Big Freaking Water Rocket Launcher

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I am planning to turn a 15-liter water cooler bottle into an enormous water rocket using heavy-duty plastic made from pop bottles. This design has not been tested yet, so use it at your own risk. I won't be anywhere near the launcher when I add pressure, that's for sure. Just uploading this for comments and ideas. To-do list: * Develop a release mechanism (in progress). The base design has spots for O-rings and could work by simply letting go whenever the pressure is stronger than friction. I'd like to add arms that lock onto a ring on the bottle later, but first, I need to figure out if it will even work. Instructions Printing: The STL won't print as is; the two parts have to be separated. I didn't think the hose barb would print well even with support unless it was vertical. It still needs work for overhangs. Build Thoughts It probably needs to be printed with 30-60% infill and extra shells/perimeters, and I plan on using ABS rather than PLA for this one. An acetone vapor treatment or a brush with acetone slurry might be a good idea to make sure it's air-tight. The barb end is sized for 1/4" ID air hose, but may need to be separated; it's probably not going to print nicely that way. The rings on the riser should hold a set of O-rings. They don't all need to be filled - just the two or three that the cap of the bottle touches against. The style of bottle I am using (see pictures) is smaller than normal cooler bottles, and doesn't have a handle, so it should balance more easily. None the less, the legs of the launcher have holes to peg into the ground or screw onto a larger base. Potential issues: * The cap may completely pop off instead of launching from the smaller nozzle. Epoxy might help there. * I have no idea what kind of pressure these bottles can take. I plan on using just a little bit of water and building up gradually. * Balance and aim: the bottle will likely need some fins for stability and a nose cone for aerodynamics. * Need lots of space, probably bigger than a back yard. I don't want this thing hitting me or landing on anything I don't want damaged.