J-20 5th Gen Fighter Thread VI

[Deino]

how even if the combined surface area of the ventral strakes and vertical stabilizers was comparable to the surface area of the F-22’s vertical tails the F-22’s vertical tails

I have since checked my hunch that vertical tail area on the J-20 isn't reduced as much compared to the F-22 as horizontal stabilizer (canard) area with a good beam photo and it was confirmed. Fin + strake area is scaled down to a factor of about 0.7, canard area to 0.6 - I applied the latter in my calculation though (i.e. I acted as thought he J-20 has somewhat smaller fins than it really does). So I don't think there's scope for crediting the J-20 with a greater weight reduction for empennage area than I already did.

Where I withhold certainty is with the other factor of the weight question, which is density. Density can’t be eyeballed. If the J-20 were to be significantly lighter than the F-22 that’s the side of the equation where it’d have to be different. It’s not completely unfathombale either, to be honest. The X-35 was only 9 tonnes, the YF-22 was only 15 tonnes, and the YF-23, despite being a dimensionally larger plane than the YF-22, was only 13 tonnes. Of course these are clean sheet prototypes, so you can only stretch this point so far, but I think it carries a very strong point, which is that this weight disputed is not purely a matter of spatial dimensions.

Driving down density comes with serious compromises on certain aspects of the design (g-limit, fuel capacity, weapons bay size - that kind of stuff) though, as those demonstrators you mention quite conveniently exemplify. It's no accident that the production aircraft which grew out of them were all substantially heavier - the proof of concept airframes were without exception far from combat-capable at that weight. None carried anything like a full avionics suite, none were fitted with RAM treatments and the X-35 even lacked weapons bays as well as having a reduced fuel capacity - lots of air in there:

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Likewise, the YF-23 was much more of an empty shell than the YF-22 (it did have weapons bays but they were not functional whereas Lockheed actually testfired an AMRAAM etc.) - the manufacturer's own weight projections for the production aircraft put F-23 empty weight *higher*. Both these points reputedly contributed to the victory of the F-22, as it was judged more mature (its demonstrator was closer to a combat-capable aircraft) and lower cost (weight is a cost driver).

You mean, overwhelming excluding what China's 3D printing industry claims to have achieved.

No, excluding what the 3D printing industry as a whole *claims* to have achieved Read Sciaky's description of what they'd like customers to believe their machine is capable of and compare/contrast with the apparent experience in the field at Airbus. Perhaps it's too pessimistic an attitude, but I'm simply assuming the signal-to-noise ratio from the Chinese 3D printing industry is broadly the same as it has historically proven to be with their counterparts elsewhere.

The problem isn't on the milling control side of the equation, but the material side of the equation. No matter how good the control system is you still need to factor in the properties of the material you're milling. Titanium's hardness and rigidity means that below a certain material thickness even the most finely controlled milling will produce a high risk of cracking, especially if you're applying direct force such as when you're cutting holes (if I'm not mistaken this is the *primary* thickness limitation with titanium).

Actually the main attraction is time and cost.

No hostility intended either, but as I said before, I find the idea that the F-22 is overweight to the tune of several tons due to bulkheads which are thicker than what the load bearing requirements demand, simply because they can't machined any thinner, scarcely credible. Do you have a source which says that loud and clear? BTW, larger holes/openings (for instance the intake ducts) are incorporated into the forging before machining - the smaller one would not amount to machining so much as drilling.

Technically, it doesn't need to match the material properties of machined forging. It just needs to fit the structural needs of the mechanical loads it's being subjected to.

I doubt billets for bulkheads would undergo processing and forging for months at astronomical cost just to endow them with properties which are not actually required...

Furthermore, these same stories also seem to be advertising that they're applying it to at least some of their fighters. How else did we get the news about 3D printed bulkheads in stealth fighters?

People jumping to conclusions? It does happen For that matter, when the 15t figure was mentioned are we certain it refered to OEW (as in operational) and not bare airframe weight (without engines & some equipment - 15t would be perfectly believable for that)? Or it's the weight of #2001/2002 and they were largely empty demonstrators?

Has there been specific confirmation that Chinese fighters not only use 3D printed parts in general (things like jobjed's pipe fitting - perfectly credible and still a boon from a cost and time perspective) but actual bulkheads?

