Water Rocket Computer Model Problems

Here is the third Water Rocket Computer Model Problem.

The screen shot below is from the 3D optimisation of the default 2 litreRight Click and Zoom In to see better or Left Click to show full screen. water rocket.

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

It is a plot of Distance Downrange as the output variable with Angle of Elevation (39.3g to 47.9g) on the Y axis and Mass of Rocket Empty (190.5g to 260.4g) on the X axis with a post-thrust integration interval of 10ms.

The maximum shows a number of diagonal lines that run all of the way across the display.

Variables
Water Rocket Computer Model Problem 03    
Rocket
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 21.5   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 21   mm
[X] Hollow Launch Tube Used    
Wall Thickness 2   mm
Length of Tube Empty 25   cm
Distance of Vent from End 0   cm
[ ] T-Nozzle in use Not Used    
T-Nozzle Diameter 4.75   mm
Parachute
Diameter opened out flat 1.2   m
Parachute Coeff of Drag 0.9    
Deploy () Apogee.( ) Timer 4   s
Delay in opening 5   m
Initial
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
Environmental
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 diagonal lines.


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.


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