# Why would a significant non-zero angle of attack be an advantage during 1st stage burn?

From videos of both the SES-10 launch shown in @RusselBorogrove's question, Cause of apparent plume deflection on SES-10?" and the Block 5 launch Bangabandhu Satellite-1 Mission at T+ 01:48 it appears the Falcon 9 uses non-zero angles of attack (or displacement angle) during the 1st stage burn.

The exhaust plume is aligned with the flight path (high dynamic pressure) and it's obvious the vehicle's roll axis isn't.

I believe the visual effect is due to the rocket flying a small positive angle of attack at the end of the first stage burn, combined with a steeply foreshortened camera view.

According to the simulation data at FlightClub (https://www.flightclub.io/results/?code=SS10), the rocket flies a positive angle-of-attack during the end of the first stage burn, peaking at about 4.6 degrees AoA.

left: screen shot from Bangabandhu video, right: SES-10 from here. Click for larger size.

• Can you add a screen shot? See for example these questions 1, 2, 3, 4 – uhoh May 13 '18 at 4:48
• Would do it if I knew how. As I mentioned a few days ago, I've been doing professional space exploration for a long time, but I'm new to online stuff. Still on the learning curve. – Tom Spilker May 13 '18 at 5:05
• Can see the result of what you did (time tag icon, screen shot inserted) but not how you did it. – Tom Spilker May 13 '18 at 5:40
• I did everything using the keyboard except for importing the screenshot. To import images, you use the "image" tool at the top of the edit window. See this guide: i.stack.imgur.com/BcK5Q.png To get a short link to a question or an answer, look for and click share below the post. It pops open a small window. You just use your keyboard shortcut for copy and then it's in your copy/paste buffer. See this guide: i.stack.imgur.com/GuUF0.png – uhoh May 13 '18 at 5:45
• slightly related: Is aerodynamic lift ever useful in rocket flight? – uhoh May 13 '18 at 6:01

• +1 great edit, thanks! – uhoh May 17 '18 at 2:22