This will not be civilian related. BAE will make sure of that.
I don’t know why you cling to this idea that initially at least this flight demonstrator is going to be anything other than a vehicle that services military requirements in all it’s aspects.
Especially as we now have three heavily military invested companies onboard. I don’t even expect the demonstrator to fly anywhere than the US. Military hypersonic research is where the money is and probably the main reason Boeing & RR invested in REL.
Skylon is pretty certainly off the table for the foreseeable future.
Quote from: Star One on 04/14/2018 06:56 pmThis will not be civilian related. BAE will make sure of that.BAe have less than a 20% stake in the company. Quote from: Star OneI don’t know why you cling to this idea that initially at least this flight demonstrator is going to be anything other than a vehicle that services military requirements in all it’s aspects. Because a demonstrator is what it is. It will not be capable of "Servicing military requirements" until it's demonstrated it can actually work, just as none of the SCRamjet research vehicles have done. But mostly because a)There are no sensible hypersonic military applications that stand up to close scrutiny. The truth is if you want fast long range strike nothing beats an ICBM already. The problem is to design a cheap 1 warhead ICBM to do so. The trouble is (and military contractors understand this verywell) once you do so the "floor price" for an actual ICBM drops through the floor b) I have a long standing interest in substantially dropping the cost of launch IE by 10x. There are lots of people who want "on demand" launch to LEO. Some are military, others are not. Not a ticket to ride with a 1-2% failure rate (on mature systems). I mean an actual asset they control.And a lot more people would pay for P2P with rather more "aircraft like" operations than BFR will ever achieve. Quote from: Star OneEspecially as we now have three heavily military invested companies onboard. I don’t even expect the demonstrator to fly anywhere than the US. Military hypersonic research is where the money is and probably the main reason Boeing & RR invested in REL.No, you have 1 (BAe), one (RR) that's got mixed military and civilian interests and the Boeing connection is an investment fund, not actually the Boeing aircraft company. Note that word research. Hence my question about what features would the FTV need to appeal to other groups who want to do basic research in what is (AFAIK) the first reusable M5+ vehicle in half a century.The continuing inability to build a viable SCramjet suggests there is still quite a need for basic data collection in this area.Quote from: Star OneSkylon is pretty certainly off the table for the foreseeable future.As I noted there are quite a number of operational and structural features of Skylon that could be tested as part of the FTV programme. Many of them have applications to whatever vehicle is ultimately used to house an operational SABRE engine. Everyone of those tested by the FTV pushes Skylons TRL a notch further up the scale.
BAE’s investments also highlight the potential defence applications, such as weapons capable of flying at hypersonic speeds.
Every other discussion I’ve seen regarding this recent deal online, and other past developments leading up to this outside of this forum has been in terms of its military application.
BAE are the steering force now in this, their actual percentage is pretty irrelevant but it’s big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isn’t civilian.
QuoteBAE’s investments also highlight the potential defence applications, such as weapons capable of flying at hypersonic speeds.https://www.telegraph.co.uk/business/2018/04/12/reaction-engines-secures-boeing-rolls-royce-backing-hypersonic/
Outside of that there’s plenty of applications for the technology fully outside of the aviation field and I imagine they’d be both easier and quicker to exploit than a space vehicle.
After all a lot of investors these days are looking for the quick return or the shortest route to a return which this seems to offer here.
Quote from: Star One on 04/14/2018 11:34 pmEvery other discussion I’ve seen regarding this recent deal online, and other past developments leading up to this outside of this forum has been in terms of its military application.Again this vehicle has no direct military applications. I'd certainly agree that it could be used to gather the data to build a military vehicle. I'd also agree that many of the research groups who would like to use it are military funded. You seem to be equating "Looks like a reconnaissance drone" with is a reconnaissance drone. IRL what you're talking about is about as sensible as sticking missiles on an X-15 (which is a plot device in a Stephen Baxter novel IIRC, but makes no real sense IRL). Besides when was the last time you ever heard BAe spend their money on developing their own vehicle without an actual MoD or DoD requirements document or research budget?Quote from: Star OneBAE are the steering force now in this, their actual percentage is pretty irrelevant but it’s big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isn’t civilian.If it comes to a shareholder vote you'll find the difference is between "We would very much like and" and "This is what you will do" to REL management. Quote from: Star OneQuoteBAE’s investments also highlight the potential defence applications, such as weapons capable of flying at hypersonic speeds.https://www.telegraph.co.uk/business/2018/04/12/reaction-engines-secures-boeing-rolls-royce-backing-hypersonic/And if they'd made floor cleaners they'd no doubt stress its application to floor cleaning. It's what they do. Quote from: Star OneOutside of that there’s plenty of applications for the technology fully outside of the aviation field and I imagine they’d be both easier and quicker to exploit than a space vehicle. Which won't need a Flight Test Vehicle. So not really relevant to this topic.Quote from: Star OneAfter all a lot of investors these days are looking for the quick return or the shortest route to a return which this seems to offer here.The issue with REL is that it's not a get rich quick scheme. It is (potentially) a get very rich scheme (and lower the price of space access 10x). This is a stage toward that process. Could we discuss what this vehicle could do rather than why it would do it? I'd like to hear from people who have some idea what the outstanding questions in hypersonics are and what would be needed to resolve them if a reusable flight vehicle was available.
Anyway why did you feel the need to start a new thread on this when there is already a perfectly serviceable thread to discuss this. There is nothing in your OP that made it worthy of a separate thread. In fact it would quite easily have fitted in the main REL thread. Especially when any such demonstrator is still many years away and much could change before then.
Quote from: Star One on 04/15/2018 12:17 pmAnyway why did you feel the need to start a new thread on this when there is already a perfectly serviceable thread to discuss this. There is nothing in your OP that made it worthy of a separate thread. In fact it would quite easily have fitted in the main REL thread. Especially when any such demonstrator is still many years away and much could change before then.Perhaps you'd like to try putting an "IMHO" in that first sentence?It's certainly advanced and there is a pretty wide range of options for REL to consider. while not a top priority some of the initial planning should be started now.For instance the outline conversion report for turning the D-21 into a test bed for the DRACO engine said there is no low speed wind tunnel data for this shape, because it was never designed to land in the first place. That's fine for a 1 shot expendable system but a problem if you want to get it back.
I’d thought post #7 probably suggests the best route to your OP.
Even if you were considering the D-21 planform, the mentioned LOX saddle tank by itself wouldn't be enough right? You would need to also colocate a methane or hydrogen tank in the same barrel area (concentric barrels with shared wall?). If, like some artist impressions, there is a secondary engine, then having wet wing tanks for kerosene makes some sense, but you aren't putting cryogens in the wings. Since this would be a test vehicle, you might have drop tanks for added propellant during takeoff/climbout, assuming you don't airdrop from something (Stratolaunch's Roc?)
Incidentally the DRACO engine also uses an aerospike and the power to move it over the projected flight range was anticipated to peak at 5KVA, with average levels at 2.5KVA. That sounds a lot but was apparently expected to be within range of a ram air powered generator based APU.
Quote from: john smith 19 on 04/17/2018 07:11 amIncidentally the DRACO engine also uses an aerospike and the power to move it over the projected flight range was anticipated to peak at 5KVA, with average levels at 2.5KVA. That sounds a lot but was apparently expected to be within range of a ram air powered generator based APU. Addressing only this part, 2.5KVA*10 minutes = a couple of kilos of batteries.
I wasn't sure if this should go in "Advance Concepts" or "Commercial" with the main SABRE/Skylon thread, but it's not meant to be a product and it' would certainly be advanced.
REL have talked about the idea of a "Flight Test Vehicle" on a couple of occasions. Earlier ideas were for a scaled down Skylon, running LOX/Methane rockets while the current design, resembles the D-21 M3 reconnaissance drone designed to launch off the back of a couple of modified SR71s in the late 60's. then modified with a booster longer than the drone, was tested off a modified B52, before the whole project was cancelled.
Every other discussion I've seen regarding this recent deal online, and other past developments leading up to this outside of this forum has been in terms of its military application.
BAE are the steering force now in this, their actual percentage is pretty irrelevant but it's big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isn't civilian.
https://www.telegraph.co.uk/business/2018/04/12/reaction-engines-secures-boeing-rolls-royce-backing-hypersonic/Outside of that there's plenty of applications for the technology fully outside of the aviation field and I imagine they'd be both easier and quicker to exploit than a space vehicle. After all a lot of investors these days are looking for the quick return or the shortest route to a return which this seems to offer here.
Has anyone considered asking Reaction Engines about this? I am sure that Alan Bond would tell, if he's able to.
JS19 wrote:QuoteI wasn't sure if this should go in "Advance Concepts" or "Commercial" with the main SABRE/Skylon thread, but it's not meant to be a product and it' would certainly be advanced. Works for meQuoteREL have talked about the idea of a "Flight Test Vehicle" on a couple of occasions. Earlier ideas were for a scaled down Skylon, running LOX/Methane rockets while the current design, resembles the D-21 M3 reconnaissance drone designed to launch off the back of a couple of modified SR71s in the late 60's. then modified with a booster longer than the drone, was tested off a modified B52, before the whole project was cancelled.I recall the rocket powered vehicles were actually more like aerodynamic test vehicles rather than an engine/cycle test vehicle which is what the current "FTV" seems to be aimed at. (Speaking of how about some links to past and present concepts, test goals, and other information?)Nice find on the DRACO/D-21 having something to build on would help with the costing as even a subscale demonstrator is going to be expensive. (Despite what the cited studies actually "say" I'll note that they both include the verbiage "only vehicle designed to attain/maintain hypersonic speeds" which is wrong as the D-21 never came close to Mach-5 which is the actual boundary of "hypersonic" speed) I suppose the first question is what exactly are they trying to 'test'?1) If they want to test the airframe design, (which I'm doubting as we've already seen the details differ from one company or group to another) then whatever is used will be designed around both the engines and the airframe and an integration of the two. Being's Boeing is onboard I highly doubt it will look like the Skylon we're used to from REL.2) If they want to flight test the engine/cycle/system , (much more likely) then the airframe doesn't matter as much though the higher the testing speeds the more the design will want to "close" towards an approximation of "real" design. But initially you want to demonstrate a series of tests along a spectrum of speed if not to 'full' capability then at least to certain significant test points. For example such test points could include; Take off, climb, acceleration, ability to perform subsonic/transonic/supersonic and back transitions, accelerate to a 'maximum' speed, decelerate back through transonic and return to land, (or be recovered) and then do it all over again multiple times. (Note switching between air-breathing and pure rocket mode at various points will be a requirement so it will have to haul a LOX tank around as you suggest )As noted in the reports the D21 doesn't have very good low speed handling qualities so it would probably need modification to the wings to provide such. You're also going to have to install landing and possibly take off gear.If you are 'just' wanting to test the engine at various flight speeds then it might be better to pull a page from history and use a much simpler and more robust design type which while you'd have to 'build' can in fact be pretty straight forward AND cost effective. You can't really go wrong with something along the lines of the Lockheed X7 (https://en.wikipedia.org/wiki/Lockheed_X-7) ramjet test vehicle, which I will note CAN hit hypersonic speeds. (Late model drones topped out very near Mach-5 {and with a better engine could have done so) Given the SABRE T/W launch can be from a rail and landing kept 'simple' by keeping the parachute and "spike" from the original. Granted dimensions would have to be larger but it's certainly an option.Lastly there is the "existing aircraft airframe" conversion option. Not that I can see a Learjet outfitted with a pair of 'mini-SABRE's' but conversions have been made of several supersonic aircraft by many nations with some of the US ones being "Q" series versions of the F-106, F4, and F-16 and of course there are 'sale' versions of the T-38, F-106, F-104 and others.Finding and converting an Starfighter might be an good option as it's a bit bigger than the D-21 and if suitably braced you might be able to mount "mini-SABRE's" in place of the wingtip tanks and utilize the full capacity of the fuselage.Of course having said all the above IF the various contractors can find someone to 'pay' for it most of them (Boeing, BAE, etc, frankly probably everyone BUT REL ) might prefer to 'build-from-scratch', especially if that 'customer' is a government. And while I DO agree the initial test vehicle won't have an obvious or "built-in" Military Operational Capability and disagree with Star One that there is any "obvious" bias towards having such in a "test" vehicle simple because who's interested and who's building it the fact is such a vehicle 'could' have a secondary purpose IF built to certain specifications. It's that last part that will be telling because I recall that the original (AF driven) specifications for the X-33 program were in fact quite interesting, especially given the launch and landing locations chosen for the program.