Appropriate grades or age groups:
grade 5 and up

Estimated time to complete this project:
2-5 days

Materials:
Model rocket kit and launcher, with extra nose cones (hobby shop or buy online). Altitude tracking device (purchased, or made from things around the house)

What is the hypothesis of this science project? What does the experiment aim to prove?
Which shape nose cone gets the rocket the highest altitude?

Instructions:
We bought a tiny Estes model rocket kit, (the "Swift) the kind that takes their small 1/2A size motors, for 4 bucks. We also bought a variety bag of spare nosecones that fit the model's tube size. Five bucks. We used three different nosecones for the same rocket: one was simply sanded to a blunt flat shape and we added clay to make it weigh the same as all the others. We used an ogive (bullet nose) shaped cone, and a pointy, spiky shaped cone. It's important the nose cones all weigh the same, so as not to bias the experiment: you want shape to be the only variable.

We launched the rocket three times in the same hour, with the launcher unchanged. Altitude was measured with a 20-dollar gadget called the Estes Altitrack, but you can make your own tool for free from things in the house if you need to save money. The simplest altitude measurer is a protractor glued to a stick, with a plumb bob string hanging down as an indicator. Stand about 200 feet away from the rocket at launch (use the identical spot for each launch observation), and measure the angle when the ejection charge puffs out white smoke at rocket's highest point (apogee) Higher angle = higher altitude.

If your kid is in 9th grade or junior high, you can take this experiment to another level, and use math to give more precise altitude readings: If you know the baseline distance to the launcher, You launched with the launch rod straight up at 90 degrees, and you know the angle you got with the protractor device, you can use the rules of a right triangle to calculate the height with precision. That's what the Estes Altitrack device does automatically: it has a calibrated scale on the side that does the math conversion for you, but a judge will respect your kid more if she did the math herself. Makes a good practical math demo of geometry/trig in use.

Other comments or suggestions:
Building the rocket with the kid was as fun as firing it and running the experiment. These rockets are small and can go high: paint them a day-glo color that's easy to track and find in the grass, or risk losing them. Use the weakest motors available, to keep from losing the rocket from wind drift. The one we used, ("Swift") on 1/2A mini size motors, got to about 200 feet on the best try.

As to the nose cones, what "looks" efficient isn't always what IS most efficient.
Don't glue the noses on: either use tape or drill a little hole thru the side and make a retaining pin with a paper clip wire or push pin, so you can swap out nosecones between flights.

If you're not versed in model rockets, ask the folks at a real hobby shop to help you out with this experiment and getting all the right materials. It really isn't hard or expensive. A fancy premade launcher is about 20 bucks, or you can make your own with 30 feet of 2-wire lamp cord, some paper clips, and a 12-volt battery like the one in your car, or 2 6-volt flashlight lantern batteries hooked in series. The rocket engines come in packs of 4 with their own electric igniters and instructions, the only other thing a launcher needs is a length of stiff piano wire (craft or harware store) stuck in the ground to guide the rocket for the first 2-3 feet. So you could do all this for about 25-30 bucks if you're thrifty, 50 bucks "first class". Plenty of resources and tips via google and the NAR (National Association of Rocketry)

*This also makes a good group or class project.