Author Topic: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage  (Read 104986 times)

Offline Orbiter

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #140 on: 08/15/2016 01:43 am »
F9-S1-0024 is on the test stand at McGregor again per the SpaceX Facebook page

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Offline The Roadie

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Offline woods170

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #142 on: 08/15/2016 08:04 am »
Looks like the 'cap' is not on this time.

Online ugordan

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #143 on: 08/15/2016 08:22 am »
Maybe the cap is installed separately.

Offline abaddon

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #144 on: 08/15/2016 08:48 pm »
Speaking of the "cap", Gwynne called it a "variable load head" at the small-sat conference, 20:50 in the below video:
Quote
the variable load head at the top, we're quite worried about that

Just noticed it in passing when I was watching it and thought it was of minor interest.

« Last Edit: 08/15/2016 08:49 pm by abaddon »

Offline Chris Bergin

Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #145 on: 08/31/2016 03:42 pm »
For a "Max Damage" booster, they sure are getting some firings out of it. More:

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Offline AncientU

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #146 on: 08/31/2016 03:51 pm »
Do we have a count?
This is #5 at least...
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Offline John Alan

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Offline Kabloona

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #148 on: 08/31/2016 06:32 pm »
Speaking of the "cap", Gwynne called it a "variable load head" at the small-sat conference, 20:50 in the below video:
Quote
the variable load head at the top, we're quite worried about that

Just noticed it in passing when I was watching it and thought it was of minor interest.


I watched the clip and I still don't know why she said they're worried about the load head, because she didn't elaborate. Worried about what?

Offline wannamoonbase

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #149 on: 08/31/2016 07:54 pm »
Do we have a count?
This is #5 at least...

7 full burns?  Is that 7 after returning to McGregor or does it count the original McGregor test and the first flight for a total of 5 burns post flight?
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Offline rsdavis9

Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #150 on: 08/31/2016 07:55 pm »
I think total after flight macgregor burns
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Offline abaddon

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #151 on: 08/31/2016 09:56 pm »
I watched the clip and I still don't know why she said they're worried about the load head, because she didn't elaborate. Worried about what?
Yeah, I'm not sure what she meant.  And why is it a "variable" load head?  The weight of the stack the first stage supports doesn't really vary that much as it is dominated by the second stage...

Online ugordan

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #152 on: 08/31/2016 10:11 pm »
And why is it a "variable" load head? 

They need to exert additional force on the hold-downs as the vehicle burns through the propellant weight, but the thrust level remains the same. The hold-downs probably can't handle the full force of 9 M1Ds being only opposed by the empty stage weight. Or, they can but they want to be on the safe side.

On the other hand, you don't need that extra load while the stage is still pretty much full.

The weight of the stack the first stage supports doesn't really vary that much as it is dominated by the second stage...

The force exerted on the top of the interstage by the 2nd stage mass is directly proportional to the vehicle axial acceleration. What starts off as 1.3 or so G ends up at 4 Gs or so near burnout.
« Last Edit: 08/31/2016 10:13 pm by ugordan »

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #153 on: 08/31/2016 11:02 pm »
And why is it a "variable" load head? 

They need to exert additional force on the hold-downs as the vehicle burns through the propellant weight, but the thrust level remains the same. The hold-downs probably can't handle the full force of 9 M1Ds being only opposed by the empty stage weight. Or, they can but they want to be on the safe side.

On the other hand, you don't need that extra load while the stage is still pretty much full.

I'm still trying and failing to understand the "variable" part. The word "variable" seems to imply they can vary the weight of the load head. Why not just make it fixed, ie the weight of a fully loaded S2/interstage?

Or maybe it's a semantic misunderstanding. Maybe it's a fixed-weight "load head" that compensates for the "variable" weight of S1 as it burns. But I'd just call that a "load head" and leave the word "variable" out.

So I'm still confused.

Offline acsawdey

Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #154 on: 08/31/2016 11:09 pm »
I'm still trying and failing to understand the "variable" part. The word "variable" seems to imply they can vary the weight of the load head. Why not just make it fixed, ie the weight of a fully loaded S2/interstage?

Or maybe it's a semantic misunderstanding. Maybe it's a fixed-weight "load head" that compensates for the "variable" weight of S1 as it burns. But I'd just call that a "load head" and leave the word "variable" out.

So I'm still confused.

The S1 accelerates with a fixed mass S2 atop the interstage. The acceleration varies as S1 propellant is depleted. S1 being constructed of an aluminum alloy presumedly has the possibility of fatigue issues. Therefore, you might consider a cap on top that pulls down harder as the burn progresses to model the loads felt by S1 as acceleration ramps up. Then at least some of the loads on/within S1 are similar to flight loads.

Offline guckyfan

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #155 on: 09/01/2016 04:22 am »
Those thick cables coming down from the "load head" must have some function. To me it looks like winches can pull on them and add dynamic load. They don't use that device on normal testing.

Offline CyndyC

Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #156 on: 09/01/2016 07:12 pm »
Speaking of the "cap", Gwynne called it a "variable load head" at the small-sat conference, 20:50 in the below video:
Quote
the variable load head at the top, we're quite worried about that

I interpret that to be a reference to the varying mass of payloads in the future. Just because the stage tests well with a dummy cap of whatever mass doesn't guarantee the launcher will perform the same way with something heavier on top.
« Last Edit: 09/01/2016 10:52 pm by CyndyC »
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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #157 on: 09/01/2016 07:48 pm »
Those thick cables coming down from the "load head" must have some function. To me it looks like winches can pull on them and add dynamic load. They don't use that device on normal testing.

That might be the source of Gwynne's concern. They'd have to change the load on each cable symmetrically/simultaneously in order not to pull the stage sideways, and that could be tricky.
« Last Edit: 09/02/2016 10:44 am by Kabloona »

Offline deruch

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #158 on: 09/02/2016 02:21 pm »
I'm still trying and failing to understand the "variable" part. The word "variable" seems to imply they can vary the weight of the load head. Why not just make it fixed, ie the weight of a fully loaded S2/interstage?

Or maybe it's a semantic misunderstanding. Maybe it's a fixed-weight "load head" that compensates for the "variable" weight of S1 as it burns. But I'd just call that a "load head" and leave the word "variable" out.

So I'm still confused.
Maybe it's not "dynamically variable", but rather "statically variable" (probably not the correct terms).  i.e. the load doesn't change during any given test, but can be variably dialed up/down to whatever load you want (within parameters).  So, for 1 test it may be 50,000 lbf and for another 30,000 lbf.  As opposed to one that only ever gives you 40,000lbf.  Though this seems somewhat silly to me, and my personal interpretation agreed with the straightforward one given by ugordan and others above.
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Offline biosehnsucht

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Re: SpaceX Falcon 9 (F9-S1-0024) Reuse Testing Coverage
« Reply #159 on: 09/06/2016 08:11 am »
Why not tension the cables to a specific midpoint and have a hydraulic system sitting on top of the stage that can move up and down to add/remove tension to simulate a range? That way you're not fiddling with 4 adjustments, just one.

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