(Launch from Edwards AFB towards a facility in Utah, Speed in excess of Mach-12 and 'several hundred pounds' of "test instruments" in a long narrow bay... At the time it was noted by several people the 'test instrument bay' could hold a STAR solid motor and a microsatellite as 'payload' after all ) And while Star One is kind of obsessed with "hypersonic strike" missions the ACTUAL most likely mission is frankly as an advanced D-21 system for a reconnaissance drone. (Any 'weapon' has to be deployed from the inside of the vehicle mind you and THEN transition through a Mach-5+ shockwave AND still remain aimed at the target all of which is VERY difficult. And since it can't mass more than 2,000lbs at most it has to be highly accurate so obviously guided and everything has to be able to stand up to hypersonic speeds since that's when it's launched. As we've not developed any that work yet...) And for that you'd need specialized sensors, environmental conditioning equipment, (hypersonic speeds remember) power and others which will amount to something on the order of several hundred to maybe a thousand pounds. (Remember also you're flying at hypersonic speeds at almost 100,000ft so "OTS" sensor won't work) And then there's the 'range' question. The D-21 had a range of over 3,000 miles while modern UAV's have ranges from under 200 miles to over 14,000 miles but using LH2 or Liquid Methane there would be no opportunity for air-to-air refueling, (and transferring cryogenic fluids has been shown to have issue and that's before the operational problems with working with the stuff in bulk) and internal storage and insulation, (hypersonic again) issues abound for a smaller airframe.Still the 'customer' has to be very upfront about such and willing to pay for it. Sensors, weapons bays, internal fuel storage will all have to specified UP FRONT so they can be included in the design as there won't be any way to 'retrofit' them once the vehicle is built. And all this has a very real possibility of not only the actual vehicle or engine not performing to specifications but that the 'added' requirements don't themselves cause the vehicle to fall short of requirements.Since the main 'question' is (obviously) does the SABRE live up to expectations AND if so what are its actual performance metrics IN FLIGHT I have very high confidence that no one will be willing to pay for anything likely to be 'useful' till after all that data is in. Now something 'based' on the FTV could eventually be pitched but keep in mind there will be certain and strict requirements that have to be met along the way.The most likely outcome is the FTV will be (as suggested by the "usual" aerospace contractors such as Boeing, BAE, etc) an expendable "test" vehicle on the line of the X-45/47 with each vehicle pushing the performance envelope along a series of 'goals' over the program. It's typical of such test programs today so it won't be either unexpected nor vastly difficult to pitch. On the other hand JS19 has a point that making it 'reusable' may in fact be both the better and 'simpler' option given the minimum size needed. But even a conversion of an existing airframe is going to be expensive and a 'scratch built' one probably out of the question. But you really DO want reusable despite the 'cost analysis' tending towards expendable since what you REALLY want to do is get data from the full spectrum of flight operations rather than just selected 'segments' which might induce errors or miss issues.Star One wrote:QuoteEvery other discussion I've seen regarding this recent deal online, and other past developments leading up to this outside of this forum has been in terms of its military application.Actually every time "hypersonics" is mentioned or written about the 'subject' turns to military applications which is different than what you're implying. Simply put, inserting "military applications" is a standard way to pad a subject that "might" actually have "military applications" whether the actual work being done IS directed towards that goal or not. Hypersonic flight has been specifically 'tied' to proposed "military applications" since the 1950s but actual versus assumed applications have been severely lacking and this is no different. SABRE, (which is the whole point of any test vehicle) is another, albeit rather better thought out, propulsion system that can possibly be used to push a vehicle to hypersonic speeds. Since it is possible for any vehicle to be used for 'military purposes', (and therefor used to pitch money from either the government or the military) such 'padding' is always inserted no matter if the actual application doesn't fit the suggested concept.Let's take a look at the ACTUAL "military applications" of the SABRE engine:1) It can be used to power a booster vehicle to launch expendable or reusable upper stages for vastly cheaper than current launch costs.Now 'suggested' applications tend to be:a) It can be used to power a bomber/fighter/recon aircraft flying at the edge of space and hypersonic, (Mach-6 to -10) speeds!Actually no since a 'fighter' by definition needs a propulsion system that can allow it to do its job which is engage and destroy enemy aircraft and flying at 100,000ft and Mach-6 to Mach-10 you can't see, identify, lock-onto and engage a target with any reasonable chance of success. Similarly a 'bomber' needs to find, identify and engage its target which while not moving, (generally in fact the main 'purpose' of a hypersonic bomber is supposed to be the ability to reach a target area before a MOVING target can move outside its engagement area) and destroy it. Anyone that thinks that a platform moving as hypersonic speed at an altitude of 100,000ft plus can do this 'easily' is sadly out of touch with the reality of weapons technology. (Or trying to get money which pretty much covers the majority of sources for such suggestions) So that leaves the reconnaissance role which actually has possibilities as long as you ignore the rather obvious problems with a super-fast, super high altitude very "visible" (both to radar and basic IR sensors) target that while it might spot targets that would normally avoid predictable satellite passes or low and relatively slow "normal" aircraft is both vulnerable and restricted on what information it can gather. How can something flying so high and fast be 'vulnerable'? It is flying 'high' so again it's a LOT more visible than something flying very low and very slow so its chances of being spotted are vastly higher and unfortunately even 100,000ft is not 'low' enough to "hide" behind the curvature of the Earth as has often erroneously been suggested. Barring flying against someone with only the "Mark-One Eyeball" you WILL be spotted and tracked. You're also vulnerable in that neither the speed or altitude are immune from aggressive interception.Further the SABRE cycle due to the inclusion of a rocket motor is vastly inferior for ANY hypersonic mission of any of the type given except launch vehicle when compared to vastly better cycles such as the Scimitar or other 'turbine' rather than 'rocket' based cycles. The 800-pound gorilla in the room everyone who focuses on 'military applications' for the SABRE is the fact it has ONE possible application and ONLY one: Launch Vehicle.So therefor, (it should be quite obvious) if the FTV is planned to use SABRE cycle engines then it actually has one 'possible' application and most likely it will therefore be used to PROVE the SABRE cycle itself and not some way to 'sneak' a military drone into production.QuoteBAE are the steering force now in this, their actual percentage is pretty irrelevant but it's big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isn't civilian.Actually DARPA does in fact do a lot of projects that while they 'may' have military applications in the future can and have found civilian applications in more near term time frames. Self-driving vehicles is one good example as that started as a DARPA sponsored program but was rapidly embraced and improved upon by civilian agencies. Also while DARPA is sponsoring some of the work the actual main interest is from the Air Force Research Laboratory which is specifically tasked with 'long term' research and not procurement or operations. This is on purpose because the last time DARPA tried to 'shortcut' a research program it not only failed to get to flight testing it failed to reach the level of 50 year old research and development that the DARPA researchers didn't know had already been done! (RASCAL and MIPCC) AFRL was one of the agencies that pointed out the cost models for the program were significantly lacking in basic data while the proposed 'research' areas had already been done and the suggested 'vehicle' was in no way a 'research' or 'test' model but a clear 'operational' vehicle with which DARPA was attempting to bypass standard procurement and contracting procedures. (Which in fact they were doing)Quotehttps://www.telegraph.co.uk/business/2018/04/12/reaction-engines-secures-boeing-rolls-royce-backing-hypersonic/Outside of that there's plenty of applications for the technology fully outside of the aviation field and I imagine they'd be both easier and quicker to exploit than a space vehicle. After all a lot of investors these days are looking for the quick return or the shortest route to a return which this seems to offer here.Nice of you to point out another article that fully and totally misses the main 'point' of its own information in order to pad the word count with nonsensical and non-relevant subjects. Point of fact where in that article can you find ONE "application" for the SABRE OTHER than as a launch vehicle? That is after all the ONLY application that is suggested or implied by those quoted in the article. Supersonic and hypersonic flight is 'suggested' as something that can be 'derived' from the SABRE cycle in the future a number of times but any connection with the SABRE FTV is inferred and not explicit by anyone quoted in the article. Wonder why that is?It's because the SABRE is not suitable for either supersonic or hypersonic "flight" and those being quoted are WELL aware of this fact. The engine that would power supersonic or hypersonic aircraft, (note not "spacecraft" which is what the SABRE is stated to be used for in the article) is the Scimitar which is optimized and designed for just such applications and does the job VASTLY better than the SABRE.I think one thing that people seem to ignore is due to its nature SABRE powered vehicles simply can NOT fly from ANY 'standard' airport anywhere in the world. Not even 'lightly loaded' or 'partially fueled' and REL has pointed this out several times. It has nothing to do with runway length or loading or any of the other "operational" issue that have been discussed but directly due to the fact it uses a rocket engine in its design. It can't fly from an standard airport because it is impossible for it to meet the noise regulations of any standard airport. Period.Scimitar CAN do so and is specifically designed to do so and meet ALL regulations and guidelines.And lets discuss the applications outside the aviation industry which can be so lucrative...Point of fact REL has a nice heat exchanger technology but as was pointed out back when they were trying to hype it, (and SABRE) up to get investment it is highly specialized and has few if any applications outside the ones REL has in mind. Granted if they exist you can be sure BAE will exploit them but really that has nothing to do with the thread. Still if you'd like to list them we can disassemble them again I suppose.Phillip Clark wrote:QuoteHas anyone considered asking Reaction Engines about this? I am sure that Alan Bond would tell, if he's able to.And deprive ourselves of the possibly of vastly speculative and argumentative postings? What are you? Mad? I mean look how boring and mundane BFS turned out to be compared to our ideas and concepts, come on loosen up some Some additional comments on the D21 design:Note the LOX tank was wrapped around the 'duct' not the actual engine. Even at Mach-6 the heating wasn't going to be really 'bad' and there was insulation. But in any case, (Liquid Methane or LH2) is going to require a larger tankage and not be compatible with 'wet-wings' normally. (You have to admire the way they got 'away' with "wet-wings" cyro-LOX in the Star-Raker design though: http://www.alternatewars.com/SpaceRace/Star_Raker/Star_Raker.htmhttps://motherboard.vice.com/en_us/article/ezvj4j/the-747-to-space-that-never-washttps://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790010900.pdf (page 73)Having said that since you don't actually NEED to put propellant in the wings, and at hypersonic speeds "wings" aren't really needed there would be tendency to move towards a lifting fuselage body similar to the "waverider" and advanced aircraft we've been working on the last 50 years. Now with that as pointed out with the D-21 you DO need wings at lower speeds so unlike NASP and some of the more extreme designs you want good low speed landing wings. On the other hand if you don't assume that you have to squeeze every ounce of efficiency out of the propulsion, (Skylon doesn't, whereas most of the others DO and therefore the engines and fuselage are designed to synergistically support each other) then you can consider other options for engine placement. (I should note the ENTIRE fuselage is synergistically used so that the forward body helps compress and ingest the air while the after body helps align and expand the exhaust for more efficient operation)Again this isn't 'lazy' on REL's part but it greatly simplifies the figures you need to play with since with the engines on the wingtips reduces some of the aerodynamic and weight-and-balance problems. (Of course you get a similar effect without the "engine-out" issues by putting the engine near the center of the airframe, again which is common on engine/body designs) I suppose the main question is how small can they make a SABRE engine?Randy
I recall the rocket powered vehicles were actually more like aerodynamic test vehicles rather than an engine/cycle test vehicle which is what the current "FTV" seems to be aimed at. (Speaking of how about some links to past and present concepts, test goals, and other information?)
Nice find on the DRACO/D-21 having something to build on would help with the costing as even a subscale demonstrator is going to be expensive. (Despite what the cited studies actually "say" I'll note that they both include the verbiage "only vehicle designed to attain/maintain hypersonic speeds" which is wrong as the D-21 never came close to Mach-5 which is the actual boundary of "hypersonic" speed) I suppose the first question is what exactly are they trying to 'test'?
1) If they want to test the airframe design, (which I'm doubting as we've already seen the details differ from one company or group to another) then whatever is used will be designed around both the engines and the airframe and an integration of the two. Being's Boeing is onboard I highly doubt it will look like the Skylon we're used to from REL.
2) If they want to flight test the engine/cycle/system , (much more likely) then the airframe doesn't matter as much though the higher the testing speeds the more the design will want to "close" towards an approximation of "real" design. But initially you want to demonstrate a series of tests along a spectrum of speed if not to 'full' capability then at least to certain significant test points. For example such test points could include; Take off, climb, acceleration, ability to perform subsonic/transonic/supersonic and back transitions, accelerate to a 'maximum' speed, decelerate back through transonic and return to land, (or be recovered) and then do it all over again multiple times. (Note switching between air-breathing and pure rocket mode at various points will be a requirement so it will have to haul a LOX tank around as you suggest )
As noted in the reports the D21 doesn't have very good low speed handling qualities so it would probably need modification to the wings to provide such. You're also going to have to install landing and possibly take off gear.
If you are 'just' wanting to test the engine at various flight speeds then it might be better to pull a page from history and use a much simpler and more robust design type which while you'd have to 'build' can in fact be pretty straight forward AND cost effective. You can't really go wrong with something along the lines of the Lockheed X7 (https://en.wikipedia.org/wiki/Lockheed_X-7) ramjet test vehicle, which I will note CAN hit hypersonic speeds. (Late model drones topped out very near Mach-5 {and with a better engine could have done so) Given the SABRE T/W launch can be from a rail and landing kept 'simple' by keeping the parachute and "spike" from the original. Granted dimensions would have to be larger but it's certainly an option.
Lastly there is the "existing aircraft airframe" conversion option. Not that I can see a Learjet outfitted with a pair of 'mini-SABRE's' but conversions have been made of several supersonic aircraft by many nations with some of the US ones being "Q" series versions of the F-106, F4, and F-16 and of course there are 'sale' versions of the T-38, F-106, F-104 and others.Finding and converting an Starfighter might be an good option as it's a bit bigger than the D-21 and if suitably braced you might be able to mount "mini-SABRE's" in place of the wingtip tanks and utilize the full capacity of the fuselage.
Of course having said all the above IF the various contractors can find someone to 'pay' for it most of them (Boeing, BAE, etc, frankly probably everyone BUT REL ) might prefer to 'build-from-scratch', especially if that 'customer' is a government. And while I DO agree the initial test vehicle won't have an obvious or "built-in" Military Operational Capability and disagree with Star One that there is any "obvious" bias towards having such in a "test" vehicle simple because who's interested and who's building it the fact is such a vehicle 'could' have a secondary purpose IF built to certain specifications. It's that last part that will be telling because I recall that the original (AF driven) specifications for the X-33 program were in fact quite interesting, especially given the launch and landing locations chosen for the program.
(Launch from Edwards AFB towards a facility in Utah, Speed in excess of Mach-12 and 'several hundred pounds' of "test instruments" in a long narrow bay... At the time it was noted by several people the 'test instrument bay' could hold a STAR solid motor and a microsatellite as 'payload' after all ) And while Star One is kind of obsessed with "hypersonic strike" missions the ACTUAL most likely mission is frankly as an advanced D-21 system for a reconnaissance drone. (Any 'weapon' has to be deployed from the inside of the vehicle mind you and THEN transition through a Mach-5+ shockwave AND still remain aimed at the target all of which is VERY difficult. And since it can't mass more than 2,000lbs at most it has to be highly accurate so obviously guided and everything has to be able to stand up to hypersonic speeds since that's when it's launched. As we've not developed any that work yet...) And for that you'd need specialized sensors, environmental conditioning equipment, (hypersonic speeds remember) power and others which will amount to something on the order of several hundred to maybe a thousand pounds. (Remember also you're flying at hypersonic speeds at almost 100,000ft so "OTS" sensor won't work) And then there's the 'range' question. The D-21 had a range of over 3,000 miles while modern UAV's have ranges from under 200 miles to over 14,000 miles but using LH2 or Liquid Methane there would be no opportunity for air-to-air refueling, (and transferring cryogenic fluids has been shown to have issue and that's before the operational problems with working with the stuff in bulk) and internal storage and insulation, (hypersonic again) issues abound for a smaller airframe.
Still the 'customer' has to be very upfront about such and willing to pay for it. Sensors, weapons bays, internal fuel storage will all have to specified UP FRONT so they can be included in the design as there won't be any way to 'retrofit' them once the vehicle is built. And all this has a very real possibility of not only the actual vehicle or engine not performing to specifications but that the 'added' requirements don't themselves cause the vehicle to fall short of requirements.
Since the main 'question' is (obviously) does the SABRE live up to expectations AND if so what are its actual performance metrics IN FLIGHT I have very high confidence that no one will be willing to pay for anything likely to be 'useful' till after all that data is in. Now something 'based' on the FTV could eventually be pitched but keep in mind there will be certain and strict requirements that have to be met along the way.
The most likely outcome is the FTV will be (as suggested by the "usual" aerospace contractors such as Boeing, BAE, etc) an expendable "test" vehicle on the line of the X-45/47 with each vehicle pushing the performance envelope along a series of 'goals' over the program. It's typical of such test programs today so it won't be either unexpected nor vastly difficult to pitch. On the other hand JS19 has a point that making it 'reusable' may in fact be both the better and 'simpler' option given the minimum size needed. But even a conversion of an existing airframe is going to be expensive and a 'scratch built' one probably out of the question. But you really DO want reusable despite the 'cost analysis' tending towards expendable since what you REALLY want to do is get data from the full spectrum of flight operations rather than just selected 'segments' which might induce errors or miss issues.
Star One wrote:QuoteEvery other discussion I've seen regarding this recent deal online, and other past developments leading up to this outside of this forum has been in terms of its military application.Actually every time "hypersonics" is mentioned or written about the 'subject' turns to military applications which is different than what you're implying. Simply put, inserting "military applications" is a standard way to pad a subject that "might" actually have "military applications" whether the actual work being done IS directed towards that goal or not. Hypersonic flight has been specifically 'tied' to proposed "military applications" since the 1950s but actual versus assumed applications have been severely lacking and this is no different. SABRE, (which is the whole point of any test vehicle) is another, albeit rather better thought out, propulsion system that can possibly be used to push a vehicle to hypersonic speeds. Since it is possible for any vehicle to be used for 'military purposes', (and therefor used to pitch money from either the government or the military) such 'padding' is always inserted no matter if the actual application doesn't fit the suggested concept.Let's take a look at the ACTUAL "military applications" of the SABRE engine:1) It can be used to power a booster vehicle to launch expendable or reusable upper stages for vastly cheaper than current launch costs.Now 'suggested' applications tend to be:a) It can be used to power a bomber/fighter/recon aircraft flying at the edge of space and hypersonic, (Mach-6 to -10) speeds!Actually no since a 'fighter' by definition needs a propulsion system that can allow it to do its job which is engage and destroy enemy aircraft and flying at 100,000ft and Mach-6 to Mach-10 you can't see, identify, lock-onto and engage a target with any reasonable chance of success. Similarly a 'bomber' needs to find, identify and engage its target which while not moving, (generally in fact the main 'purpose' of a hypersonic bomber is supposed to be the ability to reach a target area before a MOVING target can move outside its engagement area) and destroy it. Anyone that thinks that a platform moving as hypersonic speed at an altitude of 100,000ft plus can do this 'easily' is sadly out of touch with the reality of weapons technology. (Or trying to get money which pretty much covers the majority of sources for such suggestions) So that leaves the reconnaissance role which actually has possibilities as long as you ignore the rather obvious problems with a super-fast, super high altitude very "visible" (both to radar and basic IR sensors) target that while it might spot targets that would normally avoid predictable satellite passes or low and relatively slow "normal" aircraft is both vulnerable and restricted on what information it can gather. How can something flying so high and fast be 'vulnerable'? It is flying 'high' so again it's a LOT more visible than something flying very low and very slow so its chances of being spotted are vastly higher and unfortunately even 100,000ft is not 'low' enough to "hide" behind the curvature of the Earth as has often erroneously been suggested. Barring flying against someone with only the "Mark-One Eyeball" you WILL be spotted and tracked. You're also vulnerable in that neither the speed or altitude are immune from aggressive interception.Further the SABRE cycle due to the inclusion of a rocket motor is vastly inferior for ANY hypersonic mission of any of the type given except launch vehicle when compared to vastly better cycles such as the Scimitar or other 'turbine' rather than 'rocket' based cycles. The 800-pound gorilla in the room everyone who focuses on 'military applications' for the SABRE is the fact it has ONE possible application and ONLY one: Launch Vehicle.So therefor, (it should be quite obvious) if the FTV is planned to use SABRE cycle engines then it actually has one 'possible' application and most likely it will therefore be used to PROVE the SABRE cycle itself and not some way to 'sneak' a military drone into production.
QuoteBAE are the steering force now in this, their actual percentage is pretty irrelevant but it's big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isn't civilian.Actually DARPA does in fact do a lot of projects that while they 'may' have military applications in the future can and have found civilian applications in more near term time frames. Self-driving vehicles is one good example as that started as a DARPA sponsored program but was rapidly embraced and improved upon by civilian agencies. Also while DARPA is sponsoring some of the work the actual main interest is from the Air Force Research Laboratory which is specifically tasked with 'long term' research and not procurement or operations. This is on purpose because the last time DARPA tried to 'shortcut' a research program it not only failed to get to flight testing it failed to reach the level of 50 year old research and development that the DARPA researchers didn't know had already been done! (RASCAL and MIPCC) AFRL was one of the agencies that pointed out the cost models for the program were significantly lacking in basic data while the proposed 'research' areas had already been done and the suggested 'vehicle' was in no way a 'research' or 'test' model but a clear 'operational' vehicle with which DARPA was attempting to bypass standard procurement and contracting procedures. (Which in fact they were doing)
Quotehttps://www.telegraph.co.uk/business/2018/04/12/reaction-engines-secures-boeing-rolls-royce-backing-hypersonic/Outside of that there's plenty of applications for the technology fully outside of the aviation field and I imagine they'd be both easier and quicker to exploit than a space vehicle. After all a lot of investors these days are looking for the quick return or the shortest route to a return which this seems to offer here.Nice of you to point out another article that fully and totally misses the main 'point' of its own information in order to pad the word count with nonsensical and non-relevant subjects. Point of fact where in that article can you find ONE "application" for the SABRE OTHER than as a launch vehicle? That is after all the ONLY application that is suggested or implied by those quoted in the article. Supersonic and hypersonic flight is 'suggested' as something that can be 'derived' from the SABRE cycle in the future a number of times but any connection with the SABRE FTV is inferred and not explicit by anyone quoted in the article. Wonder why that is?It's because the SABRE is not suitable for either supersonic or hypersonic "flight" and those being quoted are WELL aware of this fact. The engine that would power supersonic or hypersonic aircraft, (note not "spacecraft" which is what the SABRE is stated to be used for in the article) is the Scimitar which is optimized and designed for just such applications and does the job VASTLY better than the SABRE.I think one thing that people seem to ignore is due to its nature SABRE powered vehicles simply can NOT fly from ANY 'standard' airport anywhere in the world. Not even 'lightly loaded' or 'partially fueled' and REL has pointed this out several times. It has nothing to do with runway length or loading or any of the other "operational" issue that have been discussed but directly due to the fact it uses a rocket engine in its design. It can't fly from an standard airport because it is impossible for it to meet the noise regulations of any standard airport. Period.Scimitar CAN do so and is specifically designed to do so and meet ALL regulations and guidelines.
And lets discuss the applications outside the aviation industry which can be so lucrative...Point of fact REL has a nice heat exchanger technology but as was pointed out back when they were trying to hype it, (and SABRE) up to get investment it is highly specialized and has few if any applications outside the ones REL has in mind. Granted if they exist you can be sure BAE will exploit them but really that has nothing to do with the thread. Still if you'd like to list them we can disassemble them again I suppose.Phillip Clark wrote:QuoteHas anyone considered asking Reaction Engines about this? I am sure that Alan Bond would tell, if he's able to.And deprive ourselves of the possibly of vastly speculative and argumentative postings? What are you? Mad? I mean look how boring and mundane BFS turned out to be compared to our ideas and concepts, come on loosen up some
Some additional comments on the D21 design:Note the LOX tank was wrapped around the 'duct' not the actual engine. Even at Mach-6 the heating wasn't going to be really 'bad' and there was insulation. But in any case, (Liquid Methane or LH2) is going to require a larger tankage and not be compatible with 'wet-wings' normally. (You have to admire the way they got 'away' with "wet-wings" cyro-LOX in the Star-Raker design though: http://www.alternatewars.com/SpaceRace/Star_Raker/Star_Raker.htmhttps://motherboard.vice.com/en_us/article/ezvj4j/the-747-to-space-that-never-washttps://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790010900.pdf (page 73)
Having said that since you don't actually NEED to put propellant in the wings, and at hypersonic speeds "wings" aren't really needed there would be tendency to move towards a lifting fuselage body similar to the "waverider" and advanced aircraft we've been working on the last 50 years. Now with that as pointed out with the D-21 you DO need wings at lower speeds so unlike NASP and some of the more extreme designs you want good low speed landing wings. On the other hand if you don't assume that you have to squeeze every ounce of efficiency out of the propulsion, (Skylon doesn't, whereas most of the others DO and therefore the engines and fuselage are designed to synergistically support each other) then you can consider other options for engine placement. (I should note the ENTIRE fuselage is synergistically used so that the forward body helps compress and ingest the air while the after body helps align and expand the exhaust for more efficient operation)
Again this isn't 'lazy' on REL's part but it greatly simplifies the figures you need to play with since with the engines on the wingtips reduces some of the aerodynamic and weight-and-balance problems. (Of course you get a similar effect without the "engine-out" issues by putting the engine near the center of the airframe, again which is common on engine/body designs) I suppose the main question is how small can they make a SABRE engine?
The X7 airframe is great to begin with: simple and straightforward to mount a test engine, optimized for top speed at M4+ (even with aerodynamics of 1950s).
X7B have dual engines below wigs, resembling subsequent operational BOMARC missile with the same Marquardt RJ43 ramjets. BOMARC is optimized for balance between speed, range, and climbing ability after ground launch.
Eventually came the D21 with a special version of RJ43 optimized for long range cruise. The reasons for D21 to have a SR71 style flat lifting body are basically range and radar stealth, not top speed.
Having LH2 tanks around the engine is seeking trouble for a test vehicle.
I suggest you read any history of DARPA before suggesting they do anything civilian, if they do it's accidental rather intentional.
I think the key thing for the Methane rocket version was inlet development. The "Peace Jack" programme showed what a big difference you could get with a better (and bigger) inlet on a conventional turbojet.
Links? Hmm. Only a few REL presentations mention the idea in any detail. They were also looking at a kind of sounding rocket using IIRC LO2/LNH3/LN2 to simulate the combustion and trajectory.
I think people are making a lot of the Boeing involvement but this is the VC arm of Boeing. I'm not sure how much 2 way interaction happens between them and the actual aircraft building parts (either military or civilian). Of course as a potential customer it would good to get their input (provided it can be done in a non ITAR contaminating way of course).
Exactly. It's pretty clear that a lot of people simply won't believe a vehicle and engine can fly this trajectory until one does (although they seem to have no trouble believing a SCramjet will do whatever its promoters claim it will ) Therefor that needs to be the key goal.
Actually they dug up the top aerodynamics guy at the time and he said they never tested the shape for low speed handling. No point. It's never going to land. TBH that's probably the case for any existing shape.
Looking at the D-21's internal structure what struck was how SR71 it was. Basically, take an SR71, chop off the wings past the engine nacelles (and the nacelles themselves), then core out the fuselage and stick the ramjet in there. No doubt it was considerably more subtle than that but that's the high level view I got.
Now this works better. When this Idea came up I was thinking more of the V-1 but with proven high Mach flight to go on... My instinct is LH2 storage is going to be the big issue for any test design. A design that gives you a solid centre body to put an LH2 tank inside seems easier. Of course if you goal is to demonstrate "mad design skillz" then the LH2 wet wing is definitely the way to go. But there's a very fine line between mad skillz, and just plain mad.
