Wentian Long March 5B Core Stage Reentry Update and Discussion Thread

[sevenperforce]

6 hours ago, steve9728 said:

I measured about 58 to 60km or so from the nearest land.

Within the splashdown ellipse.

[steve9728]

16 minutes ago, sevenperforce said:

Within the splashdown ellipse.

It's daylight in the Philippines now and within a few hours there should be video or photos about the wreckage that landed, if any.

[magnemoe]

14 hours ago, steve9728 said:

It's daylight in the Philippines now and within a few hours there should be video or photos about the wreckage that landed, if any.

Don't think much will be found, if over water the only thing who float might be the helium tanks if they use titanium for them, they have showed up from time to time. 
Yes stuff like the engine chamber will probably survive reentry but it will sink. 

[steve9728]

1 hour ago, magnemoe said:

Don't think much will be found, if over water the only thing who float might be the helium tanks if they use titanium for them, they have showed up from time to time. 
Yes stuff like the engine chamber will probably survive reentry but it will sink. 

According to the previously CCTV's documentaries, they use aluminium for the tank. Now a day has passed, and I personally haven't seen any videos from the Philippines. Then maybe we'll have to wait a few years for someone to go diving to see it hahaha

[SunlitZelkova]

2 hours ago, steve9728 said:

According to the previously CCTV's documentaries, they use aluminium for the tank. Now a day has passed, and I personally haven't seen any videos from the Philippines. Then maybe we'll have to wait a few years for someone to go diving to see it hahaha

The water doesn’t look to be particularly deep, I would have to go check the exact depth later but it is possible this can be reached by illegal salvage crews.

Unfortunately such organizations operate across South East Asia and have been known to deface WWII wrecks- and thus the bodies of the war dead in them- from time to time.

The law enforcement management of these crews has not been great, sometimes entire ships/wrecks have disappeared without anyone knowing for years.

These crews clearly don’t have a lot of care about what they pick up so I wouldn’t put it beyond them to pick up a rocket engine component, shrug, and then move on.

[steve9728]

"I can't read Chinese, I never hear about it, so it never happened"

 

CNSA's official statement from the official website: *Announcement I, II & III about the CZ-5B Y3 rocket wreckage*

 

Spoiler

In fact, I wonder if there is a possibility, or not, that the CNSA has done some calculations and simulations of the fall zone of the rocket wreckage, based on data from numbers of atmospheric science satellites that have been launched. After all, 'probability', or 'luck' is a crucial factor in this thanks to the vast size of the sea, but it still needs takes some skill to catch it. It may sound a bit outrageous, and I think it is too. But it does give me that feeling.

[JoeSchmuckatelli]

3 hours ago, SunlitZelkova said:

The water doesn’t look to be particularly deep, I would have to go check the exact depth later but it is possible this can be reached by illegal salvage crews.

Unfortunately such organizations operate across South East Asia and have been known to deface WWII wrecks- and thus the bodies of the war dead in them- from time to time.

The law enforcement management of these crews has not been great, sometimes entire ships/wrecks have disappeared without anyone knowing for years.

These crews clearly don’t have a lot of care about what they pick up so I wouldn’t put it beyond them to pick up a rocket engine component, shrug, and then move on.

More like "sell to the highest bidder".

[sevenperforce]

1 hour ago, steve9728 said:

CNSA's official statement from the official website: *Announcement I, II & III about the CZ-5B Y3 rocket wreckage*

Inaccessible from my phone browser in Washington DC, if that tells you anything.

I am curious, though. Wiki lists LM-5 at 14 tonnes to GTO and LM-5B at 25 tonnes to LEO. Obviously LM-5B would have abysmal performance to GTO (if it could even reach GTO, which is doubtful), but what about sending LM-5 to LEO? Would it have higher or lower performance than LM-5B?

The LM-5 upper stage has a wet mass of 39 tonnes and is powered by a pair of YF-75Ds, with a combined thrust of 177 kN. They have multiple restarts. If a 25-tonne+ payload was launched to LEO on a standard LM-5 with the upper stage, the T/W ratio at staging would be, like, 0.02 gees or something similarly very low. Is that why they don’t put the core into a high suborbital trajectory (like the Shuttle or SLS) and use the upper stage for orbital insertion? The Shuttle managed it.

Surely even with the low T/W ratio, they could push more payload into LEO with the upper stage than without it. 

[steve9728]

41 minutes ago, sevenperforce said:

Inaccessible from my phone browser in Washington DC, if that tells you anything.

Weird, I can open it from my pc chrome in UK but here it is:

Spoiler

Except of the engine, you need to think about the size of the station module my friend: they are pretty long and heavy: core module is 16.6m, Wentian and Mengtian is 17.9m. With 22.5 tones for the core module and 23.2 for the Wentian. As a comparison, the length about Shijian-20 launched by CZ-5 Y3 rocket to GTO was 8m and 8 tones. 

