ProcessRead and understand the rulesResearchDesignBuildTestAnalyzeFix

Important RulesBuild up to 2 rockets before the tournamentRockets will use 2 liter carbonated bottlesMUST WEAR SAFETY GLASSESNothing within 5 cm of the nozzleLaunched at 75 psiCan use any recovery systemBest single rocket time will win

What makes it work?1. Water is poured into the pressure chamber

2. Air is then pumped into the bottle.

3. When the rocket is released, the air forces the water out of the bottle.

4. Newton’s Third Law of Motion kicks in

Parts of the Rocket and Forces

Pressure Chamber2 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

FinsFins 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 ConesPopular types:

ConicalBlunted ConicalEllipticalSpherical

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 SystemsThe 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

ParachuteParachutes 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

BacksliderBackslider 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.

Example Backslider

Examples