final interest payment)

So overall, I have paid out $100 and I have received $180.  Deciding whether this was a fair deal (for me or for the bond issuer) is a complex question, and for those wanting an answer the Wikipedia article on Discounting  (http://en.wikipedia.org/wiki/Discounting) is as good a place to start as any.
Bank account interest, loans, mortgages and so forth all follow this general pattern.  The interest rate is an annual amount, describing how much interest is paid each year.

[Note: to the pedants out there: yes, I am aware of semi-annual interest, compounding, daycount convention, the definition of IRR, the difference between nominal/coupon yield, current/OTR yield and redemption yield, the roles of exchanges, depositories and clearing houses, ... . I have simplified the explanation, for the sake of exposition.  If you know enough to challenge me on any of these details, you also know enough to agree with my central point, which is that yield is an annual amount]

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Impaler on 02/18/2015 05:28 PM
jrc14:  Thank you for for that well written post.  I hope this settle the matter for anyone still in doubt and we may now discuss how Skylon business case closes/dose-not-close using correct financial principles.

jrc14, can you give us some rough estimates of what a potential Skylon operators cost of capitol might be and thus generate some estimates of what kind of gross profit is needed over a range of time-frames to breakeven.

Lets assume 1 Billion is the initial outlay for the Skylon, and time periods are 2 year, 5, years, 10 years, 20 years.  How much do they need to make over and above operating costs per year and over the period in question to justify the investment?
Title: Re: Yield (on bonds, investments, and so on)
Post by: t43562 on 02/18/2015 05:42 PM
Just to clarify a point on 'yield' that seems to be causing misunderstanding, and responding to recent posts (in thread #4) by t43562, francesco nicoli and others ...
What the answer is: when people quote 'bond yield' or 'return on investment' or 'interest' as a percentage figure, that is always an annual figure (its units being "quantity per cent per year").

Thanks for the explanation.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/18/2015 06:06 PM
To start off the new thread, here's a summary of my own reasons for being skeptical about Skylon.  Some of these views are probably shared by other skeptics.  Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.

First off, I don't think there's a known flaw in Skylon that definitely makes it impossible.  It's not like a perpetual motion machine that violates known laws of physics.  My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case.  There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.

The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

The team at REL has consistently proposed building a large-scale single-stage-to-orbit system.  That shows poor judgement, in my opinion.  SpaceX started with Falcon 1.  Then then moved to a full-expendable Falcon 9.  Now they are working on perfecting reuse of only the first stage.  Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch.  I believe that kind of incremental, flexible approach is very effective.  It is the opposite of the REL approach.  With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans.  And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.

There have been many programs with similar or lesser optimistic goals that have failed.  The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed.  Note that I'm not saying the details of the technological challenge are similar -- they are not.  But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.

The X-33/VentureStar is another launch program that had optimistic goals and failed.  I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today.  And yet it failed because of the engineering details in turning the theory into reality.

I also find the projected business model of Skylon implausible.  It posits 30 units of Skylon will be bought for a billion dollars each.  That would give a launch capability far, far beyond the current market, at a price not enough lower to justify the enormous market expansion.  One commonly-used cost figure is $5 million per flight based on 200 flights per vehicle and 30 vehicles.  If the market were really there for such a launch rate, SpaceX could develop a fully-reusable upper stage for Falcon 9 and cover it at an even lower cost.

Another part of the business case is that governments will by Skylon units for prestige.  I think that's unrealistic because national space programs get prestige from developing indigenous capabilities far more than by buying from another country.

So, there you have it.  If you disagree, post what you disagree with and why.  If you're a reader and undecided, read this and the responses and make up your own mind.

One final note: I hope I'm wrong and that Skylon beats the odds and succeeds.  But hope shouldn't mean we aren't realistic about how unlikely something is.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/18/2015 07:13 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

The team at REL has consistently proposed building a large-scale single-stage-to-orbit system.  That shows poor judgement, in my opinion.  SpaceX started with Falcon 1.  Then then moved to a full-expendable Falcon 9.  Now they are working on perfecting reuse of only the first stage.  Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch.  I believe that kind of incremental, flexible approach is very effective.  It is the opposite of the REL approach.  With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans.  And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.

If my memory serves me their contention is that a smaller system does not offer the economic benefits. In other words the nature of the problem dictates the way they have to go - they can't scale up over time.  Assuming this is true, what do you expect them to do?

I think it's also fair to say that if they can build a demonstrator engine they'll be able to remake their decisions having learned from it. I don't see them claiming that their plan is set in stone. If you consider HOTOL, they have already learned and changed quite a lot.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 02/18/2015 08:40 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/18/2015 09:25 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization.

That is a different argument - if we are respecting the English language and the use of absolutes.

They are an engine company not an airframe company.   Let the airframe company use its great institutional experience for its part of the work.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/18/2015 09:28 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization.

That is a different argument - if we are respecting the English language and the use of absolutes.

They are an engine company not an airframe company.   Let the airframe company use its great institutional experience for its part of the work.

That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/18/2015 09:49 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization.

That is a different argument - if we are respecting the English language and the use of absolutes.

They are an engine company not an airframe company.   Let the airframe company use its great institutional experience for its part of the work.

That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.

Don't they have to? Is it not necessary at all times to make such projections and keep updating them as new information is learned? Would anyone even bother to invest if the projections of today were bad? It doesn't mean their projections are 'plucked out of the air' or based on nothing.  So they will build their test engine and perhaps other things on the way and then their projections will have much more authority whatever they turn out to be but for now we have what we have and can only discuss that.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/18/2015 11:30 PM
That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.

Don't they have to? Is it not necessary at all times to make such projections and keep updating them as new information is learned?

There'd be no shame in their saying "we don't know yet".

Would anyone even bother to invest if the projections of today were bad?

Lots of people make lots of bad investments.  The mere fact that someone has invested in not sufficient to overrule our judgement if we have reason to doubt a projection.

The projections of the early Space Shuttle studies were way off.  The projections of the X-33/VentureStar project were way off.  And in both of those cases you had organizations with much more relevant experience.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 02/18/2015 11:50 PM
To start off the new thread, here's a summary of my own reasons for being skeptical about Skylon.  Some of these views are probably shared by other skeptics.  Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.

First off, I don't think there's a known flaw in Skylon that definitely makes it impossible.  It's not like a perpetual motion machine that violates known laws of physics.  My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case.  There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.

The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't think you are fully aware of the background the REL team. Mark Hempsell for example worked on the DCX.
http://forum.nasaspaceflight.com/index.php?topic=19127.msg493088#msg493088


The team at REL has consistently proposed building a large-scale single-stage-to-orbit system.  That shows poor judgement, in my opinion.  SpaceX started with Falcon 1.  Then then moved to a full-expendable Falcon 9.  Now they are working on perfecting reuse of only the first stage.  Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch.  I believe that kind of incremental, flexible approach is very effective.  It is the opposite of the REL approach.  With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans.  And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.

SABRE is a SSTO engine, I'm not sure what intermediate stage there can be for engine explicitly designed to take a single stage into orbit. I can't imagine designs cost get significantly smaller by making a smaller version.


There have been many programs with similar or lesser optimistic goals that have failed.  The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed.  Note that I'm not saying the details of the technological challenge are similar -- they are not.  But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.
The technical challenge of airbreathing to Mach 18 is clearly of a vastly higher level than airbreathing to Mach 5.5 and the number of unknowns in geting to Mach 18 in 1984 far greater than achieving Mach 5 thirty years later.


The X-33/VentureStar is another launch program that had optimistic goals and failed.  I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today.  And yet it failed because of the engineering details in turning the theory into reality.

X-33 didn't fail, it was cancelled due to a change in administration, just as many Clinton era space programs were cancelled by the Bush administration. What many people forget is that the X-33 was just a rocket powered x-plane like the X-15, like the X-15 it had a ton of not flown before technology some of which had teething problems, and like the X-55 if it had flown it would have provided invaluable hypersonic flight data.


I also find the projected business model of Skylon implausible.  It posits 30 units of Skylon will be bought for a billion dollars each.  That would give a launch capability far, far beyond the current market, at a price not enough lower to justify the enormous market expansion.  One commonly-used cost figure is $5 million per flight based on 200 flights per vehicle and 30 vehicles.  If the market were really there for such a launch rate, SpaceX could develop a fully-reusable upper stage for Falcon 9 and cover it at an even lower cost.
Your comparing apples to oranges, the current launch capability is already far, far, larger than the current launch market and yet it is sustained by it. Further 30 Skylons are not just going to come into existence upon the commencement of commercial availability, they have to be built. At a rate of 2 a year there wouldn't be 30 Skylon's arround until 2040, 35 years from the current market. Finally the question that needs to be asked isn't how many launches could be made each year but how few could be made while still turning a profit at a competitive price because if a profit can be made nothing else matters.What seems to be the case is that at an incremental launch cost of $5 million a very high launch rate can spread fixed costs so widely that the market launch price can be not much more than that or at a much lower launch rate the market price can be competitive with current launchers.


Another part of the business case is that governments will by Skylon units for prestige.  I think that's unrealistic because national space programs get prestige from developing indigenous capabilities far more than by buying from another country.

The business case for governments is massively more responsive space access and, for currently non-space-faring countries, a greatly increased asssured access to space and sovereign space capability as well the economic development that comes with having such assets akin to governments having national flag airlines, building massive hub airports and ports etc.
 
So, there you have it.  If you disagree, post what you disagree with and why.  If you're a reader and undecided, read this and the responses and make up your own mind.

One final note: I hope I'm wrong and that Skylon beats the odds and succeeds.  But hope shouldn't mean we aren't realistic about how unlikely something is.


Personally I think the greatest threat to Skylon development will be a failure of an airframer to commit to it. I think REL may find that despite developing an engine that works well and engenders a lot of interest in the end there may be a general reticence to throw in with another companies grand scheme and disrupt their own planning among the likely consortium partners. I could see REL being bought by RR as a part of an attempt at forming a successful consortium only to end being used to get some lucrative US hypersonics research money.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/19/2015 12:07 AM
To start off the new thread, here's a summary of my own reasons for being skeptical about Skylon.  Some of these views are probably shared by other skeptics.  Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.

First off, I don't think there's a known flaw in Skylon that definitely makes it impossible.  It's not like a perpetual motion machine that violates known laws of physics.  My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case.  There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.

The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't think you are fully aware of the background the REL team. Mark Hempsell for example worked on the DCX.
http://forum.nasaspaceflight.com/index.php?topic=19127.msg493088#msg493088

Actually, that demonstrates my point quite well.  DC-X never progressed to an operational vehicle.  It was never more than a sub-scale technology demonstrator.  Working on DC-X wouldn't give any experience with the very difficult transition from technology demonstration to a system that is economically successful as an operational system.

And "worked on" isn't the same as being in charge.


The team at REL has consistently proposed building a large-scale single-stage-to-orbit system.  That shows poor judgement, in my opinion.  SpaceX started with Falcon 1.  Then then moved to a full-expendable Falcon 9.  Now they are working on perfecting reuse of only the first stage.  Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch.  I believe that kind of incremental, flexible approach is very effective.  It is the opposite of the REL approach.  With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans.  And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.

SABRE is a SSTO engine, I'm not sure what intermediate stage there can be for engine explicitly designed to take a single stage into orbit. I can't imagine designs cost get significantly smaller by making a smaller version.

REL is the one who chose to design it for an SSTO vehicle.  They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.

And everything gets cheaper when things are smaller.


There have been many programs with similar or lesser optimistic goals that have failed.  The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed.  Note that I'm not saying the details of the technological challenge are similar -- they are not.  But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.
The technical challenge of airbreathing to Mach 18 is clearly of a vastly higher level than airbreathing to Mach 5.5 and the number of unknowns in geting to Mach 18 in 1984 far greater than achieving Mach 5 thirty years later.

Getting to Mach 5.5 isn't the challenge.  They still have to get to Mach 25 to make orbit.  True, in some ways it's easier if they're only air breathing to Mach 5.5.  But in other ways it's harder.  They have to carry much more oxidizer, and their engine has to work well in both air-breathing and rocket mode.  Going from Mach 5.5 to Mach 25 in rocket mode (with some of that rocket mode in the dense part of the atmosphere at Mach 5.5) means they need a very good mass fraction.

Like I said, they don't have exactly the same challenges NASP had, but they have very great challenges, and I think they're at a comparable level of difficulty.  Apparently, others think they are too, which is why others are continuing SCRAMJet research and development.

The X-33/VentureStar is another launch program that had optimistic goals and failed.  I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today.  And yet it failed because of the engineering details in turning the theory into reality.

X-33 didn't fail, it was cancelled due to a change in administration, just as many Clinton era space programs were cancelled by the Bush administration. What many people forget is that the X-33 was just a rocket powered x-plane like the X-15, like the X-15 it had a ton of not flown before technology some of which had teething problems, and like the X-55 if it had flown it would have provided invaluable hypersonic flight data.

Getting into the details of X-33 is off topic, but lets just say that opinions differ about X-33 -- many people believe it was cancelled because the progress up to that point indicated it was not able to meet its projections and wouldn't have been viable.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SleeperService on 02/19/2015 04:54 AM
Are you one of those people that claim it's only 5% of the delta v to orbit?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aga on 02/19/2015 05:36 AM
economic viability of the complete system, including engines and airframe.

that was done by others, not by rel... eg. esa, london economics, etc
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/19/2015 06:13 AM
economic viability of the complete system, including engines and airframe.

that was done by others, not by rel... eg. esa, london economics, etc

It was done by REL.  All the projections come from REL.  A small group from ESA did a short audit of the REL plans to see if there was an obvious show-stopper.  They said there wasn't a showstopper they could see.  They didn't claim to know REL's projections were all correct.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/19/2015 07:34 AM
REL is the one who chose to design it for an SSTO vehicle.  They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.
Which would in fact have doubled the development budget as they would had to look at 2 vehicles and the testing around hypersonic separation. The last attempt at which was IIRC the SR71/M4 drone separation tests.

This is from the man who's worried about "too many unknowns."  :(

You need to stop making assertions as fact. They make you look untrustworthy.
Quote
And everything gets cheaper when things are smaller.
You work in a Silicon valley start up and you aren't aware of price inflation between the last and next generation of wafer fabs as they've gone from about about 33 to 14nm?

Or the time and effort involved when you go from the piping in the 1960's Aerospace Plane (about 1cm) to the 1mm used in REL HX's.

Or REL estimate that a scaled down LH2 turbo pump (to give the same chamber pressure) for a small scale SABRE would eat abut £250m of the budget alone as engineering bearings to run about 12x faster than the full scale unit (in LH2) is much harder.

No smaller often means cheaper, but not always. Smart engineers are aware of this and plan accordingly.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/19/2015 09:25 AM
I don't see them claiming that their plan is set in stone.

Claiming, no. Acting, yes. They are designing payloads and space stations and Mars missions around the size/capacity of the Skylon payload bay. (Not to mention a hypersonic passenger plane.) And Bond rejects out of hand any suggestions that Skylon may not be the optimal design (as John echoes, above). If you were an "airframer", would you get mixed up with an engine company which behaves like that? Or wait until they fail and just licence the engines from whoever buys the IP, and develop your own clean-sheet design?

To me, it's like some who wants to develop the world's first jet engine. So far they have one compressor fan. But they've not only designed the rest of the engine, and designed the entire airliner around that engine, and insisted it's the only possible design, but they are proposing new airport designs based around the door spacing on that proposed airliner for the proposed engine for which they have (after 20 years) only built a single compressor fan.

But you dare suggest they are being a bit premature...

REL is the one who chose to design it for an SSTO vehicle. They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system
Which would in fact have doubled the development budget as they would had to look at 2 vehicles

{sigh} Why is this idea so prevalent in aerospace?

Two is more than one, so therefore it must cost twice as much to develop an aircraft to carry freight between cities and a truck to ferry between individual customers and the airfreight terminals than to develop a single vehicle which can fly between cities but land directly on the customers' driveways. Must. Because two is more than one.

Quote
and the testing around hypersonic separation.

Only if they were stupid.

When Chris is suggesting smaller stepping stones, when that's the entire premise of his argument, why would you assume he would be suggesting the hardest possible version of TSTO?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/19/2015 10:42 AM
I don't see them claiming that their plan is set in stone.

Claiming, no. Acting, yes. They are designing payloads and space stations and Mars missions around the size/capacity of the Skylon payload bay. (Not to mention a hypersonic passenger plane.) And Bond rejects out of hand any suggestions that Skylon may not be the optimal design (as John echoes, above). If you were an "airframer", would you get mixed up with an engine company which behaves like that? Or wait until they fail and just licence the engines from whoever buys the IP, and develop your own clean-sheet design?

If one looks with a hostile attitude one can twist quite normal behaviour into something sinister.

Engines do really determine what kind of aeroplane can be built - it has always been that way around in the aircraft world I believe (I'm no expert but reading the history of flight makes it pretty obvious). So yes, the airframer is going to have to accept that they can't make an airframe any size or any shape they like.  They still have freedom to ignore REL's design if they have to a reason to.  Why would they be sulky about something that has been a fact of life in the aerospace industry since the beginning?

REL designed Mars missions to show themselves that it was possible to do such a thing with the design.  If it hadn't been then that would have meant there was something basically wrong with the whole idea and it would have to be modified.

Similarly they have studied how to launch satellites and boost them into GEO. Without doing this, who would invest? It's part of designing something that you put it through it's imaginary paces before you build it rather than afterwards. Surely? Would you consider it responsible not to? Surely this has to be done repeatedly with more and more detail until the final article does it for real?

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Krevsin on 02/19/2015 11:32 AM
REL is the one who chose to design it for an SSTO vehicle.  They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.
Which would in fact have doubled the development budget as they would had to look at 2 vehicles and the testing around hypersonic separation. The last attempt at which was IIRC the SR71/M4 drone separation tests.
I'm not an expert on any of this so feel free to correct me, but wouldn't it make more sense to develop a TSTO Skylon in such a way that the skylon makes a suborbital hop and, once outside the brunt of the atmosphere, open the cargo bay and deploy an upper stage to which the payload is attached?

In fact, hasn't something similar to this concept been proposed in this (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30547.0;attach=535740) study by Mark Hempsell?

It'd certainly be less complicated than staging inside the atmosphere at hypersonic velocities IMO.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/19/2015 11:51 AM
Claiming, no. Acting, yes. They are designing payloads and space stations and Mars missions around the size/capacity of the Skylon payload bay.
Another new member who's appeared from nowhere. Welcome to the forum.

Actually you have REL's process backwards.

They run these projects to ensure that a)The existing Skylon iteration is big enough to accommodate potential customers or b)What size or other part of it needs to be re-sized to to accommodate them. Skylon is on the "D" level of its iteration so it's actually been through 4 major design cycles, although C was the first public design.
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(Not to mention a hypersonic passenger plane.)
Then why mention it? It's a separate project that was sponsored by the EU.
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And Bond rejects out of hand any suggestions that Skylon may not be the optimal design (as John echoes, above). If you were an "airframer", would you get mixed up with an engine company which behaves like that? Or wait until they fail and just licence the engines from whoever buys the IP, and develop your own clean-sheet design?
What a delightful plot for a James Follet novel.  :)

IRL Engine makers make engines and airframers make airframes. The situation is somewhat analogous to that still paper airplane the "SR72." do you expect LM to wait till Aerojet fails and buy up their IP as well?
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To me, it's like some who wants to develop the world's first jet engine. So far they have one compressor fan. But they've not only designed the rest of the engine, and designed the entire airliner around that engine, and insisted it's the only possible design, but they are proposing new airport designs based around the door spacing on that proposed airliner for the proposed engine for which they have (after 20 years) only built a single compressor fan.
Your PoV would make a lot more sense if there was someone out there saying "no, that's not how a partially air breathing HTOL SSTO should be built."

Except there is no one arguing that and the Skylon design makes good sense. In fact when NASA looked at combined cycle vehicles using TBCC they came up with a remarkably similar vehicle
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But you dare suggest they are being a bit premature...
{sigh} Why is this idea so prevalent in aerospace?

Two is more than one, so therefore it must cost twice as much to develop an aircraft to carry freight between cities and a truck to ferry between individual customers and the airfreight terminals than to develop a single vehicle which can fly between cities but land directly on the customers' driveways. Must. Because two is more than one.
Perhaps because the launch problem isn't like your rather elaborate metaphor?

You might like to study the real 2 stage vehicles proposed under the original Shuttle programme. Or you might like to glance through the thread I started on the idea of a "Triamese" shuttle.
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and the testing around hypersonic separation.

Only if they were stupid.

When Chris is suggesting smaller stepping stones, when that's the entire premise of his argument, why would you assume he would be suggesting the hardest possible version of TSTO?
You clearly know his mind better than we do. Perhaps you could explain his thinking?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/19/2015 12:07 PM
I'm not an expert on any of this so feel free to correct me, but wouldn't it make more sense to develop a TSTO Skylon in such a way that the skylon makes a suborbital hop and, once outside the brunt of the atmosphere, open the cargo bay and deploy an upper stage to which the payload is attached?

In fact, hasn't something similar to this concept been proposed in this (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30547.0;attach=535740) study by Mark Hempsell?

It'd certainly be less complicated than staging inside the atmosphere at hypersonic velocities IMO.
Yet another new forum visitor. You really are coming out of the woodwork today.  :) Welcome.

Your line of reasoning leads to the logical conclusion that the simplest process is to not stage at all does it not?

I'm not sure where you're reading about sub orbital staging in the paper you cited.  Hempsell in a previous thread mentioned REL had looked at this. REL studies indicated a sub orbital flight could put 30 tonnes into LEO if the payload could supply sufficient delta V to circularise it's orbit.

IIRC no one they've been talking to said they really need this and further studies showed that the window between doors open, payload deployment and doors closed before re entry began was tight. With no one actually asking for it and little margin for error they deleted it as an option from the latest issue of the Skylon user manual.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Krevsin on 02/19/2015 12:41 PM
Your line of reasoning leads to the logical conclusion that the simplest process is to not stage at all does it not?
Not really. In the "suborbital + kick stage to orbit" TSTO method, your primary carrier doesn't need to have quite as thin a mass margin than in a fully SSTO vehicle. It gives you more room to work with.

The only reason it goes above the atmosphere is to avoid the trouble with staging at hypersonic velocities while in the thick atmosphere.

I'm not sure where you're reading about sub orbital staging in the paper you cited.
Sorry, my bad. What I mostly meant with the study was that it contained the "fluyt" stage which could be scaled down from a GEO/Lunar transfer stage to a orbital circularization stage.

Of course, the down side of all this kick stage mallarkey would be a smaller space for payload in the cargo bay, but given the larger mass fraction thus allowed, the cargo bay would have (probably) been expanded somewhat. I'm unsure on this.

IIRC no one they've been talking to said they really need this and further studies showed that the window between doors open, payload deployment and doors closed before re entry began was tight. With no one actually asking for it and little margin for error they deleted it as an option from the latest issue of the Skylon user manual.
Those were some issues that I have also considered, but given the fact that Skylon is a reusable system, in case of running the margin too close for comfort, the people launching could easily simply opt not to deploy the payload and simply return Skylon to the ground, with the payload intact, and try again after adressing any issues which might have cropped up.

So, while the deployment window is short, I believe it is manageable.


The real issue with this TSTO concept I've outlined (at least from what I can tell) lies in getting the Skylon back to its launch site, as that would probably require prohibitive amounts of fuel so two facilities, one for launch and one for landing would most likely be required. Which would probably run the infrastructure maintenance bill through the roof.

Yet another new forum visitor. You really are coming out of the woodwork today.  :) Welcome.
Thanks.  :)
I've been registered here a while, but I mostly prefer to lurk as I often feel like I don't really have anything to add to the conversation.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/19/2015 02:45 PM
Not really. In the "suborbital + kick stage to orbit" TSTO method, your primary carrier doesn't need to have quite as thin a mass margin than in a fully SSTO vehicle. It gives you more room to work with.

The only reason it goes above the atmosphere is to avoid the trouble with staging at hypersonic velocities while in the thick atmosphere.
You're operating under a very big misunderstanding.

Thin mass margins apply to vertical take off SSTO's and all rocket HTOLs.

Skylon is neither. Air breathing to Mach 5.5 raises the average Isp to something like 5x what you get from an all rocket design and hence a much bigger payload mass fraction. Roughly speaking SABRE costs 20 tonnes to buy 100 tonnes off the LOX mass budget.  Being HTOL it also avoids needing SABRE thrust to be > than it's T/O mass. They can be about 1/3 that and (like ordinary conventional aircraft) get the job done.

That does 2 things. 1) Gives a mass fraction in the possible range for an HTOL SSTO and 2) Gives a payload fraction as good as an ELV of the same GTOW. This has never happened before. SSTO proponents have always expected to take a payload reduction and make up for it with more launches.  Skylon does not need to do this.

2) matters when you have to raise funds since why would people pay for a system that cannot at least match what a TSTO does already?
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Sorry, my bad. What I mostly meant with the study was that it contained the "fluyt" stage which could be scaled down from a GEO/Lunar transfer stage to a orbital circularization stage.

Of course, the down side of all this kick stage mallarkey would be a smaller space for payload in the cargo bay, but given the larger mass fraction thus allowed, the cargo bay would have (probably) been expanded somewhat. I'm unsure on this.
Flyt can't fit in the cargo bay in one piece. It's designed to work only in vacuum. The Skylon Upper Stage is designed to take payloads from LEO to GTO before returning and is now included in the budget.
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Those were some issues that I have also considered, but given the fact that Skylon is a reusable system, in case of running the margin too close for comfort, the people launching could easily simply opt not to deploy the payload and simply return Skylon to the ground, with the payload intact, and try again after adressing any issues which might have cropped up.

So, while the deployment window is short, I believe it is manageable.
I'll quote what Hempsell, who was with REL at the time, had to say.

Advanced Concepts / Re: The Reaction Engines Skylon Master Thread (4)
« on: 10/17/2014 04:23 PM »

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Quote from: lkm on 10/17/2014 03:19 PM

    With regards to Skylon forming  part of a military weapons platform, the Skylon user manual does detail the suborbital deployment of payloads of up to 30mt at Mach 20. Couldn't a module be designed to rack launch a load of HTV-2 like prompt global strike weapons using that mission mode?
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Sorry; sub-orbital deployment is off the menu and is not in the latest issue of the Users' Manual.  There were problems making the reentry work and, as there was no identified use for it, we gave up trying to find a solution.  We found the very low orbit deployment worked better for maximising the payload.

A further point is that the front payload mounting interface is now designed for a maximum of 17 tonnes so at the moment that is the biggest payload that can be carried regardless of where it is deployed.

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The real issue with this TSTO concept I've outlined (at least from what I can tell) lies in getting the Skylon back to its launch site, as that would probably require prohibitive amounts of fuel so two facilities, one for launch and one for landing would most likely be required. Which would probably run the infrastructure maintenance bill through the roof.
Yes and no. In air breathing mode Skylon is about 150 tonnes lighter, so a conventional runway could handle the landing.  Skylon is also a pretty good glider. The wings look too small but that's because the body is so big and so empty. It's a lot more aerodynamic than the Shuttle was. REL expect the D revision to have transatlantic range in air breathing mode. LH2 is qutie expensive at around $8.29/Kg but that would still mean a fully fueled fly back would be less than $500k.

The real problem is likely to be takeoff noise from the down range airport. Even 150 tonnes lighter and substantially throttled back a Skylon on takeoff will be very loud.  :(
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Yet another new forum visitor. You really are coming out of the woodwork today.  :) Welcome.
Thanks.  :)
I've been registered here a while, but I mostly prefer to lurk as I often feel like I don't really have anything to add to the conversation.
SABRE/Skylon is now in it's 5th thread. There's been a lot of discussion and a lot of ideas have come up (sometimes on several occasions). The site search function is very useful for finding out if something has come up before. Sadly it seems there's no way I can find to search a whole thread, rather than 1 page at a time.  :(

Electromagnetic catapult launch, catapult launch up a mountain, landing on a shallow water pool (to spread the load) have all come up already. 

Happy reading.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Krevsin on 02/19/2015 02:56 PM
I see. Well, thanks for the info.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/19/2015 03:48 PM
The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't have a biography to hand of each one of them but I suggest that it's a sweeping statement to say that they have no experience in system integration.  At the very least some of them are veterans of Blue Streak and others of the aerospace industry.

But that goes for almost any aerospace start-up. Among its employees you would expect to see some veterans from other aerospace firms - but that does not mean that the "organizational experience" as a whole translates to this new organization. 

In other words SpaceX was "unproven" until they actually flew something successfully. (That would be the F9 btw :) )

Got it.
They are an engine company not an airframe company.   Let the airframe company use its great institutional experience for its part of the work.

That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.

??? And your point? Engine companies have done that before, quite often and often with "notional" airframes to boot rather than ones that have been actually researched. Pratt-&-Whitney, GE, Mardquart to name a few. Some of them have published "studies" that made claims to those factors for everything from SCramjets to StrutJet systems. Occasionally they will actually "quote" airframe manufacturers but more often than not (since involving them costs money) they will "interpret" data from other airframes and or "other" source material.

There'd be no shame in their saying "we don't know yet".

Isn't there? After all, yourself being an example, there are people who are taking them to task FOR "not-knowing" what they are talking about when they DO talk about subjects and methods they have experience with :)

They are making, (as I pointed out many "engine" companies do) educated projections based on available knowledge and assumed performance with some very deep margins for the assumptions involved.

Actually, that demonstrates my point quite well.  DC-X never progressed to an operational vehicle.  It was never more than a sub-scale technology demonstrator.  Working on DC-X wouldn't give any experience with the very difficult transition from technology demonstration to a system that is economically successful as an operational system.

And "worked on" isn't the same as being in charge.

Actually what it "demonstrates" is you don't even have a firm grasp on what you mean to say and therefore keep moving the goal posts as you argue :)

The DC-X was, if you'll recall a "SSTO-Rocket-Powered-subscale demonstrator vehicle with NO intention other than demonstrating several ancillary "functions" of such a vehicle not any of the "substantive" functions thereof.

It "proved" that VTVL and fairly "quick" operational turn around were possible on a vehicle that faced nor addressed none of the substantial challenges to actual operational flight.
"Learning" experience here was consistent with operations and data acquisition for an LH2 rocket engine over the lifetime of the program and various issues and questions relating to those operations. Directly applicable to what amounts to a rocket powered air/LH2 engine such as Skylon.
(Note: Also applicable was the experience gained from that program which was directly related to the "future development" of a fully operational vehicle as proposed by the manufacturer of the vehicle and this was one of the reasons that led Mr. Hempsell to conclude that with current technology a solely rocket powered SSTO vehicle wasn't viable and turned his interest towards air-breathing designs :) )

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REL is the one who chose to design it for an SSTO vehicle.  They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.

And everything gets cheaper when things are smaller.

And they "choose" to do so due to issues with scaling of the engine and LH2 propellant. They also DID run a trade study on a TSTO versus an SSTO vehicle and found that the favored design was an SSTO rather than breaking the design into a fully-TSTO design.
(I should point out that "technically" the Skylon IS a fully-reusable TSTO design since the "target" market is GTO/GEO and not LEO so a "second" stage is needed to complete the mission. A "fully-reusable" baseline TSTO therefore would require a "third" stage of similar design to achieve the stated goal as well)

Further while it IS true that TSTO designs have excess "margin" to allow for possible design and operational changes they also have those margins only to a limited extent as has been shown by the SpaceX Falcon-9 design. Referencing the trades that REL did showed that the "margins" allowed by the current suggested design of the Skylon allow very similar margins while using the SSTO design over the increased complexity and cost of a TSTO design.
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Getting to Mach 5.5 isn't the challenge.  They still have to get to Mach 25 to make orbit.  True, in some ways it's easier if they're only air breathing to Mach 5.5.  But in other ways it's harder.  They have to carry much more oxidizer, and their engine has to work well in both air-breathing and rocket mode.  Going from Mach 5.5 to Mach 25 in rocket mode (with some of that rocket mode in the dense part of the atmosphere at Mach 5.5) means they need a very good mass fraction.

Note that while "you" don't think they have thought of this "issue" the plain fact is they have done a LOT of work on this and have come to the conclusion that a ROCKET BASED rather than some form of turbine-engine based engine design actually fits this criteria. Funny enough that was a conclusion reached by most researchers in the field by the late 1950s. Unfortunately several mis-assumptions crept into the field at that same time which REL have managed to avoid. (Such as a requirement for air-liquification for rocket engine use rather than deep cooling, ramjets being "required" to reach speeds between Mach-3 and Mach-6, and the "need" for SCramjet engines to allow high hypersonic air-breathing flight, etc)

The SABRE is a "good" rocket engine that can be operated "decent" air-breathing engine from a standing start to around Mach-5.5. From there is goes back to being a "good" rocket engine using on-board propellant to go from Mach-5.5 to around Mach-25 and orbit. The rocket equation (modified) shows this has enough performance to allow some pretty hefty mass-margin and a very robust mass-fraction with the given design. Rocket engines, and materials science have come a long way from the 1950s and thankfully REL never even considered using multiple engine types to close their design :)

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Like I said, they don't have exactly the same challenges NASP had, but they have very great challenges, and I think they're at a comparable level of difficulty.  Apparently, others think they are too, which is why others are continuing SCRAMJet research and development.

SCramjet research and development continues because of the "promise" of hypersonic flight within the atmosphere despite the problems and issues of such flight. In 'theory' a SCramjet can fly to beyond Mach-24 and that 'theory' looks really, really good despite some obvious flaws in the full logic chain. (As an example, its obvious that internal airflow within a SCramjet at speeds of around Mach-15 become so hot that even with hydrogen fuel further operation {acceleration} is unlikely. Operations above that speed induce 'plasma' like flow where NO amount of additional fuel will continue operations but that's not ever mentioned when SCramjets research and development is discussed.

"Truth" is that REL is working on and from the point where air-breathing, rocket based, acceleration engines was "going" before it was side-tracked in the 1950s/60s. The "challenges" are significantly less since the vehicle is not designed to nor will it remain in the atmosphere any longer than needed.

"Smaller-is-cheaper" is pretty much an aerospace "law" for intents and purposes and yes it would be "nice" if REL could do a demonstrator first but there is a minimum size for a fully operational SABRE engine and LH2 propellant system capable of supporting the same. And yes its "tricky" because LH2 is required for the deep cooling effect which is the basis of the system, but that's actually a requirement, not a choice. Liquid Hydrogen systems do not as a rule lend themselves to "small" systems in any sort of "operational" use. The only way REL could build a significantly "smaller" system would be to forgo the use of LH2 for a more compact but MUCH less capable propellant and they have already PROVED the engineering of an LH2 heat exchanger system so what would be the point?

REL plans on "demonstrating" a full sized SABRE engine operationally for the full flight duration and then moving on to an actual airframe designed and built with the help of a fully "proven" builder. But in order to do the "testing" necessary for a "full-duration" test of the engine they need to have an idea of what the airframe and its effects on performance will be. Not even REL is expecting the Skylon to turn out EXACTLY as they propose but until an airframe company steps forward and proposes their own idea with accompanying data REL has to make its own way. (And note that while others HAVE proposed different designs REL has not outright rejected those designs)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/20/2015 06:21 AM
In other words SpaceX was "unproven" until they actually flew something successfully. (That would be the F9 btw :) )

Actually it'd be the F1.

SpaceX actually did the whole incremental development thing. Are still doing it. And I think it explains a lot about their success. Imagine they had tried to jump directly to MCT/Raptor. (Even then, I think they are still skipping necessary stepping stones.)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/20/2015 08:06 AM
I wonder if we can move the discussion on by agreeing on a few things.

1)Reaction Engines Limited is not SpaceX.

2)It's development approach is completely different to that of SpaceX.

3)REL are not going to change their development approach because of anyone's opinion on the matter.

4) SpaceX have built a very fine ELV for (by government cost modelling standards) a very modest budget.

5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison.

6)The arguments that "It's never been done before" or "Others have tried and failed" are in fact the reason why startups are started.  Their founders believe something can be done which has either not been done before or where previous attempts have failed. That definition applies to REL, SpaceX, XCOR, Blue and in fact any start up trying to do something that has never been done or never been done successfully before, probably including whatever start ups some of the other posters here are working for.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 02/20/2015 08:19 AM
5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison.

You're right. It's not a fair comparison. One is flying, hopefully partially reused soon. The other... is just something on a paper.
 - A) Skylon is not "fully reusable", because it does not exist.
 - B) Skylon can not "deliver at least 15 tonnes to LEO", because it does not exist.
 - C) Skylon can not "deliver at least 6 tonnes to GTO", because it does not exist.

Are you catching my drift? It's always easy to make a paper project look better in comparison to any existing hardware. Reality can be slightly more difficult.  :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/20/2015 09:14 AM
4) SpaceX have built a very fine ELV

And REL have built a heat exchanger.

They have not built SABRE and are nowhere near ready to build even a test version of SABRE. They have not built and are not building Skylon. They have built a heat exchanger. Can we agree on that? I think that would move any discussion on much more.

Whereas insisting...

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5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison.

...seems to be the very thing that prevents any progress in the discussion.

Chris's post (which started the discussion that so far dominates Part 5) was asking if Skylon might not the best development path for REL's proposed technology. They are trying to jump too many steps ahead of themselves. Hence 20 years and all they have is a heat exchanger. Surely after all this time, we're allowed to ask, "Is this the best path?" Is that question so offensive to you?

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6)The arguments that "It's never been done before" or "Others have tried and failed" are in fact the reason why startups are started. Their founders believe something can be done which has either not been done before or where previous attempts have failed.

REL is trying to develop a fundamentally new type of engine. A radical air-breathing jet engine/rocket hybrid. When you are doing something so untried, so deep in unexplored territory, you don't try to lock down the end design of a vehicle that might use that engine. Simply because you can't. That's all people are saying. That's what you can't seem to move beyond.

REL doesn't and can't know the actual performance of any eventual engine. None exist, and the very concept is so new and untried that there's no reasonable extrapolation from prior technology. Therefore, without that, they cannot possibly design a vehicle yet. So the idea that this early in the process they are designing end-user missions around the size of the payload bay of that vehicle is bonkers.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/20/2015 10:58 AM
And REL have built a heat exchanger.

They have not built SABRE and are nowhere near ready to build even a test version of SABRE. They have not built and are not building Skylon. They have built a heat exchanger. Can we agree on that? I think that would move any discussion on much more.
So far the only person arguing that point is you with yourself. Strawman arguments tend to be the starting point for trolls. You might like to keep that in mind.
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Whereas insisting...
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5) To be a valid comparison for Skylon any competitor has to be a) Fully reusable b) Able to deliver at least 15 tonnes to LEO c) Able to deliver at least 6 tonnes to GTO. If a candidate vehicle cannot manage this then it's not a valid comparison.

...seems to be the very thing that prevents any progress in the discussion.
Not at all. This is REL's choice. It's what they are planning to build since they revised the design in 2010. Please note the thread title.
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Chris's post (which started the discussion that so far dominates Part 5) was asking if Skylon might not the best development path for REL's proposed technology. They are trying to jump too many steps ahead of themselves. Hence 20 years and all they have is a heat exchanger. Surely after all this time, we're allowed to ask, "Is this the best path?"
And it has been asked over the last 4 threads. But since you seem so concerned about the design, what's your design for a SABRE carrying vehicle?
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Is that question so offensive to you?
Not in the slightest. The number of posts I've read have enhanced my tolerance of even the most stupid of comments.
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REL is trying to develop a fundamentally new type of engine. A radical air-breathing jet engine/rocket hybrid.
Actually not that radical, in fact much less radial than the LACE concepts running around the National Aerospace project (the original one in the early 60's). Using William Eschers taxonomy it even has a name. A "Deeply pre cooled air turbo rocket."
Trouble was no one could get the frost control to work in the inlet heat exchanger.   :(
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When you are doing something so untried, so deep in unexplored territory, you don't try to lock down the end design of a vehicle that might use that engine. Simply because you can't.
And yet that was exactly what SpaceX did with the F9. There's a difference between Science and Engineering. REL have done Science to do Engineering. Spacex have done Engineering, now they are doing Science. And Science is not predictable
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That's all people are saying. That's what you can't seem to move beyond.
No that's what 2 people are posting. And what other people with more experience in this area are posting is that actually engine companies in the aircraft business do this regularly.


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REL doesn't and can't know the actual performance of any eventual engine. None exist, and the very concept is so new and untried that there's no reasonable extrapolation from prior technology. Therefore, without that, they cannot possibly design a vehicle yet. So the idea that this early in the process they are designing end-user missions around the size of the payload bay of that vehicle is bonkers.
Wow.  ???
Just wow.

That statement alone tells me you have no understanding of the thermodynamics underlying all engines (rocket, Diesel, gas turbine, ram or SCramjet), dating from the mid 1700s, and even less about the changes in computer modelling over roughly the last 65-70 years.  :o

You appear to think engine design (of all types) is stuck in the 1950's, where cut-and-try was the only option.

Thank you for that. It means I won't have to waste a second more responding to you. Good bye.  :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/20/2015 12:38 PM
4) SpaceX have built a very fine ELV

And REL have built a heat exchanger.

They have not built SABRE and are nowhere near ready to build even a test version of SABRE. They have not built and are not building Skylon. They have built a heat exchanger. Can we agree on that? I think that would move any discussion on much more.

It seems to me that this debate is about the attitude we should all have more than about facts since I can't remember anyone suggesting that REL have built things they haven't built.

I'm interested in what happens assuming they get things mostly right or what they might do if this or that issue turns out to be more difficult  because the alternative is that they go bust and the world is the same as before which is a non-story - why discuss it?

We might as well mention that lots of people have built rockets before but this heat exchanger is exceptional so it speaks for their ability to come up with something unheard of and get it done right.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 02/20/2015 01:35 PM
To start off the new thread, here's a summary of my own reasons for being skeptical about Skylon.  Some of these views are probably shared by other skeptics.  Feel free to reply with opposing views; hopefully, this will help clarify exactly where opinions differ and help undecided readers of these forums see both sides and make up their own minds.

First off, I don't think there's a known flaw in Skylon that definitely makes it impossible.  It's not like a perpetual motion machine that violates known laws of physics.  My issue with Skylon is that there are too many unknowns and the proponents of Skylon assume those unknowns will work out, while history shows this is seldom the case.  There are enough unknowns and enough projections that seem very optimistic to me that the odds of Skylon actually achieving its goals seem remote to me.

The people working on Skylon have been working on the idea for decades.  They are certainly dedicated and well-meaning, and they have some competence.  But they have been working on theory and small components.  They don't have experience in system integration.  They haven't built real flight hardware.  They haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system.

I don't think you are fully aware of the background the REL team. Mark Hempsell for example worked on the DCX.
http://forum.nasaspaceflight.com/index.php?topic=19127.msg493088#msg493088

Actually, that demonstrates my point quite well.  DC-X never progressed to an operational vehicle.  It was never more than a sub-scale technology demonstrator.  Working on DC-X wouldn't give any experience with the very difficult transition from technology demonstration to a system that is economically successful as an operational system.

And "worked on" isn't the same as being in charge.

Except that wasn't your point at at, your point was quite clear. That people in REL lacked "experience in system integration", "haven't built real flight hardware", and "haven't seen a system from concept through to all the inevitable compromises necessary to make a practical system". The DC-X clearly meets your original point which had no requirement of being in charge or the end system becoming operational. Other projects that meet that criteria plus your newly added one of operational status are the EJ200, Spey and RB211 which Richard Varvill and John Scott Scott worked on, respectively.



The team at REL has consistently proposed building a large-scale single-stage-to-orbit system.  That shows poor judgement, in my opinion.  SpaceX started with Falcon 1.  Then then moved to a full-expendable Falcon 9.  Now they are working on perfecting reuse of only the first stage.  Along the way, they have learned many lessons and constantly changed their plans, all while retaining their goal of greatly reducing the cost of launch.  I believe that kind of incremental, flexible approach is very effective.  It is the opposite of the REL approach.  With REL going directly for a huge, single-stage-to-orbit system, there is little room to learn operational lessons and change plans.  And Skylon is so much different from existing systems it is very likely to need far more flexibility for lessons learned than Falcon.

SABRE is a SSTO engine, I'm not sure what intermediate stage there can be for engine explicitly designed to take a single stage into orbit. I can't imagine designs cost get significantly smaller by making a smaller version.

REL is the one who chose to design it for an SSTO vehicle.  They chose to optimize it for that role rather than as part of a reusable first stage of a two-stage launch system, which would be the more conservative choice and give them more margin and require much less in the way of pushing the edge of what technology can do.

And everything gets cheaper when things are smaller.
When are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE?
 Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does?   
What engine is powering the second stage?
How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.


There have been many programs with similar or lesser optimistic goals that have failed.  The U.S. National Aerospace Plane had far more resources available and a similar level of technological challenge, and it failed.  Note that I'm not saying the details of the technological challenge are similar -- they are not.  But the programs are similar in having a goal that required many unknowns to be overcome and having people with some competence in specific areas convinced they could overcome them.
The technical challenge of airbreathing to Mach 18 is clearly of a vastly higher level than airbreathing to Mach 5.5 and the number of unknowns in geting to Mach 18 in 1984 far greater than achieving Mach 5 thirty years later.

Getting to Mach 5.5 isn't the challenge.  They still have to get to Mach 25 to make orbit.  True, in some ways it's easier if they're only air breathing to Mach 5.5.  But in other ways it's harder.  They have to carry much more oxidizer, and their engine has to work well in both air-breathing and rocket mode.  Going from Mach 5.5 to Mach 25 in rocket mode (with some of that rocket mode in the dense part of the atmosphere at Mach 5.5) means they need a very good mass fraction.

Like I said, they don't have exactly the same challenges NASP had, but they have very great challenges, and I think they're at a comparable level of difficulty.  Apparently, others think they are too, which is why others are continuing SCRAMJet research and development.
I can't help feel that rocketry (successfully putting things in orbit since 1957)  is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.

The X-33/VentureStar is another launch program that had optimistic goals and failed.  I think that X-33/VentureStar looked far more realistic at its outset, with less of a techonological leap required, than Skylon today.  And yet it failed because of the engineering details in turning the theory into reality.

X-33 didn't fail, it was cancelled due to a change in administration, just as many Clinton era space programs were cancelled by the Bush administration. What many people forget is that the X-33 was just a rocket powered x-plane like the X-15, like the X-15 it had a ton of not flown before technology some of which had teething problems, and like the X-55 if it had flown it would have provided invaluable hypersonic flight data.

Getting into the details of X-33 is off topic, but lets just say that opinions differ about X-33 -- many people believe it was cancelled because the progress up to that point indicated it was not able to meet its projections and wouldn't have been viable.

Many people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why  should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 02/20/2015 03:29 PM
There's a difference between Science and Engineering. REL have done Science to do Engineering. Spacex have done Engineering, now they are doing Science. And Science is not predictable

This paragraph deserves some kind of award. ;D It should be smooth sailing for REL now, then!  ;)

EDIT: To offer a more substantive response. I don't think the line between science and engineering exists as you think it does. And what scientific breakthroughs have REL done? Their pre-cooler work would be classified by most as an impressive piece of engineering.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/20/2015 03:53 PM
In other words SpaceX was "unproven" until they actually flew something successfully. (That would be the F9 btw :) )

Actually it'd be the F1.

SpaceX actually did the whole incremental development thing. Are still doing it. And I think it explains a lot about their success. Imagine they had tried to jump directly to MCT/Raptor. (Even then, I think they are still skipping necessary stepping stones.)

My bad my source list had the F1 flights as "partially successful" :) And actually they didn't as they "developed" everything from scratch and tested it as they built. Which is technically what REL is also planning on doing but which Chris is ignoring :)

Full scale engine is next and THEN maybe a full scale test vehicle. This is really more how aircraft are built than rockets which is of course the main point in their development plans.

But "my" point still stands that by the criteria Chris used, SpaceX was an "unproven" company despite all their "incremental" testing until they actually flew a successful, full-up flight :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Kansan52 on 02/20/2015 04:16 PM
I'm confused.

It has been posted that all that REL has built is a heat exchanger. My understanding is the heat exchanger is the linchpin. The rest of the engine is based on existing technology.

Is that incorrect?

If the heat exchanger is the linchpin idea is correct, then REL is suffering from NBNBR (No Bucks, No Buck Rogers - Bucks meaning money not dollars). Things will be slow due to money issues, not technology issues.

To recap, REL's heat exchanger is the show stopper and REL has accomplished that, the engine is based on known technology working with the heat exchanger (not easy but not necessarily ground breaking), and REL could work faster is they has more money.

That my understanding.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/20/2015 05:13 PM
I'm confused.

It has been posted that all that REL has built is a heat exchanger. My understanding is the heat exchanger is the linchpin. The rest of the engine is based on existing technology.

Is that incorrect?

If the heat exchanger is the linchpin idea is correct, then REL is suffering from NBNBR (No Bucks, No Buck Rogers - Bucks meaning money not dollars). Things will be slow due to money issues, not technology issues.

To recap, REL's heat exchanger is the show stopper and REL has accomplished that, the engine is based on known technology working with the heat exchanger (not easy but not necessarily ground breaking), and REL could work faster is they has more money.

That my understanding.

They (REL) have built and tested a deep-cooled air/hydrogen rocket engine which would "technically" be the "heart" of the SABRE and built and tested a heat exchanger which was tested under simulated supersonic conditions (using the exhaust of a running jet engine into the intake of the HE) which was the 'key technology' to the deep-cooled engine set up. The rest of the engine is pretty much adaption of off-the-shelf technology for turbojet compressors.

Your also correct that the main reason REL's progress has been slow is the lack of funds as what has gone before has been strictly technology development on the basic systems of the SABRE. Next REL plans on building and running a full size SABRE engine to validate their simulation and models.

(Most of which are based on well documented studies and research done since the mid-50s on similar engines cycles though none used the exact set up that REL has pioneered. I'm sad to say that a majority of the work was done in the United States and "abandoned" after the research was side-tracked into SCramjet research based on the false idea that SCramjets were both "required" and the ultimate "air-breathing" acceleration engine. Despite almost 50 years of focused research the SCramjet has yet to live up to even a third of its supposed "potential" and is far less closer to operational use than the SABRE is. They have so dominated the thinking that almost every "air-breathing" space launch concept MUST have them "tacked-on" at some point despite their lack of use in the majority of cases. Worse of course from my "pro-US" perspective is the fact that OUR engineers missed such a fundamental design flaw in their early Rocket-Based-Combined Cycle engine work in that they made a false assumption that "air-fed" rockets required the liqufication of the air prior to injection into the rocket motor. As just about anyone working on the LH2/LOX RL10 could have told them, a rocket greatly benefits from GAS injection of both the hydrogen AND the oxygen rather than liquid! Kudo's to REL but I'm still upset that the US HAD everything up to including an almost flight-weight engine ready for flight testing but circumstances didn't allow it :(  )

I suspect that once the full size SABRE is tested a lot more interest and money will be generated.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 02/20/2015 06:08 PM
i don't understand the animosity toward REL.  what have they done to offend so?  to me REL brings to mind two things -  the sentiment behind the quote “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard."   and  Concorde.

REL are working really hard on a disruptive idea that they had; one that they think can achieve the same as elon musk's goal of cheap rapid access to space for the benefit of mankind. good for them. that should inspire, not generate a load of naysaying.  what's wrong with you people?

when the space shuttle idea was proffered, did people say 'what's wrong with normal rockets?, we know how to do normal rockets'  were there naysayers arguing for incremental steps?  i don't know.  the result was awesome.   

' what's wrong with normal aeroplanes?'   and then out rolls concorde.  if there were people at the time who tried to undermine the spirit of the project,  i bet they were as awestruck as the rest of us when the result took off in front of them.

the world has been mesmerised by  spacex landing rockets and capsules; by them constructing a BFR,  and then out rolls Skylon sounding like the end of the world.   how is this bad?  if it is difficult, if it takes a long time, are they reasons for REL to give up?  of course not.  the world needs passionate and competent innovators of their ilk.  they should be encouraged.  i wonder if this thread is getting REL down. i hope not.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 02/20/2015 06:22 PM
i don't understand the animosity toward REL.  what have they done to offend so?  to me REL brings to mind two things -  the sentiment behind the quote “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard."   and  Concorde.

REL are working really hard on a disruptive idea that they had; one that they think can achieve the same as elon musk's goal of cheap rapid access to space for the benefit of mankind. good for them. that should inspire, not generate a load of naysaying.  what's wrong with you people?

Speaking for myself only, here - I have no animosity towards REL. Zero. I really do hope they succeed.

What does rub me the wrong way, however, is how the two main "Skylon evangelists" on this forum (not affiliated with REL but happy to speak on their behalf it seems)  ::) portray Skylon as a "done deal". Discussing it as of it already exists. Denigrating the hard work by done by people trying for the same goal but by different means.

There is also an element of "been there, seen that" skepticism. Skylon is just another in the long line of SSTO-ish launch concepts that were at their own time portrayed as the greatest idea since sliced bread. So some skepticism is warranted, and this is why I post - to counter the outlandish statements made quite frequently. If that is something "wrong with me", then so be it.

Does that make sense?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Impaler on 02/20/2015 06:35 PM
Siting the Space-shuttle and the Concorde as great beacons of success in this area gives me shudders down my spine.  These two vehicles are emblematic of why the criticism and doubt area valid, the Shuttle was expensive and dangerous, the Concorde could barely close it's business case in a much more established passenger service market.

And in response to JS19, if you want to count the detractors count me too, so were at 3 people now.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 06:36 PM
But "my" point still stands that by the criteria Chris used, SpaceX was an "unproven" company despite all their "incremental" testing until they actually flew a successful, full-up flight :)

Yes, I agree, SpaceX was at one time an unproven company.  If we were back at the time before SpaceX had built and tested its first engine and SpaceX were making projections about how many cycles their reusable first-stage airframe could handle, I would say they didn't have enough information to be making projections like that and that such projections shouldn't be considered reliable.  In fact, back then SpaceX thought that they would be reusing their first stages by putting parachutes on them, covering them with cork, and fishing them out of the sea.  They even made their first engines salt-water-tolerant because of that plan.  And that's exactly my point -- a company that has yet to build its first engine has a lot of unknowns in front of it.

SpaceX took a much more incremental approach, and that allowed them to learn lessons and modify their approach.  Their approach was also much less of a leap beyond the existing state of the art at the time.  That allowed them to deal with all those unknowns.  What worries me about REL is that they seem to think they know most of the unknowns already, when I don't think they -- or anyone else -- possibly could.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 02/20/2015 06:50 PM
Denigrating the hard work by done by people trying for the same goal but by different means.

If by the "same goal" you mean fully-reusable, wasn't this JS19's point; to compare SABRE/Skylon with others also aiming for fully-reusable vehicles (with ELV-like payload fraction). I follow every post on this thread (5-off), and have seen little (if any) denigration of others' hard work.

Edit: Substituted "fully-reusable" for "SSTO"
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 06:55 PM
i don't understand the animosity toward REL.

I haven't seen any evidence of animosity toward REL.  None.  I specifically said I hope they do succeed.

Skepticism is not the same as animosity.

The only animosity I've seen is between posters on this forum.

Skepticism is healthy.  People should welcome it even if they disagree.  Skepticism helps make sure the right decisions are made and makes it more likely we move forward in spaceflight, just like we all want.

what have they done to offend so?

Nothing at all.  Why do you interpret skepticism as offense?

to me REL brings to mind two things -  the sentiment behind the quote “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard."   and  Concorde.

The worry is in fact that REL will turn into another Concorde -- a waste of money and talent on a system that was not economically viable.

If you visit the Hiller Aviation Museum in San Carlos, California, you can see a large section of the front of what looks a lot like Concorde.  It was actually built by Boeing, at the same time Concorde was under development.  The Boeing program was going well and they could have completed their own supersonic airliner.  But they cancelled the project because they judged it wouldn't be economically feasible.  Boeing was right.  By cancelling that project, they freed up resources and engineering talent for other projects that benefited the aerospace industry.

If you read my earlier post carefully, you would realize I wasn't calling for the cancellation of the technology REL is trying to develop.  I was instead suggesting more caution in projections and a more flexible, incremental development approach.

REL are working really hard on a disruptive idea that they had; one that they think can achieve the same as elon musk's goal of cheap rapid access to space for the benefit of mankind. good for them. that should inspire, not generate a load of naysaying.  what's wrong with you people?

I find it very sad that you interpret well-intentioned skepticism as being a character flaw.  Even if you disagree with our skepticism, why can't you accept that it comes from good intentions?

when the space shuttle idea was proffered, did people say 'what's wrong with normal rockets?, we know how to do normal rockets'  were there naysayers arguing for incremental steps?  i don't know.  the result was awesome.   

A discussion of the Space Shuttle is off topic for this thread, but suffice it to say there are many people who think the Space Shuttle program was a mistake and a more incremental approach that didn't try to do so much would have been a better use of resources.  Many people think the space shuttle kept of stuck in Low Earth Orbit for decades when we could have been exploring far beyond.

' what's wrong with normal aeroplanes?'   and then out rolls concorde.  if there were people at the time who tried to undermine the spirit of the project,  i bet they were as awestruck as the rest of us when the result took off in front of them.

the world has been mesmerised by  spacex landing rockets and capsules; by them constructing a BFR,  and then out rolls Skylon sounding like the end of the world.   how is this bad?  if it is difficult, if it takes a long time, are they reasons for REL to give up?  of course not.  the world needs passionate and competent innovators of their ilk.  they should be encouraged.  i wonder if this thread is getting REL down. i hope not.

Blind encouragement and ignoring potential mistakes is ultimately bad for any project.  True friends are honest, even if they have to say things people don't want to hear.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/20/2015 06:57 PM
LarsJ, Do I then assume that you deride the various "Fully-reusable TSTO is a done deal" SpaceX fans the same way? :)

No Skylon is FAR from a "done-deal" but it does have many features and abilities that are inherent to its nature if it works even remotely close to what its supposed to. I am as hopeful as you are that it works but well aware of the numerous "risks" still to be retired. On the other hand I'm also a SpaceX supporter though I will admit (as many won't) the various and sundry short-comings inherent in the design and principles of that vehicle/design.

"Comparing" the two is frustratingly common and misleading as I've pointed out before.

Skepticism is to be expected for it can be overcome with education and data. (Not to mention working hardware :) ) And yes Skylon is the latest in a long line of "promising" SSTO vehicle but I'd point out that it in fact is much close to, and much easier to implement than most where and does not (at this point) really need as significant technologies as most of the previous concepts did. The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated. A full size working engine is next and really that's simply engineering the various components together and there's quite a bit of "prior-history" for that.

Impaler, not sure if you really want to be labeled as a 'detractor' as most here who actively engage in it have to rely on arguing the business case rather than technical details :) I'll admit to some trepidation on the assumptions involved but they DO actually have a historic (aircraft) model to draw on. Doubts are common and normally a good thing as long as they are not carried too far :)

I understand that many folks have differing ideas on how REL "should" proceed from this point but really a full size engine IS the next step. After that...

