The Reaction Engines Skylon Master Thread (5)

[Star One]

It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.

How could one turn up one's nose at a chance to try out some aspects of Skylon/Sabre without needing to go directly to a $10 billion SSTO?  It could be a godsend.

That might control what aspects the engine demonstrator has to be most realistic about, how much money has to be spent on it and where.

That's my view why turn down money to develop technology that may eventually help you achieve your commercial aims.

My only fear is the USAF 'locking up' some vital technology for their use only.

[Citizen Wolf]

Star One
**My only fear is the USAF 'locking up' some vital technology for their use only.**

That's what I was thinking also. Comments from AFRL suggest that they don't think SSTO is a good or viable option. But they do seem to think that the SABRE technology is useful for them in some other way. They could then have further arrangements with REL to develop certain aspects of the SABRE technology to implement their goals (not SSTO). These technology improvements would become tied up in military/national security concerns and SSTO/Skylon won't happen. At least certainly not in the timeframe as currently envisioned by REL. 

[flymetothemoon]

At least certainly not in the timeframe as currently envisioned by REL.

Yes. It's the timeframe I find bothersome after waiting (in mine and many people's case) more than 30 years since I was a boy to see Mr Bond's baby fly.

Still if a really good working demonstrator comes out of it, then the belief should be there and it might be full steam ahead for applications after that which wouldn't be so bad. Quite frankly I also want Alan Bond to see his Dan Dare inspired boyhood dreams realised - and superb engineering vindicated - before it's too late!

[Hankelow8]

Star One
**My only fear is the USAF 'locking up' some vital technology for their use only.**

That's what I was thinking also. Comments from AFRL suggest that they don't think SSTO is a good or viable option. But they do seem to think that the SABRE technology is useful for them in some other way. They could then have further arrangements with REL to develop certain aspects of the SABRE technology to implement their goals (not SSTO). These technology improvements would become tied up in military/national security concerns and SSTO/Skylon won't happen. At least certainly not in the timeframe as currently envisioned by REL.

Worrying this, I do hope they have enough experience  dealing with any contracts that AFRL might throw at them that does not tie their hands for future UK development.

But one has to realise they are a business with financial backers that expect a return on their investment.

[Paul451]

It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.

My only fear is the USAF 'locking up' some vital technology for their use only.

Bond & Co have been down that path before, with their own HOTOL work being locked behind (ultimately pointless) restrictions. I doubt they will go down the same path unless they have an "out" that allows them to continue REL/Skylon when the USAF program is inevitably cancelled.

[Star One]

It seems to me that there could be a chance for REL to develop something which would not be economically worthwhile  if done by themselves but might be militarily worthwhile to the USAF.

My only fear is the USAF 'locking up' some vital technology for their use only.

Bond & Co have been down that path before, with their own HOTOL work being locked behind (ultimately pointless) restrictions. I doubt they will go down the same path unless they have an "out" that allows them to continue REL/Skylon when the USAF program is inevitably cancelled.

I wouldn't assume on it being cancelled considering the current political situation.

[banjo]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

[Star One]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.

[Citizen Wolf]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are). 

[ClaytonBirchenough]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?

[meiza]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.
I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.

Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.

[Star One]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment. Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

SR-72?

I wonder if the NASA study into its proposed engines has finished yet.

[john smith 19]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

SABRE was designed from day one to eliminate SCRamjets because in the late 70's and early 80's it was basically a fantasy technology.

And despite the billions of dollars the USG has pumped into the technology it still is. 

I wouldn't assume on it being cancelled considering the current political situation.

Meaning what exactly?

Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.

And where SCRamjets are concerned there is so much chaff to begin with. 

It took a lot of reading to find that an SCRamjet has a listed T/W of 2. The turbojet on the SR71 has a T/W of about 5.3. It's estimated the nacelle halved that to about 2.6.

So after 55 years an SCRamjet may deliver  an T/W almost as good as the SR71 package did in the early 60s.

Once you know that it's no wonder they are having trouble launching even a missile based on this technology.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment.

