An hypergolic rocket has similar performance to a LOX/Kerosene rocket in basically all aspects. The only reason why people have been dropping hypergolics from use is because of the toxicity of the propellant. LOX/Kerosene doesn't have better performance. The propellant density and Isp of both is basically the same.
N2O4/UDMH does have similar ISP to Kerosene/LOX, but modern propellant chilling and insulation means more fuel can be loaded, which is still today an continous advancing techologny.
There is nothing particularly problematic about handling LOX or even liquid Methane. Like I said, the original V-2 rocket, it used LOX. The Soviets gave the PRC a license to the R-2 rocket, which is basically an extended V-2. This was called the Dongfeng-1 and it used LOX/Ethanol.
So why didn't China develop cryogenic rockets earlier? Probably people like you who waffle on about the tiny little potential benefits of keeping hypergolics in service instead of just embracing new technology,
Claiming that cryogenic LOX is some kind of new novel propellant is bullshit.
When did I claim that? I'm just saying that China needs experience with developing engines for that kind of fuel if they are to make better rocket engines.
There is nothing particularly problematic about handling LOX or even liquid Methane. Like I said, the original V-2 rocket, it used LOX. The Soviets gave the PRC a license to the R-2 rocket, which is basically an extended V-2. This was called the Dongfeng-1 and it used LOX/Ethanol.
There's a big difference in handling those fuels and making a cutting edge engine that can push the performance to the limit while having capabilities like deep throttling and restarting
What, you think you can leak hypergolic propellant? Really? You are going to leak corrosive toxic propellant?
Preventing leaks of a giant red clouds of death is very different from invisible hydrogen, methane or even liquid oxygen leaks. And guess, what, unlike N2O4/UDMH, we tend to use lots of hydrogen/methane/oxygen in lots of industries, so lesson learned on how to prevent and detect the invisible and common leakage of this fuels can be applied to dozens of industries.
And for your information the difference between designing a liquid cryogenic and hypergolic rocket, it isn't that big
Other then the alloys needed to withstand the compressed oxygen at high temperatures, which tends to melt most alloys, pure oxygen being so chemically reactive, that a very important factor that you seem to have left out. Oh and the cryogenic chilling of the propellant, the insulation needed for the tanks without weighting too much(NASA invented a highly lightweight but extremely effective insulating foam for their rockets-the orange foam that you see on the space shuttle, which has gone on to see many applications in other areas), the ground support launch sites that has to store the chilled propellants and transfer them to the rocket right before take off, potential boiloff if the rocket sees too much delays, the careful design of the rocket that has to make two giant tanks of liquid fuel at vastly different temperatures play nice-which has caused more then one rocket failure. And the engine has to made out of alloys that don't turn brittle at extremely cold temperature.
Oh and flowing such cold liquid in a rocket's piping has it's own issues that needs solving. For example, for cryogenic rockets, you need to "pre-chill" the engine before take off by running some of the fuel though the engine's pumping to prevent thermal shock. Not only is the engine pre-chilled to protect itself from the cold propellant, it’s also done to prevent the propellant from thermal shock from the warm engine. If the propellant boils before reaching the impellers in the pumps, it can cause cavitation, which can cause damage to the engine and fuck with the pumps. It's part of why ground support for a cryogenic rocket is so important and takes so long. Not easy considering how complex an rocket engine is and how it's supposed to just leak a tiny amount of fuel into the piping and not blow it's entire load on the launch pad before ignition. This process can take hours and the engine has to be dotted with sensors to ensure that the engine is evenly cooled and at the right pace. Oh and running the hot rocket exhaust right next to an engine that's cooled to -200 degrees also presents engeering challenges. You don't have to deal with this in hypergolics. Which is a plus I guess, but not worth hampering your development of modern rocket engines.
Granted it's more on ground support then the actual rocket design, but still important.
Oh and see what I mean by common design? All cryogenic rockets regardless of fuel types do this and they can all benefit from experience in this area. And since the oxygen is the main issue with your engines, designing an alloy to be chemically resistant to oxygen is going to help for methane, hydrogen or RP-1 rockets. If someone designs an alloy that can withstand being at room temperature and -200 a minute later to help speed up chill down, it can be applied to all sort of uses. If someone develops an alloy to prevent all those pesky hydrogen leaks, that alloy has many use in any industry that uses pure hydrogen, which is a lot. If someone finds a way to cool the fuels quicker and more effectively, again, many uses in many areas. You don't see this kind of benefits when working with such a niche fuel like N2O4/UDMH.
But nah man, the only difference between hypergolic rockets and cryogenic rockets is just the igniter. You're the expert.
It is basically the igniter. An hypergolic rocket doesn't need an igniter because the fuel starts burning by itself once you mix the propellants together. And a cryogenic rocket requires an igniter,
Considering how complex rocket engines are designed and how difficult it is to start and re-ignite a rocket is, which is very important to a reusable rocket. That's a bigggg difference. It's like saying that a electric car and ICE car are basically the same because it has a body and 4 wheel, it's called a car and the "only" difference is the engine. And see above to see some other massive differences between the two.
If you simplify shit so much, you might as well summarize the different between a reusable rocket and an expandable rocket as "one lands, the other doesn't" and leave out all the technical details that makes a reusable rocket possible, like all the complicated engine design needed for throttling, restarting, the landing algorithm, the rocket gimbals etc etc. What's the difference between a plane and a tank? One flies, the other doesn't, only one difference, they aren't so different after all I guess.
See what I mean by lost capability? If you're mainly working with N2O4/UDMH that doesn't need an igniter, of course the complicated technology behind re-igniting rocket engine in flight multiple times is going to fall behind, which again, is very important if you want to develop a reusable rocket. And like I said earlier, all the experience with thermal shock and working with cryogenic fuel, that shit needs time, institutional knowledge and hands on experience to learn. You can't just read it out of a book. China isn't gaining this knowledge without operating cryogenic rockets regularly.
Fun fact, when China launched it's first cryogenic rocket in 2015, some of the older private companies like Landspace were already founded. Ispace was founded in 2016. American/Chinese private space companies drew it's staff from the government sector, a huge chunk of SpaceX employees were former NASA that had experience with cryogenic rocket/fuel systems. While for China, a lot of the private companies were probably former CALT engineers that had little to no experience with cryogenic rockets considering that the first cryogenic rocket launched after the company was founded, especially not for ground support, which as we saw above, is also important. No wonder it's taking some of this early companies so long to get a cryogenic rocket in operation.
Hydrazine or UDMH is still used in quite a lot of last stages. You know the thing which puts the actual satellite in orbit. And many satellites still use it to move in space. The last stage of most ICBMs also uses hypergolic rockets to deploy MIRV warheads.
Oh wow, those tiny edge cases sure do compare to the thousands of uses of RP-1, hydrogen, liquid oxygen and methane in dozens of industries other then rocketry.
N2O4/UDMH has roughly similar performance to LOX/Kerosene or LOX/Methane.
Not with modern propellant chilling and compression methods to allow for more fuel for volume to be fitted onto a rocket. This is still being worked on and improved.
I also think that China needs to take its hypergolic rockets out of service. They need to replace the Long March 2/3/4 with the Long March 7. But this has nothing to do with performance. It is just because of toxicity. It's not a good idea to be dumping rocket stages with toxic fuel in them overland.
And work with modern fuels see many cross over technologies that can benefit over industries. Hypergolics are a dead end for many reasons.
As for chilled and densified propellant, the Soviets did that with some versions of the R-7.
And is China doing it with their hypergolics? No? Then why bring it up?
