How to Build a Soda Bottle Rocket Launcher

Plastic soda bottle rockets are a popular science lesson used to demonstrate and study the motion of objects and the forces applied to them. These rockets are capable of flying up to 350 feet high, fueled by water and compressed air. A rocket of this type requires a specially constructed launchpad to hold it while it is being pressurized, and to release it once desired pressure has been reached. The materials required to construct the launcher are available at most hardware and lumber stores.

Things You'll Need

• 2 pieces of 2x4 lumber (6 inches and 3 inches long)
• 16-inch-diameter circular plywood base, 1 inch thick
• 3 corner braces, 1.5 inches by 5/8 inch
• 2 mending plates, 8-inch, with screws
• 1 galvanized floor flange, 1/2 inch, with screws
• 1 No. 3, 1 hole, rubber stopper
• 2 hex nipples (brass), 0.5 MIP
• 1 high-pressure air hose, 10 feet, with 1/2-inch outer diameter and 1/4-inch inner diameter
• 1 dowel, 5/16-inch diameter and 36 inches long
• 1 cast female pipe tee (brass), 1/2-inch
• 1 hook-and-loop cable tie
• 4 pan head metal screws, size #12
• 4 wood screws, #10, 0.75-inch
• 2 wood screws, #10, 2.5-inch
• 1 barb splicer, 1/4-inch inner diameter
• Several #64 rubber bands
• Saw
• Drill
• Screwdriver
• Bicycle pump or electric air compressor
• 1 empty 2-liter plastic soda bottle
• 13.5 feet of string

Instructions

Constructing A Soda Bottle Rocket Launcher

1. Screw the galvanized floor flange to the center of the circular wooden base.

2. Slide an end of the air hose into the center hole of the pipe tee and bend the hose so that it extends about 2.75 inches out of the top pipe tee hole. Screw the brass nipples into the top and bottom holes of the pipe tee, allowing the hose to run through the top nipple.

3. Insert one end of the barb splicer into the end of the hose extending through the nipple. Secure the rubber stopper onto the other end of the barb splicer with the narrow end facing out and the wide end near the nipple. Pull the hose until the stopper sits on the pipe tee. Screw the lower nipple into the floor flange.

4. Stand the larger wooden block vertically, facing the flange. Taking the three corner braces, mark screw holes on both sides of the block and on the surface opposite the flange. The braces will mount the block to the base. Drill holes into the block and the base, and screw the block into place.

5. Lay the smaller block on its side and drill two holes straight through the block on either side. Place it next to the flange, opposite the larger block, and screw it to the base.

6. Push the empty soda bottle onto the stopper. This will help align the other parts being added to the launcher.

7. Drill a hole in the smaller block to securely fit the dowel (the launch rod). Position the hole so that the dowel barely rests on the side of the bottle.

8. Drill two holes into the rear top center of the larger wood block. Locate the holes in the middle, about half an inch from the rear side and about 3/4-inch apart. Screws placed in these holes act as pivot points for the mending plates that close inward to support the bottle, then open outward to release it.

9. Drill two more holes into the top block, this time in the front. Place the holes about 1 inch from either side and half an inch from the front. These holes are where the mending plates are screwed into place on the wood block.

10. Align the 8-inch mending plates with the bottle lip, just below the cap screw on the bottle. Adjusting the rubber stopper might be necessary. Position the mending plates so that they "scissor" the bottle's neck, just above the bottle lip. They will hold the bottle in place on the stopper while air is pumped into it.

11. Screw the mending plates into the inward-most holes on the top of the larger wooden block. Keep the plates loose enough to swing from side to side, but tight enough not to rock up and down. Screw the guide screws into the outer holes.

12. Wrap several rubber bands around the short end of the plates, banding them together. You'll have to experiment with the number of rubber bands to get the right amount of tension to pull the other end of the plates apart at launch.

13. Thread the hook-and-loop cable tie through the hole at the long end of the left mending plate, opposite the end with the rubber bands. Make sure to face the tie toward the other plate, as they will need to be tied together. Tie the string to the other end of the tie. The string will be used to pull the tie off to release the mending plates.

14. Connect the pump or compressor to the air hose.

Tips & Warnings

• The basic functioning of the launcher is this: the clamps swing side to side and are banded on the short end. The banded end is pulled apart when the opposite end is tied together with the hook-and-loop tie. At launch, when the tie is released, the banded end pulls together, pulling apart the opposite end of the plates to release the bottle rocket.

• Keep the bottle completely sealed with the stopper while pressurizing. You may need to turn the nipples to raise the stopper if there is air leakage.

• Only a small pull on the string should be necessary to release the mending plates.

• Do not pump the bottle above 50 pounds per square inch. Higher pressure risks exploding the bottle.

• Everyone except the person pulling the launch string should stand 25 to 40 feet from the launchpad.

References

• NASA: Water Rocket Launcher Directions