Some water rocket launchers use launch tubes. A launch tube fits inside the nozzle of the rocket and extends upward toward the nose. The launch tube is anchored to the ground. As the rocket begins accelerating upward, the launch tube blocks the nozzle, and very little water is ejected until the rocket leaves the launch tube. This allows almost perfectly efficient conversion of the potential energy in the compressed air to kinetic energy and gravitational potential energy of the rocket and water. The high efficiency during the initial phase of the launch is important, because rocket engines are least efficient at low speeds. A launch tube therefore significantly increases the speed and height attained by the rocket. Launch tubes are most effective when used with long rockets, which can accommodate long launch tubes.
Flying model rockets is a relatively safe and inexpensive way for students to learn the basics of forces and the response of a vehicle to external forces. A model rocket is subjected to four forces in flight; weight, thrust, and the aerodynamic forces, lift and drag. There are many different types of model rockets. One of the first and simplest type of rocket that a student encounters is the bottle, or water rocket. The water rocket system consists of two main parts, the launcher and the rocket.
These are my plans for a home made water rocket launcher. It is based on the 1"Clark Cable " design, and uses cable ties to clamp the rocket in place prior to launch. A locking collar holds the ties in place until the moment of release.Feel free to copy my design, however you build and use it entirely at your own risk. As with all things exciting, water rockets do come with some risk attached, launch you rocket responsibly and safely, especially keep other peoples and your own safety in mind. What you do with your water rocket and launcher is entirely your own responsibility.
WHAT ABOUT FINS ON THE WATER ROCKET? When we taped the Ask This Old House segment about water rockets, I was the overhead launcher construction expert. But the show rs"s producer, Chris Wolf, was the water rocket expert. He made some cool rockets with nose cones and fins, and they soared really high, much higher than the plain old bottles that I launch. Bottles tend to tumble around in the air, creating a huge amount of drag, so they doncrs"t go as high. Fins keep the low profile of the nose pointing up, so the rocket goes higher.