USAF/US NAVY 6th Generation Fighter Programs - F/A-XX, F-X, NGAD, PCA, ASFS news

[sferrin]

Q&A with Air Force Chief of Staff Gen. David Goldfein

Q&A with Air Force Chief of Staff Gen. David Goldfein

www.nationaldefensemagazine.org

In the atmosphere, out the atmosphere ?

Probably just means satellites.

 

[jsport]

Q&A with Air Force Chief of Staff Gen. David Goldfein

Q&A with Air Force Chief of Staff Gen. David Goldfein

www.nationaldefensemagazine.org

In the atmosphere, out the atmosphere ?

"When you start looking at the key technologies that we know we have to develop that in some way, shape or form will come together to be able to accomplish the mission of air dominance, I'm not confident sitting here today that that's a single platform. I'm actually very confident it's not. I think it's a series of platforms — manned and unmanned, attributable and unattributable, penetrating, standoff, in the atmosphere, out of the atmosphere. And there will be members of our joint team, allies and partners that will contribute to the network required to achieve air dominance at the time and place of our choosing. "

 

[Jemiba]

I tried to clean up this thread a bit. Posts about external missile carriage on the F-22 were moved and merged with the (main)
F-22 thread here : https://www.secretprojects.co.uk/threads/lockheed-martin-f-22a-raptor.4505/page-26
The discussion about counter-UAS/anti-swarm weapons was split and can now be found here
https://www.secretprojects.co.uk/threads/the-sky-over-the-battlefield-of-the-future.34931/

If there are posts left, which should be moved, too, or someone comes up with a better title, just give a shout.

 

[bobbymike]

From Inside Defense pay site


Air Force finalizes NGAD acquisition strategy
The Air Force has finalized its Next-Generation Air Dominance acquisition strategy and expects to know by next month whether it will be adopted as part of the Pentagon's fiscal year 2022 budget request

 

[FighterJock]

I hope that the NGAD will be included in the 2022 budget request, the NGAD needs to be funded now because every country around the world seems to be designing fifth generation fighters right now. So the US needs to be ahead of the pact as far as air dominance is concerned.

 

[Bhurki]

I hope that the NGAD will be included in the 2022 budget request, the NGAD needs to be funded now because every country around the world seems to be designing fifth generation fighters right now. So the US needs to be ahead of the pact as far as air dominance is concerned.

It would be a mistake to risk the noise other countries are making about new gen fighters being equated to their efforts for the same.
There hasn't been significant funding for most of these programs.

On the other hand Ngad has been active for a few years with 'white' funding reaching almost $1B this year.

Add to that the speed of concerned subsystems going through the dev phase like engines from Advent - Aedp - Aetp - Ngap,
and munitions like peregrine, cuda, Lrew.

There is little doubt other exotic subsystems are being fed through additional black funding. Not to forget the underlying institutional infrastructure already present for taking on a project of this scope.

 

[FighterJock]

I hope that the NGAD will be included in the 2022 budget request, the NGAD needs to be funded now because every country around the world seems to be designing fifth generation fighters right now. So the US needs to be ahead of the pact as far as air dominance is concerned.

It would be a mistake to risk the noise other countries are making about new gen fighters being equated to their efforts for the same.
There hasn't been significant funding for most of these programs.

On the other hand Ngad has been active for a few years with 'white' funding reaching almost $1B this year.

Add to that the speed of concerned subsystems going through the dev phase like engines from Advent - Aedp - Aetp - Ngap,
and munitions like peregrine, cuda, Lrew.

There is little doubt other exotic subsystems are being fed through additional black funding. Not to forget the underlying institutional infrastructure already present for taking on a project of this scope.

I am surprised that NGAD was not developed in the Black World from day one after the issue of the Chinese hacking the information from the F-22/F35 fighters and developing the J-20 in double quick time.

 

[Sundog]

I am surprised that NGAD was not developed in the Black World from day one after the issue of the Chinese hacking the information from the F-22/F35 fighters and developing the J-20 in double quick time.

I'm not sure what good that would do. When China got all of the information on the F-35, they weren't actually trying to get that information from where they found it. They were trying to get information on another classified program that the Pentagon won't tell us about. So it's classified and the Chinese know about it, but we don't. I don't know why people think the only way for foreign entities to get information is through something made public.

