J-20 5th Gen Fighter Thread IV (Closed to posting)
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1) Of the 40% of the F-22's weight in titanium, not every ounce is devoted to bulkheads. Titanium isn't just used as a primary structure, but in support structures and places that need high heat tolerance. The smaller the titanium part, the more likely 3D printing will have weight savings benefits. Furthermore, there's still some 60% of mass that can be shaved off that's not titanium.Look at the diagram in figure 1 in this pdf : .
Also , this pic :
You will see that most of the F-22 titanium parts are not that complex , they are basically flat panels designed to give structural strength to the plane . Yes , there are some concavities and some welding , but this is relatively small and we are talking about hundreds of kilograms , not thousands . I claimed that weight reduction with 3D printing would be around 100 kg , max 200 and I stand by that assumption - even if I made a mistake it is not such a big deal , less then a weight of average weapon F-22 or J-20 would carry .
2) Even if both sintered and casted titanium require milling, the difference between casting and printing is still a matter of available geometries. The geometries accessible through the casting process are far more limited than 3D printing, which then determines how dependent you are on the milling process, which then imposes limitations on how light you can get your bulkheads due to tolerance issues with milling. For example, with sintering you can potentially afford to construct much bigger gaps and holes while maintaining desired structural strength by shaping the structure in ways that wouldn't be possible from casting. Generally a sintered piece will depend on less milling, and thus are not as subject to the limitations of the process.
Can't eyeball aerodynamics. Besides, how do you know either the PAK-FA or the F-22 can't supercruise with a 7-8 T:W class engine?Well , if J-20 had a tin, pencil like shape of Concorde maybe it could supercruise even with AL-31Unfortunately , J-20 doesn't look like Concorde and it is much more similar to F-22 or PAK FA - not a big surprise because they are all fifth gen fighters , not passenger planes
And yet, compromise solutions have a vast area potential of performance outcomes, so we can't make good specific predictions, which is exactly what we're trying to do when we assert object a can or can't reach such and such speeds.
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There are two variables that determine T/W ratio. One is Thrust. The other is weight. Either way, T:W ratio gives you a good idea of acceleration, not cruise speed. Granted, you need a certain amount of force for a given weight to punch past the mach barrier, but that particular parameter is as much determined by aerodynamics, as weight OR thrust. Hence aerodynamics IS important. To demonstrate this, I give you the example of the F-16XL.
"The second aircraft (a two-seater) had its experimental engine replaced with a General Electric F110-129. It accidentally achieved supercruise, a design goal of the F-16XL that was never attained in ETF testing, when it reached Mach 1.1 at 20,000 ft (6,096 m) on full military power."
Assuming a normal F-16 can't cruise at mach on an AL-31 class engine, this means aerodynamics is an important determinant. Assuming that a normal F-16 can cruise at mach on an AL-31 class engine, it means that you don't need a F119 class engine to cruise at mach.
I'm going to echo kwaigonegin on the point about the AL-31 not being the J-20's intended engine.
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Engineer
Major
Individual F-22 parts are not that complex because they are intentionally designed to be simple to enable manufacturing. More complex components will require welding of those simple parts together. With 3D printing, complex components can be made directly, thereby eliminating welds. A component is stronger without welds, allowing the piece to be made lighter. Here is an example of a part made using 3D printing, and concavities can be made much deeper in comparison.Look at the diagram in figure 1 in this pdf : .
Also , this pic :
You will see that most of the F-22 titanium parts are not that complex , they are basically flat panels designed to give structural strength to the plane . Yes , there are some concavities and some welding , but this is relatively small and we are talking about hundreds of kilograms , not thousands.
Tags: 3D Printing; China; components; wing;
The already points out that 40% of weight can be saved. 40% of 4300 kg is 1720 kg, which is 17 times of your 100 kg estimation. A difference of 17 times is actually a big deal.
F-22 is not a passenger plane and does not have a pencil-like shape like the Concorde, but that does not prevent F-22 from supercruise. A plane does not have to look like a Concorde to supercruise. So, your argument contradicts itself. What's more, the fact that Concorde can still supercruise despite having lower thrust-to-weight ratio than fighters remains unchanged.Well , if J-20 had a tin, pencil like shape of Concorde maybe it could supercruise even with AL-31
Nope. Maneuverability and flying straight are not mutually exclusive. Neither are speed and maneuverability mutually exclusive, since fighters can obviously be designed to satisfy both criteria.
Engineer
Major
That's not the definition of supercruise. Supercruise merely requires an aircraft to maintain supersonic speed without afterburner. It never requires that the aircraft has to break the sound barrier without afterburner.
Thrust-to-weight ratio does not determine supercruise ability, nevermind the "same plane category" garbage. Concorde thrust-to-weight ratio is merely around 0.3, and the aircraft can supercruise at Mach 2.0 without problem. F-15 cannot supercruise despite having higher thrust-to-weight ratio than F-22. From a post on our forum:
Quit making up pseudo flight dynamic theories.
This is irrelevant to whether J-20 can supercruise, since an aircraft supercrusing at a lower speed than F-22 is still supercruising. The definition of supercruise is to maintain supersonic speed without use of afterburner, not that the aircraft must fly as fast as F-22.
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MiG-29
Banned Idiot
The ability to supercruise is releted to the inlet, and TWR.Look at the diagram in figure 1 in this pdf : .
