Ready, Aim, SPLASH: water balloon launcher

Grades 4-8

Get ready to launch some serious summer fun! In this engineering challenge, students will work together to build a water balloon launcher and test their designs for distance and accuracy. Explore the forces of tension, trajectory, and gravity—then soak your target with a splash of STEM-powered excitement!

Materials (per team of 3-4 students):

• Large plastic or wooden spoon, or plastic cup

• 3–5 rubber bands or bungee cords

• Duct tape

• Plastic or PVC pipe pieces (or sturdy sticks) for the launcher frame

• Water balloons or soft sponge balls

• Tarp, cones, or chalk to mark target zones

• Towels (optional but encouraged 😄)

Get creative with your own design and get to building, below are some ideas to help get you started!

Step 1: Build the Launcher Frame

Option A: Tripod Frame (Most Stable)

1. Arrange your 3 sticks/PVC pipes like a teepee.

2. Tie the tops together securely with duct tape or string, leaving a wide enough opening at the bottom for stability.

3. Spread out the legs to form a steady tripod base.

Option B: “Y” Frame (Simpler but Needs a Partner to Hold It)

1. Hold two sticks upright in a wide “V” shape or wedge them into the ground.

2. Use a third stick horizontally across the top, like a goalpost.

Step 2: Make the Launch Cup

1. Take your plastic cup and poke 3 small holes near the rim (equal distance apart).

2. Tie a rubber band or string through each hole, creating 3 “handles.”

3. These 3 bands will connect to your frame.

*Alternative: Use an old t-shirt or sturdy fabric to create a pouch, tying 3 rubber bands or strings to the corners.

Step 3: Attach the Launch Cup to the Frame

1. Stretch each rubber band from the cup to the top of your frame, spacing them evenly.

2. Secure them so the cup hangs centered when pulled back.

**Tip: The tighter the rubber bands, the more power you’ll have! Adjust tension as needed.

Step 4: Load & Launch

1. Place a filled water balloon in the cup.

2. Hold the frame steady (or have someone else do it).

3. Pull the cup back gently but firmly—aiming up and away from people and breakables.

4. Release the cup and watch your balloon soar through the air!

***Pro Tip:

• Experiment with the angle of your launch and how far you pull back for the best results.

• Try aiming for a target or measure your launch distance.

Safety Reminders:

• Only use outdoors or in wide, open spaces.

• Don’t aim at faces or fragile objects.

• Make sure all participants are clear of the launch path.