I am a student of mechanical engineering and my next project will be a hybrid power rocket. This is outside of the curriculum so i cannot really expect any help from the university more than locales to work in.
This will be a rocket from scratch, i'm thinking of a very simple design to start with, two paintball co2 tubes joined, with some kind of regulating valve in between. The oxidator will most likely be NO2. The choice of fuel has not been decided, but expect something simple.
So, lets get to the fun parts, how to make it. A couple of questions right from the top of my head:
1) When you buy the over the counter pressure containers designed for paintball use, i suppose you want to change the valve. To what type of valve? Is it a straightforward operation just unscrewing the things, or are there measurments to prevent you from doing that? What kind precautions must one take when assembling the new valve with the tank. Supposedly that tank has to hold 300 bars of pressure, so you dont want anything but a rock solid fit. Are the measurments standard, are there a specific brand of valves or tanks preferred?
2) Nozzle manufacturing. How do you know what type of nozzle to use, is it simply a figure it out as you go along type of deal? Should the back end of the combustion chamber tube be threaded for greater resistance to failure due to overpreasurization? Finally, material, what kind of material, and where can i get a hold of it, say a 5 times 5 cm piece of graphite?
3) How straight can you expect your rocket to travel? I can imagine that if you get the slightest missalignment when lathing the nozzle, you screw up the trajectory of the rocket big time. Any tips on how to make the flight as straight as possible?
4) Fuel, what type is recommended. I read somewhere that you can use plastics, like polyethylene, and alltough you can cast that relatively easy, i cant imagine it being near that easy to light it with a match, or whatever ignition technique you prefer. You have to cover it with some type of easy ignitable solution in order for it to catch, so that you will get some kind of combustion.
5) In order not to reinvent the wheel, and save a buck or two, i'd like to for our first project at least, to be inspired by a previous design. Is there a suitable project thread on this or on a similiar kind of internet forum that you could refer me to?