The Reaction Engines Skylon/SABRE Master Thread (6)

[Lar]

Fanboi is a deliberately insulting term. People shouldn't use it. Try to keep the thread about Skylon instead of attacking the tech of all comers. If someone else went off topic, don't follow.

[su27k]

Note stage recovery R&D cost is included in the estimate. If you skipped the $1B cost of reusability research, then the low risk design of F9 v1.0 only costs $400M to develop, less than 1/3 of the cost to develop a comparable airliner.

However since an airliner has to carry untrained passengers it's hard to say how much of that cost is down to having wings and how much to testing it well enough to ensuring it's safety is at a level that modern airline passengers will accept.

Well you wanted to compare BFR development cost with A380....

After they went to v1.1 then v1.2, it's no longer low risk design or novel way of putting aerospace-rated components together, it's something else all together. It's the only Kerosene TSTO that can launch significant mass to GTO, no one else comes even close.

Perhaps you should further qualify that last sentence with "that's been designed in the last 20 years in its weight class without the backing of a government."

Not at all, no qualification needed. There is no other Kerosene TSTO that can send 6t to GTO that is built by humans, none.

[Chris Bergin]

This is a very weak thread for something that has shown very little by way of making advances over the years.

Our tolerance for low value posts will never be high. The posts that follow will be on topic and of value or it's getting locked and staying locked until there's some actual news.

[edzieba]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

[john smith 19]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

I'd also ask "After the precooler, what is the next most difficult item to get ready for flight?

[JCRM]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

I'd also ask "After the precooler, what is the next most difficult item to get ready for flight?

I think that will be the other heat exchangers and turbo machinery working together, which hopefully will be covered in helium loop tests next year.

My question would be "given the progress being made, all we are hearing about recently is SABRE. Is Skylon, or a similar SSTO craft, still the goal?"

[t43562]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

Could you ask about SABRE spin-offs? I heard something about using heat exchangers in the motor industry (electric cars)?
I think it's relevant is to find out if Reaction Engines can find ways to sustain itself.

Another question I have is about how their helium pump is getting along.

[Patchouli]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

Could you ask about SABRE spin-offs? I heard something about using heat exchangers in the motor industry (electric cars)?
I think it's relevant is to find out if Reaction Engines can find ways to sustain itself.

Another question I have is about how their helium pump is getting along.

Gas cooled reactors using a Brayton cycle turbine could benefit greatly from work done on  SABRE.

[speedevil]

Gas cooled reactors using a Brayton cycle turbine could benefit greatly from work done on  SABRE.

Was I misremembering, or was it also a promising alternative to conventional cycles for fossil fuel driven plants, with modestly higher efficiencies?
Which seems likely a much larger market in the near term than fission.

[john smith 19]

Could you ask about SABRE spin-offs? I heard something about using heat exchangers in the motor industry (electric cars)?
I think it's relevant is to find out if Reaction Engines can find ways to sustain itself.

Another question I have is about how their helium pump is getting along.

Gas cooled reactors using a Brayton cycle turbine could benefit greatly from work done on  SABRE.

Well there's a fair bit of prior art in the Helium cooled nuclear reactor field already.  Starting with the Dragon
in Winfrith
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/05/120/5120516.pdf

Using gas bearings developed by Brown Boveri of Baden. The big ones ran at 9000 RPM, the smaller ones 24000RPM on tilting pad racking more than  33 000hrs each.

Later circulators were designed for other sites.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/05/120/5120516.pdf

So there is a certain amount of existing work to build on. On the upside these systems operating times are measured in years. OTOH none of them is "flight weight."

[john smith 19]

To claw things back on topic; I'll remind everyone that Mark Wood will be giving a lecture at the IET in London next Friday, and so far only John Smith has gotten back to me with questions to be asked in the generous Q&A session.

Just remembered that Spaceworks Enterprises Inc did analysis of a couple USAFRL designs for SABRE powered first stage TSTO vehicles. A smaller vehicle of 5Klbs from CCAFS and a larger one of 20Kbl

I would be interested to  hear their views on the assumptions underlying the SEI analyses, such as switching to air breathing at Mach 4.4, or that the reusable US has a mass fraction of 15.94% for a gross weight of both stages together of 509tonnes, and of course how would Skylon compare flying from CCAFS? IE Longitude 28.5deg.

[JCRM]

Just remembered that Spaceworks Enterprises Inc did analysis of a couple USAFRL designs for SABRE powered first stage TSTO vehicles. [...] how would Skylon compare flying from CCAFS? IE Longitude 28.5deg.

The review looked at a partially reusable system putting 5000 lb to 100nmi orbit at 28.5 degrees, and the second fully reusable being able to put 20000 in orbit - I'm going to assume it is the same altitude.

From the Skylon D1 manual, for a 30 degree launch site it is expected to be able to orbit 15.6 tonnes (34 klb) at 100 nmi (185 km) with it's GTOM of 325 tonnes.

The USAF vehicle is heavier than it need be as the upper stage was RP based - the Spaceworks study indicated that if such a system were to be used it would use LH2, but an LH2 upper stage was outside of the scope of the study.

[Archibald]

Could you ask about SABRE spin-offs? I heard something about using heat exchangers in the motor industry (electric cars)?
I think it's relevant is to find out if Reaction Engines can find ways to sustain itself.

Another question I have is about how their helium pump is getting along.

Gas cooled reactors using a Brayton cycle turbine could benefit greatly from work done on  SABRE.

Well there's a fair bit of prior art in the Helium called nuclear reactor field already.  Starting with the Dragon
in Winfrith
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/05/120/5120516.pdf

Using gas bearings developed by Brown Boveri of Baden. The big ones ran at 9000 RPM, the smaller ones 24000RPM on tilting pad racking more than  33 000hrs each.

Later circulators were designed for other sites.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/05/120/5120516.pdf

So there is a certain amount of existing work to build on. On the upside these systems operating times are measured in years. OTOH none of them is "flight wait."

Alan Bond first worked on British rocketry (Blue Streak) then when the program was shamelessly shut down by the governement in 1972, he went to the nuclear industry for a decade, working on gas cooled and helium cooled reactors. Then from 1982 the HOTOL / Skylon saga started and never stopped since then.

So REL working on nuclear powerplants heat exchangers, notably gas-cooled, would be a kind of return to the roots of Skylon and HOTOL.

[john smith 19]

Alan Bond first worked on British rocketry (Blue Streak) then when the program was shamelessly shut down by the governement in 1972, he went to the nuclear industry for a decade, working on gas cooled and helium cooled reactors. Then from 1982 the HOTOL / Skylon saga started and never stopped since then.

So REL working on nuclear powerplants heat exchangers, notably gas-cooled, would be a kind of return to the roots of Skylon and HOTOL.

You missed out his period working on the military applications of reentry vehicle design.

Actually a background in engines, structures and reentry vehicle physics is pretty much what you need to build a complete launch vehicle (or at least understand the problems of designing one).
However what was lacking was the sense of mass changes with winged vehicles, which HOTOL provided.

[john smith 19]

The review looked at a partially reusable system putting 5000 lb to 100nmi orbit at 28.5 degrees, and the second fully reusable being able to put 20000 in orbit - I'm going to assume it is the same altitude.

From the Skylon D1 manual, for a 30 degree launch site it is expected to be able to orbit 15.6 tonnes (34 klb) at 100 nmi (185 km) with it's GTOM of 325 tonnes.

The USAF vehicle is heavier than it need be as the upper stage was RP based - the Spaceworks study indicated that if such a system were to be used it would use LH2, but an LH2 upper stage was outside of the scope of the study.

