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Chinese Hypersonic Developments (HGVs/HCMs)
- Thread starter A.Man
- Start date
escobar
Brigadier
Interesting comparison between HCM vs HGV.
- HGV need more exotic materials for thermal-protection to handle the thermal environments
- Materials and thermal management are the biggest drivers of cost in these vehicles
- Heat is less of a factor for air-breathing systems because they fly at lower speeds.
- Air-breathing propulsion is lower risk because it is a less complex system
- Air-breathing weapons fly in the upper reaches of the atmosphere, but don’t go outside the atmosphere
- Air-breathers don’t fly as high or as fast as boost-glide systems. Therefore they generate less heat and can rely on more conventional materials such as metals for their airframe.
- Air-breathers tend to be more tactical than strategic. That’s important because it means they can be manufactured using lower-cost, higher-yield methods. Customers can get several air-breathers for the price of one boost-glide.
No surprises at all. HGV tends to be a much higher tech system than HCM. Anyone can put together some boosted ramjet or scramjet (harder) fridge sized HCM. The only hard part is keeping the scramjet lit. Only Russia China and the US are known to have been able to sustain an airbreathing engine for useful amounts of time. India claims it does but these guys rent second rate hypersonic tunnels from Israel to do some limited work. It's a joke.
HGV is where the intense thermodynamics and aerodynamics is at. Without non stop numbers crunching with supercomputers and constant use of hypersonic wind tunnels it's jist not even remotely possible to create a HGV. The Indians going to trial and error their way to this? Lol. Not even the US has a working HGV. Russia is unknown but they claim avangard is HGV. Only known HGV so far is df-zf.
HGV is where the intense thermodynamics and aerodynamics is at. Without non stop numbers crunching with supercomputers and constant use of hypersonic wind tunnels it's jist not even remotely possible to create a HGV. The Indians going to trial and error their way to this? Lol. Not even the US has a working HGV. Russia is unknown but they claim avangard is HGV. Only known HGV so far is df-zf.
There's a significant material science aspect to the engine, not just staying lit: the US faced a 7 minute limit for a number of years where materials would fail in the engine/airframe of scramjet powered aircraft. The materials in a scramjet are rather different than an HGV.
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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plawolf
Lieutenant General
That’s like saying a conventional hard drive is harder to make than a solid state hard drive because conventional have more moving parts.
very different comparison because a surfboard and motor boat function in the same fluid dynamic regime but HGV and HCM do not. HGV functions in low pressure, high altitude, high temperature regime. This requires blunt body aerodynamics and refractory materials. HCM functions in a temperature and pressure regime where wing aerodynamics and standard metal materials still works.
the comparison would be motor boat vs. sea floor submersible. motor boat has engine, submersible doesn't, but submersible functions in a totally different and much more extreme fluid dynamic regime.