Also, asbjos, what units should I enter when trying to do that equation?
Using my limit of [math]10^7 > 0.5 \cdot Density \cdot v^3[/math] and setting the velocity to escape velocity at Jupiter (60 000 m/s), you get that the density limit is approximately [math]10^{-7} > D[/math].
I don't know what model Orbiter uses for the atmosphere, but [math]Density = D_0 \cdot e ^ {-h / c}[/math] is often used in very simple models, where [math]h[/math] is the altitude, [math]D_0[/math] is density at the "surface" and the constant [math]c[/math] is the [ame="http://en.wikipedia.org/wiki/Scale_height"]scale height[/ame] of Jupiter's atmosphere.
I used Orbiter's value of [math]D_0=1.329 kg/m^3[/math], and found the scale height
here to be [math]c=27000 m[/math].
Solving for the altitude gives us the altitude to be approximately [math]h > 445 km[/math].
(I'm assuming the "v" means velocity)
Yes, [math]v[/math] is the velocity. To find the limits of the probe, we use maximal velocity at minimum altitude, in other words the velocity at the perigee.
Also, would that 1 x 10^7 equal to 10 million?
Yes, [math]10^7[/math] is a 1 with 7 zeros, or 10 million (10 000 000).
Just curious, because I'm trying to figure out how to aerobrake in the Martian atmosphere to get an orbit so I can intercept the Martian moons.
In general, assuming that assumptions for velocity, scale height, surface density and atmosphere model is correct for Orbiter, the equation for every planet is
[math]h > -c \cdot \ln \frac{2\cdot 10^7}{D_0 \cdot v^3}[/math]where [math]h[/math] is PeA (surface altitude at perigee, and therefore minimal altitude allowed by the Chapman Modules), [math]c[/math] is the scale height which you will have to find on the internet for your specific planet, [math]\ln[/math] is the [ame="http://en.wikipedia.org/wiki/Natural_logarithm"]natural logarithm[/ame], [math]D_0[/math] is the surface density which can be found in your planet's config file or found manually by placing yourself on the surface and reading the DNP reading in Surface MFD and [math]v[/math] is your velocity (for example the escape velocity at the surface, as an approximation).
If you don't know your velocity at the surface, you can break the equation down even further, and use this:
[math]h > -c \cdot \ln \frac{2\cdot 10^7}{D_0 \cdot \sqrt{\frac{2 \cdot G \cdot M}{R}}^3}[/math]where [math]G[/math] is the [ame="http://en.wikipedia.org/wiki/Gravitational_constant"]gravitational constant [/ame] always at [math]6.67 \cdot 10^{-11}[/math], [math]M[/math] is the mass of your target planet and [math]R[/math] is the radius of your target planet.
I made a spreadsheet for experimenting and calculating your own altitudes. You can also set the velocity to something other than the escape velocity, to make it more realistic. To calculate and set input for yourself, press "File"-->"Download as" and open the downloaded file to get editing privileges.
https://docs.google.com/spreadsheets/d/1SWxHw1WSz_sXHTtK-of3zIAcWXoj1RCAtYcpbzCkS30/edit?usp=sharing