And yet no one thinks this is quite a big clue that SCRamjets are not a very good design idea. 
Every SCRamjet test vehicle has started strapped to a rocket and the rocket has normally got it to starting speed with few hitches.

Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

They are but this needs LH2 and armed forces are very wary of cryogenics.
One of the reasons for ending the SR71 is they did not like maintaining the supply chain (a global network of dedicated ground tanks and tanker aircraft) for the JP7 fuel

Not cryogenic. Not toxic. Just not JP4.
LH2 is a much more serious commitment for a unit of reconnaissance aircraft. OTOH as a launcher you could base it at one of the old B36 rated runways, of which the USAF has 3. You'd take a payload hit but you can launch from CONUS and be back at base within a day. Kind of like an orbital B2.

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.

A modern turbofan delivers a T/W of 10:1. SABRE's design goal is 14:1. IE about 40% better than a SoA jet engine. That's poor by rocket standards but an Isp 6x or 8x better than the best rocket engine (while air breathing, otherwise it's mere as good as the best Isp of known rocket engines) makes a big difference in building an LV.

I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.

Not really.
Firstlyif you've got air breathing your Isp goes up a lot compared to rockets and you can use wings. SABRESkylon is designed to use both. 

Secondly launch puts the airframe at maximum temperature for a very limited period of time. 10s of secs at maximum AB Mach before it goes to full rocket mode and a few 10s of minutes on re entry at most.

Cruise is like re-entry but lasting for hours requiring continual dumping of enormous quantities of heat from the whole airframe. That lets you use design approaches that won't work for long periods but are perfectly acceptable for the launch/reentry mission.

If you don't understand that difference you need to study a bit more engineering.

BTW HTOL takes a thrust roughly 1/3 (or in extreme cases 1/4) the GTOW. OTOH if you go with VTOL the thrust must exceed the weight by a significant amount or there is no take off at all.

Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.

There have been many designs put up by SCRamjet proponents over the years. Various proposals attracted substantial funding. X30 got $Bn+.

All had (in hindsight) low TRL's so IRL it was going to be a case of build the vehicle to test the engine. Which, giving the high levels of uncertainty about M5 combustion and flight meant the probable result was that you'd throw the aircraft away and have to start again.
None have built an actual flight vehicle.

SABRESkylon is designed to avoid as much uncertainty as possible. The engine was designed (from day one) to be tested on the ground, so when you design the vehicle you already know it's going to work. The question then becomes how well can you design the vehicle to deliver that potential.

[banjo]

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed. 

[Star One]

Maybe the AFRL have in mind a hypersonic aircraft sporting heat exchangers, carrying a scramjet vehicle to start up speed.

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

SABRE was designed from day one to eliminate SCRamjets because in the late 70's and early 80's it was basically a fantasy technology.

And despite the billions of dollars the USG has pumped into the technology it still is. 

I wouldn't assume on it being cancelled considering the current political situation.

Meaning what exactly?

Who knows there's a lot of rumours doing the rounds these days concerning hypersonic vehicles. The internet is so full of nonsense on the topic thanks to urban legends like Aurora that it is very difficult to sort fact from chaff.

And where SCRamjets are concerned there is so much chaff to begin with. 

It took a lot of reading to find that an SCRamjet has a listed T/W of 2. The turbojet on the SR71 has a T/W of about 5.3. It's estimated the nacelle halved that to about 2.6.

So after 55 years an SCRamjet may deliver  an T/W almost as good as the SR71 package did in the early 60s.

Once you know that it's no wonder they are having trouble launching even a missile based on this technology.

At the moment scramjets have yet to prove their practical worth and overcome technical difficulties. Considering that, I would have thought that the easiest and cheapest way to get scramjets up to speed is with rockets, as they're doing at the moment.

And yet no one thinks this is quite a big clue that SCRamjets are not a very good design idea. 
Every SCRamjet test vehicle has started strapped to a rocket and the rocket has normally got it to starting speed with few hitches.

Looking into using SABRE engines to power-up scramjet craft would be a long way down the road (but I guess they could still be considering it).

Putting aside high Mach (6+) capable craft aside, I would have thought that AFRL/USAF would still be interested in a craft that can go from 0-Mach 5 (depending on what the particular goals are).

