Author Topic: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION  (Read 196543 times)

Offline saliva_sweet

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #340 on: 10/28/2017 11:09 am »
Anyone have any idea what just happened to the R/B from this launch? Did they perform a de-orbit manoever???


1 42802U 17038B   17293.72551647  .00027554  34224-5  23039-2 0  9996
2 42802  24.5026  10.7656 8296019 214.1455  24.5398  1.15434098  1332
1 42802U 17038B   17298.50320531 -.00000191  22902-6  00000+0 0  9993
2 42802  24.2449   8.5033 5926106 217.8158 334.7218  4.30932446  1399
1 42802U 17038B   17298.50320531 -.00000191  22902-6  00000+0 0  9993
2 42802  24.2449   8.5033 5926106 217.8158 334.7218  4.30932446  1399
1 42802U 17038B   17298.50320531 -.00000191  22902-6  00000+0 0  9993
2 42802  24.2449   8.5033 5926106 217.8158 334.7218  4.30932446  1399
1 42802U 17038B   17298.50320531 -.00000191  22902-6  00000+0 0  9993
2 42802  24.2449   8.5033 5926106 217.8158 334.7218  4.30932446  1399
1 42802U 17038B   17299.50658123  .00002909 -18328-4  00000+0 0  9999
2 42802  24.1857   6.6360 2957658 221.3868 298.2410  9.85103635  1432

Why do all the TLEs have the same set number?

I got them from Space-track.org

Offline saliva_sweet

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #342 on: 10/28/2017 11:17 am »
I guess it's the same observation being refined over time. All except the last TLE are bugged. But I'm not sure.

Offline Raul

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #343 on: 10/28/2017 11:09 pm »
Anyone have any idea what just happened to the R/B from this launch? Did they perform a de-orbit manoever???
No de-orbit maneuver, this is standard gradual deceleration of the second stage before reentry and decay from GTO due to drag in upper atmosphere at perigee 154, 120 and 95 km.

Offline Comga

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #344 on: 10/29/2017 03:40 am »
Can someone translate those TLEs into date, apogee, and prrigee?
The decay of second stages left in GTO orbits has been of interest for a long time.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Raul

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #345 on: 10/29/2017 08:17 am »
Can someone translate those TLEs into date, apogee, and prrigee?
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed

Offline saliva_sweet

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #346 on: 10/29/2017 09:07 am »
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed

So they were separate TLEs. Can you explain why they had the same set number - 999 (first three digits of the last element of line 1)? I thought these were supposed to be incremented each time a new TLE set was created.

Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed

So they were separate TLEs. Can you explain why they had the same set number - 999 (first three digits of the last element of line 1)? I thought these were supposed to be incremented each time a new TLE set was created.

They are but I got them from Space-track.org where they are all 999 for some reason

Offline saliva_sweet

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #348 on: 10/29/2017 09:20 am »
They are but I got them from Space-track.org where they are all 999 for some reason

Space-track sets all set numbers in all TLEs for all objects to 999?

They are but I got them from Space-track.org where they are all 999 for some reason

Space-track sets all set numbers in all TLEs for all objects to 999?

On my account they seem too, I assumed it was the same for everyone.

Offline Comga

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #350 on: 10/31/2017 03:44 pm »
Can someone translate those TLEs into date, apogee, and prrigee?
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed
Adding in the initial orbital elements from the Update thread and plotting:
It looks like the second stage hit a brick wall in late October.
Possibly had the perigee tidally pulled lower and it snowballed.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline woods170

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #351 on: 10/31/2017 05:51 pm »
Can someone translate those TLEs into date, apogee, and prrigee?
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed
Adding in the initial orbital elements from the Update thread and plotting:
It looks like the second stage hit a brick wall in late October.
Possibly had the perigee tidally pulled lower and it snowballed.
That brick wall is known as Earth's atmosphere.

Offline Lar

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #352 on: 10/31/2017 06:38 pm »
There isn't a step change in density, it's more gradual (leading to expectations of a less steep decay curve) but the effect might as well be a brick wall I guess?
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Offline Comga

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #353 on: 10/31/2017 06:56 pm »
Can someone translate those TLEs into date, apogee, and prrigee?
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed
Adding in the initial orbital elements from the Update thread and plotting:
It looks like the second stage hit a brick wall in late October.
Possibly had the perigee tidally pulled lower and it snowballed.
That brick wall is known as Earth's atmosphere.

