Rocket Shoots

Rocketry

Model Rocketry is a fun activity that you can do with cub and boy scouts. It's very difficult to mess up an event based on flying objects that go whoosh! The trick is to understand the costs and to choose models that can be constructed by the boys with the assistance of their parents. This article will focus on solid fuel rockets.

Note: This page is in progress. If you have specific questions about model rockets, feel welcome to email them to me. I may not know the best answers, but the questions will help me focus the discussion on this page. -- AWM

Rocketry basics:

Layout of a typical Model Rocket
Click the slide for additional details

Cutaway view of rocket engine
Click the slide for additional details

A typical model rocket

This slide (left) from Nasa shows a traditional model rocket. The airframe is reusable and can be flown multiple times. The solid rocket engine is used once and then discarded. Recovery is by parachute.

The birdie rocket (above/below) is similar -- the rocket is reusable, the engine is used once and discarded. The birdie rocket has no parachute. It flutters down like a . . . well, like a badminton birdie.

The bottom slide (left) shows a cutaway diagram of a rocket engine. The propellant is usually black powder, ignited by an electric ignitor (pictured below).

Launch Pads

The Launch Pad and Launch Rod stablize the rocket (i.e. keep it flying straight) until it's gained enough speed for the fins to be effective. The launch rod slips through the Launch Lug -- a short length of soda straw attached to the side of the rocket. The Estes Portapad (right) can be purchased at most stores that sell model rockets. Cost is about $15-$20 for a package that includes a ready to fly rocket and three engines. Portapads can also be purchased on Ebay.

When launching rockets as a group activity, it's useful to prepare several rockets at once. A launch pad for launching multiple rockets can be constructed from 2x4's and a pair of sawhorses. 3/32" x 30" welding or brazing rods can be used as launch rods for small and medium size rockets. In a pinch, a straightened wire coat hanger will also work.

Estes Launch Pad

Estes Electron Beam Controller

A launch controller
with his
launch controller

Launch Controllers

Rocket engines are ignited electrically. The ignitor is a nichrome wire that's inserted into the nozzel of the engine. When electricity flows through the ingitor, it gets hot and the insulation coating the wire burns, which ignites the black powder propellant in the engine.
The Launch controller consists of a battery, wire, and one or more switches that allow the rocketeer to ignite the rocket engine from a safe distance. The most common launch controller is the Estes Electron Beam Controller. This controller comes with many ready to fly rockets and costs about $20 when purchased retail (e.g. at the scout store). You can usually find them on Ebay along with a Portapad for under $10. Or you can make your own launch controller.

The major disadvantage of the Estes controller is that it's powered by 4 AA batteries. Weak batteries or dirty electrical connections can cause problems getting the rocket off the ground -- not a good idea if you have an audience. The launch controllers pictured on the lower left are powered by coffee and a 12 volt battery respectively. The 12 volt battery is much more reliable and permits multiple simultaneous launches.

Sketches of an Estes Ignitor

Ignitor Inserted in Engine

Detail of Ignitor
in Engine
ignitor

Rocket Designs:
These are rockets that have been used at daycamps and pack meetings.

	Birdie Rocket Pack meetings Fall Camporee 2006 District Daycamp 2007
	Quest Viper District Daycamp 2006
	Estes Alpha III Pack, Troop meetings

These rockets were prebuilt and used for demonstrations: