That reusability work is coming along really quick now.
China's Space Program News Thread
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What are CNSA's plans to address this shortcoming?
It is not really a shortcoming per se, engines that use the ORSC cycle are a priori somewhat limited as regards to aggressive throttling. Rocket engines are not supposed to deep throttle in the first place, it runs almost completely counter to what they need design wise to be as efficient as possible at max thrust. Which is the point for making a booster engine in the first place.
The YF-100 project is essentially considered a somewhat direct technological derivative of the RD-120 architecture. Same goes for the Ukrainian RD-801/RD-810 and Indian SCE-200 engine programs. While both YF-100 and YF-115 are in my honest view by far the best and most advanced applications of the base architecture, it is impossible to completely change its attributes. You need a new/other architecture for that. Or...you need something like the RD-191 revisions to the architecture, not an easy task with the current state of the art (you'd need to essentially leap-frog a whole generation of ORSC development).
In this specific instance, the end CZ-8R is going to have enough TWR to not suffer from any throttling limitations, as far as re-usability is concerned. A test article (like the in essence) is a different thing altogether.
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I've read some interesting discussions on TWR and reusability. To have the correct TWR for landing there are a few methods:
- stack lots of little engines - the Falcon 9 method and the one everyone is having a tunnel vision on
- increase the vehicle's dry mass - the Long March 8R method
- use more than one type of engine
One alternative, which is what Long March 8R is going for is to increase the vehicle's dry mass by hanging onto boosters.
The other alternative is to use more than one type of engine on your stage. At time of landing you could just turn off the big engines and land with thrust from a center small engine. This option is not available for SpaceX because they cannot afford to develop two different engines for one rocket so they always go for big clusters of small engines. However for a national space program they may have engines on hand that would allow for this strategy (YF-130 + YF-100 say).
I don't think it is a matter of affording to develop two engines for the same stage. It's that your smaller "landing" engine cannot easily be as efficient as the others for both launch and landing (when viewed as part of the overall stage propulsion system). The dry mass of rocket stages is extremely light, and most of the weight in them comes from the engine assembly anyway. A stage that needs to throw something as fast and far as possible cannot afford to carry weight that is not contributing adequately on an engine TWR basis. Also, running dissimilar engines on the same core at the same time comes with a number of interesting problems (it's not as easy to design as having co-firing boosters or verniers).
SpaceX did not really plan their own way either. At the start, the whole idea about re-usability was with using parachutes to retrieve stages, like the Shuttle SRBs were designed to. Back then only Falcon 1 was running, and Falcon 5 was in the works (Falcon 9 was starting to get designed).
When this approach failed, SpaceX moved to propulsive landing as a choice. You are correct in that SpaceX was lucky with the Merlin design, since converting the stage for re-usability was a lot easier (than one using only one engine, like Atlas V - for example). The original reason for Merlin being at that size was two-fold..falcon 1 and SpaceX not having enough funds at the time to develop something bigger to put in larger orbital designs.
I think what CALT is doing with CZ-8 is both refreshing and expandable btw. Imagine if they manage to enable cross-feeding from the boosters to the stage for ascent, and then use one of the main stage engines for landing. This configuration could become extremely efficient.
SpaceX did not really plan their own way either. At the start, the whole idea about re-usability was with using parachutes to retrieve stages, like the Shuttle SRBs were designed to. Back then only Falcon 1 was running, and Falcon 5 was in the works (Falcon 9 was starting to get designed).
When this approach failed, SpaceX moved to propulsive landing as a choice. You are correct in that SpaceX was lucky with the Merlin design, since converting the stage for re-usability was a lot easier (than one using only one engine, like Atlas V - for example). The original reason for Merlin being at that size was two-fold..falcon 1 and SpaceX not having enough funds at the time to develop something bigger to put in larger orbital designs.
I think what CALT is doing with CZ-8 is both refreshing and expandable btw. Imagine if they manage to enable cross-feeding from the boosters to the stage for ascent, and then use one of the main stage engines for landing. This configuration could become extremely efficient.
As others have said that you don't have to use an engine deep down to 10%. Falcon 9 is an example, Merlin could go down to only 50% ???. SpaceX uses 9 engines and only runs the center one at landing bypassing the 10% requirement. The planned CZ-6X (another effort of VTVL) uses two smaller engines for landing. 921 has 7 engines in each core, YF-100 in its current form when using only one for landing is already good enough.
Besides, there is a study that looking into making YF-100 to 10%.
That's not quite accurate.
A big part of the design was additional redundancy and designing for the inevitable failures.
Eg. Using multiple commercial grade microchips instead of radiation-hardened microchips.
Designing each stage with multiple small engines, so the rocket can handle the loss of a single engine and still complete its mission.
Hi temstar
Need your opinion, the video stated that Chinese telemetry is world class and had dual uses, aside from boasting about our hypersonic advantages over the US it said that it able to maneuver Chang'e 5 upon atmospheric re-entry?
Need your opinion, the video stated that Chinese telemetry is world class and had dual uses, aside from boasting about our hypersonic advantages over the US it said that it able to maneuver Chang'e 5 upon atmospheric re-entry?
China already has the strength of "Star Wars"? Global landscape will be rewritten? Chang'e-5 CLEP.
零零传媒antiterror13
Brigadier
Please educate me why you would think that "both YF-100 and YF-115 are in my honest view by far the best and most advanced applications of the base architecture". Thanks
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