Water Rocket
Computer Model Problems
Here is the second Water
Rocket Computer Model Problem.
The screen shot below is from the 3D optimisation of a
2 litre water rocket with an
unusually light body weight.
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 flight time as the output variable
with Mass of Water (20g to 1444.5g) on the Y axis and
Mass of Rocket Empty (1.1g to 19.7g) on the X axis.
It is clear that the longest flight times will be
gained from a moderate weight that is greate enough to
pull the rocket through the air but not so great that the
rocket cannot achieve a good enough height. This maximum
is off to the right.
| Variables |
| Water Rocket Computer Model Problem 02 |
|
|
| Rocket |
| Mass of Rocket Empty |
120 |
|
g |
| Capacity of Pressure Vessel |
2050 |
|
cm3 |
| Rocket Diameter |
9.5 |
|
cm |
| Rocket Coeff of Drag |
0.78 |
|
|
| 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 |
75 |
|
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 maximum at the top
left; and, |
| 2. |
the
maximum at the lower left. |
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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