IIRC HMX was involved with MIPCC and said they could get their hands on a couple of F106's, which had a pretty big weapons bay. They reckoned with upgraded leading edges it could hit M5. Junking all that 1950's era SAGE computer hardware should've lightened it up considerably.
I think this is the issue with adapting existing designs. No existing design (except the X-15, X37b and Shuttle) were designed to fly above roughly M3.5. True they wouldn't have to last long (for engine and trajectory test get up to the right altitude/speed, switch over and get stable combustion in rocket mode. 10s of seconds after transition?) but it's a gamble. And you'd probably need a pilot as well.
Agreed. But now you have 2 goals.1) Build a vehicle that can test the engine/inlet over its planned Mach and altitude range2) Design it as a pre-production prototype for an actual vehicle with a specific purpose.
One of the ways APD said they cut development costs by 1/3 was not to include support for things like reparability or maintainability. The language is quite important. It's a demonstrator, not a prototype.
The X-33 programme should have taught people what happens when you make one vehicle do both. You end up with no vehicle and no improvement in your ability to design one, unless you count "Designing multi lobed conformal composite LH2 tanks is hard." Did it really need a $1.5Bn programme to "discover" this?
OTOH setting aside some resources in the design (details TBD in discussion with interested parties) would give a resource other groups could use as a "flying laboratory" once it'd proved SABRE can do what they claim it can do. REL recovers some costs, the groups get access to the first reusable hypersonic test vehicle in 50 years. Everyone wins.
The "demonstrator" becomes essentially a "prototype" and the costs go up 10x (or more)?I really hope REL management don't go down this road. It ties so much that is completely irrelevant to the engine/inlet demonstration. Fly the engine over as much of the trajectory as possible. Show it works with the inlet design. Show it can do AB/rocket transition to stable combustion. All else is nice to have
I hope not, but aerospace contractors can be very persuasive when they have something that could (sort of) plausibly meet a long held desire. That's basically how NASP sank close to $3Bn. The PI told a really good story. Which in the end was exactly what it turned out to be.
I wonder if anyone's counted up how many of those hypersonic programmes demonstrators there have been, along with a)How many of them failed in flight with little or no data gathered?b)How many of the programmes delivered all the data they promised by the end?
I came across a NASA study (didn't copy it) that had a diagram of a M8 passenger aircraft (SCramjet naturally) and its temperatures. Most of it was 800-1000c with the nose at 2200c.Now where can REL find a jobbing shop that does Titanium, superalloys or ceramics?
Expendability means everything on every flight is a one-shot deal. That sounds a great deal for the contractors, not so good for the customers. One of SABRE's goals is T/W ratio of about 14:1, about 7x (or at least 3.5x)better than any SCramjets I'm aware of. How does that affect the reusability/expendability calculation?
As NASA noted, plume heating is one of the "known unknowns." Yes, it would be nice to get a jump on scoping how serious an issue (is it an issue?) this is. But for now just getting something into the air seems adequately ambitious enough to me.
This being a UK project I think the question is "how small can they make a SABRE engine affordably?"
The recording of the BIS meeting from the head of the TF1 test stand project said the test engine is basically a SABRE 4 engine but with "1 of everything."previous posters on that thread mentioned that SABRE is roughly a 4 segment pre-cooler, dual LOX pump, dual LH2 pump engine. So logically the test engine will be 1 pre cooler segment, 1 LOX, 1LH2 pump. The LH2 pump is from the Ariane programme, but REL remain coy about wheather it's from a Vulcain or a Vinci engine. The former is way too big for the test stand (and still too small for the full Skylon sized SABRE) and the latter is a little undersized, but probably has enough margin to cope. The implication is you just need to make multiple copies of those parts to upscale to a full Skylon sized SABRE. The joker is the LHe circulator which they describe as OTS, so probably too heavy for flight. There aren't too many uses for these outside of a)Air separation plants and b) Some high temperature nuclear reactors. By the end of the test programme I expect they will have a much better idea of what the issues of building one in house will be to meet the Skylon weight budget.
And more sophisticated don't forget The intake design had a series of internal segments to help handle the changing airstream as it went along. IIRC the work also spawned a suggested version of the F4 that had variable intakes similar t that of the F-15 for the same reason.
I was hoping for some 'new' and possibly more detailed information but ah well
We tend to make a lot about Boeing because they are clearly an "airframe" manufacturer whereas BAE isn't as 'big' a name at this time. Mostly Boeing "VC" arm is there to invest in "interesting" technology that Boeing wants to keep abreast of but not enough to take on internal spending and effort. On the other hand if this propulsion system tests out then they will have a 'foot' in the door as it were. IIRC Airbus was considering a similar effort but I don't recall if they actually put anything into it. Yet...
Given how much Scramjet hasn't yet lived up to the hype... And then there's the significant inertia of the concept of 'air-breathing' rocket engines that don't 'need' to have the air turned to a liquid first. Granted the information was THERE even in the late 50s but the 'institutional thinking' was stuck on LACE despite the subcontractors noting it wasn't true. (Then again consider the 'statement' saying such seems to have amounted to a couple of sentences in the general summery of work done and no attention was called to it...)
Conversely the 'idea' of 'deep-cooled' turbojets AND LH2 rockets on the same airframe have been suggested many times but the fact they are two separate systems always shows degraded performance. Even 'combined cycle' systems with everything integrated STILL showed the rocket and air-breathing being 'fed' seperatly. So ya there is a need to "show" it works in the real world and not just that the math works. ('cause Scramjet math has ALWAYS worked so getting them flying is "simply" an engineering problem right? )
And if need be use a parachute but I'll point out that one aspect this is SUPPOSED to test is flight from 'launch' to high mach which you'd think is going to be at LEAST subsonic. And with that amount of effort I'd probably shoot for a shape that can be used for full range testing. In the D-21 case I suspect since you'd have to rebuild the wings and leading edges anyway they could 'fix' the low speed handling since you're working your way UP in speed anyway.
Probably not THAT much more subtle considering how much effort went into the aerodynamic of the SR. After all there's good reason to go with a 'known' shape for approximately the same job Which is why the RATTLRS looks the way it does
Well to be honest the PRIMARY reason I recalled the X-7 was the mental picture of the FTV with its nose spike stuck in a huge "target" labled "It will never work" and the subtitle "Nailed it!" but that's just me...
Figuring the 'fuselage' design and construction can piggyback off what REL has already done is worth some thought. The biggest difference is the single engine close to the body but given the design you have less 'shock-impingement' issues to deal with.
I think MLorry was the one pushing the F106, and there was a group of F106 fans that submitted a plan to use them but it was rejected by DARPA because it was 'too small' for the 'required' payload. (Which was when it became a 'suspicion' that this wasn't a 'research' project... The other hint was numerous articles from the lead scientist about how the 'operational' system would work)
Well Northrup DID suggest a redesign of the T-38 into an 'aerospace' trainer that could hit Mach-3.3 and over 200,00ft:http://ghostmodeler.blogspot.com/2012/09/talons-in-space-northrops-n-205-proposal.htmlAnd of course the NF-104:https://en.wikipedia.org/wiki/Lockheed_NF-104ABut anything would take a large amount of work to use I agree, so starting from scratch might be more practical. Needing a 'pilot' is going to be a design decision as you can, (we've been doing it since radio control was invented) make a drone out of anything.
And that's often exactly the case with either or both contractor/customer overreach on a design (About even which one does the 'overreach' and more often than not is can be mutual : ) ) Frankly even if it IS a 'pure' test vehicle contractors will tend to 'suggest' it can be turned into an operational vehicle with "just a bit" more money and effort. More often than not this doesn't work BUT...
The 'problem' though is that can often lead to asset being even "cheaper" (by creative accounting) if it is expendable in every test. As far as I can tell EVERY Scramjet "demonstrator" has been expendable for that very reason so the 'logic' is obviously compelling. On the other hand IF the vehicle IS reusable then the "logic" of some sort of operational or "long-term" research program use is just as compelling. Again pointing to the X-7, it was an engine and aerodynamic data test vehicle and very good at both for its time. That didn't stop it being pitched as everything from a supersonic target drone to a recon or attack missile. None of which it was very good at and something which a 'point' design did better.
Then there is the X-15 which was never 'planned' to be anything but a test vehicle. (Though the Douglas design was in fact more 'aimed' at a possible 'operational' follow on for the Navy even though they frankly had no clue what they'd use it for) That didn't stop North American from proposing all sorts of projects with the basic and advanced versions of the airframe. They key is both the X7 and X-15 were designed and used for the job they were made for and any "other" tasking was going to take some (in many cases significant) redesign and rebuilding. Hence they DID the job they were designed for and while possibly could have been used for other purposes in the end it would take time and money to do so.
Actually there were a lot of lessons learned from the overall program, (a couple of the big ones being listen to your sub-contractors when you supposedly hire them for their expertise, and don't assume you can do something radically difficult when the people you hire are TELLING you it's radically difficult simply because you have a history of doing so, you can't win every time) but the ONE the was NOT learned, (even though it is often touted as "proof") is that SSTO or low-cost access is not possible. Similarly "lessons learned" from the NASP program include not making the whole program dependent on a single technology that at the time hadn't worked outside a laboratory and the risks of program bloat and unrealistic expectations. Yet the most often cited "lesson" is usually that "air-breathing propulsion" has no place in space launch without a shred of actual 'proof' to support it.
More often than not the actual "lessons" versus the assumed "lessons" are more directed towards bias's and desired outcomes than what was really learned. Never forget the biggest obstacle that any new idea has to overcome is the fallacy of "If it worked someone would have done it by now"
QuoteOTOH setting aside some resources in the design (details TBD in discussion with interested parties) would give a resource other groups could use as a "flying laboratory" once it'd proved SABRE can do what they claim it can do. REL recovers some costs, the groups get access to the first reusable hypersonic test vehicle in 50 years. Everyone wins.In theory anyway
Keep in mind that REL may have little or no input on the matter. To be honest they are really just the 'engine contractor' and most everything else is going to be what the rest of the consortium decides. All the more reason to push for essentially an flying engine test bed and not much else.
NASP suffered (a LOT) from hypersonic and Scramjet advocates finally getting access to an 'blank check' with little or no oversight or actual understanding of the challenges by those who were supposed to provide the oversite. And the advocates not only didn't try to stop the spiral they egged it on by adding "requirements" specifically to drive the program into certain directions no matter the TRL of the technology needed. Frankly the INITIAL program of a hypersonic, (up to mach-10) demonstrator was a good idea but once the whole program became dependent on a single propulsion system and the 'goal-post' of flight speed began to creep up the whole thing was doomed.
The 'figures' are available and with enough creative accounting they will tell what every result you want them to
Seriously MOST programs have been 'successful' to some degree and few research programs deliver "all" the data they promise in the end. Take the X-15 for example. Almost 200 flights and in the end it only barely 'touched' the 'promised' speed levels, (the program was literally based on gaining "hypersonic" data which meant above Mach-5 and it was severely damaged at those speeds) and only about half its altitude goals.
"Most" Scramjet tests simply list "positive thrust achieved" or that the vehicle was 'accelerated' but neglect to provide actual figures. Which is because when they do the "acceleration" and/or "thrust over drag" is miniscule at best. Sure it CAN accelerate something to much higher speeds EVENTUALLY but probably not before it runs out of fuel. Sure you got a "Scramjet" to burn at Mach-5 to 7 but you've done that in a lab and in 'real-life' it has little utility if any. So why use a Scramjet when a rocket will actually do better?
I'd be surprised if it wasn't using 'heat-pipes' to the fuel for a heat sink
Yes it means everything is 'expended' on each flight but the calculations often show that's less costly over a few flights than making it reusable. We've seen the 'math' before with ELV versus RLV so it obviously "makes sense" at some point. T/W probably isn't a metric at all since there are expendable turbojets and rocket motors. The main 'metric' I assume is how many flights are planned, (and what kind of flight program overall) against the cost of an few (less costly) expendable vehicles versus a few (more costly) reusable ones. This is where the question becomes 'gray' because if your only testing a few key areas, (actual versus projected T/W, transition and stable combustion for example) then it might make sense to fly only a couple of mission to those specific points which would lean towards expendable. On the other hand if you want to get a complete data set from subsonic through hypersonic then it may make sense to build a couple of reusable flight vehicles for more upfront money.
Part of the problem of looking for 'other users' is frankly it's probably questionable if anyone else would 'need' the capability AND if the vehicle flight parameters (or the flown test parameters) may not adversely affect each other. (Example is the X-15 and the dummy Scramjet) The suborbital and micro-payload "markets" aren't that obvious and the temptation is to make a sub-scale 'demonstrator' (if you go the reusable route) that might be capable of delivering an upper stage and payload to orbit (Cube or micro-sat size) JUST because you're already making a 'demonstrator' in the first place.
Oh I agree but that does feed back into the expendable/reusable equation. And the design, and the engine placement, and.. Well you get the picture
Well that IS the reason you reach out to moneybag.. er that is the US right?
And really that's the whole nutshell right there. You probably NEED to flight test some type of engine to get an idea of what works subscale, what doesn't and what you can podge together to get it to work. The big risk is if you don't get it right then it may not work and then the whole concept is circular-filed as 'not-working' when it was actually a question of design. This is the stuff that keeps designers awake at night and causes ulcers but it's also a point your kinda of 'happy' to have gotten to.