 

[In_A_Dream]

I am surprised that NGAD was not developed in the Black World from day one after the issue of the Chinese hacking the information from the F-22/F35 fighters and developing the J-20 in double quick time.

Doesn't help when Chinese researchers, scientists, & engineers are deeply embedded in the Defense World. China probably has a good idea already what the concepts were, who won, and what subsystems America is going to go forward with.

 

[Bhurki]

I am surprised that NGAD was not developed in the Black World from day one after the issue of the Chinese hacking the information from the F-22/F35 fighters and developing the J-20 in double quick time.

I'm not sure what good that would do. When China got all of the information on the F-35, they weren't actually trying to get that information from where they found it. They were trying to get information on another classified program that the Pentagon won't tell us about. So it's classified and the Chinese know about it, but we don't. I don't know why people think the only way for foreign entities to get information is through something made public.

China knowing about the 'hidden' subsystems in partial or even absolute certainty still doesn't mean they have the means to counter it.
That requires an entire process of divising and operationalizing strategies and systems to counter it.
If anything, pentagon recognizing the leak about a system itself could be a gambit against other systems they seek to guard.
We're moving towards the deep end of speculation here.

 

[jsport]

Air Force ‘Digital Century Series’ Fighters: Technologically Exciting, Operationally Unworkable

A bright idea with legs everywhere except the battlespace.

www.forbes.com

Not

 

[dark sidius]

This guy article is at each time criticize, don't care of his opinion. Mr Roper is what the USAF need, you win war with new ideas not with blablabla!

 

[marauder2048]

This guy article is at each time criticize, don't care of his opinion. Mr Roper is what the USAF need, you win war with new ideas not with blablabla!

Roper is a strange bird; 10 years in grad school without any publications I could find.
And he didn't make a strong impression on the contemporaries of his that I talked to from MIT LL.

 

[Bhurki]

Roper is a strange bird

Agree, never seen a CV this strange in years.
I think its because most of his work is on black and only now surfacing projects including operational hypersonics.
He is also the founding director of Strategic Capabilities Office and has won Wash100 thrice, so i guess there was some recognition before he arrived at the post.

 

[Bhurki]

Navy establishes FA-XX program office.

Navy Quietly Starts Development of Next-Generation Carrier Fighter - USNI News

This post has been updated to clarify comments from Bryan Clark. After nearly a decade of fits and starts, the Navy has quietly initiated work to develop its first new carrier-based fighter in almost 20 years, standing up a new program office and holding early discussions with industry, USNI...

news.usni.org

"Compared to the F-35’s 700 nautical miles of combat radius, Clark said the Navy hopes to build a new fighter with a radius of 1,000 nautical miles."

If thats just on internal fuel, this thing's going to be massive !

 

[Dragon029]

Not necessarily; it's expected that next-gen fighters will be using a version of the new adaptive cycle engines being tested now, and those reportedly are capable of increasing range by more than 30%; an F-35C with an A100 or A101 engine would probably meet (or come very close to) that 1000nmi combat radius. Of course, I could definitely see the Navy wanting something bigger regardless in case they want a combat radius in excess of 1000nmi. If it's replacing the EA-18G as well you'll probably want big fuel tanks so that any NGJs hung externally don't prevent it from flying on longer sorties with the F-35Cs and other assets (unless they go with an EF-111-style integrated jammer variant).

 

[LMFS]

Not necessarily; it's expected that next-gen fighters will be using a version of the new adaptive cycle engines being tested now, and those reportedly are capable of increasing range by more than 30%; an F-35C with an A100 or A101 engine would probably meet (or come very close to) that 1000nmi combat radius. Of course, I could definitely see the Navy wanting something bigger regardless in case they want a combat radius in excess of 1000nmi. If it's replacing the EA-18G as well you'll probably want big fuel tanks so that any NGJs hung externally don't prevent it from flying on longer sorties with the F-35Cs and other assets (unless they go with an EF-111-style integrated jammer variant).

Is this increase of range related to a reduction of TSFC across all operational conditions of the engine or just in some of them? For instance the F135 is already very efficient in subsonic operation, a 30% reduction in consumption would mean a better TSFC than high-bypass turbofans in airliners.

