Author Topic: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION  (Read 206975 times)

Offline Wolfram66

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

Offline Shanuson

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #261 on: 05/16/2017 04:36 pm »

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.

Offline hans_ober

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #262 on: 05/16/2017 04:41 pm »
Pretty good performance. 70k apogee + an inclination reduction.

Offline AncientU

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #263 on: 05/16/2017 04:44 pm »
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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Offline edkyle99

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #264 on: 05/16/2017 04:46 pm »
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
« Last Edit: 05/16/2017 04:47 pm by edkyle99 »

Offline stcks

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #265 on: 05/16/2017 04:49 pm »
Pretty good performance. 70k apogee + an inclination reduction.

Excellent performance. GTO-1570.

Offline Dante80

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #266 on: 05/16/2017 04:52 pm »
Pretty good performance. 70k apogee + an inclination reduction.

Excellent performance. GTO-1570.

I'm getting this from the calc. Am I putting something wrong in?

http://www.satsig.net/orbit-research/delta-v-geo-injection-calculator.htm

« Last Edit: 05/16/2017 04:55 pm by Dante80 »

Offline AncientU

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #267 on: 05/16/2017 05:06 pm »
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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Offline Dante80

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #268 on: 05/16/2017 05:08 pm »
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).
« Last Edit: 05/16/2017 05:13 pm by Dante80 »

Offline envy887

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #269 on: 05/16/2017 05:13 pm »
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.

Offline stcks

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #270 on: 05/16/2017 05:14 pm »
I'm getting this from the calc. Am I putting something wrong in?

http://www.satsig.net/orbit-research/delta-v-geo-injection-calculator.htm

I don't know what algorithm that site is using, but I'm using this: https://www.reddit.com/r/spacex/wiki/launches/gto_performance and here is the code: https://gist.github.com/anonymous/aa3397ea848d2e2d6986804f027e286e

This is a Lou Scheffer approved method. (See https://forum.nasaspaceflight.com/index.php?topic=36954.0 from which is based). I dont trust that site, and it seems neither does he.
« Last Edit: 05/16/2017 05:15 pm by stcks »

Offline Dante80

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #271 on: 05/16/2017 05:16 pm »
Yep, I did this wrong.  :-[ Many thanks for the prompt answers..C:

Offline gongora

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #272 on: 05/16/2017 05:16 pm »
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.

Offline Dante80

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #273 on: 05/16/2017 05:21 pm »
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.
« Last Edit: 05/16/2017 05:25 pm by Dante80 »

Offline Billium

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #274 on: 05/16/2017 05:58 pm »
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.

Offline envy887

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #275 on: 05/16/2017 06:16 pm »
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.

Offline envy887

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #276 on: 05/16/2017 06:18 pm »
I'm getting this from the calc. Am I putting something wrong in?

http://www.satsig.net/orbit-research/delta-v-geo-injection-calculator.htm

I don't know what algorithm that site is using, but I'm using this: https://www.reddit.com/r/spacex/wiki/launches/gto_performance and here is the code: https://gist.github.com/anonymous/aa3397ea848d2e2d6986804f027e286e

This is a Lou Scheffer approved method. (See https://forum.nasaspaceflight.com/index.php?topic=36954.0 from which is based). I dont trust that site, and it seems neither does he.

That calculator works fine for a single elliptic transfer. But super-sync or sub-sync requires a bi-elliptic transfer, which it can't handle.

Offline John Alan

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #277 on: 05/16/2017 06:21 pm »
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
« Last Edit: 05/16/2017 06:33 pm by John Alan »

Offline JBF

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Re: SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION
« Reply #278 on: 05/16/2017 06:35 pm »
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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Online rsdavis9


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.
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