Author Topic: F9 Block 5 Updates and Discussion  (Read 312801 times)

Online Lar

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Re: F9 Block 5 Updates and Discussion
« Reply #260 on: 04/06/2017 04:59 PM »
I am not sure how the grid fins are currently fabricated, maybe egg crate style out of Al plate and then welded, maybe cut out of thick plate and then curved. In any case, I think forging will give them much more design freedom.  They will be able to taper the vanes to make the lighter and more aerodynamic. They will be able to thin the elements smoothly from the root where strength is needed to the tip where loads are much lighter.

The shape from the ITS video shows some of this. I am very interested to see what they come up with given the freedom forging will allow, though at great expense. Tooling costs make getting this right the first time very important. Any guesses on how much three+ square meter dies for a gigantic press are going to cost?

1/5 the cost of one new stage...  (that's 8MM USD) at most??? That's a WAG. But I can get plastic molds for 16 different LEGO compatible parts cut in China for under 2 k if I'm working with a supplier I already worked with who wants the molding business too. (I have friends that do this for a living)... not at all apples to apples but I can't imagine the DIE costing more than the press itself. The PRESS? Sure, that's possibly in the tens of millions.
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Offline cscott

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Re: F9 Block 5 Updates and Discussion
« Reply #261 on: 04/06/2017 05:07 PM »


I am not sure how the grid fins are currently fabricated, maybe egg crate style out of Al plate and then welded, maybe cut out of thick plate and then curved.

I believe I've seen tooling marks on them in close-up photos that led me to believe they were CNC milled from block Al.

Of course, it's possible the CNC tool marks were from some post-processing clean up. But I don't recall ever seeing welding beads.

Offline virnin

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Re: F9 Block 5 Updates and Discussion
« Reply #262 on: 04/06/2017 07:56 PM »


I am not sure how the grid fins are currently fabricated, maybe egg crate style out of Al plate and then welded, maybe cut out of thick plate and then curved.

I believe I've seen tooling marks on them in close-up photos that led me to believe they were CNC milled from block Al.

Of course, it's possible the CNC tool marks were from some post-processing clean up. But I don't recall ever seeing welding beads.

Welding beads would be the first thing I would machine away to reduce turbulence.

Offline OneSpeed

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Re: F9 Block 5 Updates and Discussion
« Reply #263 on: 04/06/2017 09:59 PM »
Welding beads would be the first thing I would machine away to reduce turbulence.

That would dramatically reduce the strength of any weld. CNC of the current design is more likely, and forging of the larger titanium design.

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Re: F9 Block 5 Updates and Discussion
« Reply #264 on: 04/06/2017 10:19 PM »
Welding beads would be the first thing I would machine away to reduce turbulence.

That would dramatically reduce the strength of any weld. CNC of the current design is more likely, and forging of the larger titanium design.

In addition, some degree of turbulence is a good thing on lift-generating surfaces because it prevents flow separation. But more generally, look at the design of the fins themselves ... Even if they were utterly geometrically flawless, they should inherently produce fantastic turbulence already. You can't avoid it - too many individual cells, with flows through and around all of them, interesting shock waves, etc. 

Take a look here for more about grid (lattice) fins, generally:

http://www.aerospaceweb.org/question/weapons/q0261.shtml
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Online Semmel

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Re: F9 Block 5 Updates and Discussion
« Reply #265 on: 04/07/2017 06:05 AM »
Software engineer here, so please excuse my naive question. I have no idea what the differences between forging, welding and CNC are. I know roughly what the terms mean..

forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.

Ok, thats as far as my naive knowledge goes. How is it really and what are the implications for the grid fins?

Online RotoSequence

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Re: F9 Block 5 Updates and Discussion
« Reply #266 on: 04/07/2017 06:14 AM »
Software engineer here, so please excuse my naive question. I have no idea what the differences between forging, welding and CNC are. I know roughly what the terms mean..

forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.

Ok, thats as far as my naive knowledge goes. How is it really and what are the implications for the grid fins?

