Author Topic: Reaction engines Flight Test Vehicle speculation  (Read 54474 times)

Offline john smith 19

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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.pdf
and this.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990110312.pdf

Basically 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?

« Last Edit: 04/14/2018 05:58 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Star One

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Reaction engines Flight Test Vehicle speculation
« Reply #1 on: 04/14/2018 06:56 pm »
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.
« Last Edit: 04/14/2018 07:00 pm by Star One »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #2 on: 04/14/2018 10:08 pm »
This will not be civilian related. BAE will make sure of that.
BAe have less than a 20% stake in the company.
Quote from: Star One
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.
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 One
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.
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 One
Skylon 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.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Star One

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Reaction engines Flight Test Vehicle speculation
« Reply #3 on: 04/14/2018 11:34 pm »
This will not be civilian related. BAE will make sure of that.
BAe have less than a 20% stake in the company.
Quote from: Star One
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.
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 One
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.
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 One
Skylon 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.

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.

Quote
BAE’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.
« Last Edit: 04/14/2018 11:53 pm by Star One »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #4 on: 04/15/2018 09:57 am »
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.
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 One
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.
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 One
Quote
BAE’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 One
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.
Which won't need a Flight Test Vehicle. So not really relevant to this topic.
Quote from: Star One
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.
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.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Star One

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Reaction engines Flight Test Vehicle speculation
« Reply #5 on: 04/15/2018 12:17 pm »
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.
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 One
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.
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 One
Quote
BAE’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 One
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.
Which won't need a Flight Test Vehicle. So not really relevant to this topic.
Quote from: Star One
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.
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.
« Last Edit: 04/15/2018 12:21 pm by Star One »

Offline Phillip Clark

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #6 on: 04/15/2018 10:00 pm »
Has anyone considered asking Reaction Engines about this?   I am sure that alan Bond would tell, if he's able to.
I've always been crazy but it's kept me from going insane - WJ.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #7 on: 04/16/2018 07:20 am »
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.
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.

MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Star One

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #8 on: 04/16/2018 11:41 am »
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.
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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #9 on: 04/16/2018 07:25 pm »

I’d thought post #7 probably suggests the best route to your OP.
No.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Asteroza

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #10 on: 04/16/2018 11:11 pm »
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?)

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #11 on: 04/17/2018 07:11 am »
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?)
This is where it gets tricky.  The 2nd file I linked to shows part of the actual D-21's internal structure. It's a series of frames running across the vehicle with a big hole punched through all of them. The original ramjet duct ran through the hole. The first, last and 2 middle frames ran right up to the duct. These were the original JP7 fuel tanks. NASA's planned DRACO installation would have put a (roughly elongated C section) tank in this gap and left the original tanks in place for JP7.

Note 2 things.
This is how Lockheed built it. REL have shown roughly the same shape. It's internal structure could (should?) be completely different.
DRACO's goal was to test up to M6 also but the feasibility study warned the D-21 was built out of Titanium and only really good up to M4, unless the skin was thicker and the leading edge TPS improved.

TBH I was pretty shocked when they planned to wrap the LOX tank around  the engine duct, given it's going to be a bit warm.  :) I can only presume that as long as it's not in actual contact  then the air (probably GN2 or GAr IRL) and some fibre insulation would be sufficient to keep it cool, given the LOX tank on the F9 booster seems to be protected by nothing much more than a thick coat of pain.  :o

But LH2 is not going to be so easy to deal with. AFAIK All LH2 proposals (including airliner designs from the mid 70's) wanted to keep it in one block, either in a big fuselage tank or a long fuselage "hump" running on top of the fuselage.
LH2 is not dense and it really needs volume.  The upside is this design is not pressure stabilized. It relies on the static strength of the materials. the D-21 DRACO conversion planned to run the LOX tank at about 1.5psi above the ambient pressure (which would not have been high at its launch altitude on a B52.

Moving to Methane helps the coldness issue a bit but then you lose LH2's great shc (4x that of water, which is excellent to begin with). OTOH REL plan on both cryogens to be sub cooled, which reduces burst issues due to heat leaks.

Basically monocoque construction does not work too well with temperature gradients this extreme. This is where you have to ask yourself "Do I really need minimum surface area cylinders or spheres inside the moldline, or could I go with a  low pressure more-or-less conformal tank with a layer of insulation between?"
BTW the SS301 used to make the Centaur tanks has 1/10 the thermal conductivity of Aluminium and very good weld properties.

For on orbit storage REL have done some work with a LH2 tank housing LO2 and LH2 for the on orbit RCS. The LHe vaporizes, cooling the internal LO2 and LH2 further, which is just what you want.  But LHe is an ever bigger PITA to keep cold on Earth.

Hmm. Perhaps separate LH2 tank inside LO2 tank either side of the duct? With internal partitions for CoG control.

This also raises the question of wheather they build it with the Skylon structural baseline of SiC reinforced Titanium trusses with SiC reinforced ceramic skins. It sounds exotic, but really, are there any options that are less exotic, that can handle the mass and thermal issues as well?

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.

It's also now clear from the presentation the engineers in charge of the test site that the test engine will not fly. It will generate the test data for that engine.

I was curious about this as once you've designed an engine the second copy of it is likely to be a lot less expensive, and something looking rather more Skylon like (whatever its made of internally) looks a simpler bet to solving the LH2 storage problem, along with various other fringe benefits (confirming the layout, aerodynamics, plume heating etc). That said whatever the FTV it will teach a lot of lessons about how to operate a HTOL reusable LO2/LH2 or Methane fueled vehicle.
« Last Edit: 04/17/2018 07:27 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline speedevil

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #12 on: 04/17/2018 12:21 pm »
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.
Addressing only this part, 2.5KVA*10 minutes = a couple of kilos of batteries.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #13 on: 04/17/2018 03:08 pm »
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.
Addressing only this part, 2.5KVA*10 minutes = a couple of kilos of batteries.
Noted.
Batteries and a ram air driven generator were the planned power source for the DRACO conversion back in 1999. Obviously the battery tech has moved on a bit since then.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline RanulfC

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #14 on: 04/18/2018 12:38 am »
JS19 wrote:
Quote
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. :)

Works for me

Quote
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.

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:
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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.

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.

Quote
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.

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)

Quote
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.

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:
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Has 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.htm
https://motherboard.vice.com/en_us/article/ezvj4j/the-747-to-space-that-never-was
https://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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Star One

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #15 on: 04/18/2018 07:32 am »
JS19 wrote:
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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. :)

Works for me

Quote
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.

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:
Quote
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.

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.

Quote
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.

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)

Quote
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.

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:
Quote
Has 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.htm
https://motherboard.vice.com/en_us/article/ezvj4j/the-747-to-space-that-never-was
https://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 suggest you read any history of DARPA before suggesting they do anything civilian, if they do it’s accidental rather intentional.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #16 on: 04/18/2018 08:36 am »
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?)
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.
Quote from: RanulfC
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'?
Indeed.  I think the DRACO programme was relatively small scale and NASA had looked at doing LASRE on the back of one of their SR71's. Basically a D-21 was the closest thing they could get OTS. The study made no bones that M3 was OK, they were probably good to M4.5, but after that....
Quote from: RanulfC
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.
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).
Quote from: RanulfC
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 :) )
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.
Quote from: RanulfC
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.
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.
Quote from: RanulfC
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.
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.  :)
Quote from: RanulfC
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.
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.
Quote from: RanulfC
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.
Agreed.  But now you have 2 goals.
1) Build a vehicle that can test the engine/inlet over its planned Mach and altitude range
2) 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 repairability 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.

Quote from: RanulfC
(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.
Of those the sensors thing might be got round by data transfer from reconnaissance satellites but that doesn't crack any of the other issues. 14 000 miles but at what speed? I know weather survey drones have been designed for at least 12-24 hour endurance but those things have propellers. The D-21 was not in flight refueled either and a 20tonne thrust engine (44 000lbf) would be quite a lot larger vehicle. Protecting any payload is going to be kind of tough (you know some of one of those propellants is going to a cooling package for the the equipment at some point). Making it deploy something in mid flight is going to be a royal PITA.

Quote from: RanulfC
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.
And it wouldn't be the first time that's happened either.  :(

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.

Quote from: RanulfC
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.
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.  :(

Quote from: RanulfC
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.
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?

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/expendabilty calculation?

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?

Quote from: RanulfC
Star One wrote:
Quote
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.

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.
I do note that SABRE 4 lets you run air in the pre burner and has separate air breathing and rocket combustion chambers. In principle you can do air breathing flight exclusively, but I always thought Scimitar was more "tuned" to the air breathing role.
Quote from: RanulfC
Quote
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.

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)
Good point. I'd never considered RASCAL from that PoV.
Quote from: RanulfC
Quote
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.

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.
A lesson the developers of Concorde learned the hard way. Only air bases might tolerate it, and that's got to be doubtful. 

Quote from: RanulfC

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:
Quote
Has 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 :)

Ho, ho.   :)
Quote from: RanulfC
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.htm
https://motherboard.vice.com/en_us/article/ezvj4j/the-747-to-space-that-never-was
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790010900.pdf (page 73)
What a beast.  :o

Unfortunately that's the sort of vehicle that makes REL's claims and goals that much harder for skeptics to believe ("doubters" won't believe them anyway).  :(
Quote from: RanulfC
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)
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.
Quote from: RanulfC
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?
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.

« Last Edit: 04/18/2018 04:19 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #17 on: 04/18/2018 03:15 pm »
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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #18 on: 04/18/2018 04:08 pm »
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).
More importantly a place to put a big LH2 tank which is not a funny shape.
Quote from: Katana
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.
No. Those are the booster rockets to get it to ramjet operating speed.
Quote from: Katana
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.
True. Also the JP7 was fairly easy to store in any shape of tank.  LH2 is less forgiving.
Quote from: Katana
Having LH2 tanks around the engine is seeking trouble for a test vehicle.
It seems an awful lot of work for the ability to inherit what is at best only a partial aerodynamic database (especially if you want to reuse the vehicle).
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #19 on: 04/20/2018 08:37 am »
To give some idea of the sort of information people might want to get from a FTV this is a description of the 
X-15's telemetry setup.

It would be interesting to find out how many of the questions the X-15 collected data on are still relevant today. 

Obviously the FTV's goal is primarily to flight test the SABRE engine and its inlet, so I wouldn't expect it to have anything like the 590Kg (1300lb) allocated to flight test instrumentation the X-15 had. Most of this was prepared away from the aircraft and mounted onto an "elevator" pallet for installation into the instrument bay.

OTOH it is true that such hardware has become much smaller and lighter in the half century since the X-15 last flew. Although I'm not sure if a combined pressure and temperature sensor operating over the needed range exists. For this environment I think Low or High Temperature Cofired Ceramic would be a better technology than Silicon based MEMS. No one is going to be doing multi channel recording by deflecting light beams with mirrors onto film stock, when you can record onto a 32256GB micro SD card today.

As for its construction one technique I'd not seen to help construct leading edges is the notion of prestressing them,  although it never seems to have been tried in practice it looks like quite a good way to save mass, especially given that carbon fibre was still a lab curiosity when the report was written.

Other potential design features would be making the body as a Sears Haack shape for minimal drag (as Skylon does) and possibly use winglets to lower drag further (as they won't have to withstand full reentry).
« Last Edit: 12/06/2020 06:34 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline RanulfC

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #20 on: 04/28/2018 08:43 pm »
Katana wrote:
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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).

