Rechargeable Rocket Launcher

Powerful. Portable. Effortless.

The Rechargeable Rocket Launcher is the first of its kind. Unlike traditional compressed air launchers, this design is completely self-contained, yet equally powerful. Launch rockets over 300 feet without laboring over a bicycle pump, or restricting your location to an outlet for a plug-in air compressor.

Weighing in at just 4lbs, the Rechargeable Rocket Launcher takes little effort to maneuver, and aiming is perfectly intuitive. The ergonomic design makes this rocket launcher feel ultra-gratifying and fun to fire.

Perhaps best of all, it's intentionally designed to look as awe-inspiring and impressive as it functions. Capable of 25 consecutive launches at 60PSI, you'll feel absolutely complete by the time you need to recharge.

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Compressed air and high-speed rockets are inherently dangerous. Be smart.

Be sure to check out my book, Launchers, Lobbers, and Rockets Engineer!

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Tools

• hot glue gun with safety tip
• pipe wrench
• pliers
• scissors
• mallet
• measuring stick
• permanent marker permanent marker
• soldering iron
• power drill
  • 1/8" bit
  • bit that's wider than the tire valve
  • bit that's wider than the button

PVC

• nine inches of 2" schedule 40 PVC
• fourteen inches of 1" schedule 40 PVC
• ten inches of 1/2" schedule 40 PVC
• one 2" coupling
• one 2" end cap
• one 2" to 1" slip reducer
• one 1" end cap
• one 1" tee
• one 1" to 1/2" slip reducer
• two 1" elbows
• two 1" threaded male adapters

Adhesives and tape

• PVC primer and solvent weld (glue)
• epoxy, or other glue that can bond metal to plastic
• hot glue
• electrical tape
• thread sealing tape

Electronics

• 9V battery
• 9V battery clip with leads
• momentary push-button switch
• electronic 1" in-line sprinkler valve
• rechargeable air compressor

Other parts

• clamp-in tire valve stem
• 1" rubber stopper

Optional (not pictured)

• 80 grit and 120 grit sandpaper
• Spray paint; dark steel and fire orange
• blue painters tape
• respiratory mask

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Throughout the PVC assembly steps, lightly whack the freshly-glued components together with a mallet to ensure that they're fully connected.

Pressure Chamber Valve

1. Select a drill bit that is slightly wider than your clamp-in tire valve stem. Drill a hole in the center of the 2" end cap. Drill slowly and with even pressure. If you drill quickly and forcefully, the bit may catch onto the end cap and wrench it from your hand.
2. Remove the nut, washer, and thick rubber gasket from the clamp-in tire valve. Insert the valve through the hole from the inside of the end cap. Place the washer and nut back onto the valve.
3. To tighten, grip the nut with a pair of pliers and use your free hand to push against the valve from the inside of the end cap. The friction from the rubber seal on the valve, plus your pressure, should be sufficient to keep it in place as you tighten the nut. Continue tightening until the valve's rubber seal is pressed tightly against the inside of the end cap.

Pressure Chamber

1. Read and follow the directions on your PVC primer and solvent.
2. Glue the end cap with the valve onto the 9-inch piece of 2" PVC.
3. Glue the coupler on the other end, and then glue the 2" to 1" reducer into the coupler as shown.

Stock

1. Cut out three pieces of 1" PVC pipe: Two of those pieces are 2-1/4" long. The third piece depends on the size of your air compressor. In this example, the third piece is 2-5/8". This will allow the air compressor to fit snugly between the pressure chamber and the sprinkler valve.*
2. Connect the elbows with the 2-5/8" piece. Make sure the elbows are aligned. Glue the remaining 2-1/4" pieces into the open elbow connections to complete the stock.
3. Glue the stock into the 2"-1" reducer to complete the pressure chamber and stock assembly.

*Unless you are following this Instructable word-for-word, I strongly recommend dry-fitting the components with a mallet and check to make sure that your air compressor its between the pressure chamber and the bottom of the stock. Ideally there should be no more than 1/16" of clearance between the compressor and the PVC parts.

Handle

1. Cut the remaining 1" PVC into a 2-1/4" and a 5" piece (the length of the 5" piece does not have to be precise).
2. Fit the 1" rubber stopper into the 5" piece. This will help prevent turbulence and air loss when the launcher is activated.
3. Drill a hole that's slightly wider than your push-button switch about 1.5" from the top of the 5" piece. Drill a second 1/8" hole directly opposite of the first one.
4. Glue the 1" tee onto the 5" piece. Make sure that the holes are aligned with the open tee connections.
5. Glue the 1" to 1/2" reducer into the open tee connection that's facing the same direction as the hole for the button.
6. Glue the 2-1/4" piece into the remaining tee connection, and the 1" end cap onto the bottom as shown.

Barrel

The launch barrel does not need to be glued into the handle as long as it dry-fits snugly. This will allow you to remove the barrel, making the Rechargeable Rocket Launcher even more portable. You can also swap out barrels of different lengths to change the appearance of the launcher.

