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 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

Parts of the Rocket and Forces

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

Fin Shapes

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: Nose cones reduce drag 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

Making a Parachute

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. Acceleration down = (m*g – v*b)/m

Example Backslider

Examples