Author Topic: The Reaction Engines Skylon/SABRE Master Thread (6)  (Read 437876 times)

Offline Paul451

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #240 on: 10/07/2016 06:02 pm »
spaff billions of quid

Not sure it that violates the site's language policy or not.

Offline momerathe

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #241 on: 10/11/2016 01:26 pm »
I admit nothing <_< .

Anyway, let me ask the thread a different question. REL have always put forth the idea that they are an engine company first and foremost. So, let's take them at their word: let's suppose than in 6-7 years time they've got a working 1/4 scale SABRE engine, that does everything they say it will, and anyone (export restrictions notwithstanding) can come along and buy one for their rocket.

What are the applications?

* TSTO first stage. Possibly using the cluster of engines mentioned in the Aviation Week article. Sound plausible - at least AFRL think it is. Who's going to build it? And will it be cost competitive?

* Space tourism. Assuming you think space tourism is a viable business model (I have my doubts), this seems like an easy target. A suborbital, RTLS, HTHL vehicle with decent crossrange has a load of safety and handling advantages. Having a proven, working engine is significant de-risking for potential investors.

* Military applications. Though I can't help thinking that this is more of an opportunity to milk the US Govt for development money.

Anything else? Smallsat launcher, perhaps?
thermodynamics will get you in the end

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #242 on: 10/11/2016 04:59 pm »

Anyway, let me ask the thread a different question. REL have always put forth the idea that they are an engine company first and foremost. So, let's take them at their word: let's suppose than in 6-7 years time they've got a working 1/4 scale SABRE engine, that does everything they say it will, and anyone (export restrictions notwithstanding) can come along and buy one for their rocket.

What are the applications?
If it's for sale then this would not be a 1/4 scale "model" it would be an actual SABRE engine with a design thrust 1/4 that of the planned unit for Skylon.

And since it's designed to run the whole runway-to-orbit mission how about building a SSTO HTO launcher around it?
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Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #243 on: 10/12/2016 11:15 pm »
I nearly made a similar comment myself John Smith. Why not just string a load of these units together and do a Skylon-like vehicle anyway? Maybe they would be alongside each other under a blended wing type belly? I don't know. Perhaps it would provide a reduction in complexity and make maintenance somewhat easier?  Anyway I decided against the comment since I figured there was a reason for the original '4 nozzle' design which I presume balances redundancy with efficiency etc. and using several of these single nozzle units presumably would result in more duplication of components. If so, might such duplication actually render the Skylon/SSTO concept less achievable - or certainly less payload?

Offline momerathe

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #244 on: 10/13/2016 09:42 am »
If it's for sale then this would not be a 1/4 scale "model" it would be an actual SABRE engine with a design thrust 1/4 that of the planned unit for Skylon.

That's what I meant. Apologies for clumsy phrasing.

Quote
And since it's designed to run the whole runway-to-orbit mission how about building a SSTO HTO launcher around it?

Sure. What size launcher, though? Like flymetothemoon suggests, you could cluster them up and build a full size skylon, but consider the following quote from the Aviation Week article:

Quote
Reaction CEO Mark Thomas believes the move to a smaller demonstrator is serendipitous. “It is now more affordable, more rapid to execute and will potentially find its first application quicker,

That implies to me that they're NOT thinking of a full-sized skylon as a first application.
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Offline Paul451

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #245 on: 10/13/2016 09:00 pm »
Just wanted to emphasise this quote:

(Via momerathe)
Quote
Reaction CEO Mark Thomas believes the move to a smaller demonstrator is serendipitous. “It is now more affordable, more rapid to execute and will potentially find its first application quicker..."

Cheaper, faster, easier to find the first paying client.

{sigh}

Can I remind everyone of the number of times this concept was raised by people on this thread (or its five predecessors) only to be shouted down by the small core of amazing peoples who insist that Skylon and SABRE can't be scaled down; that TSTO is stupid and wrong; that any interim development could only cost more money; that there's no possible advantage to any alternative to the path directly to Skylon and that anyone who says otherwise is merely ignorant.

After six longs threads, can we just stop with the shrill knee-jerk defence now? Can we accept that there are interim steps that are quicker, cheaper and easier than Skylon, and that REL is perfectly happily following that path? And not just "willing to do what the client wants, if the client is stupid enough to go in that stupid direction", but that it's actually better than a direct path.

