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#100 by ugordan on 22 Jul, 2018 15:54
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No word yet on T19V health - should have had something by now ? I may have missed it - I just don't see any news on health
https://twitter.com/pbdes/status/1020932323771146240
Manufacturer @sslmda @sslmda @MaxarTech reports #Telesat Telstar 19V sat is healthy in orbit after separation from @SpaceX Falcon 9. -
#101 by eriblo on 22 Jul, 2018 16:07
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Running solasto's implementation doesn't give any errors but I think it spits out a perigee speed that is lower than the apogee speed after the first burn and a corresponding negative delta v. This could be taken as a warning2018-059A/43562 (243 km x 17863 km x 27.00°) has a delta v to GTO of 2064.5751 m/s or it is in GTO-2065
What parameters did you use? I get 2277 m/s using that approach (which seems to agree with this online implementation)...? BTW, doing a third of a degree of the inclination change in the first apogee raising burn saves ~4 m/s.
2018-059B/43563 (242 km x 17860 km x 27.00°) has a delta v to GTO of 2064.7341 m/s or it is in GTO-2065
according to my C/C++ program based on this.
I used the TLE data along with the program written by LouScheffer. I literally "translated" that program.
This is the program, it should compile with GCC using C++11:
...
Unfortunately, that program is only correct for synchronous or greater. It does not account for the perigee burn to raise the apogee, gets the wrong sign for circularization if the apogee is below GEO, and will do the inclination reduction at the wrong burn if sub-sync. So the numbers from this program will be wrong for the sub-sync case, which this is. Sorry, it should check for that and either do it right, or at least give a message, rather than silently doing it wrong.
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#102 by jcm on 22 Jul, 2018 16:18
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Running solasto's implementation doesn't give any errors but I think it spits out a perigee speed that is lower than the apogee speed after the first burn and a corresponding negative delta v. This could be taken as a warning2018-059A/43562 (243 km x 17863 km x 27.00°) has a delta v to GTO of 2064.5751 m/s or it is in GTO-2065
What parameters did you use? I get 2277 m/s using that approach (which seems to agree with this online implementation)...? BTW, doing a third of a degree of the inclination change in the first apogee raising burn saves ~4 m/s.
2018-059B/43563 (242 km x 17860 km x 27.00°) has a delta v to GTO of 2064.7341 m/s or it is in GTO-2065
according to my C/C++ program based on this.
I used the TLE data along with the program written by LouScheffer. I literally "translated" that program.
This is the program, it should compile with GCC using C++11:
...
Unfortunately, that program is only correct for synchronous or greater. It does not account for the perigee burn to raise the apogee, gets the wrong sign for circularization if the apogee is below GEO, and will do the inclination reduction at the wrong burn if sub-sync. So the numbers from this program will be wrong for the sub-sync case, which this is. Sorry, it should check for that and either do it right, or at least give a message, rather than silently doing it wrong.
Doing a rough calculation by hand I got about 2200 m/s with a 500 m/s perigee burn to standard GTO and
about 1700 m/s from there. -
#103 by SpaceGoo on 22 Jul, 2018 16:26
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Since TerreStar 1 was the previous record holder for largest commercial spacecraft to GEO and launched by Ariane Space to a geosynchronous transfer orbit, I am curious how the delta v compares to Telstar 19. Does anyone know the delta v for TerreStar 1?
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#104 by Sam Ho on 22 Jul, 2018 17:30
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Since TerreStar 1 was the previous record holder for largest commercial spacecraft to GEO and launched by Ariane Space to a geosynchronous transfer orbit, I am curious how the delta v compares to Telstar 19. Does anyone know the delta v for TerreStar 1?
Terrestar 1 was a standard GTO from Kourou, so GEO-1500 m/s. -
#105 by envy887 on 22 Jul, 2018 17:33
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The extra payload mass is only a tiny fraction of the vehicle mass at staging.First stage cutoff was at 8170 km/hr = 2270 m/s.
This is exactly what we've seen on previous GTO with recovery missions. So no big performance boost for block 5.
You don't consider the fact that they did this with a payload in excess of SEVEN TONS, as significant? -
#106 by ZachF on 22 Jul, 2018 17:59
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GTO-2275 @7075kg would back calculate to ~5,600 kg to GTO-1800... Which is also the official SpaceX number IIRC.
