China's Space Program Thread II

[taxiya]

There are other explosives than RDX. I have heard people talking about possible use of CL-20 in solid rockets like a decade ago.

That is probably the one coming after N-15, it was called the new generation propellent in the 2007 article. Specific impulse by density is more than 5% higher than N-15.

继N-15／N-15B推进剂研制成功后，我院在“十五”、“十一五”期间加大了新型高能推进剂研制步伐。该推进剂密度比冲较N-15推进剂又提高了5％以上，比冲也有明显提高。同时该推进剂具有较高的燃速和优异的燃烧效率。“十一五”中期，计划进行缩比发动机试车，该推进剂最终要用于未来战略导弹III级发动机上。

Although this paper did not say CL-20, I have found other papers studying CL-20 based solid motor using the name 新型高能推进剂.

 

[Helius]

[snip]


My last try, this is what I highlighted.

View attachment 100838
I see Adhesive and Plasticizer. Which one indicates that N15 is polybutadiene or nitroglycerin based? If I understand you right, the type decides whether it is a NEPE like or HTPB type, right?

The HTPB is in the "adhesive" category. It's the binding agent that 'binds' the solid fuel mixture i.e. AP, Al, RDX together in this instance.

It seems to me what you're really arguing is that they don't explicitly label the binding agent as 'HTPB', and so that alone gives you doubt it isn't even HTPB at all, even though the entirety of their thesis revolves around the testing of HTPB-based propellants, not NEPE or other propellant types.

What they've done is they've come up with a model that's domestically developed that targets specifically the N15, also domestically developed, for its elasticity and tensile strength under stress, so as to prove this model of theirs provides accurate results. If it was any other fuel type the model would be different and they wouldn't base it on HTPB to begin with.

You say N15 is equivalent to NEPE, maybe you should question why they didn't adapt an NEPE test for their paper?

Anyway, if you wish to remain unconvinced that's your prerogative. You're free to agree to disagree. Several pages worth of discussion on which glue is which is enough for me for the day.

 

[taxiya]

I will save the time of all of us by clearing up what I was asking/arguing without going around any further, so I will skip the rest of your post.

It seems to me what you're really arguing is that they don't explicitly label the binding agent as 'HTPB', and so that alone gives you doubt it isn't even HTPB at all,

I am not arguing " it isn't even HTPB at all". I was questioning what in the thesis constitutes "it is HTPB" which is neither a deny nor an acceptance of what it really is.

even though the entirety of their thesis revolves around the testing of HTPB-based propellants, not NEPE or other propellant types.

This is an assertion from you that I could not get by reading the paper, therefor my question all the time.

You gave me the impression that you somehow know N-15 is HTPB based, that's it. Other people like me must take it as a fact even if we have no way to reach the same conclusion like yourself. In the mean time, you could not or would not present a reason other than "because I said so".

You say N15 is equivalent to NEPE, maybe you should question why they didn't adapt an NEPE test for their paper?

I said N-15 is equivalent in performance to NEPE. Since China's only other existing SRB is HTPB based, how could they derive from something they did not have? You can ask the Americans "why didn't they adapt NEPE test regime when they developed their NEPE?"

 

[by78]

More images of Taikonauts entering the Mengtian module for the first time.

 

[by78]

Planned rockets and spaceplane of Space Pioneer/Tiang Bing Technology (天兵科技). Awfully ambitious.

TL-3, the second-generation re-usable medium-sized low-cost commercial launch rocket, two-stage Lox/Kerosene configuration, total length 70m, body diameter 3.8m, fairing diameter 4.2m, total weight 570t, LEO capacity 17t , 500km SSO capacity 14t.

TL-3H heavy lift for lunar landing, two and a half stage common core Lox/Kerosene configuration, total length 85.2m, rocket body diameter 3.8m, fairing diameter 5.2m, total weight 1742t, LEO capacity 68t, 500km SSO capacity 42t.

TL-3M manned intercontinental transport spacecraft, to be launched by the TL-3 rocket, two-stage configuration, 67m in total length, 11m in manned cabin length, rocket body diameter 3.8m, 580t in total weight, 50t LEO capacity, 14000km intercontinental transport capacity 30t or 100 passengers.

 

[davidau]

More images of Taikonauts entering the Mengtian module for the first time.

Thanks for the images and also use the right term Taikonauts. People should use the term China Space Station or China's Space Station, do you argee?

 

[Quickie]

I'm well aware of the formula(s/e). As I said, to get a rudimentary m-dot you're missing at least 2 metrics, namely the volume of the booster itself, which we don't know, and the density of the propellant, which we also don't know.

Burn time alone won't give you mass flow rate to infer specific impulse. So I'm not sure what assumptions you're placing on those two values to arrive at whatever mass flow rate you ended up with that then gave you a 383s Isp.

You won't have to know the volume of the booster and density of propellant and the such of that. The 150 tons of propellant took 115 seconds to burn through which would give you an idea of the propellant burn rate (the equivalent to the expended fuel mass flow rate for a liquid rocket engine).

Obviously, the real problem is what kind of methods to determine the actual thrust and burn rate of the solid rocket motor and how they vary throughout the test.

 

[Helius]

You won't have to know the volume of the booster and density of propellant and the such of that. The 150 tons of propellant took 115 seconds to burn through which would give you an idea of the propellant burn rate (the equivalent to the expended fuel mass flow rate for a liquid rocket engine).

Obviously, the real problem is what kind of methods to determine the actual thrust and burn rate of the solid rocket motor and how they vary throughout the test.

the equivalent to the expended fuel mass flow rate for a liquid rocket engine

Yeah, that's what I thought gave you such a high Isp. Without fuel density it will give you skewed results since we're talking about solid fuels, not liquids, specifically their efficiency relative to thrust, hence the whole point of specific impulse.

Mass flow rate isn't the same as fuel burn rate. The viscosity of the propellant affects the velocity of its flow which in turn affects the velocity of the exhaust. That's why there're two sets of formula for specific impulse determined by either mass flow rate or exhaust velocity as they complement each other.

Burning 150t of fuel in 115s inside a 100 cubic metre tank is not the same as burning 150t of fuel in 115s inside a 200 cubic metre tank. That's why liquid fuel engines generally have higher Isp than SRBs due to their lower thrusts and higher fuel efficiencies compared to solids.

 

[Quickie]

Yeah, that's what I thought gave you such a high Isp. Without fuel density it will give you skewed results since we're talking about solid fuels, not liquids, specifically their efficiency relative to thrust, hence the whole point of specific impulse.

Mass flow rate isn't the same as fuel burn rate. The viscosity of the propellant affects the velocity of its flow which in turn affects the velocity of the exhaust. That's why there're two sets of formula for specific impulse determined by either mass flow rate or exhaust velocity as they complement each other.

Burning 150t of fuel in 115s inside a 100 cubic metre tank is not the same as burning 150t of fuel in 115s inside a 200 cubic metre tank. That's why liquid fuel engines generally have higher Isp than SRBs due to their lower thrusts and higher fuel efficiencies compared to solids.

Actually, the liquid fuel mass flow rate (which is really the rate of the amount of liquid fuel that is combusted) and solid fuel burn rate (for solid rocket engines) refer to the same thing i.e. the amount of propellant that was burned/combusted in producing the thrust.

The Impulse Formula can be applied to any type of engine whether it's a liquid rocket engine, solid rocket engine, jet engine, automotive engine etc.

 

[sunnymaxi]

https://twitter.com/i/web/status/1588561720527626240