SpaceX Falcon 9 - Inmarsat 5 F4 - May 15, 2017 - DISCUSSION

[Robotbeat]

Why not count the dispenser? It's Iridium hardware. Seems to me everything forward of the Payload adapter should be considered payload even if it isn't technically deployed. It was still carried to space.

IIRC, SpaceX built it.  I disagree with Ed that it should not be counted as payload, at least when considering established lift capability of the rocket, as a different payload could use that mass for something else.

You are talking about something that ULA calls "Payload Systems Weight", which is a legitimate way to record things.  For Ariane 5 it means including Sylda 5, etc.  For other launches it includes the PAF, etc.  If you are using that method for Dragon, you would also have to add Dragon's adapter, etc.  That's all fine, but I'm interested in deployed payload because that is what matters in the rocket equation. 

 - Ed Kyle

Was the Iridium payload adapter on top of a regular payload adapter? If so, then it should be counted as payload. If it was in /place/ of the regular payload adapter, then you can count it as Stage 2. We're talking about the maximum payload mass a Falcon 9 has proven it could launch, and if the former is true, then it'd be factually incorrect to assert it has proven less.

[Mongo62]

- 36000 km/sec seems like an awfully round number.  Maybe not a burn to residual shutdown?

It also seems like an awfully fast number. 12% of the speed of light!

[abaddon]

You'd ideally count the custom dispenser mass minus the mass of a standard payload adapter.  The Iridium dispenser is much more massive in comparison.

[gongora]

Maybe this was a hardware Block 4 with Block 3 thrust, incremental deployment?

Has SpaceX ever said anything about what a "Block 4" would consist of, exactly?  We know Block 5 will have uprated thrust, just don't recall them ever saying much of anything about Block 4

Agreed, it's not been well explained.  I believe that Block 4 is up rated thrust, COPV solution. 

Block 5 is the reuseability upgrades, new legs, heat shield etc.

COPV fix was previously said to be in block 5, along with turbopump tweaks and the reuseability stuff.  The only thing we ever heard for block 4 was uprated thrust.

[abaddon]

There were two COPV fixes, one short term and one in Block 5.  Believe the latter was at request of NASA and maybe USAF.

[cppetrie]

There were two COPV fixes, one short term and one in Block 5.  Believe the latter was at request of NASA and maybe USAF.

I thought the NASA request related to long-term fixes for turbo-pump cracking.

[Robotbeat]

There were two COPV fixes, one short term and one in Block 5.  Believe the latter was at request of NASA and maybe USAF.

I thought the NASA request related to long-term fixes for turbo-pump cracking.

NASA tends to have lots of requests.

[cppetrie]

There were two COPV fixes, one short term and one in Block 5.  Believe the latter was at request of NASA and maybe USAF.

I thought the NASA request related to long-term fixes for turbo-pump cracking.

NASA tends to have lots of requests.

True story.

[sewebster]

Gabon AOS.

Libreville's not in business for this launch, I guess.

Isn't the tracking station near Libreville?

[ZachS09]

I think there are two different tracking stations in Gabon.

The regular Gabon station and the Libreville station. Unless they refer to Libreville as "Gabon".

[Lars-J]

A great launch! Watch out for the steamroller, it might be rounding the corner... 

(For those who do not get the reference, see this article: https://www.spaceintelreport.com/has-the-spacex-steamroller-finally-arrived )

[sewebster]

I think there are two different tracking stations in Gabon.

The regular Gabon station and the Libreville station. Unless they refer to Libreville as "Gabon".

Don't know. There seems to be this CNES one in Nkoltang:
http://www.esa.int/spaceinimages/Images/2014/05/Libreville_tracking_station_in_Gabon
Which I think they refer to as Libreville, since it is the larger city nearby.

[manoweb]

It could also have been for an abundance of caution in terms of giving information on speeds etc.

Actually it's the opposite, the previous launch gave a LOT of information on the first stage, this one FULL flight profile of the second stage from takeoff to the end. I have been extracting the data with an automated script in another thread

[Pete]

Is it just me, or have they trimmed down the time from MECO to Second stage Ignition even further?

Yes, they did not need to give the first stage time to get out of the blast zone, but it still felt like the speediest second stage startup I've yet seen?

[Ben the Space Brit]

The fastest MECO to SECO1 I've ever seen was so fast that you saw the Merlin VAC's exhaust plume hit the first stage and bounce off of the top dome of the LOX tank, focussed back towards the U/S by the interstage. I'm sure that it made an interesting bit of data about high-energy fluid dynamics in near-vacuum!

[input~2]

AFAICT no TLE published yet

[gospacex]

SpaceX's heaviest payloads to date. All were launched in 2017.
1. Iridium Next (1-10) - LEO (9,600 kg)
2. Inmarsat-5 F4 - GTO (6,070 kg)
3. EchoStar 23 - GTO (5,600 kg)

Dont forget about the Dragon launches. Those will be right in there near #1

Those are LEO launches [edit: Iridium and Dragon]. For LEO, ~10 tons is not much - it's only about half of what F9 can do.

[longboard1210]

If the plume pushed against the 1st stage would the intial aceleration be larger than straight into vaccum?

[curtquarquesso]

If the plume pushed against the 1st stage would the intial aceleration be larger than straight into vaccum?

No. A rocket engine's thrust is a result of it throwing many thousands of pounds of propellant out of the nozzle, opposite the desired direction of travel independent of whatever is behind it. Tom Mueller had a great practical example in his recent interview. A rocket engine works on the same principle as sitting in the back of the wagon, and throwing a brick out the back of it. You'll get a small impulse from throwing a brick opposite the direction you want to travel. If you could throw thousands of pounds of bricks out the back continuously, you'd move very, very quickly.

(mass of brick) * (acceleration experienced by brick being thrown by you) = (force of brick leaving your hand, pushing you and wagon forward)

F = Ma

[BabaORileyUSA]

SpaceX's heaviest payloads to date. All were launched in 2017.
1. Iridium Next (1-10) - LEO (9,600 kg)
2. Inmarsat-5 F4 - GTO (6,070 kg)
3. EchoStar 23 - GTO (5,600 kg)

Dont forget about the Dragon launches. Those will be right in there near #1

Those are LEO launches. For LEO, ~10 tons is not much - it's only about half of what F9 can do.

This was NOT a flight to GTO!  This used a super-synchronous transfer orbit.