Boeing to make USAF F-22 replacements

[Kurokage]

Was this one of the two 'unknown' aircraft that seen a few years back at altitude, and was derito shaped?

[Zaphod58]

Was this one of the two 'unknown' aircraft that seen a few years back at altitude, and was derito shaped?

No. The demonstrators didn’t start flying until 2020.

[EXETER]

“That would require an airframe designed for low drag at about Mach 3 while maintaining all the low observables and the jet engine that would power it.”

Why would they be required to demonstrate aerodynamics near Mach three for an airplane that very likely isn’t intended to move that quickly? Supercruise just means that the airplane can go faster than 1 mach without AB.

Here's the technical answer to your question:

It almost certainly IS intended to be able to cruise at around Mach 3.  This conclusion is based on the the image that Lockheed released of their NGAD design back in 2023, which can be viewed in the following article:

https://theaviationist.com/2023/07/09/lm...hter-logo/

When flying supersonically, one of the things that always happens is that a big shock cone attaches to the nose tip of the aircraft.  The angle that the cone makes relative to the fuselage centerline is directly related to the cruise Mach number.  Supersonic aircraft are designed such that all the wings and control surfaces are located behind and inside the shock cone.  If you look at the Lockheed NGAD design image and measure it you will find that the lateral distance from the fuselage centerline to a wingtip is just about 1/3 of the longitudinal distance from the plane of the nose tip back to the wingtip.  Also note that the wingtips are slightly clipped instead of coming to a single sharp point.  These are all indications that the aircraft is intended to fly inside a Mach 3 shock cone.  

If you look at the recently released images of the Chinese J-36 so-called 6th generation stealth fighter and do the same analysis you can conclude that it is designed to be able to cruise supersonically at maybe Mach 1.5.  

Both the NGAD and the J-36 appear to be supercruisers, but the NGAD is probably about twice as fast as the J-36.

Diving deeper into the technical analysis, we can infer why the NGAD would want to cruise around Mach 3, and it has to do with how the drag coefficient of an aircraft varies with Mach number.  Let's say you have an NGAD design and you take off and climb up to standard airliner altitudes of around 35 to 40 thousand feet at standard airliner speeds of less than Mach 1.  The drag coefficient of the airframe stays nearly constant up to about Mach 0.9.  That means that the aerodynamic efficiency with which the airplane will cover distance also stays nearly constant, regardless of the subsonic flight speed.  Around Mach 0.9, however the drag coefficient starts to rise steeply as shock fronts start to form and attach to the airframe, so it takes much more engine thrust to make the airplane fly through Mach 1.  This is what was called the "sound barrier" back in the early days of jet flight.  But at around Mach 1.1, the drag coefficient peaks at a level that is about 67% higher than at subsonic speeds, and then starts to go back down.  At around Mach 1.5 the drag coefficient is still about 50% higher than it is at subsonic speeds, so the J-36 will have a significant range penalty during supercruise compared to if it cruised at Mach 0.9.  

But the interesting thing is that the drag coefficient continues to decline with higher speed. At Mach 3, the drag coefficient is about half of what it is at Mach 0.9.  That means that a well designed super cruise aircraft at Mach 3 can fly about twice as far on a full fuel load than if it were slogging along subsonically, everything else being equal.  

So the operational envelope of the NGAD looks to be similar to the SR-71--Mach 3 at around 80,000 ft plus.  The difference is that the SR-71 was operating essentially on ramjet power at cruise, while the NGAD will be operating on a much more efficient combined cycle engine.  The SR-71 was basically a gigantic flying fuel tank, while the NGAD will be much more like a conventional fighter in terms of its fuel requirements. That's important because there are only a certain number of tanker aircraft available for aerial refueling, and you have to be able to put enough of these aircraft into the battle at the same time to make a difference. The advanced engine is what makes this whole concept feasible. Based on the fact that the J-36 has to use 3 big power hog engines to fly, it looks like they don't have that technology yet.

It looks to me like the main point of the NGAD is to be able to base it safely well outside the first chain of islands in the South China Sea in places like Japan, Guam, and probably Australia and still be able to get to the South China Sea quickly and with enough numbers to achieve air dominance there.

[Kurokage]

No. The demonstrators didn’t start flying until 2020.

So this wasn't one of the two test aircraft that was photographed around 2014 (Wichita and Texas)?

[Avicula]

Okay. That makes sense.

Along those lines, I have to say that one thing I am particularly looking forward to seeing from this and FA-XX are the adaptive cycle engines. Being able to optimize for both scalded ape speed and Sunday drive efficiency is VERY impressive. I’m seeing a lot of people loving the J-36 and its 3-engine layout. Seems fairly obvious, even to my simple ass, that that third engine is likely only there because they can’t produce engines that can support whatever systems are on board. I mean, the 8 year old in me thinks it LOOKS cool, but I can’t help but suspect that it’s a sign that China is still lagging behind when it comes to their ability to design and built adequate power plants for their stuff.

