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HitModeler Student Version 1.1c


This is a beta 1.1c version of the HitModeler Student 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

HitModeler Student

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 elementary Student Version 1.1. A newer version of the program, (version 1.2), models the flight of a baseball, softball, or any ball that you describe with a diameter, drag coefficient, and weight. The motion is two dimensional and you can study the trajectory of the ball at the ballpark of your choice, and with selected weather conditions. This page contains detailed instructions on the use of the sliders and buttons in the program. For experienced users, we have a web page that contains only the software. You can download the student 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.

There is a simple version of HitModeler that has the same functionality as the student version but requires no keyboard. All input to this version of the program is made using a mouse and sliders. There is also a special version of HitModeler that only considers the effects of weather conditions on a batted ball. The ball velocity and angle are fixed and you select the weather conditions by pushing buttons. These two versions of Hitmodeler are recommended for younger students because of the simplifed inputs. There is a button on each page to download a copy of the software.


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 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. The current values of the design variables are presented to you in boxes. By convention, a white box with black numbers is an input box and you can change the value of the number. A black box with yellow numbers is an output box and the value is computed by the program. 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. 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. At any time, to return to the original default conditions, click the orange Reset button at the lower left of 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.

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.


The program screen is divided into three main 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 350 feet from home plate.
  2. At the lower left of the screen are input choices concerned with the stadium location and the weather. You can vary the stadium location and the atmospheric conditions at that location. You select the stadium location by using the choice button. The default weather conditions are an Average Day at the selected stadium. The average is based on an NASA model of the atmosphere and how the pressure and temperature change with altitude. For the average day, we have the temperature set to 59 degrees at each stadium. A Hot Day sets the temperature to 89 degrees, and a Cold Day sets the temperature to 35 degrees. You can change all of the atmospheric conditions by using the Specify option on the choice button. You can change the temperature, the atmospheric pressure, and the relative humidity of the air; the program will calculate the air density that affects the drag on the ball. At any time you can return to the default conditions by pushing the orange Reset button.
  3. At the lower right of the screen are input choices concerned with hitting the ball. To set up for a hit, you must specify the speed and the angle at which the ball leaves the bat. The angle is measured relative to vertical; 0 degrees is straight up, 90 degrees is along the ground. A small arrow on the ball in the graphics window will help you determine these values. You can also vary the drag coefficient of the ball by using the Drag - Cd box and slider. The default value is .3, which has been determined experimentally for a major league baseball at about 100 mph. By setting the value to 0.0, you can remove drag from the calculations and see the large effect that drag has on the flight of a baseball. You can also vary the strength and direction of the wind. When you have your conditions set, click on the red SWING button 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 white 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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