Let's be clear. The FTV relies on SABRE. Propulsion has always been the key issue. Or rather, the insistance by the US hypersonic community that only SCramjets can meet the speed and the Isp requirements. It's interesting to consider what would be flying today if they had not become infected with this particular meme. :-(. SCramjet advocates seem to be saying a) "Convetionl ramjet fuel consumption deteriorates badly above M5 and b) You have to factor in all the free reaction mass in the air.Given SCramjet T/W is pretty poor that acceleration had better be phenomenial to make up for it, and it doesn't sound like it is. Not to mention the only reliable SCramjet test vehicle for a full size SCramjet is another full size SCramjet vehicle. :-( .
The 'problem' though is that can often lead to asset being even "cheaper" (by creative accounting) if it is expendable in every test. As far as I can tell EVERY Scramjet "demonstrator" has been expendable for that very reason so the 'logic' is obviously compelling. On the other hand IF the vehicle IS reusable then the "logic" of some sort of operational or "long-term" research program use is just as compelling. Again pointing to the X-7, it was an engine and aerodynamic data test vehicle and very good at both for its time. That didn't stop it being pitched as everything from a supersonic target drone to a recon or attack missile. None of which it was very good at and something which a 'point' design did better.Then there is the X-15 which was never 'planned' to be anything but a test vehicle. (Though the Douglas design was in fact more 'aimed' at a possible 'operational' follow on for the Navy even though they frankly had no clue what they'd use it for) That didn't stop North American from proposing all sorts of projects with the basic and advanced versions of the airframe. They key is both the X7 and X-15 were designed and used for the job they were made for and any "other" tasking was going to take some (in many cases significant) redesign and rebuilding. Hence they DID the job they were designed for and while possibly could have been used for other purposes in the end it would take time and money to do so.
Many people have waited half their lives to see a SCramjet (but not conventional ramjet) before X-43. They need the process (up to X aircraft), not the outcome (to end user). Cancelling SCramjet programs to fund convential ramjet are UNFAIR to them.
Optimizing ramjet technology is even not the RESPONSIBILITY of NASA, but one (of many) choice of defence contractors while defining their products. To go faster? to go smarter and more silent?
Similar situation above applys to SABRE/Skylon vs. optimized SR71 style turboramjet with Inconel airframe. The latter could certainly go beyond M5, but choosing payload to get PAID is another story.
Interesting to note the X-43 was a pure research program conducted by a tiny team of ex-X30 engineers, not too different from REL as ex-HOTOL engineers. https://www.amazon.com/Road-Mach-10-Lessons-Research/dp/156347932X
For structure surviveability, airframe design of D-21 with Inconel material of X-15 should be capable of going to speed near X-15.
Also the limitations of airframe is not the limitations of ramjet, you can use any airframe proposed for SABRESkylon demonstrator and fit in a turboramjet.
X-51 was designed or at least shaped and pitched as a missile demonstrator. However after flight tests, interest for scramjet missiles in US ceased, including DMRJ and TTRJ programs of OrbitalATK.
For structure survivability, airframe design of D-21 with Inconel material of X-15 should be capable of going to speed near X-15.
Also the limitations of airframe is not the limitations of ramjet, you can use any airframe proposed for SABRE/Skylon demonstrator and fit in a turboramjet.
Katana wrote:I fully understand that people have been 'waiting' for flying Scramjets for 'half-their-lives' and somewhat sympathize but I'll point out while it might SEEM 'unfair' to have their test programs canceled in favor a more proven technology, (and note I and JS19 don't appear to be arguing out-right cancelation but cutting back in favor of broader research and development, exactly the OPPOSITE of what the Scramjet advocates have been pushing for 'half-their-lives') those same people have rather unfairly dedicated their time and effort (lives if you will) to ensuing that the majority of funding, support and effort have in fact been spent on Scramjets to the detriment of any other propulsion scheme.
The thing was, at the time, it was felt that you could not achieve supersonic combustion in a 'ducted' system so there was no incentive to work within the typical 'ramjet' ducting. Something most Scramjet advocates seem to forget that INITIALLY propulsion by "supersonic combustion" was not even the idea behind the researched and developed. It was all about the possible lift the could be generated at very high altitudes and speeds. (Getting to that point either with 'conventional' turbojets/ramjets or rockets mostly) Dumping some fuel into the supersonic airstream would generate lift factors at 100,000ft equivalent to those at 40,000ft per area of lift. What little 'propulsive' effect that could be generated MIGHT offset the drag factors of some 'simple' ducting (short sections of duct offset from the fuselage or wing surface) or the drag-shocks formed by the propellant injection itself but that was about it.
That's STILL 'about it' today as the Scramjet has not proven to be the 'accelerator' engine it's been touted to be. The thing is the 'advocates' still refuse to consider and have in many cases actively fought research and development in any other propulsion system OTHER than Scramjet even when such was specifically directed at a near-or-operational system rather than 'research' work.
Let's be honest, the X-51 was disappointing managing at best to go from Mach-4.8 (booster burn out) to only Mach-5.1 and unable to accelerate further before it ran out of fuel. Such a vehicle being 'pitched' in any form as a "missile demonstrator" concept it going to be rapidly dismissed. NASA's X-43, (also a Boeing design) had hit speeds of up to Mach-9.6, (from the same booster burn out speed mind you) and over double the X-51 altitude, (that's important) and again a CONVENTIONAL fixed-inlet ramjet did Mach-5.5 at 40,000ft so of COURSE the 'requirement' for a Scramjet is going to be questioned. I have little doubt that IF, (big if mind you since the amount 'stated' towards the research and the actual planned spending is VASTLY different) the current (supposed) "possible operational hypersonic weapon system" goes anywhere it will be based on a "conventional" ramjet rather than a Scramjet. (Given that LM absorbed Martin Marietta after all the ones who designed and built the ASALM)
And not exactly enthused about Michael (we know him from the also 'undefined' production and acquisition process behind Constellation) Griffen being the one 'pushing' both the development of 'hypersonic weapons' AND 'streamlining' defense acquisition process.https://breakingdefense.com/2018/04/whack-7-dod-agencies-hasc-chairs-bill-proposes/
The D-21 was designed to fly at best around Mach-4, (Mach-3.35-ish listed but seen references to Mach-4 top speed) the X-15 on the other hand was always supposed to hit speeds in excess of Mach-5. Oddly enough the "X-20" was initially proposed to research speeds from Mach-6+ (where the X-15 program was supposed to top out) to Mach-20 but went from test vehicle to prototype vehicle as participants in the program dropped to just the Air Force who had to 'justify' it as a weapons system. Notably "RATTLRS" (http://www.designation-systems.net/dusrm/app4/rattlrs.html) was supposed to be only Mach-3 yet has a form more suited to much higher speeds.
For what purpose? Granted a turboramjet 'could' hit speeds in excess of Mach-5, (Mardquart tests in the early 60s showed a 'free-wheeling' compressor system could survive up to Mach-6 for short periods) the entire exercise is to test deep-cooling and the use of the SABRE flow-path and concept so having a 'turboramjet' onboard makes no sense. SABRE has a rocket whereas a turboramjet does not. We still talking a possible applications towards an "operational" vehicle? That would strictly depend on the airframe ability to accept different engines for different tests.
Getting more directly back on topic.My ROM for the vehicle and total propellant is 23500 Kg (excluding the engine but not the nacelle or pylon mass)What I don't think people realize is how big that makes it with LH2. Assuming SABRE 4 cycle REL reckon LH2 use is 2x usual O/F ratio. O/F for LO2/LH2 is somewhere between 5 and 6 to 1. So SABRE 4 shifts that to something like 5 or 6 to 2. So assuming 6 to 2 (or 3 to 1) and 12tonnes of propellant to keep the math simple that's 9t of LO2 to 3t of LH2. But that's 7.5m^3 (assuming LO2 subcooled to 1200Kg/m^3) but nearly 39 m^3 for the LH2 at 77Kg/m^3Assuming the fuselage is road transportable at 14 feet in dia that gives 14.3 m^2. That gives a LOX cylinder 0.53m long and a LH2 cylinder 2.73m long. That's 10.5ft long in total. Of course with tank ends and wrapping it in a Sears-Haacke body that will be considerably longer. Likewise I'd assume the LH2 tank will be split with the LO2 tank in the middle for CoG control. Note this is for a FTV that's a bit <50% structure, but Skylon is more like 25% structure, significantly increasing propellant load, but making the structural issues harder (Eyes on the prize. The #1 goal is engine and inlet testing. Structural verification would be a nice-to-have). The questions area) Can you wrap a fuselage and wings around this (and the nacelle and pylon) in less than 11.5t?b) What sort of flight duration could you manage?
Virtually strech a LH2 rocket stage with boosters and add wings.More basic question than flight duration: top speed.Going barely to M5 in airbreathing mode does not even need LOX, but has little customer value.
Testing of rocket mode may push the vehicle to M8~10 and change everythig, but could push the program more to TSTO systems, even to candidate of XS1.
BTW is it possible for SABRE to operate in VTVL mode without wings?
Quote from: Katana on 05/03/2018 01:01 pmBTW is it possible for SABRE to operate in VTVL mode without wings?In principle yes. Why would you want to?
Use rocket style airframe to simplify early tests.Core fuel tank + side "booster" mounted engine nacelles.Could be done soon when engines are ready, compared to typical time cost of M3+ aircrafts.
Quote from: Katana on 05/04/2018 09:58 amUse rocket style airframe to simplify early tests.Core fuel tank + side "booster" mounted engine nacelles.Could be done soon when engines are ready, compared to typical time cost of M3+ aircrafts.It's often said that rocket stages are not leggo and that you can't mix and match stages to create new vehicles. You seem to want to turn the X-7 drone into a VTO rocket.The theoretical cost savings of this are counterbalanced bya) Massively asymmetrical thrust, needing a fairly heavy thrust structure.b) No aerodynamic lift to reduce those propellant mass loads, which are now at 180deg to thrust, not 90deg.c) In HTOL Thrust (for supersonic aircraft) is 0.5-0.7xGTOW. For this it will need to be at least 1.15xGTOW IE 15-17.39tonnes, instead of the more like 28tonnes a HTOL vehicle would have available. d) The trajectory will be nothing like that all known SABRE using concepts need to have validated.e) If you're planning on a powered vertical landing you've lost even more of your GTOW to landing propellant. So IOW what you might save on costs you lose on a vehicle that contributes very little to the big picture in engine or vehicle design. There is an outside chance that cost might trump everything and a VTOL vehicle could carry enough propellant to take off, accelerate to the transition point and past it, then come back to land. But I strongly doubt it. Anything less would not be worth the effort, as engine operation to that point can already be demonstrated on the ground.I'd point out that a significant fraction of the cost of a new aircraft are the systems designed specifically for that aircraft. 28tonnes is in the range of a heavy fighter or a light regional airliners (like the Bombardier C series). While I'd like a FTV to retire the risk of some of the systems in Skylon they don't have to exist first before it can fly. Depending on structural fraction it does not have to use the Skylon construction method. With no effective payload landing gear could be an OTS package. Flight surfaces could be hydraulic, not electric etc. Improving the TRL of all of these is nice to have, but not essential to the design functioning. In fact the very first question, which I have taken as an article of faith, is can you build a HTOL vehicle around a 20 000 Kgf SABRE engine that will carry enough propellant to get it through the AB transition?I've been presuming so.
Two booster engines to be symmetrical like conventional rockets with strap on boosters, nothing related to X7.
The X7 airframe may work up to M6, but would be infeasible for rocket mode operation to M10.
Even without VTOL, the vehicle need to be symmetrical in rocket mode, which exclude X7 and favors BOMARC/ SR71/ original Skylon.
I wasn't sure if this should go in "Advance Concepts" or "Commercial" with the main SABRESkylon thread, but it's not meant to be a product and it' would certainly be advanced. REL have talked about the idea of a "Flight Test Vehicle" on a couple of occasions. Earlier ideas were for a scaled down Skylon, running LOX/Methane rockets while the current design, resembles the D-21 M3 reconnaissance drone designed to launch off the back of a couple of modified SR71s in hte late 60's. then modified with a booster longer than the drone, was tested off a modified B52, before the whole project was cancelled. However looking through the archives I located this. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000004765.pdfand this.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990110312.pdfBasically a late 90's plan to modify a couple of D-21 to demonstrate the "DRACO" Rock Based Combined Cycle engine some NASA centers were working on. This system has multiple mode transitions in its flight trajectory and also featured a moving inlet spike to accommodate the speed changes. In the process the second one discusses the D-21 in some detail, along with the LM Advanced Projects "Experimental Prototype" approach to cutting the development cost by about 1/3 (page 35 if you're interested).Interestingly they reckoned you could add a LOX tank between the fuel wing tanks and the engine duct, and they didn't think it would have thermal issues, although once you got above M3.5 the titanium skin and duct leading edge looked doubtful. Interestingly the issue around the LOX tank was not temperature related but pressurization. The D-21 was designed to operate its fuel tanks (there were 3, front, middle and back cross ways) at 1.5psi above the ambient pressure. Pressurizing the tanks to make the engine pressure fed was viewed as too dangerous. On the upside the REL FTV is a clean sheet design with a thrust about 29x bigger than the D-21 ramjet. (Marquardt RJ43-MA-20S4) and recovery and reuse will be designed in from day one. Beyond that we have a few data points.The SABRE test engine is expected to have a thrust of 20 tonnes (44 000lbf) and according to the SEI study on the USAF TSTO design thrust needs to be at least 70% of GTOW, giving about 28500Kg of mass. SABRE's T/W ratio is expected to be 14:1 so engine mass is say 1430Kg. The D21 dry mass 5500lb vs fully loaded at 11200lb means it was 49% structure. It was stressed to withstand -2/+5g in both axial and directions normal to axial. So a lower peak acceleration should give a lighter structure.28,500-1,430kg is a total mass of 27,070Kg. A 15% mass growth allowance means the maximum mass (structure and propellant) is 23,539Kg. To put this in perspective 30tonnes is a small(ish) regional airliner or a large(ish) fighter aircraft. My instinct is this layout is not a good fit to the issues around LH2 as a fuel, hence my interest in wheather it would be possible to make 2 engines and go with a "Mini Skylon" airframe. Given the D-21 is going to be REL's FTV design to test inlet design and spike schedule what does that say about its capabilities?My instinct is REL can go one of two ways on this. A "bare bones" X-plane approach.This is totally focused on flying SABRE through as much of its trajectory as possible and refining the inlet and spike performance to meet its goals. The vehicle structure is as simple as possible to do that. Not intended to be anywhere close to deliver a substantial payload to orbit, or a 2nd stage to release.A "Skylon risk retirement" approach.This implements the FTV in technologies more like those planned for Skylon. IE a truss framework with appropriate levels of MLI and the SiC reinforced ceramic skin fabricated in corrugated panels. Both options can help retire a number of operations features of a Skylon as well. EG fully automated fueling and de-fueling, although that would not be necessary for early tests. Likewise early tests could treat it as an RPV flown from a ground station, before moving to fully AGV status. the big question would be what else could it be used for ? What sort of things would 3rd parties like to test, and what sorts of instrumentation would they want to install to do so?
