Experimenting with Model Rockets, part 3: Designing Rockets and the Scientific Method

With the practice of using clinometers behind them, we could begin to work on the rockets themselves. I had made one of the rockets in advance so that they could see the control on which their variations would be based. Their task was to create a rocket with one variation from the control rocket that would make it fly higher than the control rocket. We reviewed the scientific method.

The scientific method starts with observation. Observation allows the scientist to collect data. Once enough data has been collected, the scientist forms a hypothesis that attempts to explain some facet of the data or attempts to answer a question the scientist asks.

To assist the students in their data collection, I gave them a series of facts about model rockets.

• The lighter a rocket is, the higher it will go.
• If you increase the volume of a rocket, it will also increase altitude.
• Streamlining the body of the rocket will reduce drag.
• Smoothing the edges of the fins reduces drag.
• Less fins will result in less weight and therefore drag on the rocket.
• Fins that are larger than they need to be adds drag and weight to the rocket.
• An unstable rocket will not fly straight and will not fly as high. Fins add stability to a rocket.
• While elliptical shaped fins have the lowest drag for full-sized planes, for model rockets, a rectangular or parallelogram shaped fin seems to be the best shape to ensure lower overall drag.

I pointed out the number of fins, the way they were glued on and the length of the body tube are the variables that they needed to think about when thinking about making their rockets, reminding them that each rocket could differ from the control rocket in only one way.  We reviewed the fact that this is the only way to conduct a good experiment because if a rocket had more than one variable and it flew higher,  we wouldn't know which of the variables led to the rocket flying higher. They were assigned to design their rocket's variable as homework to bring to class next week for approval before the actual rocket construction began. They also needed to be able to say why they thought that the variable they chose would result in a higher altitude for their rocket. This would be their hypothesis.
With the remainder of class, we practiced using the clinometers on moving objects. We used a rubber ball and a Styrofoam ball and I posed the question: If thrown with the same force, which would go higher, a rubber ball or a Styrofoam ball? I had the students make predictions and then we went outside to conduct the experiment with the students using their clinometers to apply what they have been learning. 
I had drawn a circle on the playground with an 8 meter radius using an 8 meter length of string and a piece of chalk, using a string like a compass. 
I divided the class into two teams. Team A stood on one side of the circle and Team B stood on the other side of the circle. I stood in the middle of the circle and threw first the rubber and then the Styrofoam ball straight up as fast as I could. Students, using their clinometers, measured the angles and wrote them down. Next week we will use the measurements to analyze the results of the experiment. 

sources and resources:

• Experimenting with Model Rockets GEMS Teacher's Guide
• Exploring Creation with General Science