Author Topic: The Reaction Engines Skylon Master Thread (2)  (Read 592987 times)

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1860 on: 11/26/2013 08:13 PM »
I really believe that self ferry is the way to go. It simplifies the logistics radically and I think an air breathing Skylon in self ferry mode (no LO2 on board and possibly only a part load of LH2, but probably the payload) would take off with much lower thrust, takeoff speed and engine wear during the trip (compared to a launch mission).

How about ferry by airship, and a British airship to boot :)

Cargo cradle underslung a Hybrid Air Vehicles (http://www.hybridairvehicles.com/) heavy-lift vehicle. Modify the inflatable pontoons under the HAV to conform with the Skylon fuselage so that it will sit neatly underneath, protecting it from e.g. ground debris and hail damage and reducing the tendency to weathervane in the wind. Additional protective "skirts" could be dropped from the underside of the HAV.

The company are getting the prototype vehicle they built for the US Army back in bits, and they're anticipating putting it back together to restart UK flights in Q3 2014.

Also, "Thunderbirds Are Go!" MUST be played over loudspeakers as the Skylon is unloaded from the HAV. It's compulsory :D

*LIKE*

Airship transport has been suggested/quoted before here, it possibly even came from Alan Bond. I was a little surprised it hadn't got more coverage here, so well done for pointing it out again. They are offering heavy lift up to 200 tonnes so could certainly cover the job. Seems like a cracking bit of kit and being funded by the good ol' U.S. of A. military. God bless you America ;)
« Last Edit: 11/26/2013 08:14 PM by flymetothemoon »

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1861 on: 11/26/2013 08:45 PM »
I really believe that self ferry is the way to go. It simplifies the logistics radically and I think an air breathing Skylon in self ferry mode (no LO2 on board and possibly only a part load of LH2, but probably the payload) would take off with much lower thrust, takeoff speed and engine wear during the trip (compared to a launch mission).

How about ferry by airship, and a British airship to boot :)

Cargo cradle underslung a Hybrid Air Vehicles (http://www.hybridairvehicles.com/) heavy-lift vehicle. Modify the inflatable pontoons under the HAV to conform with the Skylon fuselage so that it will sit neatly underneath, protecting it from e.g. ground debris and hail damage and reducing the tendency to weathervane in the wind. Additional protective "skirts" could be dropped from the underside of the HAV.

The company are getting the prototype vehicle they built for the US Army back in bits, and they're anticipating putting it back together to restart UK flights in Q3 2014.

Also, "Thunderbirds Are Go!" MUST be played over loudspeakers as the Skylon is unloaded from the HAV. It's compulsory :D

*LIKE*

Airship transport has been suggested/quoted before here, it possibly even came from Alan Bond. I was a little surprised it hadn't got more coverage here, so well done for pointing it out again. They are offering heavy lift up to 200 tonnes so could certainly cover the job. Seems like a cracking bit of kit and being funded by the good ol' U.S. of A. military. God bless you America ;)

Ok lets be SERIOUS here for a moment... Is there ANYONE who hasn't been expecting REL/etc to end up playing TaG or the Theme to FirballXL-5 at SOME point during the test program? Really? I mean does ANYONE think someone could actually RESIST that temptation? Hmmm?

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 93143

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1862 on: 11/26/2013 09:08 PM »
Looking over the pictures of the cycle there is simply no way to NOT run the whole system during any powered portion of the flight. No mechanical compression (and no air bleed into the bypass ducts) means no thrust at low speeds:
http://www.reactionengines.co.uk/sabre_howworks.html

Don't get me wrong; I don't think it's a good idea or anything.

Obviously you'd need the turbomachinery for takeoff and acceleration.  The question is, can you then shut it down and cruise on the ramjets?  It's not like the inlet pressure recovery is good enough to require much in the way of a boost pump, though whether pressure feed is even possible in principle or not may depend heavily on the chosen cruise conditions as well as how much losing the suction from the core changes the intake behaviour...
« Last Edit: 11/26/2013 09:13 PM by 93143 »

Offline Turbomotive

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1863 on: 11/26/2013 11:01 PM »


Ok lets be SERIOUS here for a moment... Is there ANYONE who hasn't been expecting REL/etc to end up playing TaG or the Theme to FirballXL-5 at SOME point during the test program? Really? I mean does ANYONE think someone could actually RESIST that temptation? Hmmm?

Randy

As long as you give it the proper credit: the Thunderbird March, by Barry Gray.

 
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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1864 on: 11/27/2013 08:06 AM »
Obviously you'd need the turbomachinery for takeoff and acceleration.  The question is, can you then shut it down and cruise on the ramjets?  It's not like the inlet pressure recovery is good enough to require much in the way of a boost pump, though whether pressure feed is even possible in principle or not may depend heavily on the chosen cruise conditions as well as how much losing the suction from the core changes the intake behaviour...
As always almost anything is possible if the conditions are right. But the ramjet is fueled by the excess H2 after it's been through the pre cooler and used to drive various turbines. That suggests the flow is a)A gas b) Lowish pressure although (I'm guessing) still some way above sea level atmospheric. c) High volume.

The problem is if you've shut down all the turbo machinery where do you get the thermal energy? The pre burner? Residual heat from the hardware on its own?

Another question would be does the ramjet have a duct of it's own or is all the compression and pressure rise produced by the inlet. I know that at high speeds inlets can generate substantial pressure rises. IIRC the SR71 inlet multiplied the ambient pressure by 37x at M3, so the H2 flow into the burner would have to overcome whatever level the inlet produced.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1865 on: 11/27/2013 02:59 PM »


Ok lets be SERIOUS here for a moment... Is there ANYONE who hasn't been expecting REL/etc to end up playing TaG or the Theme to FirballXL-5 at SOME point during the test program? Really? I mean does ANYONE think someone could actually RESIST that temptation? Hmmm?

Randy

As long as you give it the proper credit: the Thunderbird March, by Barry Gray.

"As performed by the Royal Marines Marching Band" no less? Really though I think the theme song to Fireball-XL5 is a must at some point :)

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 RanulfC

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1866 on: 11/27/2013 03:11 PM »
I'm actually pretty surprised at this. given how much of the SR71's thrust was derived by hardware outside the core engine. While maybe less so about the rest of the airframe I'd have thought there was no way the nacelles could not have been designed and sized without a lot of input from the engine makers. Likewise the SR72 concept did not seem to be something you could just order up a stock engine for.

The SR-71 was designed around the engine P&W was building as an "advanced turboramjet" engine. Lockheed worked very closely with the engine makers to get all the systems to work together but the "original" engine had been based on the idea of using LH2 as fuel. Reducing it to kerosene actually helped both P&W and Lockheed a lot :) The airframe came first with the engines designed to fit and form into the nacelles.

The SR-72 (which we should take with a very large grain of salt because frankly that's a media "trick" to tie it into the SR-71 legacy :)) is actually being designed around using "off-the-shelf" fighter engines for the turbojets, but that leaves the major problems of designing and installing the Duel-Mode-SC/Ramjet ducting which is going to be extremely tricky.

Currently it "looks" like LM is planning on bypassing the turbojet engine entirly at high speed, (which is a good thing) but that's going to serious complicate the interal ducting and shock-wave issues unlike the "in-line" design of the SR-71s engines. As far as I know EVERY design that's tried this ends up having serious issues with the ducting and I don't have much confidence that LM is going to be different somehow.

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This I can understand. I think the move from engines embedded in the wings to engine pods (for most civilian and transport aircraft) has made the coupling much looser.

Easier, cheaper, less "draggy" and maintenace personnel EVERYWHERE celebrate the day it was invented as a international holiday! (Ok not quite but imbedded engines have ALWAYS been a superior pain to work on :))

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I know that REL have been aware of concerns about being an engine company that is designing an aircraft almost since their founding. One of the companies in the group is called "Skylon Enterprises." Currently AFAIK it's working with the CAA to help set the regulatory framework for commercial spaceflight in the UK (and in principle across Europe, which may include French Guiana if it's a region of France).

They may have been "aware" of it but they haven't acted like they really were concerned with the critisim which in some ways has hurt them I'm betting because it is a very significant factor in their PR that they have been "pushing" a "look" for Skylon that may or may not be what it IS going to look like. IF they have to make major changes (or accept someone else as "lead" on the airframe design) they have a very real chance of loosing peoples interest as they would be seen to have had to do "major" redesign work to the vehicle. It's silly but it is a real marketing issue.

One thing I actually worry about with them doing "significant" work with UK/European authorities on a regulatory environment is something we've encountered here with XCOR doing similar work with Mojave spaceport. Due to XCOR's bias' and assumptions Mojave has a set of regulations and guidelines that actually prohibit cetain types and concepts from being built, tested or flown from there. I'm not aware where this has cost Mojave any business mind you but I'm pretty sure it has or will have an impact.

Likewise is the regulatory environment ends up "favoring" Skylon type spaceplanes over anyone else...

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Looking further ahead this could become a joint venture with an airframe mfg. REL contribute all their IP on the Skylon airframe and the airframe mfg brings airframe design and mfg expertise. In effect it becomes a dedicated division for the design and mfg of the Skylon, with engines supplied by REL.

Pretty much the only way it will "work" but REL is going to be directing the majority of the airframe makers efforts in support of their engine and its needs. This is pretty much the opposite of the way it normally works :)

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An airframe mfg is in charge of mfg (and selling) the airframe, an engine mfg in charge of mfg the engines and no one is uncomfortable with the idea of a P&W or Rolls Royce airliner.  :)

Well people MIGHT if the airframe design was dictated to the point where P&W and RR were the ones with the primary input ON the airframe design :)

Subsonic transports don't work that way but hypersonic air-breathing is different and that's not a concept that has gone over well in the past. Usually the airframe designer has a LOT more "input" than the engine designer but with hypersonics its the other way around and that's a major reason a lot of designs never got very far in my opinion: Too much aircraft in my hypersonic engine design ;)

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BTW Reading the AWST article on the SR72 I got the impression that the while they got the sub scale Black Swift prototype engine running OK the cost of the scale up to full size would have been huge.

Most of the time that ends up being the problem :) SABRE doesn't seem to have as much of an issue due to the majority of the engine machinary never actually "seeing" its actual speed (heating/airflow) due to the pre-cooling. My read is they have the turbomachinary pretty much down it is just the intake and exhasut ducting for the DMRJ they need. Of course that's usually the main "problem" area in the first place...

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Hence someone (presumably Aerojet, or their predecessor, to begin with) asked "Could we take a more or less OTS engine and wrap hardware around it to do this mission (preferably without resorting to exotic fuels)?"

That's been done quite often actually, the main reason no one has come up with a satisfactory answer yet seems to boil down to money and the seeming "need" to attach SCramjets to every concept.

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The down side of course is the size of test facilities needed.  :(  :(. Obviously CFD and diagnostics to drive the CFD models have improved enormously since NASP but I don't think anything really cuts it like a flight vehicle. Remember that one of REL's ground rules was only engines cycles that could be tested with open facilities. Anything that begins "Once we've got a Mach 1/2/3/whatever airflow through the duct it'll start producing positive thrust" went straight in the circular filling cabinet.  :) , partly because of theoretical concerns and partly the pragmatic fact that "money was too tight to mention."  :)

Yep but it was "assumed" that extensive CFD was going to be able to replace the actual flight testing and somewhere along the way everyone forgot that the data-base for Mach-4 to Mach-12 flight is mostly "extrapolated" data itself and we do not have an extensive set of hard data to work with for hypersonic flight speeds. We really DO need someone in the world to buckle down and build a hypersonic "X" test vehicle to get the data.

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 (2)
« Reply #1867 on: 11/27/2013 04:28 PM »
The SR-71 was designed around the engine P&W was building as an "advanced turboramjet" engine. Lockheed worked very closely with the engine makers to get all the systems to work together but the "original" engine had been based on the idea of using LH2 as fuel. Reducing it to kerosene actually helped both P&W and Lockheed a lot :) The airframe came first with the engines designed to fit and form into the nacelles.
I think you may have conflated 2 things here. "Suntan" was won by the Glen L Martin company and was an LH2 M3 concept. It was the official design competition winner. I'm not sure who was doing the engine, could have also been P&W. It never happened (the LH2 tank was described as "The worlds biggest thermos flask") and the pump ended up as the core of the RL10.

IIRC Lockheed heard about the engine for the SR71 when it was going to be used for a Navy fighter project which got cancelled. AFAIK the USN is very uncomfortable around any cryogenics
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The SR-72 (which we should take with a very large grain of salt because frankly that's a media "trick" to tie it into the SR-71 legacy :)) is actually being designed around using "off-the-shelf" fighter engines for the turbojets, but that leaves the major problems of designing and installing the Duel-Mode-SC/Ramjet ducting which is going to be extremely tricky.
I think it's certainly had input from the LM PR department.
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Currently it "looks" like LM is planning on bypassing the turbojet engine entirly at high speed, (which is a good thing) but that's going to serious complicate the interal ducting and shock-wave issues unlike the "in-line" design of the SR-71s engines. As far as I know EVERY design that's tried this ends up having serious issues with the ducting and I don't have much confidence that LM is going to be different somehow.
Like SABRE they seem to have optimized for the conditions the vehicle is going to spend the bulk of its time in, IE M6 cruise. So you keep the high speed system in line and treat the turbojet or low BR turbofan as (literally  :)) a side show. Conceptually obvious, until you come to actually building it.  :(

