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#380
by
nicfit
on 19 May, 2017 15:51
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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
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#381
by
stcks
on 19 May, 2017 16:38
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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:
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#382
by
Dante80
on 19 May, 2017 16:42
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The rather dramatic effect on the Abs-2/Eut-117 orbit comes from the moon too, right?
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#383
by
Comga
on 19 May, 2017 20:42
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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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#384
by
Lar
on 19 May, 2017 22:45
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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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#385
by
macpacheco
on 23 May, 2017 01:45
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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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#386
by
Semmel
on 23 May, 2017 09:02
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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.
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#387
by
jpo234
on 23 May, 2017 10:25
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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?
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#388
by
edkyle99
on 23 May, 2017 14:13
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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.
- Ed Kyle
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#389
by
karanfildavut
on 23 May, 2017 18:35
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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.
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#390
by
macpacheco
on 23 May, 2017 19:56
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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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#391
by
envy887
on 23 May, 2017 21:50
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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.
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#392
by
psionedge
on 24 May, 2017 18:25
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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.
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#393
by
kevin-rf
on 25 May, 2017 00:52
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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.
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#394
by
friendly3
on 26 May, 2017 00:11
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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 
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=2017-025Ahttps://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2017-025AEDIT: they fixed this in less than 24 hours, so the links now show a Falcon 9 Full Thrust as the launcher
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#395
by
kevin-rf
on 26 May, 2017 00:27
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That's one funny looking Proton.
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#396
by
Antares
on 27 May, 2017 01:41
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A 541 at much less than half the cost. If I were ULA or OrbTK,
late career: buy survival bunker
mid career: cushy job with GovSpace
early career: leave the industry or demand better options from SpaceX.
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#397
by
Dante80
on 27 May, 2017 16:32
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To be fair - and assuming this campaign did do a depletion burn as theorized - this was a 531/4M+5,4 performance (see the WGS campaigns for Delta IV and the AEHF campaigns for Atlas V).
It is assumed that Block 5 may match 541, while still being a two stage kerolox LV (and about 20t heavier than said Atlas V variant).
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#398
by
AncientU
on 27 May, 2017 19:00
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To be fair - and assuming this campaign did do a depletion burn as theorized - this was a 531/4M+5,4 performance (see the WGS campaigns for Delta IV and the AEHF campaigns for Atlas V).
It is assumed that Block 5 may match 541, while still being a two stage kerolox LV (and about 20t heavier than said Atlas V variant).
You are referring to high energy orbits, right?
To LEO, Block 5 will
far surpass Atlas V 551; may come close to matching Delta IV Heavy.
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#399
by
Dante80
on 27 May, 2017 19:22
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You are referring to high energy orbits, right?
To LEO, Block 5 will far surpass Atlas V 551; may come close to matching Delta IV Heavy.
Yep, we were talking about GTO missions. Falcon 9 is an absolute monster as far as LEO is concerned. You cannot beat kerolox in that profile.
Falcon 9 block5 can probably match the ISS throw-weight of Ariane 5 ES. And that is a 760t rocket!
: 