Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion Thread 1  (Read 562820 times)

Offline Cheapchips

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #380 on: 12/20/2017 10:11 AM »
The titanium fins are bigger, so they felt they needed more control authority on the side boosters?
« Last Edit: 12/20/2017 12:51 PM by Cheapchips »

Offline loki

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #381 on: 12/20/2017 10:26 AM »
Quite impressive as expected. Canít wait for launch.
I guess Spacex needs this demo asap,  because design of busters has to be verified before starting production of Block5?

Offline eweilow

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) :)

Offline ugordan

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #383 on: 12/20/2017 10:38 AM »
The titanium fins are bigger, so they felt the needed more control authority on the side boosters?

Yes.

Offline ugordan

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #384 on: 12/20/2017 10:41 AM »
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) :)

http://forum.nasaspaceflight.com/index.php?topic=42705.msg1761564#msg1761564

Offline Jet Black

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?
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline ugordan

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #386 on: 12/20/2017 10:51 AM »
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.

Offline Skylab

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #387 on: 12/20/2017 11:47 AM »
The large frame connecting the boosters surprised me. Guess I was just going by the early renderings, but it's quite big.
« Last Edit: 12/20/2017 11:48 AM by Skylab »

Offline JamesH65

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #388 on: 12/20/2017 12:09 PM »
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.

Offline IntoTheVoid

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #389 on: 12/20/2017 12:10 PM »
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.

Online woods170

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #390 on: 12/20/2017 12:11 PM »
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.
« Last Edit: 12/20/2017 12:11 PM by woods170 »

Offline ugordan

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #391 on: 12/20/2017 12:40 PM »
What those renders from 2 years ago didn't show was the connections at the bottom.

Including the missing TSMs, heh.

Offline Skylab

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #392 on: 12/20/2017 12:47 PM »
Two years is the blink of an eye in Falcon Heavy terms. ;) Glad to finally be on the eve of seeing the first launch.
« Last Edit: 12/20/2017 12:49 PM by Skylab »

Offline Comga

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #393 on: 12/20/2017 01:44 PM »
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.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Nomadd

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #394 on: 12/20/2017 01:50 PM »
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.

Offline old_sellsword

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #395 on: 12/20/2017 02:37 PM »
Anything special about the PAF which can only be partly seen?

The PAF isnít even present, thatíll be with the payload wherever itís being processed. The top of the second stage is the avionics tower.

Offline cscott

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #396 on: 12/20/2017 02:40 PM »
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).

Offline matthewkantar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #397 on: 12/20/2017 02:54 PM »
Nice detail.

Offline StevenV

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #398 on: 12/20/2017 03:00 PM »
The center core also has no use for the greater cross-range the titanium fins give.

Offline russianhalo117

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #399 on: 12/20/2017 03:16 PM »
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.
« Last Edit: 12/20/2017 05:35 PM by russianhalo117 »

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