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?
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.
Quote from: matthewkantar on 04/06/2017 04:39 pmI 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.
Quote from: virnin on 04/06/2017 07:56 pmWelding 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.
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?
Quote from: Semmel on 04/07/2017 06:05 amSoftware 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
... How is it really and what are the implications for the grid fins?
You forgot extrusion Grids can be extruded. Of course, you'd need to be making a lot of fins to justify the tooling cost.
What matters is reducing drag power, which is why entry heating is ~v³.
Quote from: cscott on 04/01/2017 11:34 amAny 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.
Any chance the new grid fins will pop open on ascent?
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.
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.
what are the implications for the grid fins?
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.”
Quote from: matt_ellis on 04/07/2017 04:03 pmSpaceX 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.