This mostly pertains to how you'd put the parts together, and their individual mechanical properties that come from it. I don't have a formal education in any of this, but to my understanding, forging introduces its own effects into the atomic structures of a work piece, as do welding and, to a lesser extent, CNC machining. If I recall correctly, CNC milling introduces the fewest defects or modifications to the crystal structure in the bulk material.
« Last Edit: 04/07/2017 06:15 AM by RotoSequence »

Offline mikes

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Re: F9 Block 5 Updates and Discussion
« Reply #267 on: 04/07/2017 06:34 AM »
Welding beads would be the first thing I would machine away to reduce turbulence.

That would dramatically reduce the strength of any weld. CNC of the current design is more likely, and forging of the larger titanium design.

If they already have an established CNC production method, why switch to forging?
From googling, I understand CNC milling of titanium has problems of heat transfer leading to combustion. Presumably choice of atmosphere (or maybe liquid medium?) can mitigate this.
Forging of such a complex structure would seem to me quite a challenge, but I have no experience with any of these processes (software guy!)

Offline cambrianera

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Re: F9 Block 5 Updates and Discussion
« Reply #268 on: 04/07/2017 08:14 AM »
Software engineer here, so please excuse my naive question. I have no idea what the differences between forging, welding and CNC are. I know roughly what the terms mean..

forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.

Ok, thats as far as my naive knowledge goes. How is it really and what are the implications for the grid fins?

The following indication are for complex shapes.
Forging: good use of material, high cost of tooling (dies and machinery), qualification of process important, medium/high workmanship required, working time short.
Welding: good use of material, low cost of tooling (jigs and machinery), qualification of process critical, medium/high workmanship required, working time long.
Machining: bad use of material, low/medium cost of tooling (jigs and machinery), qualification of process not important, low/medium workmanship required (CNC), working time long.
Added:
Casting: good use of material, low cost of tooling (dies and machinery), qualification of process important, low/medium workmanship required, working time short.

As per mech properties, see pic
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Offline Rei

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Re: F9 Block 5 Updates and Discussion
« Reply #269 on: 04/07/2017 10:00 AM »
Software engineer here, so please excuse my naive question. I have no idea what the differences between forging, welding and CNC are. I know roughly what the terms mean..

forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.

Ok, thats as far as my naive knowledge goes. How is it really and what are the implications for the grid fins?

The following indication are for complex shapes.
Forging: good use of material, high cost of tooling (dies and machinery), qualification of process important, medium/high workmanship required, working time short.
Welding: good use of material, low cost of tooling (jigs and machinery), qualification of process critical, medium/high workmanship required, working time long.
Machining: bad use of material, low/medium cost of tooling (jigs and machinery), qualification of process not important, low/medium workmanship required (CNC), working time long.
Added:
Casting: good use of material, low cost of tooling (dies and machinery), qualification of process important, low/medium workmanship required, working time short.

As per mech properties, see pic

You forgot extrusion  ;)  Grids can be extruded.  Of course, you'd need to be making a lot of fins to justify the tooling cost.
« Last Edit: 04/07/2017 10:02 AM by Rei »

Offline OneSpeed

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Re: F9 Block 5 Updates and Discussion
« Reply #270 on: 04/07/2017 11:31 AM »
... How is it really and what are the implications for the grid fins?

This is an excellent question, but to attempt to answer it completely in this thread might raise alarm bells with the mods.

You forgot extrusion  ;)  Grids can be extruded.  Of course, you'd need to be making a lot of fins to justify the tooling cost.

You could also produce a rough billet with additive manufacturing, and forge it to the final (or near final) shape. To piggy back off cambrianera's post, the general trend is that castings are weaker than bar stock, which is weaker than a forging.

Offline Proponent

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Re: F9 Block 5 Updates and Discussion
« Reply #271 on: 04/07/2017 11:39 AM »
What matters is reducing drag power, which is why entry heating is ~v³.

The rate of heat production goes as v³, but the heat delivered to the spacecraft may not.  It's possible, for example, to be in a regime where the heat on the spacecraft goes as v8.

Offline Dante2121

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Re: F9 Block 5 Updates and Discussion
« Reply #272 on: 04/07/2017 11:56 AM »

Any chance the new grid fins will pop open on ascent? 

