Author Topic: The Reaction Engines Skylon/SABRE Master Thread (7)  (Read 353274 times)

Offline Star One

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The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #60 on: 01/09/2019 11:06 pm »
Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

No, REL is no longer pushing Skylon, SpaceX is pushing Starship ... big difference.

This is a mis-representation of REL’s long term position.

I'm happy to re-evaluate my current evaluation if you can show me that the current management are still pushing Skylon.

Can you provide anything to show that this isn’t still their long term goal, outside of your own assumptions?
« Last Edit: 01/09/2019 11:06 pm by Star One »

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #61 on: 01/09/2019 11:17 pm »
I'm also interested in what handling characteristics you believe JS19 "made up". The static stability and engine out capability are documented design features.

But that sometimes has little bearing on final product features. [...] Would the final model have 'static stability'? Not necessarily. Would it be capable of engine out engines on the extreme ends of the wings, at all phases of flight? Extraordinary claims require extraordinary evidence.[...]
We live in a real world with real engineering trade offs.

so you were being disingenuous when you claimed the documented design features were something JS19 had made up.
 

Offline Dao Angkan

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #62 on: 01/09/2019 11:22 pm »
Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

No, REL is no longer pushing Skylon, SpaceX is pushing Starship ... big difference.

This is a mis-representation of RELís long term position.

I'm happy to re-evaluate my current evaluation if you can show me that the current management are still pushing Skylon.

Can you provide anything to show that this isnít still their long term goal, outside of your own assumptions?

Sure, I'll make an indepth and thoroughly sourced post tomorrow. I'll trust that you will do the same yourself.

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #63 on: 01/10/2019 12:11 am »

Extraordinary claims require extraordinary evidence

For static stability, the canards need a stretched-out lower-intensity coefficient of lift response to angle of attack than the wings CL AoA response. Like a swept wing compared to a straight wing. Like Skylon's swept canards.

Your claim that this well understood aspect of aerodynamics wouldn't work is extraordinary, where is your extraordinary proof? Merely saying something might crop up  during development doesn't cut it, definitely not to the point that you can claim it's something JS19 made up.



Quote
The fastest way to empty a propellant tank for a rocket propelled vehicle is to actually burn it through the engine.
Now, that *is* an extraordinary claim.

Perhaps you mean on a launchpad, burning it is quicker than pumping it out.

The quickest way is to unzip the tank with detcord. Neither Skylon's skin or tanks are structural. I don't know what the abort scenario propellant dumping plans are, but I strongly suspect they are not that drastic, but still meet the desired criteria.

Quote
Skylon still lives in the paper world where everything can be solved by writing another paragraph about a design feature that can solve everything. Or a spurious claim on an internet forum by a Skylon evangelist.
As opposed to your spurious claims that it just wouldn't, couldn't work?

I don't expect Skylon to be built to the current spec (and not just because the spec is stated to be "good" only until engine data is bavailable). Changes would be made if it were developed, and some snags may require rethinks, but I strongly doubt they would be in those documented design features that you claimed JS19 "made up"
« Last Edit: 01/10/2019 12:19 am by JCRM »

Offline Gliderflyer

Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #64 on: 01/10/2019 12:25 am »
Quote
The fastest way to empty a propellant tank for a rocket propelled vehicle is to actually burn it through the engine.
Now, that *is* an extraordinary claim.

Perhaps you mean on a launchpad, burning it is quicker than pumping it out.

The quickest way is to unzip the tank with detcord. Neither Skylon's skin or tanks are structural. I don't know what the abort scenario propellant dumping plans are, but I strongly suspect they are not that drastic, but still meet the desired criteria.
It is actually pretty easy to rapidly dump propellant through a separate valve. The dump valve doesn't have to fight the back-pressure from a running engine, so you can get a much higher flow rate. It is far from a spaceship, but here is an example from the EZ-Rocket (original link on this page: https://web.archive.org/web/20030202164818fw_/http://www.xcor.com:80/video-ezrocket.html)
I tried it at home

Offline CameronD

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #65 on: 01/10/2019 01:31 am »
It is actually pretty easy to rapidly dump propellant through a separate valve. The dump valve doesn't have to fight the back-pressure from a running engine, so you can get a much higher flow rate. It is far from a spaceship, but here is an example from the EZ-Rocket (original link on this page: https://web.archive.org/web/20030202164818fw_/http://www.xcor.com:80/video-ezrocket.html)

That took, what, 25 seconds?  Hardly "rapid"..  AIUI, the biggest issue dumping propellant through a valve in flight is stopping the vent opening from freezing shut.
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Lars-J

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #66 on: 01/10/2019 01:39 am »

Extraordinary claims require extraordinary evidence

For static stability, the canards need a stretched-out lower-intensity coefficient of lift response to angle of attack than the wings CL AoA response. Like a swept wing compared to a straight wing. Like Skylon's swept canards.

