Author Topic: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION  (Read 90301 times)

Offline nicfit

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #380 on: 05/19/2017 03:51 PM »
Regarding the decay of Stage 2: The perigee height won't stay there for long. It will be perturbed higher or lower by the Moon etc. when nearer to apogee. This should be even more marker on a super-synchronous transfer orbit. Next question being, which way will it be perturbed and by how much...?


Stages 2 re-entered in less than half a year for the SES8 et Thaicom 6, both supersync injection orbits --> the moon effect

Offline stcks

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #381 on: 05/19/2017 04:38 PM »
It is left as an exercise for the reader to figure out which ones have decayed and any typos.

Here is what I have gathered:


Online Dante80

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #382 on: 05/19/2017 04:42 PM »
The rather dramatic effect on the Abs-2/Eut-117 orbit comes from the moon too, right?

Offline Comga

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #383 on: 05/19/2017 08:42 PM »
This thread is drifting from discussing the May 15 Inmarsat 5 F4 launch.  These are interesting enough topics but there are dedicated threads for them elsewhere.  (I would love to see a single plot of the second stage apogee heights vs calendar days, but except for THIS second stage, it would go in a general discussion thread.)
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Offline Lar

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #384 on: 05/19/2017 10:45 PM »
This thread is drifting from discussing the May 15 Inmarsat 5 F4 launch.  These are interesting enough topics but there are dedicated threads for them elsewhere.  (I would love to see a single plot of the second stage apogee heights vs calendar days, but except for THIS second stage, it would go in a general discussion thread.)

Yes please... let's find a home for some of this.... interesting but off topic.... (PM me and I'll try to move stuff to the thread identified) Thanks!
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Offline macpacheco

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #385 on: 05/23/2017 01:45 AM »
42698   INMARSAT 5-F4   2017-025A      1401.67min   24.50deg   69839km   381km      
42699   FALCON 9 R/B   2017-025B           1410.43min   24.47deg   70181km   384km

I believe these are identified backwards: the payload is in the 384 x 70,181 km orbit; and the Falcon-9 upper stage rocket body is in the 381 x 69,839 km orbit.   Expect 18 SPCS to swap these in the next couple of days.
Swap has taken place:
42698   INMARSAT 5-F4  2017-025A      1409.24 min    24.52deg    70134km    385km
42699   FALCON 9 R/B    2017-025B      1401.51 min   24.47deg    69835km    378km


Still no maneuvers detected...

Would those be explained by timing so that once they start their burns they get to the right GEO slot, and right now with each orbit the get closer to that proper timing faster than if they did some substantial burns prior ?
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Online Semmel

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #386 on: 05/23/2017 09:02 AM »
42698   INMARSAT 5-F4   2017-025A      1401.67min   24.50deg   69839km   381km      
42699   FALCON 9 R/B   2017-025B           1410.43min   24.47deg   70181km   384km

I believe these are identified backwards: the payload is in the 384 x 70,181 km orbit; and the Falcon-9 upper stage rocket body is in the 381 x 69,839 km orbit.   Expect 18 SPCS to swap these in the next couple of days.
Swap has taken place:
42698   INMARSAT 5-F4  2017-025A      1409.24 min    24.52deg    70134km    385km
42699   FALCON 9 R/B    2017-025B      1401.51 min   24.47deg    69835km    378km


Still no maneuvers detected...

Would those be explained by timing so that once they start their burns they get to the right GEO slot, and right now with each orbit the get closer to that proper timing faster than if they did some substantial burns prior ?

I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

Online jpo234

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #387 on: 05/23/2017 10:25 AM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?

Offline edkyle99

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #388 on: 05/23/2017 02:13 PM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?
Not in my opinion (GEO is a better location), but then again this transfer orbit was given a higher than typical perigee, perhaps to allow for more time before starting ascent. 

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Offline karanfildavut

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #389 on: 05/23/2017 06:35 PM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?

Generally, I was under the impression this is a bad idea due to the repeated transits through the Van Allen belts. Those tend to be hard on satellite electronics. My wager is that the satellite checkout is continuing in some form and that they will start the orbital changes as soon as they are satisfied. I'm sure they can use it to decongest bandwidth in their high demand areas (europe was mentioned before).

Also, AFAIK it's actually not that energetically expensive to change orbital slots in GSO since you can do a racetrack maneuver or something similar. Just raise or lower your orbit by a few km, drift till you get to the correct slot and re-enter. Low total dV expenditure.

Offline macpacheco

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #390 on: 05/23/2017 07:56 PM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?

Generally, I was under the impression this is a bad idea due to the repeated transits through the Van Allen belts. Those tend to be hard on satellite electronics. My wager is that the satellite checkout is continuing in some form and that they will start the orbital changes as soon as they are satisfied. I'm sure they can use it to decongest bandwidth in their high demand areas (europe was mentioned before).

Also, AFAIK it's actually not that energetically expensive to change orbital slots in GSO since you can do a racetrack maneuver or something similar. Just raise or lower your orbit by a few km, drift till you get to the correct slot and re-enter. Low total dV expenditure.
Not energetically expensive, but how long it would take to go half way around the globe that way ? How many months ? Timing can be very important in several situations.
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Offline envy887

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #391 on: 05/23/2017 09:50 PM »
Not energetically expensive, but how long it would take to go half way around the globe that way ? How many months ? Timing can be very important in several situations.
For 30 m/s it can drift at least 180 degrees in 35 days. That's with circular orbits but it might be cheaper and faster to use elliptical orbits to drift.

Offline psionedge

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #392 on: 05/24/2017 06:25 PM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?
They will probably have to go to Geo to check out the satellite before the manufacturer hands it over to the customer. You aren't going to be verifying link budgets and channel performance in GTO.

Offline kevin-rf

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #393 on: 05/25/2017 12:52 AM »
I dont think so. With two burns, one that parks perigee somewhere between where it is now and GEO height and an other one for the final perigee raise they can get to almost any point within 2 or 3 orbits. By now, they must have at least 10 orbits.

The satellite is supposed to be a spare. Would it make sense to leave it in the current transfer orbit until it is actually needed?
They will probably have to go to Geo to check out the satellite before the manufacturer hands it over to the customer. You aren't going to be verifying link budgets and channel performance in GTO.

It will also last longer in GSO, GTO does multiple passes through the Van Allen each day.
I just saw some idiot at the gym put a water bottle in the pringles holder on the treadmill.

Offline friendly3

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #394 on: 05/26/2017 12:11 AM »
Tweeted, but when I went to RT, it said action unavailable and that's because they deleted it.....sorry, which I could have grabbed the pics, but at least screenshot the deleted tweet.

Oh, they deleted it because they typoed. Proton 9 ;D

Anyway, they haven't tweeted the correction.....we get the message and the milestone.



Well you can't blame them, even to this day NASA's website says Inmarsat 5 F4 was launched from the Cape on a Proton-M ::) :

https://nssdc.gsfc.nasa.gov/nmc/spacecraftOrbit.do?id=2017-025A

https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2017-025A
« Last Edit: 05/26/2017 01:36 AM by friendly3 »

Offline kevin-rf

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #395 on: 05/26/2017 12:27 AM »
That's one funny looking Proton.
I just saw some idiot at the gym put a water bottle in the pringles holder on the treadmill.

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