(CZ-5 & CZ-5B)

If we put one more stage at middle of the CZ-5B, it will certainly have a significant impact on the rocket's centre of gravity and mass. The budget and time given for the project is limited, and if there is an impact, then the time and money for the corresponding design justification will have to be extended and invested next. Besides the second launch was failure makes whole project delay for nine hundred days. "So, guys, why not...?"

 

Core stage: 33.16m + Second stage:11.54m + CZ-5B version fairing: 20m=64.7m: We are 7.73m higher than the original design. Put everything about physics aside, this even required corresponding modifications to the interior of the VAB and the launch side - just for this one model.

Edited August 1, 2022 by steve9728

[SunlitZelkova]

3 hours ago, JoeSchmuckatelli said:

More like "sell to the highest bidder".

Yeah, this is what I meant. Only after re-reading what I wrote am I now realizing it is not clear.

What I meant by “move on” was just throw it in the pile of scrap and keep going without telling anyone.

3 hours ago, steve9728 said:

"I can't read Chinese, I never hear about it, so it never happened"

 

CNSA's official statement from the official website: *Announcement I, II & III about the CZ-5B Y3 rocket wreckage*

 

  Reveal hidden contents

In fact, I wonder if there is a possibility, or not, that the CNSA has done some calculations and simulations of the fall zone of the rocket wreckage, based on data from numbers of atmospheric science satellites that have been launched. After all, 'probability', or 'luck' is a crucial factor in this thanks to the vast size of the sea, but it still needs takes some skill to catch it. It may sound a bit outrageous, and I think it is too. But it does give me that feeling.

Quoting myself from when Tianhe launched-

“

There is a journalist for a Chinese domestic aerospace magazine claiming that the core stage entering orbit was well understood from the beginning of the design of the Long March-5B. They apparently think 74% (or whatever it was) chance of it hitting the ocean is safe enough.

“

It would take awhile for me to find the exact magazine in case you are interested.

Anyhow, I have to wonder if part of their justification is based on how Skylab was launched. The massive S-II went into orbit and did not decay until 1975 or so.

They may thus feel that it is acceptable to do risky things if the cost of doing it safer is too much. It would have taken way too long and too much money to build a kick stage for the Skylab dry workshop, perhaps the CSS engineers were pressed for money in a similar manner?

We don’t know the real internal funding situation of CNSA, for all we know there may be a Grechko-like presence in the PLA railing against crewed spaceflight in every manner possible. They may have had no choice, just as it wasn’t really feasible for NASA to ask for funding to build a one off kick stage for Skylab during the post-Apollo massacre of their budgets.

[sevenperforce]

12 hours ago, steve9728 said:

Core stage: 33.16m + Second stage:11.54m + CZ-5B version fairing: 20m=64.7m: We are 7.73m higher than the original design. Put everything about physics aside, this even required corresponding modifications to the interior of the VAB and the launch side - just for this one model.

Ah, okay, that makes sense. Essentially the same reason we can't slap a giant upper stage on SLS, then. 

Well, they should have done a single-orbit disposal trajectory like the Shuttle and SLS. Wentian would have had to do a longer orbit-raising burn, which would have decreased station lifetime, but that's the price you pay if you're not going to do the work to enable controlled disposal.

 

[steve9728]

1 hour ago, sevenperforce said:

Ah, okay, that makes sense. Essentially the same reason we can't slap a giant upper stage on SLS, then. 

Well, they should have done a single-orbit disposal trajectory like the Shuttle and SLS. Wentian would have had to do a longer orbit-raising burn, which would have decreased station lifetime, but that's the price you pay if you're not going to do the work to enable controlled disposal.

 

Unfortunately ‘Trolley Problem’ is everywhere

KSP logic: do what you said as well. Give Tianzhou-3 a larger tank for refuel the Wentian module when it docked with the core module (Both front and rear docking port of core module all have ability to refuel). Let Tianzhou-3 docking at rear docking port and let Tianzhou-4 flying with the station. When Wentian docked, refuel it and let Tianzhou-3 leave the station. Then put the Tianzhou-4 back to the rear port. Or even just simply launch another Tianzhou only for refuel the Wentian and Mengtian.

But the reality is that Tianzhou-2,3,4 and 5 are all in same batch and same assembly line product. The only difference on Tianzhou-2 is it had a grapple fixture for the robotic arm testing. And meanwhile, we have the problem that we all struggle with: the budget and deadline.

[tater]

11 minutes ago, steve9728 said:

Unfortunately ‘Trolley Problem’ is everywhere

It's best practices, or "who cares?" Those are the 2 options, and they chose "who cares?"

Smaller stuff happens all the time, accidents, etc, also happen and has not yet harmed anyone that I know of, but letting core stages do this on purpose is irresponsible.

 

Edited August 1, 2022 by tater