I'd also point out it would give the fuselage construction scheme REL has suggested a chance to be used :) With the later design, (for example the last version produced the X-7A-3/XQ-5/AQM-60A) and updated materials it probably wouldn't be difficult to hit speeds above Mach-6. You'd need to protect

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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.

The X-7B was canceled before flight and was a 'standard' (single engine) configuration that was to test guidance and control (GnC) systems. You may be confusing the later X-7A-3 models which had two under-wing rocket boosters instead of the large tail booster to allow semi-internal carry on the B-29 mother ship. (See: http://www.designation-systems.net/dusrm/m-60.html)

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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.

Well stealth isn't an option for anything travelling above Mach-2 really :) But the others are correct as the much more recent RATTLRS airframe shows: http://www.designation-systems.net/dusrm/app4/rattlrs.html
Note it has even less 'wing' than the D-21 so probably not very helpful :)

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Having LH2 tanks around the engine is seeking trouble for a test vehicle.

Keep in mind folks the tankage wraps around the inlet DUCT not the engine which is at the very back of the vehicle :)
Here's a picture of the engine removed from one drone for separate display:
http://roadrunnersinternationale.com/d-21_ramjet.html
Details: http://roadrunnersinternationale.com/d_21/d-21.html
Removal: http://roadrunnersinternationale.com/d_21/d-21_removal.html

It's actually about 'half' a standard RJ43 with a quite different centerbody, (white object in the photo's, which BTW includes magnesium and thorium making it slightly radioactive!) because it uses the D-21 inlet and ducting unlike the 'integral' inlet and fixed spike of the standard RJ43. Also unlike the standard RJ43 it incorperated a 'restartable' ignition system (using TEB the same as the SR-71 and the Falcon-9 rocket btw :) ) and a more sophsitcated fuel flow and operations controller due to using the D-21 inlet system.

And in general note the size comparision between the D-21 and the NASA F-104 and T-38.


Star One wrote:
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I suggest you read any history of DARPA before suggesting they do anything civilian, if they do it's accidental rather intentional.

I'm very well aware of the history and operations of DARPA and if you'd read what I wrote you would see I never said they "do" civilian work but that many projects have civilian as well as military applications and this is by design as part of DARPA's charter is to explore military AND civilian applications of advanced technology. Military work is of course the core priority but in order to perform that work DARPA has to contract through and work with civilian agencies and organizations and is encouraged to allow cross-pollination and expansion of non-classified projects with those same groups. The SABRE FTV is just such a case as it has limited military application, (space launch) and therefore is neither classified nor restricted and is being treated as such by DARPA and AFRL.

Again, SABRE brings very little to the 'table' for militayr missions OTHER than Space Launch so it's direct military value is only 'played-up' for funding purposes or by those who see any support by the military as being directly tied to the 'latest' weapons fad. Let me break it down again;

There are three basic areas where the military "needs" a very fast, high flying platform:
1 ) Space Launch
2) Reconisscene
3) Strike

The SABRE cycle has direct applicabiity to the first one since, (of course) it is the mission it is designed to perform. Hence military interest in the technology being demonstrated to a high level.

SABRE has some applicability to the second mission but very little compared to other forms of propulsion because it has a high operations cost and is not as efficient as more operationally flexible and cheaper systems that are already at a higher TRL. While more work on "deep-cooling" will probably be done with an eye to application the use of LH2 is operationally and economically far less atractive than other more workable propellants. While Liquid Methane is an option the miliitary frankly would prefer a much more operationally flexible and available propelant based on hydrocarbon. Now if large segments of the civilian aerospace industry move to establish and utilize crygenic fuels such as methane or hydrogen then of course the military will tap into that infrastrcuturre but they have experience that shows utilizing 'specialtiy' propellants even in small quanties and for specific missions is not cost effective and signifincalty increses operational costs and difficulties.

In addition, despite the hype over hypersonics, a high-supersonic or hypersonic platform is neither 'stealthy' nor invulnerable to interception. Much has been made about no one every 'hitting' (or coming close to) an SR-71 in flight. But to really understand this you need to understand that for the most part none of these 'attempts' were able to generate direct intercepts or even get very close to the aircraft in flight. The flights WERE closely tracked and the SR-71s never directly overflew the targets on most missions, getting most information by 'side' or oblique scans of the area. Those that did overfly targets were in areas where it was known in advancce that no possible aircraft or defenses encounted could be a threat.

Part of the reason for retiring the SR-71 is to many nations now have aircraft capable of reaching altituds where they could launch a missile* that would have a very high chance of sucessfully engaging a very fast, very high flying overflight or even a near-overflight. Vehicles at 100,000ft are vulnerable to current aircraft and missile combinations and given any decent air defense radar system a hypersonic platform above 80,000ft (where they have to operate due to aerodynamic heating) is going to be highly visible to even passive IR tracking systems let alone radar. (And just for an FYI effective 'stealth' coatings are incompatable with high speed flight)

*Something people who assume 'hypersonics-is-the-new-stealth' need to know is you have to fly HIGH to sustain hypersonic speed, and that makes you visible a long way off. Further a main reason that missiles were not effective at very high altitude was due to having aerodynamic control surfaces (fins) which were not effective in the thin air. Most intercept missiles today and in the future are moving to reducing or removing the control sufaces in favor of vectored thrust and/or thruster controls which allow much more radical manuevers than 'fins'. This also allows them to be HIGHLY more effective at extreme altitudes where the air is to thin for fins to work! The only way you get 'low reaction time' is to fly at hypersonic speeds at less than 1000 feet, (actually less than 500 feet works best) but think for just second on how dense the air is at that altitude and how tough your vehicle has to be to survive that environment. The PLUTO/SLAM 'only' did Mach-3 at less than 1000 ft and its shockwave was calculated, (and planned) to be a 'weapon' all by itself!

Finally we have the "strike" mission which entails the ability to locate, engage and destroy targets on the ground which has all the issues of "reconisncee" and adds the need to be able to deploy weapons at high speed and altitude. (And gets worse if your platform is itself supposed to be the 'weapon' and needs to engage the target at the surface) Now keep in mind the whole basis that advocates of hypersonic recon/strike vehicles have always based the concept on was NOT 'stealth' or the ability of the vehicle to arrive over the target without being detected. This is all 'new' hyperbole which conflates hypersonic speed as the 'new stealth' and is frankly unsupportable as well as unworkable. Hypersonic recon/strike as always about being able to cover 'more' area by the virtue of flying so high and fast that any 'located' (recon) target could not remove itself from the engegement area (strike) so mobile targets could be more easily engaged. Even so it was quite obvious that the platform would be both visible and engageable itself but at the time these systems were proposed, (from the late 50s through the mid-80s) engagment with existing defensive systems was 'assumed' to be difficult if not impossible. Similarly the only weapons 'assumed' to be deployed by these hypersonic systems that could be effectivly used were nuclear in nature because no weapon of the period could be effectivly guided to the target from a hypersonic platform.

While effectie guidance can be done now from off-platform resources, (GPS, and other systems such as local laser guidance etc) delivery by hypersonic platform still requires the 'target' be located and isolated which presents issue as noted above. Things get worse not better if the hypersonic platform IS the weapon because once it begins an attack run it LOSES the ability to track the target. While granting any target can't move very 'far' once the attack run begins without a nuclear warhead anything less than a direct hit is problematical since in most cases hypersonic weapons have smaller than average or no warhead and depend much more on actual physical impact. Why does the weapon lose the target? Because no sensor can 'see' through the rapidly increasing aerodynamic heating effect around the weapon. The only way to 'guide' such a weapon is again by some off-platform sensor and guidance system which is effectivly limited to what bandwidth you can push through the rear-end of the heating. (No GPS won't work because the target is MOBILE and can in fact 'move' sufficently from a position in the time it takes a Mach-6 projectile to get from 100,000ft to the surface to possibly generate a 'miss' from the original target point. GPS will put a weapon on a set of coordinates only which is why an 'active' targeting system is required)

Lastly there is the 'size' factor to be considered. Nothinig powered by LH2 is going to be 'small' and even Liquid Methane is still about twice the area of a hydrocarbon fueled vehicle. You can't 'launch' such a vehicle from any standard aircraft without it being externally carried and any aircraft that does carry it is going to be huge, subsonic and rather obvious to any defender.
Keep in mind the 'range' factor as well. Whereas hydrocarbon fueled vehicles such as the D-21 or RATTLRS have ranges of 600 to 3, 000 miles a similar sized LH2 or Methane powered vehicle will not. It could have several hundred miles or up to 500 miles if it uses some ballistic 'coasting' flight. And it is going to be as BIG as a manned fighter jet to get THAT much range. And don't forget it will also require high operations support due to the cryogenic propellant.

Final nail in the coffin? You don't NEED it, there are far more cost effective and capable propulsion systems for both 'recon' and 'strike' platforms the we KNOW work and work quite well. The main drawback over the years has been fixation on certain propulsion types (Scramjet) as the 'only' type that can do the mission when in fact "real-world" testing has shown that 'simple' subsonic combustion ramjets, (ALSAM) advanced turbojets, (RATTLRS) or even rockets (Falcon) have shown you don't need either Scramjets or the SABRE to get the job done. Deep-Cooling intake air for the purposes of allowing sustained hypersonic flight DO have some military applications in that it could allow a recon platform of sufficient size to be operated but the SABRE cycle isn't the one you want unless that platform is going into suborbital or orbital flight. It's simiply not the best soluton to the problems. But again you also don't NEED it as we've been studying hypersonic flight for decades and "propulsion" is the least of the issues and always has been.

There is a very good and obvious, (if one cares to look) why so many "Blackbird" follow-ons have never actually flown. It's the same reason no one bothers to field supersonic bombers in great numbers in that the "mission" is only one aspect of the overall operational environment and frankly the faster and higher you go the more limited it becomes because everyone can see you and see exactly where you're going.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline RanulfC

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #21 on: 04/28/2018 08:50 pm »
JS19 wrote:
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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.

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.

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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 was hoping for some 'new' and possibly more detailed information but ah well :)

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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).

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...

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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.

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? :) )

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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.

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.

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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.

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 :)

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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. :)

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.

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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 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)

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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.

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.html

And of course the NF-104:
https://en.wikipedia.org/wiki/Lockheed_NF-104A

But 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.

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Agreed. But now you have 2 goals.
1) Build a vehicle that can test the engine/inlet over its planned Mach and altitude range
2) Design it as a pre-production prototype for an actual vehicle with a specific purpose.

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...

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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 '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.

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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?

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" :)

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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.

In theory anyway :)

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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

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.

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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.

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.

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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?

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?

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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?

I'd be surprised if it wasn't using 'heat-pipes' to the fuel for a heat sink :)

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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?

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.

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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.

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 :)

Quote
This being a UK project I think the question is "how small can they make a SABRE engine affordably?" :)

Well that IS the reason you reach out to moneybag.. er that is the US right? ;)

Quote
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 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.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #22 on: 04/29/2018 10:45 am »
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.
Impressive. I'm guessing inlet technology to run from M0-5.5+ will be even more critical.
Quote from: RanulfC
I was hoping for some 'new' and possibly more detailed information but ah well :)
The closest was a description of (roughly) a miniature Skylon, 3.5m span x 9m long, which IIRC was the Methane fueled inlet test vehicle. It's target was a 1000Kg mass.