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Kansan52 on 02/20/2015 06:59 PM
Thanks Randy. That summary really helps me!!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/20/2015 07:08 PM
Yes, I agree, SpaceX was at one time an unproven company.  If we were back at the time before SpaceX had built and tested its first engine and SpaceX were making projections about how many cycles their reusable first-stage airframe could handle, I would say they didn't have enough information to be making projections like that and that such projections shouldn't be considered reliable.  In fact, back then SpaceX thought that they would be reusing their first stages by putting parachutes on them, covering them with cork, and fishing them out of the sea.  They even made their first engines salt-water-tolerant because of that plan.  And that's exactly my point -- a company that has yet to build its first engine has a lot of unknowns in front of it.

I'm going to point out that the bolded part is NOW not "back-then" as SpaceX does NOT have the data to make accurate predictions... yet.

Yes REL faces a lot of "unknowns" in assembly of their first engine but the basic technology and techniques are already in place. They have already retired two of the biggest with the heat exchanger and rocket. Their biggest hurdle continues to be money, not competence or capability. Where would SpaceX be without Musk and his money?

Quote
SpaceX took a much more incremental approach, and that allowed them to learn lessons and modify their approach.  Their approach was also much less of a leap beyond the existing state of the art at the time.  That allowed them to deal with all those unknowns.  What worries me about REL is that they seem to think they know most of the unknowns already, when I don't think they -- or anyone else -- possibly could.

Which unknowns would those be? I'm curious.

SpaceX's approach was highly conservative in most respects. They built an ELV with the idea of eventually turning it into an RLV. They then rebuilt it as an RLV but still usable as an ELV. In the end its going to remain an RLV that "can" be an ELV and in that sense its limited (and they admit this) and eventually will end up a "dead-end" no matter how successful. But it's a start and in the right direction so kudos and I'm rooting for them.

REL is aiming for a different vehicle, operational mode, and model from the start and they have far less resources than SpaceX did to do it with. That in no way makes one approach "better" than the other.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 07:23 PM
Yes, I agree, SpaceX was at one time an unproven company.  If we were back at the time before SpaceX had built and tested its first engine and SpaceX were making projections about how many cycles their reusable first-stage airframe could handle, I would say they didn't have enough information to be making projections like that and that such projections shouldn't be considered reliable.  In fact, back then SpaceX thought that they would be reusing their first stages by putting parachutes on them, covering them with cork, and fishing them out of the sea.  They even made their first engines salt-water-tolerant because of that plan.  And that's exactly my point -- a company that has yet to build its first engine has a lot of unknowns in front of it.

I'm going to point out that the bolded part is NOW not "back-then" as SpaceX does NOT have the data to make accurate predictions... yet.

Yes, they don't have the data to be fully confident.  It's still somewhat uncertain.  But having actually designed, built and flown real stages, done water landings, flown Grasshopper and F9R-dev1 in Texas, they do have some data to go on.  They have done enough to be far, far more confident about how many times they can re-use it than REL.

Yes REL faces a lot of "unknowns" in assembly of their first engine but the basic technology and techniques are already in place. They have already retired two of the biggest with the heat exchanger and rocket. Their biggest hurdle continues to be money, not competence or capability. Where would SpaceX be without Musk and his money?

True, Musk was an asset to SpaceX without a doubt.  But he had $100 million to invest.  REL says they need more than 100 times that amount of money.

REL needs both investors and a cheaper program to have a better shot at actually succeeding.

Quote
SpaceX took a much more incremental approach, and that allowed them to learn lessons and modify their approach.  Their approach was also much less of a leap beyond the existing state of the art at the time.  That allowed them to deal with all those unknowns.  What worries me about REL is that they seem to think they know most of the unknowns already, when I don't think they -- or anyone else -- possibly could.

Which unknowns would those be? I'm curious.

They are all the things that aren't anticipated in advance that are learned when doing the detailed design and when doing flight tests of that design.

SpaceX's approach was highly conservative in most respects. They built an ELV with the idea of eventually turning it into an RLV. They then rebuilt it as an RLV but still usable as an ELV. In the end its going to remain an RLV that "can" be an ELV and in that sense its limited (and they admit this) and eventually will end up a "dead-end" no matter how successful.

Huh?  That makes no sense to me.  Because it can be used as either an expendable or reusable vehicle it's a dead end?  Just because it can be used as expendable doesn't mean it's any less effective as a reusable vehicle.

But it's a start and in the right direction so kudos and I'm rooting for them.

REL is aiming for a different vehicle, operational mode, and model from the start and they have far less resources than SpaceX did to do it with. That in no way makes one approach "better" than the other.

The SpaceX approach has so far succeeded.  Past programs that were more like the REL approach have failed.  That's what makes one approach better than the other.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/20/2015 07:53 PM
I haven't seen any evidence of animosity toward REL.  None.  I specifically said I hope they do succeed.

I don't think it's YOU that's being referred to :) I seem to recall at least one post where REL was called an outright 'fraud' which I think would be considered "animosity".

Quote
Skepticism is not the same as animosity.
Skepticism is healthy.  People should welcome it even if they disagree.  Skepticism helps make sure the right decisions are made and makes it more likely we move forward in spaceflight, just like we all want.

No it's not and in measure its a good thing. However, skepticism focused on "second-guessing" someone who's actually "done-the-math" and bent metal in testing is another level. (One I'm guilty of with SpaceX at times I must admit :) )

And how 'helpful' is skepticism when it is mis-directed and/or non-constructive? Not that it probably actually matters since we're on these forums and both SpaceX and REL would seem to read but not take our "opinions" into their consideration :)
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The worry is in fact that REL will turn into another Concorde -- a waste of money and talent on a system that was not economically viable.

And it's from this "point-of-view" that your argument make no sense :) REL is not Boeing (your example) and if Boeing DOES come on-board at some point they will have made the exact calculations and studies you mention. You seem to assume that "someone" is going to blindly accept REL's figures which hasn't been done by anyone so far as evidenced by the "lack" of investors beating down their door. The "talent and money" they are using is the same ones they started out with and they DON'T have "other" business that they are taking these from. So your 'fear' would seem groundless which makes me suspect its NOT what your really questioning :)
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If you read my earlier post carefully, you would realize I wasn't calling for the cancellation of the technology REL is trying to develop.  I was instead suggesting more caution in projections and a more flexible, incremental development approach.

Got that but you don't seem to understand the limitations on REL due to the technology involved. They ARE being incremental. Unless the SABRE under-performs by a very significant margin their work shows that going with a TSTO design WOULD be un-economical (which is supposedly an underlying concern of yours) compared to a fully SSTO design. If this is "true" then they will find out with the full-up engine demonstrator and thereby adjust their development plans accordingly. (Considering that Mardquart had an Mach-4.5 "almost-flight-weight" LH2/LOX capable RBCC-SERJ engine ready for testing in the early 1960s WITHOUT deep-cooling or an air-fed rocket motor I consider this an unlikely complication)

Again, your "skepticism" seems misdirected.

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I find it very sad that you interpret well-intentioned skepticism as being a character flaw.  Even if you disagree with our skepticism, why can't you accept that it comes from good intentions?

"I" don't consider it a character flaw BTW so we're clear :) But I DO have to wonder at the "intentions" given the circumstances. "Supporters" are being accused of "blind encouragement," "ignoring problems," and "Skylon evangelism" despite real attempts to answer and address questions and skepticism about the concept. Is it perhaps that BOTH sides are missing the point that the discussion comes from "good intentions" on both sides?

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A discussion of the Space Shuttle is off topic for this thread, but suffice it to say there are many people who think the Space Shuttle program was a mistake and a more incremental approach that didn't try to do so much would have been a better use of resources.  Many people think the space shuttle kept of stuck in Low Earth Orbit for decades when we could have been exploring far beyond.

Point here is that the "Space Shuttle" for good or ill IS the only current example of an operational RLV and therefore the "comparisons" no matter how inaccurate are inevitable as well :) Just like comparisons to the F9 seem to be despite the lack of "common-ground" for such :)

(And anyone who even THINKS that it was the Shuttles "fault" we've been stuck in LEO for the last 40+ years is simply looking for an excuse to ignore the real reasons and why those reasons will continue to manifest themselves as long as the "government" is the driving factor)

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Blind encouragement and ignoring potential mistakes is ultimately bad for any project.  True friends are honest, even if they have to say things people don't want to hear.

Yep :) Shall we proceed from that point and continue the discussion friend? :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SteveKelsey on 02/20/2015 08:01 PM
Maybe it helps to bring it down to the differentiator. REL have delivered a pre-cooler that can enable a new air-fuelled rocket engine. This is a matter of fact, not opinion. The SABRE offers margins that are robust enough to enable reusable SSTO to be considered.
I don't think anyone is suggesting that the pre-cooler is anything other than a breakthrough.
From this breakthrough REL have projected what they believe they can deliver with the technology. There will be many other applications that are easier to deliver than an SSTO but that’s the deliver REL want to make.
Its entirely reasonable to point out that REL have a long way to go, and that the design will mature as learning progresses but just maybe the projections for and against have become a little ....searches for suitably diplomatic term...abstract?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 02/20/2015 08:15 PM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 08:24 PM
I haven't seen any evidence of animosity toward REL.  None.  I specifically said I hope they do succeed.

I don't think it's YOU that's being referred to :) I seem to recall at least one post where REL was called an outright 'fraud' which I think would be considered "animosity".

Agreed.  I've never gotten the impression REL is a fraud.  On the contrary, I think the people there are very dedicated to their vision and have chosen to work on it for many years on lean funding in spite of the fact I'm sure they could find more lucrative things to do.

Is it perhaps that BOTH sides are missing the point that the discussion comes from "good intentions" on both sides?

That's a good point.  I think it always helps to assume that even those we disagree with have good intentions.

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Blind encouragement and ignoring potential mistakes is ultimately bad for any project.  True friends are honest, even if they have to say things people don't want to hear.

Yep :) Shall we proceed from that point and continue the discussion friend? :)

Yes! :-)  Skepticism of my skepticism is fair.

I think this particular discussion has more or less run its course.  We've all made our points, and other readers can judge for themselves what they find most persuasive.

I look forward to hearing more news from REL in the future so we have new things to discuss.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 02/20/2015 08:53 PM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?

It appears so; there have been a number of nozzle and flow demonstrator engines built and tested by REL and their associates:

STRICT
STERN
STRIDENT
STOIC
STILETTO

http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=33648.0;attach=571189
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 09:35 PM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?

It appears so; there have been a number of nozzle and flow demonstrator engines built and tested by REL and their associates:

STRICT
STERN
STRIDENT
STOIC
STILETTO

http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=33648.0;attach=571189

Yes, those are important pieces of hardware being tested.  I think it's fairer to call them engine component tests rather than engines, though.  None is something you could put on a vehicle and have it fly.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/20/2015 10:48 PM
What would people think of separating this thread into two threads: Skylon Updates and Skylon Discussion?  There's been a lot of discussion in the Skylon threads, and not everyone who is interested in hearing about news from Skylon has the time or inclination to follow all the discussion.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 02/20/2015 11:12 PM
Just to say Richard Varvil has 2 Lectures coming up:

Tuesday, 14 April Skylon and Sabre - Bringing Space Down to Earth
http://aerosociety.com/Events/Event-List/1934/&

and

Thursday, 21 May The Skylon Spaceplane and Sabre Engine:- progress to date and future prospects’
http://aerosociety.com/Events/Event-List/1640/&

for anyone able to go.

Also on  the 26th of March he's a speaker at this event:

http://www.develop3dlive.com/speakers/

Finally  Alan Bond has a lecture here:
http://www.theiet.org/events/2015/210323.cfm?nxtid=

On the 4th of June called The SKYLON - the future of space transportation
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/20/2015 11:53 PM
I'm interested in what happens assuming they get things mostly right or what they might do if this or that issue turns out to be more difficult  because the alternative is that they go bust and the world is the same as before which is a non-story - why discuss it?
Indeed. Who'd start up a start up expecting to fail?
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We might as well mention that lots of people have built rockets before but this heat exchanger is exceptional so it speaks for their ability to come up with something unheard of and get it done right.
Yes, that's why they built it first.  If they couldn't make this work there was no point in continuing.

The key point is not only that it works but it works as designed which implies they have a deep understanding of how it works.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/20/2015 11:54 PM
The DC-X clearly meets your original point which had no requirement of being in charge or the end system becoming operational. Other projects that meet that criteria plus your newly added one of operational status are the EJ200, Spey and RB211 which Richard Varvill and John Scott Scott worked on, respectively.
For those who don't know these are low and high bypass ratio turbofan engines. The EJ200 powers the Eurofighter Typhoon and is therefor SoA for high T/W ratio engines running over a broad range of thrust and altitude settings.
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When are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE?
 Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does?   
What engine is powering the second stage?
How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.
Indeed. It's one of those ideas that sounds very sensible, until you look at it a bit more closely.
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I can't help feel that rocketry (successfully putting things in orbit since 1957)  is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.
That would be an interesting list.
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Many people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why  should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.
Actually the view amongst some people was that the X33 was extremely complex and risky for its stated purpose. I'd suggest VTOHL SSTO is the most difficult way to do it. It calls for both a T/W of at least 1.1:1 and a strong structure in two axes.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/20/2015 11:55 PM
EDIT: To offer a more substantive response. I don't think the line between science and engineering exists as you think it does. And what scientific breakthroughs have REL done? Their pre-cooler work would be classified by most as an impressive piece of engineering.
Well for those who are having a little trouble understanding the difference.
If you can look up the numbers or the models in a text book or report (and they produce accurate results IE within an acceptable limit of error) that's Engineering.

When you can't, because either the models are wrong or they simply don't exist then you're doing Science.

REL have practiced Science making the frost control system work. The bulk of the rest is expected to be Engineering.

SpaceX built a TSTO ELV. That's Engineering. 11 years in they have now have to do Science to learn
a)Landing high aspect ratio "floppy" structures b)Rocket ignition in a supersonic flow c) Aerodynamics and control over a wide Mach range using grid fins d) Modelling fluid slosh forces on pairs of very large tanks.

Somewhere along the way they've also discovered that their 2nd plan to do 2nd stage recovery can't be made to work without an unacceptable payload loss, which would indicate some (all ?) of their models were in error.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Impaler on 02/21/2015 12:22 AM
What your calling Science I would simply call 'real man's engineering' and looking something up from a book is 'engineering for dummies'.  Iteration in engineering doesn't in my opinion make it a science because science is the creation and testing of theories, engineering is the creation and testing of devices.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: topsphere on 02/21/2015 12:56 AM


Also on  the 26th of March he's a speaker at this event:

http://www.develop3dlive.com/speakers/


This is held at my University. I'll try and go - thanks for the heads up!!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/21/2015 04:33 AM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?

LOX apparently not air. So that's still a bit of question I suppose though to be honest the "Low-NOx" engine test would seem to indicate air use.
http://www.reactionengines.co.uk/sabre_techdevel.html

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/21/2015 04:38 AM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?

LOX apparently not air. So that's still a bit of question I suppose though to be honest the "Low-NOx" engine test would seem to indicate air use.
http://www.reactionengines.co.uk/sabre_techdevel.html

On the page you link to, REL says this about the Low Nox test: "REL has designed and tested a new rocket combustion chamber".  A combustion chamber is an important part of a rocket motor, but it is only a part, not a complete motor.

It's also not clear whether this combustion chamber is full size or a small-scale test.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/21/2015 06:29 AM
When are you proposing to stage this notional TSTO? Inside the atmosphere so you can use a simpler non rocket mode SABRE losing LOX tanks from the first stage or outside still using SABRE?
Are you carrying the second stage internally or externally? If externally how are managing the damage that does to the aerodynamics and thermal protection? If internal how are making the vehicle trimable given the damage that does?   
What engine is powering the second stage?
How does any of that make the development of SABRE cheaper? Either you're proposing using the SABRE design as is, or you're suggesting development of a second engine, on top of SABRE, without a pure rocket mode neither of which can be cheaper for REL as an engine developer than just building SABRE.
Indeed. It's one of those ideas that sounds very sensible, until you look at it a bit more closely.

lkm: Good questions because it IS a "good-idea" depending on the answers. REL has already determined it is NOT a good answer for their purposes and having read their reasoning I'd have to agree. Since I'm currently arguing the "viability" of sub-orbital rendezvous and re-fueling I can't very well say I don't think it's possible :)
Quote

Quote
I can't help feel that rocketry (successfully putting things in orbit since 1957)  is somewhat better understood that Scramjets ( someday soon we'll reach ten minutes cumulative flight time). Who is seriously researching scramjets for anything other than hypersonic cruise? Also please name these other people who think that the development challenges of NASP in 1984 are of comparable difficulty to the challenges of Skylon in 2015.
That would be an interesting list.

lkm: A WHOLE lot better but really "beside-the-point" as the whole attraction of SCramjets is how fast they can go in theory rather than fact in the first place :) The answer to the second is no one as that's about its only use being considered. And lastly I blame confusion between what was "required" of NASP with many of the supposed issues with Skylon. Well that and confusion with issues with the X-33, DC-Y, Roton, etc, etc, etc :)
Quote
Quote
Many people believe that VentureStar wasn't viable, but I don't think anybody believes the X-33 couldn't have flown and gathered useful data. The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project with a similar budget and goals to the X-15. The X-15 wasn't a failure because it had no follow on project so why  should the X-33? When the X-15 first flew it didn't have it's intended engine yet because it wasn't ready, so why should the X-33 not have been given the same leeway? Like I said, there was a change in administration, a desire to cancel and repudiate the projects of the previous one, people obliged.
Actually the view amongst some people was that the X33 was extremely complex and risky for its stated purpose. I'd suggest VTOHL SSTO is the most difficult way to do it. It calls for both a T/W of at least 1.1:1 and a strong structure in two axes.

lkm: I'd be one of the ones who would argue that no, the X-33 would in fact NOT have been useful since it could not in fact met its flight related goals. That was in fact a major issue with the program as LM kept dropping the "goals" because the design was incapable of meeting the original series. Couple that with the development issues and cost over-runs it was pretty inevitable IMHO. Even if there had been no change in the political landscape the problems with the X-33 program overall would have ended up the same. Similarly I was never convinced that the VentureStar was going to happen even IF the X-33 was able to fly. LM had to constantly "update" the design to take into account problems they were running into with the X-33 AND there were inherent issues with the design that LM really should have known about given their background. (Come on, the design could not in fact "fly" because it was too tail heavy and no one in an aircraft company figured this out till AFTER? :) )

Comparison of the X-33 to the X-15 isn't really applicable. The "X-33" was an "X" vehicle only due to it supposedly being a technology demonstrator/development program which in fact it didn't do. The X-15 on the other hand was a test aircraft along the line of progression to higher speeds and altitudes. I don't actually consider the X-33, (or X-34, X-37, etc) to be actual "X-Planes" but this is pretty much OT for this thread.

JS19: While technically accurate (VTHL design) we HAVE done this before and its a pretty straight forward engineering problem. Has issue but then again so will designing and building what amounts to a hypersonic zeppelin :)

Its always a plus if you can design a vehicle to only handle the "exact" loads it needs and not a bit more. (Henry Ford logic/economics at work :) However that "logic/economics" leads to surviving a crash only to be killed when the "minimum" roof of the car collapse on you :) ) And since every ounce counts/costs going into space...

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Dalhousie on 02/21/2015 06:33 AM

The two biggest hurdles technology wise were the heat exchanger and the rocket motor both of which have been demonstrated.

The rest of your post was reasonable, but this I must inquire about:
When was the rocket motor demonstrated? Did I miss that?

LOX apparently not air. So that's still a bit of question I suppose though to be honest the "Low-NOx" engine test would seem to indicate air use.
http://www.reactionengines.co.uk/sabre_techdevel.html

Randy

That page list contra-rotating turbines, Sabre combustion chamber, Sabre nozzles, low NOx engines, and Sabre intakes, so REL have a lot more than "just" a "cooler".
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/21/2015 08:32 AM
The X-33 wasn't VentureStar, VentureStar was a powerpoint, X-33 was an active x-plane project

But when someone makes a comment like that about the Skylon vehicle vs REL's actual development, they get their heads bitten off.

Aside: One of the reasons the X-33 failed was the belief by some senior people that saying "there's no showstoppers" meant that you could treat development as a fait accompli. Therefore... Well, I recall (no refs, sorry, it was awhile ago) a program manager testifying before Congress that the program would be "worthless" (I think he even used that word) if it didn't launch with every piece of technology on his wish-list (mainly the composite hydrogen tank). So when the development of key pieces of technology stalled, what outcome would you expect?

I similarly worry that REL's people are so fixed on their end goal that they can't see alternative approaches. A TSTO is dismissed because it isn't as "economical" as their SSTO... which they expect will cost $10b to develop...

(I worry the same thing about Musk. But his development philosophy results in useful, low cost vehicles at each stage, even if his end goal fails.)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/21/2015 08:41 AM
What would people think of separating this thread into two threads: Skylon Updates and Skylon Discussion?  There's been a lot of discussion in the Skylon threads, and not everyone who is interested in hearing about news from Skylon has the time or inclination to follow all the discussion.

Agreed. But I'd suggest three.

- REL development news. Info only (Plus the usual RFI questions. "Does anyone know if..." "Are they going to...")

[edit: Ah, what the hell, Reaction Engines Ltd (REL) news and information (http://forum.nasaspaceflight.com/index.php?topic=36851.0) )

- Skylon general discussion. Everything else... except...

- Alternative uses of REL tech. A2/Scimitar discussion. General application to aviation. Alternative applications to spacecraft. Alternative paths to Skylon. (The discussion you were trying to start, which got bogged down in... {waves hand} ...this.)


when the space shuttle idea was proffered, did people say 'what's wrong with normal rockets?, we know how to do normal rockets'  were there naysayers arguing for incremental steps?

I would suspect there were a lot of "naysayers" and "skeptics" arguing for a more incremental development path. Not because they hated the idea, or wished ill upon it, but because the Shuttle required too many new technologies all to work exactly as predicted. Any problems would turn the Shuttle into a fragile expensive system which would fail in its goal of making access to space affordable and routine...

And I know in the '80s a lot of us space advocates used the lack of incremental development in the Shuttle program in the '70s as an example of "what not to do". And we despaired as program after program (Freedom, NASP, VentureStar, even Delta Clipper to a degree(*), and almost all of the big science missions) repeated the same mistake with the same or similar results. And now, of course, SLS and Orion doing the same thing. "They say the definition of madness is doing the same thing over and over and expecting a different result."

It's this pattern that we see being repeated in Skylon, and this outcome that I fear for REL.

(* While DC-X was a lovely cheap research program, next "step" was meant to be a full sized SSTO demonstrator, DC-Y. Ick.)

Do I then assume that you deride the various "Fully-reusable TSTO is a done deal" SpaceX fans the same way?

Yes. Often.

I also deride those who build a strawman out of a handful of the most naive enthusiasts into some general behaviour of "SpaceX Fans".

Quote
And yes Skylon is the latest in a long line of "promising" SSTO vehicle but I'd point out that it in fact is much close to, and much easier to implement than most where and does not (at this point) really need as significant technologies as most of the previous concepts did.

Out of curiosity, can you think of a single one of those previous designs whose advocates didn't say exactly the same thing about their design?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 02/21/2015 09:42 AM


And from what I saw over the last 25 years, that's part of the reason it's taken so long for Bond's ideas to receive backing. If you're an investor (or administrator) in aerospace/aviation and this comes across your desk; a report that's actually about some guy who thinks he's solved the pre-cooler icing problem, but if you saw a picture of Skylon and pages of detail on the vehicle, payloads and missions, would you even read the report? Would you wade through the rest to even get to the two paragraphs on Bond's actual pre-cooler design? Because Skylon hit the quadrella of aerospace "alarm bells": a tiny unknown company proposing a radical vehicle design, plus it's an SSTO, plus it uses air-breathing jet/rocket hybrid engines, plus it's all based (with no margins) around their own new unproven technology proposal.

OTOH, you're in aerospace and a report crosses your desk about a small start-up that thinks it has solved the pre-cooler icing program. They point out that if their idea works, it could make high-speed turbojet engines more efficient and effective. Oh sure, they speculate - just as an aside, making it clear that they are just speculating - that the idea could even be useful for future space vehicles. And that's it, the report is about their pre-cooler idea, nothing else.

that's some back to front thinking you have going on there Paul451.   REL need heavy investment.  Investors need to be wooed.  showing them what the ultimate goal of their investment is is logical.   telling them that you have done no work on plausible applications of the pre-cooler breakthrough and then asking for investment is nuts.   REL did exactly the right thing in commissioning business case reviews and framing end use scenarios.  if you're after investment, this is what you do.

about wooing investors with the promise of making high-speed turbojet engines more efficient and effective.  why would they?   REL's goal is not to make high-speed turbojet engines more efficient and effective.   we know what their ultimate goal is and they are entitled have it. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 02/21/2015 09:56 AM
Out of curiosity, can you think of a single one of those previous designs whose advocates didn't say exactly the same thing about their design?

SSTO was always about making up negative margins with handwavy breakthroughs.  X-33 was actually sold on that basis.  Before Skylon, what SSTO concept had double-digit mass margins after decades of iterative design and component fabrication/testing? What SSTO concept could have absorbed a 10% Isp hit (and used up its structural margins) without failing to make orbit?  REL has been busy making sure nothing on the vehicle is below TRL 4 before committing to so much as an engine development program, and while the resulting design is unconventional it does not seem to require any breakthroughs.

Paul451, I understand you haven't really been around for the technical discussions, but it gets really old having newcomers assume proponents of the idea are handwaving in a vacuum.  Skylon is nothing like X-30.

Lars_J, you have been around long enough and should know better.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/21/2015 10:27 AM
that's some back to front thinking you have going on there Paul451.   REL need heavy investment.  Investors need to be wooed.  showing them what the ultimate goal of their investment is is logical.

And yet for over 20 years it didn't work. Only now are they picking up some actual revenue, and not for Skylon but for a hypersonic passenger plane study.

"Step 1: Get £10 billion investment..."

Umm, no.

Quote from: banjo
about wooing investors with the promise of making high-speed turbojet engines more efficient and effective.  why would they?

Because high speed military aircraft are a lucrative market. And a company that develops the next big thing in aircraft engines will end up with much spare cash for their more speculative R&D.

And I suspect they'll end up somewhere like that anyway. Only it will take a demonstration of the full SABRE engine to get potential customers to ignore Skylon long enough to say, "Oh hey, that's actually useful technology". Something REL may have achieved 15-20 years sooner had they not publicly fixated on Skylon.

Paul451, I understand you haven't really been around

I've just started posting here, but I've been watching REL since they started, and HOTOL before it. And I've been "around" these discussions long before NSF existed. Your patronising is unnecessary.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/21/2015 10:41 AM
that's some back to front thinking you have going on there Paul451.   REL need heavy investment.  Investors need to be wooed.  showing them what the ultimate goal of their investment is is logical.

And yet for over 20 years it didn't work. Only now are they picking up some actual revenue, and not for Skylon but for a hypersonic passenger plane study.

I thought their money is from a 60 million pound government investment for developing SABRE and private capital.  I mean I know they were part of LAPCAT but that seems like a minor part of what funding they managed to get.  Why are you leaving out the major sources?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/21/2015 10:44 AM
What your calling Science I would simply call 'real man's engineering' and looking something up from a book is 'engineering for dummies'.  Iteration in engineering doesn't in my opinion
make it a science because science is the creation and testing of theories, engineering is the creation and testing of devices.
Then you'll be pleased to know that SpaceX have been doing plenty of 'real man's engineering'   :)
 
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make it a science because science is the creation and testing of theories,
SpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible.

That's when  you start doing Science.

BTW if you look at the book cases of successful real engineers in any field you'll find an extensive back catalogue of stuff they can dip into when a new problem arrives and say "Ah, this looks like something in <textbook name/journal article/web page I copied> " The skill is knowing how to "flex" what's there into what's wanted.

They are called "inspection" or "cookbook" methods but a lot of the time they get the job done.

Trouble is what SpaceX want to do is not in any "cookbook"  :(

That's when you start getting into Applied Physics and hacking the source code on your CFD systems.

Unfortunately that's when development schedules go out the window and you may have to scrap all your previous work. You think you can get away with something (turning an ELV into an RLV at a certain size while still having a large payload say) and you can't.

To make this more Skylon centric look at what Skylon does not do.  It does not
1) Take off vertically. So it's engine T/W  ratio can be worse and T/O Thrust much lower than GTOW. That's not the whole story of course. It's that it then turns the atmosphere around it into IIRC about 100 tonnes of extra propellant (80% of it is more strictly "reaction mass" but it all helps).

2) No main engine re ignition in an oncoming (albeit tenuous) hypersonic airstream.

3) No engines forward re-entry. I can't imagine the CFD days (weeks?)  SpaceX took for them to be comfortable doing that. In particular the heat load on the most forward bell of the most forward engine (it'll be slightly below the horizon of local airflow) That's a combined aero/thermo/chemical load simulation problem. It's like the little patch on the Apollo heat shield. The temperature fall off outside it is huge but that's because that patch will run hot

4) No direct exposure of main propellant tanks to airflow. This side steps heating and bending forces which will try the F9 1st stage to a "face on" directly into the flow have to be resisted. It also side steps questions about wheather the LOX vaporises and the Merlins need to run on GO2/RP1 instead.

5) No large lumps of propellants sloshing round in the main tanks, which are vented.  Keeping in mind an F9 stage is not "end on" to the stream so the deceleration forces smear the propellants onto the wall facing the airflow at an angle. Hard enough  (like a guy charging a door) to make the stage flips over? What's the safe loading range to avoid that? Is it enough to land on? Who knows.

6) No ablatives (of unknown erosion rates) to replace.

Some of these are Science problems with no existing methods to solve them and some of them are situations that have no precedence, so no one has got constants for them for others to use.

And those are the obvious ones from a layman's PoV.  :(

Those forces interact in lots of interesting ways to give new force vectors (which will of course change over the course of the flight).

SABRE/Skylon "solves" these problems by not having to deal with them. However it has a set of problems of its own to solve, which would be on topic for this thread. The difference is REL don't need flights to collect the basic data to start to build the models (not the vehicle, the models) in the first place.

So if you're a CFD programmer or an Applied Physicist this makes SpaceX possibly the most exciting place on the planet for you to work right now.  :)

And you will work.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/21/2015 11:53 AM
I thought their money is from a 60 million pound government investment [...] Why are you leaving out the major sources?

Nothing sinister about it. It was an arbitrary decision to draw a distinction between the UK Govt giving them bare-minimum funding to keep REL viable, to keep from losing technology to someone else (even if they didn't believe in the technology enough to properly fund it), and someone completely independently saying "hey, you guys have mad skills, care to do some work for us?" The latter struck me as more significant, even if it garners fewer dollars pounds euros.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/21/2015 02:48 PM
that's some back to front thinking you have going on there Paul451.   REL need heavy investment.  Investors need to be wooed.  showing them what the ultimate goal of their investment is is logical.

And yet for over 20 years it didn't work. Only now are they picking up some actual revenue, and not for Skylon but for a hypersonic passenger plane study.

I thought their money is from a 60 million pound government investment [...] Why are you leaving out the major sources?

Nothing sinister about it. It was an arbitrary decision to draw a distinction between the UK Govt giving them bare-minimum funding to keep REL viable, to keep from losing technology to someone else (even if they didn't believe in the technology enough to properly fund it), and someone completely independently saying "hey, you guys have mad skills, care to do some work for us?" The latter struck me as more significant, even if it garners fewer dollars pounds euros.

I'm sorry but I read it as "they have no money other than for a hypersonic study" and I don't see how anyone could possibly read it otherwise.  Now it twists into another comment which is also wrong because they always have had private support and 60m pounds is the lesser part of it from what we know of their plans for developing the engine i.e. what they said they'd need versus what we know for sure they have.

Are we expected to have detailed information about their private funding? I didn't think private companies usually handed that kind of thing out to everyone.

It is obvious, however, that to get this far they certainly have impressed people who certainly have put a very large amount of money in.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Impaler on 02/21/2015 06:35 PM

SpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible.

That's when  you start doing Science.

THIS is the kind of comment that destroys your credibility.   As Lars-J said earlier is smacks of "Denigrating the hard work by done by people trying for the same goal but by different means." 

It has been pointed out repeatedly to you that SpaceX is not PURSUING full reusability for F9 because they have decided to focus on the followup vehicle which they DO intend to make fully-reusable.  They have said this is a decision driven by market volume and development resource, NOT one forced on them by hitting technological barriers.

But you have been repeatedly portraying this a technical failure on SpaceX's part and further more that this failure invalidates the vertical take-off, vertical landing paradigm, leaving your preferred Horizontal arrangement the 'only' viable solution.  And you blatantly ignore that they are STILL WORKING on the goal, which puts them in the same race as REL, but miles ahead, while you try to treat them as if they have dropped out.

And no this is not Science, it is ALL engineering.  Science is creating the rocket-equation, Bernoulli's principle and all the other THEORIES that let us know how the world behaves.  SpaceX nor any other Airo-space company dose science, they engineer vehicles using well established theories.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Robotbeat on 02/21/2015 06:48 PM
Thank you again, Impaler! Can I subscribe to your newsletter?
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 02/21/2015 08:39 PM

SpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible.

That's when  you start doing Science.

THIS is the kind of comment that destroys your credibility.   As Lars-J said earlier is smacks of "Denigrating the hard work by done by people trying for the same goal but by different means." 

It has been pointed out repeatedly to you that SpaceX is not PURSUING full reusability for F9 because they have decided to focus on the followup vehicle which they DO intend to make fully-reusable.  They have said this is a decision driven by market volume and development resource, NOT one forced on them by hitting technological barriers.

But you have been repeatedly portraying this a technical failure on SpaceX's part and further more that this failure invalidates the vertical take-off, vertical landing paradigm, leaving your preferred Horizontal arrangement the 'only' viable solution.  And you blatantly ignore that they are STILL WORKING on the goal, which puts them in the same race as REL, but miles ahead, while you try to treat them as if they have dropped out.

And no this is not Science, it is ALL engineering.  Science is creating the rocket-equation, Bernoulli's principle and all the other THEORIES that let us know how the world behaves.  SpaceX nor any other Airo-space company dose science, they engineer vehicles using well established theories.

I kind of agree with what you said other than please do not just dismiss what REL has achieved so far by the glib sentence of saying that Space X is miles ahead. Especially as this is not some kind of race as I don't even regard Space X & REL as being in the same business.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ChrisWilson68 on 02/21/2015 08:43 PM
I kind of agree with what you said other than please do not just dismiss what REL has achieved so far by the glib sentence of saying that Space X is miles ahead.

To me, saying SpaceX is miles ahead doesn't dismiss what REL has achieved.  SpaceX was once far behind ULA, but held promise.  Being behind doesn't mean they won't eventually end up in front.  It just means they have a longer journey ahead and there is more uncertainty because of that.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 02/21/2015 09:16 PM
That's fine, but this engine company is making projections about the performance and economic viability of the complete system, including engines and airframe.

Don't they have to? Is it not necessary at all times to make such projections and keep updating them as new information is learned?

There'd be no shame in their saying "we don't know yet".

There no shame in that but say "we don't know yet", tend to put off investors and especially investors who will put money into such early projects, they want to be sold a dream a visions, they don't want ifs and buts.


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Personally I think the greatest threat to Skylon development will be a failure of an airframer to commit to it. I think REL may find that despite developing an engine that works well and engenders a lot of interest in the end there may be a general reticence to throw in with another companies grand scheme and disrupt their own planning among the likely consortium partners. I could see REL being bought by RR as a part of an attempt at forming a successful consortium only to end being used to get some lucrative US hypersonics research money.
This is my biggest fear as well, that REL squash under a barrage internal politics from any consortium.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Dalhousie on 02/21/2015 09:54 PM

SpaceX's failure to deliver a fully reusable F9 strongly suggest that the current theories, and the models derived from them have flaws in them that mean going from their very public video to actual hardware was impossible.

That's when  you start doing Science.

THIS is the kind of comment that destroys your credibility.   As Lars-J said earlier is smacks of "Denigrating the hard work by done by people trying for the same goal but by different means." 

It has been pointed out repeatedly to you that SpaceX is not PURSUING full reusability for F9 because they have decided to focus on the followup vehicle which they DO intend to make fully-reusable.  They have said this is a decision driven by market volume and development resource, NOT one forced on them by hitting technological barriers.

But you have been repeatedly portraying this a technical failure on SpaceX's part and further more that this failure invalidates the vertical take-off, vertical landing paradigm, leaving your preferred Horizontal arrangement the 'only' viable solution.  And you blatantly ignore that they are STILL WORKING on the goal, which puts them in the same race as REL, but miles ahead, while you try to treat them as if they have dropped out.

And no this is not Science, it is ALL engineering.  Science is creating the rocket-equation, Bernoulli's principle and all the other THEORIES that let us know how the world behaves.  SpaceX nor any other Airo-space company dose science, they engineer vehicles using well established theories.

I think you are completing misreading John Smith 19's points.  As I read it, he is pointing out that there is a difference between applying well known existing engineering principles to a particular problem (engineering), and developing new processes that require new and deeper understand of fundamental processes (science). The distinction isn't clear cut, but it is there.

Nor is it correct to say that John Smith 19 has consistently denigrated SpaceX.  He has not as far as I can see. He has merely pointed out that SpaceX and REL are approaching things differently and have different goals.  As others have said, it isn't a race.


Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/21/2015 10:43 PM
Question: Do we think we know enough about SABRE to state categorically that it only works when integrated with a Skylon type of airframe? Are there no other possibilities? Like, say, fitting it to a smaller vehicle that has aerodynamics/wing area suited for landing, but that's air-launched from the StratoLaunch carrier aircraft?

This is just a (probably crazy) example. If it could be useful in other configurations, what are they?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 02/21/2015 11:27 PM
"Step 1: Get £10 billion investment..."

Umm, no.

Background:  HOTOL was a high-resolution design study resulting in an airbreathing SSTO that looked marginally feasible but not economically interesting, powered by deeply precooled air turborocket engines (Rolls-Royce RB545) with a solution to the icing problem incorporated (no, it's not the same solution SABRE uses).  After the study was essentially completed and the involved parties lost interest, the engine tech got classified, with no indication (even now, after a quarter of a century) of any actual intent to use it.  So to circumvent the classified patents, Bond & co. came up with a modified engine cycle that actually turned out to be superior to the RB545.  They also rethought the airframe concept to eliminate one of the biggest problems with the original design.  It is at this point that REL was formed.

Step 1:  solicit small grants and investments and use them to buy down risk, partnering with industry and academia as appropriate.

Step 2:  land enough investment (millions) to carry out a comprehensive technology demonstration program with the goal of raising SABRE/Skylon's component TRL floor to 4, again seeking out external expertise as appropriate.  This program started in 2009, and one of the more prominent results was the flight-weight precooler hardware tested in 2012.
Step 2a:  simultaneous to Step 2, produce a high-fidelity vehicle design (Skylon D) to anchor the engine design, so as to avoid having to go back and redesign the engine once the vehicle takes shape.

Step 3:  leverage the results of the tech demonstration program to attract sufficient cash (hundreds of millions) to start intensive engine development.  This has apparently happened; the £60M government investment is not a keepalive fund but rather a pump primer for a large effort.  REL has been expanding significantly, and has apparently secured enough funding to forgo a subscale demonstrator (SCEPTRE) in favour of a full-size prototype SABRE.

Step 4:  With a full-size prototype SABRE showing good results on the test stand, get the interested parties to commit to full-scale vehicle development, which may well involve subscale and/or suborbital demonstrator vehicles.

At no point does REL itself ask anyone for a £10 billion investment.

...

As you can see, it is not accurate to claim REL is not doing "incremental development".  It just looks a bit different, because what they're trying to do is different.  It's not REL's fault there doesn't seem to be a commercially useful way to half-ass the idea (leaving aside peripheral stuff like the Valkyrie sounding rocket)...

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Because high speed military aircraft are a lucrative market. And a company that develops the next big thing in aircraft engines will end up with much spare cash for their more speculative R&D.

The precooler tech is tied to hydrogen fuel.  This immediately makes it useless on any existing airframe, creating a very high entry barrier, and greatly complicates the operation of any new vehicle using it.  The difficulties of hypersonic cruise only make this situation worse.  (Remember, existing engine tech is perfectly capable of propelling an aircraft faster than any currently-operational aircraft actually goes.)  Space launch is about the only market with a clear near-term use for the technology.

The U.S. military hates hydrogen, probably because logistics are so important to them.  They don't even like LOX.  I don't know why the USAF is interested in SABRE, but I'd be willing to bet it's not for a fighter.

Non-aerospace applications of the precooler technology are possible, but they will have to wait until the manufacturing process is refined and the price comes down...

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I've just started posting here, but I've been watching REL since they started, and HOTOL before it. And I've been "around" these discussions long before NSF existed.

Yet you don't seem to know much about it, and a lot of what you think you know seems to be wrong.

Science is creating the rocket-equation

No.  The rocket equation could be derived in short order by any reasonably competent engineer who actually bothered to think about the problem.  Tsiolkovsky was merely one of the first people to do so (not the very first; it shows up in earlier sources).  The "science" in the rocket equation is all Newton.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 02/21/2015 11:46 PM
I think USAF is interested in SABRE simply because they hate the thought of anyone else having something that outclass anything they are working on at least publicly.

 The last thing they want is the Chinese showing up in 20 years time having developed their own Sabre/Scimitar  engine powered aircraft either independently or stolen from REL and USAF not having any answers . This is good news for REL assuming they can figure out how to get hold of USAF money without to many strings being attach  ;).

Plus with hydrogen being use in cars and in buses and everyday civilian lives there probably some in USAF that thinks it time for their hatred of hydrogen fuel engines to come to an end. Especially as their scramjets projects seems to crash just as often as they manage to fly.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 02/21/2015 11:58 PM
Do we think we know enough about SABRE to state categorically that it only works when integrated with a Skylon type of airframe?

SABRE isn't tightly integrated with the airframe like a scramjet is.  All it strictly requires is a source of liquid hydrogen.

The only airframe-integration feature I can think of is the nacelle camber, which is due to the difference between the desired angle of attack and the desired angle of thrust.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Chris Bergin on 02/22/2015 01:30 AM
Ok guys, this thread is a problem as not a day goes by without report to mods coming in, mainly due to off topic and a few people getting rowdy with each other.

All posts from this point onwards will be on topic and civil.

No excuses.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/22/2015 03:37 AM
Do we think we know enough about SABRE to state categorically that it only works when integrated with a Skylon type of airframe?

SABRE isn't tightly integrated with the airframe like a scramjet is.  All it strictly requires is a source of liquid hydrogen.

The only airframe-integration feature I can think of is the nacelle camber, which is due to the difference between the desired angle of attack and the desired angle of thrust.

That's my understanding too. So what other airframe configurations might make sense? And are there any that are less ambitious/costly than the Skylon vehicle as currently conceived?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/22/2015 11:01 AM
JS19: While technically accurate (VTHL design) we HAVE done this before and its a pretty straight forward engineering problem. Has issue but then again so will designing and building what amounts to a hypersonic zeppelin :)
True. But it never would have worked without those monster RATO packs and the humungous drop tank. :)
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Its always a plus if you can design a vehicle to only handle the "exact" loads it needs and not a bit more. (Henry Ford logic/economics at work :) However that "logic/economics" leads to surviving a crash only to be killed when the "minimum" roof of the car collapse on you :) ) And since every ounce counts/costs going into space...
Sometimes referred to as the "one horse shay" paradign.  :)

I think you are completing misreading John Smith 19's points.  As I read it, he is pointing out that there is a difference between applying well known existing engineering principles to a particular problem (engineering), and developing new processes that require new and deeper understand of fundamental processes (science). The distinction isn't clear cut, but it is there.

Nor is it correct to say that John Smith 19 has consistently denigrated SpaceX.  He has not as far as I can see. He has merely pointed out that SpaceX and REL are approaching things differently and have different goals.  As others have said, it isn't a race.
Your are correct in all points. There was much more I'd written, but it's OT and I'd like to bring it back to SABRE/Skylon.  :(

That's my understanding too. So what other airframe configurations might make sense? And are there any that are less ambitious/costly than the Skylon vehicle as currently conceived?
That's tricky without understanding why they developed this configuration.

The problem is twofold.

The Centre of Pressure shifts a lot over an airframe going from 0-M23-0

The Centre of Gravity shifts a lot because propellant is a much bigger fraction of the vehicle weight than in an aircraft.

A key  problem with HOTOL was with the engines at the back as the tanks emptied you had very little mass to stop the body "flipping" upward, so you needed a huge set of control surfaces (and their actuators) to keep the nose at the right angle. IIRC Bond said "2000 tonne metres" IE a small ship on those control surfaces.

Terrestrial aircraft can get away with the engines at the back (Trident DC-10, Caravelle) because of a) A relatively empty fuselage b) "Wet" wings and c) More "dead" weight in the vehicle to counter balance the weight of the engines in the back.

There are various configurations you could build a SABRE (ideally a pair of SABRES) into but they all face 2 problems.

High pressure LH2 engines (or rather their turbo pumps) scale down badly so you'd want to use full size SABRE engines.

It's not what your sub scale prototype can demonstrate it's what it cannot. Those things can only be demonstrated in the full size vehicle, IE a Skylon. So you're building a Skylon (actually REL are planning 2 flight test Skylons) and  this demonstrator/proof-of-concept/whatever vehicle, so your overall budget goes up.  :(

My instinct is the simplest way to go is with full size SABRES propelling a reduced scale Skylon airframe with narrower, shorter fuselage, no payload bay (and no payload  :( ) and much lower propellant load.

If such a vehicle matches a full sized Skylons aerodynamics and mass properties then its results should be transferable directly to the full size Skylon, shortening the flight programme of the full sized vehicles to lower the overall development budget and "squaring the circle" of using 3 vehicles instead of 2 but still working out cheaper.   :)

IRL my instinct is that being able to scale a design to that way while preserving all the main features is a very big "if" indeed. I suspect the range over which you could scale the airframe while a)Using full size SABRES and b)keeping the various mass properties and aerodynamic coefficients matching the full size vehicle is very limited.

The question is not "can you scale it down" but "do you save so much on the test budget it's worth doing" ?

I suspect the answer comes out "Build a full size Skylon with full size engines and no payload bay (there is room, but only enough is installed to preserve necessary structural stiffness) and smaller tanks," and I think REL have a better idea of the answer, but I don't know what it is.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/22/2015 08:15 PM
I suspect the answer comes out "Build a full size Skylon with full size engines and no payload bay (there is room, but only enough is installed to preserve necessary structural stiffness) and smaller tanks," and I think REL have a better idea of the answer, but I don't know what it is.  :(

Hmmm, you may be right. At first blush, building a half-scale Skylon seems less ambitious, and so more likely to happen, i.e. receive funding. Skylon as currently described is soooo huge that size alone makes the whole project appear impractical. BUT once you've committed to the design of a few square meters of aeroshell/tankage, then manufacturing lots and lots of square meters is not that much more difficult/costly than half as much. This is probably made easier because Skylon has such a regular/recurring shape.

And as you say, smaller and lighter internal tanks give you lots of margin to play with on the test vehicle, and lower loads... And unlike other spacecraft you have the option of loading a small amount of LH2 (and no O2) which again lowers weight and loads.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: space_britannia on 02/23/2015 11:36 PM

The U.S. military hates hydrogen, probably because logistics are so important to them.  They don't even like LOX.  I don't know why the USAF is interested in SABRE, but I'd be willing to bet it's not for a fighter.


I wouldn't be surprised if it's for SUSTAIN ("Marines in Space") - see http://www.popsci.com/military-aviation-space/article/2006-12/semper-fly-marines-space
http://www.popularmechanics.com/military/a5539/plans-for-marines-in-space/
http://www.defenseindustrydaily.com/hypersonic-rocketplane-program-inches-along-0194/

Those stories talk about a 2-stage concept however, and whether with scramjets or sabre (hydrogen fuel issue again), that's going to be one very expensive ride to ditch in the middle of a conflict zone
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 02/24/2015 02:35 AM
Do we think we know enough about SABRE to state categorically that it only works when integrated with a Skylon type of airframe?

SABRE isn't tightly integrated with the airframe like a scramjet is.  All it strictly requires is a source of liquid hydrogen.

The only airframe-integration feature I can think of is the nacelle camber, which is due to the difference between the desired angle of attack and the desired angle of thrust.

That's my understanding too. So what other airframe configurations might make sense? And are there any that are less ambitious/costly than the Skylon vehicle as currently conceived?

Probably not , considering it's a tube with wings and you need spheres or tubes ideally for the tankage. Tube with wings is well known, and has low frontal area.

But, as a thought exercise, a squished pancake shape might work. Internally, you have three rows of cylindrical spaces, center with payload bay and fore/aft LOx tanks flanked by full length LH2 tanks. Fit the SABRE equipment near the mid-fuselage edge of the pancake, with a 2D ramp inlet on its side, and exhaust is half an aerospike ramp on its side. That largely preserves the basic Skylon layout (which does well to deal with cg changes), but frontal area drag unfortunately goes up which goes against the partial cruise accelerator profile. The only advantage to that layout is if you were doing something kinky like receiving external heating AKA Laser Skylon, as you could have a better receiver area.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/24/2015 03:50 AM
I don't know why the USAF is interested in SABRE, but I'd be willing to bet it's not for a fighter.
I wouldn't be surprised if it's for SUSTAIN ("Marines in Space")

[Such speculation may be off-topic, I'm not sure how strictly to Skylon Chris wants the thread to run.]

There are other applications of the pre-cooler. Improving flight range via greater engine efficiency; higher speed from existing engines without overheating the engine; even reducing the IR signature of engine exhaust (which wasn't one I'd previously considered.) Plus you've got the ongoing interest in fast-turnaround small-sat launchers, a la DARPA XS-1.

(For other Services, you've got improved operations of any large turbine-based engine (increasingly common in non-nuclear ships.))
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/24/2015 06:15 AM
The projected first flight of Skylon has always been far enough into the future, and the schedule burdened with sufficient unknowns that you can forgive critics for doubting it will ever see the light of day. But it occurred to me that if (big if) investors were to suddenly want to make it happen ASAP we could conceivably see it in the first half of the 2020s rather than the second for a couple of reasons.

Firstly, as REL have rightly pointed out before, the full engine cycle can be thoroughly tested on the ground. This is hugely beneficial, and additional cash would allow more extensive testing to be concluded sooner.

Secondly, the airframe could be prototyped/tested in parallel with the engine or beforehand. No-one's talks about doing this because if the SCEPTRE tests show major problems you won't need the airframe. However, if someone wanted to I suspect you could do subsonic testing of the airframe shape by placing turbojets in the nacelles. Perhaps you could then go supersonic by adding rockets and closing (and testing) the nacelles cones.

Don't ask me where the money and desire to do this will come from, but it's one more reminder that Skylon's problems have more to do with politics and economics than technology or necessarily long dev schedule.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/24/2015 09:09 AM
I wouldn't be surprised if it's for SUSTAIN ("Marines in Space") - see http://www.popsci.com/military-aviation-space/article/2006-12/semper-fly-marines-space
http://www.popularmechanics.com/military/a5539/plans-for-marines-in-space/
http://www.defenseindustrydaily.com/hypersonic-rocketplane-program-inches-along-0194/

Those stories talk about a 2-stage concept however, and whether with scramjets or sabre (hydrogen fuel issue again), that's going to be one very expensive ride to ditch in the middle of a conflict zone
Welcome to the forum and the thread.

Firstly "Force projection" through space has a long history. Bono and Gatlands "Frontiers of Space" looked at delivering 100s of Marines at a time by "ballistic transport" IE near SSTO sub orbital vehicles. That was around 1969.

Reading the links you listed in detail they read like sales pitches for yet another SCRamjet research programme.  :(

AFAIK the CRADA is for SABRE engine cycle only. So the USAFRL can run the numbers (the pressures, temperatures and flows at various parts of the system) through their design codes and satisfy themselves that it it will produce the output they expect.

I do hope they pay attention to what the condition of the inlet air is as the Mojave desert is a little different from Kourou.  :)

It would seem that some in the USAF are starting to think the unthinkable.

"What if we do a vehicle without developing an SCRamjet in it as it does not need an SCRamjet?"

But Skylon is not designed as some kind of assault transport. The problem is you need to secure a landing strip before it arrives with reinforcements (although without LH2 and LO2 on board it can land on quite a poor runway), a chicken and egg situation.  :(

However "responsive" access to space IE launching payloads to monitor or assist in developing theaters of operations in days not years, has been an interest of some parts of the DoD for a long time, XS1 being the latest attempt (although that's gone rather quiet of late).

SABRE/Skylon can deliver such a capability.
BUT once you've committed to the design of a few square meters of aeroshell/tankage, then manufacturing lots and lots of square meters is not that much more difficult/costly than half as much. This is probably made easier because Skylon has such a regular/recurring shape.
Making things smaller in prototype has some history in aerospace to a point, but only to a point. This is why REL were looking for IIRC £250m then worked out that for £15m more they could a full size engine, so why not?

In mfg the hardware you have access to always has some limits on how big a thing you can make on it. For 1 offs you can probably find a way to exceed those limits (again, to a point ) but for repeat production you're looking at a step change in costs as now you've got to buy/build a whole new suite of machines to handle that.

NASA can do a 10m tank, but push it to 15m or 20m? I think you'd have to tear out the current hardware and replace it wholesale.  Obviously it's a question of what you're funded to and how far you think a concept can go when you're planning  your factory.
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And as you say, smaller and lighter internal tanks give you lots of margin to play with on the test vehicle, and lower loads... And unlike other spacecraft you have the option of loading a small amount of LH2 (and no O2) which again lowers weight and loads.
True.

It comes down to a very tricky problem. Can I find a cheaper way to do part of the programe (easing my fund raising problem) that does not mean I have to buy extra hardware (or tests) later, so increasing the overall cost, the problem I'm trying to avoid.

Probably not , considering it's a tube with wings and you need spheres or tubes ideally for the tankage. Tube with wings is well known, and has low frontal area.
Exactly.  Keep in mind that a "tube with wings" has already demonstrated successful reentry about 130 times
Quote
But, as a thought exercise, a squished pancake shape might work. Internally, you have three rows of cylindrical spaces, center with payload bay and fore/aft LOx tanks flanked by full length LH2 tanks. Fit the SABRE equipment near the mid-fuselage edge of the pancake, with a 2D ramp inlet on its side, and exhaust is half an aerospike ramp on its side. That largely preserves the basic Skylon layout (which does well to deal with cg changes), but frontal area drag unfortunately goes up which goes against the partial cruise accelerator profile. The only advantage to that layout is if you were doing something kinky like receiving external heating AKA Laser Skylon, as you could have a better receiver area.
If cost is the issue for a prototype you'd scrap the payload bay. This layout might handle the Cp/Cg shifts well enough to do the whole flight trajectory.

But look what you've lost  :(

This design is reminiscent of the "pye wacket" missile concept for an armed SR71 but AFAIK it has no flight history in other vehicles you can call on to refine the design.

Then you're suggesting some altitude compensation by expansion against the underside, which raises the temperature quite a bit.

And once you've got it working how do you translate the measurement of the flight programme to that of a Skylon?

It's a tough problem.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 02/24/2015 09:38 AM
true that skylon could not land itself to deliver troops in a contested combat zone- it is also too expensive for this.

But may it could
1) deliver into space a specifically designed lander and its squad
2) deliver the specifically designed lander into space, and bring the squad there when it is needed.

in the option 1) it would work as a sort of first stage
in the option 2) it would work as a transport vehicle of its own. however I guess the timeframe for going to LEO, transit the squad in the vehicle stationning there,  and down again, isn't any close to "two hours". Although it would still solve the issue of transportation above unfriendly territory.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/24/2015 10:13 AM
2) deliver the specifically designed lander into space, and bring the squad there when it is needed.

The lander-in-orbit would be limited to a single window in a single orbital plane, making it incompatible with the goal of a suborbital ballistic "drop-ship" to allow any point-to-point travel in 90 minutes or so.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/24/2015 03:38 PM
There are other applications of the pre-cooler. Improving flight range via greater engine efficiency; higher speed from existing engines without overheating the engine; even reducing the IR signature of engine exhaust (which wasn't one I'd previously considered.) Plus you've got the ongoing interest in fast-turnaround small-sat launchers, a la DARPA XS-1.

Just to note but these were "somewhat" brought up by REL as part of pushing the HE technology as a breakthrough "on-par" with the development of the jet engine itself and unfortunately isn't as "applicable" as REL made it out to be or having all that many "applications" above and beyond its actual use in SABRE.

Deep-Cooling can in fact extend the usable Mach range of a turbine based engine as well as increasing thrust output. But this was shown with previous work including the most recent Mass-Injection-Pre-Compressor-Cooling, and in fact does not require Liquid Hydrogen to accomplish things like a doubling of thrust and Mach number of the turbine engine. Increased engine efficiency is possible but only if the entire engine is run using hydrogen fuel as a standard hydrocarbon engine wouldn't stand to gain much due to the use of multiple fluids. (Which is already an "issue" with standard MIPCC which uses LOX/Water both of which are far more compact and easier to use than LH2)

"Standard" (LOX/Water) MIPCC can extend the Mach number of a standard (F100 for example) low-bypass turbofan from Mach-2 to Mach-4 and double or more the output thrust. Deep-Cooling with LH2 through an HE might extend this to Mach-6 though the extensive "bulk" of the LH2 tankage and system would probably greatly increase the vehicle design and complexity.

Exhaust IR mitigation IS a possible use but again mitigation doesn't "require" the use of liquid hydrogen and again unless the whole vehicle/engine is based on LH2 propulsion the use of an LH2 HE and bypass cooling air system wouldn't be very effective in operational use due to the added complexity and cost.

Last I looked the XS-1 program was specifically avoiding LH2 due to such systems NOT having fast turn around capability of more benign cryogenic systems such as LOX/Kero.

In most operational cases, unless your engine system and therefore your vehicle design overall, is using LH2 for fuel the efficiency isn't all that clear cut a case. Which is I suspect one of the (many) reasons no one is jumping on the REL investment bandwagon :)
What they are doing is directly relatable to GTO (Ground-To-Orbit) launch but doesn't have much broader uses under the current situation.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/24/2015 03:52 PM
I wouldn't be surprised if it's for SUSTAIN ("Marines in Space") - see http://www.popsci.com/military-aviation-space/article/2006-12/semper-fly-marines-space
http://www.popularmechanics.com/military/a5539/plans-for-marines-in-space/
http://www.defenseindustrydaily.com/hypersonic-rocketplane-program-inches-along-0194/

Those stories talk about a 2-stage concept however, and whether with scramjets or sabre (hydrogen fuel issue again), that's going to be one very expensive ride to ditch in the middle of a conflict zone
Welcome to the forum and the thread.

Firstly "Force projection" through space has a long history. Bono and Gatlands "Frontiers of Space" looked at delivering 100s of Marines at a time by "ballistic transport" IE near SSTO sub orbital vehicles. That was around 1969.

