David M

Building a Water Rocket

Step 1 Define the problem. Using water as a power source to propel a rocket

Step 2: Brainstorming:

These are the four designs that I came up with for my brainstorming.

Research step 3

Drag - Drag is created by air resistance.

Lift - On a rocket, Lift is a side force used to stabilize and control the direction of flight

Thrust - This is the force that produces lift-off, or upward movement of a rocket

Weight - A combination of factors affect the weight of a rocket and can include cargo, passengers, fuel, parts of the rocket, materials, and other items

longitudinal (roll) axis runs lengthwise down the rocket. The rockets tends to twist about this axis.

The lateral (pitch) axis runs side-to-side. Think of being on a seesaw and moving up and down. That up and down movement is your pitch and it occurs along a lateral axis.

The vertical (yaw) axis runs top-to-bottom. On a rocket, yaw is very similar to pitch except that the nose moves side-to-side.

On a "real" rocket, movement along these axes is controlled by adjusting the thrust direction, placing rudders on the fins, and other techniques. For a water rocket, we have to pay close attention to the location of the center of gravity and center of pressure

Newton's Three Laws of Motion

an object at rest will remain at rest unless acted on by an outside force.

This law tells us that force is proportional to an object's mass and acceleration. So if we want our rocket to accelerate, we can increase force or reduce mass

For every action, there is an equal and opposite reaction.

Thrust is an excellent example of this law. The rocket's movement off the launch pad is a reaction to an action created by the motor.

In the case of a water rocket, the rocket reacts to water being forced out of the bottle by moving in the opposite direction.

Stability and Control

  • Roll is a twisting motions about the roll (longitudinal) axis. Roll movement is not really a problem on a water rocket since it does not tend to alter the rocket's flight path.
  • Pitch refers to an up and down movement of the rocket's nose. This movement can take the rocket off of its intended flight path and could result from a gust of wind. Careful attention to the location of the center of gravity and center of pressure will ensure pitch stability.
  • Yaw refers to the side to side movement of the rocket's nose. This movement can take the rocket off of its intended flight path and could result from a gust of wind (very similar to pitch). Careful attention to the location of the center of gravity and center of pressure will ensure yaw stability.

A newton is the metric unit for force. One newton is the force required to accelerate a mass of one kilogram to one meter per second squared.

momentumwater = masswater x velocitywater

momentumwater = momentumrocket


masswater x velocitywater = massrocket x velocityrocket

. Drag occurs when a solid object moves through a gas or liquid. The force of drag acts through the Center of Pressure (CP) of the rocket

To understand the force of drag you must first understand the variables involved. The equation for drag:

Drag = .5 x air density x velocity2 x frontal area x coefficient of drag

Step 4 Identify Criteria and Specify Constraints

Step 5 Exploring Possibilities:

Picture 1 I was trying to make the fins small and light so that the fall time would increase

Picture 2 I made to fins bigger so that it would be more stable even tho it added weight and I made to cone size smaller to try and lesson the weight

Picture 3 I made the fins small again and increased the cone size hoping it would make it more stable.

Picture 4 is basiclally the same as picture 2 just the cone size is bigger to help with drag.

7. Developing a Design Proposal

Take your highest scoring sketch and create working drawings (sketches with dimensions, so that you could build your project). Attach your working drawings to this sheet.

©2012 International Technology and Engineering Educators Association Foundations of Technology, Third Edition/ Technology, Engineering, and Design

8. Making a model or prototype

In the space below, document (using digital pictures) your construction of the model/prototype. Be sure to include a picture of the final model/prototype.

9. Testing and Evaluating the Design, using specifications

As you create your solution, you will perform tests to make sure that the solution is meeting the needs of the given problem. If you solution does not work, you may need to repeat the previous steps of the Engineering Design Process, until you find a functional design. In the space below, document the type of test you conducted and the results.

Test Performed

Test Results

Launched rocket

Lasted 6.55 sec

Parachute did not deploy

10.Refining the Design

Based on your tests, propse refinements to the design and construction of the design problem in the space below.

I would try to make the parachute deploy and figure out why it did not. And I might put more water in it next time the ball for the parchute had got stuck in the tube so it did not all0w itself to deploy the clay had got stuck to the paper so that it didn’t deploy

11. Creating or Making It

If time allows, modify your model/prototype as proposed in refining the design. What additional steps would be necessary to produce this solution for mass market production?

I would need plastic and be able to make the bottle non breakable and I will also need to make it safe for children so they do not get hurt. Get it to work properly and easy to use

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