Author Topic: SpaceX Falcon 9 : CRS-12 : Aug 14, 2017 : DISCUSSION  (Read 122606 times)

Offline whitelancer64

Cropped version of SoaceX landing photo. I know the side on angle isn't great, but to me it looks mainly like dirt (sand?) on the pad, the pad paint job seems to have held up pretty well?

The landing pad is concrete. This has been definitively established multiple times. It's surrounded by a ring of compacted dirt.
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Offline abaddon

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Cropped version of SoaceX landing photo. I know the side on angle isn't great, but to me it looks mainly like dirt (sand?) on the pad, the pad paint job seems to have held up pretty well?
The landing pad is concrete. This has been definitively established multiple times. It's surrounded by a ring of compacted dirt.
I believe @FutureSpaceTourist was talking about what looks like a bit of a wash of dirt/sand on the pad, not what the pad is made of, and suggesting that it is in fact dirt/sand and not damage from the rocket plume.  As noted, it is difficult to say for sure due to the angle, but I would tend to agree.
« Last Edit: 08/15/2017 04:00 pm by abaddon »

Offline Rocket Science

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The grid fins seemed to be much more active during the landing sequence, compared to previous missions.
They looked like they were getting a workout and still makes me smile every time... :)
"The laws of physics are unforgiving"
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Offline joncz

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I believe @FutureSpaceTourist was talking about what looks like a bit of a wash of dirt/sand on the pad, not what the pad is made of, and suggesting that it is in fact dirt/sand and not damage from the rocket plume.  As noted, it is difficult to say for sure due to the angle, but I would tend to agree.

Surely so.  They've scarified the nearby surface to remove topsoil in preparation for pouring concrete for the second pad.  They certainly didn't have a water truck active just prior to launch for dust control, and with the wind at the coast, I have no doubt there was a layer of dust and sand across the entire concrete surface.

Offline Basto

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If you compare the landing location on the pad to CRS 11 and you can see that the rocket performed the landing perfectly.

While the AOA looked pretty dramatic, there are not many landings that have had as clear a view of the entire process from the ground. So I am assuming it was not far out of the ordinary. Either that or we were witnessing part a block IV upgrade of some sort.


Offline kenny008

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My understanding is that they target offshore until they are comfortable that the engines are performing properly, then bring it over the pad for final landing.  The AOA maneuver occurred right after the entry burn was complete, so this might be when they are satisfied the engines are working properly and they can then target the pad. 

Not convinced it's any different than previous flights.  Might be just a great view this time.

Offline AlesH

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Where exactly (relative to ISS) is Dragon CRS-12 right now (Tuesday, August 15th, 18:30 UT)? Do you know the times and parameters of Dragon's orbital maneuvers? The officially issued TLE parameters do not make much sense to me, because the arrival to the ISS would be up to August 17th (without very strong and ineffective maneuvers).
« Last Edit: 08/15/2017 07:01 pm by AlesH »

Offline stcks

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you will notice some of the block 4 differences if you have a good eye and watch the flight footage and not all are small differences but most are. I'll leave you with that until launch day.

Well, its the day after and I've looked at tons of pictures and video and I can't find anything different. Care to elaborate?

Offline ppb

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Looking side way, looks like 20-25 degree angle of attack.


Great pix. I'm kind of amazed the little (relative to the body) grid fins have that much control authority. The CG must really be close to the engines at that point.

Offline LouScheffer

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The takeoff looked quicker to me, but I compared it to CRS-11 and it's almost identical.

Looking at both videos, at the frame where the clock ticks from 6 to 7, the bottom of the booster is about 3 "floors" above the top of the FSS just behind it.  Side by side, it looks exactly the same to me.  The telemetry at this frame shows 53 km/h for CRS-11, and even a little less for CRS-12 (51 km/h).   So certainly a 10% thrust increase is ruled out - that would change the initial acceleration from something like 0.3 G up to 0.4 G up, which would be clearly noticeable.  Instead the two launches look identical to within the accuracy of the webcast.
EDIT: fixed units
« Last Edit: 08/16/2017 12:45 am by LouScheffer »

Offline stcks

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The takeoff looked quicker to me, but I compared it to CRS-11 and it's almost identical.

Looking at both videos, at the frame where the clock ticks from 6 to 7, the bottom of the booster is about 3 "floors" above the top of the FSS just behind it.  Side by side, it looks exactly the same to me.  The telemetry at this frame shows 53 m/s for CRS-11, and even a little less for CRS-12 (51 m/s).   So certainly a 10% thrust increase is ruled out - that would change the initial acceleration from something like 0.3 G up to 0.4 G up, which would be clearly noticeable.  Instead the two launches look identical to within the accuracy of the webcast.

Yes there were clearly no thrust increases on CRS-12.

Offline Joffan

The takeoff looked quicker to me, but I compared it to CRS-11 and it's almost identical.

Looking at both videos, at the frame where the clock ticks from 6 to 7, the bottom of the booster is about 3 "floors" above the top of the FSS just behind it.  Side by side, it looks exactly the same to me.  The telemetry at this frame shows 53 m/s for CRS-11, and even a little less for CRS-12 (51 m/s).   So certainly a 10% thrust increase is ruled out - that would change the initial acceleration from something like 0.3 G up to 0.4 G up, which would be clearly noticeable.  Instead the two launches look identical to within the accuracy of the webcast.

