Author Topic: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion Thread 1  (Read 593179 times)

Offline cscott

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #440 on: 12/21/2017 12:40 PM »
A bit of a tease but sounds like payload is either in processing or encapsulated:

Can confirm that it is already mated to the payload adapter.

Can you confirm whether or not this was it:

I was taking a sponsored community college kid on a bus tour at KSC a few days back on the 8th.
We got stopped by the escort vehicles for... this.
Headed to 39A as far as I could tell...
« Last Edit: 12/21/2017 12:41 PM by cscott »

Offline Norm38

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #441 on: 12/21/2017 01:43 PM »
Did they change the Ti grid fin design?  I don't see the scalloped edges in the latest FH images.

Online matthewkantar

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #442 on: 12/21/2017 01:58 PM »
Did they change the Ti grid fin design?  I don't see the scalloped edges in the latest FH images.

The two outer cores are fitted with TI grid fins, the center core has Al fins.

Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #443 on: 12/21/2017 01:59 PM »
Did they change the Ti grid fin design?  I don't see the scalloped edges in the latest FH images.

I think it's there, the scalloped side is the side against the stage so hard to see.
« Last Edit: 12/21/2017 02:04 PM by nacnud »

Offline Coastal Ron

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #444 on: 12/21/2017 08:44 PM »
The left side booster also appears to contain the number 8 in the expected location, considering the two cores are 180 deg apart.

Actually the two side boosters are not 180 degrees apart. I noticed the feed line that runs down the side of the boosters are installed so that they are on the same side of the center stage.

What precisely do you mean by feed lines? To the best that my eye can see, they are identical cores, one simply rotated 180 degrees. Like Atlas V HLV would have done and unlike Delta IV Heavy.

OK, apparently it was an optical delusion on my part. I mistook the underside of the legs for the external "structure" that runs down the side of each 1st stage (what I called feed lines, but not sure now). The wide angle of the camera lens meant that you don't see the other legs easily, which added to my confusion.

Nothing to see here...  :o
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Online abaddon

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #445 on: 12/21/2017 09:57 PM »
Been meaning to ask a (rather trivial) question but keep forgetting: does anyone know why some (but not all) of the engine bells on the left booster are shiny/reflective, while all the other engine bells are matte/sooty?  Any significance to that?

(Best seen from the overhead views)
« Last Edit: 12/21/2017 09:58 PM by abaddon »

Offline Jcc

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #446 on: 12/21/2017 11:32 PM »
Did they change the Ti grid fin design?  I don't see the scalloped edges in the latest FH images.

The two outer cores are fitted with TI grid fins, the center core has Al fins.

I find that a bit odd, I would think that the center core would be higher energy than the side boosters.

Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #447 on: 12/21/2017 11:36 PM »
Due to the turbulence produced by the nose cone of the side boosters while it is traveling backwards more control authority is needed by the side booster than the centre stage. Hence they have the larger Ti grid fins.

Offline meekGee

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #448 on: 12/21/2017 11:58 PM »
Due to the turbulence produced by the nose cone of the side boosters while it is traveling backwards more control authority is needed by the side booster than the centre stage. Hence they have the larger Ti grid fins.

And/or they want more authority during separation (and forward flight) to ensure control of the separating stages.

If they can get the cores to "peel" using the grid fins, beyond a certain angle, the force on the entire body of the side boosters will point outwards and thus be safe.
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #449 on: 12/22/2017 12:04 AM »
The separation is performed in vacuum, grid fins can't help then.

Offline deruch

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #450 on: 12/22/2017 07:14 AM »
Been meaning to ask a (rather trivial) question but keep forgetting: does anyone know why some (but not all) of the engine bells on the left booster are shiny/reflective, while all the other engine bells are matte/sooty?  Any significance to that?

