Rockets Class
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Lesson 2: Stomp Rockets
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Introduction: Stomp Rockets

To get you started in the world of rockets we'll construct a very simple one to help you understand some of the science that goes into rocketry. Stomp Rockets are a great way to learn, in a simplified and fun way, what is happening when a rocket is launched. Using everyday household and hardware store materials, you can construct a rocket that uses air pressure to launch a paper rocket about 30 feet!

To achieve this, we'll use a plastic soda bottle to force air through a pipe and launch a projectile (similar to how you can use a straw and wadded paper to make spitballs), except we're firing a rocket from over the barrel of a tube instead of inside it. Plastic soda bottles are a great choice for this since they are designed to handle pressure from a carbonated beverage and are well suited to the rigors we're going to put them through.


Tools + Supplies

Stomp rockets require a tubular apparatus to channel air into the rocket to achieve lift off, for this we'll use inexpensive and easily found PVC pipe. The fittings used are minimal and keep the apparatus simple yet functional, however you can experiment and make your own launcher design.

Here's the minimum of what's needed:

*depending on the angle you want your rockets to shoot, straight up or at an angle


Cut Pipe for Apparatus

PVC pipe is usually sold by lengths of 10'. The measurements provided here to build the PVC apparatus are guides to provide safe distances between elements, however you're free to modify the ports to work with your own custom design.

PVC Cut List:

  • 1 x 40" section - air tube
  • 2 x 12" sections - stabilizers
  • 1 x 6" section - connector to firing tube
  • 1 x 12" section - firing tube
  • 3 x 14" sections - rocket forming tubes

The lengths don't need to be totally accurate, as they are guidelines to create your own launch apparatus. However, the rocket forming tubes need to be long enough to wrap the printer paper around and form the rockets we will fire (14" works well). More on how to roll the tubes after the apparatus assembly.

After cutting the PVC pieces, set the rocket forming tubes aside so they don't get mixed up with the apparatus build.

The cut ends can be cleaned up with a file. Cleaning the ends removes burrs and makes for a smoother interface when we cement the pipe to the connectors later.


PVC Glue - End Caps

Once all the pieces are cut we can start to assemble them. To connect PVC pipe and their fittings together there's a special glue that's used, a solvent cement. When applied, the cement will cause a chemical reaction with the PVC and melt the plastic a little, so that when two pieces are cemented together the melted sections bond and form a watertight connection.

Below is the basic launch apparatus we're going to make. You can probably determine how to make it just from looking at the image, but I'll walk you through the process.

Before starting any cementing, it's a good idea to make sure you're working in a well ventilated area and on a work surface that's protected. PVC cement is a solvent, and dyed a very nice deep blue, so it will stain everything from both the dye and the chemicals in the solvent. Be careful!

Opening the PVC cement you'll see that there's an applicator brush attached to the underside of the lid. This is very handy. I like to apply the PVC cement over the bottle, that way any drips will make it back into the bottle and hopefully not make a mess.

Starting with the end caps and the two 12" PVC stabilizer sections, remove the cement lid and use the applicator to brush on about a 1/2" band of cement around the entire circumference on one end of one of the PVC stabilizer sections. Working rapidly, use the applicator to brush the inside of one end cap. While the cement is still wet quickly insert the cemented end cap onto the cemented end of the PVC pipe and twist until the cap cannot be pushed any further on the end of the pipe.

The twisting action will help distribute the solvent and ensure a tight bond between the two PVC pieces. The cement only take a few seconds to completely harden; set aside the cemented PVC stabilizer and repeat the process with the other stabilizer section and end cap.


PVC Glue - 4-Way Splitter

With both stabilizers end caps installed we can attach the stabilizers to the the PVC 4-way splitter.

Using the same cementing technique as before, apply cement to the uncapped ends of both stabilizer sections and any two opposing openings of the 4-way splitter. Insert the cemented ends into the cemented openings of the splitter and twist until all the way on.


PVC Glue - Connector + Firing Tube

The 6" connecting tube and 12" firing tube can be cemented together next using either a 90°or 45°elbow. The choice is yours! If you want your rocket to fire straight up, use a 90° elbow. To shoot in an arcing trajectory away from you, use a 45° elbow.