I think the difference might just be that the audio count of zero was better synchronized to the hold-down release. Because it looked quicker to me too, but I don't see that on telemetry or visuals.
Getting through max-Q for humanity becoming fully spacefaring

Offline envy887

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The takeoff looked quicker to me, but I compared it to CRS-11 and it's almost identical.

Looking at both videos, at the frame where the clock ticks from 6 to 7, the bottom of the booster is about 3 "floors" above the top of the FSS just behind it.  Side by side, it looks exactly the same to me.  The telemetry at this frame shows 53 m/s for CRS-11, and even a little less for CRS-12 (51 m/s).   So certainly a 10% thrust increase is ruled out - that would change the initial acceleration from something like 0.3 G up to 0.4 G up, which would be clearly noticeable.  Instead the two launches look identical to within the accuracy of the webcast.

Assuming the liftoff mass was the same... which it may not have been since it depends on prop temp.

I don't have any evidence that thrust was higher, and I actually doubt that it was, but I'm just pointing out that acceleration depends on more than just thrust.

Offline Steven Pietrobon

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Maybe the thrust increase was for the second stage. CRS-12 second stage burn time was 10 seconds shorter than CRS-11 (6:38 versus 6:48). Of course, different payload mass, orbit and throttling could help to explain the difference.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Bargemanos

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« Last Edit: 08/16/2017 01:53 pm by Bargemanos »

Offline abaddon

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I suppose it is possible that the booster was cleared for higher thrust but the mission profile chose not to use it.  No need for it on this mission and maybe NASA didn't want to be the first guinea pig.

Offline stcks

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Maybe the thrust increase was for the second stage. CRS-12 second stage burn time was 10 seconds shorter than CRS-11 (6:38 versus 6:48). Of course, different payload mass, orbit and throttling could help to explain the difference.

Maybe, but ChrisG specifically said M1D:

Quote
The first Block 4 did make use of increased-thrust Merlin 1D engines. The thrust increase of the Merlin 1Ds is also incremental, with a final thrust increase set to debut on the Block 5.

If there was a thrust increase on the first stage it was so slight as to not be noticeable. There are some really good telemetry graphs and two comparisons between CRS-11 and CRS-12 that can be found on this reddit post. Its quite obvious that, everything else being relatively equal, both CRS-11 and CRS-12 were flown with basically the same thrust (but different max-q throttling).

I'm very curious what was meant by the above quote. Did it just mean that the flown engines were uprated but flown at same thrust levels?

Online FutureSpaceTourist

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Fun video by Scott Manley



Quote
Published on 16 Aug 2017
SpaceX launches Dragon Spacecraft to the International Space Station under the Commercial Resupply Services (CRS) program.
This video synchronizes the launches of CRS-1 through CRS-12 and you can see how the technology and launch profiles have changed.
The were a few Dragon missions prior to this which were technology demonstrators for the Commercial Orbital Transportation Services (COTS) program, the second of which berthed at the ISS in May 2012. This is missing from the video because 13 is not a convenient number for this presentation :)

Mission control audio is chopped up with sections from all launches intermixed to highlight the major events.

The music is by Test Shot Starfish who do all the music for the SpaceX livestreams.
https://soundcloud.com/testshotstarfish
Tracks are 'Re - Flight', 'Approaching Dragon' and 'Andromeda'
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...

Offline Raul

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If there was a thrust increase on the first stage it was so slight as to not be noticeable. There are some really good telemetry graphs and two comparisons between CRS-11 and CRS-12 that can be found on this reddit post. Its quite obvious that, everything else being relatively equal, both CRS-11 and CRS-12 were flown with basically the same thrust (but different max-q throttling).

I'm very curious what was meant by the above quote. Did it just mean that the flown engines were uprated but flown at same thrust levels?

It could be also possible that increased booster liftoff thrust upto 7.6MN (1.71M lbf) was used already before this first flight of Block 4 booster (incl. CRS-11), as it was mentioned first time by John Federspiel during NROL-76 webcast (also S2 in Block 4 configuration for the first time), mentioned that similarly also during BulgariaSat-1 webcast, or by SFN in case of Intelsat 35e. Could be only tweaked thrust without fundamental HW changes.
« Last Edit: 08/17/2017 08:19 am by Raul »

Offline Comga

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Fun video by Scott Manley



Quote
Published on 16 Aug 2017
SpaceX launches Dragon Spacecraft to the International Space Station under the Commercial Resupply Services (CRS) program.
This video synchronizes the launches of CRS-1 through CRS-12 and you can see how the technology and launch profiles have changed.
The were a few Dragon missions prior to this which were technology demonstrators for the Commercial Orbital Transportation Services (COTS) program, the second of which berthed at the ISS in May 2012. This is missing from the video because 13 is not a convenient number for this presentation :)

Mission control audio is chopped up with sections from all launches intermixed to highlight the major events.

The music is by Test Shot Starfish who do all the music for the SpaceX livestreams.
https://soundcloud.com/testshotstarfish
Tracks are 'Re - Flight', 'Approaching Dragon' and 'Andromeda'
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...

This is TERRIFIC!
Such an education
The first stage landings have stopped getting faster.  CRS-11 first stage landed at 7:40 elapsed time.  CRS-12 was 6 seconds slower.  CRS9 and CRS-10 were identically 40 seconds slower and CRS-8, going to the ASDS was a full 60 seconds slower.  But they were all exciting to watch, especially together.
There is even more contrast in the first stage flights, with CRS-1 taking way longer to stage.  Yet CRS-5 was the shortest time to separation of Dragon.
Then there are the LOX-cam views. I miss those.
Again, a really cool compilation.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

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