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Project and Construction of Arduino controlled model rocket

  1. Apr 20, 2016 #1
    Hey folks. I've done a little bit of research into model rocketry and I'm stuck with the idea of designing and projecting a rocket to put into practice all the engineering I'm learning in college - I'm into MechE. I want to start simple, doing a few tests and learning the basics - types of engines, propellants- and, after that, build something a little bit more sophisticated. I'm learning Arduino, and I want to implement things like control, guidance and data collection - acceleration, temperature, pressure - into my project.
    So, where should I start? I don't want to buy a ready design, I want to build my own. I know there are sugar rockets, but I don't know if this would be the best option for the project that I bear in mind. What about materials? The interior of the rocket, that comes into direct contact with the burning propellants, what should it be made of?

    My intent is to build an engineering project. So I want to understand the thermodynamics, do all the calculations - rocket equations and so - and theoretical stuff, in order to compare with experimental data.
    Any hints of how should I start to delve into this?
     
  2. jcsd
  3. Apr 20, 2016 #2

    berkeman

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    Staff: Mentor

    What is your background in model rocketry? Is there a club near you where you can learn more (especially about safety)?

    You did see the recent news articles about the high school student who was killed when the model rocket he was working on exploded, right?

    http://ktla.com/2016/04/04/2-injure...-explodes-at-thousand-oaks-elementary-school/

    The more you try to do on your own instead of using proven kits, the more likely an accident is to happen. I'd recommend starting with a small 4-wheel vehicle similar to an RC car, and adding your own guidance system and Arduino control to that first. That will let you start to get the hang of inertial guidance, without the dangers associated with rocketry...
     
  4. Apr 20, 2016 #3
    Didn't knew about that. Thank you. Sadly, there's no club nearby where I could learn more, but I don't intend to do anything very dangerous. Would it still be dangerous if I'm dealing with proven kits? Could I customize those kits to implement my guidance, control systems?
    And yeah, I do intend to start with 4-wheel vehicles and try to build some simple robots. But I want to deal with rocketry somewhere in the future, and I wanted to know a little bit more about how should I start dealing with this project.

    EDIT: I've been making my research in this site: http://www.nakka-rocketry.net/
    There is a ton of stuff related to model rocket building in there, including safety procedures. I'm not a risk-taker, so I don't intend do start with the hard - and more dangerous - stuff.
     
    Last edited: Apr 20, 2016
  5. Apr 21, 2016 #4

    berkeman

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    Staff: Mentor

    Thank you for your good reply -- we feel a lot better about what you are doing now.:smile:
    Yeah, I haven't seen if they've found out what they did wrong to get killed/badly injured. They sound like very bright young high school students, so the accident is very problematic.
    I think that's the best approach. Start with standard solid fuel rocket bodies, and look at replacing the purely drag control fins with top and bottom control fins driven by the Arduino. And starting with ground vehicle control is a good springboard to the full vertical problem, IMO. :smile:
     
  6. Apr 21, 2016 #5
    Also, I have the intention of studying things like thrust, specific impulse and thrust-to-weight ratio. Surely, proven kits will come with this information, but I do want to test them for myself, build thrust curves and understand the basic operation of the rocket. There is some information about this in the website I posted. I found it really interesting:
    http://www.nakka-rocketry.net/strainlc.html (a strain gage load cell for thrust measurement)
    http://www.nakka-rocketry.net/hydlc.html (there is a hydraulic version)


    EDIT: I think that the most dangerous stuff in building model rockets is the engine. After I start playing with a few proven kits - and understand all the basics - would it be a good idea to buy just the engines and integrate them into a home-built rocket? This would skip the hazardous procedure of mixing up chemicals, and I could focus on designing the body of the rocket, aerodynamics and control systems.
     
    Last edited: Apr 21, 2016
  7. Apr 21, 2016 #6
    Okay, a little bit of math here.
    I looked at some of the equations on rocketry, and tried to obtain, theoretically, what speeds I could get given some conditions. I thought about a 0,400kg rocket - full - with average thrust of 40 N. I used the formula:

    [tex]I_{sp} = \frac{T}{ṁ g_0}[/tex]
    Where Isp is specific impulse, T is average thrust, ṁ is mass flow rate and g0 is gravity acceleration. I got the information on the rocket specs by looking at some rocket kits charts. The mass of the fuel is 0.0581kg, and burn time = 1.3 sec. So I get that ṁ = 0,0446kg/sec, and I plug that into the equation to find that Isp = 91,157sec. I'm assuming that all the fuel is burnt in 1.3 sec, so the final mass of the rocket would be 0,3419kg.
    I used Tsiolkovsky rocket equation to find delta-V:
    [tex]\Delta V = I_{sp}g_0*\ln{\frac{m_0}{m_f}} - (g_0*tb)[/tex]
    Where the term "(g_0*tb)" is a correction for the gravity acceleration - tb is burn time. I've found that delta V must be equal to 127,684m/s.
    By using Newton Laws, I've got a similar result for the final speed. First, I've found that resultant force during take off would be equal to 36,072 N, and assumed that this would be constant during burnt. Also I assumed that mass changes linearly with time - another simplification. I integrated this with time and found that final speed would be equal to 126,625m/s.

    Thing is: I may be making a total mess here. I'm learning all those concepts - specific impulse, thrust - and I may be confusing some stuff. I'm not sure if delta-V in Tsiolkovsky equation means what I think it means. I'm I doing this right, or the similarity between the results I've got is just a huge coincidence?
     
  8. Apr 21, 2016 #7
    And the escape velocity from Earth is what?

    Where the heck are you sending that thing!?
     
  9. Apr 22, 2016 #8
    Sorry, I'm not sure if I understand your question.
     
  10. Apr 22, 2016 #9
    European notation 1/2 -- 0,5000 --- American notation 1/2 == 0.500
    V-final 126,625 m/s in American notation 126.625 m/s
    Earth escape velocity about 12000 m/s -- 126625 m/s over 10 times that
    light speed 300000 m/s
     
  11. Apr 22, 2016 #10
    To put something in orbit you need 8km/sec. To escape the solar system, around 30km/sec.
    You are showing speed of 126km/sec. Where are you going/how long will the trip take?

    @vinicius0197, garcol popped in as this was being written. If you are is using European notation, that answers both your and my questions.

    Greetings from Southern California!
     
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