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3, 2, 1, Blast Off!. Process. Read and understand the rules Research Design Build Test Analyze Fix. Important Rules. Build up to 2 rockets before the tournament Rockets will use 2 liter carbonated bottles MUST WEAR SAFETY GLASSES Nothing within 5 cm of the nozzle
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Process • Read and understand the rules • Research • Design • Build • Test • Analyze • Fix
Important Rules • Build up to 2 rockets before the tournament • Rockets will use 2 liter carbonated bottles • MUST WEAR SAFETY GLASSES • Nothing within 5 cm of the nozzle • Launched at 75 psi • Can use any recovery system • Best single rocket time will win
What makes it work? • Water is poured into the pressure chamber • Air is then pumped into the bottle. • When the rocket is released, the air forces the water out of the bottle. • Newton’s Third Law of Motion kicks in
Pressure Chamber • 2 Liter soda bottle • Do not cut or scratch the pressure chamber. • Can glue fins to pressure chamber with silicone or polyurethane glues. • If pressure chamber is damaged it will not be launched
Fins • Fins keep the rocket stable in flight • There must be at least 3 • Fins must be rigid • Backswept fins work best
What does it mean to be stable? • Stability: the tendency of the rocket to return to equilibrium • This means if the rocket begins to veer, it will straighten back up on its own. • To be stable, the center of mass must be closer to the top of the rocket than the center of pressure
Nose Cones • Popular types: • Conical • Blunted Conical • Elliptical • Spherical • Nose cones reduce drag • Conical are easy to make but can be difficult to get straight.
Recovery Systems • A recovery system is something that slows the rockets descent. • The two most popular at the parachute and the back-slider
Recovery Systems • The velocity of a falling object can be shown as follows where v(t) is velocity, g is acceleration do to gravity, c is the coefficient of air resistance, t is time, and v(0) is initial velocity. • C is much larger for a parachute than a backslider; therefore, it will fall much more slowly
Parachute • Parachutes work best but are harder to get to work consistently • The size needs to match the rocket. • It should have 8 to 10 strings • Fold it like an accordion and then wrap extra string around it to keep it folded
Making a Parachute Cut Here
Backslider • Backslider is made by making the center of gravity close to the center of pressure • This prevents the rocket from turning over at apogee and instead floating down on its side. • Fins on this type of rocket should be larger to help slow it down.