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Easier, cheaper, less "draggy" and maintenace personnel EVERYWHERE celebrate the day it was invented as a international holiday! (Ok not quite but imbedded engines have ALWAYS been a superior pain to work on :))
IIRC Bill Gunston outlines the history, and it's one where the US lead the way. IIRC the UK companies had grossly overestimated the drag on podded engines. Boeing was the lead for this with the B52. The British industry started to change but it took a long time (and the British military side was devastated by the 1957 Defense White Paper).
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They may have been "aware" of it but they haven't acted like they really were concerned with the critisim which in some ways has hurt them I'm betting because it is a very significant factor in their PR that they have been "pushing" a "look" for Skylon that may or may not be what it IS going to look like. IF they have to make major changes (or accept someone else as "lead" on the airframe design) they have a very real chance of loosing peoples interest as they would be seen to have had to do "major" redesign work to the vehicle. It's silly but it is a real marketing issue.
Oh it's a real issue full stop. At one level it's unimportant (what's in a name), at another level it has serious implications on cost and schedule. On yet a third it raises questions like options for towing/carriage/self ferry, which the airframe mfg will have experience with handling.  :(
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One thing I actually worry about with them doing "significant" work with UK/European authorities on a regulatory environment is something we've encountered here with XCOR doing similar work with Mojave spaceport. Due to XCOR's bias' and assumptions Mojave has a set of regulations and guidelines that actually prohibit cetain types and concepts from being built, tested or flown from there. I'm not aware where this has cost Mojave any business mind you but I'm pretty sure it has or will have an impact.

Likewise is the regulatory environment ends up "favoring" Skylon type spaceplanes over anyone else...
True. A case in point IIRC is that propellant tanks must have 2 barriers between propellants. So no common bulkhead tanks.  :( That said if no one else is stepping up to the task of shaping the Europe wide air regulation framework, whats the option?
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Pretty much the only way it will "work" but REL is going to be directing the majority of the airframe makers efforts in support of their engine and its needs. This is pretty much the opposite of the way it normally works :)
I was aware of that for the subsonic world, and the military supersonic world, but I'd guessed for more "experimental" regimes it was more a case of build the aircraft round the engine unless the engine is a rocket, since you've no internal airflows to worry about (I'm thinking about the X1 and X15, for which engine selection seemed to be fairly late in the day).
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Well people MIGHT if the airframe design was dictated to the point where P&W and RR were the ones with the primary input ON the airframe design :)
True. But then they wouldn't just be engine mfgs anymore, and other aircraft mfgs would view them as competitors.

The other issue is the internal politics. Shouldn't matter, but it will. It's just what happens when you have to manage people, not machines.  :(

Airframe mfgs have fairly large design teams and I'd expect some issues if they were told "You're not really needed, the design is 95% complete.  :( " BTW when HOTOL was running the idea for the "spill ramjet" came from the airframe side of the partnership, who described it as "negative drag" to avoid ruffling any feathers.  :(

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Subsonic transports don't work that way but hypersonic air-breathing is different and that's not a concept that has gone over well in the past. Usually the airframe designer has a LOT more "input" than the engine designer but with hypersonics its the other way around and that's a major reason a lot of designs never got very far in my opinion: Too much aircraft in my hypersonic engine design ;)
Exactly. And I'm sure those issues can wreck a project even when the technology is viable.  :(

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Most of the time that ends up being the problem :) SABRE doesn't seem to have as much of an issue due to the majority of the engine machinary never actually "seeing" its actual speed (heating/airflow) due to the pre-cooling. My read is they have the turbomachinary pretty much down it is just the intake and exhasut ducting for the DMRJ they need. Of course that's usually the main "problem" area in the first place...
Yes. As team members also worked on the RZ20 LO2/LH2 GG engine they feel confident they can handle that side of things. I guess the Valkyrie flights will take care of the exhaust side using an E/D nozzle. Presumably the are also confident about the inlets as well. Remember that unlike plug nozzles there is only minimal stand data for E/D nozzle, as it was felt they did not deliver atmospheric compensation, following the very critical 1968 report from Notre Dame.
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That's been done quite often actually, the main reason no one has come up with a satisfactory answer yet seems to boil down to money and the seeming "need" to attach SCramjets to every concept.
I wonder if this a chicken and egg problem. IOW hypersonic flight == SCRamjet. So if you want funding for M5+ you have to have an SCRamjet in the design. IRL (as you've noted) at least one M5 ramjet has flown, and seemed to fly pretty well, but the powers that be don't seem to want to know.  :(
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Yep but it was "assumed" that extensive CFD was going to be able to replace the actual flight testing and somewhere along the way everyone forgot that the data-base for Mach-4 to Mach-12 flight is mostly "extrapolated" data itself and we do not have an extensive set of hard data to work with for hypersonic flight speeds. We really DO need someone in the world to buckle down and build a hypersonic "X" test vehicle to get the data.
Mind you reading "Facing the Heat Barrier" suggest people were eager to get their hands on the extremely large bag of cash the USAF was offering.  :(

It was only years later someone went through the models and realized the collection of optimistic assumptions (and IIRC at least one flat out error in the values of a constant driving the models) used that it was realized this was not going to happen.

I guess the DARPA SCRamjet demonstrators have supplied some data but I keep thinking they are point data. No single vehicle has flown from 0/Sea Level to M4/5/6/whatever and cruised there for a prolonged period of time. I think the closest was the X15. I think the new DARPA XS-1 programme should be interesting here as "Hypersonic research" is listed as one of the goals and a top speed of M10 were certainly meet that.  :) , although my instinct is it will be rocket propelled.
« Last Edit: 11/27/2013 04:33 PM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1868 on: 11/27/2013 08:22 PM »
The SR-71 was designed around the engine P&W was building as an "advanced turboramjet" engine. Lockheed worked very closely with the engine makers to get all the systems to work together but the "original" engine had been based on the idea of using LH2 as fuel. Reducing it to kerosene actually helped both P&W and Lockheed a lot :) The airframe came first with the engines designed to fit and form into the nacelles.
I think you may have conflated 2 things here. "Suntan" was won by the Glen L Martin company and was an LH2 M3 concept. It was the official design competition winner. I'm not sure who was doing the engine, could have also been P&W. It never happened (the LH2 tank was described as "The worlds biggest thermos flask") and the pump ended up as the core of the RL10.

While Martin was the "official" winner, the Lockheed design actually had more work done on it and is usually the design people "show" when they talk Suntan (http://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan) IIRC P&W was supposed to develop the engine for EVERYBODIES design but the actual design work was years behind. Turbopump issues abounded but they DID get them working but only after the project was cancled :)

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IIRC Lockheed heard about the engine for the SR71 when it was going to be used for a Navy fighter project which got cancelled. AFAIK the USN is very uncomfortable around any cryogenics

The MILITARY is very uncomfortable around cyrogenics as a rule. About the only exception has been LOX because a solid core of "distrust" over solid oxygen generator systems. The "original" engine considered for the next generation "after" Suntan by Lockheed was based on an LH2 SERJ engine that Mardquart had designed but changes in the Navy/Air-Force requirements had Mardquart making a "new" SERJ using H2O2/kerosene and which limited top speed to Mach-4 instead of Mach-6 for the LH2 engine. But Lockheed was leery about using hydrogenperoxide and not really confident about the multi-system of the Supercharged Ejector Ram-Jet engine despite Mardquarts data.