As Lar said, the atmosphere is not a brick wall. 
Look at something like the orbital decay of Tiangong 1.  It spent all of October in the atmosphere below 310 km without falling out of the sky. The decay does, however, get steeper all the time.
The Bulgariasat second stage spent four months dipping below 200 km on each orbit. 
Then something passed a threshold, either a tipping point in atmospheric density or an external event, like a gravitational tug  from the Moon. 

A salient question is what was that event, and what does it say about the decay of other second stages.  But that's for another thread.
« Last Edit: 10/31/2017 08:03 pm by Lar »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Lars-J

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #354 on: 10/31/2017 07:46 pm »
Can someone translate those TLEs into date, apogee, and prrigee?
Fri Oct 20 2017 17:24:44 GMT      154/63757km
Wed Oct 25 2017 12:04:36 GMT   120/19026km
Thu Oct 26 2017 12:09:28 GMT   95/5533km   
Fri Oct 27 2017                     Decayed
Adding in the initial orbital elements from the Update thread and plotting:
It looks like the second stage hit a brick wall in late October.
Possibly had the perigee tidally pulled lower and it snowballed.
That brick wall is known as Earth's atmosphere.

As Lar said, the atmosphere is not a brick wall. 
Look at something like the orbital decay of Tiangong 1.  It spent all of October in the atmosphere below 310 km without falling out of the sky. The decay does, however, get steeper all the time.
The Bulgariasat second stage spent four months dipping below 200 km on each orbit. 
Then something passed a threshold, either a tipping point in atmospheric density or an external event, like a gravitational tug  from the Moon. 

A salient question is what was that event, and what does it say about the decay of other second stages.  But that's for another thread.

A circular LEO orbital decay is going to be a lot more gradual and predictable.
« Last Edit: 10/31/2017 08:04 pm by Lar »

Offline envy887

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #355 on: 10/31/2017 07:54 pm »
The Bulgariasat second stage spent four months dipping below 200 km on each orbit. 
Then something passed a threshold, either a tipping point in atmospheric density or an external event, like a gravitational tug  from the Moon. 

A salient question is what was that event, and what does it say about the decay of other second stages.  But that's for another thread.

There are several exponentially compounding effects here. Air density and thus drag at 95 km is some 100x higher than at 154 km. Also, as each perigee pass slows the stage, the apogee drops significantly - and since most of the orbit time is around apogee, the next perigee pass happens much sooner.

154/63757km has a period of 20.7 hours
120/19026km has a period of 5.8 hours
95/5533km has a period of 2.48 hours

So even though that last orbit doesn't look substantially lower, it's decaying ~1000x faster than the highest orbit.

Offline Comga

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #356 on: 10/31/2017 09:22 pm »
All that is known.
The atmosphere doubles in density roughly every 20 km
Lowering the perigee reduces the orbital period resulting in more  passes through the top of atmosphere per day.
The emptied second stage is particularly light and large, almost a giant aluminum balloon.
Nevertheless, the terminal decay is rather dramatic.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline envy887

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #357 on: 11/01/2017 01:18 am »
All that is known.
The atmosphere doubles in density roughly every 20 km
Lowering the perigee reduces the orbital period resulting in more  passes through the top of atmosphere per day.
The emptied second stage is particularly light and large, almost a giant aluminum balloon.
Nevertheless, the terminal decay is rather dramatic.
Density doubling every 20 km is not accurate in this perigee range. Around 120 km there is a "knee" in the curve and density increases more than 100-fold in just 25 km. This makes decay extremely sensitive to perigee altitude.

The plots below model air density from 95 to 155 km; one is on a log scale, the other the same data on a linear scale:
Data from: https://omniweb.gsfc.nasa.gov/vitmo/msis_vitmo.html
« Last Edit: 11/01/2017 01:33 am by envy887 »

Offline Comga

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Re: SpaceX Falcon 9 : BulgariaSat-1 : June 23, 2017 : DISCUSSION
« Reply #358 on: 11/01/2017 01:42 am »
Neat data
The log-linear assymptotes show that above 130 km the doubling height is ~13 km
Below 110 km it's only ~3 km
That is a lot like a brick wall.

Doubling every 20 km is a decent approximation above 300 km
Near the ground, it doubles around 20 kft or 6 km.
SO nonlinear.
« Last Edit: 11/01/2017 01:45 am by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Theres a new elset on Space-track.org for it... what the heck is going on with their elsets??


1 42802U 17038B   17305.79196749 +.99999999 -28699-4 +93816-8 0  9999
2 42802 024.1564 357.8001 2618557 238.2422 285.5175 10.75890139002054


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