Your claim that this well understood aspect of aerodynamics wouldn't work is extraordinary, where is your extraordinary proof? Merely saying something might crop up  during development doesn't cut it, definitely not to the point that you can claim it's something JS19 made up.

My point - is that flying at mach 5+ is where things get really difficult (not that they were trivial to begin with), so you don't get to just throw out phrases like "Sears Haack shape" and declaring it solved. So what happens if that canard placement turns out to be problematic? Whoops!

Quote
The fastest way to empty a propellant tank for a rocket propelled vehicle is to actually burn it through the engine.
Now, that *is* an extraordinary claim.

Perhaps you mean on a launchpad, burning it is quicker than pumping it out.

The quickest way is to unzip the tank with detcord. Neither Skylon's skin or tanks are structural. I don't know what the abort scenario propellant dumping plans are, but I strongly suspect they are not that drastic, but still meet the desired criteria.
Of course there are ways, but none of them are trivial nor instant. And surely a detcord should be ruled out immediately, if the point was that an engine out scenario was survivable.  ;D

Quote
Skylon still lives in the paper world where everything can be solved by writing another paragraph about a design feature that can solve everything. Or a spurious claim on an internet forum by a Skylon evangelist.
As opposed to your spurious claims that it just wouldn't, couldn't work?

I don't think I've ever written that. But feel free to correct me. My point has been that it will simply more difficult than what Skylon proponents claim. I don't expect it to succeed, but it does not break the laws of physics.

I don't expect Skylon to be built to the current spec (and not just because the spec is stated to be "good" only until engine data is bavailable). Changes would be made if it were developed, and some snags may require rethinks, but I strongly doubt they would be in those documented design features that you claimed JS19 "made up"

He comes up with stuff all the time. Just in the last page he suggested that a Skylon could be manually controlled without a computer. I doubt you will see that in a RE booklet: 
I'd guess that it could be piloted by a human directly linked to the flying controls. Again unlike the Shuttle, where APU failure meant the computers, the controls (and probably the crew) would all die.
« Last Edit: 01/10/2019 01:49 am by Lars-J »

Offline Gliderflyer

Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #67 on: 01/10/2019 01:45 am »
It is actually pretty easy to rapidly dump propellant through a separate valve. The dump valve doesn't have to fight the back-pressure from a running engine, so you can get a much higher flow rate. It is far from a spaceship, but here is an example from the EZ-Rocket (original link on this page: https://web.archive.org/web/20030202164818fw_/http://www.xcor.com:80/video-ezrocket.html)

That took, what, 25 seconds?  Hardly "rapid"..  AIUI, the biggest issue dumping propellant through a valve in flight is stopping the vent opening from freezing shut.
It all depends on the definition of "rapid". It was much faster than the normal ~2 minute engine burn, which is the point of a separate dump valve. The important part is making sure it is gone before landing. It is unlikely that the vent opening would freeze shut. Ice can only form where there is water, and the flowing propellant does a good job of keeping the opening clear (although "gentle" boiloff venting will form harmless ice tunnels extending out a few inches from cryo tank vents). A bigger issue is the valve mechanism seizing, but that is a solved problem for cryo valves.
I tried it at home

Offline john smith 19

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #68 on: 01/10/2019 06:26 am »
It all depends on the definition of "rapid". It was much faster than the normal ~2 minute engine burn, which is the point of a separate dump valve. The important part is making sure it is gone before landing. It is unlikely that the vent opening would freeze shut. Ice can only form where there is water, and the flowing propellant does a good job of keeping the opening clear (although "gentle" boiloff venting will form harmless ice tunnels extending out a few inches from cryo tank vents). A bigger issue is the valve mechanism seizing, but that is a solved problem for cryo valves.
AIUI, the biggest issue dumping propellant through a valve in flight is stopping the vent opening from freezing shut.
It seems what you understand are the design problems and the actual design problems are different things.

Are there any other things you "Understand" are problems?
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Offline john smith 19

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #69 on: 01/10/2019 06:59 am »
My point - is that flying at mach 5+ is where things get really difficult (not that they were trivial to begin with), so you don't get to just throw out phrases like "Sears Haack shape" and declaring it solved. So what happens if that canard placement turns out to be problematic? Whoops!
That was CameronD's point.

