Author Topic: Reaction engines Flight Test Vehicle speculation  (Read 32715 times)

Online edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #80 on: 12/16/2020 08:45 am »
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.
... 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.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #81 on: 12/16/2020 09:16 am »
*deleted*

edzieba put it better than I did:
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 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.
I'll add the reason the Viper was converted was because the precoolers in that test were taking the air temperature down to waaaaay below freezing for jet fuel.

SABRE 4 doesn't require such low temperatures

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
For 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.

Quote
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.
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: John Smith 19
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.
It probably would be.

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:
Quote
High speed intake aerodynamics and flow distortion
Applications 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
These guys probably know a thing or two about monitoring.
« Last Edit: 12/16/2020 09:32 am by JCRM »

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #82 on: 12/17/2020 01:41 am »
Apparently the 3 month study announced in May concluded we should build a HTB, but I'm unable to find any details...
Quote from: Orbital Today
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.

Offline Asteroza

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #83 on: 12/17/2020 02:06 am »
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.
... 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #84 on: 12/17/2020 06:25 am »
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.
... 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.
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Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #85 on: 12/17/2020 06:42 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. You trade trade a conceptually simple (but potentially very awkward) task for something that is more complex but can be done off line and in parallel with vehicle construction.
REL also developed an aero engine H2 combustor design as part of the LAPCAT programme. That might prove to be the simplest way to do the conversion.
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Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #86 on: 12/17/2020 07:19 am »
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
For 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.
Obvious factors are how far the nozzle has to move, how fast, and wheather AB mode is still active (and the inlet partly open) or the vehicle is in a short coast, 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: JCRM
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.
(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. A subsidiary point is that while the storage and digitization systems have shrunk enormously the actual sensors still have significant mass. The X-15 was a national programme and had 1500lb (681Kg) allocated to this hardware (which IIRC was lots higher than NAA originally pitched but was what the client said they needed). It depends on what constraints they have to design to. They've stated DEMO-A is in in the 20 000Kg thrust class.
I listed some engines that match this but the EJ200 that powers the Typhoon is about 4 132 Kg thrust with full reheat. If this is available through collaboration with BAE and RR that scopes the size of a potential HTB.


Quote from: John Smith 19
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.
It probably would be.

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:
Quote
High speed intake aerodynamics and flow distortion
Applications 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
These guys probably know a thing or two about monitoring.
[/quote]
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. FADS is basically the Pitot tube reworked to minimize reentry heating.
The ideal solution would not need holes cut in the TPS (or in case of the shuttle would have to have a set of pipes molded into the RCC nose cap if it had actually been deployed  :( ) but would still be capable of reading external air data.
« Last Edit: 12/17/2020 07:32 am by john smith 19 »
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Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #87 on: 12/17/2020 05:36 pm »
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
For 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.
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 transition

The sequence is most likely to be hydrolox start -> air breathing shutdown -> nozzle extension,
but could be air-breathing shutdown -> nozzle extension -> hydrolox start

Quote from: john smith 19
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.
It'll be ballscrews as previously discussed elsewhere.
Quote from: john smith 19
Quote from: JCRM
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.
(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
OK, you got me, I only calculated for the slow recorder, eyeballing the other as roughly the same ballpark.
The smallest SSDs around tend to be 128GB, so there should be plenty of space for recording the portions of the flight of interest.

Quote from: john smith 19
As always the jokers in the pack are flight duration, resolution and sample rate.
Welcome to the 21st century, where a TB of storage weighs around a gram.

I'd suggest 4 bytes for values, two at a pinch, and 8 bytes per row for TAI64 timestamps. That should gives you over a minute of storage on 128GB for the fast recorder.

In general data can be striped across multiple disks (better for write bandwidth), but failing that SSDs up to 100TB are available, but NVMe (which I'd recommend for weight and performance) is topping out at around 16TB, but that should still give two hours of storage at the high data rate.