As the respective GE and P&W offerings mature and evolve, we’re are going to see some incredible capabilities follow. When they finally make that leap that provides all of that power at lower, manageable temperatures… THAT is going to be huge. All we need now is effective RAM that doesn’t impose a speed/time limit on those aforementioned sprints to and fro… That will be a wonderful day.

[Avicula]

That's true, but in this case super-cruise is such an integral part of the mission concept for this bird that I have to think they would have demonstrated that part of the technology.  That would require an airframe designed for low drag at about Mach 3 while maintaining all the low observables and the jet engine that would power it. I can't believe they would commit to a program of this magnitude without having demonstrated the basic aerodynamic performance. I agree that could be a somewhat smaller version of the production aircraft.

Here's the technical answer to your question:

It almost certainly IS intended to be able to cruise at around Mach 3.  This conclusion is based on the the image that Lockheed released of their NGAD design back in 2023, which can be viewed in the following article:

https://theaviationist.com/2023/07/09/lm...hter-logo/

When flying supersonically, one of the things that always happens is that a big shock cone attaches to the nose tip of the aircraft.  The angle that the cone makes relative to the fuselage centerline is directly related to the cruise Mach number.  Supersonic aircraft are designed such that all the wings and control surfaces are located behind and inside the shock cone.  If you look at the Lockheed NGAD design image and measure it you will find that the lateral distance from the fuselage centerline to a wingtip is just about 1/3 of the longitudinal distance from the plane of the nose tip back to the wingtip.  Also note that the wingtips are slightly clipped instead of coming to a single sharp point.  These are all indications that the aircraft is intended to fly inside a Mach 3 shock cone.  

If you look at the recently released images of the Chinese J-36 so-called 6th generation stealth fighter and do the same analysis you can conclude that it is designed to be able to cruise supersonically at maybe Mach 1.5.  

Both the NGAD and the J-36 appear to be supercruisers, but the NGAD is probably about twice as fast as the J-36.

Diving deeper into the technical analysis, we can infer why the NGAD would want to cruise around Mach 3, and it has to do with how the drag coefficient of an aircraft varies with Mach number.  Let's say you have an NGAD design and you take off and climb up to standard airliner altitudes of around 35 to 40 thousand feet at standard airliner speeds of less than Mach 1.  The drag coefficient of the airframe stays nearly constant up to about Mach 0.9.  That means that the aerodynamic efficiency with which the airplane will cover distance also stays nearly constant, regardless of the subsonic flight speed.  Around Mach 0.9, however the drag coefficient starts to rise steeply as shock fronts start to form and attach to the airframe, so it takes much more engine thrust to make the airplane fly through Mach 1.  This is what was called the "sound barrier" back in the early days of jet flight.  But at around Mach 1.1, the drag coefficient peaks at a level that is about 67% higher than at subsonic speeds, and then starts to go back down.  At around Mach 1.5 the drag coefficient is still about 50% higher than it is at subsonic speeds, so the J-36 will have a significant range penalty during supercruise compared to if it cruised at Mach 0.9.  

But the interesting thing is that the drag coefficient continues to decline with higher speed. At Mach 3, the drag coefficient is about half of what it is at Mach 0.9.  That means that a well designed super cruise aircraft at Mach 3 can fly about twice as far on a full fuel load than if it were slogging along subsonically, everything else being equal.  

So the operational envelope of the NGAD looks to be similar to the SR-71--Mach 3 at around 80,000 ft plus.  The difference is that the SR-71 was operating essentially on ramjet power at cruise, while the NGAD will be operating on a much more efficient combined cycle engine.  The SR-71 was basically a gigantic flying fuel tank, while the NGAD will be much more like a conventional fighter in terms of its fuel requirements. That's important because there are only a certain number of tanker aircraft available for aerial refueling, and you have to be able to put enough of these aircraft into the battle at the same time to make a difference. The advanced engine is what makes this whole concept feasible. Based on the fact that the J-36 has to use 3 big power hog engines to fly, it looks like they don't have that technology yet.

It looks to me like the main point of the NGAD is to be able to base it safely well outside the first chain of islands in the South China Sea in places like Japan, Guam, and probably Australia and still be able to get to the South China Sea quickly and with enough numbers to achieve air dominance there.

THANK YOU!!! That has to be one of the clearest and most concise replies I have ever seen in an aviation forum. Even better, IT MAKES SENSE! I have a very irritating type of numerical dyslexia (dyscalculia) that ruined my future as an aeronautics engineer decades before it ever would have started. I can hang relatively well when the math is converted into concepts and words as you did above. Being able to convey complex ideas in a simple manner is a sign of REAL understating and you nailed that reply to the wall.

[sahgwa]

I hope that the factories and people that build the military's aircraft at Boeing are different than the factories and people that build the passenger jets at Boeing.