I'm not sure you are making any point at all, beyond "There will things that will be difficult" An insight that's right up there with "Water is wet."  :(

SABRESkylon starts from a point that it will use the best available knowledge to design a system that will do the job without needing breakthroughs in the underlying science, rather than trying to (for example) turn something that's not designed for reuse into something that is.

Quote from: Lars-J
Of course there are ways, but none of them are trivial nor instant. And surely a detcord should be ruled out immediately, if the point was that an engine out scenario was survivable.  ;D

Quote
Skylon still lives in the paper world where everything can be solved by writing another paragraph about a design feature that can solve everything. Or a spurious claim on an internet forum by a Skylon evangelist.
As opposed to your spurious claims that it just wouldn't, couldn't work?

I don't think I've ever written that. But feel free to correct me.
But it seems to sum up your views pretty accurately, does it not?
 You don't know why Skylon can't work, you just do.

Here's my thought from a previous thread
Quote
If your argument that SABRE/Skylon will not work is basically "It won't work because I say it won't" that's not a debate, that's an opinion :(

The odds on bet of such an opinion holder is they will retain their opinion till the day Skylons are sold commercially, whereupon they will go off and opine that something else won't work.  :(

I tend to refer to such people as "Doubters." They are not skeptics and logic and reason won't work is merely a waste of time.

It's a valuable lesson in all walks of life.  :(


Quote from: Lars-J
My point has been that it will simply more difficult than what Skylon proponents claim. I don't expect it to succeed, but it does not break the laws of physics.
As opposed to say making an upper stage that can survive re-entry without sacrificing so much propellant and being so damaged in the process that it's unusable afterward?

That does seem to need several breakthroughs in the physics (and chemistry) of materials and control systems as to make it impossible. 

The difference between "easy" and "easier" is quite important. As is  the difference between possible and impossible.

No one who's familiar with SABRESkylon has ever said it will be easy, but winged re-entry has already been demonstrated by 3 vehicles (Buran, Shuttle and the X37b). The fact some of the best design teams in the industry couldn't find a way to build a large re-entry vehicle that did not need them speaks volumes for how very tough this problem is.

I don't expect Skylon to be built to the current spec (and not just because the spec is stated to be "good" only until engine data is bavailable). Changes would be made if it were developed, and some snags may require rethinks, but I strongly doubt they would be in those documented design features that you claimed JS19 "made up"
Quote from: Lars-J
He comes up with stuff all the time. Just in the last page he suggested that a Skylon could be manually controlled without a computer. I doubt you will see that in a RE booklet: 
I'd guess that it could be piloted by a human directly linked to the flying controls. Again unlike the Shuttle, where APU failure meant the computers, the controls (and probably the crew) would all die.
REL have stated the current Skylon design is trimmable, so it can be statically balanced.

Given Skylon re-enters with empty main tanks (minimal sloshing) and has most of its point masses (engines and payload bay) close to its CoM (unlike putting large point masses at the back, where they'd tend to flip the structure) and needing no substantial propellant masses to create potentially large slosh loads its control problem should be relatively simple.
« Last Edit: 01/12/2019 12:44 pm by john smith 19 »
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Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #70 on: 01/10/2019 09:02 am »

Of course there are ways

So you were being disingenuous when you stated "The fastest way to empty a propellant tank for a rocket propelled vehicle is to actually burn it through the engine. "

Quote
, but none of them are trivial nor instant.
no, but they wouldn't need to be.
Quote
And surely a detcord should be ruled out immediately, if the point was that an engine out scenario was survivable.
why do you think it wouldn't be survivable by the payload?

I would, instead, rule out detcord on the basis that such a rapid emptying would be unnecessary, and also because it would lead to high refurbishment costs. I mentioned it not as the most practical method, but in counterpoint to your false claim that burning it through the engines was fastest.



Quote
He comes up with stuff all the time. Just in the last page he suggested that a Skylon could be manually controlled without a computer. I doubt you will see that in a RE booklet:
I see no problem with that statement. It's a natural consequence of the design that that could happen, and it illustrates what it means to have static stability. I don't think  anyone was proposing that it would be a configuration that would be used now. (Although I have nothing to prove there was never a plan for test pilots to fly Skylon airframes to develop the control software, back when computers were so much less than they are today)

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #71 on: 01/10/2019 09:20 am »

Come on guys, Skylon is dead
Sure, I'll make an indepth and thoroughly sourced post tomorrow. I'll trust that you will do the same yourself.
I look forward to this. Indepth and thoroughly sourced information about the internal machinations at Reaction Engines are hard to come by.