Doubt it. When Musk talks about extra control and higher angles of attack being flown due to the new grid fins, I think he's talking about descent only. Higher angle of attack would then create higher drag on entry and allow prop savings for both the entry and landing burns.

Less fuel required for descent translates to more fuel available for payload to orbit = performance gains.

Offline matt_ellis

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Re: F9 Block 5 Updates and Discussion
« Reply #273 on: 04/07/2017 04:03 PM »
SpaceX are already using 3D printing for Super Draco engines ( http://www.spacex.com/news/2014/07/31/spacex-launches-3d-printed-part-space-creates-printed-engine-chamber-crewed ), so why not grid fins?  Draw in CAD, hit 'Print' and collect a few hours later.

Offline cscott

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Re: F9 Block 5 Updates and Discussion
« Reply #274 on: 04/07/2017 04:05 PM »
SpaceX are already using 3D printing for Super Draco engines ( http://www.spacex.com/news/2014/07/31/spacex-launches-3d-printed-part-space-creates-printed-engine-chamber-crewed ), so why not grid fins?  Draw in CAD, hit 'Print' and collect a few hours later.
Size.

Online meekGee

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Re: F9 Block 5 Updates and Discussion
« Reply #275 on: 04/07/2017 05:16 PM »
Software engineer here, so please excuse my naive question. I have no idea what the differences between forging, welding and CNC are. I know roughly what the terms mean..

forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.

Ok, thats as far as my naive knowledge goes. How is it really and what are the implications for the grid fins?

For all questions about manufacturing, youTube is your best pal.

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Offline koshvv

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Re: F9 Block 5 Updates and Discussion
« Reply #276 on: 04/07/2017 09:20 PM »
forging: Make metal hot and beat it with a hammer until it has the shape you want.
welding: Take small pieces of metal and glue them together by melting some of the metal where it touches.
CNC: Take a large block of material and scrape off everything you dont want.
Forging improves crystalline structure and makes piece stronger.
Welding worsens crystalline structure in melted material and make piece prone to break at joints. Advanced welding techniques reduce or eliminate melting.
CNC does not affect it.

Quote
what are the implications for the grid fins?
Forged grid fins will be stronger than ones with same mass but made by other methods. So they can make either lighter or bigger grid fins.
« Last Edit: 04/07/2017 09:21 PM by koshvv »

Offline RedLineTrain

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Re: F9 Block 5 Updates and Discussion
« Reply #277 on: 05/07/2017 01:53 PM »
F9 Block 5 is turning into quite a capable machine...

Quote
In terms of trends, Shotwell sees a trend of a bifurcation in the market. She says there are a couple of satellite providers making their satellites bigger. “Some of that is basically putting a giant satellite on Falcon 9 with a lot of propellant, which would normally be a very heavy satellite, even potentially hard for Falcon 9 to throw. But when you put so much propellant on that satellite, they can get themselves to orbit even from a sub-synch. A couple of manufacturers are doing that … [sending] an over 7-ton satellite on Falcon 9 to GTO. We are seeing a number of satellite manufacturers come around and do that just because of the value proposition presented by Falcon 9.”

http://interactive.satellitetoday.com/via/april-2017/shotwell-ambitious-targets-achievable-this-year/
« Last Edit: 05/07/2017 01:54 PM by RedLineTrain »

Offline DOCinCT

Re: F9 Block 5 Updates and Discussion
« Reply #278 on: 05/07/2017 04:33 PM »
SpaceX are already using 3D printing for Super Draco engines ( http://www.spacex.com/news/2014/07/31/spacex-launches-3d-printed-part-space-creates-printed-engine-chamber-crewed ), so why not grid fins?  Draw in CAD, hit 'Print' and collect a few hours later.
Size.
And complexity.  The Main Oxidizer Valve body inside a Merlin 1-D took 1 to 2 days to print.  It is basically an shaped cylinder with some cross pieces.  I imagine the SuperDraco combustion chamber took a bit longer, and it's about the size of a canister vacuum cleaner.

Online AncientU

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Re: F9 Block 5 Updates and Discussion
« Reply #279 on: 05/07/2017 07:05 PM »
A batch of grid fins is exactly the kind of fab run that is ideal for forging.
Cannot get either cheaper or higher strength than that.
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