Why the story? We’re thinking about 3D printing a nozzle. As it is screwed into the 2-liter bottle threads and below said threads, it will contain some extra volume (fuel). How much extra volume can a nozzle contain before it is creative cheating?
Let’s take several cases that are related.
1) The rules can’t be ABSOLUTELY ZERO or even the off-the-shelf Gardena quick-disconnect with its extra few milliliters would be unacceptable.
2) The rules can’t be wide-open as someone might create a half-liter chamber that they tout simply “smooths” the flow. While the rest of us say, “clearly that’s a honk’n 2 inch fuel line!”
3) As a reality check and similar issue... the standard launch system using a ½ inch PVC pipe up the center of the 2-liter bottle that is used as the air supply and a launch guide tube has a variable volume depending on where the air shutoff value is located. (A) If the valve is right next to the rocket, the air pressure inside the rocket is dropping as the rocket slides up the tube. However (B) if the tube bore is large and the volume large between the rocket and the valve, the pressure remains nearly constant until the rocket clears the tube. Yes, this is a small advantage, but someone might argue an unfair advantage.
We’re not looking to bend or break the rules. However, we really don’t even want the perception of bending the rules. As this will be performed as part of an 8th grade science class, it would be quite embarrassing to subsequently be labeled a cheat and disqualified... Not quite the example we want to present to the students.
Thanks