I mean, what makes a Chinese University's claim to have printed a bulkhead different to Sciaky's claim to have printed a spar? With the latter, not only was Airbus apparently unhappy with the result, they were unhappy enough to turn to a competely different partner for further development. Just because the makers of a 3D printer (and it matters not where they hail from) says so obviously doesn't mean it's true - I'd just be rather more inclined to believe claims from an actual airframer (i.e. the customer)

If you followed the series of 2013 stories on Chinese 3D printing closely, they *do* seem to be advertising their 3D printing for the C919 though.

"The Northwestern Polytechnical University of China is also making five meter-long titanium wing beams for the C919 passenger plane, which is scheduled to be put into commercial operation in 2016."

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That's more like it - thanks! Where on the C919 does that beam go though? A floor beam for example would say nothing about the applicability of the manufacturing process to a more highly-loaded part like a bulkhead on a 9g fighter. Also, weight goals for the C919 are nevertheless unremarkable.

 

[Deino]

But the way you listed it looked dishonest and biased against the J-20.

If that's what one wants to see, I guess it does.

I did some research on the gun as you suggested and got 92kg for the gun, 140-180kg for the feed (likely 140kg) plus 480 rounds and whatever the belt that holds the rounds weighs. I guess you got 232kg empty and trimmed the sig figs?

You have to do better than Wikipedia for the really good stuff.

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F/A-18 feed system has a capacity of 580 rounds, apart from being newer F-22 has 480 rounds so almost certainly going to be a bit lighter. No belt - the F-22 has a linkless feed (as do most of the newer aircraft fitted with the M61).

Another data point:

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Only 30 rounds more than F-22 and, lo and behold, a bit lighter (but even older).

 

[latenlazy]

Just to add that something else to consider with weight saving techniques is cost.

Often, the most cutting edge technology is not immediately applied to existing products because of cost considerations. Especially for the PLA, who has a reputation for penny pinching. Just look at AESA proliferation rates in the PLAAF and elsewhere as a good example of that in action.

In addition, fighters are finely balanced machines. It’s not as simple as replacing a part made with aluminium with the same part made from carbon fibre and calling it a day.

If you reduce the weight of a key component, then the weight distribution with your plane will change, and you will need to make other changes to compensate for that.

Often, those supplementary changes eats up a lot of the original weight saving from improved materials and adds a lot of costs and delays. That’s why mods to existing designs tend to be a lot more conservative and modest than what could be achieved with a new clean sheet design.

There are exceptions, for example if the design had the new parts and materials in mind from the start, in which case room would have been reserved, but more critically, weights would have been added and/or non-essential equipment temporarily not installed where necessary to simulate the weight and balance of the plane as if it had the ultimately intended materials and parts in place all along.

In which case, once the intended part/material becomes available, they could just unwind all the added weights and install any omitted equipment and sub in the new materials/parts to keep the balance and weight the same.

So my point is two-fold. Firstly, it is rare for cutting edge materials and manufacturing technology advancements to be fully applied to existing designs. So looking at the weight and performance gains achieved with existing designs is not really a good reflection of what could be achieved if those same materials and manufacturing techniques are applied to a new design that planned for those new materials and techniques and the weight savings and performance gains they would yield.

Secondly, just because we do not see the latest cutting edge manufacturing and materials technologies applied to existing military or commercial designs, that are far more price sensitive, does not necessarily mean a nation does not have the knowhow to make and use those cutting-edge materials and technologies if, as is the case with premiere 5th gen air dominance fighters like the F22 and J20, price is really not an issue.

That is also why we tend to see a big jump in performance between newly developed designs and existing designs modified with the latest tech even when the two programmes might be done by the same country/company and roughly the same time.

Exactly. A *key* aspect of advancing materials and process technologies is that they change the very principles of structural design. Structural design is an expression of the materials and manufacturing processes you select. You can't just take the materials and processes used in the 787 and stick them into a legacy design like the 777 design for example. You would have to go through an entirely new development process, which is what the 777X is, and even then using a legacy design as a starting template will impose limits to how much of the new materials and processes technologies you can employ.

 

[latenlazy]

I have since checked my hunch that vertical tail area on the J-20 isn't reduced as much compared to the F-22 as horizontal stabilizer (canard) area with a good beam photo and it was confirmed. Fin + strake area is scaled down to a factor of about 0.7, canard area to 0.6 - I applied the latter in my calculation though (i.e. I acted as thought he J-20 has somewhat smaller fins than it really does). So I don't think there's scope for crediting the J-20 with a greater weight reduction for empennage area than I already did.

