SpaceX Falcon 9 : Intelsat 35e : July 5, 2017 : DISCUSSION

[envy887]

I am pretty sure this was the fastest turn around for Pad 39A, correct?  The Gemini launches for 7 and 6 were faster for any pad correct?   Or has there been a faster turnaround anywhere else?

Nope. They missed it when they didn't launch on Monday. If I remember the post from somewhere upthread the record is SkyLab 1 and 2.

Any pad at the Eastern range? Or anywhere? The Russians have turned around a pad much faster, less than 24 hours.

[Jdeshetler]

Any pad at the Eastern range? Or anywhere? The Russians have turned around a pad much faster, less than 24 hours.

Or they will be send to gulag to northeastern Siberia...

[Lars-J]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

[StuffOfInterest]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

Does that mean they will actually need to lower the apogee to circularize the orbit?  Seems like that is almost overdoing it.  Why not keep a little more fuel for the second burn to raise the perigee?

[launchwatcher]

I am pretty sure this was the fastest turn around for Pad 39A, correct?  The Gemini launches for 7 and 6 were faster for any pad correct?   Or has there been a faster turnaround anywhere else?

Nope. They missed it when they didn't launch on Monday. If I remember the post from somewhere upthread the record is SkyLab 1 and 2.

This is still the fastest turnaround of pad 39A; the skylab launches used both pads.

Skylab 1 (Saturn V lifting the station) launched from 39A on May 14, 1973.
Skylab 2 (Saturn 1B lifting the first crew) launched from 39B on May 25, 1973, 11 days later.

[Lars-J]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

Does that mean they will actually need to lower the apogee to circularize the orbit?  Seems like that is almost overdoing it.  Why not keep a little more fuel for the second burn to raise the perigee?

No, the higher apogee is actually a net gain since it makes the inclination change maneuver easier. It seems counter-intuitive, but it is true. This is commonly called a super-synchronous transfer orbit, and is discussed here: https://forum.nasaspaceflight.com/index.php?topic=33731.0

[launchwatcher]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

Interesting that a subsynchronous transfer orbit (GEO is ~35,700km above sea level, right?) would have been acceptable...

[cppetrie]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

Nice job Lou. Not a bad estimate at all based on the empirical data we had.

We know this is a burn to depletion, targeting 26^o.  What should we expect?

Compare to Inmarsat.  That put 6086 kg into a 70K km apogee, 24.5^o orbit, needing minimal GTO+377m/s.

Plugging in the new mass of 6761 kg, second stage estimates (ISP=348, empty mass 4.5t, fuel 111.5t), plus  a small first stage loss, gives a total delta V of 202 m/s less.  So it should still reach GTO, but with only 175 m/s left over.  Adding in the final inclination of 26^o, we get an apogee of 48K km, with a delta-V remaining to GEO of about 1700 m/s.

Of course since this is a burn to depletion, dispersions could be quite large  (the apogee spec is 31K km, or greater).  But if it performs as well as the last one, it will be super-synchronous and Intelsat will get a good deal.

[cppetrie]

I am pretty sure this was the fastest turn around for Pad 39A, correct?  The Gemini launches for 7 and 6 were faster for any pad correct?   Or has there been a faster turnaround anywhere else?

Nope. They missed it when they didn't launch on Monday. If I remember the post from somewhere upthread the record is SkyLab 1 and 2.

This is still the fastest turnaround of pad 39A; the skylab launches used both pads.

Skylab 1 (Saturn V lifting the station) launched from 39A on May 14, 1973.
Skylab 2 (Saturn 1B lifting the first crew) launched from 39B on May 25, 1973, 11 days later.

I stand corrected. I misread this post below citing fastest turnaround at Kennedy.

Not actually official yet, but the way KSC is acting on the notes of roadblocks and preps suggests they are deep into activating the 24 hour scrub turnaround, so another attempt today. Caveat is they can take it down to polling points, so yeah - but let's go with another attempt until we hear different.

A launch tonight and this would still be the shortest time between two launches from Kennedy. Any further delay and the gap from BulgariaSat-1 will be longer than that between Skylab 1 and Skylab 2 (i.e. Skylab itself and its first crew) in May 1973.

[LouScheffer]

Looks like they squeezed as much performance from this F9 as they could: 

https://twitter.com/elonmusk/status/882761133177790464

Elon Musk‏ @elonmusk
Thanks @INTELSAT! Really proud of the rocket and SpaceX team today. Min apogee requirement was 28,000 km, Falcon 9 achieved 43,000 km.

Interesting that a subsynchronous transfer orbit (GEO is ~35,700km above sea level, right?) would have been acceptable...

They loaded extra fuel to account for this possibility and still get full life for the satellite.  In general this is a winning strategy if you have room in the satellite tanks for more fuel.  You get less delta-V from the booster, because of the increased mass, but you more than make up for it by more delta-V from the satellite.   That's because the satellite engine is only pushing about half the mass (satellite only, as opposed to satellite + upper stage).

[rickl]

I am pretty sure this was the fastest turn around for Pad 39A, correct? 

Chris Gebhardt said in the update thread that it is, and it's the second time this year that SpaceX has broken the record for the fastest turnaround at 39A.  (For some reason I can't quote his comment here.)

This is the eighth launch from 39A this year, which I'm pretty sure sets a record.  Wikipedia lists nine Shuttle launches in 1985, but doesn't say whether they were from 39A or B.  I'd bet that some were from 39B.

[Sam Ho]

This is the eighth launch from 39A this year, which I'm pretty sure sets a record.  Wikipedia lists nine Shuttle launches in 1985, but doesn't say whether they were from 39A or B.  I'd bet that some were from 39B.

