China's Space Program News Thread

[Lime]

It always makes me confused when someone says a rocket debris is uncontrollable.
In other words, can we say a bullet is uncontrollable after shooting? It depends on whether the shooter has a good shooting skill.
I used to see some information that China has the ability to predict the re-entry area before launch rocket.
I wonder why US take so much care about it? Maybe they don't have the prediction technology so know nothing about it or just want to depreciate China's achievement?

 

[Fedupwithlies]

just want to depreciate China's achievement?

100% this

Edit: Yea, I'm angry too, Loveleenkr. Me too.

 

[Lime]

I know the 1st stage of CZ5B is very big. But it also doesn't take too much time to reenter which means the debris is not too much affected by the change of atmosphere.
The prediction of weather is more and more accurate nowadays, so I think prediction of re-entry area is feasible and the key is how to make the prediction more accurate.

 

[kbecks]

It always makes me confused when someone says a rocket debris is uncontrollable.
In other words, can we say a bullet is uncontrollable after shooting? It depends on whether the shooter has a good shooting skill.

It's controlled if you intentionally start the deorbit like most rockets do. Turn around 180 degrees and light the engines to rapidly slow down and fall out of orbit over a specific area. The CZ5B didn't do this, it just sat in orbit and experienced drag to slow-down eventually in the future.

I know the 1st stage of CZ5B is very big. But it also doesn't take too much time to reenter which means the debris is not too much affected by the change of atmosphere.

The point is that no one knows WHEN it well re-enter, including China. The CZ5B was left in orbit to slowly decay from drag, similar to the SpaceX dragon trunk that recently re-entered and wasn't great. They should both be criticized for this, though the CZ5B is massive in comparison to the Dragon trunk.

Orbital decay happens because of drag on the vehicle which comes from air/atmosphere which change at various altitudes. It is quite impossible for anyone to accurately predict the levels of drag that a tumbling rocket body with uncertain and unknown orientation (and therefore drag forces). China is simply relying on probability that says they will most likely hit an ocean because they cover most of Earth, doesn't mean it's any sort of skill.

There are so many factors that stack up and impact the deorbit time it is truly impossible they knew where it would be. For example you mention weather forecasting has gotten better - but do you think you can accurately predict the winds down to the exact speed for the next ~6 days? No, not perfectly. Keep in mind these things orbit the Earth once every ~90 minutes, so over 6 days if you are off by even 0.5% then that means hitting the other side of the world.

Of course Western media is making a huge deal out of this and likely won't be as harsh on the recent SpaceX incident, but that doesn't mean either SpaceX or China are innocent in doing this.

 

[Lime]

The two re-entry of 1st stage of CZ5B, one is near Maldives and another is near Malaysia, but neither hit the land and both fall into the sea not much far from the coast. People near the coast can see the meteor-like deorbit process.

I used to read a paper in China says they use some technology to predict and control the deorbit process. It is more than 5 year ago, maybe they have improved the technology.

So I still think they have the ability, maybe some technology is secret, otherwise it is so fortunate that each re-entry just near the coast but never hit the land.

 

[davidau]

The West, especially youy know who, are always China knockers. They are purple with China's success in aerospace technology.

The two re-entry of 1st stage of CZ5B, one is near Maldives and another is near Malaysia, but neither hit the land and both fall into the sea not much far from the coast. People near the coast can see the meteor-like deorbit process.

I used to read a paper in China says they use some technology to predict and control the deorbit process. It is more than 5 year ago, maybe they have improved the technology.

So I still think they have the ability, maybe some technology is secret, otherwise it is so fortunate that each re-entry just near the coast but never hit the land.

 

[Lime]

CZ5BY1 re-entry near the west coast of north Africa.
CZ5BY2 re-entry near the west coast of Maldives.
CZ5BY3 re-entry near the south coast of Sulu Archipelago.

All of three are not far from a coast but fall into the sea in the end.

 

[davidau]

View attachment 94579
CZ5BY1 re-entry near the west coast of north Africa.
CZ5BY2 re-entry near the west coast of Maldives.
CZ5BY3 re-entry near the south coast of Sulu Archipelago.

All of three are not far from a coast but fall into the sea in the end.

China is reputed for its mathmetics and I am sure they have calculated and recalculated the landing sites in the oceans. But the West are bent on knocking China and scare the uninformed populace of the West, especially the yanks!

 

[kbecks]

So I still think they have the ability, maybe some technology is secret, otherwise it is so fortunate that each re-entry just near the coast but never hit the land.

Yes they are fortunate as you say, it's luck and probability. Most of the ground track is over the ocean so that is the most likely place, again that doesn't mean its responsible.

I used to read a paper in China says they use some technology to predict and control the deorbit process. It is more than 5 year ago, maybe they have improved the technology.

That's pretty vague and lacking any actual information, you're probably talking about tracking debris with radar? And by "technology" do you mean deorbiting the stage like everyone else does? You and a few others seem to really be pushing hard for these talking points without any logical or physics based explanation.

China is reputed for its mathmetics

This is getting hilarious at this point - it's not about mathematics, there isn't some formula that no one can solve except the chinese. It's about uncertainty in your input variables that makes it impossible to get the right answer. You guys are shilling pretty hard and ignoring reality and science.

 

[zbb]

Yes they are fortunate as you say, it's luck and probability. Most of the ground track is over the ocean so that is the most likely place, again that doesn't mean its responsible.

And by "technology" do you mean deorbiting the stage like everyone else does? You and a few others seem to really be pushing hard for these talking points without any logical or physics based explanation.

Before continuing your tirade about how China acts irresponsibly while "everyone else" deorbit their rocket stages responsibly, let's look at some cold hard data. The following Nature paper was written by Canadian researchers based on American space tracking data.

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Despite China and the USA having had similar number of total space launches since 2010, the number of potentially hazardous rocket stages left in orbit by China is less than half of that of the USA. 41% of the overall casualty risk to someone on the ground is contributed by rocket stages launched by the USA, while China only contributes 17%. Europe has left more uncontrolled rocket stages in orbit than China and has similar contributions to casualty risk as China despite Europe having had far fewer space launches than China.

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But how can this be? Didn't the always truthful Western media tell us how USA and Europe have policies in place to limit casualty risk of uncontrolled rocket entries? Well, they do have great sounding policies in place, except they are only applied when it's convenient.

In the USA, the Orbital Debris Mitigation Standard Practices (ODMSPs) apply to all launches and require that the risk of a casualty from a reentering rocket body is below a 1-in-10,000 threshold

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. However, the US Air Force waived the ODMSP requirements for 37 of the 66 launches conducted for it between 2011 and 2018, on the basis that it would be too expensive to replace non-compliant rockets with compliant ones

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. NASA waived the requirements seven times between 2008 and 2018, including for an Atlas V launch in 2015 where the casualty risk was estimated at 1 in 600 (ref.

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).

The fact of the matter is all space powers, including China, only deorbit rocket stages when it is relatively convenient to do so, and the cold hard data clearly shows that China has in fact been far more conscientious in deorbiting rocket stages than both the USA and Europe.