# What's the atmospheric drag coefficient of a Falcon 9 at launch (sub-sonic, large fairing)

While I said just a few hours ago that "There's almost no such thing as a dumb question! this one just might sound like one.

I'm making some slides about first principles thinking applied to engineering problems, and Elon Musk has several good quotes, one for example at a TED talk where near the end he says something like “...boil things down to their fundamental truths and reason up from there.” I'm using both Tesla model S and Falcon 9/Falcon Heavy as examples.

For the Tesla Model S, you can get the approximate required battery size easily from a range and speed (400km, 110kph), cross-sectional area (25 square feet), and drag coefficient of 0.24, plus the rolling resistance of good tires, 90% overall efficiency and another kilowatt or two for air conditioning, computer&display, and maybe some music.

I wanted to add the drag coefficient of a Falcon 9 rocket as a tangential comment only. I don't need an exact number, but something in the ballpark, and I have no idea where to begin.

Assume sub-sonic, flying straight, with a reasonably large payload fairing. It doesn't have to be a Falcon 9 - any rocket somewhat representative is fine.

If there is a plot of drag coeficient vs speed that extends to supersonic, that would be really very helpful also. This is back-of-the-envelope I'm doing here.

Is it better or worse than the "Long Cylinder" below?

• Braeunig's Saturn V simulation page has a graph of Cd versus Mach number; it's a rough approximation based on the figures for the Atlas rocket, but better than nothing. Jun 29, 2016 at 17:02
• Indeed, there is useful discussion and plots at http://www.braeunig.us/apollo/saturnV.htm.
– uhoh
Jun 29, 2016 at 22:07
• That page is, like, the source of 1/3 of my points on here. Jun 30, 2016 at 2:20
• Oops! Didn't mean to reveal trade secrets.
– uhoh
Jun 30, 2016 at 4:55
• Haha, not at all -- I normally link it, but I was on my phone when I made my first comment. Jun 30, 2016 at 14:47