Earlier than that actually :)

@1958 the Army did some research on delivering troops and/or supplies to the front lines by sub-orbital ballistic missile delivery. Specifically the "Redstone" IRBM:
http://www.popsci.com/blog-network/vintage-space/riding-rocket-battlefield

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/24/2015 04:40 PM
2) deliver the specifically designed lander into space, and bring the squad there when it is needed.

The lander-in-orbit would be limited to a single window in a single orbital plane, making it incompatible with the goal of a suborbital ballistic "drop-ship" to allow any point-to-point travel in 90 minutes or so.

Just to make sure everyone's on the same page, the actual SUSTAIN/Hot Eagle requirements had the vehicle being capable of P2P travel OR being put into orbit as a "standby" measure for "drop" at any point up to several days later.

The conflicting requirements of those two mission parameters were something that was never addressed and would drive a "vehicle" design that would be very costly to meet both requirements.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/24/2015 06:49 PM
Do we think we know enough about SABRE to state categorically that it only works when integrated with a Skylon type of airframe?

SABRE isn't tightly integrated with the airframe like a scramjet is.  All it strictly requires is a source of liquid hydrogen.

The only airframe-integration feature I can think of is the nacelle camber, which is due to the difference between the desired angle of attack and the desired angle of thrust.

That's my understanding too. So what other airframe configurations might make sense? And are there any that are less ambitious/costly than the Skylon vehicle as currently conceived?

That's my understanding too. So what other airframe configurations might make sense? And are there any that are less ambitious/costly than the Skylon vehicle as currently conceived?
That's tricky without understanding why they developed this configuration.

The problem is twofold.

The Centre of Pressure shifts a lot over an airframe going from 0-M23-0

The Centre of Gravity shifts a lot because propellant is a much bigger fraction of the vehicle weight than in an aircraft.

A key  problem with HOTOL was with the engines at the back as the tanks emptied you had very little mass to stop the body "flipping" upward, so you needed a huge set of control surfaces (and their actuators) to keep the nose at the right angle. IIRC Bond said "2000 tonne metres" IE a small ship on those control surfaces.

Terrestrial aircraft can get away with the engines at the back (Trident DC-10, Caravelle) because of a) A relatively empty fuselage b) "Wet" wings and c) More "dead" weight in the vehicle to counter balance the weight of the engines in the back.

There are various configurations you could build a SABRE (ideally a pair of SABRES) into but they all face 2 problems.

High pressure LH2 engines (or rather their turbo pumps) scale down badly so you'd want to use full size SABRE engines.

It's not what your sub scale prototype can demonstrate it's what it cannot. Those things can only be demonstrated in the full size vehicle, IE a Skylon. So you're building a Skylon (actually REL are planning 2 flight test Skylons) and  this demonstrator/proof-of-concept/whatever vehicle, so your overall budget goes up.  :(

My instinct is the simplest way to go is with full size SABRES propelling a reduced scale Skylon airframe with narrower, shorter fuselage, no payload bay (and no payload  :( ) and much lower propellant load.

If such a vehicle matches a full sized Skylons aerodynamics and mass properties then its results should be transferable directly to the full size Skylon, shortening the flight programme of the full sized vehicles to lower the overall development budget and "squaring the circle" of using 3 vehicles instead of 2 but still working out cheaper.   :)

IRL my instinct is that being able to scale a design to that way while preserving all the main features is a very big "if" indeed. I suspect the range over which you could scale the airframe while a)Using full size SABRES and b)keeping the various mass properties and aerodynamic coefficients matching the full size vehicle is very limited.

The question is not "can you scale it down" but "do you save so much on the test budget it's worth doing" ?

I suspect the answer comes out "Build a full size Skylon with full size engines and no payload bay (there is room, but only enough is installed to preserve necessary structural stiffness) and smaller tanks," and I think REL have a better idea of the answer, but I don't know what it is.  :(

But, as a thought exercise, a squished pancake shape might work. Internally, you have three rows of cylindrical spaces, center with payload bay and fore/aft LOx tanks flanked by full length LH2 tanks. Fit the SABRE equipment near the mid-fuselage edge of the pancake, with a 2D ramp inlet on its side, and exhaust is half an aerospike ramp on its side. That largely preserves the basic Skylon layout (which does well to deal with cg changes), but frontal area drag unfortunately goes up which goes against the partial cruise accelerator profile. The only advantage to that layout is if you were doing something kinky like receiving external heating AKA Laser Skylon, as you could have a better receiver area.
If cost is the issue for a prototype you'd scrap the payload bay. This layout might handle the Cp/Cg shifts well enough to do the whole flight trajectory.

But look what you've lost  :(

This design is reminiscent of the "pye wacket" missile concept for an armed SR71 but AFAIK it has no flight history in other vehicles you can call on to refine the design.

Then you're suggesting some altitude compensation by expansion against the underside, which raises the temperature quite a bit.

And once you've got it working how do you translate the measurement of the flight programme to that of a Skylon?

It's a tough problem.  :(

Very good discussion of various flight issues and body type trade offs. Couple of points:

Just a correction JS19 but the "Pye Wacket" lenticular missile was being designed for the XB-70, not the SR-71 :)

-An alternative Skylon design by the Centre for Future Air-Space Transportation Technology (cFASTT,)at the University of Strathclyde  has already come out suggesting various changes to enhance the "basic" design by REL.
http://www.strath.ac.uk/fastt/
https://www.facebook.com/cFASTTstrath/photos_stream?ref=page_internal
http://www.rocketeers.co.uk/node/3129
http://strathprints.strath.ac.uk/48572/1/Wuilbercq_R_et_al_Pure_Robust_multi_disciplinary_design_and_optimisation_of_a_reusable_launch_vehicle_Jun_2014.pdf

-As noted the main reason for the current suggested design of the Skylon is to reduce the aerodynamic variables that are associated with changes in CP/CG over the flight trajectory. However the design functions end up so that the basic design is almost "required" to be along certain lines. The engines are going to end up either under the airframe or on the wings, beyond that your airframe choices, due to the aim to reach minimum hypersonic (Mach-5) speed ends up being similar to Boeing Model 1074-xxxx (sometimes called the "Hyperdart") interceptor design. (Which was designed around the Mach-4.5 hydrocarbon/H2O2 propellant SERJ engine) Reference: http://www.secretprojects.co.uk/forum/index.php/topic,11580.0/all.html?PHPSESSID=2f9apo98c9kqtupnof6cmqo6u5

Which dates from the mid-60s hence the "needle" nose instead of the more common "shovel" nose you'd see today.

Much as I like the idea of a lenticular design ("Pye Wacket" see: http://www.rimworld.com/dsp/pyewacket.html, and http://aviationtrivia.blogspot.com/2010/05/in-1947-researchers-at-wright-patterson.html) as noted it doesn't lend itself well to hypersonic accelerator designs though it HAS been suggested in the past. (LM among others patented several designs for supersonic and hypersonic models in the 60s such as this: http://www.freepatentsonline.com/3066890.pdf, but you'll note how difficult fitting LH2 tanks into such a design would be. Moving the engines towards the outer sections and the tankage towards the middle induces intake issues and mounting the engines above or below the vehicle with a lenticular design offers none of the normal intake/exhaust compression/expansion advantages that a more dedicated (and normal layout) design would. And as noted higher drag and therefore heating would be an issue.

In the end the basic shape that REL has chosen for the baseline Skylon so they can have something to anchor their work in is what you're going to end up with in a very close approximation unless you have some compelling reason to go with a more radical airframe design. And the reason would have to be VERY compelling given the amount of data the "baseline" design has available.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/24/2015 10:47 PM
Very good discussion of various flight issues and body type trade offs. Couple of points:
Thank you.
Quote
Just a correction JS19 but the "Pye Wacket" lenticular missile was being designed for the XB-70, not the SR-71 :)
Oops. My memory playing tricks with me. I conflated the SR71 with the missile.
Quote
-An alternative Skylon design by the Centre for Future Air-Space Transportation Technology (cFASTT,)at the University of Strathclyde  has already come out suggesting various changes to enhance the "basic" design by REL.
http://www.strath.ac.uk/fastt/
https://www.facebook.com/cFASTTstrath/photos_stream?ref=page_internal
http://www.rocketeers.co.uk/node/3129
http://strathprints.strath.ac.uk/48572/1/Wuilbercq_R_et_al_Pure_Robust_multi_disciplinary_design_and_optimisation_of_a_reusable_launch_vehicle_Jun_2014.pdf

-As noted the main reason for the current suggested design of the Skylon is to reduce the aerodynamic variables that are associated with changes in CP/CG over the flight trajectory. However the design functions end up so that the basic design is almost "required" to be along certain lines. The engines are going to end up either under the airframe or on the wings, beyond that your airframe choices, due to the aim to reach minimum hypersonic (Mach-5) speed ends up being similar to Boeing Model 1074-xxxx (sometimes called the "Hyperdart") interceptor design. (Which was designed around the Mach-4.5 hydrocarbon/H2O2 propellant SERJ engine) Reference: http://www.secretprojects.co.uk/forum/index.php/topic,11580.0/all.html?PHPSESSID=2f9apo98c9kqtupnof6cmqo6u5

Which dates from the mid-60s hence the "needle" nose instead of the more common "shovel" nose you'd see today.
Given the advances in supersonic and hypersonic flow heating analysis is the "needle nose" even plausible today?
Quote
In the end the basic shape that REL has chosen for the baseline Skylon so they can have something to anchor their work in is what you're going to end up with in a very close approximation unless you have some compelling reason to go with a more radical airframe design. And the reason would have to be VERY compelling given the amount of data the "baseline" design has available.
Indeed. Once  you consider the full list of constraints a design must meet the options are quite limited.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 02/24/2015 11:41 PM
and in fact does not require Liquid Hydrogen [...]
Exhaust IR mitigation IS a possible use but again mitigation doesn't "require" the use of liquid hydrogen

Neither does Bond's heat exchanger. Indeed the major testing has not been with LH on the cold-side of the He-loop. LH is a requirement for Skylon because of the hypersonic operating environment where they need around 1000°C cooling (as would most hypersonic applications, for the same reason.) Outside of that operating environment, you pick the coolant to suit the application.

The key to Bond's idea is a) that it's frostless, b) that it's fast, and c) that it's both hot- and cold-side agnostic. The first lets you use where you can't use other heat-exchanges, the second means it acts almost like a thermal-superconductor (it will near-instantly cool the hot-side close to the temp of whatever is on the cold-side), the last means it's flexible for more applications. A bonus is that it's ridiculously light as a side-effect of (b).

[I do like how now I'm arguing that REL understands their pre-cooler well enough to model applications, while you're arguing that they've been a little premature/overenthusiastic...]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/25/2015 12:48 PM
Which dates from the mid-60s hence the "needle" nose instead of the more common "shovel" nose you'd see today.
Given the advances in supersonic and hypersonic flow heating analysis is the "needle nose" even plausible today?

Actually yes. Needs some "tweeks" but really the only "difference" between the styles is how much they effect overall fore-body compression and acceleration profile.

and in fact does not require Liquid Hydrogen [...]
Exhaust IR mitigation IS a possible use but again mitigation doesn't "require" the use of liquid hydrogen

Neither does Bond's heat exchanger. Indeed the major testing has not been with LH on the cold-side of the He-loop. LH is a requirement for Skylon because of the hypersonic operating environment where they need around 1000°C cooling (as would most hypersonic applications, for the same reason.) Outside of that operating environment, you pick the coolant to suit the application.

To be more clear and specific pre-cooling and thrust augmentation doesn't even require a heat exchanger. But overall I think we're saying the same thing.

Quote
The key to Bond's idea is a) that it's frostless, b) that it's fast, and c) that it's both hot- and cold-side agnostic. The first lets you use where you can't use other heat-exchanges, the second means it acts almost like a thermal-superconductor (it will near-instantly cool the hot-side close to the temp of whatever is on the cold-side), the last means it's flexible for more applications. A bonus is that it's ridiculously light as a side-effect of (b).

[I do like how now I'm arguing that REL understands their pre-cooler well enough to model applications, while you're arguing that they've been a little premature/overenthusiastic...]

Sorry if that was the impression of what I was saying but I'm NOT actually arguing RELs process or methods I'm simply pointing out that their process/methods are designed towards their needs and models. I was pointing out that there are other methods of achieving similar results. And I'm in no way arguing that those other methods are applicable to RELs work as they are obviously not though the results and data obtained from the earlier work IS applicable for REL's modeling purposes.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Moe Grills on 02/25/2015 04:05 PM
   Right!   Since I never consider WORDS or DEBATE to be equivalent to proof, I patiently await the suborbital test-flight of the aerospace frame that will ATTEMPT to use the scaled down version of the SABRE engine before this decade is out.  Only until then will I consider this advanced technology to be feasible or not, practical or not.


I repeat the sentence fragment, "before this decade is out", noting that it was used by JFK to push a project that made history, revolutionized technology and achieved an ambitious goal. Perhaps it may apply to the SKYLON/SABRE. We hope!  Fingers crossed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 02/25/2015 04:48 PM
@Moe Grills
They're building a full-size SABRE. Not a scaled down version. The costs and difficulties involved in the engineering of the engine mean that a full-sized engine makes more sense.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Moe Grills on 02/25/2015 07:06 PM
@Moe Grills
They're building a full-size SABRE. Not a scaled down version. The costs and difficulties involved in the engineering of the engine mean that a full-sized engine makes more sense.

I guess size matters, maybe.
BTAIM, If it works, bully to Mr. Bond and his engineering disciples; a spaceflight revolution can then begin sometime next decade.  If it doesn't work,  alas, humanity will have to plod along with conventional boosters for another century perhaps.
Fingers crossed that it may work as advertised.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/25/2015 07:10 PM
@Moe Grills
They're building a full-size SABRE. Not a scaled down version. The costs and difficulties involved in the engineering of the engine mean that a full-sized engine makes more sense.

I guess size matters, maybe.
BTAIM, If it works, bully to Mr. Bond and his engineering disciples; a spaceflight revolution can then begin sometime next decade.  If it doesn't work,  alas, humanity will have to plod along with conventional boosters for another century perhaps.
Fingers crossed that it may work as advertised.

Well for one thing it will cut down a small bit on the people who will still refuse to believe the engine will work because "it's ONLY a scale-model" :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/25/2015 08:26 PM
Well for one thing it will cut down a small bit on the people who will still refuse to believe the engine will work because "it's ONLY a scale-model" :)
But only a small bit  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/25/2015 08:45 PM
IIRC the plan for SCEPTRE is a full size prototypes/demonstrator rengine  but it will not be laid out to fit inside the cowling - more like a breadboard than something you could fly. Anyone know if that's correct? I'm also not sure if SCEPTRE will include thrust chambers and/or nozzles, but I'm going to guess not.

If it is not tightly packaged as it will be in the cowling then that will make it easier to troubleshoot and tweak. But doesn't a lot hinge on the plumbing/flow properties and thermal cycles that are influenced by layout? If so, will that necessitate a SCEPTRE 2.0?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 02/25/2015 09:40 PM
AFAIK they've decided to skip sceptre and go straight to developing a fully integrated full-size SABRE. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 02/25/2015 09:54 PM
IIRC the plan for SCEPTRE is a full size prototypes/demonstrator rengine  but it will not be laid out to fit inside the cowling - more like a breadboard than something you could fly. Anyone know if that's correct? I'm also not sure if SCEPTRE will include thrust chambers and/or nozzles, but I'm going to guess not.

If it is not tightly packaged as it will be in the cowling then that will make it easier to troubleshoot and tweak. But doesn't a lot hinge on the plumbing/flow properties and thermal cycles that are influenced by layout? If so, will that necessitate a SCEPTRE 2.0?

I agree with your views on the full scale engine being a (breadboard) design. Building a full size engine with no restrictions on fitting into a cowling is sensible, just prove it works and leave a R/R type company to carry out the design needed to fit into the cowling and any further work needed to produce a flight ready engine. I am certain this will produce an  engine for ground tests much sooner.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 02/25/2015 11:12 PM
LH is a requirement for Skylon because of the hypersonic operating environment where they need around 1000°C cooling (as would most hypersonic applications, for the same reason.) Outside of that operating environment, you pick the coolant to suit the application.

True.  But in the case of aircraft propulsion specifically, hydrogen is far and away the best match.  It could still make sense with a different fuel, but I don't really see it as a game-changer.

When flying at Mach 5, SABRE - even the latest version - uses far more hydrogen for cooling than the core can burn.  The excess has to be burned at lower efficiency in a bypass ramjet.  Now consider that liquid hydrogen's heat soak capability per unit of combustion energy is at least double that of jet fuel.  By the time you got the speed down to the point where you weren't wasting fuel, you'd be getting close to the range accessible to existing engine technology without precooling - which is faster than any modern aircraft actually flies, there being other reasons not to bother going that fast.

On the other hand, even flying at Mach 3 or so, you might get a substantial improvement in T/W and perhaps SFC from being able to deal with air at about room temperature rather than at 350°C (of course the advantage would have to be great enough to justify the additional weight, cost, and maintenance overhead of the precooler and associated systems).  But a subsonic engine wouldn't gain much without a cryogenic propellant.

Dumping the heat while retaining the coolant isn't really an option as far as I can tell.  A water-cooling loop using the skin of the airframe as the cold side would still be well over an order of magnitude short of the heat transfer rate required, unless I messed up my quick ballpark calculation...

Building a full size engine with no restrictions on fitting into a cowling is sensible, just prove it works and leave a R/R type company to carry out the design needed to fit into the cowling and any further work needed to produce a flight ready engine.

Reaction Engines plans to build the engines themselves.  And while I could be wrong, I do think their full-scale engine will be in proper cowling form factor, based on how they've described it in contrast to the "dissected rabbit" that was SCEPTRE.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/26/2015 12:12 AM
Interesting - I missed the change away from the 'dissected rabbit'. Hopefully that's indicative of confidence in all the theoretical and simulation work they've done, rather than impatience.

Any idea if what they're building includes everything, i.e. combustion chambers, nozzles, bypass burners, etc?

And does this match up with the phasing they mentioned in 2013 - where 3a included SCEPTRE? A near-flight-worthy engine is much more ambitious (expensive) than what I was expecting.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 02/26/2015 08:51 AM
Interesting - I missed the change away from the 'dissected rabbit'. Hopefully that's indicative of confidence in all the theoretical and simulation work they've done, rather than impatience.

Any idea if what they're building includes everything, i.e. combustion chambers, nozzles, bypass burners, etc?

And does this match up with the phasing they mentioned in 2013 - where 3a included SCEPTRE? A near-flight-worthy engine is much more ambitious (expensive) than what I was expecting.

From Jeremy Nickless' talk last December http://forum.nasaspaceflight.com/index.php?topic=34964.msg1298468#msg1298468

Quote from: SICA Design
Phases 3 & 4 of the £10bn project now stretch over 10.5 years, of which £3.64bn is for SABRE. Phase 3 (£0.36bn) commenced April 2014 and approximately £100m has been secured, with approx £250m to secure in the next few years. Phase 4 is due to commence October 2018, with a (new) Skylon in-service date of October 2024.

Valkyrie? - "Could not possibly comment on that". Phase 3 WILL however involve a flying SABRE engine (not Skylon).
:
:
Quote
My impression was a single full-size SABRE with wings and tank
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/26/2015 10:16 AM
Valkyrie? - "Could not possibly comment on that". Phase 3 WILL however involve a flying SABRE engine (not Skylon).
My impression was a single full-size SABRE with wings and tank
If you're not going with something looking like a Skylon you loose pretty much any benefits from getting early test data you can apply to the full vehicle  :(

Building one engine should be cheaper than two but with minimum order quantities, and discounts for buying large blocks, I'm not sure it would be that much cheaper.

You're now looking at something a long way from the Skylon. How big a problem that is depends on what speed range you're operating over.

 The issue would seem to be the air breathing to rocket transition at about Mach 5.5. A flying test vehicle (if it looks nothing like a Skylon it's not a prototype) operating up to say Mach 6 could be used to fine tune the Nacelle structure (like the NTV) and demonstrate the switchover to rocket mode before circling round to come back for a landing.

Following the rule of X-plane design that the only advanced technology you are using is the technology you're testing in the first place they should probably avoid the SiC reinforced Titanium space frame and PyroSic skin of a full Skylon.

M6 is in X15 territory, a vehicle designed to study prolonged airframe heating effects (when the whole airframe is cooked through). half a century later designing a vehicle for short duration flight at this speed (as it turns around to head for home) should not be beyond skills of a competent design team, especially given the commercial availability of things like Reinforced Carbon Carbon (and the flat plate techniques pioneered in the SHAFEX 1 and 2 programmes by DLR)

An interesting question would be if the vehicle is that much lighter and simpler (I don't think it'll be having a 15 tonne payload bay for starters  :( ) could it run on something other than LH2? Personally I hope not as this would reduce the "traceability" of the design to SABRE/Skylon design

Personally I'd like to see it make orbit and return. Such a "whole trajectory" demonstration would be hugely impressive and dramatically move the goalposts on the question "Is SSTO possible?"

No I don't think there's any chance of that happening.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 02/26/2015 10:35 AM
My impression was a single full-size SABRE with wings and tank
If you're not going with something looking like a Skylon you loose pretty much any benefits from getting early test data you can apply to the full vehicle  :(

My impression could (of-course) be completely wrong, but it would advance REL's position (as engine mfg) and separate the issues of Skylon from SABRE.

Successful testing of SABRE through air and vacuum would surely encourage airframers to get onboard with Skylon development. It would be one further huge landmark in RELs track record of delivering what they claim.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/26/2015 11:30 AM
My impression could (of-course) be completely wrong, but it would advance REL's position (as engine mfg) and separate the issues of Skylon from SABRE.

Successful testing of SABRE through air and vacuum would surely encourage airframers to get onboard with Skylon development. It would be one further huge landmark in RELs track record of delivering what they claim.
It's a swings and roundabouts problem.  :(

Yes you get early evidence that SABRE 4 engine can run up to at least M6 (I don't really see much point if the demonstrator doesn't go at least that high) you're still left with building 3 vehicles when they were expecting to build 2.  There is also the issue that anyone with serious money to put into the project will have had a technical evaluation done anyway and would not expect this to be a problem in the first place.

But you're right it would be another land mark that demonstrates that (when funded) REL can deliver what they say when they say.

Don't misunderstand me. I would love to see a demonstrator sooner rather than later but the whole budget is very large. If they can do it without enlarging it further that would be great

My feeling around forming the Skylon consortium is to find some way to get potential customers to sign an agreement with REL that can be passed to the consortium (when formed)  effectively saying

"We (country, corporation or other entity) agree to buy X Skylons at $Ym in 20xx prices(adjusted to the inflation up to the purchase date) and a support contract at $Zm in 20xx prices(adjusted to the inflation up to the purchase date) subject to it meeting the specification listed below from the entity REL have passed this to"

If enough of these were obtained it would act as a)A big incentive for the members to join the consortium (as they'd know already there is  the customer base exists) and b)Banks could see there were customers already waiting to buy them, lowering the investment risk.

Note at that point No money has changed hands, it's simply the demonstration that there is demand  out there.

That still leave plenty of problems. Have you got enough "pledges" to buy to cover the whole development cost? Can you build Skylons for that price and make a profit? If there is a time clause can you get Skylon flying before the pledge expires?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 02/26/2015 02:16 PM
I'm sure this is ridiculous for many reasons but:   Could SABRE be tested by bolting it on to or into some existing airframe as is done with new jet engines?

I presume full power would not be possible unless perhaps for fractions of a second and the maximum speed would have to be very low compared to SABRE's potential hence perhaps it's completely nonsensical?

Would there be anything to gain from this?  e.g. behaviour at various altitudes, ability to restart ...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aga on 02/26/2015 02:41 PM
what existing aircraft uses lh2?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/26/2015 02:48 PM
I'm sure this is ridiculous for many reasons but:   Could SABRE be tested by bolting it on to or into some existing airframe as is done with new jet engines?

I presume full power would not be possible unless perhaps for fractions of a second and the maximum speed would have to be very low compared to SABRE's potential hence perhaps it's completely nonsensical?

Would there be anything to gain from this?  e.g. behaviour at various altitudes, ability to restart ...
You're perhaps thinking of the Olympus engine tests for Concorde, where (IIRC) a test engine for the Concorde version was mounted underneath a Vulcan bomber (powered by 4 more of them). IE roughly 1/4 the full thrust of the aircraft, Or the LASRE tests planned for NASA's SR71 in the X33 programme.

The trouble is a full size SABRE has roughly 4.5x the thrust of all the engines on an Airbus 380, and that won't even get you to Mach 1.  :(

You're pretty much going to build some sort of airframe around it (or underneath it).

Unobstructed airflow is going to be a big issue with this. The best (simplest) ideas I can come up with are putting wings on either side of single nacelle (about the simplest possible structure but a lot of stuff has to go inside those wings like fuel and landing gear)  or something like a V1, with a minimal body to limit flow obstruction at the back.

In principle the narrower the Mach range (and the lower the payload) the less you have to worry about the Cp/Cg shifts that drove the Skylon design in the first place but building a single engine vehicle which has adequate  airflow over a wide enough Mach range to be useful is (I think) going to be very tricky.  :(

My heart likes the idea of an early flight test vehicle with a (pair ?) of full size SABREs but my head says either the overall budget gets bigger or they fund from cuts from elsewhere, and it seems nothing is in the budget that doesn't need to be there already.   :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: NovaSilisko on 02/26/2015 03:01 PM
what existing aircraft uses lh2?

I've now got silly visions of a large airliner with one engine replaced with a SABRE, and another replaced with an aerodynamic LH2  tank...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 02/26/2015 03:18 PM
what existing aircraft uses lh2?

I've now got silly visions of a large airliner with one engine replaced with a SABRE, and another replaced with an aerodynamic LH2  tank...

I was going to point that out but IIRC there is a converted 707 with an LH2 tank in the boneyard from testing done in the early 70s.

However you'd really need a dedicated airframe unless you're JUST testing subsonic and takeoff/landing characteristics which is of limited value. You could go as far as mounting it to the side of an air-cargo aircraft and installing an LH2 tank in the cargo bay but the utility is limited at best.

I suspect JS19s idea is about what you'll get for flight testing.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 02/26/2015 03:43 PM
You're perhaps thinking of the Olympus engine tests for Concorde, where (IIRC) a test engine for the Concorde version was mounted underneath a Vulcan bomber (powered by 4 more of them). IE roughly 1/4 the full thrust of the aircraft, Or the LASRE tests planned for NASA's SR71 in the X33 programme.

The trouble is a full size SABRE has roughly 4.5x the thrust of all the engines on an Airbus 380, and that won't even get you to Mach 1.  :(

I wonder, could they build a full-scale SABRE but 1/4 power, i.e. fit some dummy (blanking) HX modules, only fit 1-of-4 combustion chambers / nozzles. Not sure how this would affect the compressor and other cooling loop / turbo machinery. Aim being to reduce power to suit smaller airframe, but still get relevant test results from full-scale components.

Any merit to this?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/26/2015 04:30 PM
We've certainly heard that the back end of SABRE is in essence two rocket engines driving four thrust chambers, and shutting down two of them is a planned failure mode. If that's still the case, half power in the test engine should be easy enough, and then add in whatever throttle-range it has.

Has minimum throttleable thrust ever come up before? This might be another reason to prefer E/D nozzles. IIUC wthout them Skylon startup thrust will need to be higher, and with SABRE's separated on wing-tips assymmetrical startup would be problematic.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/26/2015 04:54 PM
Interesting - I missed the change away from the 'dissected rabbit'. Hopefully that's indicative of confidence in all the theoretical and simulation work they've done, rather than impatience.

Any idea if what they're building includes everything, i.e. combustion chambers, nozzles, bypass burners, etc?

And does this match up with the phasing they mentioned in 2013 - where 3a included SCEPTRE? A near-flight-worthy engine is much more ambitious (expensive) than what I was expecting.

From Jeremy Nickless' talk last December http://forum.nasaspaceflight.com/index.php?topic=34964.msg1298468#msg1298468

Quote from: SICA Design
Phases 3 & 4 of the £10bn project now stretch over 10.5 years, of which £3.64bn is for SABRE. Phase 3 (£0.36bn) commenced April 2014 and approximately £100m has been secured, with approx £250m to secure in the next few years. Phase 4 is due to commence October 2018, with a (new) Skylon in-service date of October 2024.

Valkyrie? - "Could not possibly comment on that". Phase 3 WILL however involve a flying SABRE engine (not Skylon).
:
:
Quote
My impression was a single full-size SABRE with wings and tank

Thanks. You know, for a project that's not due until the mid 2020s we generate a lot of messages!

I would love to know how much of the 'build a flying SABRE' plan is dependent on the next £250m coming in, and what happens if it's late, or doesn't materialise. Here are a couple of options, one very cautious, and one not:

1] Spend the £100m to complete more ground-based component testing. Start work on the flyable Skylon when/if the £250m comes in. If it hasn't showed up when the £100m has been spent, REL goes into quiet mode awaiting money. Alan Bond retires soon thereafter, but the company continues.

2] Start spending the £100m to get ~ 1/3 of the way to a flying SABRE. If no-ones comes forth with the needed £250m to finish it, wasting that £100m will not reflect well on REL.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 02/26/2015 06:50 PM
I would love to know how much of the 'build a flying SABRE' plan is dependent on the next £250m coming in, and what happens if it's late, or doesn't materialise. Here are a couple of options, one very cautious, and one not:

1] Spend the £100m to complete more ground-based component testing. Start work on the flyable Skylon when/if the £250m comes in. If it hasn't showed up when the £100m has been spent, REL goes into quiet mode awaiting money. Alan Bond retires soon thereafter, but the company continues.

2] Start spending the £100m to get ~ 1/3 of the way to a flying SABRE. If no-ones comes forth with the needed £250m to finish it, wasting that £100m will not reflect well on REL.
The obvious route is to build and test the engine on the ground but plan the necessary features for it to be installed in an airframe.

REL have shown they are very careful at structuring the work they have to do relative to the funds they have.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 02/26/2015 07:02 PM
Sounds sensible. I wonder how much of a ground-based SABRE they can build for the £100m they have in hand. If most/all, we can reasonably expect to see something engine-shaped being built in Oxford over the next few years.

Edit: just went back to the January press release, and that says static test 'before the end of the decade.' So the flying SABRE test vehicle is early 2020s, which leads me to think that the additional £250m is needed to get through the static test.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: space_britannia on 03/01/2015 03:14 AM
2) deliver the specifically designed lander into space, and bring the squad there when it is needed.

The lander-in-orbit would be limited to a single window in a single orbital plane, making it incompatible with the goal of a suborbital ballistic "drop-ship" to allow any point-to-point travel in 90 minutes or so.

Just to make sure everyone's on the same page, the actual SUSTAIN/Hot Eagle requirements had the vehicle being capable of P2P travel OR being put into orbit as a "standby" measure for "drop" at any point up to several days later.

The conflicting requirements of those two mission parameters were something that was never addressed and would drive a "vehicle" design that would be very costly to meet both requirements.

Randy

Just considering the first one then, since they would seem impossible to reconcile, what they have in mind would seem to be an LH2-fuelled skylon-like carrier, dropping a jet-fuelled lander (since ability to retrieve troops and craft was a desired characteristic), equipped with heat shielding.

Even if a suitable heat shield material was available, the main problem seems to be with the skyon-like carrier - what happens to it after release? If it goes to orbit once-around, then maximum payload for the lander is limited to in the region of Skylon's 15 tons. If it is on a suborbital trajectory, it would re-enter in uncontrolled airspace, and would have to be refuelled at a LH2-capable runway.
 
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/01/2015 09:27 AM
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible
Correct.

The CRADA is about specifically about the SABRE engine cycle.

If they'd wanted Hypersonic cruise I'm quite sure they'd have requested more information on the LAPCAT work for M5 cruise.

Put it this way, if they are not looking at SABRE for use in a launch vehicle they are very foolish.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 03/01/2015 02:31 PM
If it's just the engine cycle itself, ie the thermodynamic cycle, then it probably doesn't need to include any specific  information on the heat exchangers and frost control mechanisms.

And is it the SABRE 3 or SABRE 4 engine cycle?

What might the USAF gain from studying the thermodynamics of the engine cycle?  ie what applications or insights might it give them for future planning? Is it like JS19 suggests - the only real reason for studying the cycle in this engine is to look at possible applications for launch capacity only.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/01/2015 05:37 PM
If it's just the engine cycle itself, ie the thermodynamic cycle, then it probably doesn't need to include any specific  information on the heat exchangers and frost control mechanisms.
It will contain specific information regarding things like mass flow rates, temperature differences and inlet and out let temperatures (on both fluids). At this level it's mathematics. How those features are implemented is another question entirely.
Quote
And is it the SABRE 3 or SABRE 4 engine cycle?
This has been mentioned. It'll be SABRE 3 as that can be compared with the work funded by ESA and done at the Von Karman institute. That means the USAFRL can set up the same input conditions and expect the same output conditions. If that doesn't happen then someone has implemented the model of the engine wrong, which is a very handy thing to find out.

AFAIK the detailed performance of the SABRE 4 cycle are still private to REL.
Quote
What might the USAF gain from studying the thermodynamics of the engine cycle?  ie what applications or insights might it give them for future planning? Is it like JS19 suggests - the only real reason for studying the cycle in this engine is to look at possible applications for launch capacity only.
Have seen how much the USAF spends on launch only.

Gwen Shotwell at her NATO presentation said to the effect that "National Security Space launch is the US space launch market and you have to be in it to a major player in US space launch."
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: MichaelBlackbourn on 03/01/2015 06:00 PM
Any chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.

How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? :)

Or maybe a disposable frame that gets ejected and then drops the troops.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 03/01/2015 06:36 PM
JS19
**It'll be SABRE 3**

I missed that info. Thanks. :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: space_britannia on 03/01/2015 07:51 PM
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible
Correct.

The CRADA is about specifically about the SABRE engine cycle.

If they'd wanted Hypersonic cruise I'm quite sure they'd have requested more information on the LAPCAT work for M5 cruise.

Put it this way, if they are not looking at SABRE for use in a launch vehicle they are very foolish.  :(

Clearly they are looking at launch rather than hypersonic cruise, my question is if it is SUSTAIN they have in mind then how are they going to make this sabre carrier / turbojet lander architecture work
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/02/2015 08:33 AM
Clearly they are looking at launch rather than hypersonic cruise, my question is if it is SUSTAIN they have in mind then how are they going to make this sabre carrier / turbojet lander architecture work
Welcome to the forum.

The answer is rather obviously with extreme difficulty. :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/02/2015 10:05 PM
Any chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.

How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? :)

Or maybe a disposable frame that gets ejected and then drops the troops.
Welcome to the forum.

The bay is about  4.8m wide and about 16 m long. There is no option for a "tail ramp" type drop.

Unfortunately you're either going to need various bases at different longitudes to minimize plane change payload losses or  you have a fairly small minimum team the system can use.

If the vehicle is staying orbital to land further along track or plane change back to its launch base that means the personnel are carrying out individual reentries, or you have to do an orbital ejection of a re entry capable lander module while keeping the vehicle in tact. Either way a huge challenge.  Probably the closest to this architecture is the "Q bay" of the U2 and it's developments, built as a simple rectangular duct running top to bottom, but I'm not sure what facilities it supplied to the payload or if they were more or less self contained.

Option B is to have the vehicle already into a reentry so a chunk of velocity is already lost. Now you're looking at something like an ejection. The highest is about M3 from an SR71, however it seems due to the altitude (around 80 k feet) which apparently equates to something like 400mph.

This is one of those sounds-cool-but-is-really-nonsense ideas that's great for the plot of a straight-to-download action movie.

IRL not really that good.  :(

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 03/03/2015 11:51 AM
UK ministers issue spaceport shortlist:-

http://www.bbc.co.uk/news/science-environment-31711083

Three of the 6 shortlisted sites have runways under 3000m, with implications for Skylon unless rectified.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 03/03/2015 11:58 AM

UK ministers issue spaceport shortlist:-

http://www.bbc.co.uk/news/science-environment-31711083

Three of the 6 shortlisted sites have runways under 3000m, with implications for Skylon unless rectified.

Already a dedicated thread for this.

http://forum.nasaspaceflight.com/index.php?topic=35163
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/03/2015 12:40 PM
UK ministers issue spaceport shortlist:-

http://www.bbc.co.uk/news/science-environment-31711083

Three of the 6 shortlisted sites have runways under 3000m, with implications for Skylon unless rectified.
I don't think any of the runways have the necessary 5000m for a full Skylon runway.

Logically Newquay, being at a slightly lower longitude is best if you want direct launch to orbit. Otherwise I think most of then could handle Skylon payload loading and take off in air breathing mode.

OTOH as Hempsell pointed out all UK sites are bad for equatorial launch, but OK for polar launch, which is handy for some kinds of Earth observation missions.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 03/03/2015 02:57 PM

UK ministers issue spaceport shortlist:-

http://www.bbc.co.uk/news/science-environment-31711083

Three of the 6 shortlisted sites have runways under 3000m, with implications for Skylon unless rectified.
I don't think any of the runways have the necessary 5000m for a full Skylon runway.

Logically Newquay, being at a slightly lower longitude is best if you want direct launch to orbit. Otherwise I think most of then could handle Skylon payload loading and take off in air breathing mode.

OTOH as Hempsell pointed out all UK sites are bad for equatorial launch, but OK for polar launch, which is handy for some kinds of Earth observation missions.

This isn't really relative to REL as they didn't even respond to the consultation.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 07:31 PM
And just to "tweak" the doubters again, ('cause its fun :) ) I was re-reading "Facing the Heat Barrier" again and found something I'd missed the first couple of time. Seems Lockheed has done some work on a "SABRE-like" engine for a 1962 space plane study with a system called "Tubo-LACE" (which was a misnomer as it didn't even USE LACE)

From “Facing the Heat Barrier” chapter 4, page 119:
“For takeoff, Lockheed expected to use Turbo-LACE. This was a LACE variant that sought again to reduce the inherently hydrogen-rich operation of the basic system. Rather than cool the air until it was liquid, Turbo-Lace chilled it deeply but allowed it to remain gaseous. Being very dense, it could pass through a turbocompressor and reach pressures in the hundreds of psi. This saved hydrogen because less was needed to accomplish this cooling. The Turbo-LACE engines were to operate at chamber pressures of 200 to 250 psi, well below the internal pressure of standard rockets but high enough to produce 300,000 pounds of thrust by using turbocompressed oxygen.”

All under the "Aerospaceplane" study effort that was sponsored by the Air Force looking for an air-breathing launch platform :)

As an additive "thunk" experiment, I was wondering if a modified REL HE could work effectively in reverse? (Using suitable materials of course) Having a "hot" heat exchanger in the place of a normal combustion chamber to provide heating of the air. I recall there was some work done by a small Canadian company on such a design for use with alternative fuels for aircraft engines though I can find nothing at the moment on it. The idea was you could use less than ideal fuels to provide thrust through the HE concept rather than burning the fuels directly in the airstream. Mostly because some fuels (peanut oil IIRC was one suggested fuel) don't burn in a high speed airstream as well as kerosene products, but some mention was made that heating a supersonic airflow (yes getting into my "favorite" engine cycle here the SCramjet :) ) without causing shockwaves due to injected fuel.

Probably impractical but discussions with someone on using an "electric fan fed" jet engine got me to thinking...

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 08:31 PM
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible
Correct.

The CRADA is about specifically about the SABRE engine cycle.

If they'd wanted Hypersonic cruise I'm quite sure they'd have requested more information on the LAPCAT work for M5 cruise.

Put it this way, if they are not looking at SABRE for use in a launch vehicle they are very foolish.  :(

And one thing the US in general and our military specifically is NEVER is foolish by assumption :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 08:47 PM
If it's just the engine cycle itself, ie the thermodynamic cycle, then it probably doesn't need to include any specific  information on the heat exchangers and frost control mechanisms.

And is it the SABRE 3 or SABRE 4 engine cycle?

What might the USAF gain from studying the thermodynamics of the engine cycle?  ie what applications or insights might it give them for future planning? Is it like JS19 suggests - the only real reason for studying the cycle in this engine is to look at possible applications for launch capacity only.

"Deep-cooled" airflow is actually useful in applications NOT related to launch but not many. On the other hand NO thermodynamic data is useless so even if the USAF is not interested in SABRE as a cycle or for launch purposes there's information to be had :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 09:11 PM
Any chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.

How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? :)

Or maybe a disposable frame that gets ejected and then drops the troops.
Welcome to the forum.

The bay is about  4.8m wide and about 16 m long. There is no option for a "tail ramp" type drop.

Not wanted or needed for supersonic drops anyway the air "above" the airframe is less disturbed and smoother in a relative way. And to prevent serious scatter and/or injury you'd want to eject the personnel in a pod of some type. We (the US) actually did some studies of dropping troops from a B-58 using the under-slung pod in a wind tunnel. Again the major problem was you can drop a whole company and supplies from a sub-sonic C-130 and get the job "done" where as specialized insertion has much less margin for supplies and more troops. It would take as squadron of B-58s to put the same number of boots (and kit) on the ground as one C-130 and the C-130 does it more efficiently and accurately as well.
(BTW: Studies have been done on supersonic and even hypersonic troop and supply drop and while you can use a "tail-ramp" it ends up being on TOP of the airframe and you have to chuck the stuff past the shockwave with something like a catapult so again, not very effective overall. Oh and you have to actually "pressurize" the bay to prevent sucking the shockwave into the airframe in order to "open-up" at supersonic speeds)

In retrospect it would actually have been neat to be able to have the option of supersonic dash into AO, drop to high-subsonic and dump the payload pod, then dash back up to supersonic for egress. But you still have all the issues of inserting into hostile territory with minimum forces that is inherent in the system. Hmmm, something more like a supersonic "Pack-Plane" maybe? (http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane) But the differences between with and without aerodynamics would probably be prohibitive let alone hypersonic and/or suborbital...

And on top of it all you have an institutional dislike of cryogenic fluids if they can at all be avoided...

Quote
Unfortunately you're either going to need various bases at different longitudes to minimize plane change payload losses or  you have a fairly small minimum team the system can use.

If the vehicle is staying orbital to land further along track or plane change back to its launch base that means the personnel are carrying out individual reentries, or you have to do an orbital ejection of a re entry capable lander module while keeping the vehicle in tact. Either way a huge challenge.  Probably the closest to this architecture is the "Q bay" of the U2 and it's developments, built as a simple rectangular duct running top to bottom, but I'm not sure what facilities it supplied to the payload or if they were more or less self contained.

DROP TROOPERS! :)
U2: Power and air conditioning as far as I know. The constraints were that the equipment had to fit into the bay and work on the provided air and electric.

Quote
Option B is to have the vehicle already into a reentry so a chunk of velocity is already lost. Now you're looking at something like an ejection. The highest is about M3 from an SR71, however it seems due to the altitude (around 80 k feet) which apparently equates to something like 400mph.

This is one of those sounds-cool-but-is-really-nonsense ideas that's great for the plot of a straight-to-download action movie.

IRL not really that good.  :(

Still need a pod or something to hold the troops together unless they individually have some sort of propulsion and guidance. HALO's do something similar from similar altitudes but they have control over their positioning during drop which a supersonic drop would not have. (Imagine your "average" Marine's full kit. Now put a spacesuit on it and him and ask him to perform "simple" maneuvers in the gear. There's a reason the military was interested in the results of high altitude parachuting before Baumgartner did it :) )

And again you get about twice the useful payload to the target with a C-130 than you would with a Skylon under these circumstances...

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 09:16 PM
Any chance we can hack a ramp into the bottom of the payload bay for paratrooper deployment? Baumgartner up some airborne troops and fire them off the back of the ramp.

How does the payload bay compare to a c130 in number of troopers. And can the craft slow down long enough and low enough to deploy them and then land far downrange? :)

Or maybe a disposable frame that gets ejected and then drops the troops.

Capacity: Skylon is this role would be around 15mT where as the C-130 delivers 33mt so about half what a C-130 could do and how much of it is going to be required for support and equipment to keep the troops safe from take off to "landing" is a key issue.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/03/2015 09:22 PM
Just considering the first one then, since they would seem impossible to reconcile,...

Welcome as well :)

Oh not "impossible" of course, what the military wants they will, usually, eventually get but really, really hard to reconcile to say the least :)

Quote
... what they have in mind would seem to be an LH2-fuelled skylon-like carrier, dropping a jet-fuelled lander (since ability to retrieve troops and craft was a desired characteristic), equipped with heat shielding.

Even if a suitable heat shield material was available, the main problem seems to be with the skyon-like carrier - what happens to it after release? If it goes to orbit once-around, then maximum payload for the lander is limited to in the region of Skylon's 15 tons. If it is on a suborbital trajectory, it would re-enter in uncontrolled airspace, and would have to be refuelled at a LH2-capable runway.

Or Tanker and air-to-air refueling. LH2 is still considered (and researched) as a possible aircraft fuel after all. And technically the Skylon could, if suborbital, still retain enough propellant to egress the insertion area and fly to meet such a tanker once all was said and done.

Quote
Build a heat-shielded jet aircraft lighter than 15 tons or maintain a network of LH2-capable runways in hostile regions, neither seems particularly feasible

Well a quick (few minutes) search of NTRS doesn't find what I'm looking for but I'll say the idea has been looked at before. Around 1965 IIRC there was a NASA tech-note on the idea of a orbital or suborbital system that had a reentry vehicle that deployed itself as a Mach-2 fighter or (5 or 6 person IIRC) aircraft once it entered the "area or operations" on arrival. Not in any way as efficient as a purpose built aircraft mind you but do-able as far as the study could tell.

The main problem with SUSTAIN/HOT-EAGLE wasn't that it was not possible but that the idea of inserting a handful (biggest body I ever saw mentioned was a company but the usual group was a squad) of troops with no heavy weapons or support and expecting them to actually DO anything even if no one noticed their arrival.

It was an attempt to replace stealth with speed with the idea that getting the troops to the "trouble" location within minutes of being alerted replacing getting enough troops and equipment to be effective and it didn't make a whole lot of sense from the start.

It's simply not enough force to do any job given that the insertion is so non-stealthy in the first place. A Marine recon squad "ready-to-go" massed more than the notional troops that were supposed to be inserted by the system and THEY get things like SF-stealth helicopters to ride in :)

Again the main issue is even if you got the troops there, intact with minimum or no notice by the locals they are very few and with no real equipment or support and no capability for self extraction or retrieval without additional resources already in place.

We've a thread on the concept IIRC if anyone wants to resurrect it but its been years. (Then again I don't think I ever got to fully explore some of the concepts that came around under that heading. The Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issues :) )

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/03/2015 11:41 PM

In retrospect it would actually have been neat to be able to have the option of supersonic dash into AO, drop to high-subsonic and dump the payload pod, then dash back up to supersonic for egress. But you still have all the issues of inserting into hostile territory with minimum forces that is inherent in the system. Hmmm, something more like a supersonic "Pack-Plane" maybe? (http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane) But the differences between with and without aerodynamics would probably be prohibitive let alone hypersonic and/or suborbital...
This is OT but this idea still looks a sensible notion to maximize the use of expensive assets. I don't think anyone doubts that the ISO container has revolutionized how quickly goods can be be moved as holds no longer need to be individually loaded.
Quote
DROP TROOPERS! :)
U2: Power and air conditioning as far as I know. The constraints were that the equipment had to fit into the bay and work on the provided air and electric.
Which sounds like quite a fair trade off. The SR71 had the detachable nose and various sensors on pallets for the different bays but only the U2 had a full through  bay with no floor.
Quote
Still need a pod or something to hold the troops together unless they individually have some sort of propulsion and guidance. HALO's do something similar from similar altitudes but they have control over their positioning during drop which a supersonic drop would not have. (Imagine your "average" Marine's full kit. Now put a spacesuit on it and him and ask him to perform "simple" maneuvers in the gear. There's a reason the military was interested in the results of high altitude parachuting before Baumgartner did it :) )

And again you get about twice the useful payload to the target with a C-130 than you would with a Skylon under these circumstances...
I also think it's pretty clear that whatever such a vehicle would be it's definitely not a Skylon anymore.

TBH the "simplest" (and I use the word very loosely) would be to fly the Skylon upside down and drop the pot out the way it came in.

Conceptually simple but IRL insane  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 03/05/2015 06:49 AM
UK spaceport selection shortens the short list...

https://www.gov.uk/government/news/industry-backs-governments-spaceport-plans (https://www.gov.uk/government/news/industry-backs-governments-spaceport-plans)

but still aiming at 3000m+ runway. Enough for build+ferry ops?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 03/05/2015 10:33 AM
Approx. 97% off-topic:

http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane (http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane)
This is OT but this idea still looks a sensible notion to maximize the use of expensive assets. I don't think anyone doubts that the ISO container has revolutionized how quickly goods can be be moved as holds no longer need to be individually loaded.

The Packplane concept (and Skylon equivalent) is not analogous to ISO containers. Shipping containers are much smaller than the ships that carry them. Ditto palletised cargo that goes in a shipping container or truck box. The pallets/container are much smaller than the cargo-carrier so that you don't have to worry about the vehicle size. A 2 pallet van, a 2x2x5 pallet truck, a 2x2x10 pallet ISO shipping container...  A single 2-TEU skeleton trailer, a double-stack 2-TEU train carriage, a 36-TEU river barge, a 5,000-TEU Panamax, etc.

But there's no shipping equivalent of the Packplane, where you have a single removable module that becomes a ship's entire hold, even though ships similar to an empty Packplane (http://worldmaritimenews.com/wp-content/uploads/2012/01/China-CMHI-Delivers-Semi-submersible-Heavy-Lift-Vessel-HUAHAILONG.jpg) exist for other purposes, so it's not a structural issue. It would be simple to design a roll-on/roll-off giant freight module for such a ship, but each semi-submersible platform-ship is a unique size, therefore each giant freight module would be bespoke to each ship. You can see where this is going...

Similarly, instead of a Packplane, the air-freight equivalent of ISO containers are the much smaller ULD containers, light pallets with corner cutaways to allow them to stack against curved cargo-holds. (Likewise the US military have standardised on their own "master pallet".) A Packplane type system, OTOH, would be unique to each airframe and wouldn't really save you anything in airport handling. It would just add another step to go wrong, another set of equipment to buy to move the Packplane shell around, in addition to the equipment to load the shell (ULDs/master-pallets, forklifts, etc) and support the loaded and uploaded airframe.

The launch vehicle equivalent of pallets/ULDs/ISOs would be the cubesats and their racks and launchers. If launch vehicles ever became so large that they routinely shipped dozens of full scale (say 5t) satellites in a single launch, then I suspect something like a 2.4x2.4x2.4m "cubesat" standard would evolve. (2.4m/8ft is pretty common for 3+m shrouds, 4.8m/16ft for 5.5m shrouds. Makes a nice 1U, 2U standard.)

Without that, I don't think there's a an advantage in creating a single "Packplane" payload module for a launcher. It doesn't give you "aircraft-like operations". Operationally, it just increases the handling - integrate the payload into the container, then the container into the launcher. So the container is really just wasted payload.  It's different if you were routinely trying to integrate 10-20 separate payloads into a single HLV where a size-standardised payload-rack would improve operations enough to justify the rack's mass.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/05/2015 02:57 PM
Approx. 97% off-topic:

Probably closer to 98%+ but that's a quibble :)

>cut for brevity attempt :)<
Quote
The Packplane concept (and Skylon equivalent) is not analogous to ISO containers. Shipping containers are much smaller than the ships that carry them. Ditto palletised cargo that goes in a shipping container or truck box. The pallets/container are much smaller than the cargo-carrier so that you don't have to worry about the vehicle size. A 2 pallet van, a 2x2x5 pallet truck, a 2x2x10 pallet ISO shipping container...  A single 2-TEU skeleton trailer, a double-stack 2-TEU train carriage, a 36-TEU river barge, a 5,000-TEU Panamax, etc.

But there's no shipping equivalent of the Packplane, where you have a single removable module that becomes a ship's entire hold, even though ships similar to an empty Packplane (http://worldmaritimenews.com/wp-content/uploads/2012/01/China-CMHI-Delivers-Semi-submersible-Heavy-Lift-Vessel-HUAHAILONG.jpg) exist for other purposes, so it's not a structural issue. It would be simple to design a roll-on/roll-off giant freight module for such a ship, but each semi-submersible platform-ship is a unique size, therefore each giant freight module would be bespoke to each ship. You can see where this is going...

Similarly, instead of a Packplane, the air-freight equivalent of ISO containers are the much smaller ULD containers, light pallets with corner cutaways to allow them to stack against curved cargo-holds. (Likewise the US military have standardised on their own "master pallet".) A Packplane type system, OTOH, would be unique to each airframe and wouldn't really save you anything in airport handling. It would just add another step to go wrong, another set of equipment to buy to move the Packplane shell around, in addition to the equipment to load the shell (ULDs/master-pallets, forklifts, etc) and support the loaded and uploaded airframe.

The launch vehicle equivalent of pallets/ULDs/ISOs would be the cubesats and their racks and launchers. If launch vehicles ever became so large that they routinely shipped dozens of full scale (say 5t) satellites in a single launch, then I suspect something like a 2.4x2.4x2.4m "cubesat" standard would evolve. (2.4m/8ft is pretty common for 3+m shrouds, 4.8m/16ft for 5.5m shrouds. Makes a nice 1U, 2U standard.)

Without that, I don't think there's a an advantage in creating a single "Packplane" payload module for a launcher. It doesn't give you "aircraft-like operations". Operationally, it just increases the handling - integrate the payload into the container, then the container into the launcher. So the container is really just wasted payload.  It's different if you were routinely trying to integrate 10-20 separate payloads into a single HLV where a size-standardised payload-rack would improve operations enough to justify the rack's mass.

In general I agree.

The "Packplane" concept lives a proof of the "Bee-plane" (http://www.bee-plane.com/) but the issue is the fact that you have to make each "pod" the equivalent of an aircraft fuselage no matter WHAT the cargo is. That costs. At the time the Packplane was proposed you could almost get away with a "pod" being nothing more than a cheap metal tube on some car-wheels and a roof mounted hard point attachment. All well and good but as someone who's spent a great deal of time on board NORMAL transport aircraft with minimum insulation and sound proofing, (it looks funny but you can tell the folks going home in the desert because they show up for on the flight line in thermal underwear and parkas and are happy about it :) ) while it MIGHT work for the military for normal passenger or freight services you need more structure and support. And your cost ramps up fast. Plus there is the drag and other aerodynamic issues and the fact that you "core" aircraft is ONLY usable with the pod system and in the end the effort doesn't "seem" worth it.

Note the "quotes" there :) As shown by the Bee-Plane being only the latest example the idea won't go away and really, from studies done such a "pod" system might in fact be the future of civil passenger aviation. Someday :)
But the process isn't really applicable for space flight, not anytime soon at least.

Now I've seen some concepts (and patents thereof :) ) that involve hooking together actual ISO containers either onto fuselage or making a fuselage out of them and most look pretty dodgy for "regular" use but as Paul451 notes you COULD just simple stuff ISO containers into a detachable fuselage pod and call it done but it will not BE an "ISO container" aircraft anymore than a "container" ship is made out of containers :)

Standardized "Payload" pods though could be useful and probably will be but not any time soon I think. That kind of "containerization" of cargo takes a certain level of both throughput for a transportation system AND at least some degree of "standardization" of cargo loads as well. We're not there yet with space transport as no two satellites are exactly the "same" enough to allow a single standardized payload attachment and support system.

Except as noted (again) by Paul451; cubesats.

I don't think it's too far fetched to imagine that once access frequency goes up and costs come down that a similar architecture for larger satellites won't spring up and lead to a "standardized" payload module and interfaces.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Archibald on 03/06/2015 05:42 AM
Quote
The Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issues

WTF ??!!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 03/06/2015 03:30 PM
Quote
The Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issues

WTF ??!!

Impressive :) It only took three days for someone to catch that one. Yup, was a suggested approach I read on an engineering forum. Not QUITE as crazy as it sounds but not far off :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: tea monster on 03/06/2015 06:13 PM
Wow! Lock, n load, n launch soldier!

It would be great to be the only helo pilots on the planet with astronaut's wings!  ;)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Archibald on 03/08/2015 07:52 AM
Quote
The Falcon-9 with the with an aeroshell that landed a folded up Blackhawk and crew/soldiers was, I thought a nice attempt at addressing the issues

WTF ??!!

Impressive :) It only took three days for someone to catch that one. Yup, was a suggested approach I read on an engineering forum. Not QUITE as crazy as it sounds but not far off :)

Randy

Do you have a link to that "engineering forum" ?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: tatarana on 03/10/2015 11:05 PM
As was said several times in this and the previous 4 threads, SABRE engine seems to scale down badly due to problems with the LH2 pump.
BUT... ???
What are the perspectives to scale it up, if (normal size) SABRE and Skylon fulfill its promises ?
There would be any limits to build a larger Skylon to send heavier payloads to orbit,
as for example, doubling payload to 30 tonnes ? An obvious one is the runway reinforced concrete pavement, but there are any fundamental limits ?
Also, what would be  possible economic reasons to scale it up ?

Tatarana
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 03/11/2015 03:19 AM
http://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577

Quote from: Hempsell
We have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).

If the market for large payloads gets to the point where a bigger vehicle makes sense, someone will design one.  Kinda like how locks on the St. Lawrence Seaway have been replaced with bigger ones multiple times as shipping outgrew them.

Alternately, if someone with big plans and deep pockets decides they want a super heavy Skylon-type vehicle for their own purposes, they might pay to get one built; NASA and SpaceX are both doing this already with more conventional launcher technology.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/12/2015 10:05 PM
If the market for large payloads gets to the point where a bigger vehicle makes sense, someone will design one.  Kinda like how locks on the St. Lawrence Seaway have been replaced with bigger ones multiple times as shipping outgrew them.
Interesting analogy.

It's an interesting point that those locks were the right size for the bulk of the traffic at the time they were built, but really big ships would have to take the long way round.

Skylon won't deliver the biggest payloads to orbit but it will deliver the bulk of payloads. Will that matter? Time will tell.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: tatarana on 03/14/2015 03:40 PM
http://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577

Quote from: Hempsell
We have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).

If the market for large payloads gets to the point where a bigger vehicle makes sense, someone will design one.  Kinda like how locks on the St. Lawrence Seaway have been replaced with bigger ones multiple times as shipping outgrew them.

Alternately, if someone with big plans and deep pockets decides they want a super heavy Skylon-type vehicle for their own purposes, they might pay to get one built; NASA and SpaceX are both doing this already with more conventional launcher technology.

93143, thanks a lot for the refresher.  During  thread 1  I was still not able to follow the subtle points of arguments about space markets.  Skylon threads also have this nice characteristic of being a teaching tool.

JS19, your argument about 'bulk cargo' makes a lot of sense.
Question: if you take out the satellite market, what other bulk cargo could there be? Fuel to depots ?
Space station's construction components by other nations ?

