We just launched our rocket named Orion III at 3rd March 2017. It consist of two 1.5 litre bottle, one is used for pressure chamber and the other one is used for electronics bay and deployment bay. We are using Estes altimeter to record our rocket's peak altitude. More information about estes altimeterhttp://www.estesrockets.com/002246-estesr-altimeter. The weight of our rocket is 274 grams and the average altitude for three flights is 85.67 meters(281.07 ft) 83+86+88/3 = 85.67 meters
I come from China, do not understand English, your information I use the translation software to view. I like water rockets, technology is the same, I hope we can become friends.
That is an interesting bottle shape. I bet you have trouble joining those together because there does not look like a single straight part on the side of the bottle. It look like a good aerodynamic shape by itself, so perfect for a single bottle rocket. I congratulate you on the submitted record! I approved!
Mark Chen wrote:That is an interesting bottle shape. I bet you have trouble joining those together because there does not look like a single straight part on the side of the bottle. It look like a good aerodynamic shape by itself, so perfect for a single bottle rocket. I congratulate you on the submitted record! I approved!
yup, im quite happy too about the shape of the bottle, it helps reduce the drag. Actually the bottle is'nt bend but the launcher tube bend a little bit to the left because we only us PVC pipe as the launcher tube so it will bend by time due to usage of the launcher. This launcher is 3 years old . Thank you soo much for voting and have a nice day
Fantastic job. I just did an analysis of your rocket. The Asian Pepsi bottle you used looks very similar to a 1.5L Calpico (or Calpis) soda bottle one can get at Japanese grocery stores here in the United States: taller than the squat 2-liter bottles we have here, and significantly thinner, about 92mm in diameter. The best thing is the shape, with a long taper toward the nozzle end. This has a significant effect on drag coefficient. And I find that the altitude achieved is very sensitive to drag coefficient.
So I plugged the dimensions of a Calpis bottle into the simulator I wrote, set it at 274 grams for the empty weight and 0.5 liters of water. I had to guess at the length of your launch tube. I calculated that the water level would be 134 mm above the nozzle, and it looks like your launch tube goes about 25 mm higher than that. So I'm assuming your launch tube is 160 mm.
My simulator indicates that to achieve 85 meters, your rocket's drag coefficient is about 0.19. This is amazing considering that a typical bottle rocket has a drag coefficient approaching 0.3. And your initial fill of 0.5 L is spot-on, the optimum fill for a 274g rocket. Hitting the optimal fill like that makes me think you did some analysis of your own.
A 2 liter bottle has the advantage of containing more energy (more air volume for 100 psi), but the sub-optimal shape with a poor drag coefficient negates that advantage. The thinner bottles perform better as long as you can keep the rocket light enough.
That's an elegant-looking launcher you constructed, also.
anachronist wrote:Fantastic job. I just did an analysis of your rocket. The Asian Pepsi bottle you used looks very similar to a 1.5L Calpico (or Calpis) soda bottle one can get at Japanese grocery stores here in the United States: taller than the squat 2-liter bottles we have here, and significantly thinner, about 92mm in diameter. The best thing is the shape, with a long taper toward the nozzle end. This has a significant effect on drag coefficient. And I find that the altitude achieved is very sensitive to drag coefficient.
So I plugged the dimensions of a Calpis bottle into the simulator I wrote, set it at 274 grams for the empty weight and 0.5 liters of water. I had to guess at the length of your launch tube. I calculated that the water level would be 134 mm above the nozzle, and it looks like your launch tube goes about 25 mm higher than that. So I'm assuming your launch tube is 160 mm.
My simulator indicates that to achieve 85 meters, your rocket's drag coefficient is about 0.19. This is amazing considering that a typical bottle rocket has a drag coefficient approaching 0.3. And your initial fill of 0.5 L is spot-on, the optimum fill for a 274g rocket. Hitting the optimal fill like that makes me think you did some analysis of your own.
A 2 liter bottle has the advantage of containing more energy (more air volume for 100 psi), but the sub-optimal shape with a poor drag coefficient negates that advantage. The thinner bottles perform better as long as you can keep the rocket light enough.
That's an elegant-looking launcher you constructed, also.
How did you make the fins? Were they 3-D printed?
Perfect research xD... actually the diameter of the bottle is 80mm +-2mm, and our drag coefficient is 0.295 which is a bullet drag coefficient. our fins is made from straw board which is the lightest and durable material we have found so far. the fins only weights 3grams for 3 fins.
bshot89 wrote:Perfect research xD... actually the diameter of the bottle is 80mm +-2mm, and our drag coefficient is 0.295 which is a bullet drag coefficient. our fins is made from straw board which is the lightest and durable material we have found so far. the fins only weights 3grams for 3 fins.
80mm is the widest diameter of the bottle? I can imagine that 80mm would be the diameter of that narrow cylinder section, but isn't the bulge before the nozzle somewhat larger?
A bullet has a drag coefficient of 0.295 because of the blunt tail end, causing it to lose kinetic energy because the tail end is transferring energy to the air to create vortices. This has a huge effect on drag. The tail actually contributes more to drag than the nose. Your tail end has a nice taper to recover the energy that a bullet would lose, so I'm confident that your actual drag coefficient is less than a bullet.
I'm also curious about your recovery system. Servo? Mechanical timer?
WRA2 members only. Submit your videos and altimeter data to qualify for the WRA2 Unreinforced Bottle world record.
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