Sunday, December 24, 2017

High-Power Rocket Initial Design

It has been a wild year since my last post. Crashed my old Fit, bought a brand new 2017 Prius, took my place as a junior engineer a lot more in my company, passed my OIQ ethics exam, tried to buy a house (and chickened out), finished a bunch of small projects that I won't really be talking about because I didn't document them, got more into the cosplay community...and left because I just stopped doing stuff.

Long story short, I want to get back into something I started getting into with the GAUL in University; High Power Rocketry.

So for the actual initial design:

Design Constraints:

  1. - Use Pro-38 casing (Because they're way WAY cheaper than Pro-54)
  2. - Can accomodate H to J impulse motor to be used as a reliable certification rocket from level 1 to 3
  3. - Gets as close as possible to 6000 ft with the biggest pro-38 J motor
  4. - Dual deployment
  5. - Use a stratologger for the altimeter.
  6. - Must NOT include crazy custom avionics, sensors, or other similar. (Although I do have some ideas for some for a future rocket from my time with the GAUL...)
  7. - Custom Avionics bay. None of this plywood and threaded rod bull crap.
  8. - Must not be 2 inches or less. Fisting a rocket is hard enough, no need to make it harder.

And all the USUAL design constraints of building a rocket:

      - Must survive launch, MAX-Q, Aerolastic effects, and touch down.
      - Minimum 4g of acceleration at lift-off to clear the rail with a speed high enough to be stable
      - Must be Stable with any pro-38 motors, from H to J.

Based on #3, you don't want to go too big in diameter. More Diameter = More surface area = more drag = less altitude. But then considering #8, there are only two real choices as far as rocket diameter go. 2.6 inches and 3 inches. Based on that, #1, #2 and #4 we can start messing around on OpenRocket.

Messing around, I ended up with two possible designs. One with a 2.6inch diameter, and one with a 3inch diameter. All tubes and nose cone measurements are based on phenolic tubes.

Comparison of both preliminary design with a 819-J354-WH-16A-13

As you can see, the 2.6inch gets closer to 6000 feet with the biggest J Motor, gets so close...and yet so far, to being supersonic  (Mach 0.97 with a V-max), which sounds more fun, and looks WAY better.

The 3 inch version would be a lot less pain to fist, designing the avionics bay would be way easier, but the rocket would also be a lot slower (Mach 0.89 with a V-max), would go 300 feet lower, and look more boring overall.

And so in the end, I will be going ahead with the 2.6 inch initial design.

And that's it for today! My next post will either be me talking about the initial design of the avionics bay, or dismantling something.

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