Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 419582 times)

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #100 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 1000C 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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Moe Grills

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #101 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.

Offline Citizen Wolf

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #102 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.
The only thing I can be sure of is that I can't be sure of anything.

Offline Moe Grills

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #103 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.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #104 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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #105 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  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #106 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?
« Last Edit: 02/25/2015 08:45 PM by adrianwyard »

Offline Citizen Wolf

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #107 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. 
« Last Edit: 02/25/2015 09:40 PM by Citizen Wolf »
The only thing I can be sure of is that I can't be sure of anything.

Online Hankelow8

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #108 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.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #109 on: 02/25/2015 11:12 PM »
LH is a requirement for Skylon because of the hypersonic operating environment where they need around 1000C 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 350C (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.
« Last Edit: 02/26/2015 12:14 AM by 93143 »

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #110 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.
« Last Edit: 02/26/2015 12:20 AM by adrianwyard »

Offline SICA Design

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #111 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

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #112 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.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline SICA Design

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #113 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.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #114 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?
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #115 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 ...
« Last Edit: 02/26/2015 02:20 PM by t43562 »

Offline aga

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #116 on: 02/26/2015 02:41 PM »
what existing aircraft uses lh2?
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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #117 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.   :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline NovaSilisko

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #118 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...

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #119 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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

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