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #246 on: 10/14/2016 05:11 am »
Just wanted to emphasise this quote:

(Via momerathe)
Quote
Reaction CEO Mark Thomas believes the move to a smaller demonstrator is serendipitous. “It is now more affordable, more rapid to execute and will potentially find its first application quicker..."

Cheaper, faster, easier to find the first paying client.

{sigh}

Can I remind everyone of the number of times this concept was raised by people on this thread (or its five predecessors) only to be shouted down by the small core of amazing peoples who insist that Skylon and SABRE can't be scaled down; that TSTO is stupid and wrong; that any interim development could only cost more money; that there's no possible advantage to any alternative to the path directly to Skylon and that anyone who says otherwise is merely ignorant.

After six longs threads, can we just stop with the shrill knee-jerk defence now? Can we accept that there are interim steps that are quicker, cheaper and easier than Skylon, and that REL is perfectly happily following that path? And not just "willing to do what the client wants, if the client is stupid enough to go in that stupid direction", but that it's actually better than a direct path.

No, I think not because it makes sense to go for the big plan and do it the most efficient way if you can.  What's happened thus far is the result of setbacks which we wish had not happened.   Should circumstances change for the better, I'm sure we will all be happy without the distracting side-shows.

Offline Asteroza

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #247 on: 10/14/2016 07:08 am »
Considering the avoidance up to now of building 1/4 sub-Skylon sized SABRE engines due to the time/cost of designing the LH2 turbine, how much of system/weight penalty would you take by using multiple subscale LH2 turbines to feed a full scale SABRE?

Apparently there is a lot of duplicated components in a full scale SABRE, usually in groups of four, correct? Is it really as simple as saying use 4 subscale turbines and eat the weight increase in piping/manifolds?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #248 on: 10/14/2016 01:35 pm »
Considering the avoidance up to now of building 1/4 sub-Skylon sized SABRE engines due to the time/cost of designing the LH2 turbine, how much of system/weight penalty would you take by using multiple subscale LH2 turbines to feed a full scale SABRE?
Actually both the LOX and LH2 sides of the SABRE use 2 turbines.
Quote
Apparently there is a lot of duplicated components in a full scale SABRE, usually in groups of four, correct? Is it really as simple as saying use 4 subscale turbines and eat the weight increase in piping/manifolds?
No, parts are implemented as multiple sub units. The ramjets seems to use 4, but the pre-cooler operates as as single unit, while both LOX and LH2 turbines are a pair. OTOH IIRC the full size pre cooler uses 21 modules (which have already been tested).

So the question would be where do you draw the line?

The  reason REL have resisted a scaled down design was (according to Hempsell, when he posted on thread, that a scaled down LH2 turbopump at full chamber pressure would basically swallow aŁ350m budget without delivering a design you could use in the full size engine. So why bother?

However the SABRE 4 cycle appears to be able to de-couple the air breathing chamber pressure from the rocket chamber pressure much more, making the LH2 turbo pump more transferable to larger designs.
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Offline knowles2

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #249 on: 10/17/2016 03:26 am »
May be they are now just planning to buy a off the shelf LH2 turbopump, like the use on the Vulcain engine?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #250 on: 10/17/2016 11:41 am »
May be they are now just planning to buy a off the shelf LH2 turbopump, like the use on the Vulcain engine?
There's no such thing as an OTS LH2 turbopump. 

Offhand I'd say the Vulcain TP is the wrong size and is powered by a gas generator burning O2/H2. SABRE uses a Helium loop. The blade design will be substantially different for a start because of the difference in properties between hot He and a mixture of hot GH2 and steam that Vulcains GG produces.
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Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #251 on: 10/17/2016 04:21 pm »
May be they are now just planning to buy a off the shelf LH2 turbopump, like the use on the Vulcain engine?
There's no such thing as an OTS LH2 turbopump.

Yes there is and you in fact point out there are BUT point out they may need modification :)

Quote
Offhand I'd say the Vulcain TP is the wrong size and is powered by a gas generator burning O2/H2. SABRE uses a Helium loop. The blade design will be substantially different for a start because of the difference in properties between hot He and a mixture of hot GH2 and steam that Vulcains GG produces.

