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RocketModeler Version 1.2

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This is a beta 1.2 version of the RocketModeler program written by Eric Bishop from the Ohio State University. You are invited to participate in the beta testing. If you find errors in the program or would like to suggest improvements, please send an e-mail to benson@grc.nasa.gov.


This page contains an interactive Java applet to explore the various factors which affect the flight of a model rocket. All of the information presented by the applet are available within the Beginner's Guide to Model Rockets. You should start with the slide describing the parts of a model rocket.

RocketModeler

With this software you can investigate how a model rocket flies by changing the values of different design variables. If you are an experienced user of RocketModeler, you may prefer a slightly different version of RocketModeler which does not include this manual and loads a little quicker in your browser. There is newer version of the program, called RocketModeler II, which is also available. The newer program simulates a wider variety of rockets. If you experience difficulties when using the sliders to change variables, simply click away from the slider and then back to it. If the arrows on the end of the sliders disappear, click in the areas where the left and right arrow images should appear, and they should reappear.

If you see only a grey box at the top of this page, be sure that Java is enabled in your browser. If Java is enabled, and you are using the Windows XP operating system, you need to get a newer version of Java. Go to this link: http://www.java.com/en/index.jsp, try the "Download It Now" button, and then select "Yes" when the download box from Sun pops up.

SCREEN LAYOUT

The program screen is divided into two main parts:

  1. On the left of the screen is the graphics window in which you will see your rocket design and test flight. You can switch to the launch graphics by pushing the blue "Launch Rocket" button. Details are given in Graphics.
  2. On the right of the screen are the input sliders and boxes that you use to change your design or to set flight conditions. Details of the input variables are given below.

GRAPHICS

There are two main graphics displays. During the design of a model rocket you will see a drawing of the current design. As you change tube length, or fin geometry the graphic will change. On the rocket you will see two circles. The circle with the black diamonds is the location of the center of gravity (CG). The circle with the black dot is the location of the center of pressure (CP). The location of the CG and CP will change during design. For a stable rocket, keep the CP below the CG.

When the blue "Launch Rocket" is pushed on the design screen, the graphics change to display the location and orientation of your rocket during flight. Initially the rocket is sitting on the ground on its launch rail. When the red "Begin Launch" button is pushed, a countdown from T-3 sec. begins. At T= 0, the engine fires and you will see some small "flames" at the base of the rocket. The flames remain burning during the powered portion of the flight but are extinguished during the coasting ascent. If you are flying a 2 or 3 stage rocket, you will see the spent stage fall away from the stack following staging. When the ejection charge is ignited, the nose cone is discharged and a small parachute is deployed for slow descent. On the left and bottom of the graphics are some numbers which indicate the location of your rocket relative to the launch rail. The scales are in meters. When your rocket return to earth, a message appears telling you how high your rocket flew. Clicking on the blue "Design Rocket" button will return you to the design graphics.

INPUT VARIABLES

The input variables are located on the right side of the screen. During rocket design, you have two choices of input screens; Design and Materials. You can select the input screen using the buttons at the top. At the bottom of the input screen you will see numerical values of the CG, CP, and the rocket weight. By convention, input boxes have a white background and black numerals, while output boxes have a black background and green numerals. However, if your rocket is unstable, the color of the output numerals will change from green to red. If you are designing a multistage rocket, you will need to check the stability of both the launch (upper stage plus booster) and the flight (upper stage only) configurations by using the menu button at the bottom. You can also display the the CG and CP locations relative to the bottom of the rocket or the bottom of the stage by using the menu button. Pushing the blue "Launch Rocket" button changes the input variables which are displayed.

The default input screen is the Design screen. You can select a one, two, or three stage rocket for design by using the menu button at the top of the design screen. You can use the sliders and input boxes to change the length and diameter of the body tube, the length of the nose cone, and the length, width and height of the fins. You can use the selection buttons to choose either three or four fins located at equal intervals around the rocket. Most of the variables on this screen will influence the location of the CP. The "Zoom" input controls the size of the graphics. To change the value of an input variable, simply move the slider. Or click on the input box, select and replace the old value, and hit Enter to send the new value to the program.

The Materials screen is used to provide information which affects the weight and CG location of the rocket. You can select from a variety of materials for the nose and fin using the pull down menus. If you choose "Custom" materials, you must provide the density of that material in the input boxes in units of grams per cubic centimeter. On this screen, you also specify the engine to be used during your flight, and the weight of the recovery system. You can select from three parachute sizes, which will affect the terminal velocity of your descent. The drag coefficient is based on the cross sectional area of the rocket and has a default value of .7. You can enter a different value for your own rocket design. (In future versions, this number will be computed by RocketModeler based on your design.)

During Rocket Launch several buttons, text fields, and sliders appear in the input screen. The blue "Design Rocket" button returns you to design mode and resets the graphics and input screens. The red "Begin Launch" button starts the countdown for a new flight. At any time during the flight, you can push the white "Reset" button to return the rocket to the pad. Pushing the yellow "Pause" button freezes the rocket in flight so that you can record data from the flight. A purple "Resume" button is pushed to continue the flight. To the right of the buttons are output text fields showing the elapsed time of the flight, the current velocity, and the maximum altitude attained. During ascent, the maximum altitude is the current altitude. Using the sliders beneath the buttons, you are able to set the angle of the launch rail, and to set the wind speed. Positive velocity is from the right of the graphic. The "Percentage Real Time" slider allows you to control the speed of the animation. 100% is real time, and higher values cause the animation to proceed more slowly. (Because of a refresh problem in Internet Explorer, we recommend using a value greater than 400% for that browser. Otherwise the instantaneous time, velocity, and altitude outputs are not properly updated. Hitting the "Pause" button will display the correct values, however.)

Have fun!

NEW FEATURES

The Learning Technologies Project will continue to improve and update RocketModeler based on user input. The history of changes is included here:

  1. On 14 Jan 03, version 1.2 was released. This version includes the multi-stage capability and some bug fixes associated with the calculation of the engine weight.
  2. On 14 Dec 01, version 1.1 was released. This version includes controls on the speed of the animation, options for the number of fins, output of instantaneous velocity and altitude, and a countdown to launch.
  3. On 1 Jan 01, version 1.0 was released.

Button to Download a Copy of the Program


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Related Sites:
Rocket Index
Rocket Home
Exploration Systems Mission Directorate Home

 

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Editor: Tom Benson
NASA Official: Tom Benson
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