Once the "Seamaster" seaplane bomber was cancled P&W were scrambling for someone to buy the engines they were contracted to produce for that aircraft and pitched it to Lockheed and Convair who snapped them up and based their designs for the "A-12" off them. Other than the fact that they used a very specialized and very expensive derivitive of kerosene they turned out to be operationally probably a better decision than the SERJ engines or so Lockheed convinced the Air Force :) (IMHO the SERJ probably would have been a better overall choice but it is hard to "compete" with an already existing and tested engine, which involced actually flight testing one on a B-58 where as SERJ never got flight tested)

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The SR-72 (which we should take with a very large grain of salt because frankly that's a media "trick" to tie it into the SR-71 legacy :)) is actually being designed around using "off-the-shelf" fighter engines for the turbojets, but that leaves the major problems of designing and installing the Duel-Mode-SC/Ramjet ducting which is going to be extremely tricky.
I think it's certainly had input from the LM PR department.

At LEAST for the "exterior" views since no one knows exactly how they are going to route the inlet/exhaust at the moment the internals are ALL PR :)

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Currently it "looks" like LM is planning on bypassing the turbojet engine entirly at high speed, (which is a good thing) but that's going to serious complicate the interal ducting and shock-wave issues unlike the "in-line" design of the SR-71s engines. As far as I know EVERY design that's tried this ends up having serious issues with the ducting and I don't have much confidence that LM is going to be different somehow.
Like SABRE they seem to have optimized for the conditions the vehicle is going to spend the bulk of its time in, IE M6 cruise. So you keep the high speed system in line and treat the turbojet or low BR turbofan as (literally  :)) a side show. Conceptually obvious, until you come to actually building it.  :(

Which is where everone tends to run into those pesky "intergration" problems :)

I wish em luck however... ;)

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Easier, cheaper, less "draggy" and maintenace personnel EVERYWHERE celebrate the day it was invented as a international holiday! (Ok not quite but imbedded engines have ALWAYS been a superior pain to work on :))
IIRC Bill Gunston outlines the history, and it's one where the US lead the way. IIRC the UK companies had grossly overestimated the drag on podded engines. Boeing was the lead for this with the B52. The British industry started to change but it took a long time (and the British military side was devastated by the 1957 Defense White Paper).

Ya there were a lot of mistakes made with the calculations of embedded versus podded engines that were not found out until both had been flying for a while. I seem to recall that once the engines in "pods" were attached to the flying wing they acted to help stabilize the aircraft which was counter-intuitive at the time.

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One thing I actually worry about with them doing "significant" work with UK/European authorities on a regulatory environment is something we've encountered here with XCOR doing similar work with Mojave spaceport. Due to XCOR's bias' and assumptions Mojave has a set of regulations and guidelines that actually prohibit cetain types and concepts from being built, tested or flown from there. I'm not aware where this has cost Mojave any business mind you but I'm pretty sure it has or will have an impact.

Likewise is the regulatory environment ends up "favoring" Skylon type spaceplanes over anyone else...
True. A case in point IIRC is that propellant tanks must have 2 barriers between propellants. So no common bulkhead tanks.  :( That said if no one else is stepping up to the task of shaping the Europe wide air regulation framework, whats the option?

Oh that's easy... Let the FAA do it all ;)

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Pretty much the only way it will "work" but REL is going to be directing the majority of the airframe makers efforts in support of their engine and its needs. This is pretty much the opposite of the way it normally works :)
I was aware of that for the subsonic world, and the military supersonic world, but I'd guessed for more "experimental" regimes it was more a case of build the aircraft round the engine unless the engine is a rocket, since you've no internal airflows to worry about (I'm thinking about the X1 and X15, for which engine selection seemed to be fairly late in the day).

The X-1 was originally supposed to be jet powered but there was no WAY we were going to have the British design OUR supersonic jet engine... So since someone was "playing around" with rocket engines they decided to go that route. I'd point out though that  less than 5 years earlier NACA was trying very hard to make a "supersonic" propeller driven aircraft, so there was still an awful lot of "play" in the theory and design :)

The X-15 was "sortof" built off a planned engine that didn't exist when the airframe was being built. That's why the program started OFF with varients of the X-1 rocket engines before its "real" engine was finally ready. The X-15 HAD to have rockets as no other aero-engine was seen as capable of making multiple hypersonic runs and none of the would allow the projected altitude needed.

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Well people MIGHT if the airframe design was dictated to the point where P&W and RR were the ones with the primary input ON the airframe design :)
True. But then they wouldn't just be engine mfgs anymore, and other aircraft mfgs would view them as competitors.

Under the current circumstances yes, but this gets into a rather "gray" area when dealing with hypersonic designs as LM among others have found out. (And which I suspect they are going to find out again :))

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The other issue is the internal politics. Shouldn't matter, but it will. It's just what happens when you have to manage people, not machines.  :(

Are you suggesting that REL will not be one of those who welcomes our new robot overlords? :)

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Airframe mfgs have fairly large design teams and I'd expect some issues if they were told "You're not really needed, the design is 95% complete.  :( " BTW when HOTOL was running the idea for the "spill ramjet" came from the airframe side of the partnership, who described it as "negative drag" to avoid ruffling any feathers.  :(

Is true but the "airframe/engine" manufacturer system has a very long history and assocated inertia going for it. On the other hand change is often more "forced" than most folks would like it to be and as I've pointed out before; REL really blew the doors off everyone else with a simple but non-obvious answer: Air-Breathing Rocket Engines that did NOT "require" a LACE cycle. Prior to that little "bombshell" everybody was convinced that rockets had to have "liquid" propellant even though at the same time everyone also understood that the RL-10 used "gas/gas" in operation and why. The simple "fact" was no one considered the RL-10 a "gas" propellant rocket engine it was CLEARLY a "liqud" engine...

Couple that little "bias" and the "fact" that air-breathing "space launch" always meant staying in the atmosphere as long as possible to get every little "ounce" of performance out of those turbo-ram-scram jets and it is the airframe driving the engine design and not the other way around. Then when the engine can't match the fantastic performance needed everyone throws up their hands and walks away saying it can't be done.

