SpaceX Falcon 9 : Telstar 19 Vantage : July 22, 2018 - DISCUSSION

[ugordan]

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.

[eriblo]

2018-059A/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
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.

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.

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.

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 warning

[jcm]

2018-059A/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
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.

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.

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.

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 warning

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.

[SpaceGoo]

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?

[Sam Ho]

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.

[envy887]

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?

The extra payload mass is only a tiny fraction of the vehicle mass at staging.

[ZachF]

GTO-2275 @7075kg would back calculate to ~5,600 kg to GTO-1800... Which is also the official SpaceX number IIRC.

[GWR64]

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

[soltasto]

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.

[vaporcobra]

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°.

[SpaceGoo]

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.

[gongora]

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.

[marsbase]

  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. 

[Comga]

  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. 

And rockets 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. 

[Pete]

  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.

[rower2000]

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.

The customer will calculate

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.

[soltasto]

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

[codav]

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.

[marsbase]

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.

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.

[ZachS09]

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.