is a beta 1.5a version of the KiteModeler 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 Thomas.J.Benson@nasa.gov.
With this software you can study the physics and math which describe the
flight of a
You can choose from several types of kites and change the shape, size, and materials
to produce your own design.
You can change the values of different variables which affect the design
and immediately see the new
With this version of the program, you can even test how your kite
would fly on Mars, or off the top of a mountain.
The program tells you if your design is
or not and
also computes a prediction of how
your kite will fly.
If you are an experienced user, you can use
of KiteModeler which does not include this tutorial.
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.
To return to the
original default conditions, click the Set button on the view window
to the left.
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 three main parts:
On the left
of the screen is a graphics window
in which you can display a drawing of the kite you
are designing, trimming, or flying. Details
are given in GRAPHICS.
On the right
of the screen at the bottom is the control and output panel.
You can select the "Design", "Trim","Fly", or "Output" mode by clicking on the
buttons at the top of the panel.
The selected mode is indicated by a yellow button.
Depending on your choice, different input panels appear at the
top of the program and different output variables are shown at the bottom.
Output boxes are shown with a black background, input boxes with
a white background.
Details of the INPUT
and OUTPUT variables are given below.
If you click the "Output", a large text window
is displayed at the upper right. Output can be saved to this window by
using the Print
button on the view window at the lower left.
On the right
of the screen at the top are the input panels.
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.
Some input panels contain menu buttons. To operate a menu button,
click on the arrow to the
right and make your selection from the drop menu.
The View window for the kite is shown on the left of the program screen.
You can change the size of the image by using the slider at the far left. Just
click and drag on the black bar to make the image larger or smaller.
If your kite design or trim is,
a red and yellow banner appears
over the graphics. You should then change either a
or a Trim input until the banner disappears.
You can perform the calculations in either Imperial (English) units or Metric units
by clicking on the button in the upper left of the view window. Imperial
units are the default.
You can move the kite within the view window by moving your cursor into the window,
holding down the left mouse button, and dragging the kite to a new location. If you
lose the kite, click on the Find button above the slider.
There are three views available to the user; Front, Side, and Field, as
indicated by the buttons at the top of the window.
The selected button is indicated by a yellow background.
By default, the Front view is shown in Design Mode, the Side view
in Trim Mode, and the Field view in Fly Mode.
However, you can override the default by using the "Select View->" button.
Click on this button, then click on the desired view. You can use any view
at any time in the design, trim, and flight sequence as long as the "Select View->" button
is yellow. To return to the default views, just click on the "Select View->" button again.
the kite as viewed looking perpendicular to the surface. This view is
the default during the "Design" of your kite. The geometric input
parameters are shown to the right and below the kite drawing.
are shown as white areas, while the frame is shown as black lines.
center of gravity
is shown as a red dot and the
center of pressure
as a green dot. The tail of the kite is given as a green line at the
the kite as viewed looking along the surface. This view is
the default during the
phase of your kite.
The wind is blowing
over the kite from left to right and the
of the wind is
shown by a small green arrow at the bottom.
The kite surface is again shown as a white area, and the tail as a cyan
line at the right. The length of the tail (T) is set on the trim input panel.
The kite surface is inclined to the horizontal at the
angle of attack
of the kite.
of the kite is given by the white line below
the kite surface. The bridle length (B) is set on the Trim input panel.
is shown by a magenta line from the lower left.
The control line is attached to the bridle at the
bridle point (knot)
shown as a white dot. The distance of the knot from the base of the
kite is denoted by (K) and is shown as a yellow line below the bridle.
This distance is also set on the trim input panel.
This drawing changes as you trim the kite by changing the length of the
bridle or the location of the knot.
forces that are acting on the kite
during flight are displayed as vectors (arrows) with the lengths
proportional to one another. You can change the length of all the force
vectors by using the "Scale" slider at the bottom of the window.
the kite flying with the control line running from you to the kite. This view is
recommended during the "Flight" phase of your kite.
As before, the wind blows from left to right over the kite.
A white line shows the length and shape of the control line. (Notice that the
under its own weight and may even touch the ground.) The kite flies
at some distance "X" from your feet and at some height "Y" above the ground.
The values of these variables are shown on the output panel.
If you let out line, the kite may leave the view window. You can change the
size of the display by using the "Scale" slide at the bottom.
Output variables are displayed at the top right of the program screen.
In most cases, these output variables are calculated by the computer program
using mathematical equations. We have