RL-10 maybe? I'm going to guess that dealing with hot helium will be at least a little easier to deal with than hot hydrogen and oxygen.

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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #252 on: 10/19/2016 03:03 am »
Yes there is and you in fact point out there are BUT point out they may need modification :)
Fair point. I was in a hurry at the time. I should have said OTS if powered by a similar gas generator.  But by the time you've redesigned for the different drive gas you might as well have designed the whole thing from scratch and avoided having to be compatible with any existing parts.
Quote
RL-10 maybe? I'm going to guess that dealing with hot helium will be at least a little easier to deal with than hot hydrogen and oxygen.
I think REL are saying the new test engine will be about 40 Klb of thrust, so I think the RL10 TP is still a bit small. Wasn't the largest RL10 variant about 22-25 Klbs ?
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Klebiano

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #253 on: 10/19/2016 04:11 am »
Yes there is and you in fact point out there are BUT point out they may need modification :)
Fair point. I was in a hurry at the time. I should have said OTS if powered by a similar gas generator.  But by the time you've redesigned for the different drive gas you might as well have designed the whole thing from scratch and avoided having to be compatible with any existing parts.
Quote
RL-10 maybe? I'm going to guess that dealing with hot helium will be at least a little easier to deal with than hot hydrogen and oxygen.
I think REL are saying the new test engine will be about 40 Klb of thrust, so I think the RL10 TP is still a bit small. Wasn't the largest RL10 variant about 22-25 Klbs ?

The Vinci engine, under development of Airbus Safran has the right specification. 40lbf.

Offline hkultala

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #254 on: 10/19/2016 06:25 am »
Yes there is and you in fact point out there are BUT point out they may need modification :)
Fair point. I was in a hurry at the time. I should have said OTS if powered by a similar gas generator.  But by the time you've redesigned for the different drive gas you might as well have designed the whole thing from scratch and avoided having to be compatible with any existing parts.
Quote
RL-10 maybe? I'm going to guess that dealing with hot helium will be at least a little easier to deal with than hot hydrogen and oxygen.
I think REL are saying the new test engine will be about 40 Klb of thrust, so I think the RL10 TP is still a bit small. Wasn't the largest RL10 variant about 22-25 Klbs ?

The Vinci engine, under development of Airbus Safran has the right specification. 40lbf.

There are many other things in "specification" than just size. Vinci is expander cycle, it's turbopumps are running on hot hydrogen warmed up in the nozzle. SABRE turmopump is running on hot helium.

He is about 2 times heavier than H2 which means the turbine should propably be quite different.

Also the output pressures might be totally different (but I don't know if they are)
« Last Edit: 10/19/2016 07:48 am by hkultala »

Offline Katana

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #255 on: 10/24/2016 09:07 am »
2x heavier molecular weight could be balanced by differences of temperature and pressure.

Bigger problem: He gas compressor which is not included in standard turbopump units.
« Last Edit: 10/24/2016 09:31 am by Katana »

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #256 on: 10/29/2016 07:24 am »
This talk at the American Astronautical Society on reusability is a bit long but the bit from theman from DARPA at 1:49:29 is of interest, I think. where he says "rockets are fine, I don't need airbreathing"

http://livestream.com/accounts/563450/events/6533675/videos/140271208

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #257 on: 10/29/2016 09:13 pm »
This talk at the American Astronautical Society on reusability is a bit long but the bit from theman from DARPA at 1:49:29 is of interest, I think. where he says "rockets are fine, I don't need airbreathing"

http://livestream.com/accounts/563450/events/6533675/videos/140271208
The man from DARPA  is Jess Sponable, who ran the DC-X project and is running the XS-1 project.

The REL work is linked into the USARFRL

What's more interesting is he talked about a resin for composites usable up to 750 degrees. If that's degrees Celsius this is a major achievement. 750F (398c) would still be very impressive.

« Last Edit: 10/29/2016 09:15 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #258 on: 11/03/2016 07:32 am »
This talk at the American Astronautical Society on reusability is a bit long but the bit from theman from DARPA at 1:49:29 is of interest, I think. where he says "rockets are fine, I don't need airbreathing"

http://livestream.com/accounts/563450/events/6533675/videos/140271208
The man from DARPA  is Jess Sponable, who ran the DC-X project and is running the XS-1 project.

