I have a model rocket and I want my rocket to reach specific height above the ground level. As soon as desired height is reached, an air brake (umbrella type) is allowed to deploy. In order to have higher drag, what is the best position for the air brake? Will I obtain same drag if the air brake is below or above the Center of Gravity (CG)? Is Cd different for different locations of the air brake (having same surface area)?

Note: Although this question is about a rocket, this really has to do with aerodynamics.

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    $\begingroup$ Does the rocket need to remain in stable flight once the airbrake deploys? Because deploying this far enough above the CG can make it tumble. $\endgroup$ – AEhere supports Monica Jul 20 at 15:09
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    $\begingroup$ So here's a thought...if it's just a sounding rocket, why not just decrease the amount of fuel such that when it reaches your desired height the upward speed is minimal? I would like to understand why air brakes would be needed to arrest ascent $\endgroup$ – JZYL Jul 20 at 15:27
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    $\begingroup$ I’m voting to close this question because it belongs on Space Exploration. $\endgroup$ – FreeMan Jul 20 at 17:27
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    $\begingroup$ I would keep this open, as it involves aerodynamics. $\endgroup$ – Jpe61 Jul 20 at 18:52
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    $\begingroup$ this question is clearly on the edge between both space.SE and aviation.SE. OK sounding rockets are on space.SE, but rocket aerodynamics involved on missiles are on aviation.SE. Thus, this question also belong to aviation.SE. $\endgroup$ – Manu H Jul 21 at 13:41

If you want to arrest ascent you put the airbrake behind/below the CG. Keep in mind the rocket will tend to remain flying "nose first", which may affect parachute deployment (from nose) on the way down.

Notice the Space X Falcon 9 has theirs near the nose allowing the rocket to descend tail first, and are only deployed once the rocket has coasted to maximum altitude, slowed down, and has begun to fall. Nearer to the ground, you use retrorockets and/or parachute.

For a high altitude sounding rocket, it may be preferable to delay parachute deployment, lest the wind carry it too far away from the launch point.

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