This is the dependence of the maximum angle of attack on the relative thickness of the lattice profile
с=с/b
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You misunderstand. The basic design of the falcon 9’s grid fins optimized drag in comparison to grid fins used on missiles. The grids are extremely thick and flat. This is not beneficial to the control of the rocket, instead only improved the terminal velocity by increasing drag.
All launches are filmed.
The control authority was already there. The titanium fins didn’t need to be so much thicker, but they are. The peaks allow better flow in spite of the thicker fins. Optimization in all areas.
Is inches thick necessary for re-entry? I don’t think so. It’s considerably thicker than the aluminum fins. This wouldn’t be necessary.
I wonder how they stabilize the pod if they don’t move? Perhaps drag?
The general lack of understanding of grid fins is why people fail to understand the R-77 around here.
@MiG_23M
And here is drag compared to the grid size (source):
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Meaning larger “holes” create less drag.
old and new fins on Falcon 9 compared:
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Notice how the holes are significantly larger, to reduce drag.
Edit:
here is a test done on difference in making thin/thick compared to making larger holes:
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You still don’t understand, the fences themselves are thicker and flat. This is not ideal for reducing drag. More spacing was required in part of the lattice to even allow any flow at higher mach numbers.
Edited to include test of thin walls, note how the size of holes matter more.
they also didn’t change the thickness of the walls between the versions.
the thickness could be to make them reusable and withstand the forces and heat, not for more drag.
This is of grid fins optimized to reduce drag, this isn’t relevant
This would be for an air to air missiles and not as a method of increasing drag - the opposite.
its very relevant, it shows the change in drag when changing only wall thickness and changin only hole size.
highly relevant as the change for Falcon nine was larger holes, but no change in wall thickness. meaning less drag.
You are not observing the taper, or considering the additional area of the lattice from the extension or the peaks. There is a reason they have foregone using the landing gear as a method of reducing the terminal velocity.
This is called the grid step and the number of plans
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the increased area from the peaks results in higher drag and better control at angles, not at zero alfa.
if you want them as air brakes you want the higher drag when not angled.
The peaks are added to make the zero alfa drag less.
the additional area would not increase the drag more than the peaks decreases it at zero alfa.
that is the function of valleys.
i have yet to se a source on this. until you provide one i have only seen statements of the opposite and will believe as such.
The rocket maintains ~20° AoA in descent to slow down, increase drag, and avoid wasting fuel. Once it is subsonic, slowing down is not necessary and control is transferred mostly to the engines TVC systems.
Elon Musk stated it himself and I already provided the source.
The peaks were added to ensure proper flow in spite of the thicker grids, improving control in several regions and also providing additional drag.
the alfa refers to the angle of the fin in relation to the airflow, not the rockets angle.
could you link to it? i have not seen it and i cand find any when i search.
just… no? i don’t know where you get that the peaks increase drag. they reduce it.
That’s because it is reducing the surface area by at least 50%
If you increase the size of the holes, but keep the surface area the same, the drag is minimally affected.
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well yes. but that would be counter productive as you would have less area for steering and more area for drag.
so its a question of reducing area by making the walls thinner or holes bigger to achieve less drag.
I’m aware…?
Depends on angle
then why did you bring up the rockets angle?
exactly what i’m trying to say, if you want air-brakes, you want them to have high drag at zero angle. which peaks avoids.
this says the exact opposite? that they do use the legs as airbrakes.
" […] look at our landing gear, they’re essentially like giant body flaps, so the drag - when we deploy the landing gear, the drag massively increases, so we have dual use of the landing gear as giant body flaps and as landing gear. That actually cuts the terminal velocity in half and therefore the fuel - the propellant we need to stop the vehicle in half, and actually it’s quite an efficient method of landing precisely."
there is nothing in there about them taking the legs away or stopping using them as airbrakes?
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Peaks allow better control across a wider range of conditions when the grids themselves are so thick.
The fins are not neutral when the rocket itself is held at 20° …?
That they did, as I said they did. They stopped when they switched to the thicker titanium fins. The launches and landings are all recorded.
by reducing wave drag. reducing… drag…
they do NOT increase inherit drag.
are you saying they are angled constantly when not used for steering?
there is nothing in that source using past tense. there is nothing in that source indicating a change of legs occurred. you have not provided a source for any potential new legs not being used as air brakes.