The form a test vehicle takes will depend on the requirements behind the funding.REL worked on FSPLUK which if funded may provide a flight tested vehicle that could fly a SABRE. But I can't see anyone funding a pure SABRE test vehicle until SABRE has been tested. BAe's initial estimates for a test vehicle was 1 billionThe Darpa funding has a potential phase 3, which covers flight testing (It also explicitly mentions dual use - civilian and military).
Quote from: Katana on 05/05/2018 06:06 amTwo booster engines to be symmetrical like conventional rockets with strap on boosters, nothing related to X7.Are you saying you think REL would build two flight engines or two rocket engines? Quote from: KatanaThe X7 airframe may work up to M6, but would be infeasible for rocket mode operation to M10.I'm talking about the X7 layout which is basically the same as the M2 Firebee II drone and Hound Dog missiles. Quote from: KatanaEven without VTOL, the vehicle need to be symmetrical in rocket mode, which exclude X7 and favors BOMARC/ SR71/ original Skylon.There have been a number of asymmetric thrust rocket concepts, IIRC one of the NLS designs for example. I think everyone would prefer a symmetric vehicle wheather it looked like Skylon or not. Thrust is more balanced, there are more engine placement options and you have redundancy, which is important given the new engine has unknown reliability statistics (something else flight testing will discover). It's wheather the budget will be available to allow it. The minimal assumption is there will be enough for one engine, not two, so what can you do with that one engine? Incidentally it turns out that through the 1970's and 80's NASA ran a number of studies for such an aircraft in the 40-60 000lb range as the "High Speed" or "Hypersonic Speed" Research Aircraft, partly to try out the various possible structural concepts they had seen on a scale that would give them a realistic test of the structural issues of a large aircraft. They reckoned you could build a baseline aircraft out of fairly conventional Aluminium with active water/glycol cooling good at least to M6. My instinct is for a passive heat pipes to move heat, eliminating the need for pumps and the large numbers of fluid connectors that have to stay fluid tight over a very wide range of temperatures and pressures covering the wings and fuselage. I don't think their complexity was ever really addressed and it's a non trivial problem to solve.
Why you think REL can't afford to build two engines , for a test vehicle? Building several more copies per batch only add minor cost to R&D. In fact they are really needed for backup, in case of damaging.Solving the asymmetrical thrust problem needs additional procedures, which becomes really expensive.
BAE works on military funding scales, if they say it will cost a billion, a non military contractor probably could so it for a fraction of that price. The vehicle only have to be something similar to SpaceshipOne,. Which cost around a 100 million dollars, even taking inflation into account it hard to get to BAE figure of a billion quid for a demonstrator vehicle.
The UK has just announce it building a new fighter the tempest. I think Reaction Engine can squeeze a bit of money out of this program. It could provide a continuous revenue stream by getting rolls royce to adopt it pre coolers for the fighter engine. Reaction Engine do claim they offer a lot of advantages, https://www.reactionengines.co.uk/sabre/pre-cooled-turbojet. This is Roll Royce video on the new engine Could the guy fit any more buzz words in this video! Improve thermal management is one of Reaction Engine claims through. Also nearly all the partners involve in Tempest are now also actively involved in Reaction Engine. I'm taking a little guess here but to be a truly next gen aircraft the Tempest will be base on a all electrical system. incorporate electrical landing gears and replace most of hydraulic systems with electrical systems, which should produce plenty of transferable knowledge to incorporate those technologies into skylon. Also could reaction engines take advantage of Project Magma https://www.baesystems.com/en/article/first-magma-flight-trials to further lighten skylon?Project Tempest if the UK truly wants a true 6th gen aircraft, should mature all of these technologies making them cheaper to integrate them into Skylon and produce a even lighter vehicle and may be even a simpler spacecraft to build as well.
The UK has just announce it building a new fighter the tempest. I think Reaction Engine can squeeze a bit of money out of this program. It could provide a continuous revenue stream by getting rolls royce to adopt it pre coolers for the fighter engine. Reaction Engine do claim they offer a lot of advantages, https://www.reactionengines.co.uk/sabre/pre-cooled-turbojet. Could the guy fit any more buzz words in this video! Improve thermal management is one of Reaction Engine claims through.
Also nearly all the partners involve in Tempest are now also actively involved in Reaction Engine. I'm taking a little guess here but to be a truly next gen aircraft the Tempest will be base on a all electrical system. incorporate electrical landing gears and replace most of hydraulic systems with electrical systems, which should produce plenty of transferable knowledge to incorporate those technologies into skylon.
Also could reaction engines take advantage of Project Magma https://www.baesystems.com/en/article/first-magma-flight-trials to further lighten skylon?Project Tempest if the UK truly wants a true 6th gen aircraft, should mature all of these technologies making them cheaper to integrate them into Skylon and produce a even lighter vehicle and may be even a simpler spacecraft to build as well.
Fluidic controls are even more problematical if you've already gone to electric actuators. Where you draw the line is a very tricky question. Necessary innovation (because you can't make the design work without it) versus unnecessary innovation, that adds cost, technical risk and potential delays.
I'm no expert but it just seemed like thrust vectoring a rocket nozzle with airflow would be a huge research project of its own and why would you want to do it for a launch vehicle?
As for replacing ailerons etc they mentioned that it got more challenging with larger aircraft but that the fact that large modern engines (as opposed to their model aircraft ones) had more compressors which might compensate. That's all I could get - I leave you to judge if anything's applicable to SABRE-powered vehicles.
Would fluidic nozzles win versus gimbals and associated structure to accommodate gimbaling? I get a sneaking suspicion that the mass and performance trades are real murky here.
For instance, is there enough bleed air from the SABRE compressor to run fluidics? On a more conventional rocket engine, would turbine exhaust work?
Shades of the TAN augmented nozzle work in a sense?
For Skylon, the nacelles have a serious bend to them, trying to matching between airflow flight angle and ideal thrust angle, which is probably not insignificant in terms of drag. Could one cheat with fluidics to effectively get more of the nozzle inline with the airflow and have variable thrust angle/trim?
Doing a web search I found this item from the British space agency. It's the planning for the flight test vehicle to test SABRE.Interesting points. It's funding comes from ESA through its general support programm for future technology. It's for both an FTV and a road map for a new full scale launch vehicle (single or two stage) for the European market in c2030.
I assume this would be funding that is not yet paid. If this is the case, would it be only available to EU members going forward, which might in some cases cause problems for BSA/Reaction.
EU membership is not a requirement for ESA membership, which is why Norway, Sweden, Finland and Switzerland (who are not part of the EU) can all be members. OTOH there are actual EU states that are only associate members, as is Canada, which is on a different continent.
Sweden and Finland are in the EU.
Norway, Switzerland and Canada are not in the EU and are sufficient to support your point.
Quote from: john smith 19 on 09/01/2019 08:38 amEU membership is not a requirement for ESA membership, which is why Norway, Sweden, Finland and Switzerland (who are not part of the EU) can all be members. OTOH there are actual EU states that are only associate members, as is Canada, which is on a different continent. Sweden and Finland are in the EU.Norway, Switzerland and Canada are not in the EU and are sufficient to support your point.
Quote from: Barley on 09/02/2019 03:09 pmQuote from: john smith 19 on 09/01/2019 08:38 amEU membership is not a requirement for ESA membership, which is why Norway, Sweden, Finland and Switzerland (who are not part of the EU) can all be members. OTOH there are actual EU states that are only associate members, as is Canada, which is on a different continent. Sweden and Finland are in the EU.Norway, Switzerland and Canada are not in the EU and are sufficient to support your point. The U.K. government has long said that Brexit will have no impact on the country’s membership of ESA.
To be frank: what the UK government says on Brexit does not necessarily have any particular correlation to reality.
The point is moot as indicated by Canada and Switzerland's memberships.
Looking through the document I can see to requirements for the FTV to be the 'same architecture' as the final vehicle.
the operational envelope of the FTV shall match, as closely as possible, that of the vehicle defined in work package 2.2
Potential SABRE applications and their market impact
Top level system requirements that would be dimensioning for SABRE/Vehicle concepts, and taking into account target market segments identified in WP 2.1
Indeed, the FTV is to fly without the SABRE at first, and then incorporate "one or more" SABRE engines at a later date. It looks like the FTV is intended to be analogous to the X-43, X-51 or HTV-2 vehicles and to then pull double-duty as a SABRE test vehicle if-and-when an engine is ready. That would avoid ESA spending money on a test vehicle they cannot use if RE run into any issues.
Establishment of vehicle development roadmap and associated Design Development and Verification Plan(DDVP) for the (FTV) detailing the system upgrade/replacement strategy, testing of various SABRE subsystems and integration of SABRE air-breathing core engine
The purpose of this study is two-fold, firstly to develop a roadmap for the next phase in the SABRE development, which is focused on flight-testing the core SABRE air-breathing engine, and secondly to assess the potential competitive positioning of future SABRE- powered applications in the future space transportation segment.
The Flight Test Vehicles(s) shall be experimental in nature and not target application beyond testing high-speed flight and SABRE systems to keep the cost low and to achieve a fast development schedule (the operational envelope of the FTV shall match, as closely as possible, that of the vehicle defined in work package 2.2).
. It is considered that the next technology step in the programme would be to develop a flight test vehicle that would initially test some components of the air-breathing SABRE core but would be reconfigurable (same airframe or multiple airframes) to eventually fly one or more complete SABRE air-breathing cores.
Operational envelope and architecture are two very different things (and both are a vast way from actual vehicle design). The FTV is intended not to test design of an eventual operational vehicle, only the engine operating regime (altitudes and speeds, and transitions between modes, onboard stores handling, etc). Building a "mini-Skylon" or similar seems to be directly at odds with the objectives of minimising costs (dual-engine would seem to be right out on these grounds alone) and acting as a pure testbed.
It also seems unlikely that the ground test engine (DEMO-A, which lacks the heat exchanger, uses a CoTS He compressor, and uses an 'off the shelf' combustion chamber and nozzle from Ariane Group) would ever be used for flight testing. The individual components are designed for discrete modular testing (the heat exchanger, the compressor, the combustion chamber, the Helium loop, etc) so may not even have an all-up full cycle test on the ground, let along somehow cram the entire assemblage into an airframe that can get off the ground. That would wait for a future engine iteration after ground testing is completed.
Quote from: Asteroza on 08/05/2018 11:48 pmFor Skylon, the nacelles have a serious bend to them, trying to matching between airflow flight angle and ideal thrust angle, which is probably not insignificant in terms of drag. Could one cheat with fluidics to effectively get more of the nozzle inline with the airflow and have variable thrust angle/trim?Maybe. Estimates are that this angle was about 14Deg for SABRE 3 but SABRE IV has halved that to about 7 Deg.
Doing a web search I found this item from the British space agency.
It's the planning for the flight test vehicle to test SABRE.It's funding comes from ESA
It's for both an FTV and a road map for a new full scale launch vehicle (single or two stage) for the European market in c2030.
Key goals are that the FTV should match the architecture of the proposed full scale
That strongly suggests a two engine FTV.
The request also requires the FTV should take off and land from a run way somewhere in Europe.
The key thing that cannot be demonstrated on the ground is the air breathing to rocket transition.
The request also talks of gradually building up what is being flown in terms of the core engine, the pre cooler and the bypass burners but I'm not sure that's possible.
The time frame of flight ready by 2025 strongly suggests taking the ground test engine will be the model for the engines in the FTV
(Demo-B?)
At the risk of being pedantic, I'm fairly sure it was the design changes between Skylon C2 and Skylon D1 that account for the reduction in nacelle curvature -- after all, the engine doesn't require any curvature at all
Are you sure it's from ESA, not from UKSA through ESA?
And a market model demonstrating the financial value of such a full scale vehicle
Are you sure? Annex A says in 1.3.1 "not target application beyond testing high-speed flight and SABRE systems to keep the cost low and to achieve a fast development schedule" -- so matching the architecture is ruled out. The only requirement is "the operational envelope of the FTV shall match, as closely as possible, that of the vehicle defined" i.e. verify SABRE trust/ISP matches the REL projections for speed/altitude
QuoteThat strongly suggests a two engine FTV."[the] FTV flies with a SABRE air- breathing core engine" -- doesn't even use engine(s)
it does seem to go out of its way to rule out Orbital Access' plan...Quote The key thing that cannot be demonstrated on the ground is the air breathing to rocket transition.What makes you think that?