Quote from: RanulfC
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...
Actually BAe do build complete airframes. The trouble is the only two that comes to mind as new build are the "Hawk" trainers and the Typhoon. Hawk is a 40 year old design. Typhoon, being a multi national European design will have issues pending Brexit.
Quote from: RanulfC
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...)
Exactly. Hence the critical need to get a vehicle to fly as much as possible of the trajectory, ideally beyond the AB/Rocket transition.
Quote from: RanulfC
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? :) )
It seems the maths of SCramjets has always been shown to work. It's just that pesky engineering.
TBH to LACE and "cryojet" designs (which IIRC is what SABRE would be classified by William Escher as).frost control and the size of the precooler have been the issues Historical designs had tubes 10x the dia of the REL types and what is basically a more "fractal" plumbing layout.
I think the question is how far did earlier designs manage to share the core systems. It would seem not much, whereas SABRE shares inlets, pumps, pre-burners etc. It's only more recently they've gone with more separation of thrust chambers, giving an AB thrust chamber much closer to conventional gas turbine pressures.

Quote from: RanulfC
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.
Yes, the only part of the D-21 designed for recovery was the "hatch" housing all the control gear, sensors etc. Apart from the fact it needs one engine and can hit more than M3 (but not sure how much more than) the D-21 layout doesn't have that much going for it as a model for a M6 test vehicle.
Quote from: RanulfC
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 :)
I suspected it was something like that.

Quote from: RanulfC
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...
I like that as well. :-)
Quote from: RanulfC
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.
This is where it gets tricky.
The trouble is all the high mach designs I know of are
a) Air launched
b) Used actively cooled walls (mostly M3 and higher airliner studies).
a)Means they don't have to worry too much about take off mass and b is quite a complex design (interestingly they seemd to have gone with direct cooling from the LH2 in the tanks, rather than Helium loops (which in hindsight looks like asking for trouble to me). 

So maybe the simplest answer is to you use the construction technique they are planning to use on Skylon?

I will note that the FTV's goal is not that of the X-15. The core goal of the X-15 was to find out what happens to an airframe when it's "soaked" to thermal equilibrium with the environment. AFAIk the nearest thing in the UK to this was the Bristol 188, but apparently it didn't have the endurance to reach full soaking temperature.

This "Over and under" style has been used in a few ramjet missiles and recon drones up to about M4 (with the X-7). While I think it solves the LH2 storage issue the X-15 showed just how damaging shock/shock interferrence can be with the dummy SCramjet, mostly it seems not from the spike on the front, but from the outer edge of the inlet cowling hitting the airframe and fin shocks. There is also the issue this engine will definitely be running and therefor generating an exhaust plume

The obvious approach is to put the engine nacelle as far back as possible, like the V1. However now you're back in HOTOL territory, with high forebody lift with a back end heavy shape.
Quote from: RanulfC
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)
Highly suspicious. That said the X-15 "payload" was 1300lbs of instrumentation. Because of how early they started the planning for this they went with film cameras recording osciloscope traces rather than digital tape recorders. Obviously today with micro SD cards running 64GB you can collect a fair bit of information in a considerably smaller package.
Quote from: RanulfC
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.html

And of course the NF-104:
https://en.wikipedia.org/wiki/Lockheed_NF-104A

But 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.
I'd not heard of the T38 conversion. Very dramatic. Big doubts about the structural heating theough. :-( .
I think both RC and full AGV technology has come a very long way, but the list of vehicles possibly available is pretty small. Throw in the need to run LH2/LO2 (or even Methane) and it shrinks even further.

Quote from: RanulfC
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...
My instinct with this is it depends to what degree "hooks" allow a design to transition into something more "operational."
Note that (according to Jenkins book) the core X-15 mission goals were done by 1963. The rest were flights on behalf of other people, or seperately funded, to test equipment, study the upper atmosphere etc.
In the same way I think there are other groups around the world who would be interested in fying their instrumentation not as an operational vehicle, but to help them design theirs.

Quote from: RanulfC
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.
Personally I think the itearative nature of inlet development makes a reusable vehicle cheaper in the long run. The desire to make an LH2 monocoque seems to skew all attempts, when separating the LH2 as an inner tank makes life a lot simpler.

Quote from: RanulfC
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.
Which IMHO is how an X programme should be.
Quote from: RanulfC
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.
All true, sadly (with the exception that the X-33 somehow "proves" SSTO is impossible, when all it shows is something is impossible if you impose enough irrelevent and unneccessary constraints).
Quote from: RanulfC
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" :)
Good point. The price of wisdom is enternal vigilance against learning the wrong lessons. :-( .
Quote from: RanulfC

Quote
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.

In theory anyway :)
That's basically what I'm suggesting. Of course the devils in the details.....

Quote from: RanulfC
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.
True. It will depend if REL is funding the FTV or there is a consortium in place. That's when the issue of governence comes in and things can get tricky. Again.
Quote from: RanulfC
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.
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. :-(.

Quote from: RanulfC
The 'figures' are available and with enough creative accounting they will tell what every result you want them to :)
Now that I can believe. :-( .
Quote from: RanulfC
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.
I think that's a bit harsh. AFAIK it met all core goals. especially the prolonged effect on airframe heating. The real damage happened when they mounted that dummy SCramje to the lower fin. No one saw the massive effects of shock/shock interferrence heating.
Quote from: RanulfC
"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?
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. :-( .

Quote from: RanulfC
I'd be surprised if it wasn't using 'heat-pipes' to the fuel for a heat sink :)
That's the weird thing now I come to think of it. They seem to cool the skin panels directly from the LH2 supply, no intermediate HX. No heat pipes. It seems hard to believe no one considers this an issue.
Quote from: RanulfC
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.
Fair point. I guess the question is wheather you're validating what you already know to be true, or you're finding out what "true" means?
Quote from: RanulfC

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.
We may be talking at cross purposes here.
I'm talking about "users" in the X-15 sense of additional research groups who might want to install other instrumentation. AFAIK most of the people who have an interest in this area use sounding rockets and balloons. Sounding rockets don't really do constant altitude and balloons are difficult to recover.
My favorite example was the UV spectrometer looking through a window in the top of the telemetry hardware bay.  This would have been completely impossible without the bay being designed for access from above, hence looking up at the sky was relatively easy.

My interest is in what other early design choices could make the FTV more "experimenter friendly" ?

Quote from: RanulfC
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 :)
It's a Gordian Knot alright. But you've got to start somewhere. Only making a single engine is a serious limit on options here. With two they'd be lloking at something a lot more Skylon like. With three they might be able to approach the EU to do some structures testing. LAPCAT looked at the engines for a hypersonic aircraft but there was a sibling programme for the vehicle structure (can't recall the name. Choose any of the usual adjectives and nouns for this stuff and I'm pretty sure you'll a project that's used that combination over the decades. :-( ).
I wonder if it's too late for REL to set up EU office in say Bruxxels staffed with French and German speakers?
Quote from: RanulfC
Well that IS the reason you reach out to moneybag.. er that is the US right? ;)
Well, you are the country that gave the world "No Bucks, no Buck Rogers" :-)
Quote from: RanulfC
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.
My experience in other areas is that you can usually come up with two or three ways to do something. On paper they all look about equal. Pros and cons for all of them. Historically this was decided by the core developent team
a) Going to a bar
b) Talking it out
c) Drinking themselves into a stupor
d) Implementing the choise.

Although I'm sure a similar process could be carried out at your nearest favorite coffee house.

I can understand some REL fearing the outcome but I don't think any fear the process.
Some have waited half a lifetime to demonstrate their proposals are correct. Younger staff memebers weren't born when REL was founded. They have (literally) waited a lifetime for their efforts to pay off.
Fear of getting it wrong? Certainly.
Fear of trying. Never.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #23 on: 04/29/2018 03:42 pm »
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. :-( .

I suspect NOTHING between M5 and M10 could satisfy the “speed and Isp requirements” of end user. The actual need of end user is even NOT  "speed and isp". Especially given the revolutionary success (and effort) of recon satellites and stealth subsonic cruise weapons (on the side of microelectronics), while hypersonic excludes stealth.

But SCramjet developers could justify their activity as "technology demonstrators", while testing conventional ramjets for top speed can't.

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.
« Last Edit: 04/29/2018 04:48 pm by Katana »

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #24 on: 04/29/2018 05:02 pm »
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.

Both X-7 and X-15 are proved worthy to be reuseable, while X-43 and X-51 are proved worthy to be expendable.

X-7 provide iterative testing of RJ43 ramjet (for BOMARC) from concept to product. Similar Bumblebee program for Talos ramjet costed a great number of expendable protypes, and left out many problems in operational version, leading to late product modification.

https://www.okieboat.com/Talos%20history.html

X-15 provided system level testing for manned hypersonic flight before Shuttle.

X-43 and X-51 had little goal other than scramjet and airframe, while their expendable solid boosters are large and expensive, maybe more expensive than vehicle.

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

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.
« Last Edit: 04/29/2018 05:15 pm by Katana »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #25 on: 04/29/2018 08:04 pm »
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.
Not really. Supersonic combustion was demonstrated at Johns Hopkins in 1960.  It's just very difficult to get any actual net thrust out of it.

Quote from: Katana
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?
The first A in NASA is "Aeronautics," so yes it can be part of their task.
Quote from: Katana
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.
Actually a bit doubtful. The study on the D-21 to carry a new air breathing engine reckoned it could go to M4.5, but above that they were doubtful the structure could survive. The target of DRACO was to go to M6. Since the D-21 was structurally similar to the SR71 it is likely the SR71's limits would be quite similar.
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
In what way?

X30 blew close to $3Bn and produced nothing. The whole US SCramjet effort has (over 6 decades) swallowed  $10Bn+ in 2018 $ and failed to produced a single operational vehicle.

HOTOL cost less than $10m and paved the way for a step change in Isp and an actually viable SSTO.
In fact REL has no interest in building a "flight demonstrator," they want to build a vehicle they can sell.
That's the difference between companies that want to build products and researchers who want to build research programmes.

$3Bn would have had a full size SABRE running by now.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #26 on: 04/30/2018 05:42 am »
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.
« Last Edit: 04/30/2018 05:49 am by Katana »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #27 on: 04/30/2018 06:28 am »
For structure surviveability, airframe design of D-21 with Inconel material of X-15 should be capable of going to speed near X-15.
Possibly. But LH2 is both much colder and much more voluminous than JP7. It's not the materials, it's the actual layout that seems unfriendly to the task.
Quote from: Katana
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.
True. But then you have the limitations of the turboramjet, which are known and not really relevant to this thread.

For some idea of the sort of parameters the FTV might collect here is the initial design study for the SCramjet that crashed the X-15 A2.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650011864.pdf

I found the issues around collecting valid pressure reading particularly interesting. I wonder how far we've come in 5 decades?
[EDIT
This paper discusses some of the issues of too slow or too low a resolution sampling system

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19850008594.pdf

applied to the Shuttle Orbiter system. ]
« Last Edit: 04/30/2018 04:56 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline RanulfC

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #28 on: 05/01/2018 04:06 am »
Katana wrote:
Quote
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.

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.

