Water Rocket Computer Model Problems

Here is the eighth Water Rocket Computer Model Problem.

This Right Click and Zoom In to see better or Left Click to show full screen.is a fairly normal water rocket running at 100 psi.

I have included the file details so that you can reproduce it yourself to investigate the peculiar nature of the maximum displayed in the screen shot on the right.

It is a plot of Distance Downrange as the output variable with Mass of Water (10g to 1500g) on the Y axis and Nozzle Diameter (2.0mm to 9.0mm) on the X axis with a post-thrust integration interval of 10ms.

The graph shows a long maximum that runs along the edge of the viable range.
At the cursor, the nozzle diameter is 4.33mm and this produces a downrange distance of 92m whereas at the right hand side (with the same weight of water - 606g), the downrange distance is only a tenth of this. What is the explanation?

Water Rocket Computer Model Problem 08    
Mass of Rocket Empty 120   g
Capacity of Pressure Vessel 2050   cm3
Rocket Diameter 9.5   cm
Rocket Coeff of Drag 0.56    
Nozzle Diameter 10   mm
Constant K for nozzle 0.16    
[ ] Launch Tube in use Not Used    
Duration of air impulse 50   ms
[ ] Parachute in use Not Used    
Launch Tube
Length 20   cm
External Diameter 75   mm
[X] Hollow Launch Tube Used    
Wall Thickness 2   mm
Length of Tube Empty 25   cm
Distance of Vent from End 0   cm
[X] T-Nozzle in use Used    
T-Nozzle Diameter 4.75   mm
Diameter opened out flat 1.2   m
Parachute Coeff of Drag 0.9    
Deploy () Apogee.( ) Timer 4   s
Delay in opening 5   m
Mass of Water 850   g
Pressure in Vessel 100   psi
Height 1.5   feet
Angle of Elevation 88  
Speed at Angle of Elevation 0   m/s
Temperature 10   C
Gamma of Gas in Rocket 1.402    
Density of Gas in Rocket 1.293   kg/m3
Density of Liquid in Rocket 998   kg/m3
Acceleration due to Gravity 9.81   m/s2
Atmospheric Pressure 1013   mBar
Density of Air at STP 1.293   kg/m3

The problem here is . . .
1. to find an explanation for the maximum being positioned so closely to the edge of the viable range.

The variables are in the table on the left...

If you give up or you think you know what is going on, look at the answers.

Back to the Computer Model Page
Back to the Water Rocket Index
Site Map