Well that covers how well Skylon would cover the problem but my real interest (which I think only REL can answer) was their opinion on wheather (and which) assumptions SEI made were generous to REL or conservative.
I'm thinking (for example) of the T/O thrust being 70% of GTOW, whereas for aircraft it's normally nearer 30%, while the Teledyne Ryan Firebee II supersonic drone achieved M2 cruise with a thrust 50% of GTOW.
Or the landing gear mass allowance (3.98% of GTOW) when even the XB70 could manage c2% of GTOW (using late 50's/early 60's design methods). and REL spent significant effort in designing a light weight  but fully effective brake and cooling system for Skylon to cope with a launch abort at maximum runway speed.

[JCRM]

in 1972, [Alan Bond] went to the nuclear industry for a decade, working on gas cooled and helium cooled reactors. Then from 1982 the HOTOL / Skylon saga started and never stopped since then.

So REL working on nuclear powerplants heat exchangers, notably gas-cooled, would be a kind of return to the roots of Skylon and HOTOL.

This work also exposed him to dealing with plasma interacting with materials (magnetic confinement is all very good in theory) and System 2

The review looked at a partially reusable system putting 5000 lb to 100nmi orbit at 28.5 degrees, and the second fully reusable being able to put 20000 in orbit - I'm going to assume it is the same altitude.

From the Skylon D1 manual, for a 30 degree launch site it is expected to be able to orbit 15.6 tonnes (34 klb) at 100 nmi (185 km) with it's GTOM of 325 tonnes.

The USAF vehicle is heavier than it need be as the upper stage was RP based - the Spaceworks study indicated that if such a system were to be used it would use LH2, but an LH2 upper stage was outside of the scope of the study.

Well that covers how well Skylon would cover the problem but my real interest (which I think only REL can answer) was their opinion on wheather (and which) assumptions SEI made were generous to REL or conservative.

That's why I only attempted the throwaway question at the end. I'd be interested to hear REL's assessment of the designs - or differences of opinion - but wouldn't expect them to put too much effort into doing so as skylon serves as a reference design until actual performance of SABRE is available.

I'm thinking (for example) of the T/O thrust being 70% of GTOW, whereas for aircraft it's normally nearer 30%, while the Teledyne Ryan Firebee II supersonic drone achieved M2 cruise with a thrust 50% of GTOW.

the high thrust/weight is dictated by the desire to use existing runways (to reduce infrastructure cost, and maintain a high take off speed (to minimise wing size). The difference in optimal transition speed is proabably due to staging, but the difference in T/W might also contribute.

Or the landing gear mass allowance (3.98% of GTOW) when even the XB70 could manage c2% of GTOW (using late 50's/early 60's design methods). and REL spent significant effort in designing a light weight  but fully effective brake and cooling system for Skylon to cope with a launch abort at maximum runway speed.

I would guess the landing gear sizing is due to the procedural model used, and should further investigations be made I would expect optimised landing gear to be a factor. As it was an exercise in risk reduction from the Skylon design I wouldn't expect novel water cooled brakes to be included.

[Archibald]

There is also Daedalus, the interstellar fusion probe of 1977. Bond was part of that project.

[john smith 19]

This work also exposed him to dealing with plasma interacting with materials (magnetic confinement is all very good in theory) and System 2

Good point.

That's why I only attxmpted the throwaway question at the end. I'd be interested to hear REL's assessment of the designs - or differences of opinion - but wouldn't expect them to put too much effort into doing so as skylon serves as a reference design until actual performance of SABRE is available.

I do hope not. That is an extraordinarily short sighted view of such a report if you're looking at the USAF as a potential funding source, which I presume REL are hoping for. 
Reports like this can have very long term consequences on how a concept is pursued. A similar report (on plug nozzles Vs E/D nozzles) from Notre Dame in the late 60's effectively ended E/D research until REL decided to take another look.
Assumptions matter. If they are unreasonable they should be challenged.

I would guess the landing gear sizing is due to the procedural model used, and should further investigations be made I would expect optimised landing gear to be a factor. As it was an exercise in risk reduction from the Skylon design I wouldn't expect novel water cooled brakes to be included.

AFAIK all "risk reduction" schemes come down to
1) Build an expendable US
2) Build a smaller 2nd winged vehicle.
IOW double (actually more than double) the development budget. 