Some time ago I read a nice paper about space mining, NEAR EARTH OBJECTS AS RESOURCES FOR SPACE INDUSTRIALIZATION, by MARK SONTER. He makes a strong argument by examining and comparing the mining industry on Earth with space use. One of his conclusions was that it could be possible to build a space craft mining unity that would weight something like 5 metric tonnes. I wonder if something like this could be crammed inside a Skylon  standard cargo module, perhaps with a suplementary deep space propulsion unit launched separately (perhaps  electric propulsion like Vasimr, that uses argon and hydrogen that could be mined and replenished  in situ). This subject has ever surfaced on Skylon threads ?

Tatarana
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/14/2015 04:59 PM
JS19, your argument about 'bulk cargo' makes a lot of sense.
Question: if you take out the satellite market, what other bulk cargo could there be? Fuel to depots ?
Space station's construction components by other nations ?
Welcome to the site.

In hindsight "bulk" might not have been the best word. Certainly Skylon can cover the majority of the known and expected payload growth in those known markets. That said the aggregate mass these missions put up easily exceed any single payload over time.

Actual bulk payloads are either things that need to be delivered in large volumes (or masses) or that cannot be sub divided. The former would be propellants, water, toilet tissue, ready meals. The latter would be things like large nuclear reactors or telescopes.

REL have done various studies to ensure that their vehicle can accommodate tasks as diverse as launching satellites to GEO, probes to other planets and their moons (while retaining the upper stage) and full blown Mars missions.

Quote
Some time ago I read a nice paper about space mining, NEAR EARTH OBJECTS AS RESOURCES FOR SPACE INDUSTRIALIZATION, by MARK SONTER. He makes a strong argument by examining and comparing the mining industry on Earth with space use. One of his conclusions was that it could be possible to build a space craft mining unity that would weight something like 5 metric tonnes. I wonder if something like this could be crammed inside a Skylon  standard cargo module, perhaps with a suplementary deep space propulsion unit launched separately (perhaps  electric propulsion like Vasimr, that uses argon and hydrogen that could be mined and replenished  in situ). This subject has ever surfaced on Skylon threads ?
The current Skylon revision is for a payload of 15 tonnes in a payload bay about 13m long and close to 5m in diameter. It's not that cramped, although the price would be set by the Skylon operators.

It should be big enough to accommodate such a payload.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 03/15/2015 09:57 PM
the issue with Skylon and asteroids mining is actually that miners expect to get most of their initial revenue from basic commodities, like water, which value per kg in space equals their launching cost per kg.

Skylon kills this business case by providing cheap access. it brings the value of water down from 14k $ per kilo, to 600 $ per kilo.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hanelyp on 03/16/2015 04:44 AM
But bringing down launch costs also brings down the expense to deploy asteroid mining equipment.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 03/16/2015 06:35 AM
Skylon kills this business case by providing cheap access. it brings the value of water down from 14k $ per kilo, to 600 $ per kilo.

Bringing down the cost of access to LEO increases the number of users who can justify access, which increases the number of users who can then justify BEO missions. (Even if its primarily university/govt research.) That creates a much larger initial market for water/air/fuel delivered to BEO facilities from local sources. That then lowers the cost of operations BEO, and increases the number of users who can justify going a step further out.

Additionally, the increase in users in LEO and BEO pays for the development of more HSF and robotic technology. That lowers the start-up cost for asteroid (and lunar-pole/Mars moons/etc) miners.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 03/18/2015 07:50 AM
if demand for space is sufficiently elastic,yes.
But we don't know it yet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 03/18/2015 03:47 PM
Apparently Jeremy Nickless gave a presentation at NSSC 2015 at the beginning of the month,


http://ukseds.org/nssc2015/?p=speakers

Anyone attend?

Anyway there are some slide pictures on twitter from it and this one seemed new to me:

https://twitter.com/Astro_Mona/status/572037016537444352/photo/1

I read it as saying in airbreathing mode SABRE consumes 900t of air for a deltaV of 5.2km/s, which is data point for SABRE 4 performance I don't think we had before.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 03/18/2015 10:15 PM
I'm seeing "Rocket ΔV=6.2km/s", which sounds about right given that C1 seems to have been about 6.3 km/s.  Airbreathing should be around 3.5-4 km/s if it's anything like C1, which according to my calculations was about 3.7 km/s.

900 tonnes of air is less than the 1250 tonnes or so C1 took in, but that includes the bypass flow; scaling the 530-tonne core flow by the increased mass of D1 still gives me only 650 tonnes.  If the new engine is substantially different, perhaps with a different trajectory-coupled-optimum thrust level, I can see how the number might have changed.  Or maybe it's per engine; one SABRE 3 seems to use close to 800 tonnes when scaled to the mass of D1.  Alternately, I could have done my math wrong; it's happened before...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Soundbite on 03/20/2015 06:44 PM
Just thought you might all be interested in the latest press release from reaction engines http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html).

Alan Bond is going to concentrate on being Chief Engineer and pass the reigns of Managing Director to a new appointee.

Maybe they are anticipating tougher competition ahead?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 03/20/2015 08:32 PM
The fact that they've hired the former Chief Engineer for Technology and Future Programmes with Rolls-Royce Civil Large Engines to be the new MD seems to me to be very positive news. And importantly an addition that potential investors would welcome.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/20/2015 10:08 PM
Just thought you might all be interested in the latest press release from reaction engines http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html).

Alan Bond is going to concentrate on being Chief Engineer and pass the reigns of Managing Director to a new appointee.

Maybe they are anticipating tougher competition ahead?
No, it means he wants to focus on the technology development.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 03/20/2015 10:22 PM
The fact that they've hired the former Chief Engineer for Technology and Future Programmes with Rolls-Royce Civil Large Engines to be the new MD seems to me to be very positive news. And importantly an addition that potential investors would welcome.
Quote
Mark Thomas, CEng, FRAeS

Mark is Chief Engineer for Technology and Future Programmes in the Rolls-Royce Civil Large Engines Business. He leads the Engineering teams responsible for the exploration and concept design of next generation propulsion systems; also the execution of system level demonstrators to deliver innovative technologies meeting future product requirements.

In 2014 Mark will celebrate 25 years with Rolls-Royce, joining the Company in 1989 as a sponsored Undergraduate trainee before completing an Engineering degree at Queens’ College, Cambridge University.

Mark’s career started in the Rolls-Royce Defence Aerospace Business and he has completed a variety of Engineering and Management roles located in the UK and Germany.

Notable roles have included Chief Development Engineer for the EJ200 (Typhoon) Engine, Programme Executive for UK Defence Research and Technology, Chief Engineer for the EJ200 (Typhoon), RB199 (Tornado) & Adour (Hawk/Jaguar) engine programmes, and Technical Director of the Eurojet Turbo GmbH consortium based in Munich.

As a Chief Engineer in Defence, Mark was responsible for the support of around 3,000 engines worldwide with 25 Military Operators ranging from the US Navy to Royal Australian Air Force.

In 2009 Mark moved to the Civil Aerospace Business in Derby to take up the role of Chief Engineer for the Trent 900 (Airbus A380), leading the team during an especially challenging three year period for the programme, working closely with Airbus and Airline Customers.

Mark is a Chartered Engineer, Fellow of the Royal Aeronautical Society and also a Governor of a flourishing Engineering Academy. He mentors a number of engineers in Rolls-Royce and is a key member of the Rolls-Royce Senior Engineering Leadership team.

Mark is married with two teenage sons and one daughter and lives in Leicestershire. Outside work he enjoys skiing, travel and reading.
- See more at: http://aerosociety.com/Events/Event-List/1577/Rolls-Royce-future-developments-in-engine-technology#sthash.Zx2ceu45.dpuf

I think this  answers rather handily the questions of whether REL is a serious concern and whether there is anyone with real experience working there.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/21/2015 12:12 AM
I think this  answers rather handily the questions of whether REL is a serious concern and whether there is anyone with real experience working there.
In theory yes, in practice no.  :(

Skeptics will note that no one would walk away from a 25 year career with a company without substantial motivation to do so. 

Doubters will continue to insist that only a full size flight vehicle returning from orbit, having deployed a full size payload, will adequately demonstrate that it can work.

Then they will (grudgingly) admit it works but insist that that REL will never sell any.  :(

I'll note that substantial investors in new companies often require Board level representation as a condition of that investment.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 03/21/2015 01:02 PM
I think this  answers rather handily the questions of whether REL is a serious concern and whether there is anyone with real experience working there.
In theory yes, in practice no.  :(

Skeptics will note that no one would walk away from a 25 year career with a company without substantial motivation to do so.

They can't question the experience though.

Another interesting possibility struck me: I used to work for a big Finnish phone maker and when a fairly high up executive arrived from a competitor to become CEO it was a prelude to a takeover.  ..... :-)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 03/21/2015 01:41 PM
When someone with the credentials of Mark Thomas comes in from a company as important as RR then there's something serious afoot.

It's not clear if he's maintaining a position at RR?  If he still maintains some position at RR then that has implications for what's going on with regards the latest announcement. As suggested above, perhaps there's going to be a take-over or collaboration of some sort.

If he's severing his ties with RR then that also tells us something. He will have had a look at all the insider information before he makes a career move like that. He won't want to tarnish his reputation and get on-board with a project that he thinks won't succeed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 03/21/2015 03:45 PM
I think this  answers rather handily the questions of whether REL is a serious concern and whether there is anyone with real experience working there.
In theory yes, in practice no.  :(

Skeptics will note that no one would walk away from a 25 year career with a company without substantial motivation to do so.

They can't question the experience though.

Another interesting possibility struck me: I used to work for a big Finnish phone maker and when a fairly high up executive arrived from a competitor to become CEO it was a prelude to a takeover.  ..... :-)

I used to think RR might take REL over at some point, but now I just wonder why they haven't already.
Given the number of ex RR employees at REL from the top down it's effectively a RR spinoff anyway.
At this point in time REL has basically proved their major engine innovation and everything to come over the next 3-4 years is engine integration work that could benefit greatly from the massive resources of RR as well as RR's great experience negotiating ITAR and being a major US defence contractor. I'm sure REL's IP could be worth many the cost of the company to RR when applied across RR's product line.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 03/21/2015 06:47 PM

I think this  answers rather handily the questions of whether REL is a serious concern and whether there is anyone with real experience working there.
In theory yes, in practice no.  :(

Skeptics will note that no one would walk away from a 25 year career with a company without substantial motivation to do so.

They can't question the experience though.

Another interesting possibility struck me: I used to work for a big Finnish phone maker and when a fairly high up executive arrived from a competitor to become CEO it was a prelude to a takeover.  ..... :-)

I used to think RR might take REL over at some point, but now I just wonder why they haven't already.
Given the number of ex RR employees at REL from the top down it's effectively a RR spinoff anyway.
At this point in time REL has basically proved their major engine innovation and everything to come over the next 3-4 years is engine integration work that could benefit greatly from the massive resources of RR as well as RR's great experience negotiating ITAR and being a major US defence contractor. I'm sure REL's IP could be worth many the cost of the company to RR when applied across RR's product line.

Be interesting to see if a takeover by RR is in the offing, I'm almost surprised this hasn't already happened. Perhaps they are waiting for the AFRL to report back to find out if there is the possibility of a valuable future customer for the technology.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 03/21/2015 08:39 PM


I used to think RR might take REL over at some point, but now I just wonder why they haven't already.
.....

Be interesting to see if a takeover by RR is in the offing, I'm almost surprised this hasn't already happened. Perhaps they are waiting for the AFRL to report back to find out if there is the possibility of a valuable future customer for the technology.
....

I have no expertise to base this on but it would surprise me a bit given the immensely competitive market that RR are in.  It seems to me like a fight to the death against superb competitors with possibly better subsidies. If I was them I'd want to spend every ounce of my R&D effort on getting some advantage in the current jet engine battles.   I've heard speculation that RR might even be concerned that SABRE would divert talent away that it needs.  This could be an example.

I went to a lecture not long ago about RR research areas and it spent a lot of time on the Ultrafan and an explanation of the market and how it works - engines sold before they are even designed.  To me it sounded like the sort of fierce competition that tends to make people focus on improving widget X instead of inventing totally new ones and hoping to sell them - simply because any loss, any mistake could hand billions of dollars of future revenue to a competitor.

Their long term worries, according to the speaker (John Whurr), are that distributed propulsion will make it more sensible for the airframer to also build the engines, since they will be so intricately integrated, and that there wont' be the option of buying from a range of engine manufacturers.  i.e. that their raison d'etre will disappear.

So SABRE seems like rather a diversion to me.....but.... he did mention that they do some degree research into cryogenic engines, hydrogen as a fuel (my terminology is probably all wrong).  Anyhow I pricked my ears up because that sounded a little like SABRE.

To me it seems more logical that RR might have an interest in using precoolers for engines other than SABRE. It would certainly be a trick that others might find hard to copy.

I have no special knowledge.  I'm speculating - which is more fun the less one actually knows :-).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/22/2015 08:45 AM
Their long term worries, according to the speaker (John Whurr), are that distributed propulsion will make it more sensible for the airframer to also build the engines, since they will be so intricately integrated, and that there wont' be the option of buying from a range of engine manufacturers.  i.e. that their raison d'etre will disappear.
"Distributed propulsion"

http://en.wikipedia.org/wiki/Distributed_propulsion

What specifically did he mean by the term?
Quote
So SABRE seems like rather a diversion to me.....but.... he did mention that they do some degree research into cryogenic engines, hydrogen as a fuel (my terminology is probably all wrong).  Anyhow I pricked my ears up because that sounded a little like SABRE.

To me it seems more logical that RR might have an interest in using precoolers for engines other than SABRE. It would certainly be a trick that others might find hard to copy.
Then you'd be talking about REL's work on the EU funded LAPCAT project for M5 airliners.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 03/22/2015 01:10 PM
Their long term worries, according to the speaker (John Whurr), are that distributed propulsion will make it more sensible for the airframer to also build the engines, since they will be so intricately integrated, and that there wont' be the option of buying from a range of engine manufacturers.  i.e. that their raison d'etre will disappear.
"Distributed propulsion"

http://en.wikipedia.org/wiki/Distributed_propulsion

What specifically did he mean by the term?

As I understood him, it meant all sorts of combinations of propulsors, engines and batteries ranging from engines with mechanical transmission to their distributed propulsors to fully electric aircraft with lots of battery storage.

RR has to study these to see if there's a place for it in any of them and to know when and what moves to make (my interpretation).



So SABRE seems like rather a diversion to me.....but.... he did mention that they do some degree research into cryogenic engines, hydrogen as a fuel (my terminology is probably all wrong).  Anyhow I pricked my ears up because that sounded a little like SABRE.

To me it seems more logical that RR might have an interest in using precoolers for engines other than SABRE. It would certainly be a trick that others might find hard to copy.
Then you'd be talking about REL's work on the EU funded LAPCAT project for M5 airliners.

I found this quote from a Reaction Engines Q&A on "The Engineer"'s website:  http://www.theengineer.co.uk/aerospace/in-depth/skylon-and-sabre-your-questions-answered/1014164.article

Quote
Other market applications for the technologies that we have been developing include but are not limited to improving the efficiency of ground-based heat engine cycles for power production, reducing infra-red signatures in engine exhausts, increasing the performance of automotive engines through improved waste heat recovery, higher performing air-conditioning and refrigeration systems for civil and industrial applications such as for LPG shipping, and increasing the efficiency of cooling for electrical and nuclear power systems.

So I can imagine those precoolers being of interest e.g. to the Trident "successor" submarines or possibly to the company that RR invested in which wants to make small modular nuclear reactors for civil applications - so you don't have  such a huge capital cost before you can start generating - you can grow bit by bit and upgrade bit by bit too.  You can also obviously see the interest for LO aircraft - like FCAS.  etc etc.  It seems odd that something could help the efficiency of ground based automotive engines but have no value to aircraft engines at all, at least in theory if weight was not a problem and cost could be reduced.  So I am wondering if Mach 5 Lapcat isn't a sort of distraction from some other more conventional use for precoolers?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 03/22/2015 09:15 PM
Mark Thomas is an experience guy.

It will be interesting to see if he makes any big changes, like you know hire a PR person that writes regular updates about the project :P

I never really heard anything from Rolls Royce that they are looking to make a major entry into a new market and the acquisition of REL would be a major move for them But it they are losing talent to REL, RR is probably looking at their options.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/24/2015 09:24 AM
As I understood him, it meant all sorts of combinations of propulsors, engines and batteries ranging from engines with mechanical transmission to their distributed propulsors to fully electric aircraft with lots of battery storage.
RR provide a lot of the small lift jet engine for various VTOL concepts in the 1960s.

In the end only the Harrier entered service. Given Boeing couldn't even face the idea of a blended wing body airliner for the 787 this is decades away at least.
Quote
It seems odd that something could help the efficiency of ground based automotive engines but have no value to aircraft engines at all, at least in theory if weight was not a problem and cost could be reduced. 
What REL have been saying is that this tech is very difficult to retrofit to existing jet engines as they were built to use (and need) certain flows, pressures and temperatures. Pre coolers can change the game if built into a new design from day one.
Quote
So I am wondering if Mach 5 Lapcat isn't a sort of distraction from some other more conventional use for precoolers?
When someone puts cash on the table to investigate a long term idea versus various ideas that have put no money on the table it's never a distraction. :(

BTW while a real M5 airliner is probably decades away that programme let REL investigate contra rotating turbines (now SOP on the larger Trents but when this started only seen on the Olympus used in the Harrier) and low NOx combustion which is expected to create 1% of the NOx of other H2 combustors.

Useful things to have in the too box if you're planning to build a big low weight LH2 engine.  :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: topsphere on 03/25/2015 12:01 PM
I'm going to a talk entitled "Precooled propulsion – key to 21st century spaceflight" by Richard Varvill of REL tomorrow. I will try and either record audio or make notes to post here, but does anyone have any burning questions that I might attempt to put to him?

Edit - Just realised tomorrows talk will be broadcast live - http://www.develop3dlive.com/d3d-live-stream-gmt/   - starting at ~14:20 GMT

I'll still try and make notes but if people want to better understand what Mr Varvill will be saying it may be better to watch his talk.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 03/25/2015 01:55 PM
I'm going to a talk entitled "Precooled propulsion – key to 21st century spaceflight" by Richard Varvill of REL tomorrow. I will try and either record audio or make notes to post here, but does anyone have any burning questions that I might attempt to put to him?

Off the top of my head these are my questions:
 
   1) Does the SABRE 4 cycle use hydrogen recycling to achieve it's high efficiency? (He wont answer but may have a tell that gives it away)

  2) Does the SABRE frost prevention work by turning off precooler module pairs in a rotational cycle around the      precooler allowing the channels to be constantly blown clear? (ditto)

  3)Has the SABRE 4 been definitively chosen as the production engine yet?

  4)Will the final production model be a Skylon E type?

  5)What does he think of the UK Spaceport shortlist and whether he thinks it's important that the selected site be   capable of being expanded to support orbital vehicles in the long term, such as Skylon, or is it more important to be close to the  existing aerospace economic base?

  6)Would REL every consider a buy out from Rolls Royce?

  7)What's the status of Valkyrie, the nacelle test vehicle et al?   

  8)Has the USAF CRADA experience been a positive one given REL's justified fear of ITAR entanglement?

  9)Roughly what percentage of future Skylon production will take place in the UK, i.e. parts production, assembly, etc?

  10)The city of London has a reputation for being poor at financing long term infrastructure projects, has REL found that problem  in relation to Skylon?


Most of these questions probably aren't very answerable though.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 03/28/2015 09:51 PM
Going back to Mark Thomas, Rolls Royce and the possibility of other light weight heat exchanger applications, in look into Thomas I found this presentation:

http://aerosociety.com/Assets/Docs/Events/746/GBD_Propulsion_211014_RR_1.pdf

Which led to this one:

http://www.newac.eu/uploads/media/NEWAC_Technologies.pdf

Where the introduction of a heat exchanger between bypass air and compressed air situated between the low pressure and high pressure compressors is used to gain a higher overall pressure ratio. The heat exchanger used is a titanium corrugated lattice but it would be interesting to know how its efficiency compares to SABRE's precooler.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 03/29/2015 09:56 AM
I'm going to a talk entitled "Precooled propulsion – key to 21st century spaceflight" by Richard Varvill of REL tomorrow. I will try and either record audio or make notes to post here, but does anyone have any burning questions that I might attempt to put to him?

Edit - Just realised tomorrows talk will be broadcast live - http://www.develop3dlive.com/d3d-live-stream-gmt/   - starting at ~14:20 GMT

I'll still try and make notes but if people want to better understand what Mr Varvill will be saying it may be better to watch his talk.
This looks interesting but I missed it.

Is there any idea when they will post this years videos?

Failing that can you give a brief outline of key points?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 04/01/2015 12:32 PM
Re Richard Varville's talk at Develop3D.  I asked them on their Facebook page about the video and they answered:
Quote
Develop3D Yep, all the videos from #D3DLive will be posted online soon. Stay tuned for the release announcement in the coming weeks
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/01/2015 01:28 PM
Re Richard Varville's talk at Develop3D.  I asked them on their Facebook page about the video and they answered:
Quote
Develop3D Yep, all the videos from #D3DLive will be posted online soon. Stay tuned for the release announcement in the coming weeks
I'll have to look out for that.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: topsphere on 04/01/2015 01:58 PM
I'm going to a talk entitled "Precooled propulsion – key to 21st century spaceflight" by Richard Varvill of REL tomorrow. I will try and either record audio or make notes to post here, but does anyone have any burning questions that I might attempt to put to him?

Edit - Just realised tomorrows talk will be broadcast live - http://www.develop3dlive.com/d3d-live-stream-gmt/   - starting at ~14:20 GMT

I'll still try and make notes but if people want to better understand what Mr Varvill will be saying it may be better to watch his talk.
This looks interesting but I missed it.

Is there any idea when they will post this years videos?

Failing that can you give a brief outline of key points?

I'm afraid I forgot to bring a pen and paper :(

It was a good talk, nothing that seemed a new revelation, but then I haven't been following the technical development too closely.

He started off very generally, talking about justifying re-use vs expendable, background and history (HOTOL/work at rolls-royce), then background of skylon, went into quite a bit of detail about the mechanics of the SABRE engine, then current status of REL and future applications.

I'll leave you to pass judgement until you've seen the video, though.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/02/2015 09:32 AM
I'm afraid I forgot to bring a pen and paper :(
Not a problem. We'll wait for the videos.
Quote
It was a good talk, nothing that seemed a new revelation, but then I haven't been following the technical development too closely.

He started off very generally, talking about justifying re-use vs expendable, background and history (HOTOL/work at rolls-royce), then background of skylon, went into quite a bit of detail about the mechanics of the SABRE engine, then current status of REL and future applications.

I'll leave you to pass judgement until you've seen the video, though.
It's the current status part that's likely to change over time.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/03/2015 06:14 AM
Below are some thoughts on Skylon areodynamics, and safety. I could be making some incorrect assumptions here, so am happy to hear corrections.

Much has been made of how the Skylon aerodynamics are much improved over HOTOL due to the new airframe configuration: it now requires much less trim even as the fuel tanks empty and it transitions to rocket power.

That’s a welcome advance, but it seems to me that re-entry could still be challenging for a Skylon shape - at least more challenging than with capsules. I certainly believe that when flying during ascent it will be stable and easy to trim - those canards are far forward of the center of mass & pressure and so up to the task.

But the early stages of atmospheric entry are not at all like climbing, winged flight. With the nose high, the wings are essentially drag devices, and inasmuch as Skylon is an aircraft it’s in a free-fall stall. Unlike a capsule, the Skylon shape is complex and extends far away from the center of lift, so any net forces from the extremities are on long moment arms and need to be dealt with. And unlike a capsule it will not be passively stable. That said, my guess is that Skylon must be actively ‘flown' on the canards during re-entry in the period when the atmosphere overpowers the RCS, and before Skylon is flying forwards - on wings like an aircraft.

The Skylon images indicate that there are elevons on the wings, but during high-alpha entry they seem close to the center of lift and so would not offer as much leverage as the canards (or the equivalent body flap at the rear of the space shuttle orbiter).

If I’m right, failure of the canard actuator would be disastrous. I don't believe a thin movable aero surface like that has been flown from orbital speed through entry heating, and to sea level - the most recent public documents on Skylon state that the canards will need to be actively cooled.

I'm sure the cooling mechanism and the actuators will be expertly designed, but with a spacecraft that's expected to fly many times, we can worry about what happens when statistically unlikely events occur. I’d love to hear how REL would respond to questions about cooling mechanism and/or actuation mechanism failures.

----------------------------------

Since we’re not likely to hear from REL on these things, let’s do some speculating:

+ The canards could be designed to require active cooling under normal conditions, but survive (need replacement) if it fails.
+ A second redundant pair of canards could be added to the rear of the fuselage, i.e. a tailplane/horizontal stabilizer.

If you were to add those additional aerosurfaces you get some other benefits too. It would give greater control authority which could conceivably help the self-ferry case on shorter runways: the additional surfaces would allow the nose to be pulled up earlier, putting more air under the wings leading to an earlier take-off. Similarly, all four surfaces could serve as air-brakes after landing, reducing roll-out distance.

And while we’re talking about self-ferry, if the engines could be gimbaled above the horizon, that too would help pick up the nose as the engines are behind the landing gear. I suppose it would also mean less rocket blast hits the runway which is a good thing.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/04/2015 04:00 PM
Re the need to cool the canards:

It turns out BOR-4 used a vapor cooling system - a passive one - for its fins:

Quote
The structure of the heat shield of the wings was different from the remainder of the body. Indeed, because of the aerodynamic profile of the lifting body the wings were thin and could not support the heavy tiles. The interior cavity of wing was filled by a porous matter (the same as felt which holds the tiles on the fuselage) and impregnated with a special composition based on water. Thus, the vapor was used for cooling the structure during the intense heating on the return trajectory.
From: http://www.buran-energia.com/bor/bor-desc.php

So something like that could be used for Skylon. Obviously the advantage of a passive system is you don't need to worry about what happens when the coolant circulation system fails.

And perhaps you could do both: an active system that, when failed, leaves enough residual vapor/transpiration capacity to survive one entry?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/04/2015 11:36 PM
Re the need to cool the canards:

It turns out BOR-4 used a vapor cooling system - a passive one - for its fins:
So something like that could be used for Skylon. Obviously the advantage of a passive system is you don't need to worry about what happens when the coolant circulation system fails.

And perhaps you could do both: an active system that, when failed, leaves enough residual vapor/transpiration capacity to survive one entry?
REL probably chose water cooling over something like heat pipes because the system has been flight tested at least once.

There is a declasified test report for a warehead test in the late 70s or early 80s on DTIC about it. Since it was a warhead design the structure was "thin" as they don't aim to decellerate much before detonation.

People call this "active" cooling but there is typically no actual "pump" involved. It's just water being allowed to boil and heat out of the surfaces.

RCC is good to 3000c in vacuum. it's likely to be SiC coated, like the Shuttle nose and leading edge sections, so good to somewhere like 1500 to 1800c without cooling.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Space OurSoul on 04/06/2015 04:24 PM
the additional surfaces would allow the nose to be pulled up earlier, putting more air under the wings leading to an earlier take-off. Similarly, all four surfaces could serve as air-brakes after landing, reducing roll-out distance.

And while we’re talking about self-ferry, if the engines could be gimbaled above the horizon, that too would help pick up the nose as the engines are behind the landing gear. I suppose it would also mean less rocket blast hits the runway which is a good thing.

Early rotation: Once you're out of ground effect, I think the design would already be at optimal angle-of-attack for the take-off airspeed regime.

High gimbal: That would represent a new stress dynamic for transmitting thrust to the airframe: Now a shear on the engine itself and a torque on the wings. So a bigger mass penalty in the structure? And air is a capricious thing: I think you'd still want thrust running through the center-of-mass or who knows what-all instabilities you'd run into in the turbulent lower atmosphere (where, granted, aero surfaces are good at helping (although less so at low airspeeds)).

The effect of either approach is to trade higher drag for increased lift. I'm not sure that lift is the right variable to optimize for: I would have thought that optimizing for early acceleration (i.e _lower_ drag) would actually be what you want. (The way I though of it, probably simplistically, is that if you had high lift but traded a lot of fuel to get it, all you'd end up with would be a slightly less-fueled ship a few meters higher off the ground, going at the same speed. All your fuel's energy went into adding turbulence to the atmosphere.)

But I realize that it's a very complicated optimization problem: Less time on the runway may well translate to mass savings in the undercarriage, less brake-cooling water to carry, etc. And if you really can get into ground-effect flight earlier, it might be a very efficient regime in which to accelerate.


A few threads back I floated the notion of dorsal re-entry. Imagine a configuration like SR-71 with two vertical stabilizers, one at each wingtip and no canard. It rolls down the runway "upside-down" with the stabilizers doubling as undercarriage. The payload doors are underneath at this time, and the top is unbroken TPS out of FOD danger from objects on the runway. During re-entry, the ship lies on its back, stabilizers sticking up out of the heating. It then flips over, probably subsonic, and lands like it takes off.
The relevance to the current discussion is that you now have two configurations (albeit, obviously, tightly linked!) that can be optimized: the take-off can favor low-speed aerodynamics, and the re-entry can favor dynamic stability.
While this approach might help for roll stability, I'll admit it doesn't much address the point that you raised which I think was focused on pitch. It does seem like some kind of aero-surface, ideally far from the center of lift, would help for that flight regime you mentioned.

 

All these thoughts make me realize, yet again, what a difficult optimization problem Skylon represents. I wonder if REL ever had a bash at "genetic" programming: iterating randomly tweaked designs, simulate over the whole mission, repeat.

But I talk too much.
</uninformed guesses>
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/06/2015 10:29 PM
All these thoughts make me realize, yet again, what a difficult optimization problem Skylon represents. I wonder if REL ever had a bash at "genetic" programming: iterating randomly tweaked designs, simulate over the whole mission, repeat.
This is the challenge to building Skylon. Any changes you make to improve some part of the trajectory have to either improve the whole of the trajectory or leave the rest unaffected.

Once you realize this you realize just how tricky it is to make changes to the design and how carefully the REL team have had to think this through.

In one of the periodic update reports REL have submitted to IAC they mentioned the use of Monte Carlo simulation methods to refine the design.

The upside is this task is still simpler than the various attempts at SCramjet powered vehicles that incorporate the inlet into the front of the vehicle.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 04/06/2015 11:38 PM
Using the dorsal surface as the heatshield has merits, but necessitates the "barrel roll of death", as opposed to the "swoop of death" required for nose first reentry VTVL SSTO's. I think an unbroken TPS is preferable, and makes certain other things (beamed thermal propulsion receiver) easier to integrate into the airframe. Ventral opening payload bay also allows easy payload load/unload via a scissor lift cargo transfer vehicle/pit, as opposed to a gantry crane. The kicker is payloads and airframe have to handle long durations in both flipped and unflipped flight modes, which makes systems design more complicated. I suppose doing the flip always clockwise, and the unflip counterclockwise, might make it a bit easier, especially with a passenger module and the rotating seat frames.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/07/2015 05:00 PM
Below are some thoughts on Skylon areodynamics, and safety. I could be making some incorrect assumptions here, so am happy to hear corrections.

Much has been made of how the Skylon aerodynamics are much improved over HOTOL due to the new airframe configuration: it now requires much less trim even as the fuel tanks empty and it transitions to rocket power.
I've read your posts a few more times and I'm still not clear what  you're worried about. Is it a pitch failure? Is it a roll failure?

BTW The Shuttle control system also had a period its control surfaces were not fully effective and RCS thrusters were used together with the aero surfaces. Later development programmes found ways to make more effective use of the control surfaces (differential use of the 2 section rudder IIRC) that reduced RCS propellant usage substantially. [EDIT Point is this is not a new phenomena and has been dealt with before. Skylon's maximum nose up would also be about 20deg below Shuttles peak (50deg Vs 70deg). I'm quite sure that REL have flown Skylon through many simulated trajectories to check what happens in these cases ]

BTW it's SOP to have triply redundant actuators for large aircraft. You're postulating simultaneous failure of all drive loops and a possible cooling failure as well.

Probaballistic risk assessment would suggest that failure mode is very remote, but I don't have stats for the simultaneous failure of all flying controls on large aircraft to give a number.  I can say the goal for blind landing systems was 1 failure in every billion operating hours across all aircraft it was installed in and AFAIK it was achieved.

Using the dorsal surface as the heatshield has merits, but necessitates the "barrel roll of death", as opposed to the "swoop of death" required for nose first reentry VTVL SSTO's.
Or you could stick with Skylon's planned flight path and avoid either.   :)
Quote
I think an unbroken TPS is preferable, and makes certain other things (beamed thermal propulsion receiver) easier to integrate into the airframe.
The trouble is it relies on the whole surface remaining perfect for all missions.

That's simply unreasonable for a vehicle of this size and expected life time.   :( [EDIT NASA are doing it for Orion, SpaceX are not doing it for Dragon, and Dragon is planned to be reused ]
Quote
The kicker is payloads and airframe have to handle long durations in both flipped and unflipped flight modes, which makes systems design more complicated.
Very much more complicated.
Quote
I suppose doing the flip always clockwise, and the unflip counterclockwise, might make it a bit easier, especially with a passenger module and the rotating seat frames.
Doubtful. You're back with the making-the-structure-strong-in-2-axes-at-once issue.  :(

When people think of cranes around rockets I believe they are thinking of Saturn/Apollo (or SRB's) being assembled in a building so big it has its own weather.

But a Skylon hangar is more like a 3-4 storey building with 20 tonne gantry crane. This is far below the leading edge of crane technology. I'd expect 10s of suppliers globally could deliver such a system.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/07/2015 05:32 PM
My point (worry) could be summarized like this:

Skeptical assessments of Skylon tend to focus on it having 'holy grail' SSTO performance, and using unproven SABRE engines. But its return from orbit is also novel/unproven in terms of its shape and size. This part of the design challenge is rarely highlighted.

But just as with the SABRE engines, Skylon re-entry does not require any magical new technology (and it evidently didn't phase the ESA assessors) but it is a novel shape, and its development will involve more than just selecting high temperature materials and nailing them together.

My bet is the development plan will include high-fidelity testing of those canards as they move around in high-temperature >hypersonic air, and fully understanding the way the resultant shock patterns interact with the fuselage. Heating at the hinge seems like a good place to focus on.

The tip of the engine inlet cones are likely another hot-spot too, but modeling/testing that seems trivial compared to the canards.

Speculation: collaboration with US Air Force could provide an opportunity for the sort of testing I'm talking about here.

Edited for clarity.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/07/2015 06:16 PM
Re take-off optimization (responding to full quote below):

I find these discussions great fun, but it's worth remembering that any 'winning' argument is probably wrong/incomplete as we're never privy to all the relevant factors.

That said, let me explain more about my thinking.

First of all, I should have emphasized I was talking about improving take-off for the self-ferry case; with little/no LOX and less LH2 on board the loads will be much less than with an orbital launch from its custom runway.

It seems to me highly desirable for Skylon to be able to self-ferry from regular runways, e.g. the Airbus runway in Toulouse (3.5km) to its own 5.5km orbital launch facility. I'm thinking about shortening take-off length in hopes that self-ferry could be made realistic.

In additional to delivering new vehicles, this would mean simplified recovery if it has to land at an alternate site. It would also mean a spare could be flown in - perhaps leased from another provider - if one had maintenance issues.

In terms of take-off aerodynamics, I'm pretty confident my idea (duplicate the canards to get double the lift/control authority) has merit theoretically. First of all, we can be sure that the wing is not optimized for short take off - many factors constrain it in other directions. Even commercial aircraft airfoils are not optimized for take-off, hence the need for high-lift devices such as flaps. The canards would essentially be the equivalent of flaps.

Imagine an extreme case: A Skylon with no canards, and wings much smaller than the current design: they generate so little lift that its still resting on its undercarriage when barreling down its 50km runway at 700mph. But at 700mph there is enough air flowing by to lift the vehicle IF the wings had some angle of attach with respect to the airflow. That's what the canards could do for this case, and that's why I suggested doubling up the canards could shorten the take-off length during self-ferry with the current design.

EDIT: my assumption is that the current canards are not already large enough to provide all the lift you'd require to pick the nose up for the shortest self-ferry take-off, and that duplicating them gives worthwhile redundancy.

And in terms of them causing drag which would hinder short take-off: they'd be feathered (so minimal drag) until they were used to rotate. In that respect, they are better than flaps on commercial aircraft.

the additional surfaces would allow the nose to be pulled up earlier, putting more air under the wings leading to an earlier take-off. Similarly, all four surfaces could serve as air-brakes after landing, reducing roll-out distance.

And while we’re talking about self-ferry, if the engines could be gimbaled above the horizon, that too would help pick up the nose as the engines are behind the landing gear. I suppose it would also mean less rocket blast hits the runway which is a good thing.

Early rotation: Once you're out of ground effect, I think the design would already be at optimal angle-of-attack for the take-off airspeed regime.

High gimbal: That would represent a new stress dynamic for transmitting thrust to the airframe: Now a shear on the engine itself and a torque on the wings. So a bigger mass penalty in the structure? And air is a capricious thing: I think you'd still want thrust running through the center-of-mass or who knows what-all instabilities you'd run into in the turbulent lower atmosphere (where, granted, aero surfaces are good at helping (although less so at low airspeeds)).

The effect of either approach is to trade higher drag for increased lift. I'm not sure that lift is the right variable to optimize for: I would have thought that optimizing for early acceleration (i.e _lower_ drag) would actually be what you want. (The way I though of it, probably simplistically, is that if you had high lift but traded a lot of fuel to get it, all you'd end up with would be a slightly less-fueled ship a few meters higher off the ground, going at the same speed. All your fuel's energy went into adding turbulence to the atmosphere.)

But I realize that it's a very complicated optimization problem: Less time on the runway may well translate to mass savings in the undercarriage, less brake-cooling water to carry, etc. And if you really can get into ground-effect flight earlier, it might be a very efficient regime in which to accelerate.


A few threads back I floated the notion of dorsal re-entry. Imagine a configuration like SR-71 with two vertical stabilizers, one at each wingtip and no canard. It rolls down the runway "upside-down" with the stabilizers doubling as undercarriage. The payload doors are underneath at this time, and the top is unbroken TPS out of FOD danger from objects on the runway. During re-entry, the ship lies on its back, stabilizers sticking up out of the heating. It then flips over, probably subsonic, and lands like it takes off.
The relevance to the current discussion is that you now have two configurations (albeit, obviously, tightly linked!) that can be optimized: the take-off can favor low-speed aerodynamics, and the re-entry can favor dynamic stability.
While this approach might help for roll stability, I'll admit it doesn't much address the point that you raised which I think was focused on pitch. It does seem like some kind of aero-surface, ideally far from the center of lift, would help for that flight regime you mentioned.

 

All these thoughts make me realize, yet again, what a difficult optimization problem Skylon represents. I wonder if REL ever had a bash at "genetic" programming: iterating randomly tweaked designs, simulate over the whole mission, repeat.

But I talk too much.
</uninformed guesses>
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/08/2015 12:13 AM
First of all, I should have emphasized I was talking about improving take-off for the self-ferry case; with little/no LOX and less LH2 on board the loads will be much less than with an orbital launch from its custom runway.

It seems to me highly desirable for Skylon to be able to self-ferry from regular runways, e.g. the Airbus runway in Toulouse (3.5km) to its own 5.5km orbital launch facility. I'm thinking about shortening take-off length in hopes that self-ferry could be made realistic.
On self ferry Skylon will be 150 tonnes lighter. That alone will shorten the takeoff substantially. It will accelerate substantially faster and its wing loading be substantially lower. 
Quote
In additional to delivering new vehicles, this would mean simplified recovery if it has to land at an alternate site. It would also mean a spare could be flown in - perhaps leased from another provider - if one had maintenance issues.
REL state the landing speed and sink rate is such that it could land on grass. Note landing, not take off.
Quote
In terms of take-off aerodynamics, I'm pretty confident my idea (duplicate the canards to get double the lift/control authority) has merit theoretically. First of all, we can be sure that the wing is not optimized for short take off - many factors constrain it in other directions.
Nevertheless it will take off in short order in air breathing mode.
Quote
Even commercial aircraft airfoils are not optimized for take-off, hence the need for high-lift devices such as flaps. The canards would essentially be the equivalent of flaps.

Imagine an extreme case: A Skylon with no canards, and wings much smaller than the current design: they generate so little lift that its still resting on its undercarriage when barreling down its 50km runway at 700mph. But at 700mph there is enough air flowing by to lift the vehicle IF the wings had some angle of attach with respect to the airflow. That's what the canards could do for this case, and that's why I suggested doubling up the canards could shorten the take-off length during self-ferry with the current design.

EDIT: my assumption is that the current canards are not already large enough to provide all the lift you'd require to pick the nose up for the shortest self-ferry take-off, and that duplicating them gives worthwhile redundancy.
If they can deliver enough lift to get the nose up for a fully loaded takeoff (which they are sized for) how likely is it they can't when the vehicle is 150 tonnes lighter?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/08/2015 12:13 AM

Assessments of Skylon tend to focus on it having 'near impossible' SSTO performance,
For a VTOL SSTO, rather less so for an air breathing HTOL. This matter has been discussed before.
Quote
and using unproven SABRE engines. But its return from orbit is also novel/unproven in terms of its shape, size. And to land in one piece, those canards need to operate as expected.
Exactly like the control surfaces of any vehicle that use aerodynamic lift and exactly as the Shuttle design managed on  135 flights. Like the Shuttle it will probably have triply redundant actuator circuits.

It's the difference between "likely to fail" and "may fail in in 20 000 launches."
Quote
My bet is the development plan includes high-fidelity testing of those canards as they move around in high-temperature >hypersonic air, and fully understanding the way the resultant shock patterns interact with the fuselage. Cooling at the hinge seems like a good place to focus on.
At least part of that has already happened when DLR (who thought the canards too thin to survive the heating) did a major CFD exercise on it using their Tau CFD code and confirmed they will survive.

It's a pretty safe bet that such test work is part of the schedule for the Skylon project.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/08/2015 12:43 AM
I think you are under the impression that me naming the concerns of Skylon's skeptics, and asking questions means I've already decided Skylon is a flawed concept - and that you need to defend it. Not true.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/08/2015 06:31 AM
I think you are under the impression that me naming the concerns of Skylon's skeptics, and asking questions means I've already decided Skylon is a flawed concept - and that you need to defend it. Not true.
Not at all. I'm trying to understand what you're concerned about and you are not making your concerns any clearer.

You started with something about canards being too small then elevons being too close to the body and come up with a reason for having a more conventional tail. You talk about the canard actuators failing but seem to ignore they will likely be triply redundant and when this is mentioned you just seem to ignore it.

So what is the root cause of your worry?



Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/08/2015 03:38 PM
I'm not worried; at least not in the usual negative sense. I think I need to put more smileys in my posts because the 'worries' you see are born of an interest and enthusiasm with the engineering challenges Skylon represents. That's clearly not coming through.

If you reread my posts you'll see they go like this (with positive fanboi vibe now added in):

1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"

2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/09/2015 12:49 PM

If you reread my posts you'll see they go like this (with positive fanboi vibe now added in):

1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"
Perhaps because no spaceplane before it had cannards? The importance of trim was one of the big discoveries of the HOTOL project. Putting the engines on the wing tips is a big change. Skylon is designed to avoid the continuous "fluttering" of control surfaces the Shuttle used to keep it stable. You're assuming it will be unstable. That's not a given.

An interesting question is could it be stable enough to allow a human pilot to fly it without a computer in the loop to stabilize it.

That would make it a very exciting prospect for some potential customers.

Quote

2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."
Then you're missing the biggest issue of all. The huge noise level. It's not just the thrust it's the exhaust velocity for air/H2 is much higher than air/kerosene mixture. While OK for occasional takeoffs or emergency landings (which will be unpowered) it's most unlikley there will be fully fueled take offs from any regular airport.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/09/2015 03:21 PM

If you reread my posts you'll see they go like this (with positive fanboi vibe now added in):

1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"
Perhaps because no spaceplane before it had cannards? The importance of trim was one of the big discoveries of the HOTOL project. Putting the engines on the wing tips is a big change. Skylon is designed to avoid the continuous "fluttering" of control surfaces the Shuttle used to keep it stable. You're assuming it will be unstable. That's not a given.

Rather than repeat myself here, I'll refer interested parties (if there are any) back to my initial post on this subject: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1354087#msg1354087.

If you've read anything that indicates the Skylon shape will be more passively stable than the Shuttle during belly-first entry, I'd be very interested in that reference. As you know, the Shuttle was not stable, and its orientation needed to be active maintained with the body flap and elevons.

EDIT: Perhaps we can agree that placing the engines on the wings makes Skylon more symmetrical than the Shuttle in terms of entry (pre-aerodynamic, ~45 degree nose-up) configuration, which is an advantage. But where the orbiter was a simple, relatively compact double-delta, Skylon is a complex shape, and spindly, meaning ISTM that it will have more pronounced forces at the nose and tail that need to be dealt with.

Quote
An interesting question is could it be stable enough to allow a human pilot to fly it without a computer in the loop to stabilize it.

That would make it a very exciting prospect for some potential customers.

Quote

2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."
Then you're missing the biggest issue of all. The huge noise level. It's not just the thrust it's the exhaust velocity for air/H2 is much higher than air/kerosene mixture. While OK for occasional takeoffs or emergency landings (which will be unpowered) it's most unlikley there will be fully fueled take offs from any regular airport.

Right. The cases mentioned in my (non fanboi) post were 1] initial delivery to Korou, and 2] recovery after abort: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1355300#msg1355300. I 'worry' that self-ferry even in these rare, special cases might not be possible. And noise is certainly a factor.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/09/2015 05:01 PM
And here's the sort of response I was hoping for:

Response to my initial post:

Quote
"While adding redundant control surfaces (e.g. horizontal stabilizers on the tail) would indeed mean you'd still have those available if the front canards were to fail, wouldn't the failed/stuck surfaces cause you control problems that your remaining surfaces might not be able to overcome?"

Me:

"You're probably right. Better to put extra effort into making sure the canards always work. (And are sized for self-ferry in addition to orbital take-off)."
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/10/2015 07:43 AM
Rather than repeat myself here, I'll refer interested parties (if there are any) back to my initial post on this
If you've read anything that indicates the Skylon shape will be more passively stable than the Shuttle during belly-first entry, I'd be very interested in that reference. As you know, the Shuttle was not stable, and its orientation needed to be active maintained with the body flap and elevons.
I cannot cite a reference. Considering the Shuttles design you had a series of big "point masses" (3 SSMEs, their plumbing and the OMS modules, along with the APUs, their fuel and cooling) in the tail. That puts a big  weight in the tail and you're trying to the Shuttle at 70 degs without flipping it over.

Skylons, engines, and returning payload (if any) are with the wings in the middle. This means that rather than fighting a big (point) tail mass (  you have a relatively light fuselage in 2 parts which are (roughly) the same mass. That means surfaces can be smaller and response times less critical.

BTW the slab sides on the orbiter made for a very bad glider which was very prone to cross winds.
Quote
EDIT: Perhaps we can agree that placing the engines on the wings makes Skylon more symmetrical than the Shuttle in terms of entry (pre-aerodynamic, ~45 degree nose-up) configuration, which is an advantage. But where the orbiter was a simple, relatively compact double-delta, Skylon is a complex shape, and spindly, meaning ISTM that it will have more pronounced forces at the nose and tail that need to be dealt with.
It's not aesthetics, it's putting the biggest masses on or near the longways  centre of mass so they have near zero moment  :( That's important because the centre of pressure is constantly shifting during reentry as you go from M23 to M0.

There was nothing simple about Shuttles shape. Shuttle histories state it took 40-50 000 hrs of wind tunnel time to develop. Part of that was for the cross range requirements of the USAF and I would suspect partly trying to adapt the blunt body aerodynamics developed for war head reentry capsules into a useable form for a winged vehicle, which basically junked the usual rule of thumb for high speed aircraft that thinner wings are always better.
Quote
Right. The cases mentioned in my (non fanboi) post were 1] initial delivery to Korou, and 2] recovery after abort: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1355300#msg1355300. I 'worry' that self-ferry even in these rare, special cases might not be possible. And noise is certainly a factor.
In 1 the vehicle will be less than 50% of its GTOW to orbit. There is every reason to think it's takeoff run will be much shorter. Keep in mind 1.5Km of that 5.5Km is solely for emergency stopping of a fully loaded Skylon. I don't know if you could drop the takeoff run and emergency braking distance to 3.5Km but I think it would be close.

2)is more a case of planning for an emergency and the legal issues around them. Clearing airspace for a Skylon on abort then getting it down. Which runway it comes down on would depend on how much is pre programmed into its auto pilot and to what extent it can receive external commands. Getting it back to Kourou would then involve a damage assessment, possible repairs up to engine replacement and refueling with LH2. While different in detail from a conventional aircraft the process would be pretty much the same.

"You're probably right. Better to put extra effort into making sure the canards always work. (And are sized for self-ferry in addition to orbital take-off)."
I guess that's a nice illustration of why it's difficult to do "tone" on the internet.  :(

Can you explain why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 04/10/2015 11:31 AM
Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon.

http://forum.nasaspaceflight.com/index.php?topic=24621.msg987883#msg987883


Also as a reminder there are two lectures coming up this month for those able to attend, on Tuesday 14th with Richard Varvill:

http://aerosociety.com/Events/Event-List/1934/Skylon-and-Sabre-Bringing-Space-Down-to-Earth

and on Wednesday 22nd with Alan Bond:

http://aerosociety.com/Events/Event-List/1686/The-Sabre-Engine

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/10/2015 07:36 PM
I'm confident everybody in this conversation is within 10% agreement, so to go on would say more about the hazards of forum-based communication than anything else.

For example, lkm says "Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon". Which should settle the issue, right? But in the cited comment Hempsell actually says the following - in 2012 - "we currently believe believe Skylon would be able to use sub-3 km runways".

I take that to mean it's not a 100% done deal, and so a topic for conversation. But when I raise the topic of self-ferry, and speculate on the usefulness of greater control authority if it turns out to be marginal on shorter runways JohnSmith19 asks me: "why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical."

Just because I'm interested in the self-ferry case doesn't mean I think it can't be done (and REL are liars). But by the same token, REL said they currently believe it can be done, which means there's a chance it might be tricky. That's what makes me raising the issue legit, rather than 'illogical'.

Same thing with Skylon entry. Just because I note that it's rarely talked about - and will not be a walk in the park - doesn't mean that I think it's impossible. But neither do I think it's established that no further work is necessary.

___

To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 04/10/2015 09:11 PM
I'm confident everybody in this conversation is within 10% agreement, so to go on would say more about the hazards of forum-based communication than anything else.

For example, lkm says "Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon". Which should settle the issue, right? But in the cited comment Hempsell actually says the following - in 2012 - "we currently believe believe Skylon would be able to use sub-3 km runways".

I take that to mean it's not a 100% done deal, and so a topic for conversation. But when I raise the topic of self-ferry, and speculate on the usefulness of greater control authority if it turns out to be marginal on shorter runways JohnSmith19 asks me: "why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical."

Just because I'm interested in the self-ferry case doesn't mean I think it can't be done (and REL are liars). But by the same token, REL said they currently believe it can be done, which means there's a chance it might be tricky. That's what makes me raising the issue legit, rather than 'illogical'.

Same thing with Skylon entry. Just because I note that it's rarely talked about - and will not be a walk in the park - doesn't mean that I think it's impossible. But neither do I think it's established that no further work is necessary.

___

To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.

My intention was only to point out that Hempsell had talked about it previously in the thread as it was some time ago and five threads back and I thought it might add to the debate, not end it. My thought on shortening take off requirements was whether optionally payload could be traded for increased take off thrust by augmenting with LOX.

On reentry, obviously nothing about that is easy but Skylon has always struck me as a somewhat prettier version of Faget's DC-3 and as such presumably has a similar reentry profile.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/14/2015 08:34 PM
To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
Certainly.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Mutley on 04/15/2015 07:50 AM
Lots more jobs appearing on the Reaction Engines website

http://www.reactionengines.co.uk/careers.html (http://www.reactionengines.co.uk/careers.html)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 04/15/2015 08:01 AM
nice! are these new jobs or sobstitutions of people that left?

anyway, SpaceX is so close now. The others cannot afford to to ignore reusability any more. Although I am seriously afraid someone at ESA will fall into the Siren's trap of a "REUSABLE ARIANE 6 BY 202X"........

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/15/2015 08:31 AM
Lots more jobs appearing on the Reaction Engines website

http://www.reactionengines.co.uk/careers.html (http://www.reactionengines.co.uk/careers.html)
Yes that's quite a broad range. Note some of them only make sense in the context of a company expecting to grow quite a lot and to a quite substantial size.

nice! are these new jobs or sobstitutions of people that left?

anyway, SpaceX is so close now. The others cannot afford to to ignore reusability any more. Although I am seriously afraid someone at ESA will fall into the Siren's trap of a "REUSABLE ARIANE 6 BY 202X"........
A lot of those roles look new.

"REUSABLE ARIANE 6 BY 202X"........

Hmm.  :( The fact ULA are committing to something may be more relevant. Before SX could be dismissed as just a private company who could do whatever they liked based on the whim of their CEO.

I think REL are still very weary of being a "government" programme (especially if that's an EU) so they have to steer a very tricky course.

SABRE/Skylon remains very high risk relative to the sort of systems Ariane 6 is being described as, although quite what that final shape will be seems to be changing. Are "all solids" still the baseline?

What might be possible would for ESA to say they need a European backup plan funded at some level in case commercial customers remain implacably opposed to an all solid design.

Solids BTW generate much more vibration on the payload and large ones are difficult (impossible?) to shut down.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 04/15/2015 08:53 AM
I still wonder whether the UK government, or REL themselves, sent an application for funding at the Commission for the new Juncker fund. This is not public ownership in the classical way... If they didn't, I would at least like to undestand why :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/15/2015 12:35 PM
I still wonder whether the UK government, or REL themselves, sent an application for funding at the Commission for the new Juncker fund. This is not public ownership in the classical way... If they didn't, I would at least like to undestand why :)
Interesting question but from my (very) cursory look at the plan it's target is to stimulate the growth of businesses in Southern Europe, such as Spain and Greece, Italy perhaps.

One of its goals does seem to be increasing investment in higher risk transport infrastructure projects, and Skylon could definitely be described as one of those.  :)

Sadly it seems Britain may be a bit far North for this option to be viable.   :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 04/15/2015 01:45 PM
well, why it is correct that the goal is stimulating investment, the fund will not have a geographic orientation. true, it constitutes an incredible opportunity for southern Europe, but it has been repeatedly stated that projects will be selected solely on the basis of their benefits- even in EU countries which do not financially participate in the fund (even tough financially contributing to the fund allows countries to have a board member and so influencing decisions, which is not bad if you want to get some of the money you put in back into your country). Then again, the fund is done for industrial development..so maybe REL can apply in a few years or so!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Mutley on 04/15/2015 03:02 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/15/2015 03:10 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

Hopefully an announcement that may lead to more significant developments. Probably not in the direction of Skylon as I can't see the USAF being that interested in that as a concept, but perhaps in other areas of in atmosphere vehicle development.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 04/15/2015 03:45 PM
"Reaction Engines Ltd. and AFRL are now formulating plans for continued collaboration on the SABRE engine; the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system, testing of SABRE engine components and exploration of defence applications for Reaction Engines’ heat exchanger technologies."


very big deals coming. The first listed is (I believe) wha the AFRL is truly interested in- SKYLON might not be suitable for defense purposes, but other "vehicle concepts based on a SABRE derived propulsion system" might surely be.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Jim on 04/15/2015 03:49 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasibility of the SABRE concept

No, feasibility is the wrong word.  AFRL "investigations examined the thermodynamic cycle of the SABRE concept and found no significant barrier to its theoretical viability provided the engine component and integration challenges are met."

They found that it can happen but have not ruled on that it will happen.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/15/2015 03:53 PM

http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasibility of the SABRE concept

No, feasibility is the wrong word.  AFRL "investigations examined the thermodynamic cycle of the SABRE concept and found no significant barrier to its theoretical viability provided the engine component and integration challenges are met."

They found that it can happen but have not ruled on that it will happen.

But if anyone has the funds to make it happen it's the USAF, they are the kind of customer REL need.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Oli on 04/15/2015 03:53 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.

An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).

Any other ideas?


Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/15/2015 04:07 PM

http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.

An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).

Any other ideas?

Couldn't they have a smaller parasite hypersonic vehicle for access to orbit carried on the back of a larger slower carrier craft.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Oli on 04/15/2015 04:21 PM
Couldn't they have a smaller parasite hypersonic vehicle for access to orbit carried on the back of a larger slower carrier craft.

That would mean you have to design 3 vehicles: The carrier aircraft, the parasite and the carrier + parasite combined.

IMO the long term goal should remain SSTO, but with an intermediate step (and expendable upper stage).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Lars-J on 04/15/2015 06:05 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

Many of us has argued that from the start. But some staunch Skylon supporters (like John Smith 19) think it has to be SSTO or nothing. The logic of that escapes me, but then again they also seem to find smaller versions of Skylon (to test technology) to be a waste of time. Skylon needs to be a massive SSTO, apparently.   

Boeing didn't start out by building 747's. The 747 wasn't even their first jet aircraft.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/15/2015 06:41 PM
TSTO vs. SSTO Skylon is a complex issue. Factors I've come to consider important are:

1] The recent discussions highlighting the difficulty of upper stage re-use. It's a reasonable guess that TSTO Skylon would be cheaper to develop and less likely to fail, but will be more costly to run (i.e. you throw away the US each time). Pick your poison.

2] Size might not matter as much as you'd think. A few pages back I became convinced that a smaller Skylon might not be easier/cheaper to build.

3] If SpaceX manages to perfect stage one recovery, then a TSTO Skylon - that just achieves the same result and no more - is not going to happen.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/15/2015 06:47 PM
I'm not sure why there is so much focus as regards this announcement on orbital vehicles as it's far more likely this will see use at least initially in some kind of hypersonic aircraft. That's where the USAF's future focus is not exotic space vehicles.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/15/2015 07:05 PM
Agreed that USAF is probably not looking to SABRE for just orbital launch, but in the press release, Barry Hellman (USAF Program Manager) weighs in on the SSTO/TSTO topic by saying:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

That's what people are responding to.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 04/15/2015 07:11 PM
Agreed that USAF is probably not looking to SABRE for just orbital launch, but in the press release, Barry Hellman (USAF Program Manager) weighs in on the SSTO/TSTO topic by saying:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

That's what people are responding to.

Since we think that SABRE might not scale down all that well, what are the options for vehicles with only one SABRE engine, full size?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/15/2015 07:18 PM
It's an interesting question that was raised a few pages back. See this post and the replies: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1335441#msg1335441
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 04/15/2015 07:31 PM
http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

Many of us has argued that from the start. But some staunch Skylon supporters (like John Smith 19) think it has to be SSTO or nothing. The logic of that escapes me, but then again they also seem to find smaller versions of Skylon (to test technology) to be a waste of time. Skylon needs to be a massive SSTO, apparently.   

Boeing didn't start out by building 747's. The 747 wasn't even their first jet aircraft.

