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

[deruch]

Insprucker said they were bringing in the LOX loading time and will continue to tune (I held by breath). The other think I noticed was a call out for "cyro-helium stir" very late into the countdown. Has anyone heard this before? Stratification mitigation in the COPVs?

If you listen closely, I believe you'll hear that this is actually "Stage 1, Stage 2 Cryo-helium secured" and not "stir".  Which I assume just means that they have stopped loading He and closed all appropriate valves prior to launch.

[nacnud]

A vid of what I think is the fairing after sep. Interestingly you can see the tiles inflating over time, starts on the left and moves right. Is it getting cooked or is something else happening?

https://www.instagram.com/p/BUK6BQnBNuK/

[Space Ghost 1962]

They might be swelling as moisture bakes out. Perhaps just ... warping (meniscus or potato chip).

I think they're hygroscopic?

[deruch]

There were a few frames of the LOX tank view right before they lost signal during the coast.  I was finally able to screencap one from Youtube by using <comma> and <period> to go frame-by-frame.

[launchwatcher]

A vid of what I think is the fairing after sep. Interestingly you can see the tiles inflating over time, starts on the left and moves right. Is it getting cooked or is something else happening?

https://www.instagram.com/p/BUK6BQnBNuK/

They seem to have stabilized the fairing...  compare with the roll rates in the first fairing video:

[TrueBlueWitt]

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

Roughly a 1,570m/s deficit to GTO. That's almost Zenit-3SLB/Proton-M/Briz-M performance.

Those have more stages too. Not bad for kerolox 2 stage.

You mean Zenit-3SL(not B)  Correct?

[Space Ghost 1962]

Correct. The three stage. The 2 is a two stage, the 3 is a three stage, the B/M is launched from Kazahstan, the SL is from the SeaLaunch platform near the equator.

add:

Block DM-SL third stage.

[TrueBlueWitt]

Correct. The three stage. The SLB/M is a two stage.

I thought the 3SL and 3SLB were basically the same.. just SL went from Equatorial(Sea Launch) and 3SLB from Baikonur (with corresponing huge dV hit to GTO).  From what I saw, 3SLB is only good for around 3750kg to GTO.

[LouScheffer]

Does anyone really think a burn terminated almost exactly at 36,000km/hr was a burn to minimum residuals?  Seems very unlikely.  Probably close, but still a little gas left in the tank.

Well, Michele Franci, the CTO of Inmarsat, really thinks so.  From Falcon 9 set to launch Inmarsat satellite for in-flight wifi, mobile broadband:

Parameters for the target orbit are not available, he said, because the upper stage engine is programmed to keep firing until it is almost out of fuel, a technique rocket engineers call a “minimum residual shutdown.” The tank-draining burn is intended to ensure the Inmarsat 5 F4 satellite goes into as high of an orbit as possible, reducing the work the craft’s own thrusters need to do in the coming months.

[abaddon]

Well, there you go .  Nice find!  Guess it was a case of the unlikely seeming round number.

[Jdeshetler]

There were a few frames of the LOX tank view right before they lost signal during the coast.  I was finally able to screencap one from Youtube by using <comma> and <period> to go frame-by-frame.

Cool, here is an animate gif, only 2 frames....

[envy887]

Data over in the Falcon Simulations thread definitely shows this booster was run at a higher thrust than SES-10. Altitude and velocity were both higher at every point in the boost.

[macpacheco]

There are multiple reports of two unnamed sources stating that the last two F9 launches were Block III booster + Block IV upper stage.
So, if that's true, what would be the effect of a Block IV booster with the same thrust upgrade ?
Is it enough for another 200Kg to GTO-1800 capability ?

[Dante80]

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

Roughly a 1,570m/s deficit to GTO. That's almost Zenit-3SLB/Proton-M/Briz-M performance.

How is that a deficit to GTO? It is almost twice as high as a standard GTO orbit.
Or am I missing something?
And what do you mean with almost Zenit/Proton performance?

Zenit 3SL running from the equator can do around 6 tons to GTO-1500. Proton M+ (enhanced) can do around 6.3 tons.

Both use 3 stages to get there (Blok D and Briz M accordingly).

[Robotbeat]

Is Falcon 9 the highest performance two stage rocket currently flying to GTO? Or ever?

I do believe everything else has to use strap on boosters &/or multiple stages to get this performance.

[Dante80]

Rockets designed/converted for GTO missions tend to use a third and/or fourth stage (or LRB/SRBs). Falcon 9 has been designed differently, using an abnormally large second stage (and second stage engine).

It will be the most powerful TSTO LV for GTO missions until New Glenn flies (and assuming that the two stage NG will be used for GTO campaigns, something that is not certain - Blue have talked about an optional BE-3U third stage for high energy missions).

[guckyfan]

Without any calculations done. Even if not very efficient, the raw power of New Glenn should get a GEO com sat to GTO in its 2 stage configuration. Everything else would make launches quite expensive.

[Steven Pietrobon]

Here's a higher resolution capture of Stage 2 LOX tank.

[baldusi]

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

Roughly a 1,570m/s deficit to GTO. That's almost Zenit-3SLB/Proton-M/Briz-M performance.

How is that a deficit to GTO? It is almost twice as high as a standard GTO orbit.
Or am I missing something?
And what do you mean with almost Zenit/Proton performance?

Zenit 3SL running from the equator can do around 6 tons to GTO-1500. Proton M+ (enhanced) can do around 6.3 tons.

Both use 3 stages to get there (Blok D and Briz M accordingly).

Zenit-3SL can do 6.16 to a 1,477m/s deficit GTO. That's a ~95m/s difference. If they used less delta-v GTO, and they didn't had structural limits on the rocket, it would be much higher performance. Using a linear approximation I get 7.8 tonnes.

[BabaORileyUSA]

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

Roughly a 1,570m/s deficit to GEO. That's almost Zenit-3SL/Proton-M/Briz-M performance.

Just a question about your sign convention:  how can the DEFICIT to GEO be this large, when this mission used a super-synchronous transfer orbit?  It would seem to have a significantly smaller deficit, since the semi-major axis is much closer to GEO than a standard Hohmann GTO, or indeed, even the S/C separation orbit of a Briz-M for a payload of equal mass... isn't the energy of the orbit a function of semi-major axis?