• An investigation is really a series of
experiments all trying to solve different
pieces of the same problem.
• Your task is to determine what it takes to
propel a pop bottle rocket to its
maximum distance.
• Your research.
– What do you already know?
– What have others who are working similar problems found out
that might help you with your problem
• Examples of background info might include:
– What components do rockets have that you could or should
– include in your rocket design? What size and shape should
these components be?
– How should the weight be distributed?
– What creates the thrust to launch a rocket?
All information in this presentation is taken from
http://www.geocities.com/rocketcorps/index.html
The main part of the rocket will be
A 2 liter bottle.
Don’t cut or puncture the pressure chamber (bottle)
Don’t use: hot/boiling water
knives or razor blades
chemical solvents
FLOUNDER NOSE CONE
The first type illustrated here is called "The Flounder".
It is the easiest to make but lacks flight stability. The
cone is made from poster board or tag board. You
can make the cone by simply cutting a large circle out
of the poster board (about a 6 inch radius). Cut a line
from the outer edge of the circle to the center on the
radius. Overlap the cut edges and turn the circle while
holding one edge stationary until you get the desired
cone shape. Secure the cone with staples or tape.
Attach to the bottle with tape or similar adhesive.
As I mentioned before "The Flounder" lacks flight stability,
this can be fixed to a degree by pressing a small lump
( a few ounces) of clay to the inside of the nose cone.
This will add mass to the cone and keep your rocket
from flipping end over end while in flight. This new
and improved rocket could be called "The Bullet".
You can also put a golf ball or tennis ball in the nose cone
for top weight.
“Bertha” Nose Cone
The "Bertha Series" nose cones are easy to make
as well but require a little attention to detail. The
"Bertha" nose cones are made by cutting the bottom
off a spare bottle and attaching the top portion
onto the pressure chamber. One strip of tape should
be enough to hold the cone on. (Note: Never
cut the pressure chamber) Using this method
you can even make your "Bertha" rocket two or
three nose cones tall! (we call that a "Big Bertha")
Within the top nose cone you can add a small lump
of clay to increase the mass. Pay attention to keep
all the cones in a straight line. A curvy rocket will
not be safe coming off the launcher.
“Space Needle” Nose Cone
The "Space Needle" style of nose cone can be made
from a spare bottle, empty paper towel roll, and
a tennis ball or racket ball. This type of nose cone
adds a great deal of inertial mass to the rocket and
makes it really stable. Simply, attach the towel roll
to the top of a single Bertha nose cone and then fix
the tennis ball to the top of the roll. Take your time
building this set up because you want the entire
assembly to be straight as an arrow.
Cut tabs in an index card and glue or tape
the card to the tube. This will hold the tube
upright. Then glue or tape the tabs onto the
nose cone top.
Additional Ideas:
A used foam pool noodle will make a fantastic
soft, spongy nose cone. Use a serrated knife to
shape the foam noodle and hot glue it onto your
nose cone.
Plastic egg halves will also fit nicely onto the
"Space Needle" assembly.
FINS
Fins are the guidance system for your rocket. Without them
a rocket would tumble end over end. Fins can give your rocket
life and beauty. Fins can portray aggressive power or aerodynamic
grace. However, fins tend to be the single greatest downfall of
many young rocket builders. With the incredible speeds and
frightful acceleration generated at launch, many fins get ripped
off the rocket body within a fraction of a second. I will discuss
the reasons for this later, but for now let's list some common
building materials
Materials: (remember lightweight but sturdy)
Index cards
Clear packing tape, or duct tape
Cardboard (cheap, plentiful, soggy when wet)
Chipboard (cereal boxes)
Foam core (a little tougher but more $, some water damage)
Sturdy-board (like plastic cardboard, great stuff, $$, no water damage)
Balsa wood (might be a little heavy, fragile on impact)
How many fins do I need?
To ensure stability and safety, the minimum number of
fins on a rocket is three (3). Many people choose a 3 or 4 fin
design. There is no maximum number of fins you may have
but keep in mind that the more fins you have the more drag
you will create and drag slows a rocket down.
Constructing fins
1. Be creative and cut out 3 or 4 identical fins.
You can use any shape except "forward swept"
fins.
2. Lay the fin on a flat surface.
3. Glue and/or tape an index card onto the side
of the fin. Be sure to leave a one-inch tab on the
index card.
You will later bend this tab out 90 degrees to
make an attachable area for the rocket.
4. Repeat the same for the other side of the fin.
5. Repeat with other fins.
You should now have 3 or 4 fins each with two-index card tabs on the
backside. (I like to laminate the entire fin surface with clear packing
tape to reduce the amount of water damage to my cardboard fins.)
Fin placement
The fins of your rocket can't be placed above the halfway
point of your pressure cylinder. You want to place your fins
at the base of the rocket to lower or maintain the center of
gravity. If you were to place the fins above the center of
gravity, the rocket would tumble and spin out of control
once it left the launch pad.
Attaching the fins
1. Apply a piece of tape to the index card tabs and
them carefully tape them to your rocket.
2. Look at your fin. Make sure it doesn't curve
or it isn't crooked. It should be in a direct line with the
body of your rocket. If it isn't perfect, take it off
and try again.
3. Attach the other fins. If you are using 4 fins
they should be at 90-degree angles. 3 fins should
be at 120-degree angles.
4. Test the wiggle of the fins. Your fins
shouldn't wiggle more than a few centimeters
from side to side. Adding more tape to the top
and bottom areas of the fin might fix this problem.
Your group needs to write one lab report, so find
someone who will be a good scribe. I suggest that you
keep the report in the “In box” so if the scribe is absent,
the group can continue and have someone else write.
Make sure that the name of everyone in your group is
on the report. You will be graded by the quality of the
report, so make sure everyone in the group is happy with
the report.
The report should have the following information:
The purpose for this investigation is to construct a water
bottle rocket that will travel the farthest distance down the
football field.
Independent variable is the one thing you are testing
In your experiment, remember to test only ONE new
thing at a time! Testing more than one variable at a
time makes it so you can’t tell if the outcome is because
of one, the other, or both changed variables.
Dependent variable is the data measured as a result of
testing the independent variable. In this case it will be
the distance traveled down the football field.
Controlled variables: Everything that you are keeping the
same and not changing. Write down what you are keeping
the same such as: same pressure (all launches will be at
60 psi) same launch angle, same fins or same nosecone,
or same amount of water, etc.
Write down what you are using (aluminum foil,
cardboard, tape, clay, posterboard, etc.) and how you’re
using all the stuff. Drawing pictures and labeling them
is a really great idea.
Then go test your ideas.
How did it go? What distance did it go? (make sure
you include units of feet, meters, yards, etc). Write
down everything that happened and what you
observed, such as:
how did it fly (straight, crooked, etc), did parts fall off,
how did it come down, how did it land, etc.
You will also need to include the following calculations:
1) Solve for height: 4.9((ave. time)/2))2
2) Solve for initial velocity: V0 =(∆x/(∆t cos 45º))
This investigation is a series of loops. Using what you learned
on your first attempt, “tweak” it (make adjustments) and test it
again, or try something entirely different, but only change one
variable at a time. If you change the nosecone, keep the same
fins water amount, and body style etc. If you decide to “tweak”
or change the fins, then keep the nosecone, body style and water
amounts the same, etc.
Tell what you are doing to improve or change the independent
variable, and what you are keeping the same as before. Be specific.
Based on your launches, tell how the factor (or factors)
you were testing affected the flight of the rocket, and what
design you found to work the best.