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#107 by GWR64 on 22 Jul, 2018 18:23
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GTO-2275 @7075kg ...
gives about 3450 kg at BOL, (speculation, imp: 323s, aerojet hipat engine with MMH )
compare to Echostar 19, also a SSL-1300 Satellite, has a dry mass of 3497 kg -
#108 by soltasto on 22 Jul, 2018 21:03
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I decided to rewrite the code from scratch to fix the issue and to write it in good C++, but I decided to also add a feature that finds the most efficient way to GEO. So now it will also scrub some of the inclination at perigee, just as much to reduce the total delta v budget.
Here is the github repository: https://github.com/AleLovesio/delta-v-to-GTO (The source files are in the source folder)
I also uploaded the files here as txts since the cpp and h extensions are not allowed even if in the end they are just text files.
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#109 by vaporcobra on 22 Jul, 2018 23:24
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I decided to rewrite the code from scratch to fix the issue and to write it in good C++, but I decided to also add a feature that finds the most efficient way to GEO. So now it will also scrub some of the inclination at perigee, just as much to reduce the total delta v budget.
Here is the github repository: https://github.com/AleLovesio/delta-v-to-GTO (The source files are in the source folder)
I also uploaded the files here as txts since the cpp and h extensions are not allowed even if in the end they are just text files.
Could you compare with JCSAT-16? It's a close match telemetry-wise, but the final orbit from F9 was 184 km × 35,912 km × 20.85°. -
#110 by SpaceGoo on 23 Jul, 2018 02:35
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Since TerreStar 1 was the previous record holder for largest commercial spacecraft to GEO and launched by Ariane Space to a geosynchronous transfer orbit, I am curious how the delta v compares to Telstar 19. Does anyone know the delta v for TerreStar 1?
Terrestar 1 was a standard GTO from Kourou, so GEO-1500 m/s.
Thanks. I thought it would be interesting to compare Terrestar 1 to Telstar 19 since they have equivalent mass and SpaceX landed the first stage. A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
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#111 by gongora on 23 Jul, 2018 02:50
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Since TerreStar 1 was the previous record holder for largest commercial spacecraft to GEO and launched by Ariane Space to a geosynchronous transfer orbit, I am curious how the delta v compares to Telstar 19. Does anyone know the delta v for TerreStar 1?
Terrestar 1 was a standard GTO from Kourou, so GEO-1500 m/s.
Thanks. I thought it would be interesting to compare Terrestar 1 to Telstar 19 since they have equivalent mass and SpaceX landed the first stage. A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
SpaceX isn't "wasting" fuel on reuse. They sell a particular amount of performance at a good price and get to reuse their vehicle. If you want to pay twice as much they'll give you the full performance of the rocket for a price similar to what most of the other launch providers charge. -
#112 by marsbase on 23 Jul, 2018 03:39
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A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
Fuel is cheap. Spacecraft are expensive. -
#113 by Comga on 23 Jul, 2018 04:28
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And rockets are expensiveA recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
Fuel is cheap. Spacecraft are expensive.
But if you are talking about the spacecraft, or the rocket, or the fuel, you are going to miss the point.
It’s a system. It needs a system solution.
They start with the subsystems they want on orbit
Then they figure out the best way to get them there in the fastest manner, with the least risk, balanced against the cost.
The SpaceX argument is that recovering the first stage is part of that optimization.
Telstar agreed.
And all the discussions of the heaviest geostationary are so much angels dancing on the head of a pin.
What we have mostly are the masses of the satellites plus their orbit insertion hardware.
You can argue all you want about whether they have one horn or two (Figure out that reference!) but there isn’t a real answer. With the propulsion system systems included, the metric is confused.
Or we just use the mass as the spacecraft separates from the rocket.
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#114 by Pete on 23 Jul, 2018 07:09
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A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
All that matters. *ALL* that matters, are:
1) Is the customer happy that their satellite was delivered where and how it was contracted to be?
and
2) Did the launcher gain benefit from providing this service?