"Conventional" ramjets "top speed" was felt by the majority of engineers that worked with and on them to be in the mid-hypersonic range where Scramjets were only supposed to be beginning 'effective' operation. And considering there is enough practical evidence that such speeds are very likely to be operationally applicable, (ASALM test article reaching Mach-5.5 with a FIXED inlet design and still accelerating for example) the obvious question is why is there an 'assumption' bias against them in favor of Scramjets? Those people have had almost a decade of Scramjet "flights" at this point so in the nature of 'fairness' shouldn't other propulsion schemes get their chance now?

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.

Quote
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.

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)

But let's also be honest that Scramjet research and development is actually NOT going away anytime soon:
https://www.c4isrnet.com/industry/2018/01/24/darpa-envisions-a-hybrid-engine-to-reach-hypersonic-speeds/

Despite the switch in main contractor:
http://www.airforcemag.com/Features/Pages/2018/April%202018/Lockheed-Martin-Gets-928-Million-Hypersonic-Missile-Contract.aspx

ARRW, ("Arrow") will be getting about a third of the money, while the DARPA TBG and HAWC programs will be getting the lion's share of the money.
https://breakingdefense.com/2018/03/dod-boosts-hypersonics-136-in-2019-darpa/ (Which by the way is less than a "billion" despite the headlines saying different) And both the HAWK and Advanced Full Range Engine concepts are planned to use Scramjets so saying "interest" has "ceased" is very misleading. It would be better to say that while 'interest' is still there the requirement for actually developing a hypersonic weapon has moved towards using a more practical, near-term propulsion system than the Scramjet. (Considering the "contract" neither specifies a time-frame or any numbers, both of which are listed as 'undefined' I have my doubt that this is actual 'progress'. Especially since they are attaching things like a new multi-service "AI" development center into the mix as a 'requirement' over and above the propulsion system itself)
https://breakingdefense.com/2018/04/usaf-announces-major-new-hypersonic-weapon-contract/
https://breakingdefense.com/2018/04/pentagon-run-ai-center-coming-hypersonics-work-in-progress/
https://breakingdefense.com/2018/04/big-hypersonic-news-coming-faster-progress-likely-roper/

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/

Quote
For structure survivability, airframe design of D-21 with Inconel material of X-15 should be capable of going to speed near X-15.

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.

Quote
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.

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.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #29 on: 05/01/2018 05:05 pm »
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.
Indeed. IMHO there are a number of groups who could benefit from more basic data with which to refine their models/hardware.
Quote from: RanulfC
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 is a very interesting side light on the history of the subject.
Quote from: RanulfC
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.
I've not seen a SCramjet that reached operating speed on anything but a damm big rocket.

Quote from: RanulfC
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)
Agreed. And I'll bet LM are very careful to phrase things with enough get outs to do so.
But this is pretty  OT for the goal of this thread.

Quote from: RanulfC
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/
True. But close to a billion is way more than the usual DARPA grant funding. It actually sounds like they want to build some hardware.  [EDIT Isn't that more like a Phaase 3 award size? ]

Quote from: RanulfC
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.
The DRACO study I quoted seemed pretty confident of M4.5. M5.0+ was pushing it. Pushing it 1.5x its design speed is (I think) pretty good. Pushing it 2x? That's like Peace Jack saying "Yeah. Phantom II can do M4. No worries," while anyone who actually knew about structures is thinking "This is going to be trouble." :-(

Quote from: RanulfC
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.
I think he may be.

I'm thinking in terms of a traditional X programme. Maybe the demo engine is close to viable as a saleable product, but it's goal is to drive the data to design the full scale SABREs, LAPCATs, etc.

The vehicles key goal should remain "Fly the SKYLON trajectory AFAP and do so beyond AB/rocket transition until the rocket has got stable combustion."
Obviously the closer you can match that profile the better for Skylon (or other SABRE LV) concepts.
an "extended" goal would be to see how far you can push the envelope beyond that, given how every m/s in the booster gets you closer to orbit and (assuming a TSTO) one less for the US to produce (at the US trade rate of 1Kg of stage mass gain --> 1Kg of payload loss).

I also think the FTV can help with those "Shouldn't be a problem, but" areas.

I'm thinking of things like automated propellant fill and drain, ideally through the wheel wells to reduce the number of openings in the TPS. Propellant sub cooling (to improve range) and eliminate boil off (or perhaps it should be designed from the start for ZBO over a 2 hour hold period).
Likewise (possibly) upgrading to water cooled brakes with a functional test of the system. Potentially a vehicle ending experiment but very useful for the follow on programme given the substantial mass of brake systems (cutting 500Kg from the dead weigh of an A380 over it's 30 year operating life...)
« Last Edit: 05/02/2018 06:24 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #30 on: 05/01/2018 05:35 pm »
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^3
Assuming 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 are
a) 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?
« Last Edit: 05/01/2018 06:00 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #31 on: 05/03/2018 12:00 am »
The biggest problem about a M6 vehicle is no customer really needs it, either for recon aircraft or strike missile. The absence of real need and real programs left the area to be occupied by SCramjet researchers who only want to build research programs.

For old ramjet / turboramjet, they are capable to reach M6 with moderate cost. But choice of whether to use them are decided by weapon manufacturers, they favor smart and stealth subsonic systems instead of going stupidly fast and hot.

Scramjet behaves even worse, but could be justified as a fancy research program and pushed by interest groups behind it. The more fancy and impractical, the more possibility of getting funded when there is no real customer need to achieve.

Same problem exists for SABRESkylon if REL want to sell the vehicle, though considering customer need too early may spoil the test vehicle.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #32 on: 05/03/2018 12:07 am »
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^3
Assuming 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 are
a) 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?

Between X7 and D21: BOMARC / SR71 /original Skylon style. Wing mounted engines, and central fuselege almost fully occupied by tanks.

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.
« Last Edit: 05/03/2018 12:18 am by Katana »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #33 on: 05/03/2018 06:14 am »
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.
Actually it would have very limited value to REL either.
AFAIK REL does not have the facilities on the ground to demonstrate air breathing to rocket transition on the ground.
Quote from: Katana
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.
The number 1 purpose of this vehicle is to demonstrate the parts of the SABRE cycle that are different from a  conventional rocket engine and to gather data to help REL design any future engine.
Once that is achieved then in principal however high a Mach number it operates too is a problem of Nacelle and aerodynamics and materials design. The engine is running entirely on internal propellants by then.

This is not a development programme for a vehicle. When I refer to customers I mean research groups who would like to use it to gather data over part of the flight path.
What data they might want, and what features they might like in the vehicle to collect it, are very on topic for this thread.
« Last Edit: 05/03/2018 06:46 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #34 on: 05/03/2018 01:01 pm »
Flight profile 1: airbreathing to M5, rocket to M7~10, reentry.
Flight profile 2: airbreathing to M5, rocket to M7~10, rocket deceleration to M5, reentry.

BTW is it possible for SABRE to operate in VTVL mode without wings?

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #35 on: 05/03/2018 04:36 pm »
BTW is it possible for SABRE to operate in VTVL mode without wings?
In principle yes.

Why would you want to?
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #36 on: 05/04/2018 09:58 am »
BTW 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #37 on: 05/04/2018 05:31 pm »
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.
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 by
a) 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.
« Last Edit: 05/04/2018 05:40 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #38 on: 05/05/2018 06:06 am »
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.
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 by
a) 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.
« Last Edit: 05/05/2018 06:17 am by Katana »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #39 on: 05/05/2018 10:08 am »
Two 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: Katana
The 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: Katana
Even 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.

« Last Edit: 05/05/2018 10:17 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline knowles2

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #40 on: 05/05/2018 11:25 am »
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.pdf
and this.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990110312.pdf

Basically 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?
It all about funding, if REL can go for the mini skylon concept then they will because it means they go from mini to full scale pretty quickly.

But if they don't have the money for that they will knock up the cheapest vehicle they can to test their engine. Which will most likely be something that complete avoids anything use or developed in the US to avoid Itar.

Thing is they are a engine seller, they aren't interesting in building the actual craft, at least not yet, so all they need is something that proves the engines flies and at least make to sub orbit. You should be able to knock something up that does that for less than a 100 million.

Offline knowles2

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #41 on: 05/05/2018 11:41 am »
Quote
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.
They are working with DARPA because they are willing to pay for testing of their pre cooler in a hypersonic tunnel. They are hoping this piece of data along with the other testing going on in the UK over the next 2-3 years that will unlock serious money either from BAE/Boeing/RR or from other investment funds around the UK, they want to avoid taking as much US money as possible to avoid getting entangled in ITAR. They

An Reaction Engines is just creating the engine, they want to sale that engine to anyone that wants one, if that includes the military then so be it, they aren't fuss, as long as no this top secret, classified,can't talk to anyone about it type restrictions are place on the program. In a ideal world they would want the military and civilian companies to buy their engines to mount of their own vehicles. Just like RR does.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #42 on: 05/05/2018 11:37 pm »
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 billion

The Darpa funding has a potential phase 3, which covers flight testing (It also explicitly mentions dual use - civilian and military).

« Last Edit: 05/05/2018 11:39 pm by JCRM »

Offline knowles2

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #43 on: 05/06/2018 12:52 am »
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 billion

The Darpa funding has a potential phase 3, which covers flight testing (It also explicitly mentions dual use - civilian and military).
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.

Offline Katana

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #44 on: 05/06/2018 05:26 am »
Two 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: Katana
The 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: Katana
Even 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #45 on: 05/06/2018 06:08 am »
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.
Because the last REL presentation I've seen showed a test vehicle looking like a D-21 drone, whereas earlier ones (designed to fine tune the inlet design) was more Skylon like.  Historical learning curves for aircraft production are that when you double the number of items you drop the cost by 15%.

That said I would expect the precooler would be a 3rd generation unit ( the test stand ones in Colorado and the TF1 stand being the first two generations). The rest would be the second full  iteration of the design.

Pending an announcement from REL the conservative view is they are going to build one flight weight engine to test fly.  :(
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #46 on: 05/06/2018 06:24 am »
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.
This is where it gets complicated. BAe is an investor (and having  an airframe mfg already was a late changed condition of the UK govt grant contract to REL)

TBH I don't believe there are any existing airframe mfgs with experience of the materials REL have baselined for the Skylon airframe, so the fact that BAe is a large military contractor is not a plus point. It basically means they are great at the paperwork of a government contract, like the F35.

No doubt the UK govt were persuaded that having someone who could design such a vehicle would "reduce risk" in their investment.

Personally I would have preferred someone who still built commercial jet aircraft (Bombardier in Belfast for example), but UK "industrial" policy (much like US DoD policy) mashed them all together (along with small arms, artillery, submarines, torpedoes and armored fighting vehicle makers) into BAe.  :(

[EDIT For those curious of what what some of the issue of a hypersonic vehicle are this is a NASA roundup paper of some of the issues (and ways to handle them) from 1968. Note a structural fraction of 25% for hypersonic aircraft was viewed as achievable without the use of a truss structure.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680017975.pdf

What has changed? Well FSW for metal joining, much cheaper  high resolution NDE of parts. Wider experience of diffusion bonding. Maximum operating temperature for some plastics exceeding 250c and some up to 350c. ]
« Last Edit: 05/06/2018 07:56 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #47 on: 05/21/2018 09:20 am »
One problem area for space planes is the hydraulic system. Servicing the one on the Shuttle was a major PITA and needed a dedicated pump to stop it freezing.

