Cardboard Rockets

This is a project I do every year with my physics students. The only thing I have to order is the model rocket engines, everything else I can find around school. I like to do this in regular physics classes right after the unit on impulse and momentum, so they can use a lot of the calculations they have practiced making, but I've also done it with my AP Physics classes at the end of the year as a fun project to kind of tie everything together.

If you don't like the big rocket engines, you could easily scale down the size, we use C6-4 but I have done them with toilet paper tubes and size A engines.

At the end of this instructable, I included a video that I share with the kids that shows all the steps being done. This helps so I don't have 30 kids all asking different questions because they are on different steps.

Supplies

I have lab groups of 4 to 5 kids, so each group gets the following:

1. A paper towel tube. The kids can bring a nice one from an aluminum foil or plastic wrap roll, but I save all my paper towel rolls for a year and bring them to school.
2. A sheet of cardboard at least 12" x 12", bigger if you want to let them prototype. I save the boxes that our reams of paper come in and each class uses a whole box. You could also use Amazon boxes.
3. Estes model rocket engines. We use C6-5, but you can go as small as you like.
4. A sheet of cardstock or some thick paper. I use a manila folder. Cut in half, one folder can supply two groups.
5. About 4 feet of light string. This is for the parachute, so you don't want super thick string.
6. A small trash bag. I use the ones the custodians put in our small trash cans, they look like they are about 5 gallons or so.
7. A straw. You only need a small piece, so one straw could be cut into 6 pieces for a class of 6 groups.
8. A rubber band, cut at one point so it is a rubber string.
9. Hot glue. I only give each group two sticks so they don't waste it.
10. Wadding paper, a fuse, and the engine plug. These all come with the engines.

I put all the materials (except the engines, fuses, plugs, and wadding paper) out on a table so they can just go get it as they need it. Each table gets their own glue gun and two glue sticks.

Step 1: Step 1: Cut Out Cardboard Parts

I give the kids two papers with outlines of different shaped fins they can choose. There are some small ones that are for stabilization that you can attach higher up from the main fins; I don't ever have them use those. If they don't calculate the center of mass and center of pressure and just put them on randomly to look cool, the rockets never work. Just stick with the larger ones. One of the favorites is the fins with the rounded edge; those seem to make the rocket spin like a football when it lifts off.

They need to cut out either 3 or 4 fins. I have them do 4 because it is easier to space them 90 degrees apart to get them even than it is to space them 120 degrees. I have had one or two groups successful with 5 fins, but never with more than that. If they insist, I always let them try so they can see what happens.

Once the fins are cut out, they need to also cut out 4 circles that are the same diameter as the cardboard tube they are using. It is important to make sure they don't cut it too small; you can always make them smaller but can't make them bigger once they're cut.

I strongly suggest that you do not glue the fins on until the very end when the body and nose are done. If you do put them on early, there are more opportunities for them to get bent or ripped off.

Step 2: Step 2: Make the Engine Mount and Parachute

The files in this section have pictures and directions for these steps. This is the part that takes the longest.

For the engine mount, take 2 of the circles that were cut out, and use the engine to cut out a hole with the same diameter as the engine in the middle. Once you have two of those, use home hot glue and attach them both about an inch from the end. I like to lay a bead of glue, then slide the mount up onto the glue and put a little more glue. Don't skimp on the hot glue, and be sure to let it dry.

For the parachute, take the trash bag and cut about 6 inches off the top of it. Then lay it out and poke 4 holes 90 degrees apart from each other about an inch from the outer edge. Take your string, cut it into 4 equal pieces, and tie one end on each hole. I cover each knot with tape to make sure that it doesn't tear out.

When the engine mount is dry, you can glue it in. You want to make sure the hole in the engine faces out (for obvious reasons). I have had groups go out to launch and when we go to put in the fuse we all laugh at them because they glued the engine in wrong.

Dry fit the engine mount first. If it doesn't fit, trim it a little. Again, don't cut too small; you can always remove material but can't add it back on. I put a bead of glue around each engine mount, then stuff it in quickly into the tube. Try to get the bottom of the engine lined up with the bottom of the tube. Once it's in, put a ring of glue around the mount that is showing to make sure it stays. Don't skimp on the glue; I have seen engines not mounted very well that basically disembowel the rocket and fly out the top and chase us all around the field. Funny, but not fun.

Step 3: Step 3: Make and Attach the Nose Cone

The file in this section has the directions and pictures for this step.

For the nose cone, use a compass to cut a circle with a radius of about 9 or 10 cm. Mark the center point and cut a line from the outer edge down to the center point. Then slide one edge over the other to make a cone. Put a piece of tape on it to secure it in place.

Put the nose cone inside the body, and trace a line around where the cone meets the body. BE SURE THE CONE IS STRAIGHT. If you have it in uneven, the nose will be crooked. Takeout the cone, and cut spikes all the way around down to the line you drew. Put one of the leftover cardboard disks and insert it inside the cone, fold the teeth down on it, and glue down with hot glue. You might have to trim the disk to fit. On the last cardboard disk, poke a hole in the middle and feed your strings from the parachute through. Place a cut rubber band inside the hole also, and then put a blob of hot glue on the ends sticking out of the hole and glue the nose cone to it.

To attache the nose cone, put a dab of glue inside the tube and then place the other end of the rubber band in the glue and let it set up. Don't put it too close to the end of the tube. I put it about 5 cm down the tube.

Step 4: Step 4: Fill Tube and Attach Fins and Straw

Once the glue inside the tube is dry, students can stuff the wadding paper down. Give them about 4 sheets, and they loosely crumple it and stuff it in. Then pack in the parachute and the nose should fit on top. If the cardboard disk does not fit, you can trim it a little. It should fit snugly. If it has trouble staying, a small piece of tape can hold it on; the charge that shoots out the parachute will be more than enough to eject it.

Once the tube is filled, the fins can be attached. Start by putting one on, and then do the one opposite. I find it easier to eyeball 180 degrees than 90. If you're using 3 fins, use a protractor to help. Make sure they are plumb with the body, and make sure the bottom of the fins extend a little below the bottom of the tube. If they are flush with the tube, when you put the rocket on the metal stand it will short the fuse and it's a hassle to try to set up to launch.

After the fins are on, take a small piece of straw and glue it down along one of the fins. It doesn't matter which one. This will keep the rocket on the launch platform and guide it up.

Step 5: Step 5: Launch!

Now you're ready to launch!

I usually have some questions they answer in the 15 or 20 minutes before we go out and launch when I go around and insert the fuses into the engines myself, and cap them with the plug. Then we take them out and launch one at a time. I let the group decide on one person to launch and one person to record the height, and the rest of the class stands behind a fence (we launch them right near home plate so theres a fence they can all stand around and see).

I have attached a lesson I used with my honors physics class in the past. When we go to launch, they have an altimeter (from Estes) that is point and hold that they can use to measure the angle it reaches, then they can use that and the distance to calculate the height of the rocket. All Estes engines come with information about the impulse applied from the rocket, so we also use that to determine the change in momentum, net force applied, and other things. You could even use a force sensor and make a bracket to hold an engine and ignite it (outside of course) and collect data with a Vernier/Pasco setup and let them make the impulse calculations themselves.

You can make this as detailed or quick as you want. As you can see from the pictures, something they also do . is decorate their rockets. I like doing rockets this way a lot better than the kits that companies like Pitsco sell because it gives them a sense of ownership, that they actually made the rocket from stuff around the house and classroom.