So, after looking at all the stuff those geniuses up at NASA came up with, I'm trying to figure out how to get the drag coefficient for the Apollo 13 command module reentry. Heres the stuff I thought were important: Entry-interface 400,000 ft 36,129fps Drogue chutes deploy at 23,000 ft, slowing module down from 300mph to 175 mph. So, 300mph is 1584000fph or 26400 fps. So, 36,129fps - 26400fps = 9729fps. If the Ei is at 0:00 then the Drogue chutes open at 8:16, or 496 seconds, divide 9729 by 496 and you get the speed lost per second, which would be 19.61fps. The equation is Cd=drag/(.5*pAV^2) I have no idea where to go next. I don't know how to convert what I have into drag, and the density of the fluid is always changing. I have a chart that shows the relation between altitude and air density, but I can't find a way to put all of it in without doing a new equation for each step in altitude. So both velocity and air density would be constantly changing, the only constants are the .5 and the A. This project is due on Thursday, so any help would be awesome.