All electric actuation looks to be less troublesome, given the wide thermal and pressure operating ranges the control system needs to operate over.  It is already standard on the Vega solid rocket and seems to have worked fine for main nozzle TVC, which calls for a fairly high thrust, high speed (but low angle) drive system. Likewise the X37b seems to be all electric, including all the landing gear associated equipment.

With this in mind I found a British PhD thesis  sponsored by landing gear mfg Messier Dowty (part of Saffran) on health monitoring for electrically actuated landing gear.

https://www.research.manchester.ac.uk/portal/files/54520238/FULL_TEXT.PDF

It mentions a £10m programme funded by the UK Dept of Trade & Industry called ELGEAR targetting this specific area.

Here is a presentation by Messier Dowty's parent company Saffran on the idea of electric landing gear, including brakes and steering.
http://www.icas.org/media/pdf/Workshops/2013/ICAS%20-%20Recent%20Advances%20and%20Future%20Electrical%20Landing%20Gear%20Systems%20Publish.pdf

This is paper from China on some of the detailed issues around this task and some of the type of electric motors that could be used.

http://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/109.PDF

IMHO it would be easier to route electric cabling and cool EMA's than develop high temperature hydraulic actuators, their associated fluid and pump package. 
« Last Edit: 05/21/2018 10:04 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #48 on: 07/16/2018 08:35 pm »
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.
I'd agree.  A two engine vehicle just seems much easier to deal with, in terms of air flow and thrust and CoG shifts.

But the latest renderings show a single engine vehicle.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline knowles2

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #49 on: 07/24/2018 02:29 pm »
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.

Offline Star One

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #50 on: 07/24/2018 03:02 pm »
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.

None of this will happen as Tempest is designed to be sixth generation on a budget. Like with the B-21 in the US the rapid capabilities office running this program is looking to use off the shelf technologies as much as possible.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #51 on: 07/24/2018 07:15 pm »
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.
Indeed. I call "House" on the Buzzword Bingo.  :)
However...
I think electric actuation is a technology that Skylon could use well and is becoming more mature. For the FTV I'm not sure if anything more than batteries would be needed (that are several decades more advanced than the ones planned for the DRACO conversion of the D-21). BTW the big points of what he was talking about are
1) Direct bonding of the magnets to the shaft, a more "unitized" construction
2) Magnets cease to work above their Curie Point, so putting those magnets deep inside the engine means magnet alloys that can operate at high (or higher) temperature.
 
Quote from: knowles2
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. 
Quite likely.
 
Quote from: knowles2
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.
This is rather more doubtful.
"Boundary Layer Control" or "blown flaps" have been demonstrated since the 1950's. The classic example was the "Buccaneer" (probably the closest to the Douglas A4 Skyhawk).

BLC allowed the Buccaneer wing to be 50% smaller that designs with similar specs. This is attractive. OTOH it took a substantial fraction of the engine thrust to do so and of course if the engine fails the consequences are serious. OTOH the wing mass reduction is significant. The question is wheather it is significant enough? [EDIT IE does the reduced vehicle dry mass outweigh the increased risk of losing the payload if there is an engine failure? ]

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.



« Last Edit: 07/26/2018 07:05 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline t43562

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #52 on: 08/02/2018 01:50 am »

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 saw Magma at the BAE Systems display at Farnborough and had a long chat with the gentleman demonstrating it.  He gave me the fluidic thrust vectoring nozzle for the previous aircraft (DEMON) to compare with the one for MAGMA which was 3D printed.

Both were made from Titanium but the DEMON one was about maybe 2KG and the MAGMA one was at most a couple of hundred grams. It was a great surprise.

I don't know about DEMON but the MAGMA one was "only" 2D and it is something that he says has potential to be included in Tempest.  It's like mouth with an (not quite) elliptical opening shape and there are openings at the top and the bottom for gas to be blown to influence the direction of flow of the exhaust.

My memory is that he said DEMON was over 100kg (140?) but that MAGMA is 20kg empty.   This is partly because they worked out how to supply air from the thrust engine instead of having 2 but perhaps mostly because of the carbon airframe.

MAGMA has conventional controls which are used to supplement the fluidics when larger forces are needed.  I think this shows they can perhaps be backups as well.

One of the big innovations in MAGMA was that they worked out that they couldn't supply more air for control but they could supply it at higher speed (supersonic) and this makes their fluidic controls much more efficient than with DEMON.

The main claim about fluidics from the MAGMA representative was that they are much lower maintenance since only a ball valve moves. The fluidic thrust vectoring is also good for this reason - meaning that whatever craft you have is much more likely to have high availability with this kind of thrust vector rather than a mechanical one.   It also pays for the vectoring system to be light because it makes CoG problems much less onerous.
 
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.



Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #53 on: 08/02/2018 07:19 am »
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?
You'd be right but this is not how it works.  The flow is run through piping to vent through the trailing edge of the wings. AIUI SABRE thrust chambers, if not the whole nacelle, will swivel.
The point is that this is a research project. I'm very doubtful that this is necessary to make the design close. Plus I'm not sure SABRE has any provision to divert any of its feed air for other purposes. If it does this could be an option. Historical designs have used similar techniques to cut wing size (which lowers drag as well as T/O mass) but it's another dynamic system that becomes a "Criticality 1" system that simply cannot fail.
Quote from: t43562
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.
Personally I think more could be done with Skylon's wing design. I suspect it is fairly basic in shape and plan. As we move toward construction I think there is room for improvement, while keeping the aerodynamics within the known SoA.

My instinct is the model for this fluidic controls stuff is the acceptance of 2 engine airlines for flight over the oceans. This took a long process of accumulating flight hours to demonstrate the new engines had the reliability to operate for the extended periods needed. It helps this technology can fly in a hybrid configuration, allowing it to accumulate flight hours without failure being catastrophic.

While the current FTV that REL have shown pictures of looks like the Man. U test vehicle I think it adds design issues both to the engine and the vehicle that aren't needed. Conventional controls should be adequate. Also the operating speed range for the FTV and Skylon are way  beyond what the bulk of vehicles fitted with this technology will operate over.  We know aerosurfaces can operate to high Mach numbers, as Buran, Shuttle and the X37b have shown. Outside the atmosphere you need thrusters anyway.
Failure to make fluidic controls work on the FTV at M3+ wouldn't mean they aren't completely viable at 0-M2+, which is pretty much what all military (and < M1 for all civil) aircraft fly at.
« Last Edit: 08/05/2018 09:47 am by john smith 19 »
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Offline Asteroza

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #54 on: 08/05/2018 11:48 pm »
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?

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #55 on: 08/08/2018 09:50 pm »
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.
And you'd be right. Multiplied by the TRL of the technology. Well understood and used many times over the last 60+ years versus (essentially) developed over the last decade with limited funding.

The hardware is not the whole story.  :( You must consider things like the design tools available to design new versions. Mature for mechanical TVC. But for fluidic, with supersonic flows? And bleeding off thrust right during take off?  That could turn a slight engine under performance into a crash (or it might not. The new tech brings greatly increased uncertainty).

Basically your swapping a well understood steering method, with equally well understood design methods, for a new approach that's have very limited hardware validation and a high risk of "Unknown unknowns" when you design and operate it over a range of at least 0-M6

The benefits, in terms of mass reduction and reliability increase by reducing the number of individual parts, would have to be huge to justify the (substantially) greater risk of using it. If they are not it's way more risk of the design not working (and over running on schedule and budget) for just too little gain.
Maybe  it can, but I'm very skeptical the case closes, in which case it would be novelty for novelty's sake, which is always a bad idea.
Quote from: Asteroza
For instance, is there enough bleed air from the SABRE compressor to run fluidics? On a more conventional rocket engine, would turbine exhaust work?
Unknown, and possible, if you can take the 3-5% of propellant diverted to the gas generator. SABRE, is more in the line of staged combustion engines, where everything that goes through the preburner ends up in the combustion chamber.
Quote from: Asteroza
Shades of the TAN augmented nozzle work in a sense?
Not really, that's way too far down stream.
Quote from: Asteroza
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?
Maybe. Estimates are that this angle was about 14Deg for SABRE 3 but SABRE IV has halved that to about 7 Deg.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #56 on: 12/31/2018 07:41 am »
HMX supplied a link to the Boeing study for a replacement Shuttle called RASV

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780022223.pdf
Written in the late 70's and assuming technology that would not be available until the late 80's in time for the start of the development programme for a Shuttle replacement by the mid 90's

It's a long read but has a number of nuggets for anyone planning a ground based HTO as written by a company that makes very large aircraft.

The preferred architecture (selected by the client, not Boeing) was a rocket powered wheeled sled to accelerate the SSTO vehicle (at 6 degs to the horizontal) to 220m/s (Skylon takeoff is designed for c180 m/s) before braking through a combination of drag brakes, drag 'chutes and plates pressing onto an unmodified (but long) runway surface

For example.
Running the engines with a zero Net Positive Suction Head LH2 pump reduced vehicle mass by 1588Kg and a 1psi NPSH LO2 pump reduced it by 902Kg, both mostly due to reduced tank mass needed to carry the additional pressure loads. The sensitivities on LO2 tank mass were 101.36 Kg/psi  and 259.59 Kg/psi for the LH2 tank.

Boeing seemed confident that they could carry LO2 in "wet wings" using pin joined spars linking the top and bottom surfaces

Landing gear is the big subsystem mass (3.3% of dry weight, although in a table it's 3.5% of landed weight) and they have some ideas of how to reduce it. Page 33 also gives the detailed landing gear requirements in FAR25, which Boeing planned to meet. Tire design is also considered for both the sled and the orbiter. Tyre cords were still Nylon, today AFAIK they are mostly Kevlar. Note OTS wheels should be good enough for an FTV, testing the viability of a larger tire on the ultimate vehicle would be much more involved.
Boeing did not consider water cooling for Rejected Take Off, and how it could radically lower the T/O mass.

The report also notes that while OMS/RCS individually are quite small, all together they come up more than the landing gear. Even then looking at ways to combine RCS and OMS functions using main propellants rather than hypergolics was being considered.

The report also notes that the APU's of the Shuttle are sized by the power needs of main engine TVC, whereas previous generation engines (F1, J2 and RL10) all had "Accessory drives" to drive hydraulic pumps, creating a more self-contained engine package. It noted that having the SSME's (actually upgraded versions of the Shuttle engines) pump their own hydraulic fluid means a)Much smaller APU, b) Much smaller APU MMH tank.
In terms of FTV/Skylon usage that might translate to eliminating a separate APU/Fuel cell power package and batteries being sufficient for aero surface control and systems power. Rather than gear down the turbine speed for a hydraulic pump (part of what made the Shuttle APU a PITA to service) a directly connected generator or alternator and some power electronics could drive a set of electromechanical actuators directly.

One quite unexpected feature. The nose wheel well is basically buried in the LH2 tank. While there is a a double walled and vented cable conduit run through the LH2 tank the designers don't seem to trust running any hydraulic lines through it. Instead they have a totally separate MMH powered APU driving a small hydraulic pump for braking and steering. Something you'd definitely want to avoid on a modern design.

Primary electrical power is 400Hz 120/220V from alternators as it notes that such systems are 10-30% the mass of DC systems. OTOH they would be more difficult for regenerative control, where you can recover most of the power you used moving something to a far point as it coasts back to its neutral position.