They are but this needs LH2 and armed forces are very wary of cryogenics.
One of the reasons for ending the SR71 is they did not like maintaining the supply chain (a global network of dedicated ground tanks and tanker aircraft) for the JP7 fuel

Not cryogenic. Not toxic. Just not JP4.
LH2 is a much more serious commitment for a unit of reconnaissance aircraft. OTOH as a launcher you could base it at one of the old B36 rated runways, of which the USAF has 3. You'd take a payload hit but you can launch from CONUS and be back at base within a day. Kind of like an orbital B2.

Air breathing has more benefits as a cruise technology compared to rockets. Air breathing is speed limited and the engines are heavy. So it makes more sense as a reconnaissance aircraft as a space launcher at first cut.

A modern turbofan delivers a T/W of 10:1. SABRE's design goal is 14:1. IE about 40% better than a SoA jet engine. That's poor by rocket standards but an Isp 6x or 8x better than the best rocket engine (while air breathing, otherwise it's mere as good as the best Isp of known rocket engines) makes a big difference in building an LV.

I hope something comes of this. It's easier to make the technology work if you don't have to take the huge engines, wings, landing gear etc to orbit.

Not really.
Firstlyif you've got air breathing your Isp goes up a lot compared to rockets and you can use wings. SABRESkylon is designed to use both. 

Secondly launch puts the airframe at maximum temperature for a very limited period of time. 10s of secs at maximum AB Mach before it goes to full rocket mode and a few 10s of minutes on re entry at most.

Cruise is like re-entry but lasting for hours requiring continual dumping of enormous quantities of heat from the whole airframe. That lets you use design approaches that won't work for long periods but are perfectly acceptable for the launch/reentry mission.

If you don't understand that difference you need to study a bit more engineering.

BTW HTOL takes a thrust roughly 1/3 (or in extreme cases 1/4) the GTOW. OTOH if you go with VTOL the thrust must exceed the weight by a significant amount or there is no take off at all.

Mach 6 methane fuelled craft have been studied decades ago, attached a picture from the Secret Projects website.

There have been many designs put up by SCRamjet proponents over the years. Various proposals attracted substantial funding. X30 got $Bn+.

All had (in hindsight) low TRL's so IRL it was going to be a case of build the vehicle to test the engine. Which, giving the high levels of uncertainty about M5 combustion and flight meant the probable result was that you'd throw the aircraft away and have to start again.
None have built an actual flight vehicle.

SABRESkylon is designed to avoid as much uncertainty as possible. The engine was designed (from day one) to be tested on the ground, so when you design the vehicle you already know it's going to work. The question then becomes how well can you design the vehicle to deliver that potential.

I was referring to China's hypersonic weapons development program & the U.S. response to it.

[TrevorMonty]

I'm confident you're reading too much into this. It would be a different matter if Alan Bond said "we're switching to TSTO" publicly, but here you have their Director of Corporate Development sound just exactly like someone in that role should: he's being broadly supportive of the AFRL statement - i.e. their recent partner who they may hope to work with again (read $$$$ that could help further the Skylon project).

How would we know there not still actively working with the USAF, it may not be something the USAF wish broadcasting.

I personally feel if the USAF want a hypersonic vehicle of some type then REL are their best best to achieve this.

According to their press release regarding the results of the CRADA it is an ongoing relationship as it states :

"Reaction Engines Ltd. and AFRL are now formulating plans for continued collaboration on the SABRE engine; the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system, testing of SABRE engine components and exploration of defence applications for Reaction Engines’ heat exchanger technologies."

Note it states "SABRE derived" regarding what they want to put in a vehicle.

The heat exchanger technology has a lot of ground based and probably marine applications. REL are expecting to make a lot of money from this technology alone.

[t43562]

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed.

I have wondered if a hypersonic vehicle that could go nearly as fast as a scramjet would make a useful test bed.  At the moment the engine+vehicle is lost after use and that has to be quite expensive.   lets say a sabre(lite)-based vehicle can only go up to M5 - perhaps it is still useful to be able to test a scramjet in real flight conditions at that speed.   You can do your test flight, recover the engine, look at what might be wrong with it and then go out and do the test again.