Turn things around though like Mardquart did with their series of SERJ-engine based proposals and suddenly the airframe design gets a lot simpler, though mistakes will still be made... (The "Hyperdart" comes to mind there ;) )

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Subsonic transports don't work that way but hypersonic air-breathing is different and that's not a concept that has gone over well in the past. Usually the airframe designer has a LOT more "input" than the engine designer but with hypersonics its the other way around and that's a major reason a lot of designs never got very far in my opinion: Too much aircraft in my hypersonic engine design ;)
Exactly. And I'm sure those issues can wreck a project even when the technology is viable.  :(

Mardquart SERJ is an example, they had a flight weight H2O2/Kerosene test engine ready and an almost flight weight LOX/LH2 engine but no airframes to fly them on and no interest from anyone to pay for the development of such an airframe. They pitched to modify the last X-15 to use a SERJ for testing but NASA had already decided to shut down the program and store the airframes.

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As team members also worked on the RZ20 LO2/LH2 GG engine they feel confident they can handle that side of things. I guess the Valkyrie flights will take care of the exhaust side using an E/D nozzle. Presumably the are also confident about the inlets as well. Remember that unlike plug nozzles there is only minimal stand data for E/D nozzle, as it was felt they did not deliver atmospheric compensation, following the very critical 1968 report from Notre Dame.

And this is why professional "bias" and expert "opinion" tend to chap my keester so much :)

The first "TAN" (Thrust Augmentation Nozzle" patent is dated something like 1958! There were several patents for E/D nozzles that were patented and documented by NACA/NASA in the early 1960s but the marjority of the "tests" were very simple lab-bench-top test and no stand time for data collection. Yet the contractors and companies that had been building and testing them felt they would work as advertised but ONE influential paper can blow real world experiance right out of the water...

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That's been done quite often actually, the main reason no one has come up with a satisfactory answer yet seems to boil down to money and the seeming "need" to attach SCramjets to every concept.
I wonder if this a chicken and egg problem. IOW hypersonic flight == SCRamjet. So if you want funding for M5+ you have to have an SCRamjet in the design. IRL (as you've noted) at least one M5 ramjet has flown, and seemed to fly pretty well, but the powers that be don't seem to want to know.  :(

It pretty much seems that way these days. If it doesn't have a "scramjet" in it then it can't be a "hypersonic" design. Never mind that "hypersonic" STARTS at Mach-5 and most SCramjets won't even START till after Mach-7/8! It seems like there is a "conventional wisdom" (with all the flaws that usually entails :)) that ramjets don't operate well over Mach-3 and so you need SCramjets to get to "hypersonic" (Mach-5) speed. Yet people who have built and tested various ramjet engine to a one are confident you could run a subsonic combustion ramjet up to around Mach-8 and still get accelleration out of it. further you can point to test runs that have hit almost Mach-5 by accident with an inlet designed for only Mach-4 so it doesn't seem like much of a leap to hypersonic cruise. But in the end everything falls back to "needing" a SCramjet on-board and you are probably right that in order to get the bucks they need to pander to the perception rather than the reality.

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Yep but it was "assumed" that extensive CFD was going to be able to replace the actual flight testing and somewhere along the way everyone forgot that the data-base for Mach-4 to Mach-12 flight is mostly "extrapolated" data itself and we do not have an extensive set of hard data to work with for hypersonic flight speeds. We really DO need someone in the world to buckle down and build a hypersonic "X" test vehicle to get the data.
Mind you reading "Facing the Heat Barrier" suggest people were eager to get their hands on the extremely large bag of cash the USAF was offering.  :(

Combined with budget cuts around the same time and it seemed to be so "simple" to cancle the "National Hypersonic Laboratory" (X-24C) in favor of more "accurate" and less costly computer modelling. Hell put in context it makes sense to ME and I'm a fan of the X-24C :)

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It was only years later someone went through the models and realized the collection of optimistic assumptions (and IIRC at least one flat out error in the values of a constant driving the models) used that it was realized this was not going to happen.

Part of the problem was that supersonic(s) didn't pan out as expected, (every airline was supposed to be flying multiple SSTs by the mid-70s) and hypersonics was loosing its focus because military air tactics were being changed and redefined with less emphisis on speed and more on stealth. By the time interest began ramping back up CFD was the ONLY method available at a "cost-effective" price.

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I guess the DARPA SCRamjet demonstrators have supplied some data but I keep thinking they are point data. No single vehicle has flown from 0/Sea Level to M4/5/6/whatever and cruised there for a prolonged period of time. I think the closest was the X15. I think the new DARPA XS-1 programme should be interesting here as "Hypersonic research" is listed as one of the goals and a top speed of M10 were certainly meet that.  :) , although my instinct is it will be rocket propelled.

You're correct about the DARPA SCramjets they were of limited use as they "only" collected data during the portion of the flight where the SCramjets were supposed to be operating. The XS-1 has to pretty much be rocket powered although given the "answers" to some of the questions aske I could actually see them being open to a jet/ramjet or SERJ suggestion as long as you could include a rocket to boost it up to Mach-10.

RAndy
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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 93143

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1869 on: 11/28/2013 02:09 AM »
Obviously you'd need the turbomachinery for takeoff and acceleration.  The question is, can you then shut it down and cruise on the ramjets?  It's not like the inlet pressure recovery is good enough to require much in the way of a boost pump, though whether pressure feed is even possible in principle or not may depend heavily on the chosen cruise conditions as well as how much losing the suction from the core changes the intake behaviour...
As always almost anything is possible if the conditions are right. But the ramjet is fueled by the excess H2 after it's been through the pre cooler and used to drive various turbines. That suggests the flow is a)A gas b) Lowish pressure although (I'm guessing) still some way above sea level atmospheric. c) High volume.

The problem is if you've shut down all the turbo machinery where do you get the thermal energy? The pre burner? Residual heat from the hardware on its own?

Just tap the LH2 feedline before it gets to any of that stuff.  Ramjets aren't that fussy about the thermodynamic state of their fuel, are they?

On the other hand, if the burners were carefully designed for warm hydrogen gas, a spray of liquid fuel might take too long to burn, resulting in suboptimal behaviour or even damage (though hydrogen should be less problematic than hydrocarbons in this respect)...  and the fuel handling bits would have to be able to deal with deep cryo temperatures...

You could probably run a small boost pump off the fuel cells, but boiling and heating the hydrogen (if it proved to be necessary) would require a lot more power...

To use the preburner to heat the hydrogen, you need to run the helium loop.  You also need air to burn the extra hydrogen with, which means you need to give the helium enough juice to turn the turbocompressor to suck air through the precooler and still have enough energy to heat the hydrogen up enough to run both the hydrogen pump and the helium boost compressor, and once you've got all that going you might as well light the main combustion chambers...  You could include another heat exchanger just for ramjet mode, but that adds mass and complexity (and cost, and hydrogen embrittlement issues) and may not physically fit; if you've got to heavily modify the engine (or remove and replace it) for self-ferry, it's probably better to just use a dirigible or something...

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Another question would be does the ramjet have a duct of it's own or is all the compression and pressure rise produced by the inlet. I know that at high speeds inlets can generate substantial pressure rises. IIRC the SR71 inlet multiplied the ambient pressure by 37x at M3, so the H2 flow into the burner would have to overcome whatever level the inlet produced.

