Tiangong-1 Re-entry

[Gargamel]

On 3/16/2018 at 3:24 PM, MaxwellsDemon said:

:: squinting at map ::   Think I should start carrying an umbrella...    

If I recall, you're a fellow NEO'er.... looks like we're right in the middle of one of those high probability impact zones.

 

I sooo want this on my tombstone. 

[tater]

 

 

[MaxwellsDemon]

4 hours ago, Gargamel said:

If I recall, you're a fellow NEO'er.... looks like we're right in the middle of one of those high probability impact zones.

 

I sooo want this on my tombstone. 

Close, central Oer.    How about an engraving of Wiley Coyote holding that little Acme umbrella?  That would make a good tombstone engraving.

[cubinator]

I figure when the thing starts to get below 150 km it's time to start looking outside.

[PB666]

https://www.cnn.com/2018/03/26/asia/china-tiangong-1-intl/index.html

The smallest range is March 31 to April2

[Gargamel]

On 3/25/2018 at 10:08 AM, tater said:

 

 

I really hesitate to call STS-107 an 'uncontrolled reentry'.  It's reentry point was well established, probably down the second.  It just suffered it's failure during a controlled reentry, and the individual aerodynamic properties of the resulting debris caused it to scatter all over the place. 

And while it may be the 50th largest uncontrolled re-entry, getting hit with the 50th largest bullet in the world is still gonna really hurt. 

[YNM]

23 hours ago, Gargamel said:

It's reentry point was well established, probably down the second.  It just suffered it's failure during a controlled reentry, and the individual aerodynamic properties of the resulting debris caused it to scatter all over the place. 

AKA "Rapid Uncontrolled Disassembly".

Edited March 28, 2018 by YNM

[MaxwellsDemon]

An earlier post on this thread speculated that the Chinese space agency may have been unaware of the need for a reboost-- something that I find difficult to believe, as they have more than enough experience in orbital flight themselves to model the upper atmosphere and resulting drag accurately, to say nothing of the availability of data from other countries.  There was evidently a decision made not to reboost it.  What I haven't seen is if there was any good reason not to launch a tug to dock with it and control the re-entry, as the Soviets/Russians did with a number of their space stations (Salyut 7 notwithstanding).  It's puzzling, unless they have something else up their sleeve, like blowing it apart at the last minute. 

[YNM]

18 minutes ago, MaxwellsDemon said:

There was evidently a decision made not to reboost it.

They couldn't be arsed to do it ?

[wumpus]

3 hours ago, Gargamel said:

I really hesitate to call STS-107 an 'uncontrolled reentry'.  It's reentry point was well established, probably down the second.  It just suffered it's failure during a controlled reentry, and the individual aerodynamic properties of the resulting debris caused it to scatter all over the place. 

And while it may be the 50th largest uncontrolled re-entry, getting hit with the 50th largest bullet in the world is still gonna really hurt. 

I really have to wonder about that graph.  The infallible wiki (presumably better than a tweet if little else) lists DOS-3 and DOS-6 as 19.4 and 19.8 tons respectively.  I may have botched a post on another site thinking that Tiangong-1 was in the same class (all the Salyuts were roughly that size).

Officially, they've lost contact with the satellite.  I wouldn't be surprised if their docking procedure requires control of each side (my KSP procedure certainly prefers it), and they aren't sure about the lost side.  Launching a rocket just to bring it down in Point Nemo is expensive, but I suspect the danger of losing face if they can't dock was the critical factor in the decision (especially if the guy responsible for docking had to sign off).

Edited March 27, 2018 by wumpus
ours is but to reason why

[tater]

Maybe it's launch mass, STS is heavy there, as well.

[MaxwellsDemon]

Well, I know that the DOS-6 (Salyut 7) reentry mass included the Cosmos nth* add-on module (think of it as a prototype for the Mir expansion modules, because that's part of what they were testing), so it would have been significantly more massive than previous Salyuts.

 

* need to look the number up if it becomes necessary; there's no way to keep all the Cosmos numbers in one's head

31 minutes ago, wumpus said:

Officially, they've lost contact with the satellite. 

Okay, this makes more sense.  They may very well not be capable of docking a tug with an unresponsive/uncooperative target.  As is known from US and Russian experience, it's far from easy.

[lajoswinkler]

I say Friday (UTC), up to 1000 km west of Japan.

My hopes were the toilet seat strikes my house but I'm out of the danger zone.

[DerekL1963]

2 hours ago, MaxwellsDemon said:

What I haven't seen is if there was any good reason not to launch a tug to dock with it and control the re-entry, as the Soviets/Russians did with a number of their space stations (Salyut 7 notwithstanding).

The Soviet/Russians had/have a spacecraft designed to assist in reboosts which could be modified to assist with de-orbit - Progress.  It's not clear whether or not Tianzhou has the same capability.  It's also not clear at which point they lost control of Tiangong-1...  and docking with an uncooperative target is a tall order even for a controlled vehicle, let alone an automated or autonomous vehicle.

[tater]

Non-trivial docking at this point:

 

[MaxwellsDemon]

Definitely non-trivial.

(To be clear, I wasn't saying that they should be reboosting or trying to control it now.  I was wondering why not several months ago... but if they don't have the capability, then it's a moot point.)

[tater]

14 minutes ago, MaxwellsDemon said:

Definitely non-trivial.

(To be clear, I wasn't saying that they should be reboosting or trying to control it now.  I was wondering why not several months ago... but if they don't have the capability, then it's a moot point.)

And to be clear on my end, I wasn't suggesting that you thought this was currently possible, I was just making a joke

 

[sh1pman]

3 hours ago, tater said:

Non-trivial docking at this point:

They need a Claw!

[MaxwellsDemon]

14 minutes ago, tater said:

And to be clear on my end, I wasn't suggesting that you thought this was currently possible, I was just making a joke

 

Oh, I caught the joke.      Though that video has it clearly rotating much faster than 2.2 degrees a second!

[PB666]

 

 

Edit, didnt see the degree sign. 

 

Edited March 27, 2018 by PB666

[Ultimate Steve]

5 hours ago, lajoswinkler said:

I say Friday (UTC), up to 1000 km west of Japan.

My hopes were the toilet seat strikes my house but I'm out of the danger zone.

Where can I find the whole map?

[kerbiloid]

If they had delivered a demolition charge to burst it into pieces on aerobraking, we would not be having such theme to discuss.

Edited March 28, 2018 by kerbiloid

[lajoswinkler]

 

15 hours ago, Ultimate Steve said:

Where can I find the whole map?

 

http://www.satflare.com/track.asp?q=37820#TOP

 

 

4 hours ago, kerbiloid said:

If they had delivered a demolition charge to burst it into pieces on aerobraking, we would not be having such theme to discuss.

 

Would you sit on such toilet seat? I think not. ˘o˘

[kerbiloid]

3 minutes ago, lajoswinkler said:

Would you sit on such toilet seat? I think not. ˘o˘

Space Shuttle SRB contained self-destruction explosives.
And Tiangong+Shenzhou anyway had several tonnes of hypergolics aboard when people were here.
Soyuz capsule has (had?) a 30 l tank of HTP inside, right behind the pilot's head.
So, I guess 20 kg of TNT would not change risks significantly.

[Kr0noZ]

Well, too bad I won't even be able to see anything from Germany, even IF reentry happened over the mediterranean (which it most likely won't...).
That would have been ONE COOL EASTER GIFT xD