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#260
by
Wolfram66
on 16 May, 2017 16:32
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Q) WRT F9 EXP booster, We know it has no legs not does it have grid-fins, but does it still have the GN2 RCS thrusters? Are the GN2 systems more integral to F9 construction?
thanks in advance
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#261
by
Shanuson
on 16 May, 2017 16:36
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This was NOT a flight to GTO! This used a super-synchronous transfer orbit.
Don't the parameters at insertion (315 km altitude, 10,025 m/s velocity) indicate a subsynchronous transfer orbit?
I calculated it naively with the elliptical orbit and got almost exactly a apogee of geo sync. i.e. 35786 km above earth surface.
v=(u*(2/r-1/a))^.5
u=GM
r=perigee from center of earth
a=semimajor axis
Velocity seems relative to launch site, since it's 0 at launch and not 408 m/s. Adding this in, you get an inertial frame speed of 10435, for a apogee of about 62000 km, or super-synchronous.
Using the posted picture in the update thread after SECO-2 we have 4 data points of R (above ground) and V:
315km - 10025m/s,
321km - 36060km/h=10017m/s
420km - 35770km/h=9936m/s
486km - 35561km/h=9878m/s
using the formular above with GM=3.98438E14 and an Earth radius of 6371km I get an average semimajor axis of about 21340+-50km or Apogee of ~ 29552km.
Adding the 408m/s to V I get an average semimajor axis of 38407+-125km or Apogee of ~ 63688km.
Do smaller errors of the first set hint that it is wrong to add 408m/s? Yet the apogee would be well below GEO strongly suggesting that the later is the better aproximation.
The question for me remains with this analysis what V really is, velocity along the flight path or relative to ground below the stage or relative to launch site?
Edit the TLEs posted show that adding 408m/s seems to be the right way to do it.
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#262
by
hans_ober
on 16 May, 2017 16:41
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Pretty good performance. 70k apogee + an inclination reduction.
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#263
by
AncientU
on 16 May, 2017 16:44
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From the update thread -
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
Definitly Super-synchronous.
Certainly. Only thing is that upper stage will stay up there for a long time.
Not sure how long after orbit these objects were catalogued... but is there a chance that the stage could do a de-orbit burn after a long-duration delay test as done after the last payload insertion?
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#264
by
edkyle99
on 16 May, 2017 16:46
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Pretty good performance. 70k apogee + an inclination reduction.
This one looks to have been a hotter performer than previous Falcon 9s. I'm becoming more convinced that this is an upgraded variant.
- Ed Kyle
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#265
by
stcks
on 16 May, 2017 16:49
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Pretty good performance. 70k apogee + an inclination reduction.
Excellent performance. GTO-1570.
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#266
by
Dante80
on 16 May, 2017 16:52
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#267
by
AncientU
on 16 May, 2017 17:06
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That doesn't include the plane change of 4 degrees, does it?
Seems to only assume the launch site was at 24.5, not 28.5.
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#268
by
Dante80
on 16 May, 2017 17:08
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Yes, but it still processes the inc+circ delta V needed for GSO circular. That is the point I think (how much work does the payload have to do until it gets to operational orbit).
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#269
by
envy887
on 16 May, 2017 17:13
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Yes, but it still processes the inc+circ delta V needed for GSO circular. That is the point I think (how much work has the payload to do until it gets to operational orbit).
After circ the period should be 24h and the drift 0. It looks like that calc is to circ at 70k, not at GEO.
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#270
by
stcks
on 16 May, 2017 17:14
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#271
by
Dante80
on 16 May, 2017 17:16
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Yep, I did this wrong.
Many thanks for the prompt answers..C:
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#272
by
gongora
on 16 May, 2017 17:16
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Pretty good performance. 70k apogee + an inclination reduction.
This one looks to have been a hotter performer than previous Falcon 9s. I'm becoming more convinced that this is an upgraded variant.
- Ed Kyle
Possibly, but we've also probably never seen max performance from a previous Falcon 9.
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#273
by
Dante80
on 16 May, 2017 17:21
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Pretty good performance. 70k apogee + an inclination reduction.
This one looks to have been a hotter performer than previous Falcon 9s. I'm becoming more convinced that this is an upgraded variant.
- Ed Kyle
Possibly, but we've also probably never seen max performance from a previous Falcon 9.
Not for v1.2. We have seen a depletion burn on Thaicom 6 with v1.1 (3,016kg, 295kmx90,000kmx22.5°). It was the one that USAF criticized for unacceptable residual margins at the end of the burn.
Two years later, v1.2 did an almost identical insertion with Thaicom 8 and then landed on the barge. It is a beast.