In other ways the report makes for quaint reading. Aircraft hydraulic systems were expected to hit 5000psi by the 80's, which didn't happen till the late 90's, by which time electric or electrohydraulic systems had also appeared. Likewise mounting 12 6 single DOF vibrating string gyros for the IMU in a dodecahedron arrangement (for redundancy), when SoA are ring laser gyros. Much lighter and much more compact.
« Last Edit: 01/02/2019 06:08 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #57 on: 08/31/2019 09:16 pm »
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.

Key goals are that the FTV should match the architecture of the proposed full scale vehicle. 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. No carrier aircraft.

It also notes that the design work for the FTV should be lead by an airframe mfg with experience of high speed flight. The implication is that would be BAe, but in principal it could be any of the partners in the Europfighter programme or Dassault, given the funding is from ESA. It's noted that it should not target applications. IOW it's an X plane to acquire and test capability ready for the full scale operational vehicle.

Matching the FTV to the projected architecture gives a strong template for what the FTV has to accomplish. 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.

On the ground you can replace the heat energy extracted from the air through the pre cooler by other means to drive the rest of the core but that's unlikely to be flight weight. You could run the the early flights without the inlet spike but that makes the pre-cooler very vulnerable to FOD. That would just leave the bypass burner (AKA "Spill ramjet") as a system that could be tested later.

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. That would give about 40 tonnes of thrust, giving roughly a 57 tonne GTOW.  A 20 tonne thrust engine is quite big by turbo fan standards. It's an RB211 or a GE CF6 size.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline speedevil

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #58 on: 08/31/2019 11:01 pm »
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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #59 on: 09/01/2019 08:38 am »
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.

Likewise aircraft certification is a Europe wide structure which I expect the UK will also continue to participate in.

I'm quite interested in wheather or not the FTV will incorporate the CNES ideas for leading edge root extensions and the "pen nib" shaped tail area to minimize the effects of plume heating, although if the expansion deflection nozzle works as expected that should be greatly reduced. 
« Last Edit: 09/06/2019 12:12 am by Lar »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #60 on: 09/02/2019 10:20 am »
Looking through the document I can see to requirements for the FTV to be the 'same architecture' as the final vehicle. 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.

Offline Barley

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #61 on: 09/02/2019 03:09 pm »

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.   

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #62 on: 09/02/2019 10:03 pm »
Sweden and Finland are in the EU.
Running on out of date data. My apologies
Quote from: Barley
Norway, Switzerland and Canada are not in the EU and are sufficient to support your point.
Thank you.  I think REL's joint project with CNES also helps.
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Offline Star One

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #63 on: 09/03/2019 12:43 pm »

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.

The U.K. government has long said that Brexit will have no impact on the country’s membership of ESA.

Offline edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #64 on: 09/04/2019 08:50 am »

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.

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. Any ERC funding and foreign workers may cause a varying degree of disruption to RE's day to day operations, but 'work for hire' like the HEX (DARPA contract) and proposed FTV (ESA) should survive.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #65 on: 09/05/2019 07:19 am »
To be frank: what the UK government says on Brexit does not necessarily have any particular correlation to reality.
Agreed, but not the time or the place for that conversation.  Things may become more problematical with the FTV depending on its details design.

Quote from: edzieba
The point is moot as indicated by Canada and Switzerland's memberships.
Exactly.
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Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #66 on: 09/08/2019 09:15 am »
Looking through the document I can see to requirements for the FTV to be the 'same architecture' as the final vehicle.

I'll quote the document.
Quote
the operational envelope of the FTV shall match, as closely as possible, that of the vehicle defined in work package 2.2

What is work package 2.2? 
Quote
Potential SABRE applications and their market impact
Which include
Quote
Top level system requirements that would be dimensioning for SABRE/Vehicle concepts, and taking into account target market segments identified in WP 2.1
IOW a space launch system, wheather that's called Skylon, Ariane 7 or "Avion Grand Vitesse" (to coin a phrase) is a question for another time.
Quote from: edzieba
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.
Most people would read
Quote
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
As an FTV sized specifically to support the ground test engine that REL are currently building.
That's when not if it's ready.

Since it is very unlikely such a space launch vehicle would be single engine that strongly suggests the FTV will be looking quite a lot like Skylon or the CNES concepts. WP 2.2 also explores the capabilities SABRE engines could give an RLV architecture (1 or 2 stage) that ELV's can't, like down mass, abort options etc.

It looks like the schedule is that FTV design and construction would begin just as the ground test programme is winding down and with enough time to incorporate lessons learned into the SABRE engines that would be carried by the FTV. An interesting question would be wheather it could run on straight rockets. Since it has to run LO2/LH2 logically that would be the OMS engines for Skylon, although wheather they could be developed within the budget for the FTV is another matter.
« Last Edit: 09/08/2019 09:21 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #67 on: 09/09/2019 04:16 pm »
Those conclusions seem to be contradicted by the document:
Quote
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.
Quote
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).
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
. 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #68 on: 09/10/2019 08:16 pm »
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.
Cost wise a single engine would be cheaper and that could get you above the AB/rocket transition stage but the implication is that the two work packages dovetail into each other.
Quote from: edzieba
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.
In fact the projected time frame fits very well with the results from demo-A being used to design and implement the fully integrated flight weigh engine (Demo-B?) for the FTV.
[EDIT I note that this is still potentially the first reusable hypersonic test vehicle since the X-15 more than half a century ago.  ]
« Last Edit: 09/23/2019 07:01 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #69 on: 10/14/2019 12:58 am »

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?
Maybe. Estimates are that this angle was about 14Deg for SABRE 3 but SABRE IV has halved that to about 7 Deg.
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

Doing a web search I found this item from the British space agency.
Why, so did I... :D

Quote
It's the planning for the flight test vehicle to test SABRE.

It's funding comes from  ESA

Are you sure it's from ESA, not from UKSA through ESA?
Quote
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.
And a market model demonstrating the financial value of such a full scale vehicle

Quote
Key goals are that the FTV should match the architecture of the proposed full scale
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
 
Quote
That strongly suggests a two engine FTV.
"[the] FTV flies with a SABRE air- breathing core engine" -- doesn't even use engine(s)

Quote
The request also requires the FTV should take off and land from a run way somewhere in Europe.
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?
Most disappointing in this document is it only requires flight up to Mach 5/25km, and only speaks of an air-breathing SABRE core - so no LOX requirement, no transition and climb.
Quote
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.
It says "It is expected that the vehicle shall test various subsystems of the SABRE engine including intake, pre-cooler and bypass burners"  but doesn't speak of "gradually building up"

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.

Quote
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
That's first flight of the FTV, Annex A says "the continued development of air-breathing SABRE core to a flyable configuration" and "the two development paths will eventually merge" (my emphasis) so I would argue the test engine will be the size deemed most suitable by the consortium (but the "new" smaller test engine size seems to be a reasonable size, so I'd be surprised if it were terribly different.)


 (Demo-B?)
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)
« Last Edit: 10/18/2019 05:54 pm by JCRM »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #70 on: 10/17/2019 06:47 am »
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
For 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. I'll certainly believe they have refined the design to reduce if not eliminate the bend. That would have been a good question for the talk as it was being given by one of the nacelle materials team.
Quote from: JCRM
Are 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: JCRM
And a market model demonstrating the financial value of such a full scale vehicle
That's the other work package. Skylon as a concept works best when there are multiple launch service providers but that's more for the main thread.

Quote from: JCRM
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
This point has been made earlier. 
Quote from: JCRM
Quote
That strongly suggests a two engine FTV.
"[the] FTV flies with a SABRE air- breathing core engine" -- doesn't even use engine(s)
That was excessive. On re-reading it does only cover the engine characteristics, not the vehicles.
Quote from: JCRM
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?
The carrier aircraft approach limits the vehicle size and hence its potential payload.  IIRC the Pegasus (the only LV currently available using this mode) has the dubious privilege of being the most expensive LV in the world in terms of $/Kg. It has benefits but unless you're going to custom build a very large carrier aircraft they are quite limited. You still have to build a TSTO vehicle in any event.

By ruling out such an approach you face the problems of reusability square on from day one with an approach that is known to scale up, with either one or two stages.  As for ground testing of course ground testing the transition would be possible if you have a LOX supply. Check the TF1 video. It has LH2, "inert gases" but no mention of LO2.  :(  AB/rocket transition is a major differentiator between SABRE and conventional rocket or gas turbine engines and hence one of the key high risk areas that would have to be proved to work without hitch before scaling up.

Quote from: JCRM
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.
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.

That sounds a lot more like the Skylon configuration than the X7 "flying stovepipe" you'd need for a single FTV. That would also mean a fairly large jet engine for the other nacelle, assuming the target for the FTV SABRE is also 20 000Kg of thrust. It would either need its own fuel tanks or be adapted to run whatever the FTV SABRE runs, either LH2 or possibly methane. We know REL adapted the viper turbojet to run on butane so methane should be fairly easy. Big turbjets were tested on H2 in the 70's by NASA and it's viable but note the very different mixture ratios have to be factored in, along with the higher temperatures involved.

The Orpheus engine for Concorde was tested in the bomb bay of a Vulcan. The Vulcan retained all its engines during the tests, despite Vulcans engines also being Orpheus's.

Quote from: JCRM
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)
"Test-A" sounds more likely.
« Last Edit: 10/19/2019 01:12 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #71 on: 10/18/2020 08:12 pm »
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 Engines
15           30.00%                  1                 44.15          9900   
15           50.00%                  1                 73.58          16500             BR700
15           70.00%                  1                 103.01         23100             V25000
25           30.00%                  2                 36.79          8250   
25           50.00%                  2                 61.31          13750              BR700
25           70.00%                  2                 85.84          19250              BR700


30% 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 42-500

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.

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.
« Last Edit: 10/18/2020 08:23 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #72 on: 12/02/2020 07:08 am »
The Reactions update given as the IAF Keynote speech had the following diagram regarding nacelle development. The word "integrated" comes up quite as does the idea that a lot of "coupled" interactions (thermoacoustic, aeroelastic etc) need to be studied. 

The joker in all this is to what extent the detailed internal structures affect the validity of the results if the nacelle is using a jet engine. Inlet flow should be fairly similar, as should driving the spike, but things will become more complex further downstream.

A more basic question would be wheather to have a single nacelle to hold either a jet engine or suitably sized SABRE or to have two separate units.

Separate nacelles add cost. OTOH the let you a) Work on both jet engine and SABRE nacelles simultaneously. b)Tailor the internals of each to hold the various components, including (if necessary) adding flow changing parts to make the jet engine flow model the actual flow in the SABRE nacelle better c) Allow the HTB to be developed at another site, provided the interface between nacelle and HTB (whatever design is chosen) is fully  defined.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline lkm

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #73 on: 12/11/2020 06:01 pm »
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 Engines
15           30.00%                  1                 44.15          9900   
15           50.00%                  1                 73.58          16500             BR700
15           70.00%                  1                 103.01         23100             V25000
25           30.00%                  2                 36.79          8250   
25           50.00%                  2                 61.31          13750              BR700
25           70.00%                  2                 85.84          19250              BR700


30% 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 42-500

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.

