5 ms·

I was surprised that during the initial ascent footage from the fin-cam, you can see that the grid fins are out. Do they not fold back on ascent? Or possibly dr

I was surprised that during the initial ascent footage from the fin-cam, you can see that the grid fins are out. Do they not fold back on ascent? Or possibly drag on one side to arc over? Just seems weird to have your “drag device” deployed during ascent.

malfist 3y ago
They're control surfaces, they help keep the pointy end up and the flamey end down
grecy 3y ago
They fold in/out on Falcon 9, but for the starship booster the decided it's not worth it. The extra weight and complexity to fold them in/out doesn't provide enough of a benefit. Elon talked about it a couple of years back on one of Everyday Astronaut's videos.
Laremere 3y ago
Grid fins aren't drag devices. They are control surfaces. As long as they are oriented so the fins are aligned with the airflow, they have no effect on orientation. The benefit of not folding them in is one less part that can fail. There might be a slight reduction in drag by folding them in, but not much and apparently not worth it.
- dylan604 3y ago
  I'm guessing 33 Raptor engines won't feel the effect of whatever drag those fins might produce. Instead, they'll just drag that drag into space
- russdill 3y ago
  The side edge of the grid fin may have more surface area than edge on.
  - panick21_ 3y ago
    Not sure they can turn that far.
    - russdill 3y ago
      I'm saying if you could fold the grid fin, the surface area presented may be as high or higher than the surface area presented when unfolded.
dotnet00 3y ago
I think that between the high TWR allowing the vehicle to spend less time in the thicker parts of the atmosphere and the lower pressure 'wake' the ship on on top would produce, there isn't as much drag over the fins as one might think. IIRC it was one of their various "delightfully counter-intuitive" discoveries during earlier testing.

5 ms·

I was surprised that during the initial ascent footage from the fin-cam, you can see that the grid fins are out. Do they not fold back on ascent? Or possibly dr

by travisgriggs 3y ago

malfist 3y ago
They're control surfaces, they help keep the pointy end up and the flamey end down
grecy 3y ago
They fold in/out on Falcon 9, but for the starship booster the decided it's not worth it. The extra weight and complexity to fold them in/out doesn't provide enough of a benefit. Elon talked about it a couple of years back on one of Everyday Astronaut's videos.
Laremere 3y ago
Grid fins aren't drag devices. They are control surfaces. As long as they are oriented so the fins are aligned with the airflow, they have no effect on orientation. The benefit of not folding them in is one less part that can fail. There might be a slight reduction in drag by folding them in, but not much and apparently not worth it.
- dylan604 3y ago
  I'm guessing 33 Raptor engines won't feel the effect of whatever drag those fins might produce. Instead, they'll just drag that drag into space
- russdill 3y ago
  The side edge of the grid fin may have more surface area than edge on.
  - panick21_ 3y ago
    Not sure they can turn that far.
    - russdill 3y ago
      I'm saying if you could fold the grid fin, the surface area presented may be as high or higher than the surface area presented when unfolded.
dotnet00 3y ago
I think that between the high TWR allowing the vehicle to spend less time in the thicker parts of the atmosphere and the lower pressure 'wake' the ship on on top would produce, there isn't as much drag over the fins as one might think. IIRC it was one of their various "delightfully counter-intuitive" discoveries during earlier testing.