China's Space Program News Thread
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No LES tower? Capsule integrated LES?
full record of the live
Fan art, it looks great though
It is certainly important news to confirm CZ-5DY will have the first stage be capable of being reusable.
But, why would a tethered landing scheme be preferred over having legs? It seems to me that the tethered landing scheme will limit the geographical locations to which the first stage can be recovered at (i.e.: only sites with the tether system), which in turn will also likely limit the number of simultaneous recoveries that can be achieved at once (as that will be limited by tether systems).
Also, if there is a failure with the legs on a rocket during landing, you only lose that given rocket and the specific landing site (which doesn't have much specialized infrastructure) -- but if there's a failure with a tethered landing system, not only may you lose the rocket, but the specialized infrastructure for said landing.
I suppose one benefit is that the lack of legs may save some weight compared to the tether system.... but given how well proven the VTVL with integrated legs have been, I'm surprised they'd choose such a strange system.
It's not like that presentation is trying to be fancy either -- one of the concepts displayed is basically just Starship and Super Heavy, albeit they describe it as only having a payload of 20 tons.
Still, it is encouraging that at least they're seriously looking at reuseable rockets now and they're now explicitly saying that CZ-5DY will be intended to have a reusable compatible first stage.
BTW, I think since late last year we've known CZ-5DY will have a LTO of 27 tons, this isn't new afaik
Considering the new lunar launcher is intended to have a reusable first stage, and that a 27 LTO will have a fairly impressive LEO throw weight, the CZ-5DY is probably the much more important intermediate heavy lift rocket with significant consequences for LEO deployment, until a reusable super heavy (like a VTVL CZ-9(21)) emerges... but a super heavy (reusable or not) won't emerge until late this decade at best.
It is certainly important news to confirm CZ-5DY will have the first stage be capable of being reusable.
But, why would a tethered landing scheme be preferred over having legs? It seems to me that the tethered landing scheme will limit the geographical locations to which the first stage can be recovered at (i.e.: only sites with the tether system), which in turn will also likely limit the number of simultaneous recoveries that can be achieved at once (as that will be limited by tether systems).
Also, if there is a failure with the legs on a rocket during landing, you only lose that given rocket and the specific landing site (which doesn't have much specialized infrastructure) -- but if there's a failure with a tethered landing system, not only may you lose the rocket, but the specialized infrastructure for said landing.
I suppose one benefit is that the lack of legs may save some weight compared to the tether system.... but given how well proven the VTVL with integrated legs have been, I'm surprised they'd choose such a strange system.
It's not like that presentation is trying to be fancy either -- one of the concepts displayed is basically just Starship and Super Heavy, albeit they describe it as only having a payload of 20 tons.
View attachment 83097
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Still, it is encouraging that at least they're seriously looking at reuseable rockets now and they're now explicitly saying that CZ-5DY will be intended to have a reusable compatible first stage.
BTW, I think since late last year we've known CZ-5DY will have a LTO of 27 tons, this isn't new afaik
The cost of such a landing tethering system should be fairly negligible. After all, it is just a bunch of steel towers, cables and nets. So this could easily be deployed widely.
And remember how many failures SpaceX encountered when developing a launch system with legs. This would avoid all those expensive failures and delays as a rocket dropping into a net is really simple.
In addition to saving the weight of the landing legs, they would also require less fuel for landing. Currently SpaceX rockets spend a lot of fuel to slow down and hover before landing. That would translate into cost and payload.
legs require rocket velocity to be reduced to a level where deceleration to 0 results in no distortion of the landing legs. If there is distortion of built in legs, then the rocket is junked. To achieve such a deceleration requires reserve fuel.
wires require rocket velocity to be reduced only to a level such that deceleration does not result in strain on wires exceeding their tensile strength. This requires less reserve fuel.
The amount of reserve fuel required is important because the last bit of fuel doesn't need to carry more fuel, thus results in more deltaV than the first bit of fuel.
I see the tethered landing structure an addition to a dedicated landing pad or landing drone ship, therefor not a geographical limit.
Yes, the destruction of the landing tethering device is an extra damage than a pad.
The tether however reduce or remove the requirement of 1:1 thrust to weight ratio for last moment hovering capability, making the landing easier.
My thought isn't about weight saving although it does. It is the extra requirement of hovering demand on engine's deep throttling capability.
Super Heavy uses similar tethering landing except it is rigged tether instead of wires. Another reason of CZ-5DY's choice for 1st stage.
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