(Best seen from the overhead views)

SpaceX stopped shining the nozzles at some point and switched to a matte finish.  Since they are reusing old boosters, the full switch must have happened between the original launch dates for the side cores.  Before they went to all engines on a booster matte, they experimented with a mix of both.  Well, first I think they experimented with a few only partially shined bells (they looked like they had stripes running up and down), then went forward incrementally from there.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline meekGee

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #451 on: 12/22/2017 11:56 AM »
The separation is performed in vacuum, grid fins can't help then.
That would indeed be a problem..  but how high are we talking about?
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Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #452 on: 12/22/2017 12:05 PM »
Around 100km, I've attached below a brilliant bit of visualization from redditor veebay that shows a detailed Falcon 9 Stage 1 Landing Analysis. It's really good so I hope attaching it here is ok, if not follow the link. In fact follow the link anyway and check it out.

Offline Norm38

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #453 on: 12/22/2017 01:39 PM »
Due to the turbulence produced by the nose cone of the side boosters while it is traveling backwards more control authority is needed by the side booster than the centre stage. Hence they have the larger Ti grid fins.

This I can't picture. The tails of aircraft aren't open cylinders, they taper to points.
I get that the two are different and have different control responses. But why does the nosecone produce
worse turbulence? Is it not long enough or something?

Edit:  I guess this belongs in an FH thread.
« Last Edit: 12/22/2017 01:40 PM by Norm38 »

Online wolfpack

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #454 on: 12/22/2017 01:53 PM »
What do we think the biggest risks are for this mission? If I had to guess, in order:

1. Side booster sep
2. Liftoff
3. MaxQ
4. Faring sep
5. S/C sep

Anyone else?

Offline nacnud

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #455 on: 12/22/2017 02:32 PM »
Due to the turbulence produced by the nose cone of the side boosters while it is traveling backwards more control authority is needed by the side booster than the centre stage. Hence they have the larger Ti grid fins.

This I can't picture. The tails of aircraft aren't open cylinders, they taper to points.
I get that the two are different and have different control responses. But why does the nosecone produce
worse turbulence? Is it not long enough or something?

Edit:  I guess this belongs in an FH thread.

It probably should be in the FH thread and there is a discussion in the L2 version but you asked the question here so...

You guessed the answer, the nose cone isn't long enough, or rather it's not designed to fly backwards but it is the right shape for assent which is more important. For some reason the booster with the interstage still attached is fine. So you could make it fit this thread by asking why doesn't the booster need larger fins as it flies today?


Offline drnscr

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #456 on: 12/22/2017 02:32 PM »
What do we think the biggest risks are for this mission? If I had to guess, in order:

1. Side booster sep
2. Liftoff
3. MaxQ
4. Faring sep
5. S/C sep

Anyone else?

So, in other words, everything except engine startup.  I have to put engine startup at the top of the list.

Offline Xentry

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #457 on: 12/22/2017 02:46 PM »
1. MaxQ
2. Engine Startup
3. Liftoff
4. Side booster sep

Offline Michael.Kalenty

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #458 on: 12/22/2017 02:49 PM »
What do we think the biggest risks are for this mission? If I had to guess, in order:

1. Side booster sep
2. Liftoff
3. MaxQ
4. Faring sep
5. S/C sep

Anyone else?

Biggest risks will be anything different from Falcon 9 that they can't test on the ground. Those would be:
1. Booster sep
2. Ignition (The launch itself is just releasing the holddowns. Larger risk is the near-simultanious ignition of 27 engines.)
3. The entire ascent between liftoff and booster sep. (This portion of flight is a essnetially flying 3 rockets side by side, so the boosters run the risk of ripping away from the core, or the opposite)

Anything after booster sep (Core/S2 sep, fairing sep, S/C sep) is essentially identical to a Falcon 9 flight, so I'd rate the risk level of these events the same I would on a Falcon 9 mission.

Offline TaurusLittrow

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Re: SpaceX FH : Falcon Heavy Demo : early 2018 : Discussion
« Reply #459 on: 12/22/2017 02:57 PM »
Any estimates of the time between the static fire of Falcon Heavy (assuming successful) and the initial launch attempt?

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