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HitModeler Weather Version 1.1c


This is a beta 1.1c version of the HitModeler Weather program, and 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

Due to IT security concerns, many users are currently experiencing problems running NASA Glenn educational applets. The applets are slowly being updated, but it is a lengthy process. If you are familiar with Java Runtime Environments (JRE), you may want to try downloading the applet and running it on an Integrated Development Environment (IDE) such as Netbeans or Eclipse. The following are tutorials for running Java applets on either IDE:

HitModeler Weather

With this software you can investigate how a baseball flies through the air by changing the values of the factors that affect the aerodynamic forces on the ball. These are the same forces that generate the drag of an aircraft wing. The flight trajectory is determined by the initial velocity and the relative size of the drag and weight of the ball. We provide a page of results which you can use to check your calculations.

There are several different versions of the HitModeler software that are now available. This page contains the weather version, a simplified version of HitModeler intended for younger students to learn the basics. All input to this version of the program is made using buttons. The motion is two dimensional and you can study the trajectory of the ball with selected weather conditions. This page contains instructions on the use of the buttons in the program. For experienced users, we have a web page that contains only the software. There is a more complex student version of HitModeler that has the same functionality as the weather version but you control the input to the program by using input boxes and sliders. You can download the weather version of the program to your computer by clicking on this yellow button:

Button to Download a Copy of the Program

With the downloaded version, you can run the program off-line and do not have to be connected to the Internet.


This program is designed to be interactive, so you have to work with the program. All input for this version of the program is made with buttons. To operate a button, use your mouse to move the cursor over the button, then left click on the mouse to "push" the button. The current values of variables are presented to you in boxes. A black box with cyan numbers are inputs to the program which are set by the selected buttons. A white box with black numbers is an output box and the value is computed by the program.

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:, try the "Download It Now" button, and then select "Yes" when the download box from Sun pops up.


The program screen is divided into two parts:

  1. At the top of the screen is the graphics window. The graphics window shows the trajectory of the hit ball. The simulation is two dimensional and you are looking parallel to the ground. Weight and aerodynamic drag are the only forces acting on the ball. Along the top of the window, the height and distance from the plate are updated during the flight. There is a wall set at 375 feet from home plate. The ball is launched at 100 mph at 45 dergees to the horizon.
  2. At the bottom of the screen are the values of the inputs to the program and the input buttons. The active button is shown in yellow. The default conditions are an Average Day with no wind and a default drag coefficient. The average day is based on an NASA model of the atmosphere and how the pressure and temperature change with altitude. You change the temperature, the atmospheric pressure, and the relative humidity of the air by using the appropriate button. The program then calculates the air density that affects the drag on the ball. You can set the wind at your back (+ Wind) or wind in your face (- Wind) and can change the drag coefficient to zero by using the buttons at the right. When you have your conditions set, click on the yellow SWING button at the top to launch the ball into the air. You can save your flight trajectory to compare with a new set of conditions by pushing the blue Save button. And you can clear all of the graphics by pushing the orange Clear button.

    Have fun!


Guided Tours


Button to Display Aerodynamics Index
NASA Baseball Home Page
Beginner's Guide to Aerodynamics
Beginner's Guide Home Page


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Editor: Nancy Hall
NASA Official: Nancy Hall
Last Updated: May 13 2021

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