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#380
by
Cheapchips
on 20 Dec, 2017 10:11
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The titanium fins are bigger, so they felt they needed more control authority on the side boosters?
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#381
by
loki
on 20 Dec, 2017 10:26
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Quite impressive as expected. Can’t wait for launch.
I guess Spacex needs this demo asap, because design of busters has to be verified before starting production of Block5?
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#382
by
eweilow
on 20 Dec, 2017 10:29
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https://twitter.com/elonmusk/status/943420026593337344
@elonmusk
Falcon Heavy at the Cape
It's worth noting that the first of the pictures (the one from above) is obviously a stitch of more than one picture and has resulted in some missing features just above the Falcon Heavy logo (like the separation pushers, which are clearly visible in the second picture)
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#383
by
ugordan
on 20 Dec, 2017 10:38
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The titanium fins are bigger, so they felt the needed more control authority on the side boosters?
Yes.
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#384
by
ugordan
on 20 Dec, 2017 10:41
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#385
by
Jet Black
on 20 Dec, 2017 10:45
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I'm curious as to why the outer cores have Ti grid fins rather than the Al of the center core. Could that be because the outer cores will be released lower in the atmosphere and need more control, since they will be relatively close together and have to redirect more quickly while performing a more complex maneuver (RTLS, boost back etc) than the center core, which will just go out to an ASDS somewhere out at sea?
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#386
by
ugordan
on 20 Dec, 2017 10:51
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The large fins are due to increased control authority, but not for the purposes of clean separation of the two side boosters. At that point they are in effective vacuum and, besides, the fins are stowed during the most critical separation period.
Not sure what is public knowledge about this so I'll just say L2 has more info on this.
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#387
by
Skylab
on 20 Dec, 2017 11:47
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The large frame connecting the boosters surprised me. Guess I was just going by the early renderings, but it's quite big.
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#388
by
JamesH65
on 20 Dec, 2017 12:09
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I'm curious as to why the outer cores have Ti grid fins rather than the Al of the center core. Could that be because the outer cores will be released lower in the atmosphere and need more control, since they will be relatively close together and have to redirect more quickly while performing a more complex maneuver (RTLS, boost back etc) than the center core, which will just go out to an ASDS somewhere out at sea?
I wonder if they need the extra control to move the boosters further apart during reentry, perhaps to increase the time between each landing by one running an S shape return, one being straight.
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#389
by
IntoTheVoid
on 20 Dec, 2017 12:10
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https://twitter.com/elonmusk/status/943420026593337344
@elonmusk
Falcon Heavy at the Cape
It's worth noting that the first of the pictures (the one from above) is obviously a stitch of more than one picture and has resulted in some missing features just above the Falcon Heavy logo (like the separation pushers, which are clearly visible in the second picture)
If at the side of the picture, you look at the perspective of the steel ribs of the HIF, it seems pretty clear that it's 3 photos; one centered on the second stage, one centered at the grid fins, and one centered on the landing legs.
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#390
by
woods170
on 20 Dec, 2017 12:11
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The large frame connecting the boosters surprised me. Guess I was just going by the early renderings, but it's quite big.
The big frame at the top is very close to what was shown in renders two years ago.
What those renders from 2 years ago didn't show was the connections at the bottom.
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#391
by
ugordan
on 20 Dec, 2017 12:40
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What those renders from 2 years ago didn't show was the connections at the bottom.
Including the missing TSMs, heh.
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#392
by
Skylab
on 20 Dec, 2017 12:47
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Two years is the blink of an eye in Falcon Heavy terms.
Glad to finally be on the eve of seeing the first launch.
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#393
by
Comga
on 20 Dec, 2017 13:44
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Larger versions
This is perhaps the most magnificent post in a long time
(with honorable mentions for the posts of the same photos in lower resolution)
Can anyone make out any details other than the grid fins?
Anything special about the PAF which can only be partly seen?
(No Roadster but that will be encapsulated before being attached. Boo hoo)
The attach mechanisms all seem to be held dynamically against the launch forces. Not what I expected.
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#394
by
Nomadd
on 20 Dec, 2017 13:50
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Interesting the side boosters have Ti grid fins while the centre core has Al fins. I would have assumed the other way round as the centre core has the hotter reentry.
No interstage on the sides, so they need the bigger fins because of the airflow.
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#395
by
old_sellsword
on 20 Dec, 2017 14:37
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Anything special about the PAF which can only be partly seen?
The PAF isn’t even present, that’ll be with the payload wherever it’s being processed. The top of the second stage is the avionics tower.
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#396
by
cscott
on 20 Dec, 2017 14:40
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I wonder if they are production-constrained on the Ti fins? It was discussed here (tea-leaf-reading on some ambiguous tweets from Elon) that perhaps the first prototype Ti fins were machined from a solid block while the production fins would be forged, and that the forging process had significant setup costs/lead time, so they might not want to get that going until the Ti fin design had been thoroughly vetted... presumably including on this FH maiden flight.
So there might be only two sets of prototype Ti fins in existence, and they've been dedicated to the two FH side boosters... explaining why some other recent high-energy F9 flight candidates haven't opted for Ti.
For that matter, they obviously see no reason *not* to use Al fins, like on the center booster here, so Al not be end-of-lifed with F9 block 5. Put another way, the only "problem" with Al fins is limited reusability, not functionality (for F9; FH needs the extra control).
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#397
by
matthewkantar
on 20 Dec, 2017 14:54
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#398
by
StevenV
on 20 Dec, 2017 15:00
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The center core also has no use for the greater cross-range the titanium fins give.
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#399
by
russianhalo117
on 20 Dec, 2017 15:16
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I wonder if they are production-constrained on the Ti fins? It was discussed here (tea-leaf-reading on some ambiguous tweets from Elon) that perhaps the first prototype Ti fins were machined from a solid block while the production fins would be forged, and that the forging process had significant setup costs/lead time, so they might not want to get that going until the Ti fin design had been thoroughly vetted... presumably including on this FH maiden flight.
So there might be only two sets of prototype Ti fins in existence, and they've been dedicated to the two FH side boosters... explaining why some other recent high-energy F9 flight candidates haven't opted for Ti.
For that matter, they obviously see no reason *not* to use Al fins, like on the center booster here, so Al not be end-of-lifed with F9 block 5. Put another way, the only "problem" with Al fins is limited reusability, not functionality (for F9; FH needs the extra control).
They may 3D print the fins in the future if they want to pursue maximum achievable strength, quality, reduced lead and manpower times and cost reduction.
Glad to finally be on the eve of seeing the first launch.