The 747 analogy is a false, Boeing after all DID build and fly an "SSTO" right from the start without even doing subscale testing or anything :)
(http://en.wikipedia.org/wiki/Boeing, Boeing Model 1 :) )
The reason for REL insisting that Skylon be  an SSTO is not for technical testing purposes. They expect to accomplish that with subscale and other testing, but as explained over and over again to you and others the economics don't work as well for a TSTO as for an SSTO. Will the Skylon BE built as an SSTO? If REL has anything to say about it then they will very much argue the economics aspect from their point-of-view, but in reality those funding the development will probably be in the form of a consortium and therefore REL will be only one voice.

And another factor is how "small" CAN you make a SABRE powered vehicle and get proper testing results? You CAN after all make a "SABRE" cycle LIKE engine with any cry-fluid but the deep cooling of the air pretty much takes LH2 to accomplish so using something else how accurate is the result? A small LH2 powered demonstrator would be all sort of helpful I'm sure but how much will it help "convince" investors and contributors? Frankly I'd be surprised if anyone who "doubts" a full up Skylon NOW would be convinced with anything short of... Well, a full up Skylon flying to orbit and back :)

The technical risk for development is high, but given the margin available not as high as say for a pure rocket powered SSTO. And the rewards are higher yet if it succeeds.

Given the huge projected development cost of the SSTO version, I kind of agree with that.

They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.

An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).

Any other ideas?

Lots and lots as hypersonic carriers launching expendable and reusable upper stages has been discussed and studied for decades. REL says their work shows it's not as cost effective as going straight to SSTO, and frankly the many air-breathing/rocket TSTO proposals tend to show that the air-breathing carrier aircraft is the most expensive part of the system no matter WHAT the propulsion cycle, and as we're all aware with Skylon the air-breathing portion of the flight while the most significant overall with ISP and delta-v is actually very little of the whole flight trajectory.

Really, I think if REL was to announce tomorrow that the SABRE included a SCramjet cycle the AF (and a lot of other folks) would suddenly find the whole idea of SSTO a LOT less "risky" or what reason I can't imagine :)

To seriously address a TSTO vehicle with SABRE engines what it amounts to is pretty much exactly the same flight profile as proposed for the Skylon; Take off and acceleration under air-breathing SABRE power to Mach-5+ then switching to pure rocket SABRE to Mach-10 to Mach-15+ outside the effective atmosphere with the release of the upper stage from that point. (For you imagination, take the twin-vertical version of the Skylon and recess a second stage just behind the point where the fuselage is maximum diameter and that's what it would look like)

And then ask yourself if, using the structural mass and propellant mass from the "second stage" you couldn't get the "carrier" aircraft up to around Mach-20 and orbit with about the same payload margin that's projected for the SSTO version of Skylon... And all your getting for the cost of two vehicle development programs, (please don't anyone think for a moment you can use an "off-the-shelf" rocket for a second stage) is a small increase in payload to orbit.

As an operational note, the Hopper as far as I understand it is CARRIED back to the launch site not towed and any operational SABRE powered vehicle will be fully capable of self-ferry by its nature. Unlike a rocket powered vehicle :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Oli on 04/15/2015 08:05 PM
To seriously address a TSTO vehicle with SABRE engines what it amounts to is pretty much exactly the same flight profile as proposed for the Skylon; Take off and acceleration under air-breathing SABRE power to Mach-5+ then switching to pure rocket SABRE to Mach-10 to Mach-15+ outside the effective atmosphere with the release of the upper stage from that point. (For you imagination, take the twin-vertical version of the Skylon and recess a second stage just behind the point where the fuselage is maximum diameter and that's what it would look like)

And then ask yourself if, using the structural mass and propellant mass from the "second stage" you couldn't get the "carrier" aircraft up to around Mach-20 and orbit with about the same payload margin that's projected for the SSTO version of Skylon... And all your getting for the cost of two vehicle development programs, (please don't anyone think for a moment you can use an "off-the-shelf" rocket for a second stage) is a small increase in payload to orbit.

As an operational note, the Hopper as far as I understand it is CARRIED back to the launch site not towed and any operational SABRE powered vehicle will be fully capable of self-ferry by its nature. Unlike a rocket powered vehicle :)

- That's pretty much what I was proposing, except maybe earlier switching to rocket mode if atmospheric heating is an issue at high Mach but I don't know that (max q is at around Mach 3+, so that's not a reason).

- If the upper stage has a propellant mass fraction of 0.9 staging at Mach 15 gives me ~2.5x the payload (Skylon C1). In any case, this isn't only about more payload or making the vehicle smaller, it's about having more margins to work with. I know some people here say it's basically all "standard tech", but as layman who is only capable of "comparing stuff" I'm very sceptical about that.

- Well Skylon is a good glider so I would go easy on those engines and tow the vehicle. You know, when people say 200 reuses it makes me suspicious.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/15/2015 08:32 PM

Agreed that USAF is probably not looking to SABRE for just orbital launch, but in the press release, Barry Hellman (USAF Program Manager) weighs in on the SSTO/TSTO topic by saying:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

That's what people are responding to.

Since we think that SABRE might not scale down all that well, what are the options for vehicles with only one SABRE engine, full size?

A question best asked maybe of Lockheed Martin as they are the ones trying to sell the idea of a hypersonic aircraft to the USAF.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/15/2015 08:36 PM
Many of us has argued that from the start.
And you didn't email REL to share your profound wisdom with them?
Quote
But some staunch Skylon supporters (like John Smith 19) think it has to be SSTO or nothing.
I "support" anything that lowers the $/lb price of a reasonable size payload to LEO.

REL are the only company that look to have a complete plan to get there.
Quote
The logic of that escapes me, but then again they also seem to find smaller versions of Skylon (to test technology) to be a waste of time. Skylon needs to be a massive SSTO, apparently.   
That's REL's position. Personally I'd like to see a smaller vehicle fly the whole mission but that means you've just spent a metric shedload of cash to do the same thing with virtually no payload and I know enough about the properties of LH2 to know what a major PITA making those pumps (at the same chamber pressure, which they'd have to be to keep the size down) would be see why they'd want to avoid that. 

When you make statements perhaps you could try for a little more accuracy?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/15/2015 08:44 PM
As far as I can tell it's only possible to judge the viability of Skylon as SSTO once you have confidence in the following:

1] The viability of the SABRE cycle - even in theory.
2] The real-life performance of a working SABRE.
3] The design and mass of the Skylon airframe around the SABRE .

It sounds like the USAF did not look at the airframe, so we could be hearing just the same informed guess you'd expect from anyone in the industry, i.e. SSTO margins are small, so it's risky.

Between the ESA and AFRL evaluations we can say 1] has been achieved. Next we need similar confidence in 2 and 3.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: topsphere on 04/15/2015 09:25 PM
Richard Varvill's talk has now been uploaded at:

https://player.vimeo.com/video/124910371

Everyone should watch it, it's quite a good viewing.

Although I have to say that watching it online where I can pause and have a think about what is being said makes for a much more informative lecture than live at the venue, where I felt like I couldn't possibly remember everything he was saying!!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 04/15/2015 09:55 PM
- If the upper stage has a propellant mass fraction of 0.9 staging at Mach 15 gives me ~2.5x the payload (Skylon C1).

No structural penalty on the first stage for shoehorning a big second stage into the existing design?

Also keep in mind that Skylon's payload is already large enough to capture the bulk of the market, and you can't scale the vehicle down because the combination of payload diameter requirements and aerodynamic considerations pretty much dictate its current size (believe it or not it has nothing to do with using LH2).  Is dual-manifest worth a potential increase in the development costs (your number assumes Skylon stats as advertised for the first stage, so it isn't easier to develop) as well as manufacturing, shipping, mating, and ground support for a brand-new fairly large upper stage on every flight, not to mention the downrange landing and the lack of on-orbit retrieval and downmass capability?

This is assuming REL are in the ballpark regarding airframe mass and engine performance, of course.  A substantial mass increase could change the picture, as could a significant rocket-mode underperformance (though as I've said I don't expect the latter).  As Skylon C shows, there's a huge margin for error in SABRE 4's airbreathing performance before the vehicle concept becomes nonviable, but technically that could still happen too...

Richard Varvill's talk has now been uploaded at:

https://player.vimeo.com/video/124910371

Thanks!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Oli on 04/15/2015 10:10 PM
No structural penalty on the first stage for shoehorning a big second stage into the existing design?

Also keep in mind that Skylon's payload is already large enough to capture the bulk of the market, and you can't scale the vehicle down because the combination of payload diameter requirements and aerodynamic considerations pretty much dictate its current size (believe it or not it has nothing to do with using LH2).

- Well the "first stage" doesn't reenter from orbit anymore and has less tank volume, could go both ways IMO.

- Yeah I know the shape is a PITA. You'd also have to rearrange the "internals" somehow to fit a stage in there. Maybe it would make sense to put the upper stage outside the vehicle. Adds a lot of drag of course. Other hypersonic designs have done that too though.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 04/15/2015 10:16 PM
Well the "first stage" doesn't reenter from orbit anymore and has less tank volume, could go both ways IMO.

Maybe, but REL says the Mach 5+ atmospheric flight is driving the TPS design just as much as the orbital reentry.  And as I said the tank volume isn't driving the shape - well, it is, in the sense that they had to make the fuselage shorter at the cost of increased drag to avoid wasting structural mass on empty space...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Oli on 04/15/2015 10:27 PM
Maybe, but REL says the Mach 5+ atmospheric flight is driving the TPS design just as much as the orbital reentry.  And as I said the tank volume isn't driving the shape - well, it is, in the sense that they had to make the fuselage shorter at the cost of increased drag to avoid wasting structural mass on empty space...

Define "driving just as much", doesn't mean they have the same requirements. At least the active cooling won't be required anymore. And why not go only to Mach 3 or so in the atmosphere? Well, that will lower the payload but might make other things easier. Regarding the tank, I thought the tank doesn't support the structure, so they could just make it smaller if there's less propellant without changing the shape.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aceshigh on 04/15/2015 10:55 PM
Richard Varvill's talk has now been uploaded at:

https://player.vimeo.com/video/124910371

Everyone should watch it, it's quite a good viewing.

Although I have to say that watching it online where I can pause and have a think about what is being said makes for a much more informative lecture than live at the venue, where I felt like I couldn't possibly remember everything he was saying!!

you know, the subject was most interesting and I enjoyed the talk content, but either Varvill's is not a good speaker or it was a bad time for him. I found it somewhat of a snoozefest and Varvill's sounded like he wanted to be somewhere else, or that he was pessimistic about the future.

I hope Varvill's is not in charge of selling Skylon...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 04/15/2015 11:14 PM
Define "driving just as much", doesn't mean they have the same requirements. At least the active cooling won't be required anymore. And why not go only to Mach 3 or so in the atmosphere? Well, that will lower the payload but might make other things easier.

My point is that there are a lot of factors involved that make it less than immediately obvious that TSTO is a better solution.  REL seems to think it's not, and they're the ones who have been doing real engineering with numbers.  There is no indication that a comparable amount of analysis underlies the AFRL statement.

Quote
Regarding the tank, I thought the tank doesn't support the structure, so they could just make it smaller if there's less propellant without changing the shape.

Yes, but then the structure and aeroshell are bigger than they need to be, which adds mass, and that trades against supersonic drag.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 04/15/2015 11:36 PM
Richard Varvill's talk has now been uploaded at:

https://player.vimeo.com/video/124910371

Everyone should watch it, it's quite a good viewing.

Although I have to say that watching it online where I can pause and have a think about what is being said makes for a much more informative lecture than live at the venue, where I felt like I couldn't possibly remember everything he was saying!!

you know, the subject was most interesting and I enjoyed the talk content, but either Varvill's is not a good speaker or it was a bad time for him. I found it somewhat of a snoozefest and Varvill's sounded like he wanted to be somewhere else, or that he was pessimistic about the future.

I hope Varvill's is not in charge of selling Skylon...

Speaking personally, if I'd been giving roughly same presentation for 10+ (20?) years, I too would have a hard time sounding enthusiastic! My hats off to them for keeping true to their vision over these long years. (I'm one of those kids who read about HOTOL with excitement in the '80s).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: dror on 04/16/2015 11:37 AM
You CAN after all make a "SABRE" cycle LIKE engine with any cry-fluid but the deep cooling of the air pretty much takes LH2 to accomplish so using something else how accurate is the result?

Randy

So I don't realy understand. Is the SABRE cycle even possible with other cryogenic fuel or not?
Strictly theoretically, is it possible with deep cooled methan for instance,  or is it not cold enogh to "liquify" the air?

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: dasmoth on 04/16/2015 01:55 PM
At LonCon last year, Alan Bond said LH2 was the only viable option.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 04/16/2015 03:05 PM
You CAN after all make a "SABRE" cycle LIKE engine with any cry-fluid but the deep cooling of the air pretty much takes LH2 to accomplish so using something else how accurate is the result?

So I don't realy understand. Is the SABRE cycle even possible with other cryogenic fuel or not?
Strictly theoretically, is it possible with deep cooled methane for instance,  or is it not cold enogh to "liquify" the air?

"SABRE-like" would mean a cycle that approximates but does not duplicate the SABRE. Off the top of my head I used an example of Mass Injection, Pre-Compressor Cooling or MIPCC which uses injected water and LOX to densify and concentrate the incoming air. You COULD use liquid methane and other cryo-fluids as injection fluids, (tests have been done with liquid nitrogen for verification of the MIPCC effects on turbo-machinery) but none of the really come to the point of DEEP cooling the air.

It actually DOES take liquid hydrogen to accomplish by the SABRE cycle. LH2 is what is know as a "hard" cryogen due to its VERY cold liquefaction temperature, (-252c/-423f) compared to other cryogenic fluids. For example methane FREEZES at -182c/-294f and its boiling point is higher as well at -161c/-258f. Your components of air (nitrogen/oxygen) liquefy at -196c/-320f and -182c/297f respectively. That's if we wanted to use something like a LACE (Liquid Air Cycle Engine) system though were we were actually making liquid oxygen for the engine, what we're talking about it simply "deep" cooling which require a lot less cooling. But we're also NOT talking about "normal" temperature air either. At Mach-5 the incoming air is going to be very hot BEFORE it's compressed and fed into the engine and only LH2 has the thermal capacity to reduce that temperature AND still drop the air temperature to a point where it can be dense enough to feed into the engine.

The main mechanical "sticking point" has always been the heat exchanger for deep cooling air for a turbo-machine application. Flow, Frost, and most other problem have been solved numerous times for various designs but mass was always an issue and REL has pretty much solved their problems with those factors with the current SABRE cycle. The OTHER more problematical issue has been that despite having worked out and proven in laboratory testing that deep cooling allowed all the advantages of LACE without most of the problems there was an industry and academic wide misunderstanding (blind spot really) that in order to run a ROCKET engine on "air" that propellant had to be made from a "gas" (which could be run in a turbo-compressor but not run through turbo-pump, the former being a jet engine the latter being "required" to inject propellant into an rocket engine) into a liquid.

I say this was a "blind spot" for the simple reason that even when it was PROVEN in lab testing that you in fact COULD deep cool air to a point where it could be run through a turbo-pump and fed into a rocket engine AS A GAS not only was this ignored by the majority of people working on the subject, the program that DID this mis-named the process by calling "turbo-LACE" which by definition would suggest that at some point the "air" becomes a "liquid" as its CALLED a version of the Liquid Air Cycle Engine...
(And in a classic case of the rocket engine people not talking to the jet engine people it was categorically stated in the literature of the time that you REQUIRED propellant to be liquid in order to run them through turbo-pumps to get high pressure in a rocket engine at the VERY same time the people producing what was to become the RL-10 LH2/LOX rocket engine were producing papers and studies showing how much MORE efficient it was to inject the propellants THROUGH A TURBO-PUMP as a GAS instead of a LIQUID! ::::doublefacepalm:::: Couple this with the obsession with the "perfect" air-breathing engine which {in theory} is the SCramjet and its pretty clear why its take REL going back and asking the "basic" questions again and NOT accepting the "common knowledge" to get to the point we are now)

You CAN do "SABRE-like" with other cryogen-propellants but the actual cycle(s) are very different and in most cases won't be as efficient at SABRE is supposed to be.

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SteveKelsey on 04/16/2015 05:38 PM
A lateral question at this point considering the detail of the discussion but with this

 "Furthermore, the heat exchanger technology also warrants further investigation for applications across the aerospace domain"

 indicating interest by the USAF,  will SABRE technology get snared in ITAR problems. I am delighted that SABRE has received the endorsement, but would hate to see Reaction Engine's IP inadvertently sequestered.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/16/2015 06:46 PM
indicating interest by the USAF,  will SABRE technology get snared in ITAR problems. I am delighted that SABRE has received the endorsement, but would hate to see Reaction Engine's IP inadvertently sequestered.
An excellent point.

The Official UK position on ITAR was described in the BSA's report on UK spaceports.

It makes depressing reading and you'd have to be very careful to ensure that any SABRE/Skylon IP is not "contaminated" by USAF work, effectively making the USG a business partner and giving it power of veto over your decisions.  :(

That might not be a position the British government is too bothered by but it should scare the hell out of any  British company that wants to be predominately  a supplier to the world in aerospace.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 04/16/2015 07:17 PM
indicating interest by the USAF,  will SABRE technology get snared in ITAR problems. I am delighted that SABRE has received the endorsement, but would hate to see Reaction Engine's IP inadvertently sequestered.
An excellent point.

The Official UK position on ITAR was described in the BSA's report on UK spaceports.

It makes depressing reading and you'd have to be very careful to ensure that any SABRE/Skylon IP is not "contaminated" by USAF work, effectively making the USG a business partner and giving it power of veto over your decisions.  :(

That might not be a position the British government is too bothered by but it should scare the hell out of any  British company that wants to be predominately  a supplier to the world in aerospace.  :(

The key phrase is "across the aerospace domain" rather than something directly applicable to "rocket/missile" technology. ITAR legally is about home made missiles not home made bombers and drones which is why model "rockets" get a hard time while GPS guided "autonomous and remote control" aircraft don't :)

As I asked earlier, one possible interesting application is a 'reverse' HE where heat is transferred FROM another source into an airstream, uses such as in turbo-heat-exchangers comes to mind as well.

It's not "just" for cooling anymore :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/16/2015 07:27 PM
Just to be clear what the CRADA says

The USAF accept that the SABRE 3 does work and at no point violates the laws of Thermodynamics provided the components can be be built to meet the thermal and structural requirements in different parts of the system.

NSF posters will already know that the core of the SABRE engines is the precooler and this has already been tested, due to it having the most demanding set of requirements in terms of airflow, temperature difference, frost control etc.

Some of the USAF's views are a bit odd. The SABRE cycle is specifically designed for flight to orbit. I think it would be superior for acceleration to M5 (during a launch) but if they wanted an engine for M5 they should have been aware of REL's LAPCAT work, which is a completely different cycle, optimized for M5 cruise.

I think it's very clear from their choice of the SABRE cycle and willingness to look at cryogens that this work is specifically aimed at launching payloads ASAP, the so called "responsive space" notion.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 04/16/2015 07:59 PM
May I at this point out that for the second time that 20 billion dollars (my random, but somewhat educated guess at current cost now) is not a lot of money in terms of US govt spending...

I am slightly concerned about IP having been already handed over in this CRADA process however...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/16/2015 08:35 PM

May I at this point out that for the second time that 20 billion dollars (my random, but somewhat educated guess at current cost now) is not a lot of money in terms of US govt spending...

I am slightly concerned about IP having been already handed over in this CRADA process however...

But it's not chicken feed either especially these days when even the USAF is feeling the pinch hence why they keep trying to retire various aircraft so they can fund things like the F-35.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: docmordrid on 04/17/2015 01:17 AM
It probably should be pointed out that the USAF is formulating proposals for a next generation bomber and a 6th generation fighter, with hypersonic.on the wish list for the latter.



Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/17/2015 06:21 AM
It probably should be pointed out that the USAF is formulating proposals for a next generation bomber and a 6th generation fighter, with hypersonic.on the wish list for the latter.

The bomber is well, well beyond formulating proposals being as they've effectively admitted to it being at the prototype stage so isn't relevant here.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 04/17/2015 02:59 PM
Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 04/17/2015 05:17 PM
Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.

Actually I've always thought that too. The CRADA might have specified SABRE, but it seems extremely unlikely that the investigations didn't involve all types of uses they were interested in.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/17/2015 06:41 PM

Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.

Totally agree that's what the USAF will be interested in not SABRE itself. There has been indications that the USAF would like to have some kind of hypersonic technological demonstrator in the air before the turn of the decade. How achievable that kind of target is for REL on the propulsion side whilst still trying to develop SABRE is anyone's guess.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/17/2015 06:45 PM
Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.
It's clear what the CRADA studied. It's equally clear that SABRE's focus is single stage to orbit launch and if the USAF chose to ignore that point that's their decision.

I will note that SABRE and Skylon are separate  designs. If the USAF were so minded they could look at a more conservative airframe that traded payload for more traditional aerospace materials.

How small I don't know. Part of it would depend on wheather they wanted orbit from a CONUS site, rather than an equatorial site. It would be an option.

Actually I've always thought that too. The CRADA might have specified SABRE, but it seems extremely unlikely that the investigations didn't involve all types of uses they were interested in.

It's not the use. LAPCAT's internals are completely different, with the turbine outside the core. IIRC it trades higher weight for better LH2 economy and of course eliminates all the air sealing system as it runs in atmosphere all the time.

May I at this point out that for the second time that 20 billion dollars (my random, but somewhat educated guess at current cost now) is not a lot of money in terms of US govt spending...

I am slightly concerned about IP having been already handed over in this CRADA process however...
The cargo transport contract to the ISS is about $18Bn

$20Bn is about a 66% rise on the last REL estimate I'm aware of ($12Bn.) That last rise was caused by including the Skylon Upper Stage to take payloads to GTO as part of the baseline development.

That's a lot of inflation compared to REL's estimate.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: dror on 04/17/2015 07:00 PM

$20Bn is about a 66% rise on the last REL estimate I'm aware of ($12Bn.) That last rise was caused by including the Skylon Upper Stage to take payloads to GTO as part of the baseline development.


Is that Skylon Upper Stage planned to be reusable and return to the Skylon befor reentry or expendable?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 04/17/2015 07:07 PM
Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.
It's clear what the CRADA studied. It's equally clear that SABRE's focus is single stage to orbit launch and if the USAF chose to ignore that point that's their decision.

I will note that SABRE and Skylon are separate  designs. If the USAF were so minded they could look at a more conservative airframe that traded payload for more traditional aerospace materials.

How small I don't know. Part of it would depend on wheather they wanted orbit from a CONUS site, rather than an equatorial site. It would be an option.

Actually I've always thought that too. The CRADA might have specified SABRE, but it seems extremely unlikely that the investigations didn't involve all types of uses they were interested in.

It's not the use. LAPCAT's internals are completely different, with the turbine outside the core. IIRC it trades higher weight for better LH2 economy and of course eliminates all the air sealing system as it runs in atmosphere all the time.

Ok. But I am sure the USAF can use their imagination :)

May I at this point out that for the second time that 20 billion dollars (my random, but somewhat educated guess at current cost now) is not a lot of money in terms of US govt spending...

I am slightly concerned about IP having been already handed over in this CRADA process however...
The cargo transport contract to the ISS is about $18Bn

$20Bn is about a 66% rise on the last REL estimate I'm aware of ($12Bn.) That last rise was caused by including the Skylon Upper Stage to take payloads to GTO as part of the baseline development.

That's a lot of inflation compared to REL's estimate.  :(

You're right. I believe you are referring to last, fairly recent, estimates which included a reduction in price owing to potential new manufacturing approaches (was it manufacturing?). So I completely take that back. I was going by the old, old, oft quoted GBP price,  rounding up quite a lot for years passed and then adding a hefty conversion to dollars. Very back of envelope and prob very inaccurate.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/17/2015 07:27 PM
Is that Skylon Upper Stage planned to be reusable and return to the Skylon befor reentry or expendable?
It's designed for 10 reuses running on LH2/LO2 through a pair of the SOMA engines. It uses the idea of the duration for an orbit to near GEO being a sub multiple of the period of the Skylon's  orbit (so called "resonant" orbits) so it "falls" back to the Skylon orbit and the Skylon is in place to pick it up than bring it back.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 04/17/2015 08:06 PM

Honestly, the press release makes my previous gut feel that much stronger - it's Scimitar the USAF really want.

Could REL develop the two engines in parallel? I'm going to say no. Regardless of the similarities, I would expect the detailed engineering on either one would consume their entire energies.
It's clear what the CRADA studied. It's equally clear that SABRE's focus is single stage to orbit launch and if the USAF chose to ignore that point that's their decision.

I will note that SABRE and Skylon are separate  designs. If the USAF were so minded they could look at a more conservative airframe that traded payload for more traditional aerospace materials.

How small I don't know. Part of it would depend on wheather they wanted orbit from a CONUS site, rather than an equatorial site. It would be an option.

Actually I've always thought that too. The CRADA might have specified SABRE, but it seems extremely unlikely that the investigations didn't involve all types of uses they were interested in.

It's not the use. LAPCAT's internals are completely different, with the turbine outside the core. IIRC it trades higher weight for better LH2 economy and of course eliminates all the air sealing system as it runs in atmosphere all the time.

May I at this point out that for the second time that 20 billion dollars (my random, but somewhat educated guess at current cost now) is not a lot of money in terms of US govt spending...

I am slightly concerned about IP having been already handed over in this CRADA process however...
The cargo transport contract to the ISS is about $18Bn

$20Bn is about a 66% rise on the last REL estimate I'm aware of ($12Bn.) That last rise was caused by including the Skylon Upper Stage to take payloads to GTO as part of the baseline development.

That's a lot of inflation compared to REL's estimate.  :(

If you think everything that was studied was detailed in that press release then I would say that you would be mistaken.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 04/17/2015 08:13 PM
It IS important to note that the AF looked at the SABRE and its cycle specifically. As noted the HE itself has other uses that make the technology important to study but the cycle itself DOES actually have some uses beyond orbital launch, though NOT in a Skylon type vehicle :)

For example it could be used in a Hypersoar (http://en.wikipedia.org/wiki/HyperSoar) which does skip-glides at speeds of less than Mach-12. (Studies show a "sweet-spot" around Mach-6 actually) Or a deep cooled engine using another cycle is possible (http://www.secretprojects.co.uk/forum/index.php?topic=6422.0, http://www.secretprojects.co.uk/forum/index.php?topic=6422.0, etc) are possible as well.

The main point of contention is operationally the AF would rather avoid LH2 propellant if at all possible, however the CRADA makes it pretty clear that the entire operation of the SABRE cycle DEPENDS on using LH2 and deep cooling, (which it does) and so any consideration of using the technology has to take that into account.

That little item in and of itself is the main point of the whole exercise IMO. This points out very distinctly that while you can have other cycles that can possibly do what the SABRE does, the SABRE itself REQUIRES LH2 so any plans to utilize the cycle require the use of LH2. The AF has in the past has used H2O2, hydrazine, IRFNA, and other toxic and dangerous propellants but they have ONLY considered (and used) LH2 when they had no other choice for the mission they wanted. (And gladly dropped it if ANY other option was available) The wording tells me that someone, somewhere was of the mind that they could use the SABRE cycle without the LH2, ("Liquid Methane is cold, we really don't need LH2") and this pretty much puts the last nail in that coffin as it were. You want to use the SABRE cycle you have to use LH2, you don't want to do that then this cycle isn't for you.

So IF the AF wants this for a launch vehicle expect to hear more, if they are looking for anything else it won't be using the SABRE or LH2 :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/18/2015 08:50 AM
...and this pretty much puts the last nail in that coffin as it were. You want to use the SABRE cycle you have to use LH2, you don't want to do that then this cycle isn't for you.

So IF the AF wants this for a launch vehicle expect to hear more, if they are looking for anything else it won't be using the SABRE or LH2 :)
With the Delta IV and Centaur the USAF have demonstrated they will tolerate LH2 for certain specific tasks, primarily launch.

Outside that area I don't think they can get their can let go their preconceptions to use it for anything else, and there's simply no way anything like SABRE can work with anything like a normal liquid hydrocarbon.   :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: mhlas7 on 04/18/2015 06:15 PM
Is that Skylon Upper Stage planned to be reusable and return to the Skylon befor reentry or expendable?
It's designed for 10 reuses running on LH2/LO2 through a pair of the SOMA engines. It uses the idea of the duration for an orbit to near GEO being a sub multiple of the period of the Skylon's  orbit (so called "resonant" orbits) so it "falls" back to the Skylon orbit and the Skylon is in place to pick it up than bring it back.
Are there any ballpark numbers for what the payload mass to GEO/GTO might be? I realize that the vehicle and engines are still very theoretical but are we talking about ~6T comsats, ~2T delta class payloads or <1T small sats?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 04/18/2015 07:48 PM
Is that Skylon Upper Stage planned to be reusable and return to the Skylon befor reentry or expendable?
It's designed for 10 reuses running on LH2/LO2 through a pair of the SOMA engines. It uses the idea of the duration for an orbit to near GEO being a sub multiple of the period of the Skylon's  orbit (so called "resonant" orbits) so it "falls" back to the Skylon orbit and the Skylon is in place to pick it up than bring it back.
Are there any ballpark numbers for what the payload mass to GEO/GTO might be? I realize that the vehicle and engines are still very theoretical but are we talking about ~6T comsats, ~2T delta class payloads or <1T small sats?

http://forum.nasaspaceflight.com/index.php?topic=33648.msg1207876#msg1207876

About 6.4 tonnes if the SUS is reused, 8 tonnes if it's expended.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Jim on 04/18/2015 07:51 PM

With the Delta IV and Centaur the USAF have demonstrated they will tolerate LH2 for certain specific tasks, primarily launch.


It is not a "toleration"    Space launch USAF is not the same as the USAF that would want to use the SABRE for other reasons. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/18/2015 08:52 PM
Are there any ballpark numbers for what the payload mass to GEO/GTO might be? I realize that the vehicle and engines are still very theoretical but are we talking about ~6T comsats, ~2T delta class payloads or <1T small sats?
In addition a SUS can put a satellite with an eletric thruster in a 5900 Km radius orbit above the Van Allan belt so it's not cooked as it reaches orbit. Assuming a 20Kw Hall thruster that would be the eqivalent of close to a 9 tonne sat  to GTO or over 5 1/2 tonnes at GEO.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/18/2015 09:02 PM
It is not a "toleration"    Space launch USAF is not the same as the USAF that would want to use the SABRE for other reasons.
True.

The "winged" side ofthe USAF seems much less happy about any cryogen that I'm surprised they'd look at SABRE, despite the fact it's looking like the only engine that's coming anywhere close to being built at full size  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 04/20/2015 06:50 AM
On other sites I've seen people asking why it cost so much to develop SABRE compared to rocket engines in other vehicles, specifically the SpaceX ones. I don't actually know if it is all that expensive comparatively but to myself I answer "reusability".

So I was wondering about this kind of thing :-) :
http://aviationweek.com/space/rocket-lab-unveils-battery-powered-turbomachinery

Presumably it doesn't scale or something like that. Nevertheless,  if there was some new risk that offered a possible way to cut the cost of either developing or building SABRE, would it be worth going for?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 04/20/2015 11:31 AM
On other sites I've seen people asking why it cost so much to develop SABRE compared to rocket engines in other vehicles, specifically the SpaceX ones. I don't actually know if it is all that expensive comparatively but to myself I answer "reusability".

So I was wondering about this kind of thing :-) :
http://aviationweek.com/space/rocket-lab-unveils-battery-powered-turbomachinery

Presumably it doesn't scale or something like that. Nevertheless,  if there was some new risk that offered a possible way to cut the cost of either developing or building SABRE, would it be worth going for?
It might seem like a reasonable comparison but it's not really a fair one.

In theory both engines are designed for reuse but there the similarity ends.

The gas generator cycle is the most common pumped engine cycle in any propellant combination. There is a lot of prior art on how to build them regarding materials compatibility, design choices and tools  etc.

In contrast there is limited experience of pumped LH2/LO2 engines anywhere with 4 designs in the US (and the only production design dating from the 1960's) with 2 in Europe and 1 (IIRC) in Russia.

SABRE is also roughly 3x bigger than Merline and due to be tested in one of the most populous countries of Europe, making H&S and availability of test stands very big issues.  :(

A fairer comparison would have been the SSME programme. A first of its kind engine using LH2.

I emphasize LH2 because it's much harder to deal with. Typically all LH2 pipework uses welded steel pipes one in side the other, with a vacuum between. "Vacuum Jacket Line" is not cheap and will need to fitted to the SABRE test stands. There are no good ways to simulate LH2's temperature or it's compressibility. AFAIK LH2 is the only common liquid that at "reasonable" pressures (100s, not 1000s of atmospheres) can be compresses by several percent of its normal volume, making pump design especially tricky.  :(

SABRE is a first of its kind design and the only one operating over the M0-M23-M0 speed range.

The SABRE development programme is roughly $300m, I'd guess that's peanuts relative to the inflation adjusted costs of the SSME.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Krevsin on 04/20/2015 12:18 PM
...and this pretty much puts the last nail in that coffin as it were. You want to use the SABRE cycle you have to use LH2, you don't want to do that then this cycle isn't for you.

So IF the AF wants this for a launch vehicle expect to hear more, if they are looking for anything else it won't be using the SABRE or LH2 :)
With the Delta IV and Centaur the USAF have demonstrated they will tolerate LH2 for certain specific tasks, primarily launch.

Outside that area I don't think they can get their can let go their preconceptions to use it for anything else, and there's simply no way anything like SABRE can work with anything like a normal liquid hydrocarbon.   :(
Could SABRE potentially work with methalox?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 04/20/2015 01:16 PM
Could SABRE potentially work with methalox?

Not cold enough. See: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1360152#msg1360152

With the Delta IV and Centaur the USAF have demonstrated they will tolerate LH2 for certain specific tasks, primarily launch.

Outside that area I don't think they can get their can let go their preconceptions to use it for anything else, and there's simply no way anything like SABRE can work with anything like a normal liquid hydrocarbon.   :(
It is not a "toleration"    Space launch USAF is not the same as the USAF that would want to use the SABRE for other reasons.
True.

The "winged" side of the USAF seems much less happy about any cryogen that I'm surprised they'd look at SABRE, despite the fact it's looking like the only engine that's coming anywhere close to being built at full size  :(

Actually we've built a few "full-size" engines for various cycles in the past. What we haven't done is fly them :)

Mostly it's an operational thing in that the majority of infrastructure is based on hydrocarbon fuel. If LH2 use and infrastructure were as large there might be less opposition. But given the reduction rather than expansion of LOX operations as the overall infrastructure has grown for civil use I'm pretty sure LH2 by the AF will remain a VERY limited segment of operations :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 04/20/2015 08:17 PM
The SABRE development programme is roughly $300m, I'd guess that's peanuts relative to the inflation adjusted costs of the SSME.

That's $£360M to get to first working prototype.  Which is about 1/10 of the whole engine development programme, which suggests that their cost estimate includes everything it's supposed to to get the engine into actual production...

EDIT:  Metric vs. Imperial money confusion...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 05/09/2015 07:00 PM
Regarding the placement of any future UK spaceport - now that the results of the UK election make the breakup of the UK much more likely (and possibly within 5-10 years), I'd wager that the powers that be will be reluctant to put any money into placing the spaceport in Scotland.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: A_M_Swallow on 05/10/2015 03:24 AM
Regarding the placement of any future UK spaceport - now that the results of the UK election make the breakup of the UK much more likely (and possibly within 5-10 years), I'd wager that the powers that be will be reluctant to put any money into placing the spaceport in Scotland.

Possibly, but the British Government is likely to go the other way - use the spaceport as a bribe. Since the Scottish Nationalists are an extreme left wing group (for instance they want Britain's nuclear weapons removing from Scotland) who already control most social spending in Scotland they cannot be bribed with military contracts.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 05/10/2015 05:28 AM

Quote from  AM Swallow on: Today at 03:24 AM - sorry I didn't quote this properly when I first wrote it
Quote
Possibly, but the British Government is likely to go the other way - use the spaceport as a bribe. Since the Scottish Nationalists are an extreme left wing group (for instance they want Britain's nuclear weapons removing from Scotland) who already control most social spending in Scotland they cannot be bribed with military contracts.

I don't think the SNP is bribable. Anything you give them, they will present to Scotland as their spoils of war, enhancing their position and increasing the likelihood of them leaving.   It is important for the government to ensure that credit for whatever happens will be attributed to the union.  Something like Skylon might be exceedingly good at that in the way that the aircraft carriers and the type 26 destroyers are.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: A_M_Swallow on 05/10/2015 05:53 AM
Quote
Possibly, but the British Government is likely to go the other way - use the spaceport as a bribe. Since the Scottish Nationalists are an extreme left wing group (for instance they want Britain's nuclear weapons removing from Scotland) who already control most social spending in Scotland they cannot be bribed with military contracts.

I don't think the SNP is bribable. Anything you give them, they will present to Scotland as their spoils of war, enhancing their position and increasing the likelihood of them leaving.   It is important for the government to ensure that credit for whatever happens will be attributed to the union.  Something like Skylon might be exceedingly good at that in the way that the aircraft carriers and the type 26 destroyers are.

The SNP needs to bring a spoil of war back to Scotland. If they come back with nothing then they will be seen as failures. The Conservative majority is sufficient that the SNP could be ignored/bypassed for the next 3-5 years.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/10/2015 08:18 AM
Regarding the placement of any future UK spaceport - now that the results of the UK election make the breakup of the UK much more likely (and possibly within 5-10 years), I'd wager that the powers that be will be reluctant to put any money into placing the spaceport in Scotland.
Incorrect.

You might like to look at the actual results

http://en.wikipedia.org/wiki/Scottish_independence_referendum,_2014

84% of the eligible electorate voted and the No (to independence) was about 10 percentage points greater than the yes result. For comparison IIRC a better than 50% turnout for the US Presidential election is viewed as good.

This was despite the Scottish Nationalist Party setting the schedule for the vote, the actual question itself and allow 16-18 year olds (statistically likely to vote for the newer idea) to vote.

The leader of the SNP at the time resigned as he had failed, despite every advantage to their campaign. When push came to shove Scots people voted with their heads, not their hearts.

This issue is dead for 1 to 2 generations in Scotland at least.

So IMHO putting a spaceport in Scotland is a pretty safe bet.

BTW on the nuclear issue it's estimated supporting those subs takes about 7000 well paying Scots jobs, and while SNP policy is NIMBY they are pragmatic enough to know that's quite a big black hole to fill.

SABRE/Skylon is designed from the ground up as a civilian space vehicle. Any effort to "weaponize" it would be so complex you'd just as well build your own ICBM.

I think the Scottish government would be happy to welcome REL to the country.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 05/10/2015 08:27 PM
JS19
**This issue is dead for 1 to 2 generations in Scotland at least**

I respect your opinion on matters space-related, but your analysis here is out of step with most political analysts on this point. England has moved to the right. Despite their single seat, UKIP had a lot of support in the election, as judged by their percentage share of the vote. There will be a referendum on the EU in 2 years. If England votes to leave, the UK will break up because the Scots want to stay in the EU.

Even aside from the referendum on the EU, Scottish and English sentiments have diverged in recent years, particularly since the Thatcher years. Cameron's comments subsequent to the Scottish referendum last year have left many Scottish who voted to stay in the union feeling that they were shafted. For unionists, the best likely outcome is now some sort of federal union, but I would not bet against it going further and a fully independent Scotland emerging in the near future.

It is that uncertainty that will make those in power (England) very reluctant to place such a strategically important infrastructure project as the spaceport in an area that they may not have control of in 10 years.

**I think the Scottish government would be happy to welcome REL to the country.**

I certainly agree with you here, but it won't be a decision left to the parliament in Scotland. This decision will be made in London.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/11/2015 12:07 PM
JS19
**This issue is dead for 1 to 2 generations in Scotland at least**

I respect your opinion on matters space-related,
That's very flattering. I'll try to continue to live up to your expectations.   :)
Quote
but your analysis here is out of step with most political analysts on this point. England has moved to the right. Despite their single seat, UKIP had a lot of support in the election, as judged by their percentage share of the vote. There will be a referendum on the EU in 2 years. If England votes to leave, the UK will break up because the Scots want to stay in the EU.
It's my view people who want to break some stuff up tend to want to break all stuff up. IOW If you liked the idea of the UK leaving Europe you like the idea of Scotland leaving the UK.

Except when the Scots were given the opportunity more than 84% turned out and it was roughly 11 to 8 against leaving.

http://en.wikipedia.org/wiki/Scottish_independence_referendum,_2014

Looking at UKIP
http://www.bbc.co.uk/news/election/2015/results

People were predicting a)A hung House of Commons and b) UKIP to win 2 seats, including their Leader becoming an MP.

But when push came to shove 1 candidate (not the leader) got elected.  So they delivered 50% of their expected performance.  The Liberal Democrats were destroyed but they still managed to retain 8 seats. Even the political wing of a disbanded terrorist group has more seats in the House of Commons than UKIP.

This referendum (assuming it happens) is about Prime Minister Cameron retaining the support of a group of his (mostly) non ministerial MP's who remain obsessed with the idea of leaving the EU.

UKIP is to UK politics what Fox News is to CNN. You may be entertained by it but actually there's not that much there and they both have definite agendas, which you should be very conscious of.  :(

Quote
Even aside from the referendum on the EU, Scottish and English sentiments have diverged in recent years, particularly since the Thatcher years. Cameron's comments subsequent to the Scottish referendum last year have left many Scottish who voted to stay in the union feeling that they were shafted. For unionists, the best likely outcome is now some sort of federal union, but I would not bet against it going further and a fully independent Scotland emerging in the near future.
Either preliminary work will go ahead regardless in pursuit of this policy directive or all work will be delayed pending the referendum outcome. As it is a stated goal of the BSA to increase UK experience and skill in space engineering the simple option is to go ahead

If the result is for leaving the EU and if Scotland requests a 2nd independence referendum (BTW the Houses of Parliament are the body that granted the right to hold a referendum in the first place) then that will require review. That's 2 big "if's" in a row after the big one of wheather there will be a referendum at all.

It looks like Cameron said he will, but words can be ambiguous.  :(
Quote
It is that uncertainty that will make those in power (England) very reluctant to place such a strategically important infrastructure project as the spaceport in an area that they may not have control of in 10 years.
Unless they are confident enough that the bulk of the British people will vote to stay that they are not worried.  :)
Quote
**I think the Scottish government would be happy to welcome REL to the country.**

I certainly agree with you here, but it won't be a decision left to the parliament in Scotland. This decision will be made in London.
No. It will be made in Culham.

REL is a private company. The UK Govt is a minority investor and AFAIK have no management input.

They could just as easily go to Toulouse instead.

While it could be said this is loosely relevant to SABRE/Skylons future I think it's going quite far OT.

From REL's perspective their next big events (I think) will be getting the test stand for SABRE ready and of course getting the full size flight configuration (although not I suspect flight weight) engine ready for it.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 05/11/2015 02:13 PM
Regarding the likelihood of Scotland staying in the UK, we are in disagreement. As you say it's off-topic for this thread so we'd probably best not thrash it out here.

JS19
**No. It will be made in Culham.
REL is a private company. The UK Govt is a minority investor and AFAIK have no management input.**

Yes, of course, decisions for REL will be made by REL. However the placement of the spaceport is a decision that will be made in London. REL will go wherever the spaceport goes (not Scotland IMO: See above).

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Galactic Penguin SST on 05/11/2015 03:08 PM
Hmm I am surprised that you guys are thinking that local politics could have such an effect on the development of Skylon. In fact I would suggest not going down that road here again or I might need to start to intervene.  ;)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Nilof on 05/11/2015 03:38 PM
In contrast there is limited experience of pumped LH2/LO2 engines anywhere with 4 designs in the US (and the only production design dating from the 1960's) with 2 in Europe and 1 (IIRC) in Russia.


OTOH, looking only at engines that have actually flown on orbital flights or are very likely to do so in the near future, and ignoring hot tests:

US:
RL-10
J-2
SSME
RS-68
BE-3

Russia:
KVD-1
RD-0120 series
RD-0146 series
...and a ton of incredibly crazy experimental engines such as the 30 MPa chamber pressure RD-701 which have to count for something. Though the russians have avoided LH2 stages because of excellent non-cryogenic alternatives.


Europe:
HM-7 series
Vulcain series
Vinci

Japan:
LE-5 series
LE-7 series

India:
CE-7.5

China:
YF 73 and 75 series.

...imho, while LH2 is still a PITA as far as engine development is concerned, it is not necessarily more so than the decision to use a staged combustion cycle. Virtually everyone who has been concerned with improving the performance of their rockets rather than getting something into space period, has developed an LH2 expander or gasgen at some point.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 05/11/2015 09:21 PM
Expander cycle is good for upper-stage engines.  It has a maximum thrust, and it's not very high.  If you want high T/W and high Isp in a large engine that has to operate at sea level, some form of staged combustion is by far your best bet.

The SABRE seems to dodge a lot of the problems by taking advantage of the helium loop, which would be extra weight and complexity on a pure rocket but is essentially free here because they need it for the airbreathing mode.  This should significantly attenuate the issues with seals and metallurgy.  It's still not simple to develop, but if you add the cost of the SSME to the cost of the GE90 you do blow past REL's estimate...

Oh, wait just a second; that reminds me:

That's $360M to get to first working prototype.

Excuse me; that's £360M.  Everything else I said is fine.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 05/12/2015 10:51 PM
So it seems Jo Johnson is the new minister for Space ( and some other none spacey stuff) and as such seems likely to be involved in making some of the governments decisions regarding Skylon.
 
http://en.wikipedia.org/wiki/Jo_Johnson

On the one hand this may be seen as a bad thing as the man seemingly has no more than a high school science education  but I posit this may actually be a cunning plan as he has a background in finance as well as fluent French and an MBA from INSEAD. If the government was indeed interested in assisting Reaction Engines in forming a Skylon consortium with Airbus in the next four years that could be just the sort of background you might want in the minister in charge of helping to make it happen.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/13/2015 03:35 PM

http://en.wikipedia.org/wiki/Jo_Johnson
He is also Boris Johnsons's brother.

Time will tell if this is an asset or a liability.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/13/2015 07:48 PM
I notice that Skylon's fuselage is pinched at the middle where the payload bay is. I wonder why they decided not to use a wider payload bay of ~ 6 metres. How much of a payload penalty would that involve.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 05/13/2015 08:03 PM
It's a good guess this pinch is due to Area Rule influencing the design. (http://en.wikipedia.org/wiki/Area_rule)

So if you made the payload bay wider, the rest would widen proportionally too.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RanulfC on 05/13/2015 08:58 PM
I notice that Skylon's fuselage is pinched at the middle where the payload bay is. I wonder why they decided not to use a wider payload bay of ~ 6 metres. How much of a payload penalty would that involve.
It's a good guess this pinch is due to Area Rule influencing the design. (http://en.wikipedia.org/wiki/Area_rule)

So if you made the payload bay wider, the rest would widen proportionally too.

Yes, you have to keep in mind that Skylon is more of (but not "an") an aircraft than a standard launch vehicle so flying through the atmosphere to around Mach-5 makes aerodynamics important :)

Randy
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/13/2015 08:58 PM
I hadn't heard of that before. Well you learn something every day.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 05/14/2015 08:38 AM
it would be good to have any kind of company update at this point. How is the work doing?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 05/14/2015 11:44 PM
it would be good to have any kind of company update at this point. How is the work doing?
This year they have gone crazy with the press updates, okay their been 3, which is three times more than we got in 2014.

http://www.reactionengines.co.uk/press_release.html (http://www.reactionengines.co.uk/press_release.html)

There were little updates and new pics and graphs and data release by the team at conferences but you will have to hunt them down by reading the threads on this website.

I'm not the only one that hopes when they get to the stage of testing their engine and components of the engine they will get a bit more open with us, perhaps with some nice pictures and videos. They could learn a thing or two about marketing from Space X.

The news section of their site haven't been undated since May 2014.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pmcaerospacefreighter on 05/18/2015 10:35 PM
I feel like they get a trickle of funding from the UK Govt, not enough to do anything much with it, but enough for the politicians to feel good about themselves.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/19/2015 12:00 AM
I feel like they get a trickle of funding from the UK Govt, not enough to do anything much with it, but enough for the politicians to feel good about themselves.
REL are pretty good at making a (relatively) little go a long way.

The UK governments (roughly) $94m (over 2 years) may not sound much  but it's about 1/6 of their needed budget for the work they want to do. REL are extremely wary of any government gaining a controlling interest in the project and being able to dictate design or engineering decisions.

It is enough to allow them to make significant progress on the project.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pmcaerospacefreighter on 05/22/2015 05:03 PM
a single rocket launch (I assume they need to test their engines at altitude / hypersonic speed) would eat a lot of that.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hanelyp on 05/22/2015 05:28 PM
Ram jets have been operated with inlet and exhaust nozzles not greatly different from what a sabre engine would need.  Everything in between is not directly exposed to speed and altitude, accepting hot air at one end and producing hotter air at increased pressure at the other end.  A test of the sabre cycle core needs neither high speed not now pressure ambient environment.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/22/2015 06:57 PM
a single rocket launch (I assume they need to test their engines at altitude / hypersonic speed) would eat a lot of that.
Did no one tell you what happens when you "assume" things?

The pre cooler at the front of the engine decouples the air temperature (cryogenic) and velocity (about M0.5) from the ambient environment (up to 1000c and M5.5)

Pre coolers with this power to weight ratio and ability to do frost control have never been done before, which is why this had to be tested first as a failure would have been game over for the whole project.

What that means is (unlike the SCramjets) you don't need to put it on a rocket to test its performance, although putting it on some kind of test vehicle would be a bonus.

Most of this can be found on the technical documents on the REL website.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 05/22/2015 07:38 PM
They're not putting the engine on a test vehicle during this phase of development.  Once it's proven on the test stand (yes, it gets static thrust just fine because it has a turbocompressor), the rest of the ~$5B engine development program can commence, and that might conceivably involve sticking the engine on a test vehicle (which could easily be reusable as it's essentially an airplane).

Now, they have talked about using an internally-developed sounding rocket to test nozzle ideas, but that's not quite the same thing...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 05/23/2015 08:17 PM
As other have said below much of SABRE can be ground tested, but the nacelle - with its re-entry capable nose cone - is definitely novel, critical, and will need to be proven definitively early in development either through ground testing or in flight. REL had mentioned developing an NTV - a Nacelle Test Vehicle before now, but I don’t believe it’s in the current plan.

At first blush the nacelle/inlet looks reminiscent of other flown configurations such as that used on the SR-71: it’s axisymmetric with a translating shock cone. But the fact that it can close fully and successfully resist re-entry shock/plasma/thermal conditions is new.

I did wonder if one of the purposes of the Valkyrie project was to fly a nacelle model (in closed configuration) into re-entry-like conditions.

It seems to me there are a couple of challenges with the nacelle cone and louvres.

1] The louvres need to be thin to minimize drag during air-breathing (see the attached screen shot) of a REL animation. But this thinness limits the options for thermal protection: there’s no mass/structure to sink heat into, and not much room for active thermal control.

2] The sharp tip of the cone will receive the most severe heating as it’ll be close to the shock wave, and has little volume to sink heat back into. There may be room in the cone for active cooling. Or a more drastic departure would be to swap the actual cone for an aerospike, such as that used on the Trident ICBM. (see picture from http://en.wikipedia.org/wiki/Drag-resistant_aerospike below) During atmospheric ‘forward’ flight the spike is extended to form a simulated cone, but for re-entry it’s retracted leaving the cone blunt and so better suited to face the airflow (which now comes from below).

An aerospike could also be used to alleviate heating on the sharp fuselage nose as it will face similar heating issues.

(A pre-emptive note to JohnSmith19: Please don’t take these comments and suggestions to be my dismissal of the Skylon project as impossible. Thinking through engineering challenges like Skylon is a hobby of mine, and I share my thoughts in hopes of hearing corrections when I’m mistaken.)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/23/2015 10:48 PM
At first blush the nacelle/inlet looks reminiscent of other flown configurations such that on the SR-71: it’s axisymmetric with a translating shock cone. But the fact that it can close fully and successfully resist re-entry shock/plasma/thermal conditions is new.
True.
Quote
1] The louvres need to be thin to minimize drag during air-breathing (see the attached screen shot) of a REL animation. But this thinness limits the options for thermal protection: there’s no mass/structure to sink heat into, and not much room for active thermal control.
Like a lot of things in aeospace design "it depends." Skylon is so big what looks thin as a picture may be very substantial IRL. those louvres may actually be several cms thick.
Quote
2] The sharp tip of the cone will receive the most severe heating as it’ll be close to the shock wave, and has little volume to sink heat back into. There may be room in the cone for active cooling. Or a more drastic departure would be to swap the actual cone for an aerospike, such as that used on the Trident ICBM. (see picture from http://en.wikipedia.org/wiki/Drag-resistant_aerospike below) During atmospheric ‘forward’ flight the spike is extended to form a simulated cone, but for re-entry it’s retracted leaving the cone blunt and so better suited to face the airflow (which now comes from below).
Strictly Trident use an "aero disk" but the idea is very similar. Artillery shells are probably the main users of actual "aero spike" designs.
Quote
An aerospike could also be used to alleviate heating on the sharp fuselage nose as it will face similar heating issues.

(A pre-emptive note to JohnSmith19: Please don’t take these comments and suggestions to be my dismissal of the Skylon project as impossible. Thinking through engineering challenges like Skylon is a hobby of mine, and I share my thoughts in hopes of hearing corrections when I’m mistaken.)
REL have stated that the parts needed to resist peak heating loads they would be using a version of Reinforced Carbon Carbon. This has demonstrated service up to 3000c in the Shuttle nose area, with the right surface coating. DLR is one of REL's partners and they have substantial experience in RCC.

Hopefully glass reinforced silicon carbide will be adequate for the majority of both the fuselage, wings and nacelles, but there are alternatives.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/24/2015 05:06 PM
There are a number of new things that need to be developed. These include
1. The transitioning inlet
2. lox cooled chamber
3. heat exchangers, both the primary one and the high temperature silicon carbide one.
4. active thermal protections systems on the canards and winds and perhaps the inlet.
5. an aerodynamic configuration that can fly at hypersonic speeds (mach 5), re-entry and low landing speeds.
6. super lightweight tanks that are 1% of the mass of the propellant.

Having a high number of active systems increases the probability that one of them will fail during flight and also increases the maintenance and inspection burden between flights.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RobLynn on 05/24/2015 06:12 PM
There are a number of new things that need to be developed. These include
...
6. super lightweight tanks that are 1% of the mass of the propellant.
...

From memory for C1 configuration about 220Mg LOX+LH2 and ~1000m³ LH2 and 150m³ LOX,
http://selenianboondocks.com/2010/02/calculating-propellant-mass-sensitive-term/tankmers/
At very best cryogenic tanks are about 7kg/m³, so might be as little as 8Mg - say 4-5% of propellant mass.  Not realistic to target 25% of that.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 05/24/2015 07:44 PM
There are a number of new things that need to be developed. These include
...
6. super lightweight tanks that are 1% of the mass of the propellant.
...

I don't believe I've seen this 1% tank mass requirement before. Can you point us to a source? (Or is this your own assessment?)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/24/2015 10:25 PM
If you search for "skylon hotol" then go the top link on the second page of results. The tank is a balloon tank so that helps, but the hydrogen fraction is twice that of a normal vehicle and the tanks are split into two sets of tanks, which is more inefficient.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 05/25/2015 12:19 AM
Those search terms revealed a number of interesting links (including videos of the Kerbal Space Program Skylon model that I'd not seen before) but not tank specs.

url?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/25/2015 12:50 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: hkultala on 05/25/2015 01:20 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 05/25/2015 01:34 AM
I think we're all referring to the mass budget for the C1 design on pages 32-33? That shows 2,736kg budgeted for “main tankage, cryo Insulation & supports” to carry 216,630kg of propellant.

2.7 metric tonnes for tanks does sound light, but as hkultula points out more mass for the tank can be bought from elsewhere. Also, the C1 design/budget is at least one generation out of date (two if D1 is taken forward). The optimists among us will guess that later designs have wider margins.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/25/2015 02:49 AM
Those search terms revealed a number of interesting links (including videos of the Kerbal Space Program Skylon model that I'd not seen before) but not tank specs.

url?
For those interested in tank design John Whiteheads paper makes very interesting reading.
http://www.osti.gov/scitech/servlets/purl/379977 (http://www.osti.gov/scitech/servlets/purl/379977)

Whitehead's team developed the first positive displacement pumps for what people now call micro launchers. Whitehead was (is?) looking at what it takes to build an SSTO 2 people could carry in the back of a pickup truck.

They note that "1%" tanks IE tank mass 1% of contents are possible over several orders of magnitude. LH2 is the exception but that's reduced to maybe 3% of contents mass. Tankage on LH2 vehicles is always highly deceptive. Those little red tanks on Skylon are much heavier than the huge LH2 tanks that fill most of the fuselage.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/25/2015 02:55 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.
Doubtful. That rule applies when the tanks of the LV are virtually all of the dry mass (which for ELV stages they often are)

But for Skylon you'd need to figure that as a % of the dry mass, which IIRC is something like 46 tonnes, so it's 48/46 tonnes, IE about a 4% payload hit.

Tank mass is just a much smaller fraction of dry mass in Skylon than normal ELV's.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/25/2015 03:24 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.


It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/25/2015 04:00 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.

It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth overall. However some of those will be tighter as there is quite a lot of data on horizontal cryogenic tanks for road and rail tankers. [EDIT Likewise large parts of the turbo machinery are well understood, so the margins for their design are narrower than they would have been say 40 or even 20 years ago. The less well understood sections have wider margins. ]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/25/2015 04:02 AM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.

It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth. However some of those will be tighter as there is quite a lot of data on horizontal cryogenic tanks for road and rail tankers.

road and rail tankers? Seriously?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 05/25/2015 09:29 AM
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth overall.

You sure?  I know C1's truss structure had a 15% margin, and I know D1 was said to be designed with margins "consistent with" AIAA guidelines which implies at least 15% and probably more for the stage I tentatively judged the design to be at when I last attempted to figure this out, but I'm not aware of a concrete official number for the overall mass margin.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/25/2015 09:42 AM
There are a number of new things that need to be developed. These include
Drawing from various REL presentations I'll mention when REL looked at a particular area.
Quote
1. The transitioning inlet
Ongoing since 2012. Inlets with moving centre bodies have been around since the late 50's.
Quote
2. lox cooled chamber
2010. Also the use of air cooling for the cooling while the vehicle is air breathing.
Quote
3. heat exchangers, both the primary one and the high temperature silicon carbide one.
Under study since 2002.
Quote
4. active thermal protections systems on the canards and winds and perhaps the inlet.
Not mentioned. However transpiration cooled rentry vehicles have flown in flight tests in the late 1970's and reports are available in the open literature.
Quote
5. an aerodynamic configuration that can fly at hypersonic speeds (mach 5), re-entry and low landing speeds.
Under development since the late 80's. Making  your fuselage circular, contouring it front to back for low supersonic drag and sticking the major point masses in the middle makes life a lot easier right from the first moment. Although cross range was not (AFAIK) a design driver it's given got most (if not all) of the Shuttles target (but never achieved) cross range.
Quote
6. super lightweight tanks that are 1% of the mass of the propellant.
Outside of LH2 a tank weighing 1% of its payload is not that difficult in the aerospace field.
Quote
Having a high number of active systems increases the probability that one of them will fail during flight and also increases the maintenance and inspection burden between flights.
Which logically makes the Wright Flyer the safest aircraft every built, as there's so little to wrong, right?  :)
Or maybe not.

