Talk:Atmosphere

Drag calculation notes

The calculation for the drag force as listed on this wiki page is incorrect. The units for the equation provided would be (Kg^2*m)/(s^2) when the unit of force (N) is Kg*m/(s^s). The equation should not include the mass of the craft as the mass of the craft has nothing to do with the amount of drag exerted on it.

Remember that F=ma is a very simplified version of Newton's second law. The real way to read the equation is the sum of all instantaneous forces on a body is equal to the instantaneous mass of the body multiplied by the instantaneous acceleration of the body. It is actually more helpful to think of this drag force calculation in the context of Newton's third law.The craft is accelerating the air particles it contacts (or the pressure zone ahead of it contacts) and the equal but opposite force is applied to the craft. The mass that matters when determining aerodynamic forces is the mass of the disturbed air and this is why the density of the disturbed fluid is part of the calculation.

Edit:

Before writing this I did not see the mention to this fact in the wiki page, but I am still not sure why a force would be modeled with completely wrong units. It is not to make the amount of drag be independent of the craft's mass because, as I explained above the drag equation does not consider the craft's mass. Are the internal modeling calculations all done in mass specific forces/accelerations? If so, shouldn't the true drag force then be divided by the craft's mass to yield this value? --T0w0i7ne (talk) 15:48, 15 July 2013 (CDT)

First of all, this biiiig paragraph isn't very readable. I actually only read some of it and I'm asking you: Do you complain, that the formula here is not real world compatible? Then I reference to: “Note that the m term is not present in the real-word drag equation. In the game, this causes acceleration due to drag (a = FD / m) to be unaffected by a ship's mass. (It also causes the units of the drag equation to have an extra "kg" term.)”. By the way, please sign your posts with --~~~~. — xZise [talk] 16:26, 15 July 2013 (CDT)

I misread that section once I saw it. I now understand the desire was to make the acceleration of the craft due to the force of drag be independent of the mass of the craft. What is the point in such an approach when the reality is precisely the opposite? What does this gain in the simulation? I don't see that this would be any simpler to code or that it would use drastically less CPU cycles. Please excuse my ignorance of wiki etiquette, I am now in the process of learning how to make nicer posts (after an attempt to clean up the above atrocity). I was originally under the impression that this discussion page was more like forum postings. --T0w0i7ne (talk) 22:39, 15 July 2013 (CDT)

Now about the physical simulation, I have no idea. Maybe this should be asked on the IRC. As I don't know how they calculate the crosssection of the craft, they maybe tried to make that calculation easier and don't calculate the cross section as precise as it needed and instead they estimate a heavy craft has a bigger cross section. I don't know ;). About etiquette: In a forum you can see who posted a post, but here it is harder without the signature. And it is always nice to know who you are talking to. — xZise [talk] 05:19, 16 July 2013 (CDT)