[john smith 19]

You do realize that the idea behind a SCRamjet is to use the heat generated by the air flow at M5 to burn a fuel. REL heat exchangers remove that heat and power a normal engine cycle with it.

yes, i was thinking of a hypersonic white knight two type carrier aircraft that released a scramjet vehicle once up to speed.

Only if  you're looking for funds for a SCRamjet research programme. 

If you want an M5 cruise engine REL did the conceptual work for this under the EU LAPCAT programme.

The simple fact is that REL's work eliminates the need for a SCRamjet in the first place.

Do you want a vehicle that can run at M5 or do you want a SCRamjet research programme?

REL could provide the engine for the former, but have no interest in the latter. 

I was referring to China's hypersonic weapons development program & the U.S. response to it.

The thing that needs an ICBM to get it up to speed and then glides to target?

Like the Bell BOMI concepts of the 1950s?

Or the "Evader" MIRV tests of the 1970's & 80's? Which (had they been deployed) would have been nuclear armed by default.

AFAIK the only people "worried" about this are people whose presentation ends "And that's why we need an X $Bn hypersonics research programme to investigate what we can do about it."

On a personal note you should take a look at how this site quotes stuff. Most of what  you quoted in my post was not needed. 

I have wondered if a hypersonic vehicle that could go nearly as fast as a scramjet would make a useful test bed.  At the moment the engine+vehicle is lost after use and that has to be quite expensive.   lets say a sabre(lite)-based vehicle can only go up to M5 - perhaps it is still useful to be able to test a scramjet in real flight conditions at that speed.   You can do your test flight, recover the engine, look at what might be wrong with it and then go out and do the test again.

Alternatively use the SABRE derived vehicle instead of the SCRamjet?

This is the problem for REL and the USAF.

HX technology does not help you make a working SCRamjet, which is the dream the vast majority of us researchers have been pursuing.

It eliminates the need for such an engine at all, if you can live with running on LH2.

OTOH the LAPCAT study noted that a design could support a 20 000 Km range without aerial refueling, so (in principal) eliminating the need for the fueling infrastructure that was a big part of SR71 operations.

REL engine concepts don't work if you
a) Can't accept LH2 as the fuel, because  you just don't like it.  b) Need a very long range in a small form factor.

Outside of this their engine concepts can deliver long range and high speed, potentially from bases solely inside CONUS.

That really just leaves long range missiles, not as a test bed but as the sole use for a SCRamjet running on something other than LH2, provided the spec needs a range that far exceeds a pure rocket and the speed exceeds what a subsonic combustion ramjet can do (except that in the 1960's the French built ramjets that did hit M5 and some US test missiles went that fast due to stuck fuel valves).

You'd have to write a very carefully worded missile procurement spec so that the prime candidate for propulsion was an SCRamjet. 

US Hypersonics researchers have proved remarkably adept at getting the US Govt to spend several $Bn over the decades with remarkably little to show for it. 

[banjo]

john i meant only exactly what i wrote.  "maybe the AFRL have in mind......"   

[john smith 19]

john i meant only exactly what i wrote.  "maybe the AFRL have in mind......"

Then  I would say it's a pretty doubtful notion, given the history of SCRamjet development. 

The question again is why?

The rule of thumb (not sure if anyone's tried it with SCRamjets) is ramjets can have a 3 Mach operating range so maybe you can get a vehicle to M8?
Or perhaps you don't like LH2 for a cruise vehicle. Unless you run on straight JP4 you're back to the separate fuel supply chain the SR71 had which was one of the reasons the USAF gave for retiring it in the first place. 

People may think a non LH2 fueled vehicle will be "stealthier" as it will be smaller but most of the features of low radar cross section that worked on an SR71 would scale up quite well.

But whatever the size of such a vehicle it will always be a huge target on any kind of infra red sensor.   

Someone sees a  UFO on IR traveling at M5 on a straight and level course at  FL800. They are not thinking "meteorite."