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Glenn |
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Glenn |
This is a beta 2.1d version of the RocketModeler II program. 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. The original RocketModeler program, written by Eric Bishop, is also still available, if you prefer the older version.
RocketModeler II
With this software you can investigate how a model rocket flies by changing the values of different design variables.
There are several different versions of RocketModeler II which require different levels of experience with the package, knowledge of aerodynamics, and computer technology. This web page contains the on-line student version of the program. It includes an on-line user's manual which describes the various options available in the program and includes hyperlinks to pages in the Beginner's Guide to Model Rockets describing the math and science of model rockets. More experienced users can select a version of the program which does not include these instructions and loads faster on your computer. You can download these versions of the program to your computer by clicking on this yellow button:
With the downloaded version, you can run the program off-line and do not have to be connected to the Internet.
GENERAL INSTRUCTIONS
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.
This program is designed to be interactive, so you have to work with the program. There are a variety of choices which you must make regarding the analysis and the display of results Some of your selections are made by using a choice box. A choice box has a descriptive word displayed and an arrow at the right of the box. To make a choice, click on the arrow, hold down and drag to make your selection from the menu which is displayed. Some selection are made by using the colored buttons on the panels. To activate a button move your cursor over the button and click your mouse. By convention, blue buttons are option buttons which you can select. Most option buttons turn yellow to indicate your current selection. White buttons are processes which you must complete in order to launch your rocket. You indicate that the process is complete by pushing a white "GO" button on an input panel. The process button and the "GO" button turn green when you are successful. You must have all green buttons in "Mission Control" before you can launch your rocket. A red button demands immediate attention or "Aborts" the mission.
On each input panel, the current value of a design variable is presented to you in a text box. By convention, a white box with black numbers is an input box and you can change the value of the number. To change the value in an input box, select the box by moving the cursor into the box and clicking the mouse, then backspace over the old number, enter a new number, then hit the Enter key on your keyboard. You must hit Enter to send the new value to the program. A black box with colored numbers is an output box and the value is computed by the program. A red number indicates trouble. If the CG or CP output is red, your rocket is unstable and you must change the design. If the Weight output is red, you have insufficient thrust to lift the rocket and you must either decrease the weight or increase the thrust.
For most input variables you can also use a slider located next to the input box. Click on the slider bar, hold down and drag the slider bar to change values, or you can click on the arrows at either end of the slider. 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.
SCREEN LAYOUT
The program screen is divided into two main parts:
You move the graphic within
the view window by moving your cursor into the window, hold down the left mouse
button and drag to a new location. You can change the size of the graphic by
moving the "Zoom" widget in the same way. If you loose your picture, or want to
return to the default settings, click on the "Find" button at the bottom of the
view window. The grid behind your design is toggled on or off by using the
"Grid" button located above the Zoom widget. There are three main graphics
displays:
Input variables are located
on the right side of the screen. You first select the type of rocket by using
the blue buttons at the top of the screen:
During rocket Design,
you have four choices of input panels; Nose, Payload, Body,
and Fins. You select the input panel by using the blue buttons located
above the graphics window on the left. On each input panel, you select the
material for the part being designed by using the choice button at the top of
the panel. The density of the material is shown to the left of the choice button
and is used in computation of the weight of the part. The weight of the part
affects the location of the center of gravity and the stability of the rocket.
There are input sliders and boxes on each panel which change the geometry of
each part:
After the rocket is designed, you use the Fuel input panel to specify
the propulsion system inputs. The type of input panel depends on the type of
rocket. A Ballistic object has no fuel, so the input panel is the same as
the design panel. A Stomp rocket has a reservoir with a beginning and
ending volume that can be used to compute the
pressure in the reservoir. You can choose to input the pressure by using the
choice button on the input panel. The reservoir pressure and length of
the launch tube determines the launch velocity. A 2-L Bottle rocket is
filled to some level with water and then pumped to some launching pressure
before launch. You select the volume of water, the pump pressure,
and the length of the launch tube and the program computes the
weight of the water and the lift off (LO) thrust. You must have lift off
thrust greater than weight in order to launch. For the Model rocket,
small solid rocket engines are inserted in the rocket. The thrust and weight
characteristics of these engines are described on a separate
page. With model rockets, you can also choose a two-stage or clustered
configuration of multiple engines. When you finish fueling you click "GO" and
proceed to the launch "Pad". On the launch Pad input panel you specify the flight conditions for
your rocket. The default location of your launch pad is on the Earth at sea
level. You may also launch from an "ideal" Earth, where there is gravity but no
drag, or from the Moon, where there is no drag and 1/6th of the Earth's gravity,
or from Mars, where there is reduced drag and roughly 1/3rd of the Earth's
gravity. You may change the altitude of the launch pad and the wind conditions
on Earth or Mars. You may choose to model the effects of weather
cocking on the launch by using the choice box on the input panel. And
finally, you select the angle from the vertical and the length of
the launch rail. When you finish selecting your flight conditions click "GO" and
proceed to "Launch" control. On the "Launch Control" input panel you have a white button to Fire
the rocket. As the countdown begins, the button turns yellow, then green during
the flight, and finally red after touchdown. During the flight, the time and
telemetry information changes. You can interrupt the flight by pushing the blue
"Pause" button. You can then proceed a time step at a time by pushing the white
"Step" button, or resume the flight by pushing "Resume". When your flight is
finished, you can "Reset" the same flight conditions and shoot again, or you can
re-fuel or change flight conditions. At any time you can "Abort" the mission. At
the bottom of the "Launch Control" panel, the current and maximum values of the
height, speed, and range (distance from the launch pad) are displayed. The
current value of thrust, weight, and drag o are
also displayed.
Have fun!
NEW FEATURES
The Educational Programs Office will continue to improve and update RocketModeler based on user input. The history of changes is included here: