Penetrating Counter Air / Next Generation Air Dominance

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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f119doctor

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Unread post14 Feb 2020, 20:37

hkultala wrote:Only about 22-23 klbs of that 28k is thrust from the core, and works at supersonic speeds. The rest 5-6 klbs comes from bypass air, which is only adding drag, not thrust, at supersonic speeds without afterburner. (because the air has to be slowed down to subsonic speed at the inlets, but the fan cannot accelerate it back to supersonic speed).

EJ200 engines of EF Typhoon has lower bypass ratio, giving them together about equal core thrust, and less drag from the bypass air. But EF Typhoon is a smaller plane, with less drag on clean configuration.

With an engine with core thrust of something like 25 klbs, F-35 would have no trouble of supercruising.


That is not really how modern mixed flow afterburning turbofan engines work. The bypass flow and core exit flow are mixed at roughly equal pressures and exit through the exhaust nozzle together to make thrust. The fan pressure ratio essentially sets the engine pressure ratio, and you can’t say the bypass air is not making thrust during supersonic flight.

An engine pressure ratio of 2 gets you sonic flow from the exhaust. A F100-220 and the F110-100 have an EPR of approximately 3, which gets you a supersonic exhaust, so you can make some Mil thrust above M1, but not enough to maintain above the transonic range. You have to push the fan / engine pressure ratio significantly higher than that to get supercruise thrust at Mil power.

To supply the extra power to drive the fan at the higher pressure ratio take more core power. You can run the core harder and hotter, or you can make it bigger (I.e. lower bypass ratio).

The other issue with supercruise as traditionally defined as 1.5M, 40K has a 100F inlet temp on a standard day. Most engines make their maximum thrust at 60F -70F inlet temp. They run into turbine speed and temperature limits as the inlet temp increases, and the thrust declines as the inlet get hotter. So to maintain that supercruise thrust, the engine has to be designed with enough rotor speed and temperature margin to produce full thrust under that 100F inlet condition.
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Unread post15 Feb 2020, 15:52

wrightwing wrote:
I suspect the agility requirements will be lower priority to range, payload, speed, signature reduction, and situational awareness.

That's my problem with the whole 1 size fits all design, you need range, speed, stealth and deep magazines and you would like to squeeze in some agility and speed too,

some of these cannot co exist. Range and deep magazines require size and weight which is the enemy of agility and speed. Since Agility and speed may be less required, your PCA will probably be a step backwards in performance over the aircraft it will eventually replace.

Even today with the F-22 and F-35 the USAF says this
Colonel Charles Moore wrote:
Given all of these considerations, it’s not hard to imagine the
F-35 finding itself in an environment where it is out of missiles or not within missile
parameters and completely dependent upon its gun system to defend itself and complete
its mission.
[/quote]

Capabilities should be added without the sacrificing other capabilities. The F-22 was more capable than the F-15 in every tactically relevant scenario so was the F-15 over the F-4.

The F-4 was pushed into an air superiority role despite being originally designed as a fleet interceptor and less capable than the F-8 in traditional close range engagements. We all know how many painful lessons that gave us.
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Unread post15 Feb 2020, 16:07

hkultala wrote:
No, it's not. It's equally-designed for air-to-air and air-to ground.

According to F-35 pilot Maj. John Searcy
The F-35 is not really designed for air to air (although it is capable of it) however, emphasis on the design is put on SEAD/DEAD and deep strike capabilities.

Listen here:
https://www.youtube.com/watch?v=ITCerewkIQE

Early in the JSF program the figure 60/40 was thrown around a lot. 60% for A-G and 40% for A-A was the design goals. However that 40% should still be more than enough to combat any potential adversary out there


hkultala wrote:No amount of modernizing of F-22 will bring it's range to even close to what is required for PCA.

What ever they choose to go with PCA, the KC-Z Stealth tanker will still push through.
So you don't need to have heavy bomber like range. You simply need to reduce tanker requirements to a degree.

And like I said, any fighter PCA proposal will only make up one component of the PCA family, another component may be a large Stealthy missile truck that will rely on stand off weapons.
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Unread post15 Feb 2020, 18:42

zero-one wrote:
wrightwing wrote:
I suspect the agility requirements will be lower priority to range, payload, speed, signature reduction, and situational awareness.

That's my problem with the whole 1 size fits all design, you need range, speed, stealth and deep magazines and you would like to squeeze in some agility and speed too,

some of these cannot co exist. Range and deep magazines require size and weight which is the enemy of agility and speed. Since Agility and speed may be less required, your PCA will probably be a step backwards in performance over the aircraft it will eventually replace.



I didn't say that agility wouldn't be a consideration, it just won't take precedence over the more important considerations. We're not talking about designing a new plane that has F-105/F-111 agility. It just won't have to be equal/superior to F-22 agility, to be useful. By the time the PCA enters service, it will very likely have directed energy weapons in addition to a larger missile magazine. This combined with greater range, lower RCS/IR signatures, greater supercruise endurance, will be far more important than any °/second factors. Superior situational awareness combined with HOBS/360° spherical engagement, have made other factors moot.
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sferrin

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Unread post15 Feb 2020, 19:19

zero-one wrote:That's my problem with the whole 1 size fits all design, you need range, speed, stealth and deep magazines and you would like to squeeze in some agility and speed too, some of these cannot co exist. Range and deep magazines require size and weight which is the enemy of agility and speed.


Which would you say is more agile, a P-80 or a Su-27?
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Unread post15 Feb 2020, 19:53

PCA maneuverability is about evading missiles, not engaging in dogfights. There is zero reason to engage in a dogfight. There is plenty of reason to plan for successful disengagement when they fail to approach undetected, engage annd unsuccessfully prosecute their target, or perhaps get jumped by chance opportunity by the enemy.

The more talk about PCA that I hear, the more I believe this design is going to be a combination of drone command & control combined with supercruise spyplane mated to the shoot & scoot concept. I'm also thinking these will be strategic assets, not tactical.
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Unread post16 Feb 2020, 04:20

madrat wrote:PCA maneuverability is about evading missiles, not engaging in dogfights. There is zero reason to engage in a dogfight. There is plenty of reason to plan for successful disengagement when they fail to approach undetected, engage annd unsuccessfully prosecute their target, or perhaps get jumped by chance opportunity by the enemy.

The more talk about PCA that I hear, the more I believe this design is going to be a combination of drone command & control combined with supercruise spyplane mated to the shoot & scoot concept. I'm also thinking these will be strategic assets, not tactical.


Think something like a stealthy YF-12 / XF-108 to today's F-106.
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Unread post16 Feb 2020, 12:02

sferrin wrote:Which would you say is more agile, a P-80 or a Su-27?


I don't have enough information on the P-80, but i guess there will be speeds where the P-80 has the upper hand. However I would also guess that the Su-27 has the advantage in most of the flight envelope.

If PCA will be at a disadvantage against the F-22 in most parts of the envelope then it will be an issue. Specially with the proliferation of Stealthy adversaries. The need to kill them before they get within range goes through the roof.

To me a very large aircraft that can go to China and back in one tank of gas from Hawaii with a very deep magazine seems to be an accurate description of the B-1, even the B-1 would need tankers for that, so it'll be bigger than a B-1. How that can be done while maintaining anywhere close to fighter like kinematics. It will most likely be a stealthy subsonic bomber like plane with dozens of missiles.
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Unread post16 Feb 2020, 16:45

zero-one wrote:
sferrin wrote:Which would you say is more agile, a P-80 or a Su-27?


I don't have enough information on the P-80, but i guess there will be speeds where the P-80 has the upper hand. However I would also guess that the Su-27 has the advantage in most of the flight envelope.

If PCA will be at a disadvantage against the F-22 in most parts of the envelope then it will be an issue. Specially with the proliferation of Stealthy adversaries. The need to kill them before they get within range goes through the roof.

To me a very large aircraft that can go to China and back in one tank of gas from Hawaii with a very deep magazine seems to be an accurate description of the B-1, even the B-1 would need tankers for that, so it'll be bigger than a B-1. How that can be done while maintaining anywhere close to fighter like kinematics. It will most likely be a stealthy subsonic bomber like plane with dozens of missiles.

Where are you getting an intercontinental range requirement from? Absolutely nobody has ever suggested that sort of range for the PCA. It's not going to be a B-1B sized aircraft, nor does it need to exceed F-22 level agility. It's as if there have never been posts with F-22/35 pilots talking about what's important in modern aerial combat, whenever you start opining. Superior situational awareness is the single most important factor, in determining outcomes in combat. Not who has the highest °/second performance. SA combined with HOBS/spherical engagement has rendered that a moot point. SAMs will always be the biggest threat, and A2A combat of stealthy aircraft will be increasingly like sub warfare, not Red Baron dogfights.
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sferrin

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Unread post16 Feb 2020, 17:17

zero-one wrote:
sferrin wrote:Which would you say is more agile, a P-80 or a Su-27?


I don't have enough information on the P-80, but i guess there will be speeds where the P-80 has the upper hand. However I would also guess that the Su-27 has the advantage in most of the flight envelope.

If PCA will be at a disadvantage against the F-22 in most parts of the envelope then it will be an issue.


Whether accidentally, or on purpose, you got my point exactly backwards.
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Unread post16 Feb 2020, 17:45

But if they push parameters that F-22 cannot engage then its fundamentally an apples to oranges comparison no different than P-80 being compared to Su-27. F-22 is high altitude and supercruise, but that doesn't mean it is potentially the highest and fastest. If PCA somehow is able to reach 100,000 feet and flies at say Mach 2 under a supercruise, it makes the F-22 only a threat in very limited parameters. Now imagine the PCA engaging the F-22; it is not so limited in its ability to engage on these terms.

The one destabilizer is directed energy weapons. If PCA needs to operate high, do directed energy weapons neutralize its potential? I'd hate to spend $100 billion on vaporware.
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sferrin

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Unread post16 Feb 2020, 19:12

madrat wrote:But if they push parameters that F-22 cannot engage then its fundamentally an apples to oranges comparison no different than P-80 being compared to Su-27. F-22 is high altitude and supercruise, but that doesn't mean it is potentially the highest and fastest. If PCA somehow is able to reach 100,000 feet and flies at say Mach 2 under a supercruise, it makes the F-22 only a threat in very limited parameters. Now imagine the PCA engaging the F-22; it is not so limited in its ability to engage on these terms.

The one destabilizer is directed energy weapons. If PCA needs to operate high, do directed energy weapons neutralize its potential? I'd hate to spend $100 billion on vaporware.


My point was that larger size/weight doesn't automatically mean inferior maneuverability. That said, we're not talking about PCA even needing to be a dog-fighter. I'd want more maneuverability than a Blackbird but I don't see the need for 9 gs. If you could get it without sacrificing range and payload (and not breaking the bank), sure. But I'd put it as more of a "nice to have" rather than "must have".
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Unread post17 Feb 2020, 00:50

At extreme height and speed you can reach 9G rather quickly.
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sferrin

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Unread post17 Feb 2020, 15:35

madrat wrote:At extreme height and speed you can reach 9G rather quickly.


True enough. The Tomcat had the glove vanes so it could maintain the ability to pull high-ish Gs over Mach 2.

"These vanes are automatically deployed when the speed exceeds Mach 1.4 in order to push up the nose and unload the tailplanes, giving them enough authority to pull 7.5 g at Mach 2."

Let me rephrase. I don't think it needs to be able to turn 28 deg/sec.
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Unread post17 Feb 2020, 16:02

madrat wrote:At extreme height and speed you can reach 9G rather quickly.


Yeah, and with a turn radius the size of Montana...
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