You missed the point in that section of my comment...what I was saying was that even *if* the combined vertical tail and ventral strake areas were comparable to the F-22's vertical tails, they wouldn't occupy the same volume because as two separate pieces they can be made thinner owing to smaller structural load demands compared to a single piece with the same surface area (this is also true of the canards vs horizontal tails). Anyways, as I said earlier, it's a minor quibble.

No, excluding what the 3D printing industry as a whole *claims* to have achieved Read Sciaky's description of what they'd like customers to believe their machine is capable of and compare/contrast with the apparent experience in the field at Airbus. Perhaps it's too pessimistic an attitude, but I'm simply assuming the signal-to-noise ratio from the Chinese 3D printing industry is broadly the same as it has historically proven to be with their counterparts elsewhere.

Unless Sciaky is following the work of his Chinese counterparts closely it's hard to claim that he's also speaking for China's additive manufacturing industry (and given what he defined state of the art as, I get the impression he isn't). It won't be the first or last time establishment observers and participants in an industry from the West either misses or dismisses new developments in China. Nor do I think it's safe to assume that the signal to noise ratio for information is the same in the Chinese aerospace manufacturing industry, since in many cases new developments come from state owned firms which don't have as strong an incentive to inflate their capabilities. Most of their clients are often also state owned firms, which means they don't have to advertise as fiercely to persuade clients on the open market. Where they do, as new entrants their extraordinary claims must hold more water to overcome their reputation deficit relative to their Western peers.

Driving down density comes with serious compromises on certain aspects of the design (g-limit, fuel capacity, weapons bay size - that kind of stuff) though, as those demonstrators you mention quite conveniently exemplify. It's no accident that the production aircraft which grew out of them were all substantially heavier - the proof of concept airframes were without exception far from combat-capable at that weight. None carried anything like a full avionics suite, none were fitted with RAM treatments and the X-35 even lacked weapons bays as well as having a reduced fuel capacity - lots of air in there:

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Likewise, the YF-23 was much more of an empty shell than the YF-22 (it did have weapons bays but they were not functional whereas Lockheed actually testfired an AMRAAM etc.) - the manufacturer's own weight projections for the production aircraft put F-23 empty weight *higher*. Both these points reputedly contributed to the victory of the F-22, as it was judged more mature (its demonstrator was closer to a combat-capable aircraft) and lower cost (weight is a cost driver).

And I suggest as much, but my point wasn't that the J-20 can be as light as those demonstrator. My point was that if you make some tradeoffs and catch a few ingenuitive breaks a 15 tonne J-20 isn't inconceivable.

Actually the main attraction is time and cost.

No hostility intended either, but as I said before, I find the idea that the F-22 is overweight to the tune of several tons due to bulkheads which are thicker than what the load bearing requirements demand, simply because they can't machined any thinner, scarcely credible. Do you have a source which says that loud and clear? BTW, larger holes/openings (for instance the intake ducts) are incorporated into the forging before machining - the smaller one would not amount to machining so much as drilling.

I didn't say the F-22 was overweight because of bulkheads that are thicker than load bearing requirements demand. Nor did I say the F-22's titanium structures weren't as thin as is possible with milled forging. You brought up how you can mill things things thinner than before after all, not me. My main point was and continues to be that there's a limit to how thin you can make a shape by milling a forged billet of titanium because of the material's mechanical properties and the mechanical forces involved in the particular process. The argument isn't, after all, that the J-20 or J-31 might have lighter titanium bulkheads because they have more advanced milling machines and processes.

You design your structures around both what the load bearing demands are and what is possible with the materials and process technologies that you have on hand. If your process technology or materials advance, you can achieve the same load demands with less weight (as I said in a reply to plawolf changes in materials and process technologies change the principle of design), sometimes by employing different principles that you couldn't use before.

Also, not to be pedantic but machining/milling includes drilling...

I doubt billets for bulkheads would undergo processing and forging for months at astronomical cost just to endow them with properties which are not actually required...

Did I say that? No, I did not.

For one, just because something was made with a forging process that does not mean it was made with the specific forging process that yields the highest material strength possible with forging. There isn't just one forging process. You fit the material processing based the particular material properties you need (within the confines of your project resources).

