China's Space Program News Thread

[SanWenYu]

Is the testing a regular feature?

It was to validate the engine's reliability over "long duration run". I guess you can consider reliability a feature.

这是该台发动机成功进行的第二次长程试车，进一步验证了大推力氢氧发动机的可靠性。

 

[Hyper]

What China need that Russia can offer is their experience in developing RD-170 or RD-180, not the technology. Technology is a specific design, not the theory. China has the theory, China does not need the specific design because the Russian engines do not fit CZ-9. What Russia can help is some advice when China faces some challenge in developing YF-130, such as high pressure chamber. The help may be just a few words from the past experience, or months of joint investigation. How could that be given a fixed price?

The idea of Russia selling RD 180 or RD-170 are never practical because CZ-9's design in all its evolution variants was never around any Russian engines. RD-180 is too small while RD-170 is too big.

IMO, the idea was like the rumor of Russia tried to get China on board of PAKFA. It never got serious even if it was true, and once China determined what a 4th gen fighter China want, the idea is over for ever.

Dude you can't transfer experience. It can only be gained or achieved but not bought.

 

[tygyg1111]

Dude you can't transfer experience. It can only be gained or achieved but not bought.

You somewhat can, as a simple example, if you bought an industrial 3D printer it might take several months for your staff to gain mastery over operation, troubleshooting and fixing issues, however if the deal included a temp technician or if you have an employee with previous experience, then small pointers such as "when you set up X, do this with Y to avoid Z consequence", and rules of thumb based on experience e.g., when your output piece has X problem, check Y aspect of the feed and ensure a particular input mesh setting is Z, will save you a lot of time, unnecessary failures and feedstock loss.
Extrapolate this to a much more complex system and you may be able to get major improvements.

 

[Philister]

No, the third stage is essential if you want to get 70t to LEO. Otherwise, you wouldn't reach the delta V for orbit.

70T is theoretically true,but just like delta-4 , the structure (2nd stage)can’t take such weight , so you can actually shoot 27T into TLO but 70T into LEO is just a fantasy

 

[Philister]

It means that it is a rocket designed for both LEO missions and LTO missions.




Why do you think the third stage with YF-75D is used for 70t LEO?

They explicitly stated LTO 27t as the first payload, and it makes sense that a LTO payload would require a third stage.
By contrast, a LEO mission profile will not require a third stage.




I feel like we are talking past each other.

Taxiya and I have already come to an agreement for why the single core CZ-5DY variant has a lower LEO payload than Falcon 9 -- and that's likely because the fuel tanks are smaller and the second stage has only one YF-100.

However, we are now talking about the three core CZ-5DY, which has boosters that have the first stage of the single core CZ-5DY, but that the central core first stage has much larger fuel tanks for longer burn and that the second stage also has two YF-100s rather than one.


What I am suggesting, is essentially this:

View attachment 84769

No point digging too deep, these images are constantly changing over different meetings, now it appears that the data is real but images are just placeholders, if anything is certain, the first stage and boosters would have the same fuel tanks and overall dimensions.
For the less payload, one major factor is, for a reusable rocket, dry mass ratio in first stage matters a lot more than normal ones, and that’s a disadvantage for China, Al-Li hull wasn’t practical till 2020 and they are quiet conservative about the design, there’s no image ever showed that tanks with a common bulkhead was planned for the 1st stage, so far.

 

[taxiya]

Dude you can't transfer experience. It can only be gained or achieved but not bought.

Sure you can. A newbie makes a crappy software that wastes lots of CPU cycles. An expert engineer can review the software with the newbie, show a better structure and tell him why. That experience is learned by the newbie.

 

[taxiya]

70T is theoretically true,but just like delta-4 , the structure (2nd stage)can’t take such weight , so you can actually shoot 27T into TLO but 70T into LEO is just a fantasy

This is a closed case. CZ-5DY has 2 stage configuration in its plan and 70T LEO is not just a theory. See the highlight.


Besides, the argument of structure strength of 2nd stage does not stand. For a LTO 27T, the mass to LEO orbit must be somewhere very close to 70T. This ratio is determined by needed DV(propellant mass) for the relevant orbits. If the structure of 2nd stage is too weak to put 70T into LEO, it won't be able to send 27T into LTO. A good reference of the ratio is Saturn V, 48/128.

 

[pipaster]

This is a closed case. CZ-5DY has 2 stage configuration in its plan and 70T LEO is not just a theory. See the highlight.
View attachment 85275

Besides, the argument of structure strength of 2nd stage does not stand. For a LTO 27T, the mass to LEO orbit must be somewhere very close to 70T. This ratio is determined by needed DV(propellant mass) for the relevant orbits. If the structure of 2nd stage is too weak to put 70T into LEO, it won't be able to send 27T into LTO. A good reference of the ratio is Saturn V, 48/128.

But don't confuse useful payload, with fuel/structural weight. As well you have to consider the maximum fairing size possible for that spacecraft's control authority to handle/local infrastructure.

 

[taxiya]

But don't confuse useful payload, with fuel payload/structural weight.

what do you mean? 运载能力 is useful payload which is 69.3T in the old slide and 70T in recent presentations. Chinese terminology never include fuel and structural weight in its spec of payload.

 

[taxiya]

As well you have to consider the maximum fairing size possible for that spacecraft's control authority to handle/local infrastructure.

Valid point to consider, but that is a point valid for all heavy rockets like Ares V and SLS who both have LEO over 100T in their spec. Remember Ares V at least had the idea of LEO rendezvous before departing for moon. That means its LEO payload of over 150T is real. If we doubt CZ-5DY's LEO payload, we have to doubt all others.