You might like to look out the window at the leading edge of an airliner when it lands or takes off.

There's a lot of "active systems" in play during that period, and  if any of them move in the wrong way (or fail to move at all) you're going to have a  very bad day.

And yet every day millions of passengers risk their lives to those active systems without thinking about it.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pmcaerospacefreighter on 05/25/2015 04:31 PM

The pre cooler at the front of the engine decouples the air temperature (cryogenic) and velocity (about M0.5) from the ambient environment (up to 1000c and M5.5)


So what you are telling me is that the first Skylon prototype will take off from a runway and proceed onto test flights at regimes that progressively get closer and closer to space flight?
i would love to see that happen.  But it sounds like a great risk to test the whole airframe-engine combination over such large range of regimes, when we are not talking about a relatively simple rocket but a RBCC or whatever they're using.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: hkultala on 05/25/2015 08:21 PM
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.
Doubtful. That rule applies when the tanks of the LV are virtually all of the dry mass (which for ELV stages they often are)

But for Skylon you'd need to figure that as a % of the dry mass, which IIRC is something like 46 tonnes, so it's 48/46 tonnes, IE about a 4% payload hit.

Tank mass is just a much smaller fraction of dry mass in Skylon than normal ELV's.

What rule are you talking about?

What goes to orbit is (dry mass + payload).

If either grows, another must shrink. By same absolute amount, not any percentage.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/25/2015 08:40 PM
road and rail tankers? Seriously?
One of the hallmarks of solid engineering is a focus on using advanced technology only where necessary.  A similar example would have been the pilots position for the SR71.  The vehicle set the standard for materials, engine cycles and sensors for at least a decade yet the core flying and engine controls were, AFAP, those of a standard twin jet aircraft of the time.

Despite 20+ years of work composite LH2 tanks still seem to have significant leakage levels.

If you don't need them, why use them?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Soundbite on 05/26/2015 02:36 PM
Hi All,

I dont' know if anyone noticed the patents that Reaction Engines has filed on 1 December 2014.  There are two that I can see but I haven't searched for anymore

They are found on page https://www.ipo.gov.uk/p-gcp?lastResult=40&perPage=10&filter=&sort=GCP+Request+Date (https://www.ipo.gov.uk/p-gcp?lastResult=40&perPage=10&filter=&sort=GCP+Request+Date)

The Details are found here https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318111.0 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318111.0) and here ://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6 (http://://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6) and then by clicking on the "Documents" link on the right hand side of these pages in the Window titled Select case view
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Soundbite on 05/26/2015 03:11 PM
Oops.... the last link address is faulty  :(

Try this https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6) and I also found these https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318098.9 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318098.9) and https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318109.4 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318109.4) submitted on 12 January 2015
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 05/26/2015 07:42 PM
That's interesting news regarding the patents. I thought I heard somewhere that REL didn't want to patent the tech because they didn't want the information in the public domain. Is that memory of mine mistaken?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 05/26/2015 08:14 PM
I haven't gone over them in detail (patent-ese makes my eyes bleed), but one thing jumped out at me - there are two separate patents for two different engine configurations, and one of the says:

Quote
A rocket engine is provided. The engine comprises: a rocket combustion chamber [...] and and air-breathing combustion chamber [...]. [They] are configured to be operated indepedently

That's new, isn't it? judging from the diagrams, they're concentric, sharing the same nozzle. Poss connected to the Valkyrie work?

There also seems to be some changes to the cooling loops in this version from the diagrams we've seen before, but I haven't puzzled out what the practical difference is.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 05/26/2015 08:55 PM
here's (http://i.imgur.com/7lSH3Ak.gif) a half-assedly recoloured version of the diagram. the one things that jumps out at me is that the pre-burner.

The biggest difference I can spot is that in previously-described cycles, the cooled/compressed air is split between the nozzle and the pre-burner, and all the hydrogen flows through the pre-burner (i.e. the output from the pre-burner is hydrogen-rich). In this cycle it's the other way round. I'm not sure I could tell you what that signifies, though.

EDIT: ah-ha! looks like the frost-control cat is out of the bag.

Quote
an air intake [...] which includes a first heat exchanger for cooling incoming air, a water separator downstream of the first heat exchanger, a liquid oxygen injector downstream of the the water separator and a second heat exchanger downstream of the liquid oxygen injector. The injector reduces the airflow temperature so that water remaining in the airflow is converted to small dry ice crystals. [...] the liquid oxygen is used to reduce the temperature of the flow from between 5º and 13ºC to minus 50ºC or lower, such that a considerable amount of liquid oxygen needs to be used

hrm, interesting. how much is "considerable"? and how does this apply to self-ferry and/or Scimitar?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 05/26/2015 09:52 PM
That's interesting news regarding the patents. I thought I heard somewhere that REL didn't want to patent the tech because they didn't want the information in the public domain. Is that memory of mine mistaken?

I seem to remember that too. Elon Musk definitely said that. Did REL say it too? Hmmm... Someone here will answer this soon.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/27/2015 06:10 AM
here's (http://i.imgur.com/7lSH3Ak.gif) a half-assedly recoloured version of the diagram. the one things that jumps out at me is that the pre-burner.


EDIT: ah-ha! looks like the frost-control cat is out of the bag.
hrm, interesting. how much is "considerable"? and how does this apply to self-ferry and/or Scimitar?
I think the usual expression in patenese is "to those skilled in the art."  :)

The HX patent GB2519147 does go into considerable detail on how to solve the frost control problem.

One of the neatest parts is use of a solution of Methanol as anti freeze which gets sprayed and recollected as you move through the HX, allowing the Methanol to be recycled. This is a neat way to save on a non propellant consumable which over a full flight could be quite heavy.

Note using some LOX would be OK for SABRE but a definite problem for LAPCAT. Airliners don't (AFAIK) carry it at all. They tap the engine in flow for any air they need for cabin aircon.

Note 2 things about the HX patent.

They describe a way to solve this problem. It's probably what REL are using, but it might not be.

Anyone with any knowledge of mfg engineering will know that while what you have to make is described in quite a lot of detail it assumes you already have access to large amounts of specialized materials. In this application how you make it was as difficult a problem as what to make.

[EDIT A note about the British patent pages. They are in ascending order going down. The full patent document is usually the largest item at the end.  That's what's been patented.

My quick read of the "engine" patent is that the patent states the 3 diagrams show the same engine in different modes. It shows 2 combustion chambers because that's how the real SABRE works and the thing at the top is the "spill ramjet" used to reheat bypassed air as the engine speeds up. ]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 05/27/2015 08:48 AM
Look again- there are two engine patents describing different configurations (SABRE 3 vs SABRE 4 perhaps?). One is similar (but more detailed) to what we've seen before; the other describes the twin combustion chambers in addition to the bypass duct.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/27/2015 01:11 PM
Look again- there are two engine patents describing different configurations (SABRE 3 vs SABRE 4 perhaps?). One is similar (but more detailed) to what we've seen before; the other describes the twin combustion chambers in addition to the bypass duct.
My mistake. It was only when I ran over all the patent links I found the 2nd one, ending  -155 rather than -152.

Parallel combustion chambers and the ability to side step frost control.

This sounds like the Scimatar engine for the lapcat M5 airliner but I'm not quite sure why you need rocket combustion chambers at all.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/28/2015 09:01 PM
Hi all, first time poster, long time lurker.

Seems there's more patents on the WIPO site that just recently got published that are also a little easier to read due to OCR and to refer back and forth to the drawings with:

1. 20150104316 TURBINE BLADES   US   16.04.2015
F01D 11/00   14296611   Reaction Engines Ltd.   Richard Varvill

2. 20150101308 ENGINE   US   16.04.2015
F02K 9/78    14296620   Reaction Engines Ltd   Alan Bond

3. 20150101333 ROTATIONAL MACHINE   US   16.04.2015
F02C 6/16     14296615   Reaction Engines Ltd   Alan Bond

4. 20150102129 MOUNTING ASSEMBLY   US   16.04.2015
F02K 9/84     14296618   Reaction Engines Ltd   Alan Bond

5. 20150101342 ENGINE   US   16.04.2015
F02C 7/228  14296624   Reaction Engines Ltd   Alan Bond

6. 20150101337 NOZZLE ARRANGEMENT FOR AN ENGINE   US   16.04.2015
F02K 9/97     14296628   Reaction Engines Ltd   Alan Bond

7. 20150101334 HEAT EXCHANGERS   US   16.04.2015
F02C 7/141   14296603   Reaction Engines Ltd   Alan Bond

Just do a search on "reaction engines ltd" including the quotes at https://patentscope.wipo.int/search/en/search.jsf

From what I've read and understood (IANARS - I am not a rocket scientist) I've understood the frost control (#7) to be the following:
Incoming air cooled down to a little above freezing passes over several layers of the thin tubes. Some methanol is mixed into the air flow around here. It then passes over a set of thicker tubes (Fig 13 &14) wrapped with a mesh that catches 95% of the liquid/moisture. It then passes through the remaining thin tubes and any remaining water/methonal gets crystalised as the air drops to the -150 C. Something I don't fully understand (methonol? very low water content?) causes the formation of crystals rather than the furry frost that would otherwise block the heat exchanger. I think there is then a recovery and recycling of the captured methanol to re-inject into the airflow. Figure 19D shows the thin and thick tubes, and 520 on the image shows the air travelling inwards.

To contradict momerathe, the section he quotes is from the background section and describes a different patent. I don't think REL's solution injects liquid oxygen at all, but I haven't read it in it's entirety, so apologies if I'm wrong.

In #2, #5 and #6 where the engines and nozzle arrangements are described and shows two nested nozzles. I think this may be a novel alternative to an expansion deflection rocket. The inner nozzle is for full on rocket mode. In air breathing mode the outer nozzle is used, and the rocket nozzle acts like the expansion deflection pintel.

Hope that was a useful first post  :)

[Edit] Rereading it seems the crystallization happens through sublimation, although surely that's the wrong word? Sublimation = Solid -> Gas, don't they mean Deposition = Gas -> Solid
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/28/2015 09:07 PM
 :-[ Missed the bit where JS19 had already picked up and ID'd the use of methanol. Please ignore me trying to sound clever on that bit.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: zodiacchris on 05/28/2015 09:21 PM
Welcome Oddbodd! Good first post indeed  8)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/28/2015 09:45 PM
#4 the mounting assembly patent, Fig 2. Do my eyes deceive me, or is that a drag resistant aerospike? First time I've seen that in a drawing/image. I think someone might have mentioned it as a possible option previously though.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 05/28/2015 11:05 PM
Looks like one of their really old pictures of SABRE (see Figure 6 in Varvill & Bond (2003) (http://www.reactionengines.co.uk/tech_docs/JBIS_v56_108-117.pdf)).  The newer models all have a simple conical forebody.  Doesn't mean that's what they're going with, of course...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/28/2015 11:24 PM
In #2, #5 and #6 where the engines and nozzle arrangements are described and shows two nested nozzles. I think this may be a novel alternative to an expansion deflection rocket. The inner nozzle is for full on rocket mode. In air breathing mode the outer nozzle is used, and the rocket nozzle acts like the expansion deflection pintel.

Hmmm. Actually read it properly now, and it's even more interesting. It actually translates. The smaller inner nozzle cone moves back (relative to direction of travel), creating an annular flow for separate air breathing combustion chambers arranged around the central axis. On transition to rocket mode the smaller nozzle cone moves forward, with the larger truncated nozzle cone section extending the smaller one. In this mode the rocket combustion chamber of the smaller nozzle cone is used. But the point stands that it is using the smaller nozzle cone as a pintel to create the annular flow for higher efficiency across altitudes.  8)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/28/2015 11:45 PM
I really need to go to bed  :D

http://worldwide.espacenet.com/searchResults?ST=singleline&locale=en_EP&submitted=true&DB=worldwide.espacenet.com&query=%22reaction+engines+ltd%22 (http://worldwide.espacenet.com/searchResults?ST=singleline&locale=en_EP&submitted=true&DB=worldwide.espacenet.com&query=%22reaction+engines+ltd%22)

Mostly looks like overlap, with the same 7 US ones I posted before, a couple of additional GB ones, but probably overlap the US ones, and one WO one for engine ducts.

Looks like they're all originally from back in 2013, although it seems the international stuff was applied for mid last-year.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Seer on 05/28/2015 11:53 PM
Anyone want to have a guess as to how much helium is carried? I tried to estimate it from various RE mass budgets but could never get a particularly precise number. Is it possible to estimate it from first principles? I.e knowing the pump pressure and thrust of the main engines?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 05/29/2015 12:32 AM
Looks like one of their really old pictures of SABRE (see Figure 6 in Varvill & Bond (2003) (http://www.reactionengines.co.uk/tech_docs/JBIS_v56_108-117.pdf)).  The newer models all have a simple conical forebody.  Doesn't mean that's what they're going with, of course...

Ah yes, that's long before I'd even heard of REL/Skylon etc. Now I think about it maybe someone mentioned it disrupting flow into the engine, which would explain it's absence in newer images.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/31/2015 07:59 AM
:-[ Missed the bit where JS19 had already picked up and ID'd the use of methanol. Please ignore me trying to sound clever on that bit.
Welcome to the forum. Your patent list has brought a lot to the party and gives much food for thought.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/31/2015 08:03 AM
Anyone want to have a guess as to how much helium is carried? I tried to estimate it from various RE mass budgets but could never get a particularly precise number. Is it possible to estimate it from first principles? I.e knowing the pump pressure and thrust of the main engines?
The key issue would be what is the peak amount of heat (set by the air mass and temperature) you have to move around the cycle and at what temperatures and pressure do you have to work with.

Probably possible from first principles and the data in the Skylon C1 trajectory spreadsheet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: FutureSpaceTourist on 05/31/2015 08:58 AM
That's interesting news regarding the patents. I thought I heard somewhere that REL didn't want to patent the tech because they didn't want the information in the public domain. Is that memory of mine mistaken?

I seem to remember that too. Elon Musk definitely said that. Did REL say it too? Hmmm... Someone here will answer this soon.

Yes, Reaction Engines have always said they would never apply for UK ones because of what happened with HOTOL (ie patents ended up restricted to military on national security grounds). I guess they've decided that to protect themselves from potential U.S. involvement/applications they need US ones?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: FutureSpaceTourist on 05/31/2015 10:32 AM
Oops.... the last link address is faulty  :(

Try this https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6) and I also found these https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318098.9 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318098.9) and https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318109.4 (https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318109.4) submitted on 12 January 2015

Ok, so my previous post is obviously out of date - I hadn't caught up enough on this thread!

I'm guessing the legal situation in the UK has changed and/or the more favourable support from the UK government (£60M funding) has made Reaction Engines confident enough now to patent. It's great that there is now a lot more technical info in the public domain, if only I had enough engineering expertise to understand it  :D
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 05/31/2015 12:16 PM
either way - now the patents are out there, the clock is ticking.. I just hope this means they're confident they can execute on their roadmap.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 05/31/2015 03:41 PM
either way - now the patents are out there, the clock is ticking.. I just hope this means they're confident they can execute on their roadmap.

I don't think REL have every really doubted their ability to build SABRE provided a)The pre cooler worked as expected and b) The could get the funding.

The pre cooler has now been extensively tested and worked as expected. Progress milestones then depend on their getting the necessary funding when it's needed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 05/31/2015 04:33 PM
I think these patent applications are an interesting development. Why have REL decided to submit patents when previously they said they wouldn't?

My guess is that it may have had to do with securing funding. Perhaps a major potential investor said they'd only invest if they felt that they could protect their investment from being upstaged by copy-cat designs ie have the technology protected by patents.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 05/31/2015 08:33 PM
I think these patent applications are an interesting development. Why have REL decided to submit patents when previously they said they wouldn't?

My guess is that it may have had to do with securing funding. Perhaps a major potential investor said they'd only invest if they felt that they could protect their investment from being upstaged by copy-cat designs ie have the technology protected by patents.

Another aspect is that they have to start thinking about who will make the bits. If they can't make absolutely everything themselves then it may be hard to hide all their secrets. Inference might be enough to help someone guess in the end.

Another aspect is that the more people they hire, the harder it has to be to ensure that no secrets could ever leak out.  Someone leaves the company, having stumbled across something they should not know, for example.  What can you do in such a case?

Another aspect is that the more interest they generate, the more attention they attract, the more some other clever people may be able to work out what they are doing anyhow.

Finally, I can't imagine that REL haven't been the targets of some degree of espionage.   Would any country with strategic interests in space not at least want to know if they were onto a good idea? The patents will at least make it clear what REL really did invent so that copycats can be sanctioned in some way.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Soundbite on 05/31/2015 09:38 PM
Reaction Engines has just posted a news update on Mark Thomas joining the Board http://www.reactionengines.co.uk/news_updates.html (http://www.reactionengines.co.uk/news_updates.html)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/01/2015 10:33 AM
Another aspect is that they have to start thinking about who will make the bits. If they can't make absolutely everything themselves then it may be hard to hide all their secrets. Inference might be enough to help someone guess in the end.
In some ways the simplest motivation is that it can be done at all encourages people to try finding out how.
Quote
Another aspect is that the more people they hire, the harder it has to be to ensure that no secrets could ever leak out.  Someone leaves the company, having stumbled across something they should not know, for example.  What can you do in such a case?
Other business have been built on trade secrets. Whitehead's torpedoes worked on them. The disk drive business was built on the ability to coat the platters with a magnetic layer. The precise details of this process used by each mfg have always been a closely guarded set of techniques, as both the chemistry and the morphology of the layer is critical. typically a new entrant would hire key staff from existing players to acquire this information.
Quote
Another aspect is that the more interest they generate, the more attention they attract, the more some other clever people may be able to work out what they are doing anyhow.

Finally, I can't imagine that REL haven't been the targets of some degree of espionage.   Would any country with strategic interests in space not at least want to know if they were onto a good idea? The patents will at least make it clear what REL really did invent so that copycats can be sanctioned in some way.
Logically yes.

Practically the most effective protection has probably been that people have been obsessed with SCRamjets, to the point they simply don't think it's possible for this to work, and  if it is, to deliver the performance claimed.

While that was the consensus I doubt anyone could be made to try intelligence collection.

That position should be changing and I hope REL will plan accordingly.

I'll remind people that it's one thing to explain what has to be done. It's quite another to explain how it's done. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aameise9 on 06/04/2015 04:39 PM
Reaction Engines has just posted a news update on Mark Thomas joining the Board http://www.reactionengines.co.uk/news_updates.html (http://www.reactionengines.co.uk/news_updates.html)

Bump.  Perhaps some of our Brits would care to comment?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/05/2015 05:17 AM
Reaction Engines has just posted a news update on Mark Thomas joining the Board http://www.reactionengines.co.uk/news_updates.html (http://www.reactionengines.co.uk/news_updates.html)

Bump.  Perhaps some of our Brits would care to comment?

I don't know anything special but there's a more extended biography of him here:

http://aerosociety.com/Events/Event-List/1577/Rolls-Royce-future-developments-in-engine-technology

Rolls Royce has been making people redundant recently, though from what I read these are precision machining jobs.  I do also remember reading that they planned to spend a bit less on research after something of a "splurge" recently.  So based on those two things you could make a guess that some interesting work could have been cancelled and SABRE development might seem attractive compared to what's left at Rolls. I know absolutely nothing about it and am speculating utterly.

The other speculation one could make is that he is being sent out as part of a kind of "deal" a bit like the Microsoft-Nokia thing with Stephen Elop. I only mention it because I experienced it.  I don't know whether that would be a cheering thing or not. At least you can say that RE includes some people who have worked for Rolls Royce so presumably they know each other at least by reputation and that increases the possibility of things happening.

Here is a quote of the link above:
Quote
Mark Thomas, CEng, FRAeS

Mark is Chief Engineer for Technology and Future Programmes in the Rolls-Royce Civil Large Engines Business. He leads the Engineering teams responsible for the exploration and concept design of next generation propulsion systems; also the execution of system level demonstrators to deliver innovative technologies meeting future product requirements.

In 2014 Mark will celebrate 25 years with Rolls-Royce, joining the Company in 1989 as a sponsored Undergraduate trainee before completing an Engineering degree at Queens’ College, Cambridge University.

Mark’s career started in the Rolls-Royce Defence Aerospace Business and he has completed a variety of Engineering and Management roles located in the UK and Germany.

Notable roles have included Chief Development Engineer for the EJ200 (Typhoon) Engine, Programme Executive for UK Defence Research and Technology, Chief Engineer for the EJ200 (Typhoon), RB199 (Tornado) & Adour (Hawk/Jaguar) engine programmes, and Technical Director of the Eurojet Turbo GmbH consortium based in Munich.

As a Chief Engineer in Defence, Mark was responsible for the support of around 3,000 engines worldwide with 25 Military Operators ranging from the US Navy to Royal Australian Air Force.

In 2009 Mark moved to the Civil Aerospace Business in Derby to take up the role of Chief Engineer for the Trent 900 (Airbus A380), leading the team during an especially challenging three year period for the programme, working closely with Airbus and Airline Customers.

Mark is a Chartered Engineer, Fellow of the Royal Aeronautical Society and also a Governor of a flourishing Engineering Academy. He mentors a number of engineers in Rolls-Royce and is a key member of the Rolls-Royce Senior Engineering Leadership team.

Mark is married with two teenage sons and one daughter and lives in Leicestershire. Outside work he enjoys skiing, travel and reading.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 06/07/2015 01:49 AM
The other speculation one could make is that he is being sent out as part of a kind of "deal" a bit like the Microsoft-Nokia thing with Stephen Elop. I only mention it because I experienced it.  I don't know whether that would be a cheering thing or not. At least you can say that RE includes some people who have worked for Rolls Royce so presumably they know each other at least by reputation and that increases the possibility of things happening.
Nokia had serious problems with timely delivery and was in need of a good shake-up. However Stephen Elop was either a trojan with a not-so-secret mission to devalue Nokia to the point where Microsoft could buy it for peanuts, or he was a grotesquely incompetent charlatan being paid obscene amounts for negative results! Under his tenure every metric went drastically down; revenue, profit, unit sales, share price. For this he was rewarded with $18m bonus and a new VP position at Microsoft. Even now, after the purchase by the 800-lb gorilla and the associated benefits that brings, I still rarely see Nokia/Windows phones in the wild here in Germany/UK.

I think Bond and co. are experienced enough (and wary enough) to avoid a debacle like Nokia's happening to REL. However I don't think they (Bond & Thomas) overlapped at RR so I sincerely hope there isn't some kind of predatory nature to Mark Thomas' appointment. It would be tragic for some Machiavellian skulduggery to strangle the Skylon in utero. Skylon may fail to fly, but if so that should be because very clever people failed to make the science work; not because some manager looks at some numbers in a spreadsheet, and decides to burn the place to the ground to "rescue" it.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 06/07/2015 08:12 AM

The other speculation one could make is that he is being sent out as part of a kind of "deal" a bit like the Microsoft-Nokia thing with Stephen Elop. I only mention it because I experienced it.  I don't know whether that would be a cheering thing or not. At least you can say that RE includes some people who have worked for Rolls Royce so presumably they know each other at least by reputation and that increases the possibility of things happening.
Nokia had serious problems with timely delivery and was in need of a good shake-up. However Stephen Elop was either a trojan with a not-so-secret mission to devalue Nokia to the point where Microsoft could buy it for peanuts, or he was a grotesquely incompetent charlatan being paid obscene amounts for negative results! Under his tenure every metric went drastically down; revenue, profit, unit sales, share price. For this he was rewarded with $18m bonus and a new VP position at Microsoft. Even now, after the purchase by the 800-lb gorilla and the associated benefits that brings, I still rarely see Nokia/Windows phones in the wild here in Germany/UK.

I think Bond and co. are experienced enough (and wary enough) to avoid a debacle like Nokia's happening to REL. However I don't think they (Bond & Thomas) overlapped at RR so I sincerely hope there isn't some kind of predatory nature to Mark Thomas' appointment. It would be tragic for some Machiavellian skulduggery to strangle the Skylon in utero. Skylon may fail to fly, but if so that should be because very clever people failed to make the science work; not because some manager looks at some numbers in a spreadsheet, and decides to burn the place to the ground to "rescue" it.

The whole thing is pretty baseless speculation and the Nokia/Microsoft business was done to death at the time in the relevant forums without digging it up again here.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aameise9 on 06/07/2015 08:42 AM

The whole thing is pretty baseless speculation and the Nokia/Microsoft business was done to death at the time in the relevant forums without digging it up again here.

The main message seems to me that Mark Thomas is a very senior and very serious engineer who knows how to build engines ...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 06/07/2015 12:43 PM


The whole thing is pretty baseless speculation and the Nokia/Microsoft business was done to death at the time in the relevant forums without digging it up again here.

The main message seems to me that Mark Thomas is a very senior and very serious engineer who knows how to build engines ...

And surely that's all that matters.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/07/2015 02:26 PM
Star One
**The whole thing is pretty baseless speculation and the Nokia/Microsoft business was done to death at the time in the relevant forums without digging it up again here.**

He brought it up, not to discuss the Nokia/Microsoft issue itself, but just to highlight a point. He didn't say that the unsubstantiated speculation about Stephen Elop was true, just that he hoped that it wasn't something that might happen at REL with Mark Thomas.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: A_M_Swallow on 06/07/2015 04:07 PM


The whole thing is pretty baseless speculation and the Nokia/Microsoft business was done to death at the time in the relevant forums without digging it up again here.

The main message seems to me that Mark Thomas is a very senior and very serious engineer who knows how to build engines ...

And surely that's all that matters.

No. The boss, unlike the chief engineer, also needs to be able to sell engines for a profit.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/07/2015 05:56 PM
And surely that's all that matters.
No. The boss, unlike the chief engineer, also needs to be able to sell engines for a profit.
And raise a very significant amount of funding.

And drive the formation of the airframe consortium.

Without a single wealthy investor who can eliminate part of this funding issue fund raising is a pretty serious part of running a company like this to deliver the results within a reasonable time frame.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 06/07/2015 06:17 PM

And surely that's all that matters.
No. The boss, unlike the chief engineer, also needs to be able to sell engines for a profit.
And raise a very significant amount of funding.

And drive the formation of the airframe consortium.

Without a single wealthy investor who can eliminate part of this funding issue fund raising is a pretty serious part of running a company like this to deliver the results within a reasonable time frame.

Well I trust their judgement on this when it comes to their choice of senior personnel.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 06/08/2015 11:48 AM
The other speculation one could make is that he is being sent out as part of a kind of "deal" a bit like the Microsoft-Nokia thing with Stephen Elop. I only mention it because I experienced it.  I don't know whether that would be a cheering thing or not. At least you can say that RE includes some people who have worked for Rolls Royce so presumably they know each other at least by reputation and that increases the possibility of things happening.
Nokia had serious problems with timely delivery and was in need of a good shake-up. However Stephen Elop was either a trojan with a not-so-secret mission to devalue Nokia to the point where Microsoft could buy it for peanuts, or he was a grotesquely incompetent charlatan being paid obscene amounts for negative results! Under his tenure every metric went drastically down; revenue, profit, unit sales, share price. For this he was rewarded with $18m bonus and a new VP position at Microsoft. Even now, after the purchase by the 800-lb gorilla and the associated benefits that brings, I still rarely see Nokia/Windows phones in the wild here in Germany/UK.

I think Bond and co. are experienced enough (and wary enough) to avoid a debacle like Nokia's happening to REL. However I don't think they (Bond & Thomas) overlapped at RR so I sincerely hope there isn't some kind of predatory nature to Mark Thomas' appointment. It would be tragic for some Machiavellian skulduggery to strangle the Skylon in utero. Skylon may fail to fly, but if so that should be because very clever people failed to make the science work; not because some manager looks at some numbers in a spreadsheet, and decides to burn the place to the ground to "rescue" it.

well, I must say I really like nokia/windows phones! they are basically a mobile terminal of my laptop.

besides, i m not sure about the relation with RR. there is one thing that REL needs, and it's capital. Possibily, cheap friendly capital. RR has it, quite a lot. And RR's people know pretty well how to raise capital. That's the single most important thing for REL now, and it's on it that the game is played. So a bit of engagement from RR wouldn't be necessarily negative I believe.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 06/14/2015 01:31 PM
I've changed from saying - the answer is Skylon, now what's the question (for about 30 years) - until more more recent times (and on these threads) when I still say this, but... Elon Musk...

When's European Space going to see reality slapping it hard in the face, bite the bullet and figure it's **** or bust? ULA are going to be decimated by SpaceX and they're not the only ones. China and Japan are reacting now too.

http://www.wsj.com/articles/spacex-and-the-russian-rocket-mess-1434149145

ESA haven't got a BFR (Mars mega-rocket) in planning anyway so it's not as if doing Skylon hinders any of their plans. Moreover if the technology works who knows what leads that will give European aerospace?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/15/2015 06:55 AM
I've changed from saying - the answer is Skylon, now what's the question (for about 30 years) - until more more recent times (and on these threads) when I still say this, but... Elon Musk...

When's European Space going to see reality slapping it hard in the face, bite the bullet and figure it's **** or bust? ULA are going to be decimated by SpaceX and they're not the only ones. China and Japan are reacting now too.
Part of it is the way the European system differs from the US model.

Since there was only one European launcher to begin with they have never had the painful issue of phasing out an LV design.

Keep in mind Ariane 5 has been commercially successful in the global launch market where Delta IV has not, and they are both 2 stage LH2/LO2 designs with SRBs, with engines designed and built specifically for the vehicle. Ariane even uses common bulkhead tanks, which some people believe are very difficult to do (which they are, unless you read up on the extensive literature NASA generated working out how to make it work).

Large corporations react slowly to (potentially) radical change.

I think it's interesting that Airbus started their recovery project in 2010, five years ago. That suggests someone thought it prudent to have something in the bag in case this happened.

You also need to look at it from the Airbus PoV. In 2011 SX releases a video showing full recovery of an F9. By 2014 Musk is saying that's not economically possible (why it's not remains unanswered) so at least some of the senior management can claim "See, he was bluffing, they are not serious." Shotwells comments on the NATO presentation, when she stated a comm sat launch to GEO is about $100m (basically what Arianespace charge with a rideshare) would also support their argument.

I consider this a "doctrine of impotence" as RV Jones put it. It's comforting and dangerously complacent.

The trouble is Skylon has a lot of risk associated with it, relative to a a nice, well understood architecture like the TSTO ELV. That's important for pan European designs incorporating a lot of multiple governments money. Right now there isn't even a "Skylon making company" for ESA to pass money to. Likewise there is no entity you can contact and say "I'd like to buy a Skylon, what's it cost and how big a down payment do you need?"

You might think of A6 as the "comfort" design for the next generation European LV.  :(

ESA faces a mighty problem. It's under pressure to reduce it's form of "assured access" payments to Arianespace. A6 is designed to be cheaper to make and sell and be easier to find payloads for as you don't need to do rideshares to make its price reasonable.

But if A6 is not cheap enough or lacks performance it will loose out. OTOH F9's GTO performance is to the low end of flights so the question is should Europe be worried now?

If you look behind the SX PR machine can't put the bigger comm sats into GTO and that combination is where the money is. It also explains why SX is keen to get into NSS, as that's a captive market for US only LV's.

The trouble with this rather comforting world view is that it ignores Musks intent and that while F9 is not quite big enough to get large comm sats to orbit FH will be.

So ESA can't justify making SABRE/Skylon it's primary for the NGLV, but based on REL's expansion (a 3600x increase in funding over the last 15 years) and it's ability to deliver on each of its goals close to time and budget it would seem possible that it could supply some funding on an ongoing basis.


Title: News
Post by: JN on 06/15/2015 11:17 AM
News update on the website: Rocket Testing Underway

- PRESS RELEASE -

Monday 15 June 2015

Reaction Engines Ltd. have begun their latest round of rocket engine testing in Westcott, UK.

The SABRE engine requires a novel design of the rocket engine’s thrust chamber and nozzle to allow operation in both air-breathing and rocket modes, as well as a smooth transition between the two. The Advanced Nozzle project is demonstrating the feasibility of this concept and represents a significant technology development effort towards the SABRE demonstrator engine.

The test engine, which has been successfully fired 15 times during its initial commissioning phase in spring 2015, incorporates several new technologies including a 3D printed, actively cooled propellant injector system. Aerodynamic data collected from the firings is being used to validate in-house computational modelling and advance the nozzle design. The test campaign is being operated by Airborne Engineering Ltd in Westcott, Buckinghamshire. Operations are planned to continue throughout 2015, including long duration burns and tests investigating the transition between air- breathing and rocket operation planned for later in the year.

Dr Helen Webber, Reaction Engines’ Project Lead for the Advanced Nozzle Programme, commented: “This experimental engine is an important step into a new era of propulsion and space access. We are using it to test the aerodynamics and performance of the advanced nozzles that the SABRE engine will use, in addition to new manufacturing technologies such as our 3D-printed injection system.

The testing of new propulsion technology has required close work with our partners at Airborne Engineering, in order to make a test rig that can simulate the unique and demanding range of conditions required to put this engine through its paces. Despite being much smaller than SABRE, this engine is still the largest bi-propellant engine to be tested at Westcott for over thirty years, and it is exciting to see the resurgence of Westcott as the centre for UK rocket propulsion research and development. The next few months will see us running the engine for much longer periods in order to explore the transition between the air-breathing and rocket modes of the SABRE’s flight - an important and challenging part of powering Skylon into space.”

There's a video as well: http://www.reactionengines.co.uk/vid_stoicfiring.html

Enjoy!
Title: Re: News
Post by: t43562 on 06/15/2015 11:57 AM
- PRESS RELEASE -

Monday 15 June 2015

Reaction Engines Ltd. have begun their latest round of rocket engine testing in Westcott, UK.

I shouldn't complain because news is great to have :-) but ..... I can't resist a quick moan about the way the url for news updates doesn't have a link for each specific story.  i.e. it's www.reactionengines.co.uk/news_updates.html for everything.

This does make it difficult reposting stories sometimes as various other system such as facebook expect a link to link to the same text next week as it does this week.  It's just generally difficult because after some time any link will be wrong.

</moan>

Anyhow it's great news :-)

I wonder if STOIC is still an expansion-deflection nozzle?  I assume so.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: JN on 06/15/2015 12:38 PM
Point taken  - I'm working on some major fixes for the website. It'll be a while yet, but watch this space! (excuse the pun...)
Title: Re: News
Post by: john smith 19 on 06/15/2015 02:20 PM
I wonder if STOIC is still an expansion-deflection nozzle?  I assume so.
According to the REL update at the IAC (IAC-13,D2,4,6,x19609) STOIC is the hot fire version of the STRIDENT cold flow test test chamber, itself developed from the initial STRICT chamber and CFD models calibrated from STRICT tests. All of this is around E/D nozzles.

So yes an E/D nozzle, but incorporating a)Active cooling. AFAIK all  AE engines have been heat sink designs made from big billets of Copper. b) Probably including both air and O2 cooling to simulate the switch over in flight.

Making this the first tri-propellant thrust chamber test in the UK  :)

I've always had a thing about "transitions" in systems. My instinct has always been the air/LOX shift in the chamber and things like the final sealing of the inlet by the spike and its sealing rings would be the place where "unknown unknowns" would be prone to lurk in this system to bite you.

These tests look like they will tackle that issue head on.

If I'm reading the press release correctly STOIC will therefor do a full duration burn (a little over 16 mins) starting in air/H2 and shifting to O2/H2 around 5 mins in.

Sadly I don't think this will include altitude effects but will supply more detailed data to upgrade the CFD for the ground test SABRE.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/16/2015 12:33 AM
Excellent news. Good to hear that things are hotting up at REL  :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Kharkov on 06/16/2015 06:15 AM
I seem to recall it being said that the addition of Expansion/Deflection nozzles to SABRE engines means that the required distance to reach takeoff speed, and so the maximum length of the runway allowing abort capability will be reduced to less than the max length of 5,500mtrs, which to my mind has always been a problem. Not a project-stopping problem but a significant PITA.
Would anyone care to speculate, if we take it as read that Expansion/Deflection nozzles are used, what the standard takeoff/max runway length would be?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/16/2015 10:49 AM
I seem to recall it being said that the addition of Expansion/Deflection nozzles to SABRE engines means that the required distance to reach takeoff speed, and so the maximum length of the runway allowing abort capability will be reduced to less than the max length of 5,500mtrs, which to my mind has always been a problem. Not a project-stopping problem but a significant PITA.
Would anyone care to speculate, if we take it as read that Expansion/Deflection nozzles are used, what the standard takeoff/max runway length would be?
Hempsell mentioned this on a Space Show, but I can't recall which episode.

IIRC this could cut the take off run by 400-500m. As this at full GTOW that would be the part of the runway that has to be extra reinforced.

REL have talked of the runway as a $Bn investment so cutting 1/9 of the heaviest section should be good for saving $90-100m for a new build.

I'll remind people that is only for a full orbit capable runway. A Skylon could be based in its home country at much shorter (lower loading) runways at it'll be 150 tonnes lighter when in air breathing out to Kourou, before LH2 refuel and LO2 on load.
Title: Re: News
Post by: john smith 19 on 06/18/2015 05:34 PM
The SABRE engine requires a novel design of the rocket engine’s thrust chamber and nozzle to allow operation in both air-breathing and rocket modes, as well as a smooth transition between the two. The Advanced Nozzle project is demonstrating the feasibility of this concept and represents a significant technology development effort towards the SABRE demonstrator engine.
Most interesting.

Will the test engine have a name?

"SABRE demonstrator engine" seems a bit unwieldy, or is it so close to a flight model SABRE it's more like SABRE v0.9?
Title: Re: News
Post by: t43562 on 06/19/2015 05:02 AM
Will the test engine have a name?

"SABRE demonstrator engine" seems a bit unwieldy, or is it so close to a flight model SABRE it's more like SABRE v0.9?

"sabre" I imagine.

or "sABRE" :-)  or . . . . . . dare I say it . . . . .. "Light ...er ... SABRE?"
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/19/2015 02:58 PM
It's not a full SABRE, so perhaps it might be referred to as a SABRE lite;
.........or even as t43562 suggests, a lite SABRE.   ::)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/19/2015 08:39 PM
Here's an article on REL by Parabolic Arc

http://www.parabolicarc.com/2015/06/19/reaction-engines-begins-rocket-tests/#more-55597
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/23/2015 05:59 PM
I have been reading over on the pprune forum (military aviation) several posts in praise of the use of a ski jump to launch the Harrier and the upcoming F35-B.   "It's like having a free 1.5km runway in the sky".

A question was asked about why they are not used on land as well - and here is a video of that happening:

https://vimeo.com/lmaeronautics/review/131439135/07c088ad82

The answer was generally that they weren't so critically important when there was enough runway space as you do find on land.  They are also inconvenient if you want to use the runway to land in the opposite direction (if I understand correctly).

I was just thinking about whether Skylon could make use of a ramp?

I couldn't immediately see if this had been discussed before - perhaps long ago or with different words than I searched for.  Sorry if I missed it.

Presumably the gradient would have to be much lower for such a long vehicle and perhaps the landing gear might not survive it. 
I am sure there must be other objections but I thought it might make the very expensive runway a bit shorter.

I suppose to be fair it wouldn't remove the need for a long of free space after the end of the runway for a Skylon to pass over as it builds up to flying speed but you would not, perhaps, have to build anything on it.

I suppose there is also the thought that Skylon doesn't have any kind of thrust vectoring and I'm not sure how much that affects the usefulness of a ramp.  Wikipedia tells me that the Su-33 doesn't appear to use vectoring but I have seen the ramps on Russian carriers.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/23/2015 06:29 PM
I suppose there is also the thought that Skylon doesn't have any kind of thrust vectoring and I'm not sure how much that affects the usefulness of a ramp. 
I thin k you'll find that SABRE does do thrust vectoring, but on the whole engine, rather than something smaller.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 06/23/2015 08:57 PM
I thought it was just the chambers/bells that were supposed to gimbal.  And not by much; this isn't a Harrier here...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Kharkov on 06/24/2015 05:07 AM
@t43562

I think you'll find that Skylon's takeoff speed is around Mach 0.5. I'm not an engineer but I really wouldn't want to hit even a very modest ski jump at anything like that speed...

Having said that however, would it help matters - shorten the takeoff run a bit & get Skylon into the air quicker - if at around Mach 0.45, the forward undercarriage extended its length by another metre or so, raising the nose and increasing the angle of attack on the wings?

I suspect you'd need to gimbal the thrust somewhat to avoid melting bits of the runway...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/24/2015 09:42 AM
I thought it was just the chambers/bells that were supposed to gimbal.  And not by much; this isn't a Harrier here...
It's a tricky point. Early US engines (and I think the Russians?) pivoted their thrust chambers only, but the US started pivoting their whole engines from quite early on, presumably feeling pivoting about the fairly low pressure feed lines from the tanks were going to be a lot easier than moving the TC, need flexible couplings capable of staying leak proof at 10s (100's for the SSME) of atms.

You're right about the gimbal angles, IIRC even the Shuttle only did +/- 7.5 deg on any axis, which is well within the range of a flexure bearing (which can be made very strong)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/24/2015 10:49 AM
@t43562

I think you'll find that Skylon's takeoff speed is around Mach 0.5. I'm not an engineer but I really wouldn't want to hit even a very modest ski jump at anything like that speed...

I'm also a layman but from what I read, the aircraft leaves the ramp at less than flying speed - otherwise the ramp wouldn't actually be serving any purpose.  It's the fact that it has space and time (thanks to the vector given to it by the ramp) to accelerate in the air and reach flying speed without it's wheels having to be on tar that gives you the advantage of a shorter runway.

M 0.5 is about 600kmh and googling leads me to believe that the Harrier stalls at roughly 270kmh.  I suppose the harrier number is rather a rough guess and would be very variable depending on takeoff weight anyhow.  Nevertheless it's indicative of the relative difference - maybe Skylon need to travel about 2X faster.

Perhaps any ramp would have to be correspondingly 2X more gentle and would then need to be very very long and very very strong and would end up being more expensive than the extra runway.  It's gradient would also be limited by how much Skylon could tip before the tail touched the ground and as you said the effect of the engines on the runway.
 

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 06/24/2015 06:10 PM
The real killer for this idea is that a large proportion of the runway is for abort contingency, where Skylon cuts off the engines and slams on the (water cooled) brakes.

Bang (crash, bang, wallop) goes the intact abort option when you fall off the end of the ramp while braking...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/24/2015 06:59 PM
Given Reaction Engine's approach of having as few unconventional technologies as possible, I suspect launch ramps are something that may not be considered for the first wave.
Welcome to the site.

Yes, I've never heard of a land runway with ski jump. It's a clever idea but aircraft carriers have (essentially) a cliff the aircraft falls off if takeoff fails. That's not the case for normal airports.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/24/2015 09:01 PM
The real killer for this idea is that a large proportion of the runway is for abort contingency, where Skylon cuts off the engines and slams on the (water cooled) brakes.

Bang (crash, bang, wallop) goes the intact abort option when you fall off the end of the ramp while braking...

One of the great things about the internet is the way that you get to talk to all sorts of people you'd never otherwise meet.  I asked John Farley, one of the most famous Harrier test pilots, about it on pprune and his objection was that the T/W had to be over 0.85 roughly.   My very dodgy guess at Skylon's T/w is 0.26.

As for abort.....obviously that does present a serious problem but I suppose it might be worth trying to think about that some other way if a ramp was actually worthwhile in the first place.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 06/24/2015 11:23 PM
Possible arrangement of a ramped runway is an otherwise long and flat conventional runway with an overrun extension leading up an embankment to an elavated (relative to main runway elevation) runout extended overrun area exclusively for Skylon. If the embankment change in elevation is roughly equivalent to traditional 100ft obstacle clearance spec and is a appropriate upward curve for the expected speed, normal airplanes will have no issue (though pilots will get creeped out by the ground following them up). The annoyance is the overrun area is where approach lighting equipment is normally located (and the inner marker beacon?) so how one would set that up flush in the overrun is a bit of a problem. That achieves the hump with no cliff dropoff, and no downhill component for a inserted hump in a runway complicating emergency braking.

In retrospect, I suppose the humped aspect could be better achieved with a single contiguous runway with the hump near Skylon Vto, so the overall runway looks like a flattened S shape. This avoids the overrun design issues. Many existing runways have non-flat profiles due to local topography (and cost cutting avoiding the earthworks to build a flat runway), though I think of those, most tend to have a V profile? Though that depends on local terrain being helpful to keep costs down.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 06/25/2015 09:29 PM
My very dodgy guess at Skylon's T/w is 0.26.

C1 was around 0.45-0.47 during the takeoff roll, and peaked (for the airbreathing segment) at roughly 0.8 just past Mach 2.  The D revision has some substantial differences from the C designs, including larger wings and a more efficient engine cycle, so there might be some modest changes in those numbers.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 06/26/2015 07:59 PM
I've been thinking about the differences between the SABRE 3 and SABRE 4 cycles since the patents became available to read.
I think it's interesting that where as the former was designed as an integrated engine which was an excellent rocket and an adequate air breather the later seems to be a much less integrated engine designed to be an excellent rocket and and a good air breather and that this disintegration of the engine modes has resulted in a much more flexible design.

Historically all attempts at combined cycle engines seem to be about finding the right balance between performance and integration of different engine cycles and it seems REL have moved in the direction of more performance and less integration.

An interesting result of this is that where as previously the SABRE engine could be said to be not much good for anything other than SSTO that's no longer strictly true for the SABRE 4 cycle. Its equivalence ratio of 1.2 is not far off Scimitar's EQ of  0.7959 and the patent allows for a variant to run at the same EQ by adding another recuperation stage and lower pressure combustion chambers, further the only thing that is shared with the rocket mode is the nozzle so it would seem possible to easily remove all the pure rocket components to make a pure air breathing SABRE variant with reasonable fuel consumption only without the high life cycle and subsonic efficiency of Scimitar.

This begs the question, given the USAF interest in SABRE, have REL  decided in order increase their addressable market  to develop a duel purpose engine design that both satisfies their design needs for SSTO but also allows for an easily achievable variant that satisfies USAF desire for hypersonic flight and when they talk about SABRE, is this the SABRE they're talking about?   
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: SICA Design on 06/26/2015 10:29 PM
... disintegration of the engine ...
Is that a phrase REL have used in their patent? Hope no-one takes it out of context! (like I just did...  :) )
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/27/2015 07:39 AM
This begs the question, given the USAF interest in SABRE, have REL  decided in order increase their addressable market  to develop a duel purpose engine design that both satisfies their design needs for SSTO but also allows for an easily achievable variant that satisfies USAF desire for hypersonic flight and when they talk about SABRE, is this the SABRE they're talking about?
No. REL were clear the cycle they described to the USAFRL was the same one given to the Von Karman Institute  so the USAF could compare their results with a 3rd party. That's the SABRE 3.

SABRE IV's stated improvement is reduction in LH2 during airbreathing. REL were also clear if you want an air breathing engine their LAPCAT work is the way to go. USAFRL do not appear to have been interested in this work.

The idea that somehow hypersonic cruise is like arrested launch seems to come from the SCRamjet community.

The only part of an (RLV) launch that hypersonic cruise resembles is the re-entry.

The technical term for a rocket LV that is not accelerating during engine burn is crashing  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 06/27/2015 09:25 AM
... disintegration of the engine ...
Is that a phrase REL have used in their patent? Hope no-one takes it out of context! (like I just did...  :) )
No, perhaps not the best word, but engine no longer shares a fuel delivery system,  rocket chambers or preburner betweeen modes.

This begs the question, given the USAF interest in SABRE, have REL  decided in order increase their addressable market  to develop a duel purpose engine design that both satisfies their design needs for SSTO but also allows for an easily achievable variant that satisfies USAF desire for hypersonic flight and when they talk about SABRE, is this the SABRE they're talking about?
No. REL were clear the cycle they described to the USAFRL was the same one given to the Von Karman Institute  so the USAF could compare their results with a 3rd party. That's the SABRE 3.
But the collaboration is ongoing, and ongoing REL is working on SABRE 4 so the USAF is interested in SABRE 4 and part of that is :
 
Quote
  the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system
Now couldn't that be describing a SABRE 4 derived engine such as I suggested might be possible based on the patents.

SABRE IV's stated improvement is reduction in LH2 during airbreathing. REL were also clear if you want an air breathing engine their LAPCAT work is the way to go. USAFRL do not appear to have been interested in this work.

The idea that somehow hypersonic cruise is like arrested launch seems to come from the SCRamjet community.

The only part of an (RLV) launch that hypersonic cruise resembles is the re-entry.

The technical term for a rocket LV that is not accelerating during engine burn is crashing  :(

The difference between Scimitar and SABRE is that the former has a fan added for high efficiency subsonic cruise  performance and :

Quote
The main difference between the Scimitar engine and the well investigated SABRE spaceplane engine is the design lifetime, 15,000hours compared to 50 hours. Apart from this, the Scimitar requirement is alleviated by reduced mass sensitivity relative to SABRE.

As has been discussed previously for a military engine for a highly specialized vehicle short lifetimes are more acceptable and the need for subsonic cruise on a hypersonic bomber is perhaps debatable. Other than that are you arguing Scimitar itself is a bad idea?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/27/2015 12:17 PM
@lkm
AFAIK REL had the SABRE 4 concept in mind long before the USAF collaboration. Like JS19 says, I think the USAF had access to the SABRE 3 cycle and not the SABRE 4 cycle, but I could be wrong about that.

BTW, I think de-integration might be a better descriptor  :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/27/2015 03:38 PM
These chaps sound like the sort of people who would need a Skylon if it was available:


Quote
OneWeb satellite operator eyes huge rocket campaign
http://www.bbc.com/news/science-environment-33268180
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/27/2015 03:51 PM
@t43562
The OneWeb consellation of satellites is planned to be operational by 2020, far too early for Skylon. That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.

However, this is a good example of how a successful skylon programme doesn't negate the need for other types of operators. The saying 'horses for courses' will still be true in 2025.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/27/2015 04:28 PM
@t43562
... That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.

I presume they have been designed to fit the launchers available to them.  Perhaps they would not look the same if Skylon was on the scene.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/27/2015 10:31 PM
Yes, no doubt designed partially with existing launch capability in mind (and partially with the need to fulfil job specifications).

But agreed of course, increased launch capability as provided by skylon (if successful) will open up a whole new ball-game in space access and will change how people view space in terms of reliability of launch, flexibility of launch, vastly reduced lead-in times (on the order of days if needed) and perhaps other stuff that we haven't considered yet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/28/2015 11:03 AM
@t43562
The OneWeb consellation of satellites is planned to be operational by 2020, far too early for Skylon. That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.
The trip to GEO is planned to use the Skylon Upper Stage. That's designed to carry about a 6500Kg payload to GTO.

1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.

But now the timetable does not look feasible for Skylon to be used.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 06/28/2015 01:31 PM
Do senior representatives of REL, Airbus and Rolls Royce meet every other Sunday for a beef dinner and a pint?  I'd like to think so.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 06/28/2015 01:35 PM
JS19
**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 06/28/2015 08:06 PM
JS19
**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.

Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-).  Imagine that you had a SUS-like booster which carried multiple satellites.   Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job?   I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move.   If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit.  It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km.   Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon  launch.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/29/2015 12:05 AM
Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-).  Imagine that you had a SUS-like booster which carried multiple satellites.   Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job?   I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move.   If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit.  It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km.   Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon  launch.
You might like to look at the 1st generation Orbcomm satellites.

Most were deployed by single Pegasus XL launches to populate a ring of 8 satellites, each being designed like a pizza so they could be stacked together.

While the bus could supply some separation IIRC most was done by the satellites small thrusters or simple gravitational drift.

Orbcomm was one of 3 early 90's constellations (Globalstar and Iridium being the others) that actually got built. IIRC it offered the least bandwidth but was the only one that made (or came close to making) a profit. Something this new generation of constellation promoters (and their investors) might like to keep in mind.

Incidentally 1200Km is inside the Van Allan radiation belt and above the GPS constellation.

The first reduces air drag (which is actually the largest residual force on satellites below 1000Km) but raises the radiation exposure levels, so either the electronics cook faster or you have to spend mass on shielding, making them less capable, or you replace more frequently. How much more frequently would be a key design decision to trade replacement versus making them tough enough to survive as long as less exposed satellites.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 06/29/2015 12:38 AM
JS19
**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.

Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-).  Imagine that you had a SUS-like booster which carried multiple satellites.   Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job?   I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move.   If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit.  It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km.   Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon  launch.

Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/29/2015 12:14 PM
Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.
Except the bus in this case would be the SUS, which is currently spec'd at having a 10 use life time and would be recovered by the Skylon for return to Earth and refueling.

A completely reusable system changes deployment options quite a lot, especially given the target payload (125Kg?) for a single unit is much smaller than the target for a much bigger single payload to a much higher orbit.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Asteroza on 06/30/2015 12:11 AM
Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.
Except the bus in this case would be the SUS, which is currently spec'd at having a 10 use life time and would be recovered by the Skylon for return to Earth and refueling.

A completely reusable system changes deployment options quite a lot, especially given the target payload (125Kg?) for a single unit is much smaller than the target for a much bigger single payload to a much higher orbit.

Which implies cluster deployers (AKA corncob upper stages) will not be based on the currently envisioned cryogenic fueled SUS, but more like a SUS-like electric tug. So cSUS and eSUS variants?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 06/30/2015 09:46 AM
Which implies cluster deployers (AKA corncob upper stages) will not be based on the currently envisioned cryogenic fueled SUS, but more like a SUS-like electric tug. So cSUS and eSUS variants?
I don't think so. The dispenser is part of the payload. It's designed to fit on the front of the upper stage.

In Skylon's case the US sits in the payload but it's still the upper stage.

I don't see anyone who they are booked with announcing an ion drive upper stage. That's more of a "space tug" concept.

I would expect they will deploy like most of these constellation concepts. Upper stage burns AFAP, gravity drift if needed and satellite thrusters if absolutely necessary.

BTW IIRC the latest Skylon User Manual has a description of deploying an ion drive comm sat. In it the SUS deploys it about 5000 Km (above the radiation belt) and avoids the "radiation crockpot" effect.

No I don't think a specific ion drive US will be necessary.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/06/2015 03:46 PM
Today is out the new UK Space Humanflight strategy.

There is an indirect, but very very clear reference to Skylon. It appears it will have a dedicated section in the 2015 Space Technology Strategy (yet to be published I believe):

"Likewise, the development of  spaceplane technology in the UK would  complement these activities, and this will  be considered by the Agency in its national  space technology strategy." (p.10)

here the link

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/442462/Space_Environments_and_Human_Spaceflight_Strategyv2.pdf

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Soundbite on 07/10/2015 10:46 AM
An article in Aviation Week Titled "Reaction Engines Reveals Secret Of Sabre Frost Control Technology" stated that Richard Varvill spoke at the American Institute of Aeronautics and Astronautics International Space Planes and Hypersonics conference and explained how the frost control system works.

Mark Thomas also explained why they finally patented the frost control mechanism.  He said  “The trigger for patenting was the awareness that to execute this program we are going to have to involve other companies. You can’t keep trade secrets very long in that situation, so it is better to be protected formally and legally on the clever stuff.”

At the end of the article it states that:

The company is developing  the Sabre engine principally for the Skylon single-stage-to-orbit spaceplane. But the propulsion system and its pre-cooler technology are attracting wider interest for potential aircraft and two-stage launch vehicle applications

You can read the article here https://awin.aviationweek.com/ArticlesStory.aspx?id=4ae664e7-3da0-4832-9827-03895f066bb3
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/10/2015 03:51 PM
**The trigger for patenting was the awareness that to execute this program we are going to have to involve other companies. You can’t keep trade secrets very long in that situation, so it is better to be protected formally and legally on the clever stuff**

That was going to be the only reasonable outcome. Other companies they're hoping to work with obviously didn't want the risk of doing business with REL unless there was legal protection on the core technology. Now the question is which companies are REL in negotiation with?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/10/2015 04:41 PM
well, not sure of names, but it must have these characteristics

- being a big player with a history in airframes
- being interested in space launch business
- being credible when developing new projects
- being stack with cash, or eventually being so well known to being able to raise cash at favourable interest rates.

I would bet on RR, Boeing or LM, but who knows?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/10/2015 07:14 PM
well, not sure of names, but it must have these characteristics
I would bet on RR, Boeing or LM, but who knows?
Originally REL were only talking about the pre cooler but their skills seem to be growing and their confidence at executing the whole design.

This would not be competition to RR, since they don't make hybrid air breathing rocket engines.

LM are solely government contractors. For Europe the formation of a division of Astrium would be the logical way to go.

The issue for REL remains some way of signing up future customers to purchase a vehicle from another company that has not been formed yet which can be passed to that company.

That definitely sounds like a problem in economics or international law.

[EDIT Read the Av Week article. So it does use Methanol in a counter flow arrangement, starting at th back with (presumably) near pure Methanol and using the dynamic pressure to force it forward to lower and lower pressure stages.

Obviously a tricky process to get right but one that seems to have proved very effective.
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/10/2015 08:10 PM
well, not sure of names, but it must have these characteristics
I would bet on RR, Boeing or LM, but who knows?
Originally REL were only talking about the pre cooler but their skills seem to be growing and their confidence at executing the whole design.

This would not be competition to RR, since they don't make hybrid air breathing rocket engines.

LM are solely government contractors. For Europe the formation of a division of Astrium would be the logical way to go.

The issue for REL remains some way of signing up future customers to purchase a vehicle from another company that has not been formed yet which can be passed to that company.

That definitely sounds like a problem in economics or international law.

[EDIT Read the Av Week article. So it does use Methanol in a counter flow arrangement, starting at th back with (presumably) near pure Methanol and using the dynamic pressure to force it forward to lower and lower pressure stages.

Obviously a tricky process to get right but one that seems to have proved very effective.

LM are the ones who would be most interested for their aviation projects as they tick a lot of the right boxes. I don't see why LM's focus on government contracts is an issue for you?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: AnalogMan on 07/10/2015 11:04 PM
Apart from a batch of UK patents published on 15 April 2015 (ten of them) there have also been 3 more published within the last 4 weeks.  All 13 patents were originally lodged on 11 Oct 2013.  I didn't see these new ones mentioned yet.