39B was not in use in 1985. The first use of 39B in the Shuttle era was STS-51L.

[Ronpur50]

I am pretty sure this was the fastest turn around for Pad 39A, correct? 

Chris Gebhardt said in the update thread that it is, and it's the second time this year that SpaceX has broken the record for the fastest turnaround at 39A.  (For some reason I can't quote his comment here.)

This is the eighth launch from 39A this year, which I'm pretty sure sets a record.  Wikipedia lists nine Shuttle launches in 1985, but doesn't say whether they were from 39A or B.  I'd bet that some were from 39B.

Not in 1985.  Pad B had it's first launch with Challenger 51-L in 1986.  So almost at that record.

[mheney]

I am pretty sure this was the fastest turn around for Pad 39A, correct? 

Chris Gebhardt said in the update thread that it is, and it's the second time this year that SpaceX has broken the record for the fastest turnaround at 39A.  (For some reason I can't quote his comment here.)

This is the eighth launch from 39A this year, which I'm pretty sure sets a record.  Wikipedia lists nine Shuttle launches in 1985, but doesn't say whether they were from 39A or B.  I'd bet that some were from 39B.

Challenger's ill-fated STS-51L flight was the first to launch from Pad 39B in January 1986.  So all 9 shuttle launches in 1985 would have been from 39A.

[rickl]

OK, thanks for the correction.  It looks like SpaceX will break the record this year if everything goes well (fingers crossed). 

Like I said in my congratulatory post, SpaceX launches are never boring to me.  I hold my breath until it reaches orbit.  I still remember CRS-7.  Things can go sideways in a hurry.

[edkyle99]

Challenger's ill-fated STS-51L flight was the first to launch from Pad 39B in January 1986.  So all 9 shuttle launches in 1985 would have been from 39A.

We tried, really hard, to launch more Shuttles that year (1985), but there were scrubs and rollbacks and delays, etc.  SpaceX is doing this year what NASA wanted Shuttle to do back then, except for the crewed launches. 

At 10 launches so far this year, Falcon 9 becomes the first U.S. launch vehicle to fly 10 times in a calendar year successfully since Delta 2 did it in 1999, 18 years ago.  With three more launches, Falcon 9 will have us digging into the 1970s launch lists for comparison.  One or two more after that, and we'll be looking at 1960s numbers.

Of course none of those frequent flyers in those days could lift 6.761 tonnes to GTO.

 - Ed Kyle

[burningsheep]

I was wondering if anyone could educate me on the reason for using a parking orbit and then a 2nd burn over Africa to get to GTO instead of a single direct burn? Here's what I think happened:

On the webcast the speed dropped about 500Km/h and the altitude went up to 248km from 164Km during the coast; so my guess is that once they achieved a LEO orbit, they waited to hit apogee where a perigree raising burn is most efficient and then they burnt a minute to raise that perigree to a new apogee of 43000Km, and the new perigree will be approximately where they started the 2nd burn around 250km?

Does that make sense? Thanks in advance!

[Lars-J]

I was wondering if anyone could educate me on the reason for using a parking orbit and then a 2nd burn over Africa to get to GTO instead of a single direct burn? Here's what I think happened:

On the webcast the speed dropped about 500Km/h and the altitude went up to 248km from 164Km during the coast; so my guess is that once they achieved a LEO orbit, they waited to hit apogee where a perigree raising burn is most efficient and then they burnt a minute to raise that perigree to a new apogee of 43000Km, and the new perigree will be approximately where they started the 2nd burn around 250km?

Does that make sense? Thanks in advance!

No, that's not the reason. Inclination changes are most efficient over the equator, which is why the 2nd burn is done there. (which raises the apogee and simultaneously changes the inclination)

Single direct burns for GTO are only practical when launching from a near equator launch site.

[luinil]

I was wondering if anyone could educate me on the reason for using a parking orbit and then a 2nd burn over Africa to get to GTO instead of a single direct burn? Here's what I think happened:

On the webcast the speed dropped about 500Km/h and the altitude went up to 248km from 164Km during the coast; so my guess is that once they achieved a LEO orbit, they waited to hit apogee where a perigree raising burn is most efficient and then they burnt a minute to raise that perigree to a new apogee of 43000Km, and the new perigree will be approximately where they started the 2nd burn around 250km?

Does that make sense? Thanks in advance!

I'd guess that you'd want the apogee to be in a place the will put the satellite at the right geographic position when you circularize the orbit.

[Lars-J]

I was wondering if anyone could educate me on the reason for using a parking orbit and then a 2nd burn over Africa to get to GTO instead of a single direct burn? Here's what I think happened:

On the webcast the speed dropped about 500Km/h and the altitude went up to 248km from 164Km during the coast; so my guess is that once they achieved a LEO orbit, they waited to hit apogee where a perigree raising burn is most efficient and then they burnt a minute to raise that perigree to a new apogee of 43000Km, and the new perigree will be approximately where they started the 2nd burn around 250km?

Does that make sense? Thanks in advance!

I'd guess that you'd want the apogee to be in a place the will put the satellite at the right geographic position when you circularize the orbit.

No, the final position is easy to adjust during the perigee raising burns later. (which is done through many orbits) It is easy for a satellite to drift slowly to its final position by a slight raising or lowering its orbit.

You may note that all of SpaceX GTO launches make the second burn as the upper stage passes the equator. This is because it is the most effective spot (the equator) to deliver the satellite to its transfer orbit. The final satellite position is irrelevant for this step.