Optional: Taper the tip of the barrel to make it easier to slide rockets on

• Sand one end of the 1/2" PVC pipe with 80 grit sandpaper, then 120 grit.
• It's not necessary to have a long taper. A short, angled taper is sufficient.

Painting won't make this project work any better, but it'll certainly make it look powerful!

I decided to paint at this stage in the project to cover up PVC primer stains, but before assembling the final components to avoid the necessity of masking off most of the pipe. You could paint the pieces individually and then glue it together, but there's greater risk of needing to re-paint something.

The disadvantage of this option is that it still requires some masking. Painting is not one of my strengths, so if you have a better method, please share.

1. Read and follow the instructions on your spray paint cans.
2. Cover all open connections with blue painters tape as shown. Cover the tire valve as well (not pictured).
3. Paint the orange parts first. Wrap blue painters tape around the 2" end cap, 2" coupler, and 2"-1" reducer. Put on your mask, then paint the pieces as shown.
4. Wait for those pieces to fully dry. Keep the tape on the open connections, but remove the tape from everywhere else.
5. Cover the 2" pipe and the stock in tape, then paint the remaining pieces steel grey.

Use nail polish remover to remove painting mistakes.

Attach the threaded adapters

1. Wrap one layer of thread sealing tape around the threaded part of each 1" adapter as shown.
2. Screw an adapter into each end of the sprinkler valve. Tighten using the pipe wrench once it becomes too difficult to turn by hand. If you've painted the adapters, then wrap a cloth around it before tightening to prevent the wrench from stripping the paint.

Assemble the rocket launcher components

IMPORTANT: The sprinkler valve only works one-way. If you install it backwards, the rocket launcher won't work. Make sure you know which direction the air will flow in. Most electronic sprinkler valves have embossed arrows on it. I strongly recommend clearly marking the direction of the valve flow with sticky notes or other means before continuing.

1. Carefully glue the sprinkler valve onto the pressure chamber and stock as shown. Make sure the valve flow is moving AWAY FROM the pressure chamber and stock assembly.
2. Working quickly, make sure that the sprinkler solenoid is pointing directly down. This will ensure that the other side of the valve is flat, which will be important when the air compressor is added.
3. Carefully glue the handle onto the sprinkler valve as shown. Make sure the valve flow is moving TOWARD the handle.
4. Again, work quickly to ensure that the handle, solenoid, and stock are aligned with each other.

Glue the air compressor

1. Connect the air compressor to the clamp-in tire valve, then position it between the pressure chamber and sprinkler valve as shown.
2. Use a few beads of hot glue to attach the air compressor in place. Hold the compressor in position until the glue dries. This will keep the air compressor in position while the epoxy sets.
3. Mix about 1/4oz of epoxy. Lay the rocket launcher on it's side. Scoop up the epoxy with a plastic spoon and carefully pour it between the air compressor and the sprinkler valve, and between the 2" coupler.

The goal of this technique is to rely on the sludge-like viscosity and quick curing time of the epoxy to stick between the components and not leak out the other side. Therefore, you need to have minimal clearance between the air compressor and the surrounding pieces. If your clearance is more than 1/16"-1/8", then you may want to glue on the air compressor onto the sprinkler valve before assembling the rocket launcher.

Alternatively, you can skip using epoxy altogether and substitute it with lots of hot glue. The hot glue won't adhere well to the stainless steel compressor, so you may need to sand it with some rough grit sand paper to give it enough bite.

Solder and wire the trigger

Note: The sprinkler valves that I've used for rocket launchers have symmetric polarity, meaning it doesn't matter which way the electricity flows. Check your valve's polarity before continuing.

1. Insert a solenoid wire and a 9V battery clip wire through the 1/8" hole in the handle, and out of the larger hole.
2. Solder those wires to the leads on the momentary push-button switch. Wrap the leads in electrical tape.*
3. Solder the other battery wire to the other solenoid wire. Wrap the connection in electrical tape*
4. Clip on the 9V battery and test the connection.
5. Apply hot glue around the larger hole, then insert the button. Plug the 1/8" hole with hot glue as well. Although the rubber stopper should prevent air from flowing into the handle, the hot glue will ensure that no air escapes.

Note: For pressures beyond 70PSI, you may need to wire a second 9V battery in series with the first one.

*This step was totally outside my comfort zone - usually I just twist wires together. If I were to do this again, I would also probably apply heat shrink tubing instead of electrical tape.

Tidy the wiring

1. Hot glue the wires to the underside of the handle as shown.
2. Bundle the excess wires together, then tape it onto the solenoid.
3. Tape the 9V battery onto the side of the solenoid. This will make it easy to replace.

Important: Make sure you wait at least 24 hours before testing the rocket launcher. PVC solvent and epoxy usually require many hours to fully cure.

The rocket launcher is complete!