I suspect what you'll actually come back with is REL distancing themselves from SABRE only being usable with Skylon and demonstrating that a 20 year 20 billion investment isn't needed before an investor can hope for a RoI (Such as Mark Thomas's interview last year where he expects a launch vehicle would be two stage in the first instance)

Offline Star One

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #72 on: 01/10/2019 11:59 am »

Come on guys, Skylon is dead
Sure, I'll make an indepth and thoroughly sourced post tomorrow. I'll trust that you will do the same yourself.
I look forward to this. Indepth and thoroughly sourced information about the internal machinations at Reaction Engines are hard to come by.

I suspect what you'll actually come back with is REL distancing themselves from SABRE only being usable with Skylon and demonstrating that a 20 year 20 billion investment isn't needed before an investor can hope for a RoI (Such as Mark Thomas's interview last year where he expects a launch vehicle would be two stage in the first instance)

My issue with their original post was the idea that REL have given up on Skylon. They may not be rushing towards it just now but there has been no indication it doesn’t remain as a longer term goal for them.

Offline edzieba

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #73 on: 01/10/2019 02:12 pm »
As per Mark Wood's talk at the IET last year, for spacecraft applications RE's target for spacecraft SABRE applications is a TSTO vehicle, not an SSTO Skylon. Non-space applications (i.e. hypersonic flight) are expected to be arrive first.

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #74 on: 01/10/2019 03:12 pm »
As per Mark Wood's talk at the IET last year, for spacecraft applications RE's target for spacecraft SABRE applications is a TSTO vehicle, not an SSTO Skylon. Non-space applications (i.e. hypersonic flight) are expected to be arrive first.
That's not quite how I remember you describing it:
RE are continuing with Skylon as the 'reference design'/use-case for SABRE, but are actively working with other companies to use [SABRE?] both for spaceflight and for hypersonics. The SEI design got its own slide too, in place of Skylon as an example of a launch application, though not explicitly named.
Which remains congruent with "a launch vehicle would be two stage in the first instance" while maintaining SSTO as a long term goal
« Last Edit: 01/10/2019 03:17 pm by JCRM »

Offline edzieba

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #75 on: 01/10/2019 03:39 pm »
The SSTO Skylon is a "we'd like to make it" whilst TSTO is a "we think this is something that is viable to make".

Offline ZachF

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #76 on: 01/10/2019 03:47 pm »
It is actually pretty easy to rapidly dump propellant through a separate valve. The dump valve doesn't have to fight the back-pressure from a running engine, so you can get a much higher flow rate. It is far from a spaceship, but here is an example from the EZ-Rocket (original link on this page: https://web.archive.org/web/20030202164818fw_/http://www.xcor.com:80/video-ezrocket.html)

That took, what, 25 seconds?  Hardly "rapid"..  AIUI, the biggest issue dumping propellant through a valve in flight is stopping the vent opening from freezing shut.
It all depends on the definition of "rapid". It was much faster than the normal ~2 minute engine burn, which is the point of a separate dump valve. The important part is making sure it is gone before landing. It is unlikely that the vent opening would freeze shut. Ice can only form where there is water, and the flowing propellant does a good job of keeping the opening clear (although "gentle" boiloff venting will form harmless ice tunnels extending out a few inches from cryo tank vents). A bigger issue is the valve mechanism seizing, but that is a solved problem for cryo valves.

Rapidly dumping huge amounts of something as reactive as hydrogen into the air safely is no trivial task.
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Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #77 on: 01/10/2019 04:31 pm »
The SSTO Skylon is a "we'd like to make it" whilst TSTO is a "we think this is something that is viable to".
get funded.

Offline Lar

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #78 on: 01/10/2019 08:43 pm »
Let's all be excellent to each other, ok? If you think I might be talking about you, I am.
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Offline john smith 19

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Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #79 on: 01/10/2019 09:31 pm »
Rapidly dumping huge amounts of something as reactive as hydrogen into the air safely is no trivial task.
Perhaps you should consider that 150 tonnes of Skylon's mass is LOX, which is much heavier and a lot easier to dump.

Regarding LH2 it's low temperature means the problem is not vaporizing LH2, it's stopping it vaporizing. It's very low density as a gas means it will disperse very quickly.

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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