100-Yard Paper Rocket Launcher

This is my take on the compressed air paper rocket launcher. Enjoy!

Be sure to check out STEM-Inventions.com, an amazing collection of hands-on projects for kids!

Electric Trigger mechanism

• Sprinkler valve modified with momentary push button
• Or you can DIY the valve assembly:
• 1" in line sprinkler valve
• 1" threaded male adapter
• 1"-1/2" slip reducer
• 9V battery clip
• Momentary push button
• 1" PVC pipe and two end caps, for button handle

Tools for the air pressure chamber:

• Large PVC cutting tool
• Drill
• Mallet
• Pipe wrench
• Disposable gloves
• Sandpaper

Materials for the air pressure chamber:

• PVC Primer and solvent weld
• KwikPlastic (or similar)
• Tire valve
• 6" sections of 2-inch PVC (x2)
• 2" slip fit end cap (x2)
• 2" slip fit T-joint
• 2" to 1/2" slip fit reducer (to connect to valve)
• 2" section of one-inch PVC
• 24" piece of 1/2-inch PVC with tapered end (x1)
• Bicycle pump with PSI gauge

For the base:

• 12" cable ties
• PVC elbow joints (x2)
• 12" piece of PVC with two holes drilled about 4" apart (x2)
• 8" piece of PVC

The total cost is about $70, excluding all tools and solvent weld. In my line of work, it is well worth the initial investment because the paper rocket activity is very cheap, less than $0.15 per student.

For paper rockets:

• Card stock
• Masking tape
• Scissors

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This launcher works up to 60psi. You can wire in a second 9V battery to get the launcher up to 100+psi. 60psi is enough to achieve spectacular results. Pressures above 60psi dramatically increase the risk of exploding the rocket.

(and by the way, you might want to protect your work surface a bit better than I did)

The button circuit was originally purchased from a website that no longer exists. However, it's very simple to build yourself. Simply wire the button, 1 or 2 9V batteries, and the wires from the electronic sprinkler valve together in a single series.

All you need is cardstock, tape and scissors.

It's easy to build a rocket that can reach a distance of 50 feet. However, making an ultra-high-performing rocket is actually quite challenging because all aspects need to be designed to near perfection. At high speeds, tiny imperfections are quickly blown out of proportion because the forces acting upon the rocket are intensified. For example, a nosecone that leans slightly to one side may not significantly influence the rocket's performance at 40psi, however at 60psi that nosecone may create an imbalance of friction created by the air rushing by, causing the rocket to turn sharply and tumble to the ground.

For this reason, take your time while creating & attaching each part of the rocket. And with that in mind, here's how to make a high-performing rocket:

Follow these safety precautions regardless of whether the chamber is pressurized or loaded with a rocket.

• Never allow students to use the launcher unsupervised. Disable the launcher by removing the battery (or pump or launch tube) if you have to leave the launcher unsupervised.
• Never allow anyone to put their face near the launch tube. Air expelled from the tube, if forced into someone's nose or mouth, is powerful enough to cause the lungs to rupture. This is very serious. Tell your students about this and they will be frightened enough to never get near the tip of the launch tube.
• Never stand directly in front of the launcher, even if a rocket is not loaded. At point blank, a rocket shot from the launcher can cause serious injury.
• The student holding the button should keep his/her trigger finger off of the button until the final countdown is initiated. The button is sensitive and can easily misfire.
• Use a bright rope to define a safety zone that the students may never cross, even while loading their rocket.
• Have a countdown before each launch as a way to alert people in the area (and to make each launch more exciting!)

Common design flaws

• Fins that are not attached straight, or the leading tip of the fin is not secured, will cause the rocket to tumble at high speeds.
• Fins that are too big create too much lift and/or drag.
• Fins that are too small may not provide enough stability.
• Fins that extend too far from the fuselage are prone to wobbling in the wind, causing instability.
• Nosecones that are not secured well enough will explode off of the rocket.

Tips and troubleshooting

• Rockets tend to explode at pressures above 60psi. If you choose to mod the button with a second 9V battery, have the students tape up every seam many times over.
• Inspect the rocket before each flight and use your hands to straighten out the fins and nosecone, which will inevitably become bent over time.
• I usually refrain from interfering with students' designs, however if a student has created a poorly built fuselage I will step in and help them. Making a new fuselage after attaching everything else can be a hassle.
• Young students (grades 3 and below) may have a hard time rolling a tube of cardstock, so I usually do that step as part of my prep.
• If you don't have access to a huge open space, you can set up targets like stacked cardboard boxes and aim for those. Be extra cautious here.
• When storing the launcher, remove the 9V battery, or at least make sure the button is uncompressed or else the battery will quickly drain.