Supposedly the recovery pressure is about 1.3 bar throughout the airbreathing portion of the launch profile.  The tanks are supposed to be at 1 atm gage IIRC, so at Mach 2 and 40,000 feet the nacelle pressure is slightly higher than the tank pressure.  Shutting down the core would increase the flow resistance, which I imagine means higher recovery pressure if not an outright excursion from the available operating range of the inlet - but of course there's no reason you have to cruise at a point on the launch profile...

Would the shut-down core act as an aerospike, or would it just contribute a bunch of drag?

I still suspect that just throttling down is a much better idea.  From the C1 spreadsheet it appears that the SABRE 3 in airbreathing mode can be throttled down by at least 1/3 in terms of hydrogen flow, though this may be an artifact of the flight path...

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1870 on: 11/28/2013 08:03 AM »
Just tap the LH2 feedline before it gets to any of that stuff.  Ramjets aren't that fussy about the thermodynamic state of their fuel, are they?
Well given the trouble it takes to keep LH2 liquid I'd guess the odds on bet is the flow will be a gas by the time it gets to the burners.
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On the other hand, if the burners were carefully designed for warm hydrogen gas, a spray of liquid fuel might take too long to burn, resulting in suboptimal behaviour or even damage (though hydrogen should be less problematic than hydrocarbons in this respect)...  and the fuel handling bits would have to be able to deal with deep cryo temperatures...
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You could probably run a small boost pump off the fuel cells, but boiling and heating the hydrogen (if it proved to be necessary) would require a lot more power...

To use the preburner to heat the hydrogen, you need to run the helium loop.  You also need air to burn the extra hydrogen with, which means you need to give the helium enough juice to turn the turbocompressor to suck air through the precooler and still have enough energy to heat the hydrogen up enough to run both the hydrogen pump and the helium boost compressor, and once you've got all that going you might as well light the main combustion chambers...  You could include another heat exchanger just for ramjet mode, but that adds mass and complexity (and cost, and hydrogen embrittlement issues) and may not physically fit; if you've got to heavily modify the engine (or remove and replace it) for self-ferry, it's probably better to just use a dirigible or something...
Exactly.
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Supposedly the recovery pressure is about 1.3 bar throughout the airbreathing portion of the launch profile.  The tanks are supposed to be at 1 atm gage IIRC, so at Mach 2 and 40,000 feet the nacelle pressure is slightly higher than the tank pressure.  Shutting down the core would increase the flow resistance, which I imagine means higher recovery pressure if not an outright excursion from the available operating range of the inlet - but of course there's no reason you have to cruise at a point on the launch profile...
"Gage" pressure excludes atmospheric pressure. Therefor total tank pressure ("absolute" pressure) is 2 atm. That "atm" is SL pressure. So you've got roughly 2atm absolute tank pressure driving 1.3bar system, which  might be enough to pressure feed it.
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Would the shut-down core act as an aerospike, or would it just contribute a bunch of drag?
Well with the path from the inlet compressor closed air should build up in the ducting until its pressure exceeds ambient at that speed,like the nozzles when the Spacex F9 1st stage re-enters nozzle down, at which point the bulk of the flow should divert around it, like an overflowing cup with the tap still on.
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I still suspect that just throttling down is a much better idea.  From the C1 spreadsheet it appears that the SABRE 3 in airbreathing mode can be throttled down by at least 1/3 in terms of hydrogen flow, though this may be an artifact of the flight path...
Agreed.
I think that with modern seal and bearing technology, along with what is known about H2 embrittlement, if the engine is run at relatively low power it should have quite a long life. I hope this will be something the ground engine test programme looks at. If it can be proved that extended cruise had no or little effect on engine life then only structural and legal issues would prevent Skylon being able to self ferry.

But I wouldn't underestimate those legal issues, especially in skies as crowded as those of Europe.  :(
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Offline 93143

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1871 on: 11/28/2013 08:13 AM »
Supposedly the recovery pressure is about 1.3 bar throughout the airbreathing portion of the launch profile.  The tanks are supposed to be at 1 atm gage IIRC, so at Mach 2 and 40,000 feet the nacelle pressure is slightly higher than the tank pressure.  Shutting down the core would increase the flow resistance, which I imagine means higher recovery pressure if not an outright excursion from the available operating range of the inlet - but of course there's no reason you have to cruise at a point on the launch profile...
"Gage" pressure excludes atmospheric pressure. Therefor total tank pressure ("absolute" pressure) is 2 atm. That "atm" is SL pressure. So you've got roughly 2atm absolute tank pressure driving 1.3bar system, which  might be enough to pressure feed it.

At 40,000 feet, ambient pressure is less than 20 kPa.  So if the tank pressure is controlled during flight to maintain 1 atm gage, it would be below the recovery pressure at that altitude.

I know the on-orbit tank pressure is supposed to be about 1 bar, but that they only vent the tanks after MECO.  So maybe they do keep them at 2 atm for the duration of powered flight...
« Last Edit: 11/28/2013 08:23 AM by 93143 »

Offline Turbomotive

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1872 on: 11/28/2013 12:42 PM »
I really believe that self ferry is the way to go. It simplifies the logistics radically and I think an air breathing Skylon in self ferry mode (no LO2 on board and possibly only a part load of LH2, but probably the payload) would take off with much lower thrust, takeoff speed and engine wear during the trip (compared to a launch mission).

How about ferry by airship, and a British airship to boot :)

Cargo cradle underslung a Hybrid Air Vehicles (http://www.hybridairvehicles.com/) heavy-lift vehicle. Modify the inflatable pontoons under the HAV to conform with the Skylon fuselage so that it will sit neatly underneath, protecting it from e.g. ground debris and hail damage and reducing the tendency to weathervane in the wind. Additional protective "skirts" could be dropped from the underside of the HAV.

The company are getting the prototype vehicle they built for the US Army back in bits, and they're anticipating putting it back together to restart UK flights in Q3 2014.

Also, "Thunderbirds Are Go!" MUST be played over loudspeakers as the Skylon is unloaded from the HAV. It's compulsory :D

*LIKE*

Airship transport has been suggested/quoted before here, it possibly even came from Alan Bond. I was a little surprised it hadn't got more coverage here, so well done for pointing it out again. They are offering heavy lift up to 200 tonnes so could certainly cover the job. Seems like a cracking bit of kit and being funded by the good ol' U.S. of A. military. God bless you America ;)

Indeed :) It occurs to me that a HAV airship should be part of the spaceport's inventory. I've seen quoted a helicopter, to winch a passenger module, and a fuel tanker aircraft, if Skylon's stuck at a remote airport, but a HAV, would be able to rescue a dead Skylon in almost any situation?


