Closing Air Intakes - Does it affect drag ?

[Gavin786]

I was told by a senior KSP expert who I respect a lot that closing air intakes reduces drag and one should do it once an engine stops breathing and your spaceplane enters the upper atmosphere.

I have done some tests and am finding it difficult to come to this conclusion.  Opening and closing air intakes seems to have no or negligible effect on drag in the AeroGUI menu from the Alt-F12, or on the part aerodynamics info itself.

Can anyone shed light on this, does closing air intakes have any effect on drag?  Have I been misinformed ?

Thanks guys.

[Serenity]

1 hour ago, Gavin786 said:

I was told by a senior KSP expert who I respect a lot that closing air intakes reduces drag and one should do it once an engine stops breathing and your spaceplane enters the upper atmosphere.

I have done some tests and am finding it difficult to come to this conclusion.  Opening and closing air intakes seems to have no or negligible effect on drag in the AeroGUI menu from the Alt-F12, or on the part aerodynamics info itself.

Can anyone shed light on this, does closing air intakes have any effect on drag?  Have I been misinformed ?

Thanks guys.

Most say it was a really early feature and it was supposed to had a good amount of drag effect.

But for some reason that doesnt seem to be the case in newer versions.

Personally i failed many times to find any serious changes in drag, 

Maybe its just hat,  a feature that just didnt make it for various reasons in the newer versions of the game.

 

Edited August 7, 2020 by Boyster

[RyanRising]

Hey, that's a good question! I figured I should test that - the aero model changed in 1.0, so if it has been changed it would have been before that. Warning, images below.

Spoiler

I have a copy of 0.20.2, so here's my setup:

And in flight. The two boosters closest to the camera have their intakes turned off, whereas the two farther from it do not. It looks like there at least was some effect.

Eventually, the two with open intakes veered off course, whereas the two with closed intakes stayed mostly true.

For completeness' sake, I loaded the same craft file in my 1.10.1 testing installation (game gave me an error trying to load it, but it seemed fine. Looks like they kept the old SRB model too!):

And I observed no change in drag (again, two closest to camera had their intakes closed. I didn't get a very level shot, sorry about that, but trust me they were at the same height.)

Also turns out that configuration is pretty unstable. Who knew?

 

 

Conclusion: Closing intakes did indeed reduce drag as of 0.20.2 (which had the old aero model) and does not reduce drag in 1.10.1 (which has the new aero model.) I suspect that this change happened with the aero model changeover, but I would need 1.0 and 0.90 in order to confirm this.

Edited August 18, 2020 by RyanRising