Quote from: John Smith 19
Quote from: JCRM
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:
Quote
High speed intake aerodynamics and flow distortion
Applications 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
These 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.
OK, it's only Mach 2, but.... they instrumented a Typhoon for temperature

They 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. I probably know more about strorage than they do though.
« Last Edit: 12/18/2020 08:01 am by JCRM »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #88 on: 12/18/2020 07:55 am »
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 transition

The sequence is most likely to be hydrolox start -> air breathing shutdown -> nozzle extension,
but could be air-breathing shutdown -> nozzle extension -> hydrolox start
A fair point, but it is needed to demonstrate the complete switch over from air breathing to total rocket power.  Without it doubters will continue to claim that it is possible there are still unknown unknowns lurking (because you didn't fully complete the process  :(  )

Quote from: JCRM

It'll be ballscrews as previously discussed elsewhere.
They'd have to be the odds on bet.
Quote from: JCRM
I'd suggest 4 bytes for values, two at a pinch, and 8 bytes per row for TAI64 timestamps.
4 bytes is excessive for temperature, even in kelvin. It would be necessary for pressure in Pa, but 2 is probably enough in bar or millibar. Wheather nanosecond resolution is needed is debatable but an agreed standard does allow OTS libraries
Quote from: JCRM
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)
True, but AFAIK memory card capacities are use 1024 for  a kilo. I like to keep things simple.

]
Quote from: JCRM
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 temperature

They 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.
I should have been more specific. I meant the Air Data Systems that can report the vehicle attitude relative to oncoming airflow. The successors to the X-15's "Q-Ball" system.
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Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #89 on: 12/18/2020 06:01 pm »
... 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.
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.
It allows the HTB to be used to test an ammonia engine
It allows the HTB to be used to test SABRE's nacelle systems with an unmodified jet engine
It allows the HTB to be used to test SABRE's nacelle systems with a SABRE core and conventional nozzle
It allows the HTB to be used to test SABRE's nacelle systems with a SABRE core and advanced nozzle.
It allows the HTB to be used to test a full SABRE engine

Offline libra

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #90 on: 12/19/2020 06:04 am »
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.
... 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #91 on: 12/19/2020 06:27 am »
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.
Generically SABRE is pre-compressor cooling with an inert fluid. So it's like Peace Jack. OTOH it's a cryogen which I think is what MIPCC was going to go with using liquid air. 

So similar lines of thinking but (like a lot of REL's stuff) with a twist.  :)

I think it will be fantastic. I do hope REL manage to do a video of the HTB's first flight with SABRE(s) fitted. It will be very impressive (and TBH very noisy).
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Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #92 on: 12/19/2020 07:25 am »
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.
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.  :(
Quote from: JCRM
It allows the HTB to be tested with no novel engine technology.
IMHO this is the key question  :( In principle it allows flight testing to start sooner. Just get the major components together and build the nacelle(s) around them.

It all comes down to confidence.  Is REL more confident of their ability to convert jet engines to GH2 and possibly ammonia, or the structural issues of taking both ends off a fuselage and putting them back on intact?

There might be an alternative. It all depends on the volumes of the fuels involved and wheather you want to take off on kerosene for the ammonia tests and switch in flight. If the fuselage volume exists (or you're OK with using the wings for kero and/or ammonia) you could install all tanks during the build.

Wing tanks could be fitted as separate structures inside the wings but that would complicate the wing structure and are not a key design goal.  :( Neither the SR71 nor Concorde were fluid tight. They would naturally be empty when running on LH2. Thermal expansion behavior of the Skylon skin material will be very different to titanium, steel honeycomb or nickel based super alloys.  :(

The tank volumes needed will be in turn set by how long is each flight phase and what projects HTB will support.  REL have repeatedly stated they want to fly, as far as possible, the complete trajectory of a Skylon with whatever test vehicle design they have planned to use.

I'm certain someone inside REL has been tracking jet engines in the relevant sizes. What there fuel burn is, and some idea of how it would change if (what it burned) was changed to something else.
« Last Edit: 12/19/2020 06:22 pm by john smith 19 »
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Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #93 on: 12/20/2020 02:37 am »
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.
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.
« Last Edit: 12/20/2020 02:42 am by JCRM »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #94 on: 12/20/2020 06:52 am »
Or go in through a central access door a bit like Skylon gets its payload in and out
That "a bit like Skylon" may be misleading you.

Skylon's bay is about 3/4 of its diameter. It's tanks are not far off it's full diameter. So either the tank diameter has to be substantially narrower than the fuselage or the door is much closer to full width.   Skylon's payload bay is roughly 1/4 it's full length but yours would need to be the length of the longest tank.  If it isn't then how to winch the tank out and where to attach the cables to haul it become very tricky.

Which suggests the "door" will be a) 1/2 (or more) of the vehicles length, which suggests it will be  b) Load bearing.

Of course REL could ditch a cylindrical fuselage and go for something more  boxy, like the shuttle. And of course there should be no reason for it to open in flight which eliminates all the actuators and hinges. It can be lifted straight off, like a lid and locked in place. Potentially quite a significant simplification.  Of course not having one at all would be the greatest simplification.

