Author Topic: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION  (Read 1087845 times)

Offline mvpel

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #680 on: 02/15/2016 05:10 pm »
Here's the FCC STA for the launch (F9-22), which doesn't include the ASDS radios:

https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=68937&RequestTimeout=1000
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Offline cscott

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #681 on: 02/15/2016 05:24 pm »
Is it possible that the ASDS recovery zone is so far out to sea that we've entered international waters and left fcc jurisdiction?

The notice to mariners is not US-specific, but the above hazard map looks to be specific to the Cape.  We'll see if there's a more comprehensive hazard warning issued by the coast guard.

Offline Jcc

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #682 on: 02/15/2016 08:27 pm »
Dumb question:
People are so used to thinking about what is required to get out of the atmosphere fast then they might not have much background for what is required here.
Maybe some brainstorming is required to list unlikely variables and there are plenty of people on this site like me with no credibility to lose and can provide the raw material:
If the purpose of the reentry burn is bow shock modification rather than direct  velocity reduction then could other behaviours be at play?
Unfortunately the only variable I can think they have to play with is the fuel mixture (more RP1 less O2) and its interaction with the tenuous hypersonic air and can't see why that would make any difference. Is it possible to pulse fire these engines?
Any other variables possible - ?

SpaceX has several optimization objectives to fulfill one goal, that is, to get the stage back intact and suitable for reuse with the minimum impact to the mission in terms of reserved fuel and lift capacity.

Optimization objectives include RTLS with minimum fuel for boostback if RTLS, or land down range (objective 1). That takes place above the atmosphere, where the bow shock is not an issue. For reentry, they need to avoid damage due to excessive heating and pressure (objective 2), but they do want to maximize the effect of atmospheric resistance to slow the stage (objective 3), and of course by the end  of the reentry burn the stage must still be decelerating to terminal velocity, not speeding up again due to gravity, so it has to occur in the atmosphere. Here, maximizing the bow shock is  desirable and they probably want to adjust the thrust, timing, and even gimble the engines to do that, without violating objective 2, or constraining objective 1. I don't know how much leeway they have to do so, if the trajectory they need to follow to minimize fuel requires maximum deceleration as soon as it enters the atmosphere, then  they may need to just blast the engines without maximizing the bow shock.

A traditional blunt body reentry vehicle has an ablative TPS and/or heats to thousands of degrees, which is not possible in this case.

Offline deruch

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #683 on: 02/16/2016 07:13 am »
From the UPDATE thread, jacqmans posted the attached image.

Question: The hazard area only extends out by 63 NM? So any ASDS landing attempt places the barge no farther than 63 NM from the Cape, or is there a second zone farther downrange for the landing attempt?

This is only the close inshore safety zone.  There's another one for the potential debris impact areas/1st stage landing area further out.  See the lower inset of the map image.   "CG [Coast Guard] Safety Zone B per 33 CFR 165.775 active 6:01pm to 8:39pm, 24 Feb 16.


Here's the FCC STA for the launch (F9-22), which doesn't include the ASDS radios:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=68937&RequestTimeout=1000

The FCC authorization for the ASDS segment (recovery/landing) is covered in a separate grant:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=69076&RequestTimeout=1000
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Offline Johnnyhinbos

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #684 on: 02/16/2016 10:18 am »

From the UPDATE thread, jacqmans posted the attached image.

Question: The hazard area only extends out by 63 NM? So any ASDS landing attempt places the barge no farther than 63 NM from the Cape, or is there a second zone farther downrange for the landing attempt?

This is only the close inshore safety zone.  There's another one for the potential debris impact areas/1st stage landing area further out.  See the lower inset of the map image.   "CG [Coast Guard] Safety Zone B per 33 CFR 165.775 active 6:01pm to 8:39pm, 24 Feb 16.