17 June 2015
Patent GB2521113 (https://www.ipo.gov.uk/p-ipsum/Case/PublicationNumber/GB2521113)
Applicant: Reaction Engines Limited (Incorporated in the United Kingdom)
Title: Heat exchanger
Date Lodged: 11 October 2013
Inventors: Bond, Alan and Varvill, Richard

17 June 2015
Patent GB2521114 (https://www.ipo.gov.uk/p-ipsum/Case/PublicationNumber/GB2521114)
Applicant: Reaction Engines Limited (Incorporated in the United Kingdom)
Title: Heat exchanger
Date Lodged: 11 October 2013
Inventors: Bond, Alan and Varvill, Richard

01 July 2015
Patent GB2521588 (https://www.ipo.gov.uk/p-ipsum/Case/PublicationNumber/GB2521588)
Applicant: Reaction Engines Limited (Incorporated in the United Kingdom)
Title: Turbomachine with radially compressed blades
Date Lodged: 11 October 2013
Inventor: Varvill, Richard

Copies attached.  List of published UK patents since 2010 can be found at this link (https://www.ipo.gov.uk/p-pj/p-pj-ukapppub.htm?startYear=2010&startMonth=July&startDay=28th+-+6323&endYear=2015&endMonth=July&endDay=8th+-+6581&filter=%22reaction+engines%22&perPage=100&sort=Publication+Date).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/10/2015 11:15 PM
Well, plenty of technical specifications there. As the Dutch say - the monkey's out of the sleeve now. :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/11/2015 04:46 PM
LM are the ones who would be most interested for their aviation projects as they tick a lot of the right boxes. I don't see why LM's focus on government contracts is an issue for you?
AFAIK LM make no commercial products. All they do is a)Government contract work b)National security systems c) Weapon systems.

This means they are good at a)Filling in procurement paperwork and b)Lobbying governments and their support staffs to get funded and c)Lobbying governments and their support staffs to get extended funding.

All of those are skills, they're just not actually very useful when it comes to making stuff.

IOW Their idea of "profit" is nothing to do with a commercial entities. The nearest LM come to space launch is they supplied the Delta IV half of the ULA product portfolio.

AFAIK the Delta IV has never launched a non USG satellite (IE not NASA, DoD or some other "Administration"). Where private companies have gone with a ULA vehicle it's the Atlas, or the go with some other supplier.

That is a very bad choice if you want to engage with world wide customers and have tight cost and schedule, which REL need to do.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 07/11/2015 05:18 PM
For completeness sake we should mention Lockheed made the L-1011 TriStar passenger jet - operated by British Airways, and with engines developed for it by Rolls Royce. But that was a long time ago, and not a roaring success...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/11/2015 05:53 PM

LM are the ones who would be most interested for their aviation projects as they tick a lot of the right boxes. I don't see why LM's focus on government contracts is an issue for you?
AFAIK LM make no commercial products. All they do is a)Government contract work b)National security systems c) Weapon systems.

This means they are good at a)Filling in procurement paperwork and b)Lobbying governments and their support staffs to get funded and c)Lobbying governments and their support staffs to get extended funding.

All of those are skills, they're just not actually very useful when it comes to making stuff.

IOW Their idea of "profit" is nothing to do with a commercial entities. The nearest LM come to space launch is they supplied the Delta IV half of the ULA product portfolio.

AFAIK the Delta IV has never launched a non USG satellite (IE not NASA, DoD or some other "Administration"). Where private companies have gone with a ULA vehicle it's the Atlas, or the go with some other supplier.

That is a very bad choice if you want to engage with world wide customers and have tight cost and schedule, which REL need to do.

Well if you're the U.S. & want REL's technology for military use then I would think that's precisely what makes LM a strong choice.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/11/2015 05:54 PM
ok, so we can exclude LM from the picture. Who else should be dropped?
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/11/2015 06:25 PM
ok, so we can exclude LM from the picture. Who else should be dropped?

Why are you assuming this technology is only for commercial/civilian purposes because if you are then you're being very, very naive.

I'd put reasonable money on this seeing use in the military long before it has commercial use.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 07/11/2015 06:46 PM
We're in danger of talking past each other here. There are at least two points being argued for, which are fairly distinct:

1] If REL is looking for an airframer to build Skylons, Lockheed Martin is not an obviously good choice.
2] If REL is looking to license some of its recently patented technologies (multiple), then Lockheed Martin is a likely customer as they deal in products that could potentially benefit from them, e.g. military jet/UAV/cruise missiles, etc.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Jim on 07/11/2015 10:58 PM

1.  AFAIK LM make no commercial products. All they do is a)Government contract work b)National security systems c) Weapon systems.

2.  This means they are good at a)Filling in procurement paperwork and b)Lobbying governments and their support staffs to get funded and c)Lobbying governments and their support staffs to get extended funding.

3.  IOW Their idea of "profit" is nothing to do with a commercial entities. The nearest LM come to space launch is they supplied the Delta IV half of the ULA product portfolio.

4.  AFAIK the Delta IV has never launched a non USG satellite (IE not NASA, DoD or some other "Administration"). Where private companies have gone with a ULA vehicle it's the Atlas, or the go with some other supplier.


Wrong on all points

1.  They do commercial comsats.   The A2100 satellite bus has been used for many comsats.  The LM500 spacecraft bus was used for the initial Iridium constellation.

2.  Completely unsubstantiated and nonsense

3. LM supplied the Altas V which has commercial contracts and had many for Atlas II.

4.  Delta IV launched Eutelsat W5.  The GOES launches on Delta IV were completely commercial.  They were converted Delta III launches from a Hughes block buy.  The gov't had no role in the procurement.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 07/12/2015 07:28 AM

1.  AFAIK LM make no commercial products. All they do is a)Government contract work b)National security systems c) Weapon systems.

2.  This means they are good at a)Filling in procurement paperwork and b)Lobbying governments and their support staffs to get funded and c)Lobbying governments and their support staffs to get extended funding.

3.  IOW Their idea of "profit" is nothing to do with a commercial entities. The nearest LM come to space launch is they supplied the Delta IV half of the ULA product portfolio.

4.  AFAIK the Delta IV has never launched a non USG satellite (IE not NASA, DoD or some other "Administration"). Where private companies have gone with a ULA vehicle it's the Atlas, or the go with some other supplier.


Wrong on all points

1.  They do commercial comsats.   The A2100 satellite bus has been used for many comsats.  The LM500 spacecraft bus was used for the initial Iridium constellation.

2.  Completely unsubstantiated and nonsense

3. LM supplied the Altas V which has commercial contracts and had many for Atlas II.

4.  Delta IV launched Eutelsat W5.  The GOES launches on Delta IV were completely commercial.  They were converted Delta III launches from a Hughes block buy.  The gov't had no role in the procurement.

I read that the Altas V was developed for a US Airforce program.    Are they the type of company to start a risky new venture that doesn't have a big guaranteed customer such as the government?  e.g. there are people who say that about BAE.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/12/2015 10:56 AM
ok, so we can exclude LM from the picture. Who else should be dropped?

Why are you assuming this technology is only for commercial/civilian purposes because if you are then you're being very, very naive.

I'd put reasonable money on this seeing use in the military long before it has commercial use.

I am not assuming that it is only for civilian purposes. However, I believe it will originally be for civilian purposes. But I might be wrong.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RotoSequence on 07/12/2015 11:01 AM
I am not assuming that it is only for civilian purposes. However, I believe it will originally be for civilian purposes. But I might be wrong.

The US Air Force is one of the first companies to bankroll the technology. Unless I'm mistaken, it could be an enabling technology for hypersonic, air breathing aircraft with conventional turbine engines. If that's true, the first applications will almost certainly be military in nature.
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/12/2015 11:10 AM
I am not assuming that it is only for civilian purposes. However, I believe it will originally be for civilian purposes. But I might be wrong.

The US Air Force is one of the first companies to bankroll the technology. Unless I'm mistaken, it could be an enabling technology for hypersonic, air breathing aircraft with conventional turbine engines. If that's true, the first applications will almost certainly be military in nature.

Yes I think we need to separate one thing from another. Technology licensed to the airforce & Skylon's build by commercial private industry.

I apologise in retrospect my OP was rather too hot headed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/12/2015 11:16 AM
why don't we open a poll on who will be the airframer?  :) it could be fun to see who's the most guessed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 07/13/2015 10:57 AM
EADS would be at the top of the list, I would have thought. Probably the only non-US* aerospace company capable of executing a development program of that size.



* ITAR
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/13/2015 05:36 PM
Nice posts JCRM. Welcome to the thread.

If anyone is interested the wingspan of the Skylon D1 is 26.818m - for comparison, a bit less than an original 737 at 28.35m (both sources Wikipedia).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/14/2015 06:46 AM
For completeness sake we should mention Lockheed made the L-1011 TriStar passenger jet - operated by British Airways, and with engines developed for it by Rolls Royce. But that was a long time ago, and not a roaring success...
A long time ago.  :(

They (like BAe) pretty much divested themselves of any stuff that doesn't have some part of a government (preferably the US, but as long as they have plenty of cash) a long time ago.

Do  you want that as the core contractor for a time critical project to replace a significant part of their business?

If you wonder what LM would be like on this I have a simple example.

The X33 programme.

Swallowed every cent of both the development and test budgets and still failed to build a vehicle.

On that basis BAe would be a better fit.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: QuantumG on 07/14/2015 07:39 AM
https://twitter.com/patriciavmayes/status/620858977602154496
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/14/2015 08:22 AM
I'm not sure any existing manufacturer is a particularly good fit - the proposed skin and frame construction seems quite unlike modern aeroplanes.
Welcome to the forum.
TBH you're right, it's more the process of mfg and getting type approval for a large aeronautical project that they need. I think some of the "regional jet" mfg's might have a shot but AFAIK there are so few of them left  :(
Quote
Airliner wings are quite unlike what will be needed for this mach 5 'plane, and I would guess the scale of the wings also leaves fighter jet builders with little relevant experience.
Also true. Most large aircraft use the wings as fuel tanks, absolutely out of the question for LH2.
Quote
While Airbus Group might seem to be the "obvious" choice, they're pretty invested in Arianne, so the politics could be interesting.
Well Airbus has a division working on A6, it's a question of how much autonomy a "Skylon Division" would have and how much the parent could influence it. I'll note some REL staff have experience of both Anglo French and pan European projects from Concorde through (IIRC) Tornado and Typhoon.
Quote
But this seems to be very much cart before the horse. While an awful lot of design work has gone into a craft to fly the SABRE, that work was needed to ensure SABRE was worth developing. Now a working engine is needed before it would be sensible to begin work on the craft.
True. 2016/17 should be very exciting.
We're in danger of talking past each other here. There are at least two points being argued for, which are fairly distinct:

1] If REL is looking for an airframer to build Skylons, Lockheed Martin is not an obviously good choice.
Agreed.
Quote
2] If REL is looking to license some of its recently patented technologies (multiple), then Lockheed Martin is a likely customer as they deal in products that could potentially benefit from them, e.g. military jet/UAV/cruise missiles, etc.
Reasonable.
ok, so we can exclude LM from the picture. Who else should be dropped?

Why are you assuming this technology is only for commercial/civilian purposes because if you are then you're being very, very naive.

I'd put reasonable money on this seeing use in the military long before it has commercial use.
Good luck with that.

Light weight high efficiency heat exchangers have a number of civilian and military applications but none of them get REL closer to their goal of building an RLV.

SABRE's sole function is as a launch system. The notion that hypersonic cruise can become launch  is one actively promoted by the US SCRamjet community, who've probably had $5-10Bn (inflation adjusted) from the late 1950's to demonstrate their plan and took till 2004 to get positive thrust in a flight vehicle (X-43A).

If you want a hypersonic cruise engine you design a hypersonic cruise engine, you don't under run a launch engine.

REL and the USAFRL understand this quite well.

There is also the little problem that M5+ cruise is like continuous re-entry. Skylon's trajectory gains and sheds heat in a way that is impossible for a cruise vehicle to do at anything like constant altitude.

The engine is just the start.  :(

Well if you're the U.S. & want REL's technology for military use then I would think that's precisely what makes LM a strong choice.
There is the small matter of what REL want.

It is after all their technology.  :(

I read that the Altas V was developed for a US Airforce program.
It was.

Both the Atlas V and Delta IV were developed at USAF request under the EELV programme. Both companies committed their own funds (or staff and facilities equivalent to substantial funds) to their efforts and (in theory) one of them would become sole provider to the USG for most USG launches. The other would then have to rely on commercial launches.

IRL the down select never happened, the launch market suffered one of its periodic droughts and they merged into ULA, where they've enjoyed a monopoly of large USG launches ever since.
Quote
   Are they the type of company to start a risky new venture that doesn't have a big guaranteed customer such as the government?  e.g. there are people who say that about BAE.
Indeed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/14/2015 08:26 AM
https://twitter.com/patriciavmayes/status/620858977602154496
Now that injection plate is intriguing.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/14/2015 09:49 AM

https://twitter.com/patriciavmayes/status/620858977602154496
Now that injection plate is intriguing.

Why is that?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/14/2015 01:52 PM
update from REL website.

looks like production is ramping up

http://www.reactionengines.co.uk/news_14july2015_vacfurnace.html

(edit)

morever, if it works and pre-coolers are in fact requested by the market, they could easily build a second furnace to sell the precoolers to other customers and so finance part of the engine development
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 07/14/2015 02:54 PM
Point taken  - I'm working on some major fixes for the website. It'll be a while yet, but watch this space! (excuse the pun...)

Three cheers for JN for giving us a story we can link to easily (about the furnace).   Yay and thank you. 8) ;D
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Alpha_Centauri on 07/14/2015 07:44 PM
Curious comment from the UK space conference;

https://twitter.com/pbdes/status/621009703066279936?s=17

Anyone know what this is about? The only proposal I know of on that scale is REL's Blue Boomerang...

http://sec.kingston.ac.uk/uklaunch/docs/Reaction%20Engines%20Blue%20Boomerang%20-%20Light%20Launcher.pdf
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: A_M_Swallow on 07/14/2015 11:05 PM
When doing commercial feasibility studies cubesats currently cost $50,000 - $100,000 per kilogram to launch. This decreasing price includes share of the launch vehicle, deployment hardware, safely inspection and possibly the kick stage. A primary cubesat launching mission can aim for polar orbits or carry medium sized satellites containing propellant.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 07/14/2015 11:15 PM
update from REL website.

looks like production is ramping up

http://www.reactionengines.co.uk/news_14july2015_vacfurnace.html

(edit)

morever, if it works and pre-coolers are in fact requested by the market, they could easily build a second furnace to sell the precoolers to other customers and so finance part of the engine development
Look like RE learnt something publicity.

This is actually what going to make it hard for other people to copy Reaction Engine technology even with the patents in the public, the technology to actually manufacture the pre coolers, some of it was developed perfected by Reaction Engines themselves and I very much doubt we will see those being patented anytime soon.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: knowles2 on 07/14/2015 11:21 PM
Curious comment from the UK space conference;

https://twitter.com/pbdes/status/621009703066279936?s=17

Anyone know what this is about? The only proposal I know of on that scale is REL's Blue Boomerang...

http://sec.kingston.ac.uk/uklaunch/docs/Reaction%20Engines%20Blue%20Boomerang%20-%20Light%20Launcher.pdf
There been a lot of talk about UK financing indigenous a single stage to orbit rockets for small rockets capable of launching from the UK. There was talk about Virgin Galactic doing something in the UK but from what I hear their efforts confined to America at the minute, through their main customer is a British satellite firm.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/15/2015 06:42 AM
This is actually what going to make it hard for other people to copy Reaction Engine technology even with the patents in the public, the technology to actually manufacture the pre coolers, some of it was developed perfected by Reaction Engines themselves and I very much doubt we will see those being patented anytime soon.
Correct.

The patents will tell you if you make an HX with tubes this size and in this layout it will have roughly this capability.

But once you run the numbers for your design you discover that such an HX takes millions of joints that have to be close to perfect first time (it's unlikely rework is possible)

That's to say better than a 1 in 1000 000 failure rate.

How you do that is what REL know. I'm sure they will build stuff using their technology for paying customers, but I'd suggest if they are wise they don't export the technology.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: momerathe on 07/15/2015 04:06 PM
I'm not sure any existing manufacturer is a particularly good fit - the proposed skin and frame construction seems quite unlike modern aeroplanes.

Airliner wings are quite unlike what will be needed for this mach 5 'plane, and I would guess the scale of the wings also leaves fighter jet builders with little relevant experience.

I take your point, but I'm mainly thinking about the depth their pockets. IIRC REL's development cost estimates for Skylon were comparable to the A380..
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Prober on 07/15/2015 04:07 PM
some 3D printer tech for Skylon

http://forum.nasaspaceflight.com/index.php?topic=33141.msg1404984#msg1404984

now I need to backtrack and read all your posts :-X
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/16/2015 01:12 AM
I agree they're an unlikely partner, however the SR-71 gives them some relevant experience - the skin, and supporting engines on low thickness wings.
That was about 55 years ago. The Ford Trimotor also used a corrugated skin design.

LM seems to be pursuing (or rather pursuing funding for) their "SR72" concept with an Aerojet provided Dual Mode Scramjet.

There are 2 problems with LM.
1) is they are American and Skylon needs to sell on an international basis to make profit and this will get very bogged down in US ITAR rules despite it being designed to look and operate as little like an ICBM as possible
2) They are Lockheed Martin. Looking over their 110+ page corporate accounts tells you their basic business model is "Sell stuff and services to the US Government." ULA is 10% of their profit and I doubt more than  20% of that is from someone that isn't a part of the USG or some other government. 

That might be useful when it comes to selling it to other governments but it does not suggest they are good at managing a commercially funded project on time and budget when their usual MO is call up the DoD/NRO/NASA for more money especially when there is an in house programme already in place through ULA.   :(

There is a reason that when NASA ran the NAFCOM cost model for the Commercial Cargo programme over SX they thought it would cost roughly 9x what SX spend on F1 and F9.

It's the cost over runs on US government aerospace projects going back decades gradually shifting the "centre of mass" of costs upward.  :(


Quote
If nothing else, a revenue stream would get them closer to their goal. I'm sure there is a large element of investor palatability, but Reaction Engines as a company was set up to sell heat exchangers. See also their wholly owned subsidiary "Skylon Enterprise Ltd"
True, a steady non research revenue stream of decent size would  help a lot in moving the project along.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/16/2015 07:58 PM
Quote from: http://www.reactionengines.co.uk/lapcat.html
The A2 airframe also has technology commonality with the SKYLON launch vehicle. [...] it is anticipated that the A2 airframe would be constructed as a similar multi-layer structure to SKYLON [...]
once a company was building *that* sort of aeroplane, slipping a Skylon into the mix would be a lot easier.
That's a bit of a chicken & egg problem

A2 is a very long way from being built.
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/20/2015 05:15 PM
This seems appropriate here.

Mach 5 Airliner Operations Face Huge Challenges

Quote
Will hypersonic airliners be too hot to handle . . . literally? The issues involved in ground handling of a Mach 5-plus transport still simmering after its intercontinental hypersonic hop are among the unique challenges being considered as researchers address the potential operation of future high-speed airliners. While most hypersonic transport projects have focused on the basic design and aerodynamic, propulsion, structures and systems technologies required, the operational aspects are ...

http://m.aviationweek.com/commercial-aviation/mach-5-airliner-operations-face-huge-challenges
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Glom on 07/20/2015 07:16 PM
Maybe an early deceleration to allow for cooling in the terminal phase?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: tl6973 on 07/21/2015 02:31 PM
Hello all,

Long-time lurker, first time poster.

I would imagine that it is probably easier to build Skylon before getting into anything like the A2, for a number of reasons:

1. Skylon is designed for a lifetime of 200 flights, spending only minutes each in hot "hypersonic cruise" (ie re-entry) conditions. this also goes for airframe loading cycles. This is compared to the requirement of at least thousands of hours (if not tens of thousands) and cycles for a civil airliner. therefore one would expect the sklyon airframe design to be a better first one to try.

2. There is a proven, existing market for Skylon - in fact, Skylon has been designed specifically based on the GEO comsat market. whereas, Lapcat is really a feasibility study, without the robust business case required to support investment/ development.

3. The amount of new cryogenic fuel supply infrastructure required for Skylon is far less than for something like an A2 - Skylon only needs it at enough launch sites to get to the right orbits, whereas a useful passenger plane will need supply at every place that people actually want to go.

As for the temperature of a just-landed A2, I imagine in normal aircraft operations you would have at least half an hour of subsonic flight before landing during which to cool down (getting in the runway queue for one thing), plus any active cooling if run at subsonic would bring the temperature down pretty fast, plus a low heat-capacity skin material, so i wonder if this might be a bit of a non-problem. Can anyone tell me if there were/ are heat handling issues with the Shuttle/ X37B post-landing?

I hope these are valid points and am very happy to be corrected on them, just pleased to be part of the discussion :)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/21/2015 09:01 PM
Hello all,

Long-time lurker, first time poster.
Welcome. 
Quote
I would imagine that it is probably easier to build Skylon before getting into anything like the A2, for a number of reasons:

1. Skylon is designed for a lifetime of 200 flights, spending only minutes each in hot "hypersonic cruise" (ie re-entry) conditions. this also goes for airframe loading cycles. This is compared to the requirement of at least thousands of hours (if not tens of thousands) and cycles for a civil airliner. therefore one would expect the sklyon airframe design to be a better first one to try.
This may be the difference between launch and cruise. The short length of time offers options that simply can't last the length of a long trip.
Quote
2. There is a proven, existing market for Skylon - in fact, Skylon has been designed specifically based on the GEO comsat market. whereas, Lapcat is really a feasibility study, without the robust business case required to support investment/ development.
That's a mistake on my part. Hempsell stated that REL looked at various uses for the vehicle in terms of velocity requirements. The delta V needed for comm sats turned out to be the sizing limit, but comm sat delivery is a key part of the economic case.

You're right about LAPCAT. In fact its the the engine. A2 was the aircraft design,but it was always more of an outline of the vehicle you'd need to carry it.
Quote
3. The amount of new cryogenic fuel supply infrastructure required for Skylon is far less than for something like an A2 - Skylon only needs it at enough launch sites to get to the right orbits, whereas a useful passenger plane will need supply at every place that people actually want to go.
True.  The cost of the fuel infrastructure was a major reason for cancelling the SR71 and LH2 is much tougher to handle.
Quote
As for the temperature of a just-landed A2, I imagine in normal aircraft operations you would have at least half an hour of subsonic flight before landing during which to cool down (getting in the runway queue for one thing), plus any active cooling if run at subsonic would bring the temperature down pretty fast, plus a low heat-capacity skin material, so i wonder if this might be a bit of a non-problem. Can anyone tell me if there were/ are heat handling issues with the Shuttle/ X37B post-landing?
The Shuttle had issues in this area. I recall something about the door area being at its hottest after landing. OTOH Shuttle covering was a mix of ceramic blankets and open cell ceramic foam. It's easy to see how these could be strongly heated during re entry and then form a layer of stagnant air around the vehicle during landing, making heat release quite a slow process.

But Skylons skin is a series of thin plates, which won't trap stagnant air. I'm not sure if it qualifies as "low" heat capacity.

I'd be very surprised if REL didn't get access to the NASA TPSX database on TPS materials for the Shuttle. I'd guess they've run quite a few simulations on Skylon entry by now  and have a pretty good idea of the vehicles temperature profile as it takes off and lands.
Quote
I hope these are valid points and am very happy to be corrected on them, just pleased to be part of the discussion :)
You're points are very valid.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/21/2015 11:50 PM
Is it not possible, even likely, that Lapcat/A2 was simply the wrong requirement? Yes ESA had good reasons for creating a future aircraft study and REL did a fine job of meeting their study needs, but that doesn't mean it's the best idea.

Once SABREs are shown to be effective and robust (here's hoping!) the entire focus of long-distance high speed air travel may well switch to sub-orbital hopping in a passenger vehicle with SABRE like engines. Why spend 5 hours getting from Europe to Australia (very impressive) when you can do it in 45 minutes - AND avoid all those really very difficult to solve skin heating issues.

Currently, people just don't think of a safe 'space' plane with high passenger numbers as a realistic option because it "isn't possible".
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: QuantumG on 07/22/2015 12:01 AM
It's hard to see how flying through the atmosphere for longer, in an SSTO, is going to make a space plane safer.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RobLynn on 07/22/2015 02:30 AM
Is it not possible, even likely, that Lapcat/A2 was simply the wrong requirement? Yes ESA had good reasons for creating a future aircraft study and REL did a fine job of meeting their study needs, but that doesn't mean it's the best idea.

I don't think M5 is really needed or a good idea.  Why not make it way easier on yourself and just go Mach 3 - then you can use simple titanium structure and skins, cheap turbo ramjets without high risk heat exchangers, bascially little new tech requried, also an L/D of 7-8 (probably 15-30% lower fuel burn than L/D~6 Lapcat), and still get antipodial range in 6 hours.  For total trip time of probably 11-12 hours door to door vs 9-10 hours for Mach5 and 30 hours for conventional subsonic.

At the end of the day seat-mile cost for such an aircraft is likely to be half the estimated $4-5k antipodal ticket cost of Lapcat.  And demand curves being what they are that probably increases your market by an order of magnitude and the potential commercial viability from no-chance, to maybe.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/22/2015 02:37 AM
It's hard to see how flying through the atmosphere for longer, in an SSTO, is going to make a space plane safer.

I am not a space expert. What I meant was flying a Skylon-like trajectory to get you to your destination - I meant absolutely not staying in the atmosphere and therefore avoiding those heating issues. Clearly re-entry has to be considered too, but that would already be worked through to some extent should Skylon-like craft actually get built.

I also wasn't implying any of that made it safer, but there is no reason why at some future date such a thing couldn't be relatively safe.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/22/2015 06:59 AM
Is it not possible, even likely, that Lapcat/A2 was simply the wrong requirement? Yes ESA had good reasons for creating a future aircraft study and REL did a fine job of meeting their study needs, but that doesn't mean it's the best idea.
ESA didn't issue this requirement.

LAPCAT was a research project from the EU under one of their FRAMEWORK R&D schemes, which encourage pan European co operation to solve common problems to a pre competitve stage. You might think of them as being like the sort of thing that the US DARPA and E-DARPA do, but including Canada and Mexico. FRAMEWORK programmes have supported everything from next generation chip lithography to domestic heat and power concepts using natural gas fuel cells. :)
Quote
Once SABREs are shown to be effective and robust (here's hoping!) the entire focus of long-distance high speed air travel may well switch to sub-orbital hopping in a passenger vehicle with SABRE like engines. Why spend 5 hours getting from Europe to Australia (very impressive) when you can do it in 45 minutes - AND avoid all those really very difficult to solve skin heating issues.
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

What Concorde demonstrated (and what the Boeing SST got right) was you need to carry a lot of passengers (in substantial comfort) to make it worthwhile. Most (all) post flight analysis of Concorde's economics said it was too small, and should have been 2x or 3x bigger (and the French wanted it smaller  :( )
Quote
Currently, people just don't think of a safe 'space' plane with high passenger numbers as a realistic option because it "isn't possible".
REL are quit clear that LAPCAT/A2 is not a space plane but a very fast conventional airliner, designed to carry large number of passengers (not "spaceflight participants") with minimal special training and incorporating things like powered landings. Like getting on any large general aviation aircraft, but for less time.

It's pretty clear if a > M2.2 transport gets built it will be a very different beast from Concorde, due to thermal considerations alone. It's also likely to different from Skylon.

I don't think M5 is really needed or a good idea.  Why not make it way easier on yourself and just go Mach 3 - then you can use simple titanium structure and skins, cheap turbo ramjets without high risk heat exchangers, bascially little new tech requried, also an L/D of 7-8 (probably 15-30% lower fuel burn than L/D~6 Lapcat), and still get antipodial range in 6 hours.  For total trip time of probably 11-12 hours door to door vs 9-10 hours for Mach5 and 30 hours for conventional subsonic.
Perhaps you should ask the EU that question.

They set the requirements.
Quote
At the end of the day seat-mile cost for such an aircraft is likely to be half the estimated $4-5k antipodal ticket cost of Lapcat. 
Based on what exactly?
Quote
And demand curves being what they are that probably increases your market by an order of magnitude and the potential commercial viability from no-chance, to maybe.
I've flown on those $5k business class tickets.

They did not seem to have any trouble filling seats, or rather individual "pods"

At a certain level of business the key constraint is no  longer money it's time, and M5 means you spend less of it in the air.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/22/2015 08:04 AM
there is another problem with a suborbital skylon- the pricing would be totally out of reach for everyone but the wealthiest. A LEO Skylon launch, in the best scenario possible, could lower the kg/price down to 350$. Even assuming lower costs for suborbital flights (let's say 150$ kg) and assuming it could carry 60 people (the double of a LEO flight) it would still be almost 40k $ per ticket. not much compared to the 200.000$/ticket it would cost to bring one passenger to LEO in the best-case scenario, but still....
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/22/2015 12:11 PM
there is another problem with a suborbital skylon- the pricing would be totally out of reach for everyone but the wealthiest. A LEO Skylon launch, in the best scenario possible, could lower the kg/price down to 350$. Even assuming lower costs for suborbital flights (let's say 150$ kg) and assuming it could carry 60 people (the double of a LEO flight) it would still be almost 40k $ per ticket. not much compared to the 200.000$/ticket it would cost to bring one passenger to LEO in the best-case scenario, but still....
Exactly.

Using a Skylon for occasional point to point delivery of high value goods may be viable as part of an operators business case (probably not an early adopter, but in a later wave of buyers) but it's not what Skylon is designed to do.

Such a transporter, flying either a sub orbital or a cruise trajectory, would need to be a very different vehicle. The upside is the maximum powered velocity would be lower (shrinking the vehicle) it would be all air breathing (eliminating the LOX tanks, also shrinking the vehicle), but then you need to make the payload bay much bigger. An early REL estimate was the Skylon design could carry 30 passengers but that was scaled down to split them into "short stay" IE coming back on the same Skylon that took them to (notionally) the ISS and "long stays" who'd been on orbit for months (years) and would need to come down on basically a stretcher.

Now sub orbital is a short flight (a LEO orbit is 90 mins, 45 min puts you anywhere on the planet from your launch point) so consumables should be minimal but the fact remains even if you increase the seating density (45 in the bay?) that's just not going to cut it when you're looking at needing 250-300  :(

Wheather it's a M5 cruising aircraft or a sub orbital vehicle (I don't think there's even an agreed term for one of these. SOV?) it won't be a Skylon.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: tl6973 on 07/23/2015 12:00 PM
I find it hard to pin down what I find most exciting about REL.

It's a toss-up between the engineering wonderments of SABRE and Skylon, and the actual Business Culture/ operating model of REL themselves.

There's plenty on this thread about the science, engineering and economics, so I'd like to talk more about the business. They seem to occupy this very intriguing, contradictory spot between old and new space - like a start up but with 30 years' experience/ existence, with a visionary idea but that will clearly require significant collaboration with traditional aerospace and government/ political bodies. A bunch of very British Boffins in a shed, with the increasing possibility of changing the entire game.

Of course it is very hard to comment accurately on an organisation from outside, but I am very impressed with their calm determination, ability to stay completely focused on a very clearly defined technology development roadmap, and organisational unity/ rationality/ lack of internal politics and strife.

I would be very interested to know people's thoughts on how this has come about. Is it down to strong visionary leadership? is it that having a small team and constrained resources forces one to maintain focus? is it simply because the design concept is so compelling? Was the experience of working with the government on HOTOL a good lesson in how NOT to run a development programme? or is it something else entirely?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/23/2015 02:04 PM
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

I accept everyone's points (although as usual perhaps not QuantumG's  ;) ), but I was trying to imagine a different study or future. One where a craft was specifically optimised for maximum passenger carrying purposes and sub-orbital - whatever the trajectory would be to minimise time in atmosphere, but maximise distance. So yes, not Skylon. A2 isn't Skylon either.

I am not at all saying that LAPCAT wasn't a useful study, I am merely suggesting that if the EU had given REL the money for a different study, to look into *that* sort of vehicle, they might have been able to propose a realistic design, different from both A2 and Skylon, but still using technology derived from SABRE engine technology, that would seat a significant number of passengers to make an economically viable vehicle and avoid the in-atmosphere heat problems.

Then we might get our 45 minute trip - and one hell of a ride ;)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: RonM on 07/23/2015 02:24 PM
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

I accept everyone's points (although as usual perhaps not QuantumG's  ;) ), but I was trying to imagine a different study or future. One where a craft was specifically optimised for maximum passenger carrying purposes and sub-orbital - whatever the trajectory would be to minimise time in atmosphere, but maximise distance. So yes, not Skylon. A2 isn't Skylon either.

I am not at all saying that LAPCAT wasn't a useful study, I am merely suggesting that if the EU had given REL the money for a different study, to look into *that* sort of vehicle, they might have been able to propose a realistic design, different from both A2 and Skylon, but still using technology derived from SABRE engine technology, that would seat a significant number of passengers to make an economically viable vehicle and avoid the in-atmosphere heat problems.

Then we might get our 45 minute trip - and one hell of a ride ;)

That would be fun, but I don't see it happening. There are no operational SSTs today because of cost, so I doubt suborbitals would be economically viable. Even the military doesn't have supersonic transports, let alone suborbitals.

Teleconferencing takes care of rapidly attending business meetings and missiles takes care of rapidly needing to reach out and touch someone.

An issue with suborbital passenger transport is all the time on the ground. You go to the airport, wait in the security line, wait to board, wait for takeoff, ***high speed flight***, wait to land, wait to disembark, wait for your luggage, wait in line for customs, leave airport and arrive at hotel. I'd rather take a cheaper subsonic flight and take a nap while in the air.

Skylon could make an interesting SSTO spacecraft, but I doubt it or any other technology will succeed as a suborbital transport.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/23/2015 02:37 PM
That would be fun, but I don't see it happening.

Ah! "There's no market for it"  :)

Even if that's true, it would be an interesting study.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 07/24/2015 07:23 AM
An issue with suborbital passenger transport is all the time on the ground. You go to the airport, wait in the security line, wait to board, wait for takeoff, ***high speed flight***, wait to land, wait to disembark, wait for your luggage, wait in line for customs, leave airport and arrive at hotel. I'd rather take a cheaper subsonic flight and take a nap while in the air.

Skylon could make an interesting SSTO spacecraft, but I doubt it or any other technology will succeed as a suborbital transport.

To solve a problem you first have to "have it".  We haven't really fixed the issues of the time it takes to offload and process people because perhaps we are only just beginning to experience them.

I still wonder if a ticket that cost you e.g. 5000 wouldn't also pay for expedited customs processing - or even perhaps processing onboard the flight.

As for getting on and off - I'm not saying this is the answer but at least people are thinking about the problem:

http://clipair.epfl.ch/
[youtube]
NEJ3bAh7LUw[/youtube]

I love it because I had a similar idea not long ago and it's nice to know it wasn't so ridiculous as to not even be considered. :-)
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/24/2015 10:09 AM
50k more likely than 5k.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/24/2015 10:32 AM
To solve a problem you first have to "have it".  We haven't really fixed the issues of the time it takes to offload and process people because perhaps we are only just beginning to experience them.

I still wonder if a ticket that cost you e.g. 5000 wouldn't also pay for expedited customs processing - or even perhaps processing onboard the flight.

As for getting on and off - I'm not saying this is the answer but at least people are thinking about the problem:
I had a similar idea not long ago and it's nice to know it wasn't so ridiculous as to not even be considered. :-)
I understand that the trip through Reagan at Washington DC is very fast.

It can be done if law makers are feeling inconvenienced enough to do something about it.  :(

Likewise a service that preloaded all your address, hotel and credit card details on a data base that is used to upload to the DHS system to expedite trips to and from the US was offered some years ago.

Until someone stole the laptop on which a copy was sitting from a locked office in the secure area of a major airport (as happened a few years ago).

As for this cargo module idea, considered and built (in the 1940's or 50's) in prototype by (IIRC) the Fairchild aircraft company.

The problem has always been compatibility.  You end with using the lowest common denominator.

Which turns out to be a) A person walking or b) A standardized air cargo package.

[EDIT and here it is.

https://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane ]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 07/27/2015 09:32 AM
Reaction Engines concept  of a full-scale Sabre ground demonstrator.
Clearly not a flight model engine yet, but massive progress if this proves successful in 2018/2019.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/27/2015 10:43 AM
Reaction Engines concept  of a full-scale Sabre ground demonstrator.
Clearly not a flight model engine yet, but massive progress if this proves successful in 2018/2019.
Where did this come from?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 07/27/2015 11:17 AM
From the Aviation Week digital magazine. Photo credit  Reaction Engines
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: aga on 07/27/2015 12:07 PM
from here, i guess (?):
http://aviationweek.com/technology/air-breathing-sabre-concept-gains-credibility
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pippin on 07/27/2015 01:50 PM
So many things wrong with that picture....
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/27/2015 03:19 PM
So many things wrong with that picture....
I'd certainly say it look like it was made by a graphics artist, not an engineer.

What specifically did you have in mind?
Title: The Reaction Engines Skylon Master Thread (5)
Post by: pippin on 07/27/2015 04:39 PM
Oh, it shows the engine running at power but just placed in some kind of better workshop table assembly. So it doesn't have any thrust?
Four radiation cooled nozzles that close to each other would immediately burn through.
With all that it's almost irrelevant that all the deep-cold cryo piping is uninsulated and that the air inlet would suck up all kind of stuff at that power and so on.

It's so: oh, we have this image of the raw engine assy, let's just display it at work....
And then let's add these glowing red-hot engine bells people know from the SpaceX videos, they look so cool...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 07/27/2015 05:15 PM
It has come from  Aviation Week, who are crediting it to Reaction Engines, if this is correct,we have to ask what
is the purpose of what you guys clearly feel does not have any real engineering relevance to a fully engineered prototype engine on its test stand.



Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 07/27/2015 05:23 PM
Why all the consternation? It's just a notional graphical representation of a current project from a company that is not known for spending a lot of effort on PR materials. As far as I can tell the glass is half full.

And it's not as if other companies (i.e. SpaceX) haven't released graphics and animations before now that are notional at best.
___________
Plus the SABRE 4 cycle is still under wraps, so that's an additional good reason to show something vaguely representative rather than rendering the actual test bed design.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 07/27/2015 05:38 PM
In the past Reaction Engines have always produced nothing less than full on engineering diagrams.

Possibly they are now starting to use PR in a much more positive way.

The new MD no doubt will want to raise the profile of the company as they push for more funding, which over the next few years will need to be not millions but billions!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/28/2015 05:30 PM
For those of us that aren't subscribed to Aviation Weekly, does it say anything new or interesting in the article?  Thanks.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 07/28/2015 08:05 PM
For those of us that aren't subscribed to Aviation Weekly, does it say anything new or interesting in the article?  Thanks.

Hi Citizen Wolf,

If you view aga's post it has a link to the Aviation Week's article.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ElGuapoGuano1 on 07/28/2015 08:15 PM
Hankelow8, right, but as was said, if you are not subscribed to Aviation Week, you don't really see the article, you only get a paragraph...
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/28/2015 08:23 PM
@Hankelow8
If you're not subscribed to Aviation Weekly you come up against a pay wall and can't see the article.

EDIT: oops sorry, ElGuapoGuano has already said the same thing.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: kch on 07/28/2015 08:42 PM
Hankelow8, right, but as was said, if you are not subscribed to Aviation Week, you don't really see the article, you only get a paragraph...

... not worth clicking, really (unless you're a subscriber).  "Next!"
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/29/2015 03:41 PM
From the Aviation Week digital magazine. Photo credit  Reaction Engines
That's an interesting qualification.

I've just seen the hard copy version (dated July 20th onward) and this picture is not in there .

The article is a one pager and seems to part of their coverage of the AIAA Hypersonics and reentry conference, held (for reasons I'm not clear about) in Glasgow, Scotland.

It's only illustration is a cutaway of the pre cooler/front of engine section of SABRE.

There are also reports on hypersonic airliner design where efforts are being made to combine European and Japanese efforts in this area LAPCAT is mentioned but initial goals are for a 100 seat design at a price  2x that of current average business class tickets. They are targeting 200 such vehicles globally with point to point services for routes over up to (and ideally around ) 6200nm.

Possibly the most relevant item to Skylon were the data points from SR71 operations. The M5 airliner concept is targeting 48 hr turnaround. Comments by former SR71 staff state that when flying it took 19 hrs to go from a flight request to takeoff for a flight ready aircraft (IE not needing overhaul).

They noted that to get it ready for a next flight would take (on average) 1 week and if serious work needed to be done then about 1 month. They listed several areas of problems but the only one I recall was rivets being popped by the flight conditions.

I suspect at least one member of REL was at the conference and was taking careful notes of such points, if they weren't already aware of them, to refine their Skylon plans.

I also found the "commentary" section on page 11, on why grouping "Aerospace" with "Defense" is becoming increasingly misleading. It compared Airbus, Boeing and LM product mixes.

I'm not the only one who thinks of LM as strictly a government contractor and nothing else.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Jim on 07/29/2015 03:45 PM

I'm not the only one who thinks of LM as strictly a government contractor and nothing else.

Doesn't mean it is right.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/29/2015 10:05 PM

I'm not the only one who thinks of LM as strictly a government contractor and nothing else.

Doesn't mean it is right.
When it's someone who makes their living analyzing companies in (or not in) the aerospace and defense business whose reputation matters to them I think that adds credibility to the view.

However let's look at LM's market segments, from their 2014 annual report.

Aeronautics.
"is engaged in the research, design, development, manufacture, integration, sustainment, support and upgrade of advanced military aircraft,"
IE Military aircraft, mostly for the US government.

Information Systems & Global Solutions.
"IS&GS provides advanced technology systems and expertise, integrated information technology solutions and management services across a broad spectrum of applications for civil, defense, intelligence and other government customers. "
So basically selling IT systems and services to governments.

Missiles & Fire Control.
I think this is pretty self explanatory. Not something you sell to private customers.

Mission Systems & Training
"In 2014, U.S. Government customers accounted for 75%, international customers accounted for 24% and U.S. commercial and other customers accounted for 1% of MST’s net sales."
So 1% of this segments $7.1Bn revenue is from civilian customers.

Space Systems
"In 2014, U.S. Government customers accounted for 97%, international customers accounted for 1% and U.S.commercial and other customers accounted for 2% of Space Systems’ net sales. "
So maybe 2% of their $8.1Bn revenue is commercial.
"Operating profit for our Space Systems business segment includes our share of earnings for our 50% ownership interest in United Launch Alliance (ULA)."

On that basis I think I'd suggest most people looking at LM would conclude it's essentially a government contractor, mostly (but not entirely) for the US government. Non governmental works is a very small part of their total revenue.

Which I would suggest makes them about the worst candidate for building a large commercially funded project to a (relatively) tight time scale and budget, where you can't get an additional appropriation if you overrun your budget.
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/29/2015 11:15 PM

I'm not the only one who thinks of LM as strictly a government contractor and nothing else.

Doesn't mean it is right.
When it's someone who makes their living analyzing companies in (or not in) the aerospace and defense business whose reputation matters to them I think that adds credibility to the view.

However let's look at LM's market segments, from their 2014 annual report.

Aeronautics.
"is engaged in the research, design, development, manufacture, integration, sustainment, support and upgrade of advanced military aircraft,"
IE Military aircraft, mostly for the US government.

Information Systems & Global Solutions.
"IS&GS provides advanced technology systems and expertise, integrated information technology solutions and management services across a broad spectrum of applications for civil, defense, intelligence and other government customers. "
So basically selling IT systems and services to governments.

Missiles & Fire Control.
I think this is pretty self explanatory. Not something you sell to private customers.

Mission Systems & Training
"In 2014, U.S. Government customers accounted for 75%, international customers accounted for 24% and U.S. commercial and other customers accounted for 1% of MST’s net sales."
So 1% of this segments $7.1Bn revenue is from civilian customers.

Space Systems
"In 2014, U.S. Government customers accounted for 97%, international customers accounted for 1% and U.S.commercial and other customers accounted for 2% of Space Systems’ net sales. "
So maybe 2% of their $8.1Bn revenue is commercial.
"Operating profit for our Space Systems business segment includes our share of earnings for our 50% ownership interest in United Launch Alliance (ULA)."

On that basis I think I'd suggest most people looking at LM would conclude it's essentially a government contractor, mostly (but not entirely) for the US government. Non governmental works is a very small part of their total revenue.

Which I would suggest makes them about the worst candidate for building a large commercially funded project to a (relatively) tight time scale and budget, where you can't get an additional appropriation if you overrun your budget.

Military government applications are likely to reach reality before any commercial ones are and in that case LM are ideally placed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/30/2015 07:06 AM
Military government applications are likely to reach reality before any commercial ones are and in that case LM are ideally placed.
That's an assertion.

Perhaps you could take us through your reasoning?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: francesco nicoli on 07/30/2015 07:18 AM
guys, did you see the design for an airbreathing nuclear rocket reported by nextbigfuture? I know that it's just summer speculation, but I was wondering whether an integrated design with the SABRE is, as a pure matter of principle, possible.

http://nextbigfuture.com/2015/07/nuclear-thermal-turbo-rocket-with.html
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 07/30/2015 10:46 AM
The Aviationweek article is now generally available.  I suppose the idea is that subscribers get it early but the public gets it eventually.

Here's the link again:
http://aviationweek.com/technology/air-breathing-sabre-concept-gains-credibility?NL=AW-05&Issue=AW-05_20150730_AW-05_233&sfvc4enews=42&cl=article_1&utm_rid=CPEN1000001204273&utm_campaign=3312&utm_medium=email&elq2=de275daceef84b74b5541bcb84290e12
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/30/2015 12:08 PM
Military government applications are likely to reach reality before any commercial ones are and in that case LM are ideally placed.
That's an assertion.

Perhaps you could take us through your reasoning?

Fairly simple the military will always get first dibs on something like this once they are persuaded it works and does what it says on the can. The commercial sector is often more risk adverse and though the military can be conservative in these things as well, if they are persuaded they are far more likely to put money into something like this.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: oddbodd on 07/30/2015 01:06 PM
guys, did you see the design for an airbreathing nuclear rocket reported by nextbigfuture? I know that it's just summer speculation, but I was wondering whether an integrated design with the SABRE is, as a pure matter of principle, possible.

http://nextbigfuture.com/2015/07/nuclear-thermal-turbo-rocket-with.html

Fission is a barely controlled potential runaway catastrophe. And the idea of strapping one to a type of vehicle that flies over our heads, and typically has a 1 in 50 chance of exploding... I would never say never, but very unlikely. The US and USSR experimented with nuclear powered airplanes, but they only did a few test flights with the reactor on board, and not active, before the ICBM made them pointless. One of the issues was the mass for shielding, and in a mass sensitive concept like Skylon, it just doesn't make sense as far as I can see.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Jim on 07/30/2015 01:22 PM
On that basis I think I'd suggest most people looking at LM would conclude it's essentially a government contractor, mostly (but not entirely) for the US government. Non governmental works is a very small part of their total revenue.

Which I would suggest makes them about the worst candidate for building a large commercially funded project to a (relatively) tight time scale and budget, where you can't get an additional appropriation if you overrun your budget.

That is a statement based on bias and not supported by any relevant data.  Not all gov't contracts are cost plus.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/30/2015 02:13 PM

On that basis I think I'd suggest most people looking at LM would conclude it's essentially a government contractor, mostly (but not entirely) for the US government. Non governmental works is a very small part of their total revenue.

Which I would suggest makes them about the worst candidate for building a large commercially funded project to a (relatively) tight time scale and budget, where you can't get an additional appropriation if you overrun your budget.

That is a statement based on bias and not supported by any relevant data.  Not all gov't contracts are cost plus.

There seems to be a degree of either accidental or deliberate misunderstanding of LM's business.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 07/30/2015 03:15 PM
guys, did you see the design for an airbreathing nuclear rocket reported by nextbigfuture? I know that it's just summer speculation, but I was wondering whether an integrated design with the SABRE is, as a pure matter of principle, possible.

http://nextbigfuture.com/2015/07/nuclear-thermal-turbo-rocket-with.html

Fission is a barely controlled potential runaway catastrophe. And the idea of strapping one to a type of vehicle that flies over our heads, and typically has a 1 in 50 chance of exploding... I would never say never, but very unlikely. The US and USSR experimented with nuclear powered airplanes, but they only did a few test flights with the reactor on board, and not active, before the ICBM made them pointless. One of the issues was the mass for shielding, and in a mass sensitive concept like Skylon, it just doesn't make sense as far as I can see.

This has actually been extensively discussed in some of the nuclear threads, Ranulf has a lot to say about it. Essentially  the  SABRE cycle is well suited to having a nuclear derivative as the rocket combustion chamber can just be replaced with the reactor and the compressed air can be injected into the nozzle in an air augmented mode, potentially followed by an Lox augmented mode. The technology was actually listed in the 2012 NASA draft technology roadmap.
The performance benefit however is very dependant on how much shielding you require and the T/W of your reactor core. ANP shielding encased the reactor in concentric spheres of tungsten and lithium hydride such that you could stand next to the thing and get more radiation coming in through the window and the plane could plow into a mountain and the shielding would never crack and the reactor never melt down. By the nature of reactor power to mass to volume this meant that ANP only makes performance sense for aircraft sized 500mt and up (A380 sized). So a full ANP shielded SABRE engine would only make sense on a large launch vehicle but just how large depends on your shielding requirements and your reactor T/W.   

 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/30/2015 04:26 PM
guys, did you see the design for an airbreathing nuclear rocket reported by nextbigfuture? I know that it's just summer speculation, but I was wondering whether an integrated design with the SABRE is, as a pure matter of principle, possible.

http://nextbigfuture.com/2015/07/nuclear-thermal-turbo-rocket-with.html
You need to develop a bit more of a feel for engineering.  :(

This thing starts with an unflown concept and stacks the untested ideas on top of it.  Variable pitch fan blade trailing edges structured as linear aerospikes ducting 2000c GH2 through them ::) Most metals melt below this temperature. 

At the end of it you've got something with maybe an Isp of 900sec + and double thrust for a period.

SABRE delivers somewhere around 2-4000 secs without a nuclear fuel element in site.

The Aviationweek article is now generally available.  I suppose the idea is that subscribers get it early but the public gets it eventually.

Here's the link again:
http://aviationweek.com/technology/air-breathing-sabre-concept-gains-credibility?NL=AW-05&Issue=AW-05_20150730_AW-05_233&sfvc4enews=42&cl=article_1&utm_rid=CPEN1000001204273&utm_campaign=3312&utm_medium=email&elq2=de275daceef84b74b5541bcb84290e12

Tried to log in but failed to do so.

Then I read the level of the comments left.

Deeply disappointing.   :(

That is a statement based on bias and not supported by any relevant data.  Not all gov't contracts are cost plus.
I think the LM annual accounts is very relevant data if you're trying to decide how much of a companies revenue comes from being a government contractor or from selling in the open market.

And I have so far said nothing about what proportion of LM's contracts are cost plus or firm fixed price.

I fully accept that something like the Orion capsule will be cost plus (I don't know about you but I'm so excited for when that SM comes in from Europe and it's mated to the capsule for the first time. I'm sure it'll be worth the wait)

OTOH I doubt the F35 production contract is cost plus, give that should have all been worked out in development (although judging by that shoot out with an F16 described in this edition the flight control system seems a bit of tweaking).

Fairly simple the military will always get first dibs on something like this once they are persuaded it works and does what it says on the can.
Unfortunately it doesn't work that way. They may like the technology but the USAF cannot develop it. It has to have a "competition" or very good reasons to have a single source to get a programme going and of course that would leave the USAF with an engine but no aircraft.

Since REL don't make aircraft, that's the job of the Skylon mfg consortium, that leaves them in something of an impasse.
Quote
The commercial sector is often more risk adverse and though the military can be conservative in these things as well, if they are persuaded they are far more likely to put money into something like this.
That's a very sweeping generalization. Strictly speaking it will be the US Congress who puts US taxpayers money into it.

At present I think the USAFRL study provides a strong case to US readers that the technology works.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 07/30/2015 04:58 PM
I have an unpaid login - perhaps that's why I could read it.  It wasn't available to me until today though - perhaps there is some progression.

The interesting bits to me were sort of casting doubt on Skylon being the first application of Sabre.

I'm not sure about copyright so I'm quoting the quotes as I doubt they can be owned:

Quote
"The question to answer next is what benefit the Sabre could bring to high-speed aerospace vehicles compared to other propulsion systems,”

“AFRL is analyzing vehicle designs based on the Sabre engine concept. We are also considering testing their heat-exchanger technology at Mach 5 flight conditions in a high-temperature wind tunnel.”
(Hellman, AFRL)

Skylon is:
Quote
“very risky as a first application,”
“Sabre may provide some unique advantages in more manageable two-stage-to-orbit configurations.”
(Hellman, AFRL)

Quote
“From our perspective there is no cheap, quick way around the problem of space access. We’ve done studies and we agree that [a] sensible second-stage approach might be best to demonstrate the technology by taking it one step at a time,”
(Sam Hutchison, Reaction Engines)

Quote
“Enough people now say the Sabre cycle works and it looks compelling. Now the question is what will we do with it?“ As an engine class, it straddles both air and space, so we have to optimize a system to take advantage of that for a given application. As we structure the development plan going forward, we can figure out what the first use is going to be. So over the next six months we will be closing in on that application.”

“Right now we are in the process of scoping that demonstration engine in terms of what it needs to achieve,”

“The key thing is to tick the boxes in every area it needs to tick. It is all about making sure the demonstrator meets the performance requirements that are set for it. We want to make sure it really works and offers the sort of performance that we say it can do. We’re still in that phase. The studies are in their infancy for the engine demonstrator but we have got to make sure we’re not biting off too much more than we can chew.”

(Hutchison)

Apparently the demonstrator is on track to do a full engine test in  2018/2019.

Ground testing is possible :
Quote
“because the engine uses the atmosphere as the source of its energy and the reaction mass. And because of the clever heat-exchanger technology, we can modulate the air so the turbomachinery in the engine doesn’t know it is on the ground.”
(Hutchison) 

They plan to simulate higher velocity air by raising the temperature of the air entering the inlet. They are also going to do wind tunnel tests with the inlet.

The AFRL suggest that they might do Mach 5 tests in a high temperature wind tunnel.

There are apparently no short term funding shortfalls.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Moe Grills on 07/30/2015 05:04 PM
That's a very sweeping generalization. Strictly speaking it will be the US Congress who puts US taxpayers money into it.

At present I think the USAFRL study provides a strong case to US readers that the technology works.
[/quote]

You may not approve, but I would like to make a "sweeping generalization" by saying that the Skylon/Sabre-engine technology may be the proverbial "silver bullet" that space-travel enthusiasts/fans have been waiting for for decades.
At least for travel from ground to LEO and back.
For the proverbial "silver bullet" for space-travel and space projects beyond LEO to deep space?  Skylon is not the answer to that need, but maybe that sensationalized EM Drive I've read about recently (if it works) may fit
hand-in-glove with Skylon to revolutionize space-travel completely. When was the last time "REVOLUTIONIZE" has been used authentically and verifiably to describe new/advanced  tech developments for space-travel? 
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/30/2015 05:43 PM
LM have the SR-72 concept which is looking for a pair of engines. The thing is these prototype programs can often end up black budget items where it's hard to see what's happening with them.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/30/2015 06:57 PM
LM have the SR-72 concept which is looking for a pair of engines. The thing is these prototype programs can often end up black budget items where it's hard to see what's happening with them.
No they are not.  They have partnered with Aerojet Rocketdyne for a turbo ram/SCRamjet  engine.

LM think they already have an engine for their concept (and it's nowhere near cutting metal at this point).
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/30/2015 08:32 PM

LM have the SR-72 concept which is looking for a pair of engines. The thing is these prototype programs can often end up black budget items where it's hard to see what's happening with them.
No they are not.  They have partnered with Aerojet Rocketdyne for a turbo ram/SCRamjet  engine.

LM think they already have an engine for their concept (and it's nowhere near cutting metal at this point).

Concepts can change. As you've just pointed out this whole thing is a paper exercise at this point so there's nothing stopping things being altered at this time.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: livingjw on 07/30/2015 10:32 PM
If we assume that the engine works as advertised, what is it good for. It cannot possibly do SSTO while airbreathing to only Mach 5 without extremely advanced materials. A TSTO reusable design can be more easily accomplished with a TSTO rocket or rocket boosted Scramjet. So what mission would it do better than some other technology? I really don't understand the fascination with this cycle, which dates back to the 1960's.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: QuantumG on 07/30/2015 10:41 PM
Welcome to the forum livingjw.. I see you've taken Jon Goff's advice on learning about things on the Internet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/30/2015 11:24 PM
Welcome to the forum livingjw.. I see you've taken Jon Goff's advice on learning about things on the Internet.
Neatly demonstrates why I didn't persist with getting the free logon to AV&ST.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/31/2015 02:15 AM
@Livingjw

Ooow, you came in with a howler of a poor question there as a first post.

As a starter, check out reaction engines website: http://www.reactionengines.co.uk/

But as a quick answer to your question, the SABRE engine is a dual air-breathing AND rocket engine. The air-breathing cycle has a rather nifty and advanced heat-exchanger to stop things melting. If it performs to expectations, SABRE should do SSTO.


Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 07/31/2015 11:28 AM
Skylon is:
Quote
“very risky as a first application,”
“Sabre may provide some unique advantages in more manageable two-stage-to-orbit configurations.”
(Hellman, AFRL)
SABRE is designed to do one job. Get the vehicle it's attached to from a standing start on a runway to Low Earth Orbit.

If they didn't want that they should have said so and asked either for a hypersonic cruise engine like LAPCAT (which is very different internally) or the HX technology to put on the front of a turbofan.

It seems they either didn't realize how closely this is tied into the use of LH2 or they didn't really believe it could work at all.  Unfortunately now they've run the analysis themselves they now realize it can, and they're not sure what to do about it.  :(
Quote
(Sam Hutchison, Reaction Engines)

Quote
“Enough people now say the Sabre cycle works and it looks compelling. Now the question is what will we do with it?“ As an engine class, it straddles both air and space, so we have to optimize a system to take advantage of that for a given application. As we structure the development plan going forward, we can figure out what the first use is going to be. So over the next six months we will be closing in on that application.”

“Right now we are in the process of scoping that demonstration engine in terms of what it needs to achieve,”

“The key thing is to tick the boxes in every area it needs to tick. It is all about making sure the demonstrator meets the performance requirements that are set for it. We want to make sure it really works and offers the sort of performance that we say it can do. We’re still in that phase. The studies are in their infancy for the engine demonstrator but we have got to make sure we’re not biting off too much more than we can chew.”

(Hutchison)

Are you sure this guy works for REL? That's just amazingly lukewarm. I'd guessed REL had a pretty good idea of what they needed the demonstrator to demonstrate.
Quote

Apparently the demonstrator is on track to do a full engine test in  2018/2019.

Ground testing is possible :
Quote
“because the engine uses the atmosphere as the source of its energy and the reaction mass. And because of the clever heat-exchanger technology, we can modulate the air so the turbomachinery in the engine doesn’t know it is on the ground.”
(Hutchison) 

They plan to simulate higher velocity air by raising the temperature of the air entering the inlet. They are also going to do wind tunnel tests with the inlet.