I suspect those claims about massive improvements in the thrust and consumption of adaptive engines are rather related to the fact that they will give much more range than a low-bypass engine (i.e. F119) in subsonic flight and much more thrust than a higher bypass engine (i.e. F135) in supersonic flight. Otherwise the technological parameters of the engine would need to increase massively and this is already very difficult. I would appreciate if someone could clarify that point.

 

[shin_getter]

China Developing the J-20 Stealth Airframe Into a Twin Seat Airborne Early Warning and Control Jet

China’s Chengdu Aircraft Design Institute is reportedly developing a new twin seat combat jet based on the airframe of the J-20 stealth platform, with the aircraft

militarywatchmagazine.com

good idea or bad idea?

 

[Grey Havoc]

China Developing the J-20 Stealth Airframe Into a Twin Seat Airborne Early Warning and Control Jet

good idea or bad idea?

A somewhat dubious idea, IMHO, even allowing for it being used as a command & control platform for UCAV swarms and the like, though it could possibly be a cover for another program.

 

[TomcatViP]

They are probably misunderstanding the distributive targeting capability that stealth and a robust discrete data link could offer.

In a sense F-22 and mostly F-35 are already AWACS.

 

[Deino]

China Developing the J-20 Stealth Airframe Into a Twin Seat Airborne Early Warning and Control Jet

China’s Chengdu Aircraft Design Institute is reportedly developing a new twin seat combat jet based on the airframe of the J-20 stealth platform, with the aircraft

militarywatchmagazine.com

good idea or bad idea?

Plain stupid report based on the most unreliable source - namely Minnie Chan / SCMP - ... as such I would ban any report from her and the militarywatchmagazine from this forum.

 

[marauder2048]

Not necessarily; it's expected that next-gen fighters will be using a version of the new adaptive cycle engines being tested now, and those reportedly are capable of increasing range by more than 30%; an F-35C with an A100 or A101 engine would probably meet (or come very close to) that 1000nmi combat radius. Of course, I could definitely see the Navy wanting something bigger regardless in case they want a combat radius in excess of 1000nmi. If it's replacing the EA-18G as well you'll probably want big fuel tanks so that any NGJs hung externally don't prevent it from flying on longer sorties with the F-35Cs and other assets (unless they go with an EF-111-style integrated jammer variant).

Is this increase of range related to a reduction of TSFC across all operational conditions of the engine or just in some of them? For instance the F135 is already very efficient in subsonic operation, a 30% reduction in consumption would mean a better TSFC than high-bypass turbofans in airliners.

I suspect those claims about massive improvements in the thrust and consumption of adaptive engines are rather related to the fact that they will give much more range than a low-bypass engine (i.e. F119) in subsonic flight and much more thrust than a higher bypass engine (i.e. F135) in supersonic flight. Otherwise the technological parameters of the engine would need to increase massively and this is already very difficult. I would appreciate if someone could clarify that point.

The adaptive engines are reducing spillage drag which is big component for fighters at cruise.
Airliners, AFAIK, have no significant spillage drag since their installations are podded, inlet-less
and optimized strictly for subsonic cruise.

 

[LMFS]

The adaptive engines are reducing spillage drag which is big component for fighters at cruise.

Thanks, I was overlooking that contribution to drag...

 

[Dragon029]

Not necessarily; it's expected that next-gen fighters will be using a version of the new adaptive cycle engines being tested now, and those reportedly are capable of increasing range by more than 30%; an F-35C with an A100 or A101 engine would probably meet (or come very close to) that 1000nmi combat radius. Of course, I could definitely see the Navy wanting something bigger regardless in case they want a combat radius in excess of 1000nmi. If it's replacing the EA-18G as well you'll probably want big fuel tanks so that any NGJs hung externally don't prevent it from flying on longer sorties with the F-35Cs and other assets (unless they go with an EF-111-style integrated jammer variant).

Is this increase of range related to a reduction of TSFC across all operational conditions of the engine or just in some of them? For instance the F135 is already very efficient in subsonic operation, a 30% reduction in consumption would mean a better TSFC than high-bypass turbofans in airliners.

I suspect those claims about massive improvements in the thrust and consumption of adaptive engines are rather related to the fact that they will give much more range than a low-bypass engine (i.e. F119) in subsonic flight and much more thrust than a higher bypass engine (i.e. F135) in supersonic flight. Otherwise the technological parameters of the engine would need to increase massively and this is already very difficult. I would appreciate if someone could clarify that point.

It's a reduction in TSFC when the engine is operating in a high bypass mode, so that 30%+ will only apply at subsonic speeds, though frankly that's fine considering that there isn't any aircraft operational today that can supercruise for >400nmi on internal fuel (without IAR).

The F135's dry TSFC is said to be something like 0.57lb/lbf/hr, so a 30% decrease would only result in a TSFC of roughly 0.4lb/lbf/hr, which is still higher than airliner engines like the CFM56 that operate as low as 0.33lbf/lbf/hr, or even larger engines like the GE90 that get to <0.28lb/lbf/hr.

 

[LMFS]

It's a reduction in TSFC when the engine is operating in a high bypass mode, so that 30%+ will only apply at subsonic speeds, though frankly that's fine considering that there isn't any aircraft operational today that can supercruise for >400nmi on internal fuel (without IAR).

Yes that is what I mean. When the engine is in high-bypass mode, it will clearly be more efficient than a low-bypass engine. So a F-22 with such an engine would have a way longer range in subsonic than currently, that does not mean its range in supersonic (full mil power) would increase substantially, but for the inherent technological improvements between the two generations of engines rather than because of the new layout. As for the F-35, it would maybe give it a substantially higher speed in military power, but how much longer would its range in subsonic regime be would greatly depend on the maximum BPR the new engines provide, and even then, the higher the BPR, the more SFC worsens with speed.

The F135's dry TSFC is said to be something like 0.57lb/lbf/hr, so a 30% decrease would only result in a TSFC of roughly 0.4lb/lbf/hr, which is still higher than airliner engines like the CFM56 that operate as low as 0.33lbf/lbf/hr, or even larger engines like the GE90 that get to <0.28lb/lbf/hr.

Ok, I think my confusion comes from having seen TSFC data in different conditions. For the F135 I had read something like 0.7 or maybe a bit better, which makes sense for the bypass ratio of the engine, but this is probably static and at sea level (where did you see 0.57?). For the high-bypass turbofans you mention, the value I had seen was ca. 0.55, but that is in cruise mode, actually the flight regime that is relevant in this case. With TSFC at subsonic cruising speed for current fighter jets we could know if the claim of 30% reduction with newer engines makes sense or not, but I didn't find anything reliable yet...

 

[_Del_]

So a F-22 with such an engine would have a way longer range in subsonic than currently, that does not mean its range in supersonic (full mil power) would increase substantially

I don't know how substantially, but the corollary is that in supersonic flight you could push nearly all the air through the core and that is also going to give you higher efficiencies in the right conditions. Generically, if you push more air through the core than a F119 and retain exhaust velocity, you'll be more efficient at high speed than the F119.

You can move a lot of air slow, or a smaller amount of air fast to generate the same thrust. Generally, moving more air is more efficient (turboprop, undicted fan, high bypass)-- you steal energy from the core exhaust velocity to move more air.

But in the thrust equation, you need to subtract free stream velocity from exhaust velocity. So at higher speeds, you need higher efflux velocity for the same thrust. Another strike against high bypass in combat aircraft is the time it takes to spool up and down. You want finer control over thrust.

So each engine is tailored to a specific speed regime, accepting the compromises with whatever bypass ratio they choose. An F-22 is relatively low bypass bc it spends time at high speed and needs exhaust velocity for efficiency. F-35 has a larger bypass to take advantage of subsonic efficiency. If you have an engine that allows you to tailor your bypass ratio and exhaust velocity, you should get higher efficiency at all parts of the envelope than whatever the single compromise you would typically choose.

If the new engine has an option for a higher bpr than a F135 and lower possible bpr than a F119 and is similarly sized, it gives better efficiency all across the envelope. Or say the F135 size engine is the same bpr at max, but also allows lower bpr than the F135 by forcing air through the core, the F-35 will now have better supersonic efficiency (and possibly thrust) and lower spool times available as needed, but retains subsonic efficiency.

So instead of tailoring the engine to a specific best regime, you can tailor it to multiple points adjustable as needed. Bypassing the core for efficiency at lower speeds, or forcing more air down the core and getting higher efflux velocity at high speeds.

 

[Dragon029]

As for the F-35, it would maybe give it a substantially higher speed in military power, but how much longer would its range in subsonic regime be would greatly depend on the maximum BPR the new engines provide, and even then, the higher the BPR, the more SFC worsens with speed.

The range would increase by the 30%+ as mentioned; the adaptive cycle AETP engines (GE's XA100 and P&W's XA101) are both specifically designed / sized to fit the F-35 (they're by no means plug and play, but the F135 and F-35's engine bay was the reference size to match).

Ok, I think my confusion comes from having seen TSFC data in different conditions. For the F135 I had read something like 0.7 or maybe a bit better, which makes sense for the bypass ratio of the engine, but this is probably static and at sea level (where did you see 0.57?). For the high-bypass turbofans you mention, the value I had seen was ca. 0.55, but that is in cruise mode, actually the flight regime that is relevant in this case. With TSFC at subsonic cruising speed for current fighter jets we could know if the claim of 30% reduction with newer engines makes sense or not, but I didn't find anything reliable yet...

I got numbers mentally mixed up; 0.57 is the F135's bypass ratio, not TSFC - for the F135's TSFC there's competing numbers - there's 0.7lb/lbf/hr from one website published in 2004 that's incorrect about some F135 figures (so I don't trust it that much), and another of 0.886lb/lbf/hr that's supposedly from Janes, but with no specific reference, plus that number is rather high for an engine that should be relatively fuel efficient (exceptionally high combustion temperatures, a reasonable bypass ratio, etc). In any case you can look at TSFC numbers of other military turbofans here, and they're generally in the 0.7-0.8 range: http://www.jet-engine.net/miltfspec.html

Regardless of what the F135's TSFC is however, the 30%+ range increase is coming directly from GE and (kinda) P&W.

GE's website claims that their "ACE" (XA100) will offer a 50% improvement in loiter time, 35% increase in range, 25% reduction in fuel consumption and 60% increased heat transfer rate for the engine's heat exchangers: https://www.geaviation.com/military/engines/ge-adaptive-cycle-engine

P&W haven't given numbers for their XA101 / "F135 Growth Option 2" engine, but their "Growth Option 1" option, which just swaps out one of the F135 modules (without adding a 3rd airstream / adaptive cycle capabilities) offers 5-6% lower fuel burn and 6-10% greater thrust across the entire flight envelope of the engine; so evidently there's been improvements made in things like compressor and turbine design that offer increased fuel burn at the same bypass ratio: https://www.ainonline.com/aviation-...-outlines-three-step-f135-development-pathway

 

[_Del_]

An engine sitting on a bench, and an engine in flight at any given altitude and/or speed will have a different TFSC. Same with the engine throttle setting. All those figures could be exactly correct in different circumstances.

 

[Sundog]

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

 

[marauder2048]

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

"Power/Thermal Interaction within an Adaptive Turbine Engine" by Andrew K. DeSomma.

Injecting waste heat from electrical power generation into the 3rd stream:

Another consequence is that the additional heat causes the 3rd stream to behave like an impromptu burner
that increases the total engine thrust by about 113 lbf/MW. Due to this additional thrust the engine also
does not need to work as hard to achieve the required thrust.

 

[sferrin]

An engine sitting on a bench, and an engine in flight at any given altitude and/or speed will have a different TFSC. Same with the engine throttle setting. All those figures could be exactly correct in different circumstances.

Ugh. . .I hate this "argument". "But muh bench. . . " Nobody cares. OBVIOUSLY an engine sitting on a bench is going to behave differently than in the air. Do you really think GE and Pratt don't kn

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

"Power/Thermal Interaction within an Adaptive Turbine Engine" by Andrew K. DeSomma.

Injecting waste heat from electrical power generation into the 3rd stream:

Another consequence is that the additional heat causes the 3rd stream to behave like an impromptu burner
that increases the total engine thrust by about 113 lbf/MW. Due to this additional thrust the engine also
does not need to work as hard to achieve the required thrust.

113lbs for a 50,000lb thrust engine is almost in the noise.

 

[marauder2048]

An engine sitting on a bench, and an engine in flight at any given altitude and/or speed will have a different TFSC. Same with the engine throttle setting. All those figures could be exactly correct in different circumstances.

Ugh. . .I hate this "argument". "But muh bench. . . " Nobody cares. OBVIOUSLY an engine sitting on a bench is going to behave differently than in the air. Do you really think GE and Pratt don't kn

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

"Power/Thermal Interaction within an Adaptive Turbine Engine" by Andrew K. DeSomma.

Injecting waste heat from electrical power generation into the 3rd stream:

Another consequence is that the additional heat causes the 3rd stream to behave like an impromptu burner
that increases the total engine thrust by about 113 lbf/MW. Due to this additional thrust the engine also
does not need to work as hard to achieve the required thrust.

113lbs for a 50,000lb thrust engine is almost in the noise.

The engine thrust in the paper at those conditions is ~ 9500 lbs.

 

[sferrin]

An engine sitting on a bench, and an engine in flight at any given altitude and/or speed will have a different TFSC. Same with the engine throttle setting. All those figures could be exactly correct in different circumstances.

Ugh. . .I hate this "argument". "But muh bench. . . " Nobody cares. OBVIOUSLY an engine sitting on a bench is going to behave differently than in the air. Do you really think GE and Pratt don't kn

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

"Power/Thermal Interaction within an Adaptive Turbine Engine" by Andrew K. DeSomma.

Injecting waste heat from electrical power generation into the 3rd stream:

Another consequence is that the additional heat causes the 3rd stream to behave like an impromptu burner
that increases the total engine thrust by about 113 lbf/MW. Due to this additional thrust the engine also
does not need to work as hard to achieve the required thrust.

113lbs for a 50,000lb thrust engine is almost in the noise.

The engine thrust in the paper at those conditions is ~ 9500 lbs.

Wonder how that would translate to the bigger engine.

 

[_Del_]

Ugh. . .I hate this "argument"

I wasn't making an "argument".

He seemed confused that there were varying figures for the TFSC.

for the F135's TSFC there's competing numbers...

He followed with numbers he didn't "trust".

I just tried to explain that there is no absolute figure. The TFSC will depend on the circumstances. None of the numbers he quoted from various sources need to be "wrong" or not trusted. They can all be true for some given set of variables. High, medium, low altitude, military power, cruise setting, best endurance speed, best cruise speed, etc will all result in a different TFSC.

 

[marauder2048]

An engine sitting on a bench, and an engine in flight at any given altitude and/or speed will have a different TFSC. Same with the engine throttle setting. All those figures could be exactly correct in different circumstances.

Ugh. . .I hate this "argument". "But muh bench. . . " Nobody cares. OBVIOUSLY an engine sitting on a bench is going to behave differently than in the air. Do you really think GE and Pratt don't kn

You also have to look at the electrical power generation of these new power plants. Remember, due to all of the onboard systems fighters are now using, these are also designed for higher power generation, besides just higher thrust and better TFSC.

"Power/Thermal Interaction within an Adaptive Turbine Engine" by Andrew K. DeSomma.

Injecting waste heat from electrical power generation into the 3rd stream:

Another consequence is that the additional heat causes the 3rd stream to behave like an impromptu burner
that increases the total engine thrust by about 113 lbf/MW. Due to this additional thrust the engine also
does not need to work as hard to achieve the required thrust.

113lbs for a 50,000lb thrust engine is almost in the noise.

The engine thrust in the paper at those conditions is ~ 9500 lbs.

Wonder how that would translate to the bigger engine.

Good question. I just thought it was a "cute" result that waste heat isn't really wasted.

 

[sferrin]

Ugh. . .I hate this "argument"

I wasn't making an "argument".

Just disregard that. I'd started a reply and decided not to send it. Then the next time I responded, the previous text was still there albeit scrolled out of view.

 

[sferrin]

Good question. I just thought it was a "cute" result that waste heat isn't really wasted.

Read somewhere of a Martin Baker design (MB-5 maybe?) had its exhaust pipes oriented such that they produced forward thrust. (Maybe everybody did that.) Got hot air, may as well use it.

 

[Bhurki]

Geez, take it easy..
Its not so much the heat from the electrical system that needs to be used to create some extra thrust, but the requirement of efficiently dumping that heat into streams that are already present to direct that heat out of the jet without any negative impact to the electric internals.