Here's the FCC STA for the launch (F9-22), which doesn't include the ASDS radios:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=68937&RequestTimeout=1000

The FCC authorization for the ASDS segment (recovery/landing) is covered in a separate grant:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=69076&RequestTimeout=1000
Yikes! 28 16 10 North, 73 49 5 West is definitely out there! That's like, what, 400 NM due east? (That's a rough guess). Thanks for that link. Now we know right where the barge is going and can calculate departure time.
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Offline chapi

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #685 on: 02/16/2016 12:17 pm »

From the UPDATE thread, jacqmans posted the attached image.

Question: The hazard area only extends out by 63 NM? So any ASDS landing attempt places the barge no farther than 63 NM from the Cape, or is there a second zone farther downrange for the landing attempt?

This is only the close inshore safety zone.  There's another one for the potential debris impact areas/1st stage landing area further out.  See the lower inset of the map image.   "CG [Coast Guard] Safety Zone B per 33 CFR 165.775 active 6:01pm to 8:39pm, 24 Feb 16.


Here's the FCC STA for the launch (F9-22), which doesn't include the ASDS radios:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=68937&RequestTimeout=1000

The FCC authorization for the ASDS segment (recovery/landing) is covered in a separate grant:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=69076&RequestTimeout=1000
Yikes! 28 16 10 North, 73 49 5 West is definitely out there! That's like, what, 400 NM due east? (That's a rough guess). Thanks for that link. Now we know right where the barge is going and can calculate departure time.
But this authorization was requested before SES-9 launch postponement, and the subsequent statement that no recovery operation would occur on this launch, no? (to the benefit of the spacecraft in orbit transit time)

Offline cscott

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #686 on: 02/16/2016 12:46 pm »
The statement was never that "no recovery attempt would take place".  The statement was that they are attempting a more risky recovery in order to give ses-9 a more advantageous orbit.  Let's not turn into an echo chamber of false information.

Wrt to your main point: assuming this application hasn't been amended and does in fact predate the SES press release, possible interpretations:
1. The new launch plan was in the works for some time, and got announced only after it was "final".
1b. Ditto, but the announcement was primarily timed for SES's investors (dont they have a quarterly earnings call coming up?).
2. The plan all along was for no boostback burn, but the SES announcement/new plan was to shorten the reentry burn as well (this has been debated at length here on NSF).

Other thoughts on ways to reconcile the timing... assuming there's anything here to reconcile?
« Last Edit: 02/16/2016 12:52 pm by cscott »

Offline Exastro

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #687 on: 02/16/2016 01:05 pm »
Those are definitely not compression artifacts. I'll be as bold as to claim it's not even a readout artifact from the chip i.e. something like the rolling shutter effect with CMOS chips. Given this is interlaced input video, it's virtually certain this is a CCD chip and so it doesn't suffer from such pixel readout timing variations.

Agreed that it doesn't look like a compression artifact, but I think you have CCD and CMOS reversed here.  A lot of CMOS arrays can be read out in a 'global shutter' mode that avoids the rolling-shutter effect.  CCDs are notorious for it.

NB: For those not intimate with these things, the rolling-shutter effect is caused by imaging arrays that expose pixels sequentially rather than simultaneously.  If something is moving at a speed which is comparable to the rate at which the exposure sweeps across the array, it can be severely distorted (stretched or shrunken in the readout direction). 

Offline Kabloona

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #688 on: 02/16/2016 01:14 pm »
The statement was never that "no recovery attempt would take place".  The statement was that they are attempting a more risky recovery in order to give ses-9 a more advantageous orbit.  Let's not turn into an echo chamber of false information.

Wrt to your main point: assuming this application hasn't been amended and does in fact predate the SES press release, possible interpretations:
1. The new launch plan was in the works for some time, and got announced only after it was "final".
1b. Ditto, but the announcement was primarily timed for SES's investors (dont they have a quarterly earnings call coming up?).
2. The plan all along was for no boostback burn, but the SES announcement/new plan was to shorten the reentry burn as well (this has been debated at length here on NSF).

Other thoughts on ways to reconcile the timing... assuming there's anything here to reconcile?

Another thing I don't quite understand: a couple of pre- FT hazard areas had centers around 500 mile downrange, so I was expecting the FT upgrade with its higher staging velocity to have a landing zone even farther out (assuming no boostback burn).

