Time for 100K lbs of AB Thrust?

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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sferrin

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Unread post01 Sep 2021, 18:22

mixelflick wrote:
rowbeartoe wrote:One thing I just have to say about the F-18 Super Hornet. It's a very capable Jet, but those engines have got to be underpowered for it's weight. I mean an F-15E weighs about the same empty as the SH does (32,000 lbs) yet the AB thrust for the F-15E and EX is slightly over 58,000 vs "only" 44,000 in AB.


It has long been known the SH is under-powered (continuing the tradition of most "legacy" hornets). It's just part of the compromises made on the jet. But hey, Boeing built 500+ and in so doing pulled the wool over the eyes of a lot of Congressmen. Of course, the jet has its strong points too.

Thrust to weight just generally isn't one of them..


And it's not like they couldn't put a pair of EPEs in them (26k+) if they felt it was worth it.
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Unread post01 Sep 2021, 18:30

The subsonic performance of the SH is great with the standard F414s. If the Navy feels like supersonic performance isn't needed then why would they.
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Unread post02 Sep 2021, 00:52

sprstdlyscottsmn wrote:The subsonic performance of the SH is great with the standard F414s. If the Navy feels like supersonic performance isn't needed then why would they.


I remember reading back in the good ol days about the F-16 fighting the Mig-29 and the F-16 pilots saying how similar the Mig-29 was to the F-18 at slow speeds (being better than the F-16) but that unlike the F-18, the Mig-29 could accelerate faster and get back into the high speed fight.

I mention this because I would imagine more thrust for the SH would equate to better acceleration at subsonic speeds. That seemed important to that F-16 pilot back then. He also mentioned how much of an advantage the F-16 had over both Jets in the high speed fight.

As to why the Navy wouldn't invest or want more thrust for the SH I'm sure we could come up with a lot of reasons, but perhaps the biggest concern would be what I've read was the Hornets original concern, range.

That said, there is a lot that makes a Fighter Jet great these days, thrust to weight maybe one of them, but I doubt this, along with agility and maneuverability is much of a priority these days. Stealth, range, avionics, situational awareness, weapons, etc probably has more preference. But still, I'm thinking you can't go wrong with two 50K AB thrust engines in an aircraft that weighs under 50K empty would be a bad thing. :)
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Unread post02 Sep 2021, 03:00

But still, I'm thinking you can't go wrong with two 50K AB thrust engines in an aircraft that weighs under 50K empty would be a bad thing.


That was kind of my idea for a battleship cruiser, high stealth and sustained speed with range, that could clandestinely surveil the battlespace. Probably tailless and with a huge fuel fraction. Basically those were my numbers: 50K empty weight, 30K of gas, and 100K of thrust. Could be science fiction...but one must wonder what the various iterations of the USAF's NGAD looks like
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Unread post02 Sep 2021, 06:33

jetblast16 wrote:
But still, I'm thinking you can't go wrong with two 50K AB thrust engines in an aircraft that weighs under 50K empty would be a bad thing.


That was kind of my idea for a battleship cruiser, high stealth and sustained speed with range, that could clandestinely surveil the battlespace. Probably tailless and with a huge fuel fraction. Basically those were my numbers: 50K empty weight, 30K of gas, and 100K of thrust. Could be science fiction...but one must wonder what the various iterations of the USAF's NGAD looks like


I'd be surprised if the NGAD doesn't have those kinds of numbers. 40-50K lbs empty. Two 50K AB thrust engines. 20-30K of gas.

Perhaps a different kind of fighter as well. Perhaps it will be able to have Mach 2 cruise like the concord. Fly at 80K feet and a few more tricks that those engines and flight design will allow. Maybe Spaceforce will have some influence with it's design?
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Unread post02 Sep 2021, 14:53

40-50 isn't big enough. That is F-14/F-22 territory. 50-60 is what it will take if you want 30k fuel, minimum. All of a sudden 100k thrust is "just enough"
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Unread post02 Sep 2021, 14:56

The Navy's choice of SH engine was driven largely by the same requirements for the rest of the jet: Affordability, maintainability etc.. There was never a requirement for it to out-perform/specifically counter certain enemy jets (F-15/TFX requirements to best the Mig-25). So it doesn't surprise me the Navy didn't want more powerful motors. They would have probably had a shorter TBO, used more gas etc. and this would only exacerbate some of its existing shortcomings.

I can see 50,000lb motors for PCA or NGAD. The F-35 is flying with a 43,000lb motor now and soon, even more.. let's say 45,000. 5,000lbs more isn't that far of a jump, especially if they make some sort of propulsion breakthrough somewhere along the way..
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Unread post02 Sep 2021, 16:02

mixelflick wrote:The Navy's choice of SH engine was driven largely by the same requirements for the rest of the jet: Affordability, maintainability etc.. There was never a requirement for it to out-perform/specifically counter certain enemy jets (F-15/TFX requirements to best the Mig-25). So it doesn't surprise me the Navy didn't want more powerful motors. They would have probably had a shorter TBO, used more gas etc. and this would only exacerbate some of its existing shortcomings.

I can see 50,000lb motors for PCA or NGAD. The F-35 is flying with a 43,000lb motor now and soon, even more.. let's say 45,000. 5,000lbs more isn't that far of a jump, especially if they make some sort of propulsion breakthrough somewhere along the way..


NGAD engines will be physically BIGGER than the F135. Bigger AND higher tech. 50k would be nothing for these.
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Unread post02 Sep 2021, 21:14

sprstdlyscottsmn wrote:40-50 isn't big enough. That is F-14/F-22 territory. 50-60 is what it will take if you want 30k fuel, minimum. All of a sudden 100k thrust is "just enough"


Teh-he-he-he; my "real" numbers for my battlecruiser are 50k empty, 35k for fuel, and 105k for thrust (52.5K per engine), but shh...don't tell anyone. We don't want the Navy to know what we are up to..
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Unread post02 Sep 2021, 21:37

sferrin wrote:Next gen "3-stream" engines from P&W and GE are limited to the F-35's fuselage envelope. HOWEVER, they are also working on a follow on that is NOT constrained by the need to fit in the F-35. That one will be the NGAD engine.


I think it is more problem with intake and S-duct then with F-35 being small for new engine. I mean F135 is BIG engine I doubt they will go with something bigger.

So new engines probable need bigger intake and modified S-duct to be beneficial which would require redesigning F-35 and that would cost a lot so why bother with that?

In case of NGAD engines will be same size but with intake and duct optimal for those engines.

That is my POV, it could be wrong. Maybe they mentioned they are doing on scaled up engines, but I really don't see why.
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Unread post03 Sep 2021, 12:51

milosh wrote:
sferrin wrote:Next gen "3-stream" engines from P&W and GE are limited to the F-35's fuselage envelope. HOWEVER, they are also working on a follow on that is NOT constrained by the need to fit in the F-35. That one will be the NGAD engine.


I think it is more problem with intake and S-duct then with F-35 being small for new engine.


Based on what? In your scenario, what would be the point of making a second type of follow on engine if it was going to fit in the same envelope as the F135?
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Unread post03 Sep 2021, 17:50

sferrin wrote:
milosh wrote:
sferrin wrote:Next gen "3-stream" engines from P&W and GE are limited to the F-35's fuselage envelope. HOWEVER, they are also working on a follow on that is NOT constrained by the need to fit in the F-35. That one will be the NGAD engine.


I think it is more problem with intake and S-duct then with F-35 being small for new engine.


Based on what? In your scenario, what would be the point of making a second type of follow on engine if it was going to fit in the same envelope as the F135?


From what I read XA100 and XA101 are F135 size but that doesn't mean they can be use for F-35 without modifications and I gave my option what is problem, size isn't (used to their max capability).

If there is plan to make scaled up XA100/XA101 I didn't know about it.
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Unread post03 Sep 2021, 22:22

milosh wrote:From what I read XA100 and XA101 are F135 size but that doesn't mean they can be use for F-35 without modifications and I gave my option what is problem, size isn't (used to their max capability).

If there is plan to make scaled up XA100/XA101 I didn't know about it.


The XA100/XA101 are the engines that are designed to drop into an F-35. There is also a program for development engines that are not limited to the F135 envelope.

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Unread post04 Sep 2021, 16:02

milosh wrote:
sferrin wrote:Next gen "3-stream" engines from P&W and GE are limited to the F-35's fuselage envelope. HOWEVER, they are also working on a follow on that is NOT constrained by the need to fit in the F-35. That one will be the NGAD engine.


I think it is more problem with intake and S-duct then with F-35 being small for new engine. I mean F135 is BIG engine I doubt they will go with something bigger.

So new engines probable need bigger intake and modified S-duct to be beneficial which would require redesigning F-35 and that would cost a lot so why bother with that?

In case of NGAD engines will be same size but with intake and duct optimal for those engines.

That is my POV, it could be wrong. Maybe they mentioned they are doing on scaled up engines, but I really don't see why.


Can't agree the intakes will be the limiting factor, at least on NGAD. We seem to have had no problem with S-ducts on the F-22, YF-23A etc.. and the jump from the F-15 to the ATF/F-22 was huge. It seemed to me the engine itself was the greater challenge (F-119), and I think the same will hold true for whatever powers NGAD. Ditto for advanced derivatives of the F-135. The engine itself will be the greater engineering issue, not the intakes.

NGAD will no doubt be more capable than the F-22, but by how much? Perhaps the better question may be: How much is "enough"?

100,000lbs thrust, vast increase in range, much greater than 1:1 TW ratio, plus even better sensors/weapons than the F-35 currently has..... going to be BIG money. Do you design something 100% more effective than the F-22/35 and only buy 200 of them? Or something 50% more effective and buy 400?

It's a tough call, but that's why the bigshots get the big $. Hopefully this time, they make the right one...
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Unread post04 Sep 2021, 17:12

I was writing about F-35 not NGAD, of course intakes will be design for next gen engines.

I still doubt need for some huge thrust boost if you ask me two F135 are more then enough.

For example two F135 on max dry thrust deliver only little less then what F-14D had with two F110 on max afterburner thrust.

Better fuel economy and super cruise peformances are lot more important then better afterburner thrust.
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