Author Topic: SpaceX Falcon 9 : GovSat-1 (SES-16) : Jan 31. 2018 - Discussion  (Read 207777 times)

Offline marsbase

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We need not worry if the truth isn’t immediately obvious.
I would say that is pretty much the mantra of science (and good technology).  Religion and politics require immediate truth.  Science can afford to be patient.  8)

Offline hkultala

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SpaceX has been working on using more of the atmosphere to slow down Falcon 9 as that saves propellant and will be important for BFR.

F9 1st stage is having quite big angle of attack when it's flying back towards landing location. Quite much of body lift can be gotten even from a cylinder shape, when it's light enough.

And the higher angle of attack saves fuel used to both flying back AND slowing down to landing velocity

Offline Jim

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INTERESTING!

SpaceX recovery support ships Go Quest and Go Searcher have left Port Canaveral.

Possible fairing recovery test!

No, more likely telemetry relay

Online wannamoonbase

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We need not worry if the truth isn’t immediately obvious.
I would say that is pretty much the mantra of science (and good technology).  Religion and politics require immediate truth.  Science can afford to be patient.  8)

That's because facts take time, the other 2 are feelings.  Feelings won't get one to the moon or mars.

It's been a long cold January, I'm glad we are back to another launch day.

Go F9! Go GovSat-1!
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline Raul

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INTERESTING!

SpaceX recovery support ships Go Quest and Go Searcher have left Port Canaveral.

Possible fairing recovery test!

No, more likely telemetry relay

Go Quest is at the position of probable booster water landing (former droneship landing position) - it means probably to receive telemetry of booster water landing here and visual check.

Go Searcher is at the position of probable fairing landing/splashdown – likely receive telemetry, try to recover the fairing or collect debris.

Offline mgeagon

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It is evident that SpaceX believes in minimum refurbishment. “Why detach the legs? Why not expend the entire hardware first launched with NROL 76?” Reduce labor by finding areas that don’t require intervention. However, the legs were detached at LZ1. Furthermore, they appear to be cleaned (not sooty). Why go through the trouble of cleaning the legs and adding weight to a minimum fuel payload for some science that has already been collected two dozen times? There is clearly a great reason, but I cannot fathom what that is.

Mark Eagon

Offline rcoppola

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A ways back Elon mentioned wanting to reduce some return velocity by deploying the legs sooner.
Perhaps they'll test that here. Or not. There could be a few components on one or all legs that are being tested for a Block 5 implementation.
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Offline Cherokee43v6

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A ways back Elon mentioned wanting to reduce some return velocity by deploying the legs sooner.
Perhaps they'll test that here. Or not. There could be a few components on one or all legs that are being tested for a Block 5 implementation.

Errr... what legs?  Look at the pictures.  This Falcon's had a leg-otomy
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Offline mlow

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A ways back Elon mentioned wanting to reduce some return velocity by deploying the legs sooner.
Perhaps they'll test that here. Or not. There could be a few components on one or all legs that are being tested for a Block 5 implementation.

Errr... what legs?  Look at the pictures.  This Falcon's had a leg-otomy

Look again, the rocket has legs.

Offline pb2000

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It is evident that SpaceX believes in minimum refurbishment. “Why detach the legs? Why not expend the entire hardware first launched with NROL 76?” Reduce labor by finding areas that don’t require intervention. However, the legs were detached at LZ1. Furthermore, they appear to be cleaned (not sooty). Why go through the trouble of cleaning the legs and adding weight to a minimum fuel payload for some science that has already been collected two dozen times? There is clearly a great reason, but I cannot fathom what that is.

Mark Eagon
1032 originally flew in May, so it was refurbished long before the decision to dump block 3's was made. NASA wanted an original CRS booster so 1035 jumped the queue. The only questions are, have the legs and fins been on since refurb and, if not for FH slip, were they considering recoverying this one?
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Offline mgeagon

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Online LouScheffer

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SpaceX has been working on using more of the atmosphere to slow down Falcon 9 as that saves propellant and will be important for BFR.

F9 1st stage is having quite big angle of attack when it's flying back towards landing location. Quite much of body lift can be gotten even from a cylinder shape, when it's light enough.