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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #74 on: 12/11/2020 07:01 pm »
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.
That is very neat  :). It ties up a bunch of REL's interests. REL has long been an expert to doing these sorts of deals where all the partners get something out of it. Nothing answers the question "Can you really put Ammonia in flight weight tanks and burn it in a (mostly) standard engine" like an actual flight test. In principle you can trade pressure for temperature IOW just chill it lose to its 195K melting point. If you're comfortable with LOX and LH2 ammonia is not too scary. It's toxic, but it's not WMD toxic like the hydrazines are.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline libra

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #75 on: 12/13/2020 06:53 am »
Where can i find that IAF paper please ?

Lkm: nice synthesis of many different REL projects, indeed.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #76 on: 12/15/2020 10:22 am »
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
For 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.
Yes, that's the vehicle design not the engine design.
Quote from: john smith 19
Quote from: JCRM
Are 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.
On an opt in basis. Do you know of any other countries contributing to this project. I wrote to my MP to ask, but didn't get a meaningful reply - haven't chased it because since then they've (hopefully) had more pressing things to deal with.

Quote from: john smith 19
Quote from: JCRM
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.
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.
uh, no. See attached for an example of a nacelle with a non-SABRE engine (perhaps you misread it as with no SABRE engine? or perhaps you though I meant all in one flight?).

Quote from: john smith 19
Quote from: JCRM
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)
"Test-A" sounds more likely.
Turns out it was Demo-A+
« Last Edit: 12/15/2020 10:39 am by JCRM »

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Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #78 on: 12/15/2020 06:37 pm »
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.
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.

Quote from: john smith
The challenge is that no suitable engine is going to run on methane or hydrogen so will have to be converted.
Why does the engine need to be converted?  "The first question you should be asking if you feel the urge to ask state one of those is why would the design go to <more complicated solution> (When a simpler solution exists)"
 
Quote from: john smith
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.

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.
« Last Edit: 12/15/2020 07:35 pm by JCRM »

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #79 on: 12/16/2020 07:58 am »
I'd guess PR changed the name to something more exciting, except this is Reaction Engines.
Indeed. Engagement with the general public is not their strong suite.  :(
Quote from: JCRM
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.
Exactly. Historically "hypersonic" has been a synonym for fast but the modern usage is >M5. Again historically air breathing engines have done M3+cruise and a few ramjets accelerated to M5. Above that it's been SCramjets that have got to their startup speeds on the top of a big rocket.
If you can pack a full SABRE cycle engine into a nacelle form factor (and make it run for a full burn to orbit, at least on a test bench) you've demonstrated you've got the design, mfg and packaging issues understood and under control.
However the air breathing/rocket  transition is probably the last big difference between SABRE and conventional rocket and air breathing systems.
IOW Just the sort of place that "unknown unknowns" lurk.  :(
Quote from: JCRM
Why does the engine need to be converted? 
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: JCRM
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.
Yes. Flexibility is going to be very important.

I expect 2 nacelle sets, one with jets for initial tests of the precooler/inlet spike and ramjets to burn the excess fuel from the precooler. While these are flying the first flight weight SABREs will be being built in the other setat  a pace that allows the flight test data to be incorporated into them.

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, although I'm sure there will be a lot of simulations on this before they start construction (many coming from the DEMO-A results). That assumes it will be able to glide back to its home runway afterward.

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. They always had more sensor points than they could record, so they had patch panels which were re-configured each flight depending on the specific goals. Knowing what channel was recording what parameter on what flight would be a critical set of information to record and monitor for after flight data analysis.
The paper makes the point that the instrumentation should be ready and bedded down before the flight test programme begins. Some of theirs wasn't (100KHz tape recorders to capture turbulence noise) or marginal (the analog inertial position system was about up to spec but a maintenance nightmare until they replaced it with a digital system, but only after the core programme of tests was complete in 1963).

My instinct is air data will be difficult. The SoA is a "Flush Air Data System" (or "Computed" ADS as Boeing call it on the X-37b) of multiple pipes in the nose.
But that will depend on how much experience BAE (or whoever builds the HTB) has with the technology. For this application I believe better options are possible, but I'm not sure they are available. FADS (or whatever it's called) will be the baseline. :(

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 cost effective when this starts flying) so some kind of selection process (and tracking of channel assignments, which might also change throughout the flight) will still be needed.

One other point the X-15 reports made was never run the next flight (even if you could) during an existing flight until they fully understood the results of the current one. And that was a programme that had 3 flight vehicles to choose from. I doubt REL will have that luxury.  :(
« Last Edit: 12/16/2020 08:22 am by john smith 19 »
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Offline 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 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #100 on: 08/09/2022 11:24 am »
Quote from: Reaction Engines
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

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #101 on: 08/09/2022 01:29 pm »
So HVX may be a precursor to HTB

I don't think the MoD would like to think of it in quite those terms.  ;)

But once you're above M5, however you get there, if you want to stay there for any significant length of time (Which I'd say >10 secs)  you're going to have to address certain common issues, but technology that didn't exist when the X-15 and SR71 were in development have opened up all sorts of options.
Some stuff could be tested at any scale, merely to move the TRL level from the work bench/test rig --> actually flown. IMHO a key high level design choice is Hydraulic Vs electric. The Shuttle OMS and Pegasus and Vega TVC's were or are all electric, so it's certainly in the running, provided battery capacity (or onboard generation, which is SOP for non-expendable aircraft or drones) at these temperatures (and the X-15 had on board electricity generation through its APU's) is up to the job.

I'm thinking a mix of "flight stuff" like high temperature temperature/pressure/mass flow sensors along with "design" or operational stuff, like water cooled brakes, and consumables loading through wheel wells to reduce the number of lower surface openings. Fibre optics open up a world of options (up to about 400c, or you can go to Sapphire, but only in about 1.5m lengths, which suggests it will be very expensive).
I think some amazing stuff could be done with Low Temperature Cofired Ceramics. It's a very flexible technology and big in Poland and Czech Republic but less so in the UK. Los Alamos NL have done remarkable things with it.

Likewise sound and air pressure, transmitted down tubes <1.5mm dia, have been use as temperature and strain gauges, the former developed by the Dragon reactor project to measure to 1500c, within 1%, but requiring a complex manual procedure (although I'd guess with modern processors or their specialist support chips "too complex to automate" would have to be very complex indeed). One was develped for NASA using Molydenum wire a couple of mm thick, but it was only accurate to 50c.

What I liked about the X-15 programme was that after the core tests were carried out (by 1963 apparently) it had enough flexibility (and enough interest in the experimental community) to run all sorts of tests. A modern update could do so also provided a degree of flexibility was designed in from the outset. [Edit should be collected to meet REL goals, and what hooks would make the design more versatile to 3rd parties, are core subjects for this thread]

« Last Edit: 08/12/2022 11:36 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #102 on: 08/16/2022 06:30 am »
While I was offline I was thinking about the actual process for the HTB.

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.

For example while in theory micro USD' can handle writes at 300MB/S, AFAIK the highest available data rate is actually 90MB/S. No doubt it will get better  before the vehicle flies, but that should be tracked.

Likewise formats can cause issues. Consider air pressure. SL air pressure standard is 101326Pa, or 1 Bar or 1000 millibars (or worst case, a voltage reading taken from a sensor). The first gives maximum accuracy, at a cost of 2 and 1/8 bytes each. Maybe that's what is necessary to deliver useful data for the test team. It would be the FDC's job to track these needs, see what's necessary and negotiate with other teams if more is needed.

Sometimes the data might need to be pre-procesed onboard. Taking blocks of readings to create a "Signature" reading. But how? Averages are easy if the block size is a power of 2 and the register widths are big enough. But the peak value (or peak and trough values) might be more useful.

I see this all being kept in a document that can then be post-processed to generate the configuration inforamtion for the on-board data system. During design it  tracks who's collecting what data, at what data rate and (just as important) what's the reamining bandwidth available in case something unexpected comes up.

BTW given the potential data collection WiFi is not really fast enough to transmit the data in reasonable time, so another task would be to identify "Quick look" data to be downloaded (by whatever means) as a priority.

I'll be interested to see how REL does this, and what form the "Document" actually takes. It could range from a text document with multiple post-processors (flexible if you have the text mashing skills) to an actual database with formal structure, access control etc.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #103 on: 08/16/2022 12:11 pm »
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.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #104 on: 08/17/2022 07:00 am »
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.
Actually I expect it to be a role someone in the team building or specing the DAQ system.

IRL the data sampling stuff is the easy bit, it's the actual sensors they are reading that are likley to taking up most of the space, mass and power.

Those used in consumer devices can be very small MEMS, but they are only an option if they can deliver the parameter range being measured. If not you are going to need something more "industrial" built with more conventional methods, and hence likely substantially bulkier.

My point was that such decisions are not quite as simple as people might think and poor choices can swallow
large chunks of storage and bandwidth. If you went with reading atmospheric pressure in Pa a straight conversion would be to a 17bit number. Storage is byte addressible so that's going to need 3 bytes with 7 unused bits. What do you do with those 7 unused bits?

The simple answer is just to leave them empty. That's about 29% of the storage, but that's only channel.  The problem is that it won't just be one channel that's being sampled. The X-15 had about 1100 channels of data (and it's fairly obvious they would have liked more in some areas). At 90MBS that's about 81KB/sec per channel. Again you can bite the bullet and just leave that storage empty or use it for something else.  That's where you need someone to keep track of what's wanted, what's needed in what format, etc.

The classic example for why someone doing this is needed would be the Shuttle Body Flap, which was subjected to (IIRC) substantially higher heating than predicted and they needed the hinge angle to drive 2 competing models of the behaviour. However this data was only available at 1 reading/sec, meaning that by the next actual reading was available conditions had changed a lot.

Obviously HTB is probably not going to have a body flap, but the possibility for the same kind of problem to appear exists. AIUI this was an issue due to the limitations of the Shuttles onboard telementry recording system. But as I've noted it would be possible to swamp the available bandwidth and storage with some poorly planned choices. If something then appears in testing and the whole bandwidth is committed you then have to ditch some channels to make room to measure that phenomena instead. Having someone tracking usage, needs and possible contingencies seems a very good idea to me.
« Last Edit: 08/19/2022 05:30 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline edzieba

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #105 on: 08/17/2022 10:45 am »
Again, that's really not a problem that needs to be re-solved. If the required bandwidth is more than one DAQ can handle, use a second one, syncing timestamping is a standard function. 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.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #106 on: 08/19/2022 05:55 am »
Quote from: edzieba
Industrial sensors are not always big chunky things (e.g. remote fibre sensing; which includes strain sensing, chemical detection, pressure sensing, etc).
As I noted if the demand for a)That specific set of parameters and b)That dynamic range already exists. Otherwise they will have to deal with the OTS sensors that are available, unless they develop their own. I personally think LCC has a lot of potential in this area. It's a relatively cheap technology to set up and has a lot of flexibility. It's raw operating temperature is also comfortably 100s of Co above semiconductors on PCBs

Quote from: edzieba
The STS MMUs for first flight were magnetic tape based. That capacity and bandwidth limitation is not present today.
They were. But while the size of the limits on storage and bandwidth have greatly increased the limits still exist. Society is full of examples (especially in the environment) where certain resources were thought of as "infinite" when  in fact they are not. We are now living through some of the consequences of that mindset.  :(

A classic one in the IT field was described in "Programming Pearls" where the advent of virtual memory lead to people designing software using very large arrays. For small applications there was no problem as the whole array was in memory. Once the problems got bigger the system started swapping chunks out. Work was now done in bursts with long chunks inbetween when the next section of array was swapped in.

