Engineering Activity: Balloon Rockets

Philippe M. Wilson ECE
Tanna B. Alford MechE, English
Lars S. Hanson CivE, EPP
Carnegie Mellon University


The purpose of this project is to design an activity that will expose children of varying ages to the challenges and rewards of engineering. The students will be given a variety of materials along with the task of constructing a device that meets given design requirements. Although design requirements will vary based on age group, the activity will focus on the movement of the device along a suspended line. The choice of interface between the device and the line will allow the students to learn about friction through hands-on experimentation. In most cases, students will construct a balloon or rubber band powered device that will travel along a fishing line. The students will work in teams to discuss design options. By using the limited materials provided to build the devices, the students will learn about the tradeoffs involved in an engineering design process.


Engineering is the adaptation of materials to meet society's needs. While a scientist seeks to discover more about the world around him/her, an engineer uses the physical principles discovered by scientists to achieve a goal or solve a problem. Engineers apply knowledge of the world to create everything from buildings to machinery to electronics. Typically they work in groups, usually called design teams, to create whatever the company or research institute requires. A prototype, or functional version, is usually created to determine if the final product will be satisfactory. This prototype is tested and improved if necessary before a product is finalized. The phrase "back to the drawing board" refers to this iterative process of modifying a design in order to achieve the desired result.

Physical Principles Explored (Friction, ...)

Friction is a very important physical principle that affects every facet of everyday life. It is, at the most basic level, a force created by the rubbing of two surfaces. While a great deal of friction is generated between rubber and glass, cloth and hardwood floors exhibit very little friction. Friction is a significant engineering concern because any moving components of a design will be affected by frictional forces. Items such as manufacturing machinery, aircraft, and automobiles must be designed with a great deal of consideration given to friction. Sustained friction can cause significant wear and can generate a great deal of heat. Since this could cause damage to moving parts, engineers look for ways to reduce friction by using things like lubricants and roller bearings.

Other physical principles affecting this activity are mass, propulsion, aerodynamics, and balance. For students already familiar with the concept of friction, the inclusion of at least a basic discussion of some of these principles may be of great benefit to the student. The additional perspective will also serve to demonstrate the great deal of thought that goes into making design and engineering decisions.

Balloon Rockets & Friction

The balloon rockets are intended to travel along a guide line, with the ultimate goal being maximum travel distance. The rocket is powered by the release of the air in the balloon. With a standardized balloon size for all competing students/groups, the rocket with the least friction between it and the guide line should go the farthest (ignoring mass, aerodynamics, etc). The maximum balloon size can be set with a box that an inflated balloon must fit inside, or with a maximum length if using elongated balloons.

Balloon Rocket Activity

Physical Principle Demonstration

Explain the basics of the physical principle(s) appropriate for the class. Demonstrate the principle(s) using materials in a way not directly related to the construction of balloon rockets. For example, demonstrate friction with various pairs of objects that the students may examine.

Divide Into Groups

It is recommended that students be divided into groups to stimulate a discussion of design decisions.


Give the students time to examine the available construction materials and construct an initial prototype. After a set amount of time (10 minutes as a minimum), the different teams should observe each other launching their rocket. This will allow the groups to compare their approach to those of other groups. If there is enough time, it is recommended that students attempt to improve their designs. This will enhance their concept of engineering and its iterative design process.


Additional Materials

Student Worksheet [pdf][html][txt]