# Atmospheric Density

1. Jun 22, 2008

### ZachWeiner

Hey, does anyone have an equation that roughly models atmospheric density from sea level to about 200 km up?

2. Jun 22, 2008

### Phrak

There's not much of an equation for atmospheric pressure that's simple. If you have a CRC handbook you could look up a few values. You should know, as well, that it's quit variable at higher altitudes, dependent on solar activity.

3. Jun 23, 2008

### aniketp

Hi ZachWeiner,
Pressure at a height "h" is given by :
P=(Patm)*e^(-Mgh/RT) [Patm is the pressure at sea level]
And D=PM/RT
But there is an assumption that T is const. this formula will only enable you to calculate the density roughly. So do not use it if you want accurate answers.

4. Jun 24, 2008

### Phrak

I have no excuse for it, but in response to this question, I actually tried an exponential curve of pressure vs. height, and fit it to two points of data; sea level and 100 Km. It was off by 28% at 50 Km. Very disappointing.

To get a decent curve fit, P = P0 * exp(ah^3 + bh^2 + h) might do it.

5. Jun 25, 2008

### James3849

what do you need to model it for? pretty much any fluid mechanics text will tell you in a table at the back.

lol.. if u really want to model it, put all the numbers into excel and graph it

6. Jun 30, 2008

### nucleus

Last edited by a moderator: May 3, 2017