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Water Rockets

  1. Oct 10, 2008 #1

    I have recently started a Matlab course and I have been given a task to write a simple water rocket simulator using function files and a main script. I really don't know where to start and feel over whelmed tackling such a huge task, not knowing anything about water rockets.

    I would like the simulator to predict from the two user inputted values (vertical altitude and mass of the empty rocket) the required weight of water and air pressure to achieve the desired parameters. The rocket is to be modeled on a standard 1.25 liter drinks bottle. Any information on where to begin would be very much appreciated.

    Many thanks

  2. jcsd
  3. Oct 10, 2008 #2
    I would start by reviewing the basic principles or momentum. That is, conservation of momentum and how change in momentum relates to thrust.

    Also, have a look at simple kinetics of projectile motion. A little bit of calculus will be involved for this part of the project, but not much.

    Lastly, look into polytropic processes, but more specifically compression of an ideal gas. You will need this to determine how much energy from the compression of the gas will be required to get your rocket to the correct height.
  4. Oct 10, 2008 #3


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    Are you actually going to test the results with real plastic bottles? I'm not sure how much pressure these will take.
  5. Oct 10, 2008 #4
    Use bottles of carbonated drinks, (such as pepsi, coca cola, fanta etc)... these can withstand more pressure (than the bottle of non-carbonated drink). Max pressure is roughly 10 bars, before it gets blown apart. It also depends on the state of the bottle... if you use duct tape, you can get pressure even higher. Max value is mostly useless and unsafe, so find some more suitable number. Rockets I have seen used like 4 bars, this seems quite enough for a safe takeoff.
  6. Oct 15, 2008 #5
    Hi All,

    I have spent the weekend compiling the required formula for my simulation on the attached sheet .

    What has confused me is that the mass of the rocket and the flight duration are the given parameters and the required water mass and air pressure are the required parameters?

    Attached Files:

  7. Oct 25, 2008 #6
    How did you go with the USQ Problem soving assignment Creme? Its a hell of an assignment...
  8. Oct 25, 2008 #7
    ...failing miserably in a group with no interest!!
  9. Oct 25, 2008 #8
    what group you in?
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