Second, there are always multiple ways to meet some mechanical load requirement. Structural shape, mating and placement of different materials, microstructural features, etc. all work as a holistic cohesive unit. If it was just about material strength there wouldn't ever be any need for mechanical load analysis. Maybe 3D printed titanium can't achieve the same strength level as the strongest you can achieve through forging, but maybe it allows for more efficient shapes than what you can achieve with milling, so your 3D printed structure doesn't have to match the strength of the strongest forged billet. Just because you can get a some result one way that doesn't mean it's the only way and thus we should assume it's unquestionably the best you can hope to achieve. Otherwise, what's the point of new process innovations?

People jumping to conclusions? It does happen For that matter, when the 15t figure was mentioned are we certain it refered to OEW (as in operational) and not bare airframe weight (without engines & some equipment - 15t would be perfectly believable for that)? Or it's the weight of #2001/2002 and they were largely empty demonstrators?

The 15 tonne figure was mentioned in comparison to the F-22's 19 tonne empty weight. Regardless of the reliability of the source, the implications of the claim was pretty clear.

Has there been specific confirmation that Chinese fighters not only use 3D printed parts in general (things like jobjed's pipe fitting - perfectly credible and still a boon from a cost and time perspective) but actual bulkheads?

No one jumped to any conclusions about at least one of China's stealth planes using 3D printed bulkheads. The claim by industry was specific and clear on that.

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I mean, what makes a Chinese University's claim to have printed a bulkhead different to Sciaky's claim to have printed a spar? With the latter, not only was Airbus apparently unhappy with the result, they were unhappy enough to turn to a competely different partner for further development. Just because the makers of a 3D printer (and it matters not where they hail from) says so obviously doesn't mean it's true - I'd just be rather more inclined to believe claims from an actual airframer (i.e. the customer)

Because unlike your Airbus example the claim is made by institutions and firms that are arms and subsidiaries of the same conglomerate that is also producing the planes the parts are said to be used in (and the claimants provided visual evidence in their press )? As I mentioned before, you can't just assume the information environment works the same in China as it does in Western industry. If that were the case, the stuff we have to do in this forum to get updates and new information would be completely unnecessary.

Like I said earlier, you can take it or leave it, but the claims are not ambiguous regardless of how incredulous you may find them.

That's more like it - thanks! Where on the C919 does that beam go though? A floor beam for example would say nothing about the applicability of the manufacturing process to a more highly-loaded part like a bulkhead on a 9g fighter. Also, weight goals for the C919 are nevertheless unremarkable.

"The Northwestern Polytechnical University of China is also making five meter-long titanium wing beams for the C919 passenger plane, which is scheduled to be put into commercial operation in 2016."

 

[latenlazy]

Second, there are always multiple ways to meet some mechanical load requirement. Structural shape, mating and placement of different materials, microstructural features, etc. all work as a holistic cohesive unit. If it was just about material strength there wouldn't ever be any need for mechanical load analysis. Maybe 3D printed titanium can't achieve the same strength level as the strongest you can achieve through forging, but maybe it allows for more efficient shapes than what you can achieve with milling, so your 3D printed structure doesn't have to match the strength of the strongest forged billet. Just because you can get a some result one way that doesn't mean it's the only way and thus we should assume it's unquestionably the best you can hope to achieve. Otherwise, what's the point of new process innovations?

I couldn't edit my comment to include the following article, but it gets to my point about how there's a lot more going on in the engineering of structural design and weight saving techniques than how strong the materials you use are.

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EDIT:
Also forgot to address this particular point.

Also, weight goals for the C919 are nevertheless unremarkable.

Everyone else has already touched on how the C919 isn't exactly a good benchmark for what is state of the art in China, so I'll leave that angle alone, but consider that it's entirely reasonable for the C919 to have unremarkable weight goals and still employ remarkable weight savings technologies. If, for example, China's composite manufacturing capabilities aren't nearly as advanced as other countries (and it seems pretty evident that they aren't), they would need some other method to reach comparable weight goals as their market competition.

 

[Inst]

We actually have a nice range of weight estimates for the J-20, from the 15 tons of fanboy speculation, to Trident's 21 tons, which is pretty reasonable based on the F-22 airframe.

Thing is, we have no confirmed evidence of empty weight; we do have a claim of 15 tons in the Chinese media, but for all we know, it could be fanboy bluster or the J-20 without RAM, which adds around 4 tons to the F-22, going from the YF-22 to the F-22 production model.

However, if we point to evidence, check this out:

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Note that this is produced by an AVIC company, i.e, it's within the same conglomerate as Chengdu. Moreover, look at the titanium parts built; they're clearly designed for the J-20. So we can assume that the J-20 is using at least some 3D-printed Titanium parts.