So looking at the adaptive stage to be something that harnesses heat from the components to add thrust is trivial, since its mostly working as a heat pump to cool everything down. The extra thrust is just a little free obvious bonus.

 

[LMFS]

If the new engine has an option for a higher bpr than a F135 and lower possible bpr than a F119 and is similarly sized, it gives better efficiency all across the envelope. Or say the F135 size engine is the same bpr at max, but also allows lower bpr than the F135 by forcing air through the core, the F-35 will now have better supersonic efficiency (and possibly thrust) and lower spool times available as needed, but retains subsonic efficiency.

Yeah, that is exactly what I mean. Since the engine diameter is not going to change a lot, BPR may be increased compared to F135, but will it be by a big margin? Odds are that it is not going to be turned into a high bypass engine, and 30% reduction in consumption is a lot compared to an engine that is very modern and efficient already, and has been designed for subsonic flight. But I admit I dont have proof that is not the case. 30% less TSFC than a F119 in subsonic regime is realistic IMHO.

The range would increase by the 30%+ as mentioned; the adaptive cycle AETP engines (GE's XA100 and P&W's XA101) are both specifically designed / sized to fit the F-35 (they're by no means plug and play, but the F135 and F-35's engine bay was the reference size to match).

Ok I will read their statements with detail

I got numbers mentally mixed up; 0.57 is the F135's bypass ratio, not TSFC - for the F135's TSFC there's competing numbers - there's 0.7lb/lbf/hr from one website published in 2004 that's incorrect about some F135 figures (so I don't trust it that much), and another of 0.886lb/lbf/hr that's supposedly from Janes, but with no specific reference, plus that number is rather high for an engine that should be relatively fuel efficient (exceptionally high combustion temperatures, a reasonable bypass ratio, etc). In any case you can look at TSFC numbers of other military turbofans here, and they're generally in the 0.7-0.8 range: http://www.jet-engine.net/miltfspec.html

Maybe that value from Janes is cruise related? It would make sense...
Relatively high BPR in fighters go below 0.7 in uninstalled conditions, like the AL-31F for instance. It should be the case for F135 too, since it has similar BPR and way better technology.

GE's website claims that their "ACE" (XA100) will offer a 50% improvement in loiter time, 35% increase in range, 25% reduction in fuel consumption and 60% increased heat transfer rate for the engine's heat exchangers: https://www.geaviation.com/military/engines/ge-adaptive-cycle-engine

25% less consumption, 35% more range, 50% more persistence... it reads definitely like sales pitch / best case figures to me. They don't indicate what engine they are taking as reference, it may be F135 as you say but until now I have seen no proof, I will look further.

They also mention 60% more heat transference, in fact I seem to remember reading in an official document that the adaptive engines were critical to remove current restrictions regarding usable fuel and its temperature from the F-35. It may have an impact in those numbers, if for instance the fuel consumption is reduced a 25% plus due to better heat sink properties the engine allows to reduce the amount of non-usable fuel on board, they may in some circumstances reach that 35% extra range they announce. And of course, at high speeds it may not be possible to bypass so much air so that the heat sink function would not operate as effectively in that regime... it is a complex technology

P&W haven't given numbers for their XA101 / "F135 Growth Option 2" engine, but their "Growth Option 1" option, which just swaps out one of the F135 modules (without adding a 3rd airstream / adaptive cycle capabilities) offers 5-6% lower fuel burn and 6-10% greater thrust across the entire flight envelope of the engine; so evidently there's been improvements made in things like compressor and turbine design that offer increased fuel burn at the same bypass ratio: https://www.ainonline.com/aviation-...-outlines-three-step-f135-development-pathway

Exactly, the idea would be to decouple those technological improvements from the layout derived ones. It is not easy, though.

 

[Firefinder]

Another thing to consider for the range is any fuel increases or mods to the frame.

Say the navy decided to give the F35 a crank arrow delta wing, that will give you more fuel in the wings to have fun with. Design it well you may even get some better aerodynamics at cruise speeds.

So say the new adaptive engines just give a flat 20 percent increase to efficiently and range 90 percent of the time. And the new fuel load is about 20 percent more too, that will easily allow 1000 mile combat radius.

Then you have a conform fuel tank type of deal, that I sometimes sees toss around.

Honestly it be easier to just design a fresh design with all the new thing built in....