[EDIT It's a question of  margin. DEMO-A has a stated thrust of 44 000lb or 20 tonnes. an EJ200, which is being used for MoD funded work is about 13 000lb dry, 20 000 on reheat. Assuming take off thrust is 70%of GTOM (because that's what the SAIC studies like to use) gives you GTOM of 18571 lb (single engine, no reheat)  and 57142 lbs (dual engine, full reheat). That is without any growth margin.  And you might like to avoid relying on reheat to make takeoff as it's not clear  how well ammonia works in this (it's flammable mixture range is much narrower than that of kerosene or hydrogen). 

You'd want to avoid having to remove the LH2 tanks if at all possible. Which means carrying them for all flight tests, preferably sub cooled to avoid any boiloff venting (that's not a trivial issue). But do you have enough thrust for long enough to carry their dead weight and enough fuel to run the other tests? Is the space taken by the LOX tanks enough to allow replacement by kero or ammonia? Could the LOX tanks with additional plumbing carry kero and ammonia? The cleaning regime after use would have to be very thorough to avoid explosions (not unknown around LOX  :( ) ]
Quote from: JCRM
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.
AFAIK the Skylon skin is designed to be made in longitudinally corrugated sections, somewhat like parts of the SR71. IIRC they are meant to be about 0.3m square (bigger would be better but I think this size lets them wrap most of the fairly complex shape with a single panel design, although the rest will need different designs).  They are ceramic. I wouldn't call them a shingle. However as the HTB does not need to go above about M6, and then only for a less than a minute various other options are possible. With the X-15 heat soak was the goal (like the Bristol 188, which didn't have enough fuel to fully explore this). Not so with the HTB or Skylon.
« Last Edit: 12/20/2020 09:49 am by john smith 19 »
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Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #95 on: 07/18/2022 03:30 pm »
The Flight test Vehicle / hypersonic test bed may now be know as HVX

https://reactionengines.co.uk/delivering-the-future-of-uk-hypersonic-capabilities/

Offline Asteroza

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #96 on: 07/18/2022 11:11 pm »
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 inlet
Edit: Maybe the wing roots could accommodate tankage after all?
« Last Edit: 07/22/2022 04:00 am by Asteroza »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #97 on: 08/05/2022 10:23 am »
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 inlet
Edit: Maybe the wing roots could accommodate tankage after all?
Note that the name implies at least 5 variants were tested. 

It does not state a) if that was all of the variants that were tested or b) that it is the one that will built.

I have been offline for some time due to hardware and software issues.  I have been following but unable to reply. I now am.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022. Forward looking statements. T&C apply. "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #98 on: 08/05/2022 10:37 am »
The Flight test Vehicle / hypersonic test bed may now be know as HVX

https://reactionengines.co.uk/delivering-the-future-of-uk-hypersonic-capabilities/
Possible. Note who's not on the supplier list. The airframer HMG insisted that REL take on as a partner, BAe.

Now note it's #1 goal.
Quote
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.
TBH REL could have taken an airframer as any partner of the Typhoon programme, as all have M2+ experience.

REL have commented that when they asked BAe for a demonstrator price they were told £1Bn, which I guess is like Rocketdynes price for a new engine $1Bn.

Looks like honeymoon period for BAe is over. I suspect they may have also had something do with the TF1 situation and its somewhat curious business arrangements.

This book of conference abstracts has some intersting stuff on the HTB. It was discussed in a "Special  Technolgy Session" at this conference, which was actually held in 2021.  HTB is in Session 16, along with a number of other European concepts.

I've not been able to locate the full paper on line but the abstract is intriguing.

When I looked up "Hyerpsonic Test Bed" I located a paper from Curtis Wright Defense Solutions, but I suspect it refers to the "Talon" vehicle that Stratolaunch are planning to fly.
« Last Edit: 08/06/2022 06:33 am by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022. Forward looking statements. T&C apply. "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #99 on: 08/05/2022 10:50 pm »
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 inlet
Edit: Maybe the wing roots could accommodate tankage after all?
IIRC the chin inlet is quite good for air flow for missiles, as it has good flow characteristics not just "square on" to the airflow but also at an angle. Handy if you're on a rising trajectory trying to hit an aircraft.

My instinct is not to get too hung up on this concept.  Even the idea that "Concept V" was the last one considered is doubtful. Think of it as a placeholder for the project.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022. Forward looking statements. T&C apply. "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap

 

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