The AFRL suggest that they might do Mach 5 tests in a high temperature wind tunnel.

There are apparently no short term funding shortfalls.
The precooler (and it's frost control) were a)The thing that lets the engine see near constant inlet conditions from 0 to M5.5, so allowing you to design an efficient engine for a fairly narrow operating range, instead of a one size fits all, to be adequate over the whole range, and b) The one thing that had never been fully tested.

The point I note is that patents can tell you that if you make a HX of a certain size with tubes of a certain size and frost control working a certain way it will let you do certain things.

But they don't tell you how to do those things.

I sincerely hope those matters stay within REL.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 07/31/2015 01:46 PM
Sam Hutchison
**As we structure the development plan going forward, we can figure out what the first use is going to be.**

That sounds like a really odd thing for someone from REL to say. Was he thinking one thing and said another. I thought they knew what the first use of the SABRE was going to be. I thought they had designed it from the start to be an SSTO. Nothing else. Not a sub-orbital whatever, or a high-Mach quick reaction craft for USAF.  wtf?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 07/31/2015 02:22 PM
Sam Hutchison
**As we structure the development plan going forward, we can figure out what the first use is going to be.**

That sounds like a really odd thing for someone from REL to say. Was he thinking one thing and said another. I thought they knew what the first use of the SABRE was going to be. I thought they had designed it from the start to be an SSTO. Nothing else. Not a sub-orbital whatever, or a high-Mach quick reaction craft for USAF.  wtf?
It might be helpful to remember that Sam Hutchison is Director of Corporate Development at REL and  CEO of Skylon Enterprises Ltd so from his perspective he's probably saying that they've got this great piece of technology that they're going to build a SSTO with but which can usefully be applied to a bunch of other tasks on a quicker time frame at lower costs with a small amount of effort on their part so they're in the process of working out which use cases are worth pursuing in order to generate income while they work on Skylon.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 07/31/2015 02:32 PM
Skylon is:
Quote
“very risky as a first application,”
“Sabre may provide some unique advantages in more manageable two-stage-to-orbit configurations.”
(Hellman, AFRL)
SABRE is designed to do one job. Get the vehicle it's attached to from a standing start on a runway to Low Earth Orbit.

If they didn't want that they should have said so and asked either for a hypersonic cruise engine like LAPCAT (which is very different internally) or the HX technology to put on the front of a turbofan.

It seems they either didn't realize how closely this is tied into the use of LH2 or they didn't really believe it could work at all.  Unfortunately now they've run the analysis themselves they now realize it can, and they're not sure what to do about it.  :(
Could you explain  perhaps exactly how you see SABRE 4 and Scimitar as very different internally? To my eyes SABRE 4 seems Scimitar inspired.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 07/31/2015 08:16 PM
As we structure the development plan going forward, we can figure out what the first use is going to be. So over the next six months we will be closing in on that application.”

“Right now we are in the process of scoping that demonstration engine in terms of what it needs to achieve,”
ly hope those matters stay within REL.

It does sound a bit disappointing. It reads like might be getting guided by partners (the USAF?) as to what prototype they build to suit partner requirements. Maybe that seems the best reliable place they can get the money from for their prototype. Still that might turn out to be a great technology demonstrator flight application that might actually get built and prove the technology much quicker than any of us hoped - which wouldn't in itself be a bad thing.... it would still be a diversion from the creation of Skylon though which delays the Skylon dream further!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 07/31/2015 08:56 PM
I'm confident you're reading too much into this. It would be a different matter if Alan Bond said "we're switching to TSTO" publicly, but here you have their Director of Corporate Development sound just exactly like someone in that role should: he's being broadly supportive of the AFRL statement - i.e. their recent partner who they may hope to work with again (read $$$$ that could help further the Skylon project).
Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 07/31/2015 09:01 PM
I'm confident you're reading too much into this. It would be a different matter if Alan Bond said "we're switching to TSTO" publicly, but here you have their Director of Corporate Development sound just exactly like someone in that role should: he's being broadly supportive of the AFRL statement - i.e. their recent partner who they may hope to work with again (read $$$$ that could help further the Skylon project).

How would we know there not still actively working with the USAF, it may not be something the USAF wish broadcasting.

I personally feel if the USAF want a hypersonic vehicle of some type then REL are their best best to achieve this.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 07/31/2015 09:18 PM
I suppose they could be. And that would be one more reason it would be smart to ensure comments made in public are in sync.

(By way of contrast it would not be wise for REL to say "SABRE is for SSTO, if USAF don't get that they're idiots. But we'll take their money anyway.)"

And we may as well remember that the cautious amongst us could be right. An unforeseen performance/mass issue could yet kill hopes of SSTO.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 07/31/2015 10:55 PM
I'm confident you're reading too much into this. It would be a different matter if Alan Bond said "we're switching to TSTO" publicly, but here you have their Director of Corporate Development sound just exactly like someone in that role should: he's being broadly supportive of the AFRL statement - i.e. their recent partner who they may hope to work with again (read $$$$ that could help further the Skylon project).

How would we know there not still actively working with the USAF, it may not be something the USAF wish broadcasting.

I personally feel if the USAF want a hypersonic vehicle of some type then REL are their best best to achieve this.

According to their press release regarding the results of the CRADA it is an ongoing relationship as it states :

"Reaction Engines Ltd. and AFRL are now formulating plans for continued collaboration on the SABRE engine; the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system, testing of SABRE engine components and exploration of defence applications for Reaction Engines’ heat exchanger technologies."

Note it states "SABRE derived" regarding what they want to put in a vehicle.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 08/01/2015 06:56 AM
It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.

How could one turn up one's nose at a chance to try out some aspects of Skylon/Sabre without needing to go directly to a $10 billion SSTO?  It could be a godsend.

That might control what aspects the engine demonstrator has to be most realistic about, how much money has to be spent on it and where.

Title: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 08/01/2015 08:28 AM
It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.

How could one turn up one's nose at a chance to try out some aspects of Skylon/Sabre without needing to go directly to a $10 billion SSTO?  It could be a godsend.

That might control what aspects the engine demonstrator has to be most realistic about, how much money has to be spent on it and where.

That's my view why turn down money to develop technology that may eventually help you achieve your commercial aims.

My only fear is the USAF 'locking up' some vital technology for their use only.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 08/01/2015 10:11 AM
Star One
**My only fear is the USAF 'locking up' some vital technology for their use only.**

That's what I was thinking also. Comments from AFRL suggest that they don't think SSTO is a good or viable option. But they do seem to think that the SABRE technology is useful for them in some other way. They could then have further arrangements with REL to develop certain aspects of the SABRE technology to implement their goals (not SSTO). These technology improvements would become tied up in military/national security concerns and SSTO/Skylon won't happen. At least certainly not in the timeframe as currently envisioned by REL. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: flymetothemoon on 08/01/2015 10:21 AM
At least certainly not in the timeframe as currently envisioned by REL.

Yes. It's the timeframe I find bothersome after waiting (in mine and many people's case) more than 30 years since I was a boy to see Mr Bond's baby fly.

Still if a really good working demonstrator comes out of it, then the belief should be there and it might be full steam ahead for applications after that which wouldn't be so bad. Quite frankly I also want Alan Bond to see his Dan Dare inspired boyhood dreams realised - and superb engineering vindicated - before it's too late!
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 08/01/2015 10:26 AM
Star One
**My only fear is the USAF 'locking up' some vital technology for their use only.**

That's what I was thinking also. Comments from AFRL suggest that they don't think SSTO is a good or viable option. But they do seem to think that the SABRE technology is useful for them in some other way. They could then have further arrangements with REL to develop certain aspects of the SABRE technology to implement their goals (not SSTO). These technology improvements would become tied up in military/national security concerns and SSTO/Skylon won't happen. At least certainly not in the timeframe as currently envisioned by REL.
Worrying this, I do hope they have enough experience  dealing with any contracts that AFRL might throw at them that does not tie their hands for future UK development.

But one has to realise they are a business with financial backers that expect a return on their investment.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Paul451 on 08/02/2015 12:11 AM
It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.
My only fear is the USAF 'locking up' some vital technology for their use only.

Bond & Co have been down that path before, with their own HOTOL work being locked behind (ultimately pointless) restrictions. I doubt they will go down the same path unless they have an "out" that allows them to continue REL/Skylon when the USAF program is inevitably cancelled.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 08/02/2015 09:00 AM

It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.
My only fear is the USAF 'locking up' some vital technology for their use only.

Bond & Co have been down that path before, with their own HOTOL work being locked behind (ultimately pointless) restrictions. I doubt they will go down the same path unless they have an "out" that allows them to continue REL/Skylon when the USAF program is inevitably cancelled.

I wouldn't assume on it being cancelled considering the current political situation.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 08/02/2015 10:14 AM
Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 08/02/2015 12:06 PM

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 08/02/2015 12:55 PM
Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are). 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: ClaytonBirchenough on 08/02/2015 01:45 PM
Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: meiza on 08/02/2015 02:07 PM
Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.
I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.

Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 08/02/2015 02:55 PM

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?

I wonder if the NASA study into its proposed engines has finished yet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/02/2015 03:00 PM
Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.
You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

SABRE was designed from day one to eliminate SCRamjets because in the late 70's and early 80's it was basically a fantasy technology.

And despite the billions of dollars the USG has pumped into the technology it still is.  :(

I wouldn't assume on it being cancelled considering the current political situation.
Meaning what exactly?
Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.
And where SCRamjets are concerned there is so much chaff to begin with.  :(

It took a lot of reading to find that an SCRamjet has a listed T/W of 2. The turbojet on the SR71 has a T/W of about 5.3. It's estimated the nacelle halved that to about 2.6.

So after 55 years an SCRamjet may deliver  an T/W almost as good as the SR71 package did in the early 60s.

Once you know that it's no wonder they are having trouble launching even a missile based on this technology.
At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment.
And yet no one thinks this is quite a big clue that SCRamjets are not a very good design idea.  :(
Every SCRamjet test vehicle has started strapped to a rocket and the rocket has normally got it to starting speed with few hitches.
Quote
Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).
They are but this needs LH2 and armed forces are very wary of cryogenics.
One of the reasons for ending the SR71 is they did not like maintaining the supply chain (a global network of dedicated ground tanks and tanker aircraft) for the JP7 fuel

Not cryogenic. Not toxic. Just not JP4.
LH2 is a much more serious commitment for a unit of reconnaissance aircraft. OTOH as a launcher you could base it at one of the old B36 rated runways, of which the USAF has 3. You'd take a payload hit but you can launch from CONUS and be back at base within a day. Kind of like an orbital B2.

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.
A modern turbofan delivers a T/W of 10:1. SABRE's design goal is 14:1. IE about 40% better than a SoA jet engine. That's poor by rocket standards but an Isp 6x or 8x better than the best rocket engine (while air breathing, otherwise it's mere as good as the best Isp of known rocket engines) makes a big difference in building an LV.
Quote
I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.
Not really.
Firstlyif you've got air breathing your Isp goes up a lot compared to rockets and you can use wings. SABRESkylon is designed to use both. 

Secondly launch puts the airframe at maximum temperature for a very limited period of time. 10s of secs at maximum AB Mach before it goes to full rocket mode and a few 10s of minutes on re entry at most.

Cruise is like re-entry but lasting for hours requiring continual dumping of enormous quantities of heat from the whole airframe. That lets you use design approaches that won't work for long periods but are perfectly acceptable for the launch/reentry mission.

If you don't understand that difference you need to study a bit more engineering.

BTW HTOL takes a thrust roughly 1/3 (or in extreme cases 1/4) the GTOW. OTOH if you go with VTOL the thrust must exceed the weight by a significant amount or there is no take off at all.

Quote
Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.
There have been many designs put up by SCRamjet proponents over the years. Various proposals attracted substantial funding. X30 got $Bn+.

All had (in hindsight) low TRL's so IRL it was going to be a case of build the vehicle to test the engine. Which, giving the high levels of uncertainty about M5 combustion and flight meant the probable result was that you'd throw the aircraft away and have to start again.
None have built an actual flight vehicle.

SABRESkylon is designed to avoid as much uncertainty as possible. The engine was designed (from day one) to be tested on the ground, so when you design the vehicle you already know it's going to work. The question then becomes how well can you design the vehicle to deliver that potential.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 08/02/2015 04:46 PM

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.


yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Star One on 08/02/2015 06:05 PM

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.
You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

SABRE was designed from day one to eliminate SCRamjets because in the late 70's and early 80's it was basically a fantasy technology.

And despite the billions of dollars the USG has pumped into the technology it still is.  :(

I wouldn't assume on it being cancelled considering the current political situation.
Meaning what exactly?
Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.
And where SCRamjets are concerned there is so much chaff to begin with.  :(

It took a lot of reading to find that an SCRamjet has a listed T/W of 2. The turbojet on the SR71 has a T/W of about 5.3. It's estimated the nacelle halved that to about 2.6.

So after 55 years an SCRamjet may deliver  an T/W almost as good as the SR71 package did in the early 60s.

Once you know that it's no wonder they are having trouble launching even a missile based on this technology.
At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment.
And yet no one thinks this is quite a big clue that SCRamjets are not a very good design idea.  :(
Every SCRamjet test vehicle has started strapped to a rocket and the rocket has normally got it to starting speed with few hitches.
Quote
Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).
They are but this needs LH2 and armed forces are very wary of cryogenics.
One of the reasons for ending the SR71 is they did not like maintaining the supply chain (a global network of dedicated ground tanks and tanker aircraft) for the JP7 fuel

Not cryogenic. Not toxic. Just not JP4.
LH2 is a much more serious commitment for a unit of reconnaissance aircraft. OTOH as a launcher you could base it at one of the old B36 rated runways, of which the USAF has 3. You'd take a payload hit but you can launch from CONUS and be back at base within a day. Kind of like an orbital B2.

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.
A modern turbofan delivers a T/W of 10:1. SABRE's design goal is 14:1. IE about 40% better than a SoA jet engine. That's poor by rocket standards but an Isp 6x or 8x better than the best rocket engine (while air breathing, otherwise it's mere as good as the best Isp of known rocket engines) makes a big difference in building an LV.
Quote
I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.
Not really.
Firstlyif you've got air breathing your Isp goes up a lot compared to rockets and you can use wings. SABRESkylon is designed to use both. 

Secondly launch puts the airframe at maximum temperature for a very limited period of time. 10s of secs at maximum AB Mach before it goes to full rocket mode and a few 10s of minutes on re entry at most.

Cruise is like re-entry but lasting for hours requiring continual dumping of enormous quantities of heat from the whole airframe. That lets you use design approaches that won't work for long periods but are perfectly acceptable for the launch/reentry mission.

If you don't understand that difference you need to study a bit more engineering.

BTW HTOL takes a thrust roughly 1/3 (or in extreme cases 1/4) the GTOW. OTOH if you go with VTOL the thrust must exceed the weight by a significant amount or there is no take off at all.

Quote
Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.
There have been many designs put up by SCRamjet proponents over the years. Various proposals attracted substantial funding. X30 got $Bn+.

All had (in hindsight) low TRL's so IRL it was going to be a case of build the vehicle to test the engine. Which, giving the high levels of uncertainty about M5 combustion and flight meant the probable result was that you'd throw the aircraft away and have to start again.
None have built an actual flight vehicle.

SABRESkylon is designed to avoid as much uncertainty as possible. The engine was designed (from day one) to be tested on the ground, so when you design the vehicle you already know it's going to work. The question then becomes how well can you design the vehicle to deliver that potential.

I was referring to China's hypersonic weapons development program & the U.S. response to it.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: TrevorMonty on 08/02/2015 07:59 PM
I'm confident you're reading too much into this. It would be a different matter if Alan Bond said "we're switching to TSTO" publicly, but here you have their Director of Corporate Development sound just exactly like someone in that role should: he's being broadly supportive of the AFRL statement - i.e. their recent partner who they may hope to work with again (read $$$$ that could help further the Skylon project).

How would we know there not still actively working with the USAF, it may not be something the USAF wish broadcasting.

I personally feel if the USAF want a hypersonic vehicle of some type then REL are their best best to achieve this.

According to their press release regarding the results of the CRADA it is an ongoing relationship as it states :

"Reaction Engines Ltd. and AFRL are now formulating plans for continued collaboration on the SABRE engine; the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system, testing of SABRE engine components and exploration of defence applications for Reaction Engines’ heat exchanger technologies."

Note it states "SABRE derived" regarding what they want to put in a vehicle.
The heat exchanger technology has a lot of ground based and probably marine applications. REL are expecting to make a lot of money from this technology alone.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 08/03/2015 04:19 AM

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.


yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed.

I have wondered if a hypersonic vehicle that could go nearly as fast as a scramjet would make a useful test bed.  At the moment the engine+vehicle is lost after use and that has to be quite expensive.   lets say a sabre(lite)-based vehicle can only go up to M5 - perhaps it is still useful to be able to test a scramjet in real flight conditions at that speed.   You can do your test flight, recover the engine, look at what might be wrong with it and then go out and do the test again.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/03/2015 05:17 PM

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.


yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed.
Only if  you're looking for funds for a SCRamjet research programme.  :(

If you want an M5 cruise engine REL did the conceptual work for this under the EU LAPCAT programme.

The simple fact is that REL's work eliminates the need for a SCRamjet in the first place.

Do you want a vehicle that can run at M5 or do you want a SCRamjet research programme?

REL could provide the engine for the former, but have no interest in the latter.  :(
I was referring to China's hypersonic weapons development program & the U.S. response to it.
The thing that needs an ICBM to get it up to speed and then glides to target?

Like the Bell BOMI concepts of the 1950s?

Or the "Evader" MIRV tests of the 1970's & 80's? Which (had they been deployed) would have been nuclear armed by default.

AFAIK the only people "worried" about this are people whose presentation ends "And that's why we need an X $Bn hypersonics research programme to investigate what we can do about it."

On a personal note you should take a look at how this site quotes stuff. Most of what  you quoted in my post was not needed.  :(
I have wondered if a hypersonic vehicle that could go nearly as fast as a scramjet would make a useful test bed.  At the moment the engine+vehicle is lost after use and that has to be quite expensive.   lets say a sabre(lite)-based vehicle can only go up to M5 - perhaps it is still useful to be able to test a scramjet in real flight conditions at that speed.   You can do your test flight, recover the engine, look at what might be wrong with it and then go out and do the test again.
Alternatively use the SABRE derived vehicle instead of the SCRamjet?

This is the problem for REL and the USAF.

HX technology does not help you make a working SCRamjet, which is the dream the vast majority of us researchers have been pursuing.

It eliminates the need for such an engine at all, if you can live with running on LH2.

OTOH the LAPCAT study noted that a design could support a 20 000 Km range without aerial refueling, so (in principal) eliminating the need for the fueling infrastructure that was a big part of SR71 operations.

REL engine concepts don't work if you
a) Can't accept LH2 as the fuel, because  you just don't like it.  b) Need a very long range in a small form factor.

Outside of this their engine concepts can deliver long range and high speed, potentially from bases solely inside CONUS.

That really just leaves long range missiles, not as a test bed but as the sole use for a SCRamjet running on something other than LH2, provided the spec needs a range that far exceeds a pure rocket and the speed exceeds what a subsonic combustion ramjet can do (except that in the 1960's the French built ramjets that did hit M5 and some US test missiles went that fast due to stuck fuel valves).

You'd have to write a very carefully worded missile procurement spec so that the prime candidate for propulsion was an SCRamjet.  :(

US Hypersonics researchers have proved remarkably adept at getting the US Govt to spend several $Bn over the decades with remarkably little to show for it.  :(
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: banjo on 08/03/2015 09:23 PM
john i meant only exactly what i wrote.  "maybe the AFRL have in mind......"   
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/04/2015 06:46 AM
john i meant only exactly what i wrote.  "maybe the AFRL have in mind......"
Then  I would say it's a pretty doubtful notion, given the history of SCRamjet development.  :(

The question again is why?

The rule of thumb (not sure if anyone's tried it with SCRamjets) is ramjets can have a 3 Mach operating range so maybe you can get a vehicle to M8?
Or perhaps you don't like LH2 for a cruise vehicle. Unless you run on straight JP4 you're back to the separate fuel supply chain the SR71 had which was one of the reasons the USAF gave for retiring it in the first place. 

People may think a non LH2 fueled vehicle will be "stealthier" as it will be smaller but most of the features of low radar cross section that worked on an SR71 would scale up quite well.

But whatever the size of such a vehicle it will always be a huge target on any kind of infra red sensor.   :(

Someone sees a  UFO on IR traveling at M5 on a straight and level course at  FL800. They are not thinking "meteorite."
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/05/2015 06:45 PM
This is not directly Skylon/SABRE related, but since LAPCAT and Ramjets have been discussed recently:

"Concorde Mark 2: Airbus files plans for new supersonic jet - New jet could cut flight time from London to New York to just one hour"

http://www.telegraph.co.uk/finance/newsbysector/industry/engineering/11782446/Concorde-Mark-2-Airbus-files-plans-for-new-supersonic-jet.html

Animations here:
https://www.youtube.com/watch?v=0dyrbRGkVKI
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Crispy on 08/05/2015 06:58 PM
Already a thread in this forum
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 08/05/2015 07:57 PM
I have just finished reading the latest article in Aviation Week focusing on the Sabre demonstrator engine.

It's interesting to note the comments from both AFRL and Sam Hutchison director of corporate development at Reaction Engines. AFRL state that the Sabre's original target, a single-stage-to-orbit space vehicle remains technically "very risky as a first application," but he go's on to say "Sabre may provide some unique advantages in more manageable two-stage-to-orbit Configurations." Sam Hutchison states  it might be the best approach to demonstrate the technology by taking it one step at a time.

Could this be a step change in Reaction Engines thinking in going for a full blown Skylon Demonstrator, and they now think that's just "a bridge to far"

Might a demonstrator be built  just to prove Sabre up to Mach 5 prior to change over to normal rocket operations be best, the vehicle could be built on a much simpler and smaller  airframe and the return re-entry temperatures would be considerably lower. Once confidence had been achieved it might be possible to modify the demonstrator to achieve crossover to rocket power using a small internal Lox tank to test this, it only needs to operate for a short time so re-entry temperatures will again be  considerably lower than de-orbit temperatures.

I know Sabre can be fully tested at ground level, but to go straight to a flight model Skylon will be a massive risk, no one should  underestimate the complexities involved in this.

In the meantime (to make the financial backers happy) it seems that there are many other  potential aerospace applications beyond just the precooler concept that is the heart of Sabre. This could prove to be a massive income earner for Reaction Engines giving the company the income to create a world-beater in Skylon.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 08/05/2015 10:35 PM
@Hankelow8
Yes, this point was mentioned 2 pages back. Why did an REL person say this.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: AnalogMan on 08/13/2015 12:09 PM
Came across this recent NASA Ames conference paper on Skylon that I thought might be of interest to followers of this thread.

Skylon Aerodynamics and SABRE Plumes
20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference
6-9 July 2015, Glasgow, Scotland, United Kingdom


Abstract:
An independent partial assessment is provided of the technical viability of the Skylon aerospace plane concept, developed by Reaction Engines Limited (REL). The objectives are to verify REL’s engineering estimates of airframe aerodynamics during powered flight and to assess the impact of Synergetic Air-Breathing Rocket Engine (SABRE) plumes on the aft fuselage. Pressure lift and drag coefficients derived from simulations conducted with Euler equations for unpowered flight compare very well with those REL computed with engineering methods. The REL coefficients for powered flight are increasingly less acceptable as the freestream Mach number is increased beyond 8.5, because the engineering estimates did not account for the increasing favorable (in terms of drag and lift coefficients) effect of underexpanded rocket engine plumes on the aft fuselage. At Mach numbers greater than 8.5, the thermal environment around the aft fuselage is a known unknown−a potential design and/or performance risk issue. The adverse effects of shock waves on the aft fuselage and plume-induced flow separation are other potential risks. The development of an operational reusable launcher from the Skylon concept necessitates the judicious use of a combination of engineering methods, advanced methods based on required physics or analytical fidelity, test data, and independent assessments

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150015818.pdf (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150015818.pdf)

[Copy also attached]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/13/2015 07:39 PM
Came across this recent NASA Ames conference paper on Skylon that I thought might be of interest to followers of this thread.

Skylon Aerodynamics and SABRE Plumes
20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference
6-9 July 2015, Glasgow, Scotland, United Kingdom


http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150015818.pdf (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150015818.pdf)

[Copy also attached]
Interesting report.

Note this suggest REL have been in contact with the NASA team for years before this came out.

Obvious points.

NASA's analysis is that REL figures for lift and drag are conservative and underestimate how good the design is.

While quite a detailed CFD it assumes pefect gas effects, which is very isleading at these temperatures and pressures. Typicially air at this temp dissociates into atoms and there is some ionization.

I'd suggest it sound quite positive within the limits of what's being simulated and how it's being simulated.

It's a good reminder there are still substantial unknowns to the design, some of which will be quite subtle, although the report points out fuselage heating by the engine plumes is a known unknown, and this works starts to quantify it.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: t43562 on 08/14/2015 02:28 PM
This looks slightly alarming at Mach 12:

https://lh3.googleusercontent.com/UPElrgfWT-BGhP_sXkswAhG09EMvb829njzzXAPWoik=w1130-h826-no

Can the silicon carbide take it? Could it be actively cooled? Hmm.. I suppose re-entry can't be all that cool but can it compare with this?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hanelyp on 08/14/2015 03:05 PM
This looks slightly alarming at Mach 12:

https://lh3.googleusercontent.com/UPElrgfWT-BGhP_sXkswAhG09EMvb829njzzXAPWoik=w1130-h826-no

Can the silicon carbide take it? Could it be actively cooled? Hmm.. I suppose re-entry can't be all that cool but can it compare with this?
Hard to tell how bad that is without a temperature scale or indication of thermal flux.  The exhaust flow is well expanded by the time it impinges on the after-body.  Heat flow to the skin from this flow should be a small fraction of what the combustion chamber and exhaust nozzle need to deal with.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: chipguy on 08/14/2015 04:34 PM

NASA's analysis is that REL figures for lift and drag are conservative and underestimate how good the design is.


I think if you look more closely you'll find that REL figures were conservative at some speeds and optimistic
at others. Another important take away is the thermal flux on the tail is considerable and probably higher
than REL was counting on. Addressing it may cut into margin reserve for mass growth.

However, on the whole the paper represents an important independent assessment of their vehicle concept
and its general agreement with REL's claims should enhance their credibility.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: antiquark on 08/14/2015 04:46 PM
This looks slightly alarming at Mach 12:

https://lh3.googleusercontent.com/UPElrgfWT-BGhP_sXkswAhG09EMvb829njzzXAPWoik=w1130-h826-no

Can the silicon carbide take it? Could it be actively cooled? Hmm.. I suppose re-entry can't be all that cool but can it compare with this?
Hard to tell how bad that is without a temperature scale or indication of thermal flux.  The exhaust flow is well expanded by the time it impinges on the after-body.  Heat flow to the skin from this flow should be a small fraction of what the combustion chamber and exhaust nozzle need to deal with.

In the article they say "there are regions where static temperatures are roughly 8-16 times greater than the freestream temperature."  However I don't know how to fill in the blanks to arrive at an actual temperature value.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Alpha_Centauri on 08/14/2015 08:43 PM
State aid: [European] Commission approves £50 million UK support for the research and development of an innovative space launcher engine.

http://europa.eu/rapid/press-release_IP-15-5495_en.htm

How nice of them.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: 93143 on 08/14/2015 09:00 PM
At Mach 12, Skylon C1 was at about 62 km, implying an atmospheric pressure of about 15 Pa and a freestream temperature of something like 240 K.  At Mach 17, it was at around 71 km, implying 4 Pa and 215 K.  Real gas effects tend to result in lower stagnation temperatures (and higher stagnation densities) than one would calculate from the ideal gas law.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/14/2015 09:16 PM
It is curious that the authors didn't take the next step and calculate temps on structures. They're clearly aware that this could be the undoing of Skylon - or the retirement of a critical known risk. In the Takeaway section they state: "If the aft fuselage heating owing to nacelle plumes is an issue that cannot be addressed with appropriate structures and materials, then the overall design of Skylon needs to be modified." By which they appear to mean moving the engines aft (and closer to the HOTOL problems.)

They also make a suggestion I don't really follow: Use Skylon as stage 1 in a TSTO system, launching the second stage from the payload bay at ~7 km/s. But wouldn't plume heating be already high at this speed?

The TSTO comment is curiously consistent with the message from USAF/AFRL, so it makes you wonder if there is some connection.
________
For those new to the forum, this was discussed a little three years ago: http://forum.nasaspaceflight.com/index.php?topic=24621.msg943964#msg943964
http://forum.nasaspaceflight.com/index.php?topic=24621.msg945702#msg945702
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/14/2015 10:43 PM
Could the plume impingement be mitigated by switching to having a single large expansion ratio nozzle (400:1)   in each SABRE rather than four 120:1 nozzles so that the plumes aren't so  under expanded at high mach and using the airbreathing  nozzle area for thrust augmenting altitude compensation at low mach?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/14/2015 11:30 PM
The use of altitude compensating Expansion/Deflection nozzles should help also.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Citizen Wolf on 08/15/2015 12:36 AM
As Adrianwyard has nicely reminded us, this topic of plume expansion heating the skylon fuselage was queried on the 1st skylon thread back in 2012. The discussion doesn't seem to have gone any further on the thread and I certainly forgot all about it. But one would have thought that REL has considered this issue. At least I would have hoped they did. There has been no hint of any design modifications to the basic skylon shape nor repositioning of the SABRE engines.

And then the apparently odd comments from the AFRL labs and an REL employee (Sam Hutchison) about using SABRE as a TSTO when the whole original concept was for a SSTO.

I guess there's a lot we still don't know yet.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/15/2015 09:51 AM
The use of altitude compensating Expansion/Deflection nozzles should help also.

It's only an expansion deflection nozzle in airbreathing mode, in rocket mode it's a 120:1 expansion ratio bell nozzle. Either way an E-D nozzle will still become under expanded once it hits it's critical pressure and the plume will grow.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pippin on 08/15/2015 10:42 AM

Hard to tell how bad that is without a temperature scale or indication of thermal flux.  The exhaust flow is well expanded by the time it impinges on the after-body.  Heat flow to the skin from this flow should be a small fraction of what the combustion chamber and exhaust nozzle need to deal with.
I wouldn't be so sure. All the heat flow is in the boundary shock wave and their indications of more than 10 times the free stream temperature... However the final gas model will be (they do give compensation estimates for real gas), this is massive, we are talking about a kelvin-scale here!

They will probably have to cool the whole body aft of the wing, I doubt you can passively cool this without adding a lot of mass.

This essentially means there's a significant chance the whole airframe concept is not feasible. It's the kind of risks you run into when designing all-new stuff and venturing into unknown unknowns with a lot of elements in your design.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/15/2015 03:51 PM
Assuming plume heating is indeed a problem with D1.5a there's no reason to assume it can't be addressed with relatively simple airframe changes. For example, widening the wing span, moving nozzles further aft, etc.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/15/2015 04:01 PM
The use of altitude compensating Expansion/Deflection nozzles should help also.

It's only an expansion deflection nozzle in airbreathing mode, in rocket mode it's a 120:1 expansion ratio bell nozzle. Either way an E-D nozzle will still become under expanded once it hits it's critical pressure and the plume will grow.

Hmmm, I think your saying the E-D benefit occurs it lower altitudes and so is if no help here; that makes sense.

But the nozzle doesn't know if SABRE is in air-breathing or rocket mode, right? Maybe you simply meant earlier in flight when you said 'It's only an expansion deflection nozzle in airbreathing'?

The exhaust from the bypass burners (air-breathing mode) will affect the plume, but that's turned off by the time we're at the problematic speed & altitude/pressure. 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/15/2015 04:56 PM
The use of altitude compensating Expansion/Deflection nozzles should help also.

It's only an expansion deflection nozzle in airbreathing mode, in rocket mode it's a 120:1 expansion ratio bell nozzle. Either way an E-D nozzle will still become under expanded once it hits it's critical pressure and the plume will grow.

Hmmm, I think your saying the E-D benefit occurs it lower altitudes and so is if no help here; that makes sense.

But the nozzle doesn't know if SABRE is in air-breathing or rocket mode, right? Maybe you simply meant earlier in flight when you said 'It's only an expansion deflection nozzle in airbreathing'?

The exhaust from the bypass burners (air-breathing mode) will affect the plume, but that's turned off by the time we're at the problematic speed & altitude/pressure. 

Not quite. The SABRE 4 cycle works by separating the rocket combustion chamber from the airbreathing combustion chamber allowing a high pressure rocket chamber (170 bar) and a low pressure airbreathing chamber ( 12 bar but can be from 6 bar to 20 bar depending on implementation). Each rocket  nozzle consists of a single rocket chamber surrounded  by 3 ( or more depending on implementation) airbreathing chambers, they share a rocket nozzle by having a 30:1 ratio inner nozzle after the rocket chamber throat and then a closable throat fed by the airbreathing chambers followed by a nozzle extension that takes the rocket expansion ratio to 120:1. The upshot being that in airbreathing mode the nozzle acts an E-D nozzle but in rocket mode the airbreathing throat closes and the rocket sees a conventional bell nozzle ( although they are designed to work concurrently to allow for a smooth transition).
My suggestion was to  move to a single large area ratio nozzle and use the airbreathing throat to do TAN as altitude compensation. My second suggestion is to crank the delta wing to increase the wingspan, my third is to consider alternate fuels as the SABRE 4 should allow the rocket mode to work on different fuels to the airbreathing mode and gelled hydrogen could be used for the airbreathing mode, together fuel volume could be slashed creating  a smaller tail.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/15/2015 05:05 PM
I wouldn't be so sure. All the heat flow is in the boundary shock wave and their indications of more than 10 times the free stream temperature... However the final gas model will be (they do give compensation estimates for real gas), this is massive, we are talking about a kelvin-scale here!
You're missing a few points.

Firstly the vast bulk of that exhaust will be in the plume. A very small part of it's mass flow will be hitting the aft fuselage.

Secondly this is a point simulation and Skylon is a on launch trajectory. It's outside air pressure is continually falling. That means the plume is growing but also the plume density is falling, lowering the energy of the gas that will hit the aft fuselage.

Being a point simulation you'd miss the integration of temperature involved. You've also missed that a large part of the body is at a much lower temperature and therefor that heat could be moved by a heat pipe arrangement. Such systems were looked at for the Shuttle wing but never flown.

Like the XS 1 you have to ask how long does the fuselage have to sustain that temperature. On a M5 cruise vehicle that's hours, but the whole trajectory for Skylon is 10-20min tops.
Quote
They will probably have to cool the whole body aft of the wing, I doubt you can passively cool this without adding a lot of mass.
The report is not detailed enough to make that assumption.
Quote
This essentially means there's a significant chance the whole airframe concept is not feasible. It's the kind of risks you run into when designing all-new stuff and venturing into unknown unknowns with a lot of elements in your design.
Depends on your assessment of how much unknown you're dealing with.

We already know the Shuttle can survive reentry from these kinds of temperatures. No their TPS would not be the preferred option, but an existence proof for survival in horizontal landing from orbital velocity is quite encouraging.

OTOH we didn't know you couldn't build even a reasonably large 2nd stage VTOL stage to survive reentry until someone actually tried it and found they couldn't make it work.

BTW doing a CFD for this size of model takes a lot of computer time, even today. Other posters can probably put some numbers on how long a 6-8 million point model takes to run.

It's a tribute to how far Skylon's design has been matured by REL that they had a CAD model to supply to NASA for this work. I doubt NASA would have looked doing this study a decade ago, given this is a non US vehicle that is not already flying.

Moving to real gas chemistry multiplies that amount of time, so operating at this level of detail is good enough for a (relatively) quick look at the problems.

I will note a few points about the work in general.

1) The Nacelle is fully  closed at anything above M5.5.
2) Likewise ramjet flow (and any burner induced drag) ends when the nacelle closes
3) They use a SSME nozzle, but IIRC that's 1:77, not 1:100
4) It's not an E/D, although above M5.5 I'm not sure there would be much difference.
5) Nozzle form is important. Hempsell alluded to this in a Space Show appearance. A NATO report pointed out that Russian nozzles are differently designed and less prone to flow separation. I'm not sure if the British use the Russian or the Western approach.
6)It's not a "turbo ramjet," that's basically the J58 on an SR71, and a very different thermal
cycle.  IIRC Bill Escher's taxonomy described it as a "Deeply pre-cooled air turbo rocket."

Work like this establishes boundaries for further work, narrowing the risk space. It also shows how subtle the problems can be with a design and puts some boundaries on how serious they are.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/15/2015 05:24 PM
Just for reference, the System 2 material can take a maximum of 1470K and the expected maximum temp it should see was 1100K.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/15/2015 05:25 PM
The use of altitude compensating Expansion/Deflection nozzles should help also.

It's only an expansion deflection nozzle in airbreathing mode, in rocket mode it's a 120:1 expansion ratio bell nozzle. Either way an E-D nozzle will still become under expanded once it hits it's critical pressure and the plume will grow.

Hmmm, I think your saying the E-D benefit occurs it lower altitudes and so is if no help here; that makes sense.

But the nozzle doesn't know if SABRE is in air-breathing or rocket mode, right? Maybe you simply meant earlier in flight when you said 'It's only an expansion deflection nozzle in airbreathing'?

The exhaust from the bypass burners (air-breathing mode) will affect the plume, but that's turned off by the time we're at the problematic speed & altitude/pressure. 

Not quite. The SABRE 4 cycle works by separating the rocket combustion chamber from the airbreathing combustion chamber allowing a high pressure rocket chamber (170 bar) and a low pressure airbreathing chamber ( 12 bar but can be from 6 bar to 20 bar depending on implementation). Each rocket  nozzle consists of a single rocket chamber surrounded  by 3 ( or more depending on implementation) airbreathing chambers, they share a rocket nozzle by having a 30:1 ratio inner nozzle after the rocket chamber throat and then a closable throat fed by the airbreathing chambers followed by a nozzle extension that takes the rocket expansion ratio to 120:1. The upshot being that in airbreathing mode the nozzle acts an E-D nozzle but in rocket mode the airbreathing throat closes and the rocket sees a conventional bell nozzle ( although they are designed to work concurrently to allow for a smooth transition).
My suggestion was to  move to a single large area ratio nozzle and use the airbreathing throat to do TAN as altitude compensation. My second suggestion is to crank the delta wing to increase the wingspan, my third is to consider alternate fuels as the SABRE 4 should allow the rocket mode to work on different fuels to the airbreathing mode and gelled hydrogen could be used for the airbreathing mode, together fuel volume could be slashed creating  a smaller tail.

Apparently I've not been paying attention because I was not aware that the SABRE 4 design - including this new dual-mode combustion chamber arrangement - had been made public! Was this image from a public document? Patent filing? If so, could you post links? Thanks.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: pippin on 08/15/2015 05:55 PM
Firstly the vast bulk of that exhaust will be in the plume. A very small part of it's mass flow will be hitting the aft fuselage.
If you mean that due to the fact that only a certain (angular) section of the overall plume hits the body, that's of course, true. What is this, like 10 degrees or so?
If you mean that the bulk of the exhaust is not in the shock front but heading straight aft you are wrong because it's just the nature of the over expanded flow that most of the actual plume mass will be in the shock front because it gets accelerated outwards by the pressure differential. Only a small part will be heading due aft and if my principles of conservation hold that part should not be relevant because at ambient pressure and probably temperature (see the charts) actually _all_ of the plume's thermal energy will be in the shock front.

And given the fact that there is pretty low ambient pressure and mass flow that overall thermal energy will be pretty close to the same as at the nozzle exit because there's not a lot up there the energy could be transferred to.

So I think it's pretty safe to assume that as long as the aft body is indeed within the shock front the thermal energy of the shock front hitting the body will be the same as the thermal energy at the same angular section of the nozzle exit. Which will be significant but should be somewhat easy to calculate if you know the details of the rocket engine.

Quote
Secondly this is a point simulation and Skylon is a on launch trajectory. It's outside air pressure is continually falling. That means the plume is growing but also the plume density is falling, lowering the energy of the gas that will hit the aft fuselage.
So where exactly is all that energy going in your assumption? I don't think you are right with this.

Quote
Being a point simulation you'd miss the integration of temperature involved. You've also missed that a large part of the body is at a much lower temperature and therefor that heat could be moved by a heat pipe arrangement. Such systems were looked at for the Shuttle wing but never flown.
Yes, that's true. I should have made a more precise statement: you can't just radiatively cool it in place unless you use something like the Shuttle TPS (note: I'm not saying the Shuttle's TPS could sustain it, I don't know the amount of heat transfer it could take, as you already mentioned we are talking about pretty low air pressure up there). Transferring the heat to other parts of the body and using these for radiation cooling or absorbing some of the heat using LH2 might work, I don't know.

I don't think something like the Shuttle TPS can be applied without changing the airframe design, BTW, because it will have completely different drag coefficients and will likely change the aerodynamics a lot.

Quote
Quote
This essentially means there's a significant chance the whole airframe concept is not feasible. It's the kind of risks you run into when designing all-new stuff and venturing into unknown unknowns with a lot of elements in your design.
Depends on your assessment of how much unknown you're dealing with.
Not my assessment but the report's.

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/15/2015 07:04 PM
The use of altitude compensating Expansion/Deflection nozzles should help also.

It's only an expansion deflection nozzle in airbreathing mode, in rocket mode it's a 120:1 expansion ratio bell nozzle. Either way an E-D nozzle will still become under expanded once it hits it's critical pressure and the plume will grow.

Hmmm, I think your saying the E-D benefit occurs it lower altitudes and so is if no help here; that makes sense.

But the nozzle doesn't know if SABRE is in air-breathing or rocket mode, right? Maybe you simply meant earlier in flight when you said 'It's only an expansion deflection nozzle in airbreathing'?

The exhaust from the bypass burners (air-breathing mode) will affect the plume, but that's turned off by the time we're at the problematic speed & altitude/pressure. 

Not quite. The SABRE 4 cycle works by separating the rocket combustion chamber from the airbreathing combustion chamber allowing a high pressure rocket chamber (170 bar) and a low pressure airbreathing chamber ( 12 bar but can be from 6 bar to 20 bar depending on implementation). Each rocket  nozzle consists of a single rocket chamber surrounded  by 3 ( or more depending on implementation) airbreathing chambers, they share a rocket nozzle by having a 30:1 ratio inner nozzle after the rocket chamber throat and then a closable throat fed by the airbreathing chambers followed by a nozzle extension that takes the rocket expansion ratio to 120:1. The upshot being that in airbreathing mode the nozzle acts an E-D nozzle but in rocket mode the airbreathing throat closes and the rocket sees a conventional bell nozzle ( although they are designed to work concurrently to allow for a smooth transition).
My suggestion was to  move to a single large area ratio nozzle and use the airbreathing throat to do TAN as altitude compensation. My second suggestion is to crank the delta wing to increase the wingspan, my third is to consider alternate fuels as the SABRE 4 should allow the rocket mode to work on different fuels to the airbreathing mode and gelled hydrogen could be used for the airbreathing mode, together fuel volume could be slashed creating  a smaller tail.

Apparently I've not been paying attention because I was not aware that the SABRE 4 design - including this new dual-mode combustion chamber arrangement - had been made public! Was this image from a public document? Patent filing? If so, could you post links? Thanks.

Yeah, there were a whole bunch of patents made public in July, among them the heat exchanger frost control patent
(which SABRE 4 no longer uses), the SABRE 3 and SABRE 4  patents and the SABRE 4 nozzle patent. It's probably easiest if you just search back in the thread but this is SABRE 4.
It's interesting in that it is clearly Scimitar derived and the patent is broad enough to cover a SABRE variant with broadly Scimitar performance, save for the subsonic hub fan (see page 23, lines 16-22).

Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/16/2015 11:35 AM
If the work had been done in close collaboration with RE I'd have expected a response, or joint release. Alternately they were aware of it (and how it might affect investment) and this might be why there's been a softening of the response to TSTO suggestions?
And in a company with a better media strategy you'd be right. But REL don't really do media relations.  :(
Quote

It strikes me the plume is mostly going over the top of the craft. Does the simulation assume it will be following the same AoA in this steeper part of the ascent? Is that a reasonable assumption in the higher TWR and Mach phase of the flight?
I'd look a bit closer at those pictures.

I think most of them are plan forms.

BTW AIUI the comment in the 1st para of page 12 is wrong. The NASA calculated l/Cd ratio is betterthan the one REL conservatively estimated. The text does not match the numbers.

I don't think concluding that a TSTO vehicle is the way forward is really something NASA can say, although it sounds like something the USAF would like.

I'd like to see how these results stack up against the one REL got from DLR using their Tau code, which IIRC, does use real gas chemistry.

I will caution that both temperature and time are factors in wheather the vehicle can survive this sort of heating.

Checking the C1 spreadsheet shows that Skylon hits M6.41 45secs after going to full rocket power. It then accelerates to orbital speed over the next 240 secs.

So it has to survive partial immersion in this high temperature fluid for (at most) 4 minutes.

It would seem they need some system to extract the heat from the hot parts of the skin and move it to the colder parts so they can dump it.

Hmm.

Sounds like a kind of heat exchanger to me.

Wherever could REL find someone to design such equipment?

My suggestion was to  move to a single large area ratio nozzle
Judging by the diagram you supplied that's what already happens.
Quote
and use the airbreathing throat to do TAN as altitude compensation.
Assuming the REL E/D works already why would they need to do this? It puts Aerjet's IP in to their critical engine design path.
Quote
My second suggestion is to crank the delta wing to increase the wingspan,
Which gets what?
Quote
my third is to consider alternate fuels as the SABRE 4 should allow the rocket mode to work on different fuels to the airbreathing mode and gelled hydrogen could be used for the airbreathing mode, together fuel volume could be slashed creating  a smaller tail.
Except the SABRE 4 mode already cuts fuel volume needed. In one of their more recent progress reports to the IAS REL stated it's not the LH2 volume that's the problem it's the fuselage needs to be a certain shape and in fact there's a lot of empty  space inside it already.

REL have stated they will sub cool both LH2 and LO2 to below NBP to allow them to operate as no vent tanks on the runway.

You can call it "slush" or "gelled" Hydrogen but the fact remains its a 2 phase mixture of liquids and solids. It's something of a theme of REL's design work that they work very hard not to mix phases. In fact the whole point of the pre cooler is to cool but not to turn  it into a liquid. That is one of the enabling technologies of SABRE. I think the benefits for a 2 phase H2 flow would have to be very  compelling for REL to re-think this. Note that despite it being talked about since at least the mid 60's no vehicle has used it, just as (AFAIK) no engine has used gelled hydrocarbon fuels despite their (potentially) better safety and ability to carry energetic additives.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/16/2015 03:53 PM
If the work had been done in close collaboration with RE I'd have expected a response, or joint release. Alternately they were aware of it (and how it might affect investment) and this might be why there's been a softening of the response to TSTO suggestions?
And in a company with a better media strategy you'd be right. But REL don't really do media relations.  :(
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It strikes me the plume is mostly going over the top of the craft. Does the simulation assume it will be following the same AoA in this steeper part of the ascent? Is that a reasonable assumption in the higher TWR and Mach phase of the flight?
I'd look a bit closer at those pictures.

I think most of them are plan forms.

BTW AIUI the comment in the 1st para of page 12 is wrong. The NASA calculated l/Cd ratio is betterthan the one REL conservatively estimated. The text does not match the numbers.

I don't think concluding that a TSTO vehicle is the way forward is really something NASA can say, although it sounds like something the USAF would like.

I'd like to see how these results stack up against the one REL got from DLR using their Tau code, which IIRC, does use real gas chemistry.

I will caution that both temperature and time are factors in wheather the vehicle can survive this sort of heating.

Checking the C1 spreadsheet shows that Skylon hits M6.41 45secs after going to full rocket power. It then accelerates to orbital speed over the next 240 secs.

So it has to survive partial immersion in this high temperature fluid for (at most) 4 minutes.

It would seem they need some system to extract the heat from the hot parts of the skin and move it to the colder parts so they can dump it.

Hmm.

Sounds like a kind of heat exchanger to me.

Wherever could REL find someone to design such equipment?
Active cooling would probably need hundreds of metres of their inconel tubing running underneath the aeroshell ceramic plus another hydrogen/helium heat exchanger and pump for the system. That's going to add a lot of mass. Hence the suggested mass trades to lower the surface area of the tail that needs it.

My suggestion was to  move to a single large area ratio nozzle
Judging by the diagram you supplied that's what already happens.
Nope, SABRE 4 still has 4 nozzles per nascelle, each with an exit area diameter of 1.4m and a expansion ratio of 120:1 for the rocket mode. My suggestion was that with just a  single nozzle  a diameter of up to 4.7m would fit in the same space and have an expansion ratio of up to 1000:1 or higher.  This would be a mass trade against how much active cooling masses but it would have the effect of shortening the time period when the nozzle is underexpanded dramatically and thus the heat soak that the tail experiences as well as lengthening the nacelle mitigating how much of the tail is exposed to the plume and how much the wing is exposed to  plume-induced flow separation.

and use the airbreathing throat to do TAN as altitude compensation.
Assuming the REL E/D works already why would they need to do this? It puts Aerjet's IP in to their critical engine design path.
REL's nozzle uses E/D for the airbreathing mode but the rocket mode is a pure bell nozzle so an extremely large expansion ratio version of it would need some form of compensation to prevent it being grossly under expanded in hypersonic flight,  my suggestion was purely based on the idea that the airbeathing throat already exists so it would only take a connection to the second fuel delivery system to us it for TAN delivery, I wasn't suggesting using Aerojets IP unless they own the very idea of it. However putting an E/D plug in the rocket nozzle might be an better solution.


My second suggestion is to crank the delta wing to increase the wingspan,
Which gets what?
It moves the nacelles further away from the fuselage trading wing mass for active cooling mass.

my third is to consider alternate fuels as the SABRE 4 should allow the rocket mode to work on different fuels to the airbreathing mode and gelled hydrogen could be used for the airbreathing mode, together fuel volume could be slashed creating  a smaller tail.
Except the SABRE 4 mode already cuts fuel volume needed. In one of their more recent progress reports to the IAS REL stated it's not the LH2 volume that's the problem it's the fuselage needs to be a certain shape and in fact there's a lot of empty  space inside it already.

REL have stated they will sub cool both LH2 and LO2 to below NBP to allow them to operate as no vent tanks on the runway.

You can call it "slush" or "gelled" Hydrogen but the fact remains its a 2 phase mixture of liquids and solids. It's something of a theme of REL's design work that they work very hard not to mix phases. In fact the whole point of the pre cooler is to cool but not to turn  it into a liquid. That is one of the enabling technologies of SABRE. I think the benefits for a 2 phase H2 flow would have to be very  compelling for REL to re-think this. Note that despite it being talked about since at least the mid 60's no vehicle has used it, just as (AFAIK) no engine has used gelled hydrocarbon fuels despite their (potentially) better safety and ability to carry energetic additives.
Slush hydrogen and Gelled hydrogen aren't the same things though, slush is a mush of hydrogen ice and liquid while gelled is a mixture of liquid hydrogen and a frozen second fuel, gelled is clearly easier to make and deal with and has safety and boiloff benefits beyond just fuel density.

The Skylon fuselage is shaped for minimum drag and mass, the report we're discussing suggests that their calculations haven't anticipated the drag correctly with regards rocket plume impingement and we've been discussing the mass effects of trying to mitigate such a heat soak, this suggests that maybe with a new design round taking all this into account the fuselage shape needs to change a little. As such maybe Skylon needs to be shorter.

The 60's argument is ironic considering we're talking about  a SABRE powered SSTO here. Slush hydrogen tankage and pumps were successfully built and tested for NASP and generally liquid ice is used industrially as a coolant so the technology for how to pump and tank slush is more mature than you'd think.
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/16/2015 04:59 PM
How critical is AoA during the latter part of the ascent? At some point the aerodynamic forces become negligible so might you be able to just aim the plume away from structure? (And retain control thanks to the center of mass & pressure being well managed in the Skylon config.) Perhaps even using negative AoA to keep it clear of the vertical stabilizer? Or, as it's a thin moving structure and cooling will be a challenge, move it to the nose - HOTOL style?
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: Hankelow8 on 08/17/2015 09:23 AM
In 2012 The University of Strathclyde carried out a study for an alternate design for the Skylon airframe , CFASTT-1.
It concentrated on the re-entry heating characteristics of the airframe.

In view of the comments regarding rocket exhaust plume issues , it would be interesting to see if this alternate design improves rocket plume flow.


http://strathprints.strath.ac.uk/41933/1/Brown_et_al_Towards_Robust_Aero_Thermodynamic_Predictions_for_Re_Usable_Single_Stage_to_Orbit_Vehicles.pdf
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: adrianwyard on 08/17/2015 08:49 PM
In 2012 The University of Strathclyde carried out a study for an alternate design for the Skylon airframe , CFASTT-1.
It concentrated on the re-entry heating characteristics of the airframe.

In view of the comments regarding rocket exhaust plume issues , it would be interesting to see if this alternate design improves rocket plume flow.


http://strathprints.strath.ac.uk/41933/1/Brown_et_al_Towards_Robust_Aero_Thermodynamic_Predictions_for_Re_Usable_Single_Stage_to_Orbit_Vehicles.pdf

Now you mention it, the CFASTT-1 had nacelle's that angle outwards away from the tail; presumably for aerodynamic reasons rather than heating. To my eye the new V-Tails are no closer to the plume than the single C-1 fin, but it's hard to be sure.

I noticed that the NASA Ames paper specifically states that nozzle gimbaling is not taken into account (p6) but that "the plumes are so under-expanded that it is unlikely this will substantially alleviate the impingement effects" (p15). If that's the case, then perhaps we can guess the CFASTT changes will also be of little benefit heating-wise.

And while we're talking of gimbaling, disregard my post from yesterday; I forgot that with Skylon the nozzles are already pointing down rather than straight back, away from the tail and structure.
 
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: john smith 19 on 08/17/2015 09:39 PM
Active cooling would probably need hundreds of metres of their inconel tubing running underneath the aeroshell ceramic plus another hydrogen/helium heat exchanger and pump for the system. That's going to add a lot of mass.
A few A few hundred meters of this tubing will not weigh that much. bigger issues are likely to the thermal conductivity skin material.
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Hence the suggested mass trades to lower the surface area of the tail that needs it.
Yes lowering the surface area is almost always the way to go.
Quote
Nope, SABRE 4 still has 4 nozzles per nascelle, each with an exit area diameter of 1.4m and a expansion ratio of 120:1 for the rocket mode. My suggestion was that with just a  single nozzle  a diameter of up to 4.7m would fit in the same space and have an expansion ratio of up to 1000:1 or higher.  This would be a mass trade against how much active cooling masses but it would have the effect of shortening the time period when the nozzle is underexpanded dramatically and thus the heat soak that the tail experiences as well as lengthening the nacelle mitigating how much of the tail is exposed to the plume and how much the wing is exposed to  plume-induced flow separation.
I think setting the expansion ratio on any launcher is tricky. Pretty much as soon Skylon hits the nozzles "preferred" altitude it will be passing through that pressure altitude.


and use the airbreathing throat to do TAN as altitude compensation.
my suggestion was purely based on the idea that the airbeathing throat already exists so it would only take a connection to the second fuel delivery system to us it for TAN delivery, I wasn't suggesting using Aerojets IP unless they own the very idea of it.
It's patented.  REL would have to license it.
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It moves the nacelles further away from the fuselage trading wing mass for active cooling mass.
Sounds viable. The other option would be to widen the wings to put the final nozzle location as far back as possible. Again I think this needs a detailed look before major design changes are planned.
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Slush hydrogen and Gelled hydrogen aren't the same things though, slush is a mush of hydrogen ice and liquid while gelled is a mixture of liquid hydrogen and a frozen second fuel, gelled is clearly easier to make and deal with and has safety and boiloff benefits beyond just fuel density.
It's still a 2 phase mixture and this is a design approach REL seem very keen to avoid.
Quote
The Skylon fuselage is shaped for minimum drag and mass, the report we're discussing suggests that their calculations haven't anticipated the drag correctly with regards rocket plume impingement and we've been discussing the mass effects of trying to mitigate such a heat soak, this suggests that maybe with a new design round taking all this into account the fuselage shape needs to change a little. As such maybe Skylon needs to be shorter.
Possibly, but the design trades on HTOL vehicles seem much harder than VTOL systems. What you gain on heat reduction you may loose too much control authority as the weight goes too far back, like HOTOL.
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The 60's argument is ironic considering we're talking about  a SABRE powered SSTO here. Slush hydrogen tankage and pumps were successfully built and tested for NASP
Which one? The original NASP of the early 60's or the later X30 of the late 80's?
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and generally liquid ice is used industrially as a coolant so the technology for how to pump and tank slush is more mature than you'd think.
Where LH2 with either SH2 or mixed with something like Methane I doubt anyone has long term experience on any kind of industrial scale.

Again AFAIK it's not the volume of hte propellant. It's putting it in a body that' big enough and trading the surface area. But there it's plum impingement area Vs propellant burn due to higher drag. [EDIT the different elements you can trade are complex, and it's very doubtful you can improve this item and not make any other factor worse, which I think is the difference between design IRL and design in a textbook.  :( ]
Title: Re: The Reaction Engines Skylon Master Thread (5)
Post by: lkm on 08/17/2015 11:39 PM
Active cooling would probably need hundreds of metres of their inconel tubing running underneath the aeroshell ceramic plus another hydrogen/helium heat exchanger and pump for the system. That's going to add a lot of mass.
A few A few hundred meters of this tubing will not weigh that much. bigger issues are likely to the thermal conductivity skin material.
Well the Skylon D1 was designed to have 2.5mt of payload margin on top of the various built in structural margins so that's what they have to play with, and if they use it all they won't have anything left for the next problem. Perhaps they will need to re-reconsider the skin, Originally, in the very beginning, they planned to use C/SiC  for the Skylon skin which has a higher maximum temperature (1870K) and a lower density but they switched to System 2 as it was thought to be much cheaper to produce even though it increased the skin mass by 25%. Maybe they need C/SiC for the tail. 

Hence the suggested mass trades to lower the surface area of the tail that needs it.
Yes lowering the surface area is almost always the way to go.
Quote
Nope, SABRE 4 still has 4 nozzles per nascelle, each with an exit area diameter of 1.4m and a expansion ratio of 120:1 for the rocket mode. My suggestion was that with just a  single nozzle  a diameter of up to 4.7m would fit in the same space and have an expansion ratio of up to 1000:1 or higher.  This would be a mass trade against how much active cooling masses but it would have the effect of shortening the time period when the nozzle is underexpanded dramatically and thus the heat soak that the tail experiences as well as lengthening the nacelle mitigating how much of the tail is exposed to the plume and how much the wing is exposed to  plume-induced flow separation.
I think setting the expansion ratio on any launcher is tricky. Pretty much as soon Skylon hits the nozzles "preferred" altitude it will be passing through that pressure altitude.
Absolutely but if you could move the preferred altitude from say 30km to 90km for an acceptable mass/drag  increase then the time