That said, with non SABRE engine(s): * the intake could be tested on its own * the pre-cooler could be tested with the intake * and the bypass burners could be tested with the intake * the pre-cooler and bypass burners could be tested with the intake * the sabre core could be tested with the intake and pre-cooler; * the intake, pre-cooler SABRE core and bypass burners could be tested together.
Given Demo-A is the air-breathing engine demonstrator, and Demo-R is the proposed rocket demonstrator, it's more likely to be Test-A (Or Demo-A2)
The latest update from Reaction as the IAF Keynote gives much food for thought. In the past they have talked of a "Flight Test Vehicle" and "Nacelle Test Vehicle" but are now calling it the "Hyperson ic Test Bed" with either a single or a dual engine configuration. The single engine looks quite a lot like the X-7 "Flying Stovepipe" or the V1, but with a V tail. The dual engine vehicle looks rather more like the Skylon concepts Reaction have pursued for some time. GTOM is listed as 15-25t presumably between the single and dual engine. "Common sense" says the cheapest option is the single engine design. A little work with a spreadsheet gives the following. GTOM t Thrust as % of GTOM No of Engines Thrust / engine Kn Thrust / engine Lbs Possible Engines15 30.00% 1 44.15 9900 15 50.00% 1 73.58 16500 BR70015 70.00% 1 103.01 23100 V2500025 30.00% 2 36.79 8250 25 50.00% 2 61.31 13750 BR70025 70.00% 2 85.84 19250 BR70030% represents the thrust level of commercial airliners to GTOW, 50% the thrust of the Teledyne Ryan Firebee II supersonic drone to gross mass (air launched with a rocket booster) and 70% represents what USAFRL consultants set for their SABRE driven TSTO concept. The BR 700 is a commercial jet engine built by a joint venture of RR and BMW. it's available in several sizes. Splitting the thrust requirement into 2 engines substantially lowers the thrust range by about 4000lbs. Above a certain size you will only see high bypass ratio turbofans as the option, unless you can find some high thrust turbojets that are basically scrap. That said I'm not really sure how important a low BPR is to the design. Since it's likely the HTB will be built round the engine(s) Reaction select it should be readily available with either enough of them on the surplus market to get spares from or in active production. The challenge is that no suitable engine is going to run on methane or hydrogen so will have to be converted. Probably the other key major elements are the landing gear and tires. Again difficult to make in-house. a 25 tonne aircraft is a regional airliner like the Bombardier Q400 (28t) or the Bombardier CRJ200 (23t). 15t is more like the ATR 42-500Ideally the HTB would be big enough to carry the LH2 for the flight test with enough space left in the fuselage for the LOX for a subscale SABRE flight test. Although its core task is nacelle test I think the re-naming is interesting. It recognizes that a flight vehicle can test so much more.
Three points to consider. 1) If you examine figures 18 and 19 from the the keynote you can extrapolate the size of the nacelles which are about 7 metres long with a 1.5 metre diameter and further the engine depicted in figure 18 is approximately 4 metres long with a diameter of 0.80 metres, the dimensions of a low bypass military turbofan. The BR700 has a diameter of 1.8 metres I believe.2)Reaction engines has been engaged in a MOD project with Rolls Royce to put a heat exchanger in front of an EJ200 for the last two years. The EJ200 has a diameter of 74 cm and is 399 cm long with a dry thrust of 60kN and a wet thrust of 90kN.3) Reaction engines has been engaged in a study with STFC to use partially cracked Ammonia as a jet fuel replacement given that a lean Ammonia hydrogen blend behaves identically to jet fuel. A Hypersonic Test Bed vehicle with twin nacelles using ammonia fuelled EJ200's would tie together multiple strands of multiyear research for REL, it would provide the data they need themselves but also for their MOD contract as well as validating ammonia as a jet fuel replacement and improving the mass estimates they have for Skylon construction.Of course Ammonia is substantially less cryogenic that hydrogen so this would be a poor idea if the tankage can't be converted for a sub scale sabre test.
Quote from: JCRM on 10/14/2019 12:58 amAt the risk of being pedantic, I'm fairly sure it was the design changes between Skylon C2 and Skylon D1 that account for the reduction in nacelle curvature -- after all, the engine doesn't require any curvature at allFor a cruise vehicle probably not, but IIRC you want to go to orbit you want the front face of the nacelle square on to the airstream at the climb angle.
Quote from: JCRMAre you sure it's from ESA, not from UKSA through ESA?That programme is a general ESA programme for early stage development of new launch vehicle technology. AFAIK it's funded by all ESA members.
Quote from: JCRMThat said, with non SABRE engine(s): * the intake could be tested on its own * the pre-cooler could be tested with the intake * and the bypass burners could be tested with the intake * the pre-cooler and bypass burners could be tested with the intake * the sabre core could be tested with the intake and pre-cooler; * the intake, pre-cooler SABRE core and bypass burners could be tested together.Which suggests you're going to need at least 2 engine pods and a vehicle that can take off on the thrust of one, since the other won't be generating much (any?) useful thrust during takeoff.
Quote from: JCRMGiven Demo-A is the air-breathing engine demonstrator, and Demo-R is the proposed rocket demonstrator, it's more likely to be Test-A (Or Demo-A2)"Test-A" sounds more likely.
Where can i find that IAF paper please ?
The latest update from Reaction as the IAF Keynote gives much food for thought. In the past they have talked of a "Flight Test Vehicle" and "Nacelle Test Vehicle" but are now calling it the "Hyperson ic Test Bed" with either a single or a dual engine configuration. [...]Although its core task is nacelle test I think the re-naming is interesting. It recognizes that a flight vehicle can test so much more.
The challenge is that no suitable engine is going to run on methane or hydrogen so will have to be converted.
Ideally the HTB would be big enough to carry the LH2 for the flight test with enough space left in the fuselage for the LOX for a subscale SABRE flight test.
I'd guess PR changed the name to something more exciting, except this is Reaction Engines.
I think it is a better name, "Flight Test Vehicle" suggests it may be for testing flight characteristics, and with "Nacelle Test vehicle" those not familiar with the project may not understand Reaction Engines mean "Nacelle systems", which include intake, precooler, bypass and ramjets. "Hypersonic" - besides sounding hyperexciting - alludes to speeds above Mach 3, and "Test Bed" - as you note - emphasises it can be used to test multiple different things, even if it is only designed to test the nacelle systems.
Why does the engine need to be converted?
Ideally the HTB would be flexible enough to change tankage and plumbing and add equipment for measuring the conditions. That flexibility would hopefully allow for a small LOX tank for the couple of seconds needed to test transition.
All the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature. If you want to inject them as liquids instead everything gets a lot colder. New (additional) materials constraints limit your options. For example kerosene resistant rubber seals are likely to go brittle at near liquid methane temperature and probably shatter at LH2 temperatures. The O:F mass ratio for O2/HC is about 2.6:1 and 5.5-6.5:1 for H2, so injector design needs to change quite a bit if you go with hydrogen. REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial.
Quote from: john smith 19 on 12/16/2020 07:58 amAll the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature.[...]REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial. ... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.
All the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature.[...]REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial.
I'd guess REL would want it to run in rocket mode long enough for any plausible transient behavior to have died away. My instinct is maybe 10-20 secs
The paper on the X-15 telemetry system makes fascinating reading. About 90 readings were sent by telemetry to a ground station for engine health and GO/NO GO decisions wheather to launch, but the rest (about 1100) were recorded. [...]Although storage capacity has grown enormously since then I suspect there will still be too many parameters at too high a sampling frequency chasing too little storage (although I expect micro SD cards in the TB size to be quite cost effective when this starts flying) so some kind of selection process (and tracking of channel assignments) will still be needed.
My instinct is air data will be difficult. The SoA is a "Flush Air Data System" of multiple pipes in the nose. But that will depend on how much experience BAE (or whoever builds the HTB) has with the technology.
High speed intake aerodynamics and flow distortionApplications are invited for fully-funded PhD studentship in the area of aero-engine intake aerodynamics within the Propulsion Engineering Centre at Cranfield University. The research will focus on propulsion system – supersonic intake integration and dynamic distortions for novel aircraft configurations
A new study by the UK Space Agency and ESA suggests that we should develop a Hypersonic Test Bed (HTB) so as to have a revolutionary impact on reusable spacecraft for horizontal launches.
Quote from: john smith 19 on 12/16/2020 07:58 amAll the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature. If you want to inject them as liquids instead everything gets a lot colder. New (additional) materials constraints limit your options. For example kerosene resistant rubber seals are likely to go brittle at near liquid methane temperature and probably shatter at LH2 temperatures. The O:F mass ratio for O2/HC is about 2.6:1 and 5.5-6.5:1 for H2, so injector design needs to change quite a bit if you go with hydrogen. REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial. ... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.
Quote from: edzieba on 12/16/2020 08:45 amQuote from: john smith 19 on 12/16/2020 07:58 amAll the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature. If you want to inject them as liquids instead everything gets a lot colder. New (additional) materials constraints limit your options. For example kerosene resistant rubber seals are likely to go brittle at near liquid methane temperature and probably shatter at LH2 temperatures. The O:F mass ratio for O2/HC is about 2.6:1 and 5.5-6.5:1 for H2, so injector design needs to change quite a bit if you go with hydrogen. REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial. ... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.If nothing else, it would be reconfirming the MIPCC precooling work they were doing for the high speed F-4X Phantom project back in the day, which was probably the last time practical work was done.
... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.
Quote from: john smith 19 on 12/16/2020 07:58 amI'd guess REL would want it to run in rocket mode long enough for any plausible transient behavior to have died away. My instinct is maybe 10-20 secsFor STERN, "Each firing was restricted to less than a second [... which] provided sufficient time for the flow to stabilise, and all the required data to be obtained" but these are bigger and more complicated than STERN.The STS was launched six seconds after the SSMEs were started, which was long enough for transients to have gone and the required data to be collected.It's likely to be somewhere between the two. Of course, after the engine has started and is stable, the air-breathing core needs to shut down, which affects the exit plane. At some point in the rocket flight the nozzle extension will be ...err... extended - but it's not entirely clear when that would be, and so it's difficult to predict if that's in the flight envelope of HTB.
data acquisition systems have improved enormously since then, 30 Hz x 1024 channels fits in 4x20x45 cm, and 128kHz x 32 channels are smaller. Pair those with 1 GB SSD and you can gather hours of flight data. Buy as many of each as you need for your requirements.
Quote from: JCRM on 12/16/2020 09:16 amQuote from: john smith 19 on 12/16/2020 07:58 amI'd guess REL would want it to run in rocket mode long enough for any plausible transient behavior to have died away. My instinct is maybe 10-20 secsFor STERN, "Each firing was restricted to less than a second [... which] provided sufficient time for the flow to stabilise, and all the required data to be obtained" but these are bigger and more complicated than STERN.The STS was launched six seconds after the SSMEs were started, which was long enough for transients to have gone and the required data to be collected.It's likely to be somewhere between the two. Of course, after the engine has started and is stable, the air-breathing core needs to shut down, which affects the exit plane. At some point in the rocket flight the nozzle extension will be ...err... extended - but it's not entirely clear when that would be, and so it's difficult to predict if that's in the flight envelope of HTB.That makes no sense. If you're going to test the AB/rocket transition then the nozzle extension is a critical part of that process. You don't have a complete test without it. There are multiple possible options for how to do it. Some of them may be eliminated through ground test and simulation but a flight test of at least one of them is crucial.
or the rocket is already in idle. Those question will set the operating parameters for whatever actuators are chosen to produce that motion, and the environment they will have to operate in.
Quote from: JCRMdata acquisition systems have improved enormously since then, 30 Hz x 1024 channels fits in 4x20x45 cm, and 128kHz x 32 channels are smaller. Pair those with 1 GB SSD and you can gather hours of flight data. Buy as many of each as you need for your requirements.(1024)^3 / (128 000 *32) --> 262.144 secs of recording time, assuming the data and storage are byte wide. The first example gives something like 19hrs at byte wide data
As always the jokers in the pack are flight duration, resolution and sample rate.
Quote from: JCRMThe HTB study was being performed by Cranfield Aerospace, an offshoot of Cranfield University - who operate their own airport, are a registered airline and operate their own "airborne laboratory"An example of their research:QuoteHigh speed intake aerodynamics and flow distortionApplications are invited for fully-funded PhD studentship in the area of aero-engine intake aerodynamics within the Propulsion Engineering Centre at Cranfield University. The research will focus on propulsion system – supersonic intake integration and dynamic distortions for novel aircraft configurationsThese guys probably know a thing or two about monitoring.True, but they are usually done in a lab on the ground with instruments that are not flight weight. Very little work seems to have been done in this area for vehicle mounted sensing.
The HTB study was being performed by Cranfield Aerospace, an offshoot of Cranfield University - who operate their own airport, are a registered airline and operate their own "airborne laboratory"An example of their research:QuoteHigh speed intake aerodynamics and flow distortionApplications are invited for fully-funded PhD studentship in the area of aero-engine intake aerodynamics within the Propulsion Engineering Centre at Cranfield University. The research will focus on propulsion system – supersonic intake integration and dynamic distortions for novel aircraft configurationsThese guys probably know a thing or two about monitoring.