The answers to this are yes, and yes. -
#115 by rower2000 on 23 Jul, 2018 08:09
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The customer will calculateSince TerreStar 1 was the previous record holder for largest commercial spacecraft to GEO and launched by Ariane Space to a geosynchronous transfer orbit, I am curious how the delta v compares to Telstar 19. Does anyone know the delta v for TerreStar 1?
Terrestar 1 was a standard GTO from Kourou, so GEO-1500 m/s.
Thanks. I thought it would be interesting to compare Terrestar 1 to Telstar 19 since they have equivalent mass and SpaceX landed the first stage. A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
Cost of launch to GTO-xxxx + cost of raising GTO-xxxx to GTO := A + B = total cost of launch
If the cost difference for orbit raising from GTO-2275 to GTO instead of GTO-1500 or GTO-1800 to GTO is less expensive than the added cost of Ariane/ULA/Younameit for delivery to GTO-1500 or GTO-1800, then there is no wasted fuel included, just $$$ saved for the customer. -
#116 by soltasto on 23 Jul, 2018 09:14
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I decided to rewrite the code from scratch to fix the issue and to write it in good C++, but I decided to also add a feature that finds the most efficient way to GEO. So now it will also scrub some of the inclination at perigee, just as much to reduce the total delta v budget.
Here is the github repository: https://github.com/AleLovesio/delta-v-to-GTO (The source files are in the source folder)
I also uploaded the files here as txts since the cpp and h extensions are not allowed even if in the end they are just text files.
Could you compare with JCSAT-16? It's a close match telemetry-wise, but the final orbit from F9 was 184 km × 35,912 km × 20.85°.
This is what I get with those numbers:Current Orbit: 184.0000 km x 35912.0000 km x 20.8500 degrees;
Apogee Speed: 1590.7738 m/s; Perigee Speed: 10261.2798 m/s; delta v to this orbit: 0.0000
Super-sync transfer.
First maneuver:
Perigee changed to 35786km
Inclination changed to 0.0146 degrees
Current Orbit: 35786.0000 km x 35912.0000 km x 0.0146 degrees;
Apogee Speed: 3068.0452 m/s; Perigee Speed: 3077.2151 m/s; delta v to this orbit: 1679.4790
Second maneuver:
Apogee changed to 35786km
Inclination changed to 0.0146 degrees
Current Orbit: 35786.0000 km x 35786.0000 km x 0.0000 degrees;
Apogee Speed: 3074.9218 m/s; Perigee Speed: 3074.9218 m/s; delta v to this orbit: 1681.9025
Total delta v to GEO: 1681.9025 m/s -
#117 by codav on 23 Jul, 2018 12:33
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A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
Just a note on wasting fuel: if the satellite bus is large enough to hold a sizeable amount of fuel for orbit raising (understood the be about 3mt for Telstar 19V), it is way more efficient due to less overall mass to let the satellite raise itself to the final orbit than have the second stage do the job partially. It is just a tradeoff between the reduced cost of a reusable launch into a low-energy orbit or paying more for an expendable launch and gaining some additional years of in-orbit operations. -
#118 by marsbase on 23 Jul, 2018 13:52
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Yes. Another way to say it is that the satellite's propulsion system amounts to a thrid stage of the rocket. Drop the weight of the second stage empty tank and engine and keep going.A recurring argument recently is that SpaceX is wasting fuel on reuse versus getting the satellite at or nearer to GEO.
Just a note on wasting fuel: if the satellite bus is large enough to hold a sizeable amount of fuel for orbit raising (understood the be about 3mt for Telstar 19V), it is way more efficient due to less overall mass to let the satellite raise itself to the final orbit than have the second stage do the job partially. It is just a tradeoff between the reduced cost of a reusable launch into a low-energy orbit or paying more for an expendable launch and gaining some additional years of in-orbit operations. -
#119 by ZachS09 on 23 Jul, 2018 19:24
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It's possible that SpaceX used a Guidance-Commanded Shutdown for Stage 2 when the planned apogee was reached.
I ran this mission in Orbiter 2016 and let all the fuel in Stage 2 burn away, allowing a maximum apogee of 29,100 kilometers.
So, I think if SpaceX did a Minimum-Residual Shutdown for Stage 2, that apogee could have been reached.