Time to make some rockets!

A rocket launcher is only as good as the rocket it's shooting. You may not notice a significant difference between a decent rocket and a finely-crafted one if they're launched at 20PSI. However, at higher pressures, even small imperfections and material variations can make the difference between a mediocre launch, and a stellar success.

Therefore, I strongly recommend using these materials, and building each rocket with diligence.

• 8-1/2x11", 65lb card stock
• brightly colored duct tape*

• 1/2" PVC at least 12" long

*Bright colors that contrast with your surroundings will make your rockets much easier to find.

Make the rocket fuselage

1. First wrap a layer of duct tape around the PVC pipe. This will make it slightly thicker, which will ensure that your rockets will slide smoothly onto the launch barrel. This is especially important if you painted the barrel.
2. Apply a piece of duct tape on the short end of the card stock*, adhesive-side up. Place the PVC on top of the paper on the opposite end.
3. Tightly roll up the paper around the pipe until it rolls over the tape and forms a tube.
4. Slip the fuselage off of the pipe. Apply a second piece of tape along the fuselage to cover it completely. This will make it easier to find, and help it hold up better in moist conditions.

*I prefer an 8-1/2" fuselage rather than an 11" fuselage. The longer rockets have more surface area, which will produce more drag. Long rockets are more stable, however if you build your fins well, it shouldn't matter.

Attach the fins

1. Cut out three identical triangles from another piece of card stock. This example uses fins that are approximately 3/4 x 2 x 2-1/4".
2. Cut a piece of duct tape that's the same length as the fin, then place the fin on it as shown.
3. Fold the tape along the bottom edge of the fin up, then carefully position the fin about 1/2" from the back of the rocket. Make sure the fin is perfectly straight.
4. Fold the tape over the fin, then apply another small piece to cover any visible paper*.
5. Repeat two more times, making sure that the fins are evenly spaced.
6. Cut off the back 1/4" of the rocket to remove any duct tape fringes that might make it difficult to fit the rocket onto the barrel.

Avoid making fins larger than this, or using more than 3 fins. The more fins there are and the larger they are, the more drag your rocket will have. However, I don't recommend using two fins, otherwise your rocket may not be stable in every direction.

*Covering the fins in tape serves several purposes. 1) It helps the fins keep its shape after impact. 2) It protects the fins from moisture. 3) It prevents the fins from bending under the extreme aerodynamic forces that occur shortly after launch.

Make the nosecone

1. Cut out a piece of card stock that's about 3x3". The exact shape and size is not important right now.
2. Cut to the center of the card stock, then overlap the two flaps as shown.
3. Continue pulling and curling the two flaps together until a cone with a 3/4"-wide base forms. Hold the cone together with a small piece of tape.
4. Trim away the bottom of the cone until the base is as wide as your fuselage, about 5/8"

Attach the nosecone

1. Cut out four 1x4" strips of duct tape. Apply each strip from the middle of the nosecone to the fuselage. This technique will prevent the nosecone from blasting off of the tip of the rocket.
2. Cover any remaining exposed paper in tape.

I strongly recommend creating at least three rockets before launching - you may be surprised how easy it is to lose one. I think it's more fun to lose one of three rockets and keep launching than it is to lose your single rocket, then pause to build another one before continuing.

Make sure your rocket launcher works safely

Testing the rocket launcher before using it will ensure that your first launch is a success.

Important: Make sure you wait at least 24 hours before testing the rocket launcher. PVC solvent and epoxy usually require many hours to fully cure.

• Set the air compressor to 50PSI and turn it on.
• Listen for leaking air. You can patch leaks with epoxy. The sprinkler valve may also have a manual release valve, so check that as well if you hear leaking air.
• When the launcher appears to be airtight, test the trigger.

Location

• Find a very large, open area with no overhead obstructions. You'll need at least 250 feet to shoot at 60PSI.
• Select a firing position. Don't aim toward trees, tall grass, streets, houses, etc.
• Avoid crowded parks or other heavily populated areas.

How to launch

1. Follow the instructions on your rechargeable air compressor. Make sure it's fully charged.
2. Set the air compressor to 40PSI at first. Work your way up to higher pressures as you become familiar with the distance your rockets travel.
3. Keep your hand free of the trigger, and load a rocket onto the barrel.
4. For maximum distance, aim up at a 45-degree angle. Press and hold the trigger to fire!

Launcher Etiquette

In my experience, most people are curious about rocket launchers, or at least tolerant. However some people are sensitive to having rockets fired in their vicinity. Follow these guidelines to avoid being perceived as a nuisance.

• Give yourself 150ft of space in every direction, including where your rocket lands.
• Avoid firing with children nearby.
• Never fire in public areas that are hosting an event.
• If you're in a public area and someone asks you to stop, be courteous and oblige.

I created a short video in which I talk about how I designed the Rechargeable Rocket Launcher, and some of the challenges that I personally had to overcome to make this project.