And the higher angle of attack saves fuel used to both flying back AND slowing down to landing velocity
This makes sense to me.   Try a higher angle of attack, a test that requires the legs be attached to get realistic results.  Then a three engine landing burn, which they have not used in production yet.  This too requires the legs, since the G forces will be different at leg deployment, even if they are throttling down to one engine at that time.  Two good and useful tests that require the legs.

Offline Lar

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SpaceX has been working on using more of the atmosphere to slow down Falcon 9 as that saves propellant and will be important for BFR.

F9 1st stage is having quite big angle of attack when it's flying back towards landing location. Quite much of body lift can be gotten even from a cylinder shape, when it's light enough.

And the higher angle of attack saves fuel used to both flying back AND slowing down to landing velocity

I do wonder why they aren't using the titanium fins then, won't those do better at holding higher angles of attack for both heating and control authority reasons (I'm assuming that using the fins that way heats them up a lot more than gentler angles)?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline Scylla

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SpaceX has been working on using more of the atmosphere to slow down Falcon 9 as that saves propellant and will be important for BFR.

F9 1st stage is having quite big angle of attack when it's flying back towards landing location. Quite much of body lift can be gotten even from a cylinder shape, when it's light enough.

And the higher angle of attack saves fuel used to both flying back AND slowing down to landing velocity

I do wonder why they aren't using the titanium fins then, won't those do better at holding higher angles of attack for both heating and control authority reasons (I'm assuming that using the fins that way heats them up a lot more than gentler angles)?
Because they're throwing the stage away and titanium is more expensive than aluminum?
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Offline Johnnyhinbos

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Except aren't the Block 5 legs supposed to look quite different? Therefore potentially negating any detailed info that might be gathered on this flight that hasn't been gleaned already.

And I don't buy the whole "they were already installed prior to knowing it was going expendable, so might as well just leave them on" argument. That seems a bit spurious. There's value in those legs, there's potential failure points during launch in those legs (no matter how small, there's some probability), and there's a mass penalty in those legs.

But - I love a mystery and hoping for a qualified answer!

John (aka 'Hanzl', but not aka 'johnnyhinbos')
John Hanzl. Author, action / adventure www.johnhanzl.com

Offline Rocket Science

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We need not worry if the truth isn’t immediately obvious.
I would say that is pretty much the mantra of science (and good technology).  Religion and politics require immediate truth.  Science can afford to be patient.  8)
Welcome to the forum! :) Don't forget to check out the lunatic SpaceX party thread... ;D
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline mgeagon

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If you are going to expend anyway, why not give your customer the most super-synchronous orbit possible? Or, continue to prove reusability. The grid fins add little weight, but provide immense aerodynamic control. The landing legs provide 1000 kg of added gravity losses and only a small portion of reentry drag. It is possible to surmise that this mission falls right on the cusp of recoverability and so SpaceX was left with a conundrum: It is too heavy to recover intact, but light enough to add the cleaned legs to test more aggressive profiles.

Offline Rocket Science

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If they filled the RP-1 tank to the max and had just enough LOX to get down...

Rockets always basically filled to 100% no matter what the payload mass is
Makes sense on a normal rocket to have as much margin as possible, but do you know for sure if this applies to the F9? The second stage can obviously dump it's excess fuel after the deorbit burn, but the first stage brings it home - seems like a bad idea if things go pear shaped.

F9 S1 can always use any extra fuel for a less-efficient but more gentle entry and landing.
The mission I'm specifically thinking of was formosat - the payload was tiny and it landed on the drone ship downrange. I'll go back and re-watch that mission, but I don't recall any sort of excessively long post sep burns.


They also need to keep extra margin on board in case of an engine out.  There are a number of engine failure scenarios that could still make orbit but would require the entire fuel margins leaving nothing left for return.
I would say that a full load adds to the structural integrity of the LV as well since liquids don't compress...
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Offline pb2000

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It is possible to surmise that this mission falls right on the cusp of recoverability and so SpaceX was left with a conundrum: It is too heavy to recover intact, but light enough to add the cleaned legs to test more aggressive profiles.
5400Kg is about max for block 3 recovery, this mission is well under @ 4230Kg.
« Last Edit: 01/31/2018 04:09 pm by pb2000 »
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Offline mgeagon

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Yes, it appears a “toasty” landing might be successful. It seems SpaceX wishes to expend this booster. The reasons seem obvious, they are running out of room for stored boosters and have block 5s on the way. Why stick on the landing legs? Why are they cleaned? We are curious about the answer.

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