Since height is difficult to measure in an open area, and I wanted to see how much range I could get with my rockets, I chose a 45° elbow for this apparatus. The 6" and 12" PVC sections were cemented into either end of the 45° elbow and twisted into place until fully seated.


PVC Glue - Firing Tube to 4-Way

Once the glue on the firing tube has set, the 6" connector section can be glued into one of the two remaining openings of the 4-way splitter. Be careful here as the alignment of the firing tube and connector should be perpendicular (straight up) to the 4-way splitter and stabilizers. I found it easiest to have the 4-way connector laying flat on the table so it's easy to see if the firing tube section is perpendicular while the glue dries.


Bottle Interface

To get the air from the plastic 2 liter soda bottle through the cap and into the PVC apparatus, there needs to be a hole in the cap that will allow the air to pass through.

Using a ½" drill bit in a power drill, an opening was made in the middle of the plastic bottle screw cap. Instead of clamping down the cap, I found it easier to drill the opening while the cap was still on the bottle.

Once the hole in the cap has been made, remove the cap from the bottle and set the bottle aside. Warm up the hot glue gun and apply a generous bead of glue to the inside of the 2" PVC connector. Be careful not to get any glue inside the 1" opening, only around it.

Place the drilled plastic bottle cap into the 2" connector and line up the drill opening with the 1" opening at the bottom of the connector. Hold firmly in place until the glue has cooled and securely holding the cap in place.

To ensure a good seal between the plastic cap and the PVC, and to prevent the cap from accidentally being blasted out of the 2" connector, more hot glue was inserted between the outside of the bottle cap and the inside of the 2" connector.


PVC Glue - Bottle Connector

The final piece of the launch assembly is the connection between the apparatus and the bottle that will be the bladder that forces air through the PVC tube.

Our PVC pipe is ½" in diameter, and the soda bottle screw cap is about 1-¼", so we'll need a way to connect this cap to the rest of the apparatus. Since PVC pipes come in all kinds of diameters there are a whole host of connectors and reducers that help us solve this problem. What we need is a connector that is large enough on one end to accommodate the 1-¼:" plastic screw cap and then reduces down to the ½" diameter of the pipe we are using.

At my hardware store I could find a 2" to 1" reduction connector, which took me part of the way to my ½" goal. Then I used a 1" to ½" connector so the bottle could connect to the rest of the assembly.

If your PVC connectors are threaded, PVC cement will work just as well. Cement was brushed onto the threaded interior of the 2" to 1" connector and then threaded end of the 1" to ½" connector. The two components were quickly screwed together as far as they could go before the cement set and seized the two pieces together.


PVC Glue - Bottle to Air Tube

With the cap installed in the bottle connector the last component can be installed on the launch apparatus.

Using more PVC cement glue the ½" opening of the bottle connector to one end of the 40" air tube section of ½" diameter of PVC tube. Then, connect the other end of the air tube PVC section to the last opening of the 4-way splitter with stabilizer arms.


Making Rockets!

With the assembly finished we can turn our attention to making rockets to fire!

All you need is standard printer paper (8.5"x11" or A4) to make your own rockets. Using a template to make your rockets is not required, but is a very fun addition.

Download stomp rocket template here and print off a few copies, then cut out along the scissor lines shown to make the shapes for the rocket body and fins. I made my template based off Seamster's paper stomp rocket.

The areas to be discarded after cutting are gray with large X's on them. You should be left with a long rectangle that will be the rocket body and 3 chevron shapes that will be folded into fins.

The instructions are also printed on the template, allowing you to hand out a bunch of rocket templates to others without having to explain to them how and where to cut.

Download stomp rocket template here!

Decorate Your Rocket

Everyone knows that decorated rockets go higher and further than undecorated ones.

Take some time to color your rocket or add any designs you like. Maybe you've got your own space agency with a logo, or want to add some alien passengers. There are no rules when it comes to decorating, so let your imagination run wild! On the rocket template there's a clearly marked section where you can decorate. Areas outside the decoration zone will not be seen when the paper is rolled up and formed into the rocket shape.