This should have been obvious in hindsight. More subtle was that some array address patterns (the "stride" between the cells being accessed) got a lot more work done in the same amount of clock time.

Tracking who needs what, who wants what and how much of a resource is left lets you make rational decisions on what to use that resource for, and to keep some in reserve in case "unknown unknowns" have to be investigated.

It's also a fact that those parameters won't exist in a vacuum. Associated with each of them wil be a slew of information about system setup and how to extract and process it.  In the third decade of the 21st century no one should be doing that by hand anymore.

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. I'm sure we'll find out how REL dealt with the matter in due course.
« Last Edit: 08/19/2022 06:00 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #107 on: 08/19/2022 10:50 am »
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.
No more so than they will already be doing for their many existing test stands.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #108 on: 08/24/2022 06:47 am »
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.
« Last Edit: 08/24/2022 06:49 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline TrevorMonty

Re: Reaction engines Flight Test Vehicle speculation
« Reply #109 on: 08/24/2022 06:25 pm »
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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #110 on: 08/25/2022 07:25 am »
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.
As I noted it's no longer called "Hyper A" but Talon. Hadley appears to be  ORSC Kerolox, but that doesn't change the elements of the paper that I quoted.

And in this context they believe there is a market for 3rd party organisations who would like to use such a facility, which is the idea behind this thread as well.
« Last Edit: 08/26/2022 06:37 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #111 on: 09/06/2022 11:49 am »
No more so than they will already be doing for their many existing test stands.
What test stands?

There's TF2.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #112 on: 09/06/2022 02:34 pm »
No 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.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #113 on: 09/07/2022 02:02 am »
No 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, Bristol
STERN, STRICT, STOIC, pre-burner injector, HX3: Airborne engineering, at Westcott
Pre-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 facility

My 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.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #114 on: 09/07/2022 07:42 am »
HTX: RE Inc, Colorado.
Precooler test stand, Reaction Engines Ltd, Culham, *
Cold E/D: Bristol University, Bristol
STERN, STRICT, STOIC, pre-burner injector, HX3: Airborne engineering, at Westcott
Pre-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 facility

My 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.
Wellll my original point was in the context of the thread title (or HTB as we should now call it) and the data that it needs to collect (and what others would like it to collect) but  :) in fact listing the possible sites that could be involved makes it even more important.

IMHO the worst case scenario would be a partner organisation (such as a post grad at Bristol) doing their project (with Reaction support in some form) but the test parameters are just a bit off and it's too expensive to re-run. IOW the whole dataset is wasted.  :(

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.

What those needs might be, and how to ensure they are factored in, are definitely on topic for this thread.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline JCRM

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #115 on: 09/07/2022 09:54 am »


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.


... and as a product, if something like the now defunct Orbex Orbital Access is started.
« Last Edit: 09/08/2022 09:27 am by JCRM »

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #117 on: 09/08/2022 07:16 am »


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.


... 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).
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #118 on: 09/08/2022 08:40 am »


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.


... 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).
With the cost of any additional refinement/purification, if you have already decided to go for a Syntin-like synthesised propellant, deriving it from renewable feedstocks is not a significant cost increase so an easy ecological win.

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Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #120 on: 09/08/2022 09:43 am »
A Brain Fart. I meant Orbital Access
They barely lasted six years before being dissolved in Feb '21.

I think people seriously underestimate how tough even survival, let alone growth, in this business actually is.  A check on how many companies and projects in the space sector are still around from 1989 is likely to make pretty depressing reading.  :(
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #121 on: 09/08/2022 01:16 pm »


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).
« Last Edit: 09/08/2022 01:22 pm by Jim »

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #122 on: 09/09/2022 07:48 am »

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).
An interesting PoV. So are you saying the mass of individual sensors need to be reduced?
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #123 on: 09/09/2022 01:45 pm »

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).
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

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #124 on: 09/29/2022 12:26 pm »
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
My point wasn't about managing the data. It was about choosing what data is being collected. It's more about the meta data.

But as long as having someone deal with this is already a recognized function then there shouldn't be a problem.  :)
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #125 on: 09/29/2022 12:32 pm »
I found this item https://www.forbes.com/sites/erictegler/2021/08/18/the-air-forces-investment-in-hypersonic-startup-hermeus-isnt-about-producing-a-hypersonic-presidential-executive-transport/?sh=6e2917cb3e26 regarding Hermeus. This further confirms there are people interested in a re-usable M5 test vehicle.

In this case it's the USAF, looking to test ISR, C&C and video systems at hypersonic speeds. Also the ability to calibrate their wargames in terms of operational and tactical concepts.

Such capabilities would probably be of interest to any developed nation with a substantial airforce that might have to face nation level threats of similar development.
« Last Edit: 09/29/2022 12:33 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #126 on: 01/11/2023 06:33 pm »
Doncaster-Sheffield airport recently closed. The airport had  the 11th longest runway in the UK and although only offering commercial flights since 2005 had been a military airbase from 1915.

So the locals are used to the sound of very large aircraft taking off from its (untill recently) regularly maintained 2893m/991 ft runway. It also has hangar facilities.

Obviously with the airport being closed support services are likely to be non-existent somewhat spartan but there will be no queues for takeoff.

I'm not suggesting REL would buy an airport but some arrangements could be made that would allow them to use it and put some funds into the local economy.
« Last Edit: 01/11/2023 06:34 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #127 on: 01/18/2023 11:28 am »
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

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #128 on: 01/21/2023 03:32 pm »
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
An excellent find  :) Absolutely on-topic for this thread. I especially like their point about tracking uncertainty in the parameters.

One of the most insidious issues of high mach design is that the reliability of the values you have calculated drops as the speed goes up. It only takes a little increase in Cd (or a corrosponding fall in predicted CL) to make the design unworkable  :(

It also looks like this predates the recent paper that announced which version of the HTB Reaction are planning to build. Sadly still no sign of that paper in the wild.  :(

That said the Stratofly design looks sort of familliar.
« Last Edit: 01/21/2023 03:33 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #129 on: 01/21/2023 11:10 pm »
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?

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #130 on: 01/23/2023 04:35 pm »
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?
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?
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #131 on: 01/23/2023 09:45 pm »
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?
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?


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.

The Synergetic Air-Breathing Rocket Engine SABRE - Development Status Update-IAC-20,C4,7,1,x60592:
Quote
Although the primary purpose of the HTB is for
nacelle technology development, an extension to the
HTB programme may provide potential opportunities to
support some aspects of both the air-breathing core and
rocket engine development programmes. For example,
having developed a flight test platform that is capable of
high Mach/Altitude flight, it may be possible to use this
capability for in-flight testing of nozzle aerodynamics
and air breathing/rocket transition and as previously
discussed the platform could also be used for in-flight
demonstration of SABRE by substituting the
experimental nacelle COTS gas turbine with a flight
integrated version of the DEMO-A+ core. Furthermore,
the HTB may potentially also be used to develop many
of the future launch vehicle airframe technologies (e.g.
materials, structures, re-entry) in advance of a full-scale
prototype SABRE launch vehicle.

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #132 on: 01/27/2023 05:10 pm »

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.
With the implied assumption that Reaction is capable enough to engineering a complex combustion system but not of analysing a truss frame structure. IIRC the classic example of such a design was built by JPL. I think it was something like 4Kg but supported a mass of 89Kg. [EDIT or the 1987 Sunraycer solar car. As described by Paul McCready of Aeroenvironment  Gross weight 260Kg. Frame mas 7Kg. That's 37.14:1. That's straight out of an article on the Sunraycer Wiki page. Perhaps they just lack the skills to do the analysis to confirm it's possbile ? ]
Quote from: lkm
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.
Agreed.

The question with the HTB is "If you don't use Skylon construction methods how do you build it?"

if we assume that DEMO A will be sized for the first prototype SABRE that gives  you a vehicle the mass of a heavy fighter or a light regional airliner. with a T/O thrust of about 40tonnes with twin SABRE's. That give a GTOW which depends on wheather you believe thrust needs to be 70% of GTOW (IE SAIC studies go-to figure) or 30% (which was enough for both Concorde and IIRC the XB70). That means 57-133tonnes for a 2 engine HTB.

That could be used in various ways.

The key thing to bear in mind is HTB is a technology demonstrator not a prototype Skylon.  Its (initial) mission is allowing the parts of SABRE that are incapable of being ground tested (or at least incapable-at-any-reasonable-cost) to be tested and Reactions various design programs to be tested and calibrated.

So Reaction has to walk a fairly fine line. Obvioulsy the more they can test at this scale the less they will have to worry about at full scale. That implies a "robust" IE heavy structure with a high probablity of success.  OTOH there are not really that many ways to build a vehicle for M5+. The X15 was specifically designed to cruise long enough for the whole airframe to get hot to study what happens when an airframe gets that hot (the UK equivalent for the Concorde programme was the Armstrong 188 which apparently ran out of fuel before that happened, so was not very helpful. Just too heavey unfortunately :(  )

The D21 reconnaisance drone was Titanium and NASA made attempts to re-purpose some with the DRACO engine to get to M6 but that was highly questionable. Maybe Titanium designed from scratch for M6 speed?

What has changed a lot is the shear ability to track every part of a design through the CAD system and in turn update the materials properties.

 Build say a batch of hair pin rivets and weigh them.  Test them to destruction. Now you have actual values for average mass and strength (as well as max/min) and the nominal placeholder numbers are updated, feeding into everything from dry mass to probable moment forces on structures.

So the challenge will be to design an HTB that tests everything about SABRE it has to test, as well being able to have various stuff unbolted and be replaced by more risky versions of such systems, like the brakes, once the core testing is out of the way.

What sort of things it should test (related to Skylon/A7/Avion Grand Vitesse/Whatever) and what sort of things it could test for 3rd parties, are very much on-topic for this thread
« Last Edit: 02/06/2023 05:37 pm 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #133 on: 01/28/2023 06:18 pm »
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.
Especially if it did so at a scaled mass of what a full size Skylon did IE that it demonstrated truss-structure internals/corrugated skin could achieve the a structural fraction that Reaction claim.

That's not necessary for it's engine mission, but doing so would make a huge existence proof that what they are claiming is possible can be made to work.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Re: Reaction engines Flight Test Vehicle speculation
« Reply #134 on: 04/08/2023 07:17 am »
Sometimes something happens that can force a complete change of outlook.

In the early 20's Ludwig Pradtl published a paper on the most efficient lift along a wing. It was an ellipse. This was heavily read and followed up.

But in the early 30's pradtl issued another paper which revised his conclusions and the actual shape was a bell.

It's unclear how familar aircraft designers are with this papers conclusions, either in Europe or the US. Apparently not very.

NASA's study of the paper, and some of its implications are here

In particular it explains how it's possible for birds to manoeuvre without a vertical tail and why flocking helps. It also has implications for loads at the wing root. It's 22% longer but has 11% more lift.

This work was followed by the actual design of aircraft using the theory through an inverse method, rather than the conventional design-the-aircraft-first-and-find-out-its-airflow-later approach.

Pradtl's work uses spar mass as a constraint so this is quite relevant when  moving to higher performance aircraft. The joker is how this changes as you go through M1

« Last Edit: 04/08/2023 11:13 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 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

 

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