No, that's testing deploying the nozzle extension. The air-breathing shutdown has to be complete before moving the nozzle, so it can't happen during air-breathing to lox transitionThe sequence is most likely to be hydrolox start -> air breathing shutdown -> nozzle extension,but could be air-breathing shutdown -> nozzle extension -> hydrolox start
It'll be ballscrews as previously discussed elsewhere.
I'd suggest 4 bytes for values, two at a pinch, and 8 bytes per row for TAI64 timestamps.
Disk capacity is measured in GB or MB etc, not GiB or MiB (i.e in 10^3s) so your capacity is a little off. In general data can be striped across multiple disks (better for write bandwidth), but failing that SSDs up to 100TB are available. (but I've not had a play with them yet)
The HTB study was being performed by Cranfield Aerospace, an offshoot of Cranfield University - who operate their own airport, are a registered airline and operate their own "airborne laboratory"An example of their research:OK, it's only Mach 2, but.... they instrumented a Typhoon for temperatureThey have people who do this for a living, and if scramjet research has done nothing else it has developed hypersonic instrumentation which will be in the literature/conferences, so they would probably know more about it than armchair enthusiasts like me.
Quote from: edzieba on 12/16/2020 08:45 am... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.It's certainly an option, but it complicates the logistics and HTB construction, as would running on ammonia. Depending on the volume of the tanks involved you could be looking at a major rebuild to accommodate the switch over.
Quote from: Asteroza on 12/17/2020 02:06 amQuote from: edzieba on 12/16/2020 08:45 amQuote from: john smith 19 on 12/16/2020 07:58 amAll the aircraft gas turbine I know of burn room temperature liquid hydrocarbons. Methane and hydrogen are gases at room temperature. If you want to inject them as liquids instead everything gets a lot colder. New (additional) materials constraints limit your options. For example kerosene resistant rubber seals are likely to go brittle at near liquid methane temperature and probably shatter at LH2 temperatures. The O:F mass ratio for O2/HC is about 2.6:1 and 5.5-6.5:1 for H2, so injector design needs to change quite a bit if you go with hydrogen. REL did this work when they converted the viper to run on butane for their precooler tests. NASA did GH2 conversions for some airliner size engines in the 1970's. The process is known but not trivial. ... I think the point was to run an unconverted jet engine on good ol' avgas, have an on-board ancillary cryogen tank to cool the He loop, and just test for a shorter duration. You can mess around converting a jet engine to cryogens or installing a SABRE prototype later, but sticking a precooler in front of a stock jet engine and flying with the precooler active for maybe 100 seconds (initial ascent and post-test descent running on the stock jet engine without inlet cooling) retires a lot of risk with minimal investment.If nothing else, it would be reconfirming the MIPCC precooling work they were doing for the high speed F-4X Phantom project back in the day, which was probably the last time practical work was done.Do you mean "Peace Jack"? the plan to build a M3 reconnaissance aircraft using water spray injection of the inlets?I didn't think it ever got to a flight test. Ground tests at REL got to the equivalent of M3 at the start of high temperature HX testing last year.
These two are related. Peace Jack was the 1974 Israeli RF-4X proposal that scared the shit out of SR-71 supporters. Thirty years later in the mid-2000s the MIPCC Phantom was brought back as an early step toward RASCAL (which obviously also used MIPCC) It would be fantastic indeed, to see REL bringing back MIPCC via their precooler technology. MIPCC tech never got a chance.
It "complicates" the construction, by requiring design for flexibility. The Skylon design has the tanks just hanging in the aeroshell. Hanging different tanks based on the requirements of the experiment isn't a major rebuild.
It allows the HTB to be tested with no novel engine technology.
Quote from: JCRM on 12/18/2020 06:01 pmIt "complicates" the construction, by requiring design for flexibility. The Skylon design has the tanks just hanging in the aeroshell. Hanging different tanks based on the requirements of the experiment isn't a major rebuild.If HTB follows the layout of Skylon then you're looking at removing both ends of the fuselage to replace the tanks. Again this is conceptually simple but IRL going to be very tough. Again if they go with the fibre reinforced glass material REL have been looking at you're looking at removing quite a lot of rivets and replacing them later without damaging the structure.
Or go in through a central access door a bit like Skylon gets its payload in and out
The Skylon skin design is to use ceramic shingles to allow for thermal expansion, it should be possible to detach the front end without removing any shingles or rivets. The back end would be trickier, if one forgot to design for it.
HVX concept V seems to not have a full cone nose inlet, something tucked up under the chin? Plus I may be looking at it wrong, but the wing root seems kinda thin to be a wet wing, suggesting all fuel in the fuselage?Edit: New pic shows chin inletEdit: Maybe the wing roots could accommodate tankage after all?
The Flight test Vehicle / hypersonic test bed may now be know as HVXhttps://reactionengines.co.uk/delivering-the-future-of-uk-hypersonic-capabilities/
HVX’s immediate objective is to rapidly mature technologies which can deliver a step-change reduction in the cost of developing a reusable high-Mach/hypersonic air vehicle.
HVX’s immediate objective is to rapidly mature technologies which can deliver a step-change reduction in the cost of developing a reusable high-Mach/hypersonic air vehicle. Reaction Engines’ novel precooler and SABRE combined-cycle engine technologies are key foundations for the Programme. In combination with Rolls-Royce’s world-beating gas turbine technology, this brings a formidable capability to take on the challenging problems inherent with hypersonic flight.Additionally, the Programme is undertaking design work on experimental hypersonic vehicle concepts. At the Farnborough International Air Show a single engine hypersonic concept vehicle – “Concept V” has been unveiled. This example vehicle is one of a number of concept designs in active development by the Programme.
So HVX may be a precursor to HTB
I don't think that's enough of a concern to require a whole new job role, compact CotS aerospace DAQ setups are readily available, no need to reinvent the wheel there.
Industrial sensors are not always big chunky things (e.g. remote fibre sensing; which includes strain sensing, chemical detection, pressure sensing, etc).
The STS MMUs for first flight were magnetic tape based. That capacity and bandwidth limitation is not present today.
You don't seem to think this needs any tracking or management so I think we'll have to agree to differ on this point.
As to what a Hypersonic Test Bed could be used for Stratolaunch released a paper on their work. The full size vehicle is called "Hyper-Z" and is pitched to go M10, but the vehicle they've built so far is what's called in the paper "Hyper-A" but is now named "Talon" and is targetting M6. They are claiming that it can reach M2-3 from the runway on internal rocket power alone (without the ROC to carry it). But that leads to questions about landing gear mass, unless they plan some kind of trolley takeoff, or a big hit on payload IE experiments. Table 2 of this paper suggests some of the sort of people who would be interested in testing stuff on their vehicle. Curtis Wright also have a white paper on desiging DAQ for a HTB, and it also looks like Talon. CW bought a UK company that specializes in this sort of work, which would complicate ITAR issues, unless REL can find someone else to deal with this side of things. IOW people do think there is a market for a high speed reusable test vehicle to allow research teams to explore various different areas of M5+ flight, and to refine their ideas and retest them again.
That paper is out of date. Their Hydrolox engine development was cancelled when Allen's family took over business. Still developing a Hypersonic vehicle which is powered by Usra Hadley engine.
No more so than they will already be doing for their many existing test stands.
Quote from: edzieba on 08/19/2022 10:50 amNo more so than they will already be doing for their many existing test stands.What test stands?There's TF2.
Quote from: JCRM on 09/06/2022 11:49 amQuote from: edzieba on 08/19/2022 10:50 amNo more so than they will already be doing for their many existing test stands.What test stands?There's TF2.HTX test stand in Denver (TF2), HX3 test stand at Kemble, preburner test stand and IPS test stands at Cotswald airport, the rocket nozzle test stand(s) at Wescott, and the old 'back yard' precooler test rig also at Wescott.
HTX: RE Inc, Colorado.Precooler test stand, Reaction Engines Ltd, Culham, *Cold E/D: Bristol University, BristolSTERN, STRICT, STOIC, pre-burner injector, HX3: Airborne engineering, at WestcottPre-burner, Integrated Pre-burner/HX3: S&C Thermofluids, Cotswald airport in Kemble*I missed this one because I was thinking solely of hot tests. Mea Culpa. In my defence Reaction didn't consider it a test facilityMy point stands, Reaction operates a single test stand, and are likely to rely in part on the equipment and engineer expertise at the other facilities -- explicitly so at AEL.John Smith 19 is right in saying Reaction, as it grows and its teams specialise, should have someone coordinating the data collection to ensure data relevant to the whole platform is gathered during tests, not just that desired by the designers of the particular subsystem. I would hope and expect there is already someone doing this, but it's the kind of thing that can get missed.
HTB is a key element on the path to be being able to offer a complete SABRE package, but it has the possibility of generating an ongoing revenue stream, not as a product but as a service if the needs of outside users are considered in its design and construction.
now defunct Orbex
Quote from: john smith 19 on 09/07/2022 07:42 amHTB is a key element on the path to be being able to offer a complete SABRE package, but it has the possibility of generating an ongoing revenue stream, not as a product but as a service if the needs of outside users are considered in its design and construction.... and as a product, if something like the now defunct Orbex is started.
Quote from: JCRM on 09/07/2022 09:54 amQuote from: john smith 19 on 09/07/2022 07:42 amHTB is a key element on the path to be being able to offer a complete SABRE package, but it has the possibility of generating an ongoing revenue stream, not as a product but as a service if the needs of outside users are considered in its design and construction.... and as a product, if something like the now defunct Orbex is started.Or not. Interestingly both Orbex and Skyrora are saying they are using "bio" derived fuels. I knew one was running "Biopropane" but I didn't realise the other was using a keroscene derived from waste plastics. However this is OT for the thread itself but it's good to see people tackling the environmental issues up front (LH2 of course burns to water, which has a life in the atmosphere of 8-9 days).
Quote from: JCRM on 09/07/2022 09:54 amnow defunct OrbexStill alive as of 2 weeks ago.
A Brain Fart. I meant Orbital Access
I think a key person within REL will need to be a "Flight Data Coordinator" to ensure that all groups have enough storage, and bandwidth to that storage to ensure any given flight is successful.
Not really needed. This job is part of the flight test team. Data recording and storage are not a limiting factors. It is sensors and data lines (mass).
Quote from: Jim on 09/08/2022 01:16 pmNot really needed. This job is part of the flight test team. Data recording and storage are not a limiting factors. It is sensors and data lines (mass).An interesting PoV. So are you saying the mass of individual sensors need to be reduced?
It isn't a POV. It is just really. Sensors and data lines have mass. Storage media is no longer a constraint to the amount of data collected.Managing the data is not a big deal either. It can be placed on server for everybody to access
I came across this paper which discusses the aerodynamics of one of the possible HTB vehicle configurations. It's conducted as part of the H2020 More&Less project.https://www.icas.org/ICAS_ARCHIVE/ICAS2022/data/preview/ICAS2022_0596.htm
I do wonder whether the existence of the HVX programme shifts the aims of the HTB. Does the HVX just make the HTB cheaper to realise or does it give latitude for greater ambition?
Quote from: lkm on 01/21/2023 11:10 pmI do wonder whether the existence of the HVX programme shifts the aims of the HTB. Does the HVX just make the HTB cheaper to realise or does it give latitude for greater ambition?If your implementation costs are high you have the classic aerospace paradign. Commit to no physical hardware untill absolutely every last possible simulation has been done and every possible failure mode has been considered. OTOH if costs are more reasonable you can afford backups, optional versions of parts with more aggressive loadings or lighter versions. You can experiment and take risks. More to the point you can be tolerant of failure without which there is no true progress. Note the name change (from "Nacelle Test Vehicle") is already an indication of greater ambition. From the SABRE specific needs of tuning the inlet, nacelle and excess H2 burner designs to being able to offere a general purpose vehicle capable of reusably testing a wide variety of components, systems and processes connected to hypersonic flight. From (for example) robust temperature/pressure/flow sensors compared to existing types right up to the whole organisation of post-flight data reduction to compare new with existing approaches. So yes I think it will open things up. Did you have any particular directions you're interested in them going?
Although the primary purpose of the HTB is fornacelle technology development, an extension to theHTB programme may provide potential opportunities tosupport some aspects of both the air-breathing core androcket engine development programmes. For example,having developed a flight test platform that is capable ofhigh Mach/Altitude flight, it may be possible to use thiscapability for in-flight testing of nozzle aerodynamicsand air breathing/rocket transition and as previouslydiscussed the platform could also be used for in-flightdemonstration of SABRE by substituting theexperimental nacelle COTS gas turbine with a flightintegrated version of the DEMO-A+ core. Furthermore,the HTB may potentially also be used to develop manyof the future launch vehicle airframe technologies (e.g.materials, structures, re-entry) in advance of a full-scaleprototype SABRE launch vehicle.
I think the next key question RE faces after whether SABRE will work is whether their Skylon mass estimations are correct. You can see this from the CNES TSTO study, SABRE performance is accepted but the study vehicle is just an enlarged Skylon with much increased mass margins because their mass assumptions are not. It's accepted that SABRE can be built today but not that a SSTO Skylon can be built too.
I think the twin nacelle concept built using the core Sklyon construction technologies would do a lot to answer those questions before any launch concept is chosen as it's the closest to a scale Skylon. In 2020 this was only a potential stretch goal but perhaps with improved funding things have changed.
I think the twin nacelle concept built using the core Sklyon construction technologies would do a lot to answer those questions before any launch concept is chosen as it's the closest to a scale Skylon.