Also , this pic :
You will see that most of the F-22 titanium parts are not that complex , they are basically flat panels designed to give structural strength to the plane . Yes , there are some concavities and some welding , but this is relatively small and we are talking about hundreds of kilograms , not thousands . I claimed that weight reduction with 3D printing would be around 100 kg , max 200 and I stand by that assumption - even if I made a mistake it is not such a big deal , less then a weight of average weapon F-22 or J-20 would carry .
Well , if J-20 had a tin, pencil like shape of Concorde maybe it could supercruise even with AL-31
Yes they are . Most maneuverable planes (acrobatic planes) have thick stubby wings and fuselage . Fast planes have thin wings and thin fuselage and they cannot pull high g-s . Fighters tend to make compromise because they need both speed and maneuverability .
If the inlet works properly and the intake offers adequate air supply to the engine a high thrust to weight can be achieved.
J-20 is unlikely to supercruise with AL-31s, at the most it weighs like a Su-35BM at combat weight, so i doubt it has any operational supercruise capability
Stealth aircraft always will weigh more than earlier generations simply by having internal weapons bays and the need to pack all the fuel internally.
Does it have supercruise? who knows? but in my personal opinion it does not at this moment.
MiG-29
Banned Idiot
all comes to the intake, if you fly high and fast the inlet needs to supply air to the engine, pressure recovery loses mean the engine does not achieve is max thrust potential.
So it does not matter if you have th engines of the MiG-31, in order to supercruise you need to have perfect supply of air so the engine delivers its max potential.
once the engine falters you need afterburners to deliver high thrust and and engine in such conditions never achieve its max thrust at see level and static conditions, add Al-31 are not so powerful, so very likely it won`t supercruise in operational conditions.
thunderchief
Senior Member
40% of structural weight ! Around 9,600 lbs or 4200 kg as we said before . Quote from article : The program successfully incorporated 61 castings on the F-22; many of them utilized in critical
structural applications. The total poured weight for these castings is approximately 9,600 lbs., which
yielded a final weight of approximately 1,300 lbs. of cast parts on the F-22 airframe. The pour weight on
individual parts ranged from 1,200 lbs. for the largest casting to about 80 lbs. for the smaller hinge fittings
utilized in numerous applications. Machined to as casted weight ration range between 30% and 70%
I said that before , military thrust is more energy efficient then AB - but not that more. Energy from fuel is spent on defeating air resistance , on increase of kinetic energy , some of it is wasted (for example turned in thermal energy ) etc ... Difference in third part makes the difference in energy efficiency .
thunderchief
Senior Member
Well , most of the mass is devoted to bulkheads and supporting elements and they have relatively simple shape . The reason for using titanium in the first place was to provide strength to airframe . If they didn't want that they would use aluminum alloys which are both cheaper and lighter .
Smallest titanium parts are hinge fittings weighing 80lbs , according to the text I posted
First of all , sintered titanium has less structural strength then cast titanium because of the gaps in crystal structure (sintering process is not perfect ) . So , you cannot afford to have larger gapes and holes . Second , bulkhead shape is bulkhead shape
These are mostly right and straight angles , you cannot construct stronger bulkhead by curving it . Well , I know what could clean Su-27 do with Al-31 and what could clean Su-35 do with 117S . Given the J-20 or PAK FA shape and weight , and given the fact that Russians said that even 117S is not good enough for PAK FA , I could conclude certain things
Well , most of the mass is devoted to bulkheads and supporting elements and they have relatively simple shape . The reason for using titanium in the first place was to provide strength to airframe . If they didn't want that they would use aluminum alloys which are both cheaper and lighter .
Smallest titanium parts are hinge fittings weighing 80lbs , according to the text I posted
First of all , sintered titanium has less structural strength then cast titanium because of the gaps in crystal structure (sintering process is not perfect ) . So , you cannot afford to have larger gapes and holes . Second , bulkhead shape is bulkhead shape
Most of the structural mass is devoted to bulkheads and supporting elements. 3D printing can help with reducing the mass of non structural components too.
Bulkheads may have relatively simple shapes, but that's in part because the milling process imposes limitations on the kinds of geometries available. I'm aware that sintered material has less strength than casted ones, but the strength of a structure isn't just determined by material, but also how shape distributes force loads. That point on shaping doesn't have to refer to anything exotic like more curves either. It can refer to something as simple as dimensional limitations imposed by the casting and milling process. In areas where the expected force load is light you can afford to shave off more mass up to a certain point, but there's a limitation to that when you have to cast then mill the titanium (refer to the picture of the sintered part in Engineer's example).
As Engineer suggested, sintering also allows you to eliminate places where you'd have to weld the material, which means to get the same amount of strength in an area with welded parts you can afford lighter structures. This point is particularly true of support pieces that require welding, as welds can be where some of the greatest force loads are concentrated. Even though the crystalline structure of sintered pieces are imperfect a consistent shape will have fewer structural discontinuities and points of failure, which allows for the transference of force loads to where they're supposed to go and make the overall structure stronger. Finally, I'll let your own picture of the F-22 bulkhead answer your point about bulkhead shaping with regards to holes, gaps, curves, and right angles.
Your deduction doesn't necessarily conclude that those planes can't supercruise without a F119 class engine, but simply that Russia didn't think those engines fit their performance requirements. It's not like all supercruising is equal. I think the primary contention over this point has been whether the J-20 can supercruise with the AL-31, not whether that supercruising performance is adequate.Well , I know what could clean Su-27 do with Al-31 and what could clean Su-35 do with 117S . Given the J-20 or PAK FA shape and weight , and given the fact that Russians said that even 117S is not good enough for PAK FA , I could conclude certain things
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