Transcript Bottle Rockets! - North Carolina Science Olympiad

Instructor Info
 Andrew Roberts
 [email protected]
 7 year participant in Science Olympiad
 Multi event medal winner at regional at state
tournaments
 Coached State Champions in Wright Stuff
 4 year SO Summer Camp Instructor
 Science Olympiad student intern
Process
 Read and understand the rules
 Research
 Design
 Build
 Test
 Analyze
 Fix
Important Rules
 Build up to 2 rockets before the tournament that
carry a grade A egg
 MUST WEAR SAFTRY GLASSES
 Nothing within 5 cm of the nozzle
 Can use any recovery system
Important Rules
 Rockets will use 2 liter soda bottles
 Launched at 75 psi
 Best single rocket time will win
 Will receive extra 15 seconds if egg doesn’t break
extra 3 seconds if egg detaches from pressure
chamber
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 Chamber
 2 Litter 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 ridged
 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:
 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
decent.
 The two most popular at the parachute and the backslider
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.
Example Backslider
Examples