The F-22 has about 39% titanium by weight, meaning that it's 7683 kg of titanium. Using a 40% reduction, we can shave off 3 tons of weight off the J-20. My own estimate of the J-20's weight, given that it does not use TVC, which adds 800 kg to the weight, and using a 8% volume magnification ratio, you get 20 tons on the J-20. Then if the J-20 has the same basic titanium intensity as the F-22, weight reduction shaves off 3 tons, putting it down to 17 tons. Assuming it has greater quantities of titanium than the F-22, due to the lower weight and cost relative to traditional forged titanium, we get 16 tons of empty weight by shaving off the 19% titanium in the F-22, then scaling it up.

Of course, all of this is just speculation due to the lack of concrete information. But I think I've shown that an empty weight of 16 to 17 tons is plausible, and that 15 tons is believable if Chinese official sources release that empty weight.

 

[Inst]

Also, let me point out something rather weird:

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This is a Western estimate of the J-20's weight, so we can assume it does not include or consider radical new technologies. It works off 21.5m length with 12.98m wingspan, but seems to include the probe, so actual ratios are approximately 20*13. The estimated empty weight is 34572.2 pounds, or 15800 kg, putting it squarely around the 16000 kg of lower-end estimations.

In the X-35 / F-35 case, the airframe grew about 32% in weight as it moved from prototype to production model. In the YF-22 / F-22 case, the airframe grew about the same percentage. From the YF-17 to the F-18, there was only a 10% weight increase, and what's more, the wingspan increased by about 25%.

So we can make a rough guess that it's the RAM that results in the weight gain, and that without novel manufacturing technologies, the J-20 will weigh around 21.5 tons.

===

At this point, I think it's plausible to believe that the fanboy claim is at least partially correct: the aircraft weighs around 15 tons either with or without RAM. If it is without RAM, the aircraft will likely weigh around 20 tons once RAM is added.

 

[Inst]

I seem to have lost my ability to edit threads, so let me triple post.

Given the information we have available; i.e, that RAM makes up roughly 25% of a modern stealth aircraft's weight, there are a few hypotheses we can consider.

1. The fanboy claim has zero credence. This is easy to work with, and we can just assign whatever weight to the J-20 we'd like to estimate.

2. The fanboy claim is referring to the J-20 without RAM. This is also easy to conclude, since we'd need only very slight weight reductions from 3D-printed titanium to achieve this figure.

3. The fanboy claim is actually correct, which implies interesting possibilities.

3a. First, either there's extremely extensive weight reduction in terms of material, so much so that about 33% of the aircraft's weight without RAM is nixed. This is highly implausible, especially since the engine weight contributes around 3 tons of weight, meaning that the aircraft would have to lose almost half its weight.

3b i. There is some level of basic weight reduction, so the J-20 without RAM is lighter, but the J-20 opts not to incorporate RAM into its airframe. This fits with the fact that the J-20 does not seem to need temperature-controlled hangars to protect its RAM.

3b ii. Assuming the same weight reduction as in 3b i, the J-20 is lighter, but the J-20 uses RAM less extensively. The J-20, after all, is a -20 dBsm design without RAM, so if it can't win a stealth contest, why try? Reducing the amount of RAM employed reduces aircraft weight in an aircraft that needs to be maneuverable in order to compete, and allows the J-20 to fly more hours by reducing maintenance time.

3b iii. Now we get to the really interesting stuff. The J-20 was developed a couple of years later than the F-35, and it's possible Chinese RAM is more advanced than American RAM. The fact that the aircraft does not seem to need temperature control implies that Chinese RAM is more advanced in at least one area. Is it possible that the Chinese have developed new RAM that's significantly lighter than the current Western state of the art?

That said, I find hypothesis 2 most likely, and 3b iii most fascinating. I know the Chinese developed some kind of frequency-dependent nano-material for radar absorbency, but have the Chinese discovered much lighter, but effectve, RAM?

 

[guanyu158]

You should probably take this with a ton of salt considering the fact that Zhang Zhaozhong was responsible for this analysis. Although he formerly served as a rear admiral in the PLAN, there is little to no credence to many of his wild theories, which include:

1) Using kelp farms to tangle the propellers of foreign submarines in the South China Sea.
2) PM 2.5 can minimize the effectiveness of American laser weapons.
3) The J-20 (before it came out) was nothing more than a stealth version of the J-10.