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#274
by
Billium
on 16 May, 2017 17:58
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So assuming that this is max performance for the F9, at least for the moment, and as noted above by others, a 6,070 KG payload to GTO-1570, does this give us a clue what the max payload would for a GTO launch? I seem to recall seeing GTO-1800 is acceptable for customers. I don't have the knowledge to either know that GTO-1800 is ok, or the math to work backwards to get the payload. I would be interested on any thoughts by those more knowledgeable than I. I also wonder what portion of commercial payloads would exceed the mass we now think F9 is capable of. It seems like a smaller portion is restricted to the competition.
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#275
by
envy887
on 16 May, 2017 18:16
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So assuming that this is max performance for the F9, at least for the moment, and as noted above by others, a 6,070 KG payload to GTO-1570, does this give us a clue what the max payload would for a GTO launch? I seem to recall seeing GTO-1800 is acceptable for customers. I don't have the knowledge to either know that GTO-1800 is ok, or the math to work backwards to get the payload. I would be interested on any thoughts by those more knowledgeable than I. I also wonder what portion of commercial payloads would exceed the mass we now think F9 is capable of. It seems like a smaller portion is restricted to the competition.
The same performance would put 6820 kg to GEO-1800, assuming the stage dry mass if 4500 kg and MVac I_sp is 348 seconds.
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#276
by
envy887
on 16 May, 2017 18:18
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#277
by
John Alan
on 16 May, 2017 18:21
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So assuming that this is max performance for the F9, at least for the moment, and as noted above by others, a 6,070 KG payload to GTO-1570, does this give us a clue what the max payload would for a GTO launch? I seem to recall seeing GTO-1800 is acceptable for customers. I don't have the knowledge to either know that GTO-1800 is ok, or the math to work backwards to get the payload. I would be interested on any thoughts by those more knowledgeable than I. I also wonder what portion of commercial payloads would exceed the mass we now think F9 is capable of. It seems like a smaller portion is restricted to the competition.
The same performance would put 6820 kg to GEO-1800, assuming the stage dry mass if 4500 kg and MVac I_sp is 348 seconds.
So we are still no where near the 8300kg promise land... Figures...
Ref
http://www.spacex.com/falcon9
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#278
by
JBF
on 16 May, 2017 18:35
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So assuming that this is max performance for the F9, at least for the moment, and as noted above by others, a 6,070 KG payload to GTO-1570, does this give us a clue what the max payload would for a GTO launch? I seem to recall seeing GTO-1800 is acceptable for customers. I don't have the knowledge to either know that GTO-1800 is ok, or the math to work backwards to get the payload. I would be interested on any thoughts by those more knowledgeable than I. I also wonder what portion of commercial payloads would exceed the mass we now think F9 is capable of. It seems like a smaller portion is restricted to the competition.
The same performance would put 6820 kg to GEO-1800, assuming the stage dry mass if 4500 kg and MVac I_sp is 348 seconds.
So we are still no where near the 8300kg promise land... Figures...
Ref http://www.spacex.com/falcon9
8300 is the GTO figure.
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#279
by
rsdavis9
on 16 May, 2017 18:50
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This was NOT a flight to GTO! This used a super-synchronous transfer orbit.
Don't the parameters at insertion (315 km altitude, 10,025 m/s velocity) indicate a subsynchronous transfer orbit?
I calculated it naively with the elliptical orbit and got almost exactly a apogee of geo sync. i.e. 35786 km above earth surface.
v=(u*(2/r-1/a))^.5
u=GM
r=perigee from center of earth
a=semimajor axis
Velocity seems relative to launch site, since it's 0 at launch and not 408 m/s. Adding this in, you get an inertial frame speed of 10435, for a apogee of about 62000 km, or super-synchronous.
Using the posted picture in the update thread after SECO-2 we have 4 data points of R (above ground) and V:
315km - 10025m/s,
321km - 36060km/h=10017m/s
420km - 35770km/h=9936m/s
486km - 35561km/h=9878m/s
using the formular above with GM=3.98438E14 and an Earth radius of 6371km I get an average semimajor axis of about 21340+-50km or Apogee of ~ 29552km.
Adding the 408m/s to V I get an average semimajor axis of 38407+-125km or Apogee of ~ 63688km.
Do smaller errors of the first set hint that it is wrong to add 408m/s? Yet the apogee would be well below GEO strongly suggesting that the later is the better aproximation.
The question for me remains with this analysis what V really is, velocity along the flight path or relative to ground below the stage or relative to launch site?
Edit the TLEs posted show that adding 408m/s seems to be the right way to do it.
I find it amazing when playing with this formula that the difference of 408m/s(the earths veloicty at the cape) is enough to make a difference between GEO of 42000km and 60000 geo super sync.
Many thanks for the prompt answers..C:
