Using airbrakes

[Kelderek]

Does it matter which way you place airbrakes on your ship? Take these two (crude) examples:

<-- direction of flight ______/__

or

<-- direction of flight ______\__

The top one is more deflecting the air away, and the bottom one is more like scooping it up. I've tried both setups and it's hard to tell if there is a difference. Does it matter in KSP?

[Xannari Ferrows]

Drag is modeled based on the axial cross section of the part in question, rather than the direction of airflow. While technically both would produce the same amount of drag, the bottom example will generate lift as well, making you lose velocity to gravity.

[quietghost]

I think it depends only on the drag cubes involved, so the result would be the same in either situation. However the forward facing airbrake may also add a downward force component, or vice versa with the backwards. Regardless, any aerodynamic lift generated does not absorb velocity unless altitude is gained. Deflection drag does, but that is not lift.

[Kelderek]

Thanks guys.

I've been having some frustrating problems with re-entry at Eve and most of it relates to air brakes.

1. Air Brakes seem to be bugged with respect to using them in action groups. I added some to a couple action groups in the VAB, but they do not work once launched. I can only activate them using the brake key, but that toggles ALL of my air brakes, which I don't want.

2. Why don't I want all of my air brakes to open together you ask? I have to use them to keep my ship pointed retrograde during the descent into Eve's atmosphere, but they can't take the heat from that and break off. I wanted to use one set of air brakes until they broke away and then turn on a second set, but that doesn't work without action groups. I'm not sure how else I can keep my ship pointed retrograde as every time I get below about 60km it starts to tilt about 20-30 degrees off retrograde and no amount of reaction wheels can correct it, but air brakes in the back far from the CoM will hold the craft straight (lawn dart effect).

I'm beginning to think that Squad hasn't tested any of the new aero stuff with Eve at all.

[11of10]

Airbrakes don't react to "Toggle" setting in action groups. You can use "Extend" and "Retract" options however.

[xtoro]

I've used them in both directions because I was curious as well. But I didn't notice a difference, at least nothing I could tell in-game. Is there actually a small difference in position?

[cybersol]

I think Claw has fixed the airbrakes and action groups problem in his Stock Bug Fixes mod, if that would help you.