Calculating Water Rocket Performance: Thrust, Velocity & More

In summary, the water rocket will be made out of a coke bottle and it will start with about 300-800 mL of water. The thrust will decline as the air expands and the mass to be accelerated also declines. The height of the rocket will be calculated using 0.122g(tend)2 and 0.
  • #36
Help. Anyone? This is due in a few hours and I don't know how you got the volume of air so low when I get 0.001 cubic meters and that ruins the whole spreadsheet as it must be, apparently, at least 0.0001 cubic meters to take any effect.
 
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  • #37
Alcubierre said:
Help. Anyone? This is due in a few hours and I don't know how you got the volume of air so low when I get 0.001 cubic meters and that ruins the whole spreadsheet as it must be, apparently, at least 0.0001 cubic meters to take any effect.
This is probably too late. I plugged in Vf = .002, P0 = 4*atmospheric ("=4*I2"), M = 0.5, A = 0.002 (pi*.025^2). I played around with V0 to maximise height. I got nearly 5m at V0 = 0.00113. But go just a fraction over that and you lose big time.
Not sure about P0. If your gauge says 45 psi, is that 3 atmospheres, or 3 atmospheres in addition to the background 1 atmosphere? I'm assuming it's the second.
 

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