2. CeAnn Chalker ceann@chalker.org Bro. Nigel bronigel@kellenberg.org

5. * 1 st, let’s check out some extreme rocket scientists (this website is probably the best out there for ideas/hints for rocketry. They take it to a level WAY beyond SO, but they know what they are talking about.)extreme rocket scientists * Now more on our level: BacksliderBackslider * Search for “backslider,” “backglider,” and “water rockets” as opposed to “bottle rockets” * Remove the labels (and keep them – know which label goes with what rocket). Clean off the ALL the glue, but don’t scratch the rocket. * Build CLEANLY! The smoother the sides of the rocket, the better.

6. * ALWAYS keep in mind: Keep mass at a minimum!!! F=ma * Get a variety of CARBONATED 2 l bottles from DIFFERENT companies. You’ll be surprised at the variation of masses. * Use non-carbonated bottle parts for your extension, nose cones, egg holder, etc. (tend to be thinner and lighter) * Trim away ANY excess parts that are buried in the rocket and will not affect it in any way. * Use as little tape/glue as you can – both for mass and aerodynamic clean builds * Use 3 vertical fins (suggestion: thin styrene sheets)styrene * They do not have to be large!!! * Remember the 5 cm “No Fin Zone!” * Cut out a piece of non-carb bottle rocket that matches the curve of your pressure chamber. Glue the fin to the piece and then tape it to the pressure chamber!

7. * The Egg… * What material for the holder? – bubble wrap, plastic egg suspended, foam with egg cutout, air cushions, balloons, etc… * Location? * “….must be easily removed” * Practice with plastic eggs (with masses to get them to total between 57 – 60 g) to get the correct stability of the rocket. * When you transition to real eggs, use zip lock bags to facilitate clean up for the ones that fail. * Total length – depends on mass and stability (last slide) * Ones without an egg work well at an extension length of 80 to 120 cm beyond the pressure chamberextension * Cone should be rounded (NOT pointy) – plastic egg, ping pong ball, etc.

8. * Rocket Stability is VITAL! * There are three measurements that enter into the stability of the rocket - Center of Pressure (CP), Center of Gravity (CG), and Center of Lateral Area. Some of the suggested websites go into lots of detail about this. The kids building the rockets should at least read this information to help in the construction of their rocket. * At the very least, determine the CG by balancing the rocket on a pole, dowel or pencil. * Do the “2D” test to determine CP. (next slide!) * It is extremely important that the CP be closer to the tail than the CG. If they are reversed or in the same place, then the rocket will be unstable in flight * It is recommend that the CG should be at least 1 rocket diameter higher than the CP!! * Ways to change CG and CP positions: size of fins, location of masses (Putty could be added to the inside of the nose cone, etc.)

9. * CP determination: For a model rocket, there is a simple mechanical way to determine the approximate CP for the rocket. Make a two dimensional tracing of the shape of the entire rocket on a piece of cardboard and cut out the shape. Then again using a pole determine where it balances. The point at which the rocket is balanced is approximately the center of pressure. THE END.

11. * Good Websites (hint: type “water rocket” not “bottle rocket”) * http://www.h2orocket.com/ http://www.h2orocket.com/ * http://www.waterrocketmanual.com/index.htm http://www.waterrocketmanual.com/index.htm * http://polyplex.org/rockets/simulation/ http://polyplex.org/rockets/simulation/ * http://polyplex.org/rockets/ http://polyplex.org/rockets/ * http://txsnapper.eezway.org/waterrocketguy/backslider.html http://txsnapper.eezway.org/waterrocketguy/backslider.html * http://www.aircommandrockets.com/ (Cool videos of extreme bottle rockets) http://www.aircommandrockets.com/ * And many others!! * Good Luck…and Happy Launching!