How to find frictional and pressure induced drag on a rocket

[Mach3.0]

Trying to calculate the max weight my rocket can carry and still get to a mile high, but I need to be able to create a force vector for drag so I can figure it out. And ideas?

 

[neil_w]

Do you need to be doing this by hand for some reason, or can you just enter the rocket into OpenRocket or Rocksim and find out that way?

 

[Alan15578]

The traditional and most reliable way is to measure the drag in an instrumented wind tunnel.

 

[Scott_650]

Here’s how Tim Van Milligan explained calculating drag coefficients without a wind tunnel: https://www.apogeerockets.com/education/downloads/Newsletter303.pdf

Could be helpful as at least a starting point.

 

[cls]

in fact, the wind tunnel work is already done, for conventional shapes, up to Mach 2. Its called DATCOM. it has some warts (underestimates drag of conical noses). but it is already incorporated in to Rocksim and Open Rocket.

Trying to calculate the max weight my rocket can carry and still get to a mile high, but I need to be able to create a force vector for drag so I can figure it out. And ideas?

make a weight accurate and finish accurate simulation of your vehicle in Open Rocket. Adjust the atmospherics in the sim to be exactly as at your launch site. Fly the rocket, compare actual altitude (barometric) vs simulated altitude. Override the simulation Cd to match.

there, calibrated simulation with exact drag and other forces.

now try simulating using different motors.