With 1 you have to build a new US because AFAIK no stage, designed to operate on its side, exists and the stresses are pretty different (Shuttle side stepped this problem by launching vertically). To keep the costs down you either go with more or less OTS SRBs or (radically) skip the guidance and make the booster do the precision pointing with the booster (which is exactly how Black Arrow did it. The "Waxwing" solid 3rd stage contributed a lot of the delta V).
You now either block build them (with the up front costs that entails) or you build on demand.

Option 2 still leaves you with all the issues of reentry, but now you have a denser, heavier vehicle and you'll probably use some heritage TPS which will inherit all the TPS repair issues from its lineage.

IMHO the best "Risk reduction" is to build a test engine of the minimum size needed that a pair of them, when attached to a scaled down Skylon, can make and return from orbit.
Then build the thing and fly it. It wouldn't matter if its payload was no more than a camera phone that snapped pictures of the night sky then the vehicle flipped over and took some snaps of the Earth.

The fact is no airframe mfg anywhere  has experience of this structural technology (despite it's historical use dating back to rigid airships and the Wellington bomber) and it seems that while people don't believe it can work (despite what actual mathematics says can be done) it will be very hard to convince anyone it is actually possible. 

That said a flight test vehicle that operated just above transistion, whether or not it's airframe matched that of Skylon, would AIUI be the first reusable hypersonic test since the X15.

That alone would be a significant asset, if it had adequate provision for test sensors.

[edzieba]

With 1 you have to build a new US because AFAIK no stage, designed to operate on its side, exists and the stresses are pretty different (Shuttle side stepped this problem by launching vertically).

Orientation doesn't really matter squat as long as Skylon can deploy it in microgravity and above the majority of the atmosphere, which as far as I am aware was always intended to be the case (think deployment like an STS IUS rather than like the D-21).

As for the airframe: it's a pity Project SUNTAN was so long ago, almost all the extensive work on it is likely now lost, and the engineers who worked on it have largely passed away. Same fuel, similar flight regime (despite the different engines) and even a remarkable similar planform.

[john smith 19]

Orientation doesn't really matter squat as long as Skylon can deploy it in microgravity and above the majority of the atmosphere, which as far as I am aware was always intended to be the case (think deployment like an STS IUS rather than like the D-21).

It does if the stage was originally designed to launch vertically. The weight distribution is very different. You may recall that SX pulled out of doing a horizontal rocket for Stratolaunch. AIUI the assumption has been "It'll just be a scaled down F9 on its side." It wasn't.

As for the airframe: it's a pity Project SUNTAN was so long ago, almost all the extensive work on it is likely now lost, and the engineers who worked on it have largely passed away. Same fuel, similar flight regime (despite the different engines) and even a remarkable similar planform.

It may or may not exist but it would definitely be a major issue of "ITAR contamination" to REL. Something REL are working to avoid.

AFAIK the aircraft structure (designed to cruise at M2.5, so quite fast, but not as fast as the A12) was planned to be basically the worlds biggest dewar IE vacuum insulation. I presume this is because LH2 is usually carried using "Vacuum Jacketed Line"

The issue with any vacuum based system is
a) Creating a large vacuum system. b)Keeping it vacuum tight.
Vacuum failure causes a massive increase in thermal conductivity, leading to flash boiling. The difficult of building, and maintaining such a system is probably a good part of why Suntan was cancelled.

Skylon "keeps it simple" by splitting the tanks from the skin (so they only have to handle the cryogenic effects) and using a layer of low density closed cell foam to keep the air temp at the top of the layer above the dew point of the surrounding air. The tanks themselves are (IIRC) still baselined as conventional Aluminum rather than LiAl, as this has a very long operational history in cryogenic road tankers. I think they will retain this since it will be the low cost option and it's one less issue to be concerned about.

In some ways the SABRESkylon design was developed on similar principles to the A12, in the sense that it is advanced only where necessary to carry out its mission.