The REL work is linked into the USARFRL

What's more interesting is he talked about a resin for composites usable up to 750 degrees. If that's degrees Celsius this is a major achievement. 750F (398c) would still be very impressive.

Indeed, I understand the difference between DARPA and the USAF but it is going to be interesting if XS-1 turns into a great success because then why pursue a risky and expensive new idea, having basically covered most of what you wanted with somewhat more conventional methods?  I mean what motivation would the USAF have for not "simply" going for XS-1 if it ends up being nearly what they need?   

He also made a specific point about not needing airbreathing and I though that  the idea must have been put to him and rejected.  That is not wonderful - he is saying that many other things are priorities first and if that's true for him, why not for everyone?

It is just interesting also in that video to see the attitude of the former Shuttle employees and current competitors to SpaceX. I may be oversensitive but I got the impression that anyone who proposes a different strategy is going to have difficulty proposing it to a crowd like that. They have so much experience and such a strong philosophy of how to do things and deal with uncertainty that they can't abandon them for the philosophy of the new kids.  I used to work for Nokia and their phones had to be usable in sub-zero temperatures with gloves (no capacitive touch screens)  and they had multi-day battery life and were tested to destruction quite extensively.  Almost all of these things seemed very important and they sort of are still but we all prioritised the large ram, screens and fast processors that directly clashed with the ideals of ruggedness and long life.  Most of us seem delighted with the result and would never go back.    So what I mean with this analogy is that very experienced people may be hostile to new ways of doing things and they can be completely right and yet still be missing the main point.

So I do wonder what reception SABRE will have when it is demonstrated.
« Last Edit: 11/03/2016 07:49 am by t43562 »

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #259 on: 11/03/2016 11:38 am »
Indeed, I understand the difference between DARPA and the USAF but it is going to be interesting if XS-1 turns into a great success because then why pursue a risky and expensive new idea, having basically covered most of what you wanted with somewhat more conventional methods?  I mean what motivation would the USAF have for not "simply" going for XS-1 if it ends up being nearly what they need?   
XS-1 is a vehicle to get (eventually) to M10. Only the last of the test flights has to do this and that's nowhere near orbital velocity. AFAIK XS-1 is also an X plane. The next vehicle after it would be operational.

Either way you end up developing 2 stages.
Quote
He also made a specific point about not needing airbreathing and I though that  the idea must have been put to him and rejected.  That is not wonderful - he is saying that many other things are priorities first and if that's true for him, why not for everyone?
Part of the XS-1 baseline is that it needs an existing engine as the concept is viewed as high risk, low funding and short timescale. That means an OTS engine. There are not many of these but there are a few possible candidates.
Quote
So I do wonder what reception SABRE will have when it is demonstrated.
I'm not sure there's any point in worrying about wheather any particular audience will like SABRE or not.

If it meets it's performance goals then people will have to decide if they incorporate that into their plans.  SABRE gives you 2 things normal rockets don't.
1) Airbreathing Isp 6x greater than the highest rocket Isp. That pushes allowable structural mass fraction from 5% to more like 25% of GTOW, easing the design problem for the 2nd stage as well.
2)Air does not just stop carrying LOX it is 80% N2, so the reaction mass put out is actually 4x bigger than it would be if it was pure O2

I'll note you don't need a rocket  T/W to exceed the GTOW of the vehicle if the vehicle is winged so that's not an inherent advantage of SABRE but but the rockets higher T/W ratio is not a guaranteed win over SABRE once you factor in the mass of the LOX and its tankage and structure to carry it.

It would be interesting to find out what T/W a rocket engine would need to have to match SABRE in a HTOL design once the oxidzer mass and tank mass are taken into account.

Otherwise you have a choice.

a) Go VTOL and require your GTOT exceeds GTOW by about 25% regardless of how many stages you have  or
 b) Design a HTOL architecture of how many stages but with a structural mass fraction like a rocket rather than an aircraft, as the 2nd stage will have to be carried by the first.  This is relatively unknown territory.
« Last Edit: 11/03/2016 11:42 am by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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