Rocket Forming Tubes

The PVC rocket forming tubes we set aside earlier are now needed to make our rockets.

Before we start rolling the decorated rockets on the PVC, we need to first roll a blank sheet of paper onto the PVC rocket forming tube. Roll one sheet of printer paper lengthwise onto the PVC pipe and tape it in place.

This sheet of paper will increase the diameter of the PVC, allowing the rockets we roll onto it to be slightly larger than the bare PVC pipe of the firing tube on the rocket launch assembly. This will make it easier to slide the paper rockets onto the pipe.


Roll Rockets

Place your decorated sheet with the design facing downward and roll lengthwise onto the rocket forming tubes, starting with the instructional area on the template and rolling until the decorations overlap the instructions. Sparingly use tape to secure the decorated rocket along its length to prevent it from unrolling. Make sure not to tape the rocket to the rocket forming tube.

Each paper fin will have dotted fold lines that show where to fold to get the right shape. Start by folding the fin in half, then fold each edge the opposite direction to make the mounting edges for the fin.

The template has marked areas where each fin can be attached after it's been rolled onto the rocket forming tube. Use tape to secure the fins to the marked areas on your decorated rocket.


Ballast

If we just taped the tip of the rocket and tried to launch they wouldn't go anywhere, as there needs to be weight in the rocket nose that will give the rocket mass for inertia when it's launched. Inertia is the scientific word to describe an object to continue motion in a straight line until it's changed by an external force, like gravity and drag. By adding weight to the top of the rocket, we're giving it mass which will allow the rocket to use the momentum we give it on launch and continue it's forward momentum. The weight added to the rocket is called ballast.

Since our rockets are very light they don't need much ballast; paper towel or cotton balls work well for ballast. With the rocket still on the rocket forming tube, wad up your ballast and place it on the top of your rocket. Slide your rolled rocket up the tube slightly to encapsulate the wadding.

Secure the wadding inside the decorated tube with some tape, ensuring not to tape the rocket to the forming tube.

Cover the entire top opening with more tape, sealing the ballast inside the rocket body and forming an airtight seal at the top of the rocket.

The rocket is now complete and can be removed from the forming tube. Continue forming as may rockets as you like, and if you made additional forming tubes you can have a few rocket making stations going at once.


Launch Preparation

As with all rockets, you're going to need a suitable place to launch. Though these rockets might look harmless, they can easily reach a distance of 30 feet, so plan your launch area in a wide open space away from houses, power lines, trees, and eyeballs.

With all your rockets pre-rolled, place one rocket on the angled end of the firing tube and ensure it's on all the way.

Once the rocket is on the firing tube the empty bottle bladder can be added. By adding the bottle after the rocket has been installed you minimize the risk of accidentally launching the rocket before you're ready.

Screw the bottle into the threaded end of the launcher until it's tight and set the bottle and launcher assembly down on the ground.


Launch!

With your custom decorated rocket on the launcher, step up to the bottle and jump as high as you can and land with both feet on the bottle.

Timing your jump for both feet to land on the bottle will delivery the maximum pressure through the launcher and into the rocket, making it travel as far as possible. The same bottle bladder can be used multiple times, but after a few launches you'll notice that the bottle might be cracking and needs to be replaced.


Science Moment

With the weight ballast at the top of these paper rockets, and the overall weight of the rocket being relatively light, the center of gravity is very close to the rocket tip. The pressure applied to the rocket to achieve blast off is located behind this center of gravity, which as we learned is exactly what makes for good rocket performance.

After you've launched a few rockets, take a moment and think about the following changes you could make to your rocket:

  • Is there a limit to how much ballast weight you can add to the top of the rocket?
  • What if you removed the ballast weight entirely?
  • Does the flight pattern change when the weight is located somewhere other than the top?

Did you make any improvements to your rockets after considering the above? Share your thoughts in the comments below.


With your first successful launch complete we're ready for a more complex rocket. This stomp rocket used air pressure to force a paper rocket into the air. Next up we'll look at combining air pressure with a ballast to launch a heavier rocket into the air.

Strap in, Cadet!

CLASS PROJECT

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