paper: Parabolic Trajectory Calculations

[Hugh Meyer]

Thank you.

We do not have any data, but we have been talking about it. How would we measure the terminal velocity?

-Hugh

[Ether]

Originally Posted by Hugh Meyer

How would we measure the terminal velocity?

I don't know for sure; I've never done it. Perhaps drop the ball from a sufficient height next to a marked wall in a tall room and take high speed video with a camera that timestamps the frames. Then tweak the value of Terminal Velocity in this spreadsheet until the model matches your data.

I just posted a small revision (revC) to the air-drag spreadsheet. I turned off the auto-scaling in the graph and re-shaped it so the launch angle "looks" more like the real thing. It may make it easier to visualize what's changing when you change the input parameters. The downside is you lose some resolution.

http://www.chiefdelphi.com/media/papers/2946

[Ether]

Given launch speed and a desired point (d,h) on the trajectory, show the derivation of and formulas for the launch angles and the equations of the two parabolic (no air drag) solutions.

http://www.chiefdelphi.com/media/papers/download/4614

[GeeTwo]

Originally Posted by Hugh Meyer

How would we measure the terminal velocity?

My first thought is a football stadium and a radar or ultrasonic speed gun. The procedure is pretty obvious.

If you don't have a speed gun, a strobe of some sort, including the video method suggested by Ether would be next.

As for 3946, we did the air-resistance-free calculation, added about 50%, tested that we had more than we needed to hit the goal at the ranges we wanted, then we'll back down based on empirical launch data until we hit the goal at the desired range (this year, with our rear bumper in the outer works). Not as elegant as the full-physics solution, but we've built several high-percentage launchers using this paradigm.