is a beta 1.2b 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 firstname.lastname@example.org.
Due to IT
security concerns, many users are currently experiencing problems running NASA Glenn
educational applets. There are
security settings that you can adjust that may correct
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
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
There are several different versions of the HitModeler software that are now available.
This page contains the elementary Student Version 1.2. This newest version includes
the flight of a baseball, a softball, or any ball that you describe by giving the diameter,
weight and drag coefficient. An older
Version 1.1 models only the flight of a baseball.
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:
With the downloaded version, you can run the program off-line and do not
have to be connected to the Internet.
There is a
of HitModeler that has the same functionality as the student version 1.1
but requires no keyboard. All input to this version of the program is made using
a mouse and sliders.
There is also a
of HitModeler that only considers the effects of
on a batted baseball. 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
If you experience difficulties when using the sliders to change variables,
simply click away from the slider and then back to it.
the arrows on the end of the sliders disappear, click in the areas
where the left and right arrow images should appear, and they
The program screen is divided into three main parts:
At the top of the screen is the graphics window.
The graphics window shows the
of the hit ball.
The simulation is two dimensional and you are looking parallel to the ground.
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.
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
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.
At the lower right of the screen are
input choices concerned with hitting the ball.
There is a menu to choose a baseball, softball, or input a ball design.
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. If you select baseball or softball, then the drag coefficient, weight,
and diameter of the ball are set by the program. If you select "input Ball",
you can vary the
drag coefficient, weight and diameter of the ball
by using the appropriate box and slider.
The default value of drag coefficient 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.
The NASA Glenn Educational
Programs Office will continue to improve and update HitModeler based on user input.
Changes from previous versions of the program include:
On 9 May 12,
version 1.2b was released. This version includes the softball aerodynamics
and graphics, and the ability to input the ball weight and diameter. Versions
1.2a was a development versions of the program and not released to the public.
The softball data used in the HitModeler computer program was
obtained by Peter Sherman, a high school student
from Seattle Washington, during a
shadowing session at NASA Glenn in 2012.
On 23 Oct 07,
version 1.1c was released. This version included the option to specify the
weather conditions and made some slight changes in the graphics.