Chinese Hypersonic Developments (HGVs/HCMs)

BoraTas

BoraTas

Major
Registered Member
enroger said:
I'm baffled by the TengYun uses hydrogen peroxide claim, it has low isp as monopropellant, also not sure where they'd use it in a combined cycle engine, I assume the ramjet/scramjet part would use something like hydrogen or methane....

Otherwise it's a great idea to build something like a hypersonic yeeter
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I think it would be used as an oxidizer rather than as a monopropellant. Kerosene and H2O2 is a lower performance combination compared to the combination of kerosene and liquid oxygen but it is room temperature storable. It is a better combination in terms of availability
 
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gelgoog

Lieutenant General
Registered Member
No. Kerosene and H2O2 has roughly the same theoretical performance as Kerosene and O2 (i.e. LOX).

The problem is it is difficult to get HTP i.e. H2O2 at 90% purity. And it naturally decays to H2O and O2 if you do not take special precautions. Getting LOX is trivial in comparison and a lot cheaper. About the same price as milk. And the density of both is about the same.

You basically liquefy air and filter it to make LOX. The equipment is commonly available and can be found everywhere from welding shops to hospitals. H2O2 requires a chemical reaction, and then several high energy steps distilling the low purity H2O2 until you get it to 90%. The largest commercial application of H2O2 is to disinfect and clean food containers. But so called "food grade" H2O2 is only 35% purity. Trying to buy 90% H2O2 will get you funny looks since the only major user is basically the military for naval torpedos.

In theory it is easier to handle and it takes less heavy tanks to store H2O2 than LOX. But in practice because of all these issues most people don't bother.
 
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BoraTas

BoraTas

Major
Registered Member
gelgoog said:
No. Kerosene and H2O2 has roughly the same theoretical performance as Kerosene and O2 (i.e. LOX).

The problem is it is difficult to get HTP i.e. H2O2 at 90% purity. And it naturally decays to H2O and O2 if you do not take special precautions. Getting LOX is trivial in comparison and a lot cheaper. About the same price as milk. And the density of both is about the same.

You basically liquefy air and filter it to make LOX. The equipment is commonly available and can be found everywhere from welding shops to hospitals. H2O2 requires a chemical reaction, and then several high energy steps distilling the low purity H2O2 until you get it to 90%. The largest commercial application of H2O2 is to disinfect and clean food containers. But so called "food grade" H2O2 is only 35% purity. Trying to buy 90% H2O2 will get you funny looks since the only major user is basically the military for naval torpedos.

In theory it is easier to handle and it takes less heavy tanks to store H2O2 than LOX. But in practice because of all these issues most people don't bother.
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All resources I looked at state that LOX has slightly higher performance compared to high-test peroxide. What's more, I found a document about a similar project from NASA.
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You can read it if you want. Their conclusion is in a relatively low delta V vehicle little extra performance of LOX was not crucial and H202 had advantages in simplicity and safety.

"Summary and Conclusions


A trade study considering two alternate oxidizers, liquid oxygen or 90% hydrogen peroxide, for a rocket based combined cycle demonstrator vehicle was completed. This trade study considered the overall system performance from both a technical and programmatic viewpoint, to select the lowest risk solution. Given the limited energy requirement (delta V) of the demonstrator vehicle (Mach 0.7 to 7), the higher density and mass ratio of 90% hydrogen peroxide yielded similar vehicle performance when compared to LOX. Additionally, hydrogen peroxide provided system simplification, increased flight safety and packaging advantages. After consideration of the technical and programmatic details, 90% hydrogen peroxide was selected over liquid oxygen for use in the ISTAR program."
 
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gelgoog

Lieutenant General
Registered Member
The density difference is minor. Slightly more density for H2O2 (1.387 vs 1.14) but nearly irrelevant. The major advantage is the oxidizer tank would be lighter since you need no insulation. The talk H2O2 is safer than LOX is bollocks. HTP can be dangerous to handle if you do not know what you are doing. There were several accidents with H2O2 in the late WW2 period when they were trying to use it in submarines. After WW2 when it was used in torpedos there were several fatalities fueling torpedos up in the factory.
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The danger with handling HTP is a big reason why you seldom see it used in those applications anymore. All it takes is some metal flakes in the fuel tank leftover from the milling process that no one noticed, and you get a rampant fuel decomposition, and explosive compression with possible ignition event.

I doubt LOX has any Isp advantage in real terms over HTP since if you look at it, the HTP is just H2 and O2. The major issue with H2O2 is that they typically decompose it with a catalyst, I think with a platinum catalyst, before ignition with Kerosene and that takes more weight than using an hypergolic starter cartridge which is what they typically use with LOX.
 
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