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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1873 on: 11/28/2013 05:46 PM »
"Gage" pressure excludes atmospheric pressure. Therefor total tank pressure ("absolute" pressure) is 2 atm. That

At 40,000 feet, ambient pressure is less than 20 kPa.  So if the tank pressure is controlled during flight to maintain 1 atm gage, it would be below the recovery pressure at that altitude.

I know the on-orbit tank pressure is supposed to be about 1 bar, but that they only vent the tanks after MECO.  So maybe they do keep them at 2 atm for the duration of powered flight...
This has come up with reference to the tank P system of the Delta LVs (Delta II and II IIRC). The  original system kept tank pressure referenced to SL pressure despite the loads the pressurization was required to resist going down with altitude. Shifting to an outside pressure + X psi save a lot of Helium.

Do you have a reference for Skylon's behavior for this? AFAIK the usual reference when people talk about "gage" pressure is sea level, not ambient.
The SR-71 was designed around the engine P&W was building as an "advanced turboramjet" engine. Lockheed worked very closely with the engine makers to get all the systems to work together but the "original" engine had been based on the idea of using LH2 as fuel. Reducing it to kerosene actually helped both P&W and Lockheed a lot :) The airframe came first with the engines designed to fit and form into the nacelles.
While Martin was the "official" winner, the Lockheed design actually had more work done on it and is usually the design people "show" when they talk Suntan (http://en.wikipedia.org/wiki/Lockheed_CL-400_Suntan) IIRC P&W was supposed to develop the engine for EVERYBODIES design but the actual design work was years behind. Turbopump issues abounded but they DID get them working but only after the project was cancled :)
I had not realized this.
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The MILITARY is very uncomfortable around cyrogenics as a rule. About the only exception has been LOX because a solid core of "distrust" over solid oxygen generator systems. The "original" engine considered for the next generation "after" Suntan by Lockheed was based on an LH2 SERJ engine that Mardquart had designed but changes in the Navy/Air-Force requirements had Mardquart making a "new" SERJ using H2O2/kerosene and which limited top speed to Mach-4 instead of Mach-6 for the LH2 engine. But Lockheed was leery about using hydrogenperoxide and not really confident about the multi-system of the Supercharged Ejector Ram-Jet engine despite Mardquarts data.
If Marquart have full size H2O2/kero engines this might be a candidate for the XS1 programme, if it could do a brief zoom climb to M10?

Of course finding an airframe mfg to partner with won't be easy. :(
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Once the "Seamaster" seaplane bomber was cancled P&W were scrambling for someone to buy the engines they were contracted to produce for that aircraft and pitched it to Lockheed and Convair who snapped them up and based their designs for the "A-12" off them. Other than the fact that they used a very specialized and very expensive derivitive of kerosene they turned out to be operationally probably a better decision than the SERJ engines or so Lockheed convinced the Air Force :) (IMHO the SERJ probably would have been a better overall choice but it is hard to "compete" with an already existing and tested engine, which involced actually flight testing one on a B-58 where as SERJ never got flight tested)
I saw some video of that plane. It was a beast, probably the last flowering of the military sea plane.  :(

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At LEAST for the "exterior" views since no one knows exactly how they are going to route the inlet/exhaust at the moment the internals are ALL PR :)
I suspect some parts of it are fairly accurate, but the question is which?  :)

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I wish em luck however... ;)
Well I can make almost anything sound simple.  :) A straight through duct with the turbojet in side channel should give the smoothest flow at full cruise speed, especially if the turbojet is shut down.
Likewise using a full size existing COTS-ish engine makes good sense (I say -ish because historically it's taken very strong management to resist the siren call to "Just make a few minor changes to improve things." No problem until your engine breaks and you can't just call a replacement from stores, because of all the mods that have been made.  :(
 
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Easier, cheaper, less "draggy" and maintenace personnel EVERYWHERE celebrate the day it was invented as a international holiday! (Ok not quite but imbedded engines have ALWAYS been a superior pain to work on :))

Ya there were a lot of mistakes made with the calculations of embedded versus podded engines that were not found out until both had been flying for a while. I seem to recall that once the engines in "pods" were attached to the flying wing they acted to help stabilize the aircraft which was counter-intuitive at the time.
And IIRC flying wing designs need quite a lot of stabilization to begin with.  :)
I think it was in "Widebody" (the 707 story) that Boeing discovered this on the B52. The wings were so long and flexible they would waggle without all the engines on them.  :)
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Oh that's easy... Let the FAA do it all ;)
In which case we end up with regulations skewed to WK2/SS2?  :(
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The X-1 was originally supposed to be jet powered but there was no WAY we were going to have the British design OUR supersonic jet engine... So since someone was "playing around" with rocket engines they decided to go that route. I'd point out though that  less than 5 years earlier NACA was trying very hard to make a "supersonic" propeller driven aircraft, so there was still an awful lot of "play" in the theory and design :)

The X-15 was "sortof" built off a planned engine that didn't exist when the airframe was being built. That's why the program started OFF with varients of the X-1 rocket engines before its "real" engine was finally ready. The X-15 HAD to have rockets as no other aero-engine was seen as capable of making multiple hypersonic runs and none of the would allow the projected altitude needed.
Well if you look at pictures of the Miles M 52 you might recognize a certain likeness in the structure as well.  :)

Was that what people called the "Thunderscreech?" I think it's official name was the Thundershark, until people heard it.  :)
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True. But then they wouldn't just be engine mfgs anymore, and other aircraft mfgs would view them as competitors.

Under the current circumstances yes, but this gets into a rather "gray" area when dealing with hypersonic designs as LM among others have found out. (And which I suspect they are going to find out again :))

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The other issue is the internal politics. Shouldn't matter, but it will. It's just what happens when you have to manage people, not machines.  :(
Are you suggesting that REL will not be one of those who welcomes our new robot overlords? :)
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Actually I was thinking of the design team of the airframe mfg. 

Is true but the "airframe/engine" manufacturer system has a very long history and assocated inertia going for it. On the other hand change is often more "forced" than most folks would like it to be and as I've pointed out before; REL really blew the doors off everyone else with a simple but non-obvious answer: Air-Breathing Rocket Engines that did NOT "require" a LACE cycle. Prior to that little "bombshell" everybody was convinced that rockets had to have "liquid" propellant even though at the same time everyone also understood that the RL-10 used "gas/gas" in operation and why. The simple "fact" was no one considered the RL-10 a "gas" propellant rocket engine it was CLEARLY a "liqud" engine...

Couple that little "bias" and the "fact" that air-breathing "space launch" always meant staying in the atmosphere as long as possible to get every little "ounce" of performance out of those turbo-ram-scram jets and it is the airframe driving the engine design and not the other way around. Then when the engine can't match the fantastic performance needed everyone throws up their hands and walks away saying it can't be done.

