Chinese Hypersonic Developments (HGVs/HCMs)

latenlazy said:

You don’t seem to know anything about the specific challenges of aerodynamic and propulsion design for hypersonics. There are lots of chaotic and turbulent flow conditions that are extremely difficult to observe, predict, and model as you lose assumptions of smooth continuous flow to errant shockwaves in the hypersonic regime, and as the high heat environment introduces plasma dynamics into the tangle of additional factors you have to account for. The ability to incorporate those complex factors into your standard finite element analysis becomes very difficult and esoteric in the face of those conditions. As you add complexity of elements into your analysis you start to hit computational constraints over what you can model, and thus what solutions you can find for a set of conditions, which is why supercomputers have become so essential to advancing hypersonic research. “AI”, specifically neural nets, are actually very promising solution generating tools for getting around these challenges, because neural nets are actually better described as a mathematical method to efficiently map and find solutions in complex mathematical topographies. They offer a much more thorough and efficient search of a solution space than traditional computation solutions do. This will matter significantly for both coming up with better mechanical design, and for defining control laws for both flight and propulsion systems. So depending on what you mean by “design the entire projectile”, the claim itself is not that far out of a leap. It’s not as simple as taking a picture and letting your neural net do all the work, but the specific elements of a solution can be increasingly outsourced to neural nets.

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Hyper said:

What you are saying is correct in that ai is helpful. But if someone says that the ai will do all the design work for you then you know they are not telling the truth. Both human and ai input are required.

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BoraTas said:

USAF's weapon claims Mach 20 top speed and 1600 km max range. Compare this to Mach 10 DF-17 which achieves a 2500 km range. A few possibilities:
1- USAF's weapon has a horrible lift to drag ratio, resulting in a short range.
2- It can't do normal glide so it has to perform skip glide. This involves constant altitude changes meaning horrible range.
3- It uses a lower trajectory than the DF-17 which apparently uses the 40-55 km range. This would mean a superior weapon but I don't see the US shooting for this at its first hypersonic. Mach 20 combined with a lower trajectory means incredible heat.

I think it is a combination of these. A top speed of Mach 20 would require a huge rocket in any case and making the weapon light enough would require a lot of innovations. Interestingly, most failures we hear so far are rocket motor related.

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enroger said:

The disparity between speed and range is way too much, it would literally needs to have negative L/D to suck this bad.... I think mach 20 and 1600km range probably refer to different programs, or the figure is just made up

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AssassinsMace said:

Mach 20 is propaganda since the US has never achieved it with their hypersonic program. It's for US fanboys locking their bedroom doors so mommy doesn't accidentally walk into their room. When reports of Chinese successes in their hypersonic program surfaced, back then the naysayers said two things. One was China didn't have a hypersonic wave rider and the other was Chinese hypersonic missiles don't even go as fast as Mach 20 like American ones do. That only counts if you can include what's said on paper because the US doesn't have that either.

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gelgoog said:

Any of these boost glide vehicles won't be traveling at Mach 20 when it gets close to the target.
At best it will be peak speed at high altitude.

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ChongqingHotPot92 said:

Then China would have to triple, even quadruple its current IRBM force size. China currently has roughly 200 DF-26 launchers (roughly the size of US Army's Pershing-II force during the 80s) and very small numbers of DF-17 and DF-100 launchers. The DF-26 forces have to deal with both India and the Pacific theater, and 200 missiles aren't enough to destroy every single facility on Guam, not to mention a significant portion of the force have to be reserved to deter India just in case New Delhi were to take advantage of contingencies in the Pacific. Also, the US military knows where these DF-26 forces are located, as least before they are dispersed to various launch sites during a contingency. In this sense, if you want to blow up the entire second island chain in addition to the first, you really have to triple or quadruple your IRBM and hypersonic forces (assuming a portion of these forces would be taken out before they even launch). It take time to train missileers to operate and maintain complex machines like the DF-26 and DF-17. They are also parts of complex a battle network working in conjunction with the PLA Navy and PLAAF. It is not that easy to expand. Finally, those runways on Guam could be repair within a few hours after a saturation strike. You definitely need more than 200 Df-26s, DF-17s, and DF-100s to sustain the strikes to keep the bases on the second island chain from becoming operational. In general, the current PLARF IRBM force is inadequate in sustaining a prolonged war against US forces on the 2nd island chain.

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Hyper said:

Df

-zf is not mach 20.

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