Description: This is a build ahead of time event. Teams will design, construct, and launch two 2-liter water rockets to stay aloft for the greatest amount of time. Each rocket must have 3 fins.
*** MAJOR ISSUE: Some soda manufacturers have changed the size of the neck of their bottles. Please make sure the inner diameter of your bottle neck is still 2.2 cm, not the new reduced size of 2.1 cm. The 2.1 cm necks will not fit on the launcher. The easiest way to test this is by sliding a piece of 1/2 inch PVC into the bottle. If it fits loosely, the bottle will go on the launcher. If the PVC sticks and you have to apply any force to slide the PVC in, the bottle will not go on the launcher.***
Teams MUST bring safety glasses and their rocket(s). If bottle labels have been removed, teams must also bring those. Teams may also bring a funnel and measuring cup for the water.
Event leaders will provide water, the official score sheet, and testing equipment.
High score wins. Score will be determined by adding the time aloft of the 2 rockets in seconds.
- The number one mistake made by teams is not using a CARBONATED bottle for the pressure vessel. Carbonated bottles are required because they are pressure tested by the manufacturer against defects. Non-carbonated bottles are NOT tested, and are NOT allowed, even if they come in a 2 liter size. Other parts of the rocket such as nosecones and fins may be made from non-carbonated bottles, but the pressure vessel MUST be carbonated. This is a serious safety issue, and rockets that violate this requirement will not be allowed to launch at all. It is a safety disqualification that will NOT be arbitrated.
- Be sure that the pressure bottle remains intact. Repeated testing and hard landings can damage your pressure bottle. Check it frequently for scratches and weak spots that may compromise the structural integrity, and replace the bottle as needed.
- Find the ideal water level for your rocket. While 100% air will give you the maximum potential energy, it has very little mass and therefore very little momentum to carry the rocket. Likewise, 100% water will have great mass, but very little potential energy to give it momentum. Don't wait til the day of the competition to decide how much water to use!
- If you remove the label from your pressure bottle, be sure to bring it to the competition or you will not be allowed to launch the rocket.
Remember, only one launch is allowed per rocket! If you want to utilize both launch attempts, you must bring a second rocket! Varsity and JV teams must each have their own rockets and may not borrow each other's rockets to launch.
- This event only requires safety glasses, meaning the kind that look like sunglasses will work just fine. These are MUCH easier to see out of. Your local home improvement store carries cheap versions for under $4. Safety goggles (the chemical splash kind that most schools have) have a tendency to fog up, making it hard to see.
- For transporting rockets with less risk of damage, glue/screw a bottle cap to a cardboard or wood base and simply screw your rocket onto it to make it stand up. For added protection, place this entire setup inside a 5 gallon bucket to protect fins, etc.
- If you are concerned about the integrity of a bottle that you have found to use for your pressure vessel (It looks unaltered but you're just not sure) you can pressure test it. To do this, fill the bottle completely with water. This ensures that the amount of air (and potential energy) inside is minimal, so that if the bottle does fail it should simply rupture and not explode. Then pressurize it to 1 1/2 times the competition psi (competition requires 60 psi, so test to 90 psi). While this is not a way to bypass safety regulations, it can give you peace of mind and save you a lot of build time by preventing building on a damaged bottle.
- Rather than trying to cut holes through your rocket's non-pressurized plastic components, use a hot needle or hot ice pick to poke a hole with smooth, rounded edges.
- The driving force behind a rocket launch is the combination of air and water under pressure. The air that you pump into the bottle compresses, giving you a higher pressure (60 psi in this year's rules). When the rocket is released the air expands rapidly, which forces the water out of the neck of the bottle and propels the rocket.
- Angling your fins slightly to one side will cause the rocket to spiral on its way up, creating stability much like throwing a football in a spiral.
2014 Coaches Institute Handout (2015 Rules)
2012 Coaches Institute Presentation (2013 rules)
2010 Coaches Institute Presentation (2011 rules)
See the event help page for the Middle and High School version of this event (with more pictures)
Nerds, Inc (excellent rocket launchers like the ones used at NCSO tournaments)
NASA Water Rockets
- general info, not specific to NCSO event rules
Wiki How - Step by step videos on how to build a bottle rocket - not specific to NCSO event rules
Tim Hesterberg's How to Make a Water Bottle Rocket Page - not specific to NCSO event rules
Pictures and Video: