Chinese Hypersonic Developments (HGVs/HCMs)

ougoah said:

In most ways HCM isn't harder to make. In the domain of propulsion, the HCM is harder to make because the HGV can have no engine. HGV is harder to make because it requires aerodynamics that HCM don't necessarily use. There are projects combining the two to make what would essentially be an engine propelled HGV. If China's 2021 flight, that traveled basically the distance of the globe, is a HCM in the sense that it is an air breathing engine powered hypersonic vehicle, it may have also made use of aerodynamics. So far apart from that particular Chinese vehicle, there is no other HGV with anywhere close to global range and no HCM with that range either. What's hard about HGV is creating a waverider effect and so far only China has been able to do this for certain (Russia's Avangard is claimed to be capable of it and in active service). By certain I mean the US says they've been watching "hundreds" of Chinese hypersonic test flights over the years and China admits it. Okay China has many hypersonic programs of various types, applications etc and most tests are probably NOT exclusively HGV types. They even displayed the DF-ZF. Anyone can copy the outward shaping but the difficulty is in combining flight controls, materials, and the very specific shaping. All factors incl even internal weight distribution and CoG and so on. They can see the shape and even size for free.

Your analogy is not accurate. In your analogy, this surfboard is so hard to make that the US has yet to make it work and yet the US has been making scramjets for over a decade. Each simply have their own unique challenges. HCM is easier in the sense that anyone can strap a ramjet onto some frame, boost that to well over Mach 5 and let the ramjet or scramjet power it for x minutes (in India's case around 20 seconds if they're lucky since that's their ground test record) and call it a day. The DF-100 is engine propelled and been in service for years. Tsirkon been in service for some time and is an engine powered HCM. US has been testing HCM of their own for a while too and "academically" for over a decade.

Clearly one is easier than the other. So far only China has actually shown, flown, and allowed people to see one of China's HGVs. As for whatever China flew in 2021, it was in the atmosphere most of the time. Some of the American military leadership called it "breaking the laws of physics" because they can't figure out how the Chinese managed to fly a hypersonic vehicle for so long and so fast (avg speed around Mach 16). Without being engine powered for at least a part of its propulsion, how else could this Chinese hypersonic vehicle manage this range within the atmosphere. Clearly within atmosphere otherwise this wouldn't even be news because plenty of satellites are hypersonic relative to a point on the earth. The only way something "breaks the laws of physics" (the expression not the actual reality!) is because they are not sure how they sustained the glide/waveriding for so long at that speed or how the Chinese combined engine powered craft with aerodynamic lift and control in the way that a waveriding HGV "propels" itself using hypersonic shockwaves.

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gelgoog said:

You guys seem to think the thermal environment of an HCM is easier than that of a HGV. You are completely wrong. It is one thing to make materials to last a couple minutes at reentry temperatures or to make several short bounces off the Earth's atmosphere for a HGV. You can use cheap readily available ablative materials for this. The technology is known since the 1960s. It is quite another thing to make a HCM which needs to be soaked at high temperatures in an environment full of high temperature oxygen gas. Which is corrosive and eats away metal. There is one reason why all those scramjet tests you see in the US failed to significantly speed up to higher speeds than the ones provided by the initial boost rocket, and made short flights afterwards which are not enough for a practical weapon. And the DF-100 is a ramjet, not a scramjet. Not same thing. The Russians also have had the P-800 Oniks for a long time already.

Just think about it. You are comparing something which does a prolonged high speed flight inside the atmosphere to one which does a flight outside the atmosphere. It is like you are saying it is easier to make a Mach 1 vehicle that travels inside the ocean than a Mach 2 vehicle that flies in the atmosphere. So which one is harder to do? And guess why it is harder? The drag and turbulence are totally different.

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Quickie said:

I recall watching a youtube video that mentioned the DF-ZF having to be rocket-powered in the almost airless upper atmosphere in order to be boosted back to full working speed before reverting back to the wave-riding part of the flight.

In this way, the DF-ZF is already essentially a powered HGV during the boosting and re-boosting part of the flight.

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ougoah said:

Not sure what you mean but DF-ZF being a boost glide system and likely a waverider means it is propelled by shockwaves. Booster rockets aren't counted as engine propulsion in the sense of a "HCM" engine which would have to be air breathing for it to be considered a "cruise missile".

Waveriders and gliders are harder than simply making something go fast. Heaps of ballistic missiles are hypersonic. Turkey, Iran, India, France, UK, Pakistan, North Korea all have hypersonic weapons in the sense that they have ballistic missiles that are capable of > Mach 5. The only challenge in powering a hypersonic HCM is the air breathing propulsion part. As F&U posted earlier, the dynamics of control and using hypersonic shockwaves to push the vehicle is something so far only China has certainly managed to do and put into service. The US has been test flying but has yet to put a glider/waverider into service. They want to combine waverider with scramjet engine. Russia's Zircon may be a waverider + scramjet powered and their Avangard is probably a HGV without an engine since it's advertised by the Russians as an intercontinental nuclear strike platform (minimal details provided on the boost glide parameters ie how far away does HGV payload release etc).

India says they've been doing test flights but all the major observers with constellations of sea and space based sensors (really just China and US at this point) think otherwise. In China's case, I think there are some land based OTH radars pointed at Indian Ocean (not for India but for USN SSBN threat). It's not clear if sea and land based sensors can pick up on the flights but US certainly has lots of presence in Indian Ocean and both US and China have by far the most space based sensor networks. They did some flight testing of their scramjet but unless they have dozens of breakthroughs, even making a scramjet that works well enough for a weapon is difficult. For China's various military and space launch programs, China has gotten past the basic scramjet phase long ago and the more recent leaks show oblique detonation scramjet, whatever that Tsinghua test engine is (from a few months ago), rotating detonation engine, at least two types of combined cycle engines, and of course run of the mill scramjet engines. Chinese hint that other technologies are in use for hypersonic programs with the laser induced cavitation like method to manage heat.

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sferrin said:

A scramjet is WAY harder. It has to do everything the glider does as well as deal with internal heating and keep the engine running.

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ougoah said:

An air breathing glider/waverider would indeed be hardest but not all air breathing hypersonics are gliders/waveriders as far as we know. For example DF-100 probably isn't a glider/waverider but it is air breathing. Glider designs vary in effectiveness in their lift-drag anyway. Creating a working engine is extremely challenging though and boost glide vehicles don't even need to deal with that problem. However these are separate problems so I guess it is kind of pointless to say which is harder. It's like arguing which is harder to develop an engine or a transmission gearbox. Different challenges. But point is some air breathers don't need anywhere near as much aerodynamic work while some gliders that aren't engine propelled don't need to even think about the scramjet/propulsion problem.

The hardest is indeed combining the two.

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Hyper said:

You mean something like a waverider ( x-51, starry sky etc ).

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ougoah said:

Not sure what you mean with this.

In any case, do we know that DF-100 or Starry Sky project are waveriders? They don't look like waveriders but there was an image from a while ago showing a dozen or so hypersonic designs from a Chinese paper or leaked conference slide?

Does anyone have that image saved. I recall it having many DF-ZF looking "winged/fuselage" vehicles and many symmetric conical shaped vehicles as well. Basically a bunch of "proposed and evaluated designs" in something like a 5x5 arrangement against a white background.

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