Turn things around though like Mardquart did with their series of SERJ-engine based proposals and suddenly the airframe design gets a lot simpler, though mistakes will still be made... (The "Hyperdart" comes to mind there ;) )
The only innovation you missed that Bond made was not trying to reused the excess GH2 from the precooler for anything and just dumping it overboard (the spill ramjet came later).   :)

IF REL does go with the idea of Skylon Enterprises as the (nominal) airframe mfg "face" gets saved all round.  :) The market sees a radical vehicle built by a new company but backed by an established airframe mfg for the heavy lifting involved in volume mfg. Exactly how much design (rather than mfg) expertise is contributed by the airframe partner does not have to be specified.
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Subsonic transports don't work that way but hypersonic air-breathing is different and that's not a concept that has gone over well in the past. Usually the airframe designer has a LOT more "input" than the engine designer but with hypersonics its the other way around and that's a major reason a lot of designs never got very far in my opinion: Too much aircraft in my hypersonic engine design ;)
Exactly. And I'm sure those issues can wreck a project even when the technology is viable.  :(
Those who do not learn the lessons of history.....  :(
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Mardquart SERJ is an example, they had a flight weight H2O2/Kerosene test engine ready and an almost flight weight LOX/LH2 engine but no airframes to fly them on and no interest from anyone to pay for the development of such an airframe. They pitched to modify the last X-15 to use a SERJ for testing but NASA had already decided to shut down the program and store the airframes.
So there's at least one full size SERJ in existence?
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And this is why professional "bias" and expert "opinion" tend to chap my keester so much :)

The first "TAN" (Thrust Augmentation Nozzle" patent is dated something like 1958! There were several patents for E/D nozzles that were patented and documented by NACA/NASA in the early 1960s but the marjority of the "tests" were very simple lab-bench-top test and no stand time for data collection. Yet the contractors and companies that had been building and testing them felt they would work as advertised but ONE influential paper can blow real world experiance right out of the water...
Off topic something similar happened in AI research in the late 60's. A deeply critical report on one approach ended most research funding for it for 20+ years in the US.

Note that anyone could have revisited the use of E/D nozzles if they'd gone back to the original reports and noted the tests at Notre Dame were not the same as the original procedure, biasing the results.

But AFAIK only REL and it's partners bothered to look deeper:(

Same with O2 cooling. NASA demonstrated it would work, but only Rotary Rocket 20+ years ago actually tried it (without a hitch).

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I wonder if this a chicken and egg problem. IOW hypersonic flight == SCRamjet. So if you want funding for M5+ you have to have an SCRamjet in the design. IRL (as you've noted) at least one M5 ramjet has flown, and seemed to fly pretty well, but the powers that be don't seem to want to know.  :(

It pretty much seems that way these days. If it doesn't have a "scramjet" in it then it can't be a "hypersonic" design. Never mind that "hypersonic" STARTS at Mach-5 and most SCramjets won't even START till after Mach-7/8! It seems like there is a "conventional wisdom" (with all the flaws that usually entails :)) that ramjets don't operate well over Mach-3 and so you need SCramjets to get to "hypersonic" (Mach-5) speed. Yet people who have built and tested various ramjet engine to a one are confident you could run a subsonic combustion ramjet up to around Mach-8 and still get accelleration out of it. further you can point to test runs that have hit almost Mach-5 by accident with an inlet designed for only Mach-4 so it doesn't seem like much of a leap to hypersonic cruise. But in the end everything falls back to "needing" a SCramjet on-board and you are probably right that in order to get the bucks they need to pander to the perception rather than the reality.
It's especially odd because ramjets are (fairly) simple. In principle you could build a dozen of them and test slight improvements, gradually reducing the amount of deceleration to reduce deceleration losses, or raising the top speed (while preserving the starting speed)  if you could find a way to cost effectively get above M1 to start to get reasonable compression.  :( that requirement (M1+ in air) historically what has put this off limits to anybody but the professionals.

High power rocketeers have Mach busting competitions but an amateur vehicle with wings above M1? The only one I know was that Jim Bede design, which did not end happily.  :(

That said tubjets are now in the amateur range, pulse jets have been for some time. An amateur model ramjet test programme might be in the feasible range.  :)

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Combined with budget cuts around the same time and it seemed to be so "simple" to cancle the "National Hypersonic Laboratory" (X-24C) in favor of more "accurate" and less costly computer modelling. Hell put in context it makes sense to ME and I'm a fan of the X-24C :)
A fair point, sadly.  :(
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Part of the problem was that supersonic(s) didn't pan out as expected, (every airline was supposed to be flying multiple SSTs by the mid-70s) and hypersonics was loosing its focus because military air tactics were being changed and redefined with less emphisis on speed and more on stealth. By the time interest began ramping back up CFD was the ONLY method available at a "cost-effective" price.
True. A nice demonstration of the adage that technology capabilities are "tough to acquire, but easy to loose."  :(
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You're correct about the DARPA SCramjets they were of limited use as they "only" collected data during the portion of the flight where the SCramjets were supposed to be operating. The XS-1 has to pretty much be rocket powered although given the "answers" to some of the questions aske I could actually see them being open to a jet/ramjet or SERJ suggestion as long as you could include a rocket to boost it up to Mach-10.
I'd go further if you have a full size engine system (and can find an airframe partner) I think they will give you a shot.
But how many mainframe companies are left in the US?
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1874 on: 11/29/2013 01:59 AM »
Do you have a reference for Skylon's behavior for this?

No, all I found was this (admittedly I didn't look especially hard):

http://forum.nasaspaceflight.com/index.php?topic=24621.msg755106#msg755106

The fact that it isn't vented does not imply that it isn't actively pressurized, of course.  With subcooled propellants as described, once the engines started you'd rapidly be pulling a vacuum without some form of active pressurization, because the vapour pressure by itself is below ambient.  The exact pressurization schedule is unknown to me at present; I made what I thought was a reasonable guess.

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AFAIK the usual reference when people talk about "gage" pressure is sea level, not ambient.

The term derives from the fact that a pressure gauge without a vacuum or other reference chamber can only read pressures relative to ambient.  There are two ways to spell it, but either way it means the pressure a vented gauge would read.
« Last Edit: 11/29/2013 10:21 AM by 93143 »

Offline sb

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1875 on: 11/29/2013 06:57 AM »
Oh my god could people please stop quoting entire pages of text!

Offline Citizen Wolf

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1876 on: 12/02/2013 09:56 PM »
Well, that seems to have killed the thread   :o
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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1877 on: 12/04/2013 08:41 AM »
Well, that seems to have killed the thread   :o
Actually just waiting for someone to post something worth commenting on.  :(
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Citizen Wolf

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1878 on: 12/04/2013 10:47 AM »
Where's that report on the skylon business model? :( It's almost year end.
The only thing I can be sure of is that I can't be sure of anything.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (2)
« Reply #1879 on: 12/04/2013 11:20 AM »
Where's that report on the skylon business model? :( It's almost year end.

It's right here.



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