Maybe the seeming discrepancy is because the re-entry burn will reduce some/most of the horizontal velocity component, in effect truncating the tail of the ballistic arc.

Also, the ASDS may be positioned farther out than the permit states, due to the later decision to give the payload more delta V from the first stage.
« Last Edit: 02/16/2016 01:19 pm by Kabloona »

Offline hkultala

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #689 on: 02/16/2016 01:18 pm »
The statement was never that "no recovery attempt would take place".  The statement was that they are attempting a more risky recovery in order to give ses-9 a more advantageous orbit.  Let's not turn into an echo chamber of false information.

Wrt to your main point: assuming this application hasn't been amended and does in fact predate the SES press release, possible interpretations:
1. The new launch plan was in the works for some time, and got announced only after it was "final".
1b. Ditto, but the announcement was primarily timed for SES's investors (dont they have a quarterly earnings call coming up?).
2. The plan all along was for no boostback burn, but the SES announcement/new plan was to shorten the reentry burn as well (this has been debated at length here on NSF).

Other thoughts on ways to reconcile the timing... assuming there's anything here to reconcile?

Another thing I don't quite understand: a couple of pre- FT hazard areas had centers around 500 mile downrange, so I was expecting the FT upgrade with its higher staging velocity to have a landing zone even farther out (assuming no boostback burn).

If both are used for up to full capasity, FT version has lower staging velocity than 1.1 version; Stage 1 tank size did not increase so all the propellant increase is due subcooling, but stage2 tank was extended. This means stage 2 is doing greater part of the total work, and means lower staging velocity.

Offline Kabloona

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #690 on: 02/16/2016 01:23 pm »
Quote
FT version has lower staging velocity than 1.1 version;

Are you sure about that? I thought I remembered Elon saying staging velocity would be higher.

Quote
This means stage 2 is doing greater part of the total work, and means lower staging velocity.

That assumes that the "total work" of the previous model and the FT model are the same, but they're not. The FT model imparts more total delta V to a given payload, so S1 staging velocity can be higher even though the S1/S2 energy ratio shifts slightly in favor of S2.
« Last Edit: 02/16/2016 02:32 pm by Kabloona »

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #691 on: 02/16/2016 01:44 pm »
Agreed that it doesn't look like a compression artifact, but I think you have CCD and CMOS reversed here.

I don't think I have. CCDs integrate over the entire chip at once and if the exposure duration is >> than the time it takes to readout/store into another buffer, the only side-effect is a ghostly readout smear, oriented vertically or horizontally, depending on how the frame is transferred. CCDs are not susceptible to a rolling shutter as a result, however they are more expensive and are more susceptible to charge bleed artifacts.

Offline cscott

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #692 on: 02/16/2016 02:05 pm »
The 500nm hazard areas might have been the fairing drop zones in previous attempts?

Offline CyndyC

Stage 1 tank size did not increase so all the propellant increase is due subcooling, but stage2 tank was extended. This means stage 2 is doing greater part of the total work, and means lower staging velocity.

It wasn't as apparent that tank sizes in stage 1 were altered for FT, because stage 1 couldn't be stretched like the 2nd stage could, and because the total tank volume didn't change. Bending forces in flight impose a limit on length, and the stage 1 length was maxed out with the stretch from v1.0 to v1.1. The diameter of either stage couldn't be increased either, due to road transport restrictions. The Merlin 1D engines run fuel-rich, but kerosene can't be cooled & densified as much as LOX can, so to accommodate, the stage 1 LOX tank was shortened and the RP-1 tank was stretched into the extra space. Stage 2 altogether was only stretched by about half a meter, but apparently that was enough to accommodate a sufficient stretch of its own RP-1 tank (I don't know if there was any shortening of the stage 2 LOX tank).

It is true that FT changes to stage 2 were so that stage 2 could do more work with less reliance on stage 1, but as Kabloona pointed out, stage 1 performance was also increased for an improved total.
« Last Edit: 02/16/2016 05:00 pm by CyndyC »
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Offline JamesH

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #694 on: 02/16/2016 04:53 pm »
Agreed that it doesn't look like a compression artifact, but I think you have CCD and CMOS reversed here.

