- 1). Drill a hole through the center of a large plastic bottle cap using a drill and a 10 mm bit. A 2-liter soda bottle will work for a small water rocket.
- 2). Fit a car tire valve into the 10mm hole. A standard car tire valve should fit snugly. Attach an air pump with a pressure meter to the tire valve and pump until pressure reaches at least 70 psi.
- 3). Put on a pair of safety goggles.
- 4). Switch on an electric stove burner and set it to a low setting. Hold the bottle by the tire valve 8 to 12 inches above the burner. Slowly increase the temperature of the burner. As air pressure inside the bottle increases, the bottle will become hemispherical and then will stretch to a more elliptical shape.
- 5). Immerse the plastic bottle in water as soon as the bottle has attained the desired parabolic nose shape. If you do not cool the bottle by placing it in cold water, the bottle will continue to expand after you have removed it from the stove.
- 6). Cut off the bottom half of the bottle with a hack saw. Smooth the edges of the bottom half with fine sandpaper. Use this piece as a nose cone. Alternatively, use the entire bottle as a rocket.
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