I didn't know about the the third item. But it is clear that the first 2 items are misinterpretation of his words. It was deliberately twisted by certain people.

 

[Deino]

Having researched the question of the Chinese bulkhead and wing beam a bit more, I have to admit that I'm on the fence now - I might be prepared to accept that they are 3D printed and ready for use in production aircraft. What I continue to doubt is that there is a weight reduction, I'll explain below (though most of the points I have made before in one post or another).

Unless Sciaky is following the work of his Chinese counterparts closely it's hard to claim that he's also speaking for China's additive manufacturing industry (and given what he defined state of the art as, I get the impression he isn't). It won't be the first or last time establishment observers and participants in an industry from the West either misses or dismisses new developments in China.

Sciaky is neither a he or a she, they are a US-based manufacturer of metal 3D printers Their biggest machine can handle parts about the same size as the Chinese samples we've been discussing and Airbus has been playing around with a smaller variant based on the same technology. I've since learned that Airbus have also been cooperating with the Chinese Uni since 2014, perhaps you were aware of this and that's what confused you?

Regarding the accuracy of Western assessments of Chinese technology you are barking up the wrong tree - I don't disagree, hence my emphasis on the fact that I am expressly NOT holding China's 3D printer industry to a different standard than anybody else's. I also concur that China is at the forefront of the additive manufacturing race (their big machine beat Sciaky's by two years, closed loop control system and all!), I am just skeptical about them being THAT far ahead of the pack.

You brought up how you can mill things things thinner than before after all, not me. My main point was and continues to be that there's a limit to how thin you can make a shape by milling a forged billet of titanium because of the material's mechanical properties and the mechanical forces involved in the particular process.

I didn't - I made the point that for a highly loaded part of straightforward shape such as a fighter bulkhead, it will be load bearing requirements which drive part thickness, not manufacturing capability (and that this has been the case for a while). So unless you adopt a novel approach to shaping (e.g. something hollow or an integrated truss structure), using 3D printing to make it will drastically drive down cost and manufacturing time but hardly affect weight at all. A solid piece of Xcm³ of titanium is going to weigh Ykg, no matter how it came to be that shape.

For one, just because something was made with a forging process that does not mean it was made with the specific forging process that yields the highest material strength possible with forging. There isn't just one forging process. You fit the material processing based the particular material properties you need (within the confines of your project resources).

We're not debating "something" though, we're discussing fighter bulkheads - and it's a fairly safe bet you'll want the best material properties obtainable for this particular application.

Second, there are always multiple ways to meet some mechanical load requirement. Structural shape, mating and placement of different materials, microstructural features, etc. all work as a holistic cohesive unit. If it was just about material strength there wouldn't ever be any need for mechanical load analysis. Maybe 3D printed titanium can't achieve the same strength level as the strongest you can achieve through forging, but maybe it allows for more efficient shapes than what you can achieve with milling, so your 3D printed structure doesn't have to match the strength of the strongest forged billet.

Absolutely true (and I have been saying things to that effect all along), but for this to be relevant here it amounts to you claiming that the bulkhead sample you've shown is of a geometry which could not be made by forging and machining. I would roundly disagree with that - I don't see anything unconventional there which would support such an assessment. And the microstructures part after all is precisely what I mean by material properties - that aspect continues to favour forgings currently.

I couldn't edit my comment to include the following article, but it gets to my point about how there's a lot more going on in the engineering of structural design and weight saving techniques than how strong the materials you use are.

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You are making my point Do those structures look like these to you:

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So where would the weight saving over a machined forging be coming from in the above examples, if we accept that they're 3D printed? Same material, geometry which is achievable with traditional processes, likely somewhat inferior material properties which might require greater thickness in places than the conventional analogue to bear the same load. There's no question that 3D printing the conventionally shaped parts would be dramatically faster and less expensive (factors important enough that they may well clinch the deal all by themselves), but lighter?

Another case in point:

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Handsome weight saving, but only obtainable by completely rethinking the shape.

On a different note:

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LOL! Talk about being blinkered - on the General Dynamics web site where I found the F-16 gun data there is actually a page for the F-22 gun system which I somehow failed to notice.

So a total of 170kg (empty feed + gun), but on the other hand EOTS weight is actually a bit less than 100kg:

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Nonetheless, it shows that by applying a bit of common sense and technical judgement you can get the general trend right even without having the exact figures, and the two errors (such as the relevance of a couple dozen kg one way or the other is, for a ~21t estimate) do cancel out to a large degree.