I don't think I have. CCDs integrate over the entire chip at once and if the exposure duration is >> than the time it takes to readout/store into another buffer, the only side-effect is a ghostly readout smear, oriented vertically or horizontally, depending on how the frame is transferred. CCDs are not susceptible to a rolling shutter as a result, however they are more expensive and are more susceptible to charge bleed artifacts.

Once you get to the silicon, CMOS uses CCD's. The CMOS bit provides readout silicon, which isn't present on CCD's, which need a separate system. The way the readout is done will affect things like the rolling shutter as described.

Offline Lee Jay

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #695 on: 02/16/2016 07:10 pm »
Agreed that it doesn't look like a compression artifact, but I think you have CCD and CMOS reversed here.

I don't think I have. CCDs integrate over the entire chip at once and if the exposure duration is >> than the time it takes to readout/store into another buffer, the only side-effect is a ghostly readout smear, oriented vertically or horizontally, depending on how the frame is transferred. CCDs are not susceptible to a rolling shutter as a result, however they are more expensive and are more susceptible to charge bleed artifacts.

Once you get to the silicon, CMOS uses CCD's. The CMOS bit provides readout silicon, which isn't present on CCD's, which need a separate system. The way the readout is done will affect things like the rolling shutter as described.

CCD is the readout method, not the detection method.  CCDs shuffle the charge to the edge for A-to-D, while CMOS reads them in-place.

Perhaps you meant to say once you get to the silicon, CMOS and CCDs both use photodiodes.

Offline CyndyC

CCD is the readout method, not the detection method.  CCDs shuffle the charge to the edge for A-to-D, while CMOS reads them in-place. Perhaps you meant to say once you get to the silicon, CMOS and CCDs both use photodiodes.

I have an answer to the original question, for those who still remember it :). Directly from the SpaceX news page on the Sept 2013 CASSIOPE mission at http://www.spacex.com/news/2013/10/14/upgraded-falcon-9-mission-overview, there were two relights of the 1st stage after de-staging -- one for re-entry which used three engines, and a landing-on-the-ocean burn w/o landing gear which used one engine (probably the one SpaceGhost saw). Although at the time those mission add-ons were believed to complete the SpaceX knowledge base for trying the real thing, the relevance to a complete landing profile for the SES-9 mission is limited.
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Offline CyndyC

The FCC authorization for the ASDS segment (recovery/landing) is covered in a separate grant:
https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=initial&application_seq=69076&RequestTimeout=1000

Yikes! 28 16 10 North, 73 49 5 West is definitely out there! That's like, what, 400 NM due east? (That's a rough guess). Thanks for that link. Now we know right where the barge is going and can calculate departure time.

If those coordinates are ~400NM out, why do the [radio] Station Location headings say the boat and the barge are w/in 10NM?

Also, Johnny, can the radio scanning app you gave us for ORBCOMM ASDS & support tracking get us onto the 2090.00000000-MHz radio frequency, or do you or anyone know of an app or a website that can?
« Last Edit: 02/16/2016 08:12 pm by CyndyC »
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Offline Jim

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Re: SpaceX Falcon 9 FT - SES-9 - March 4, 2016 - DISCUSSION
« Reply #698 on: 02/16/2016 07:50 pm »

Also, Johnny, can the radio scanning app you gave us for ORBCOMM ASDS & support tracking get us onto the 2090.00000000-MHz radio frequency, or do you or anyone know of an app that can?

 That is S-Band and not a typical scanner frequency.  And also, it would not be voice.

« Last Edit: 02/16/2016 07:56 pm by Jim »

Offline CyndyC


Also, Johnny, can the radio scanning app you gave us for ORBCOMM ASDS & support tracking get us onto the 2090.00000000-MHz radio frequency, or do you or anyone know of an app that can?

 That is S-Band and not a typical scanner frequency.  And also, it would not be voice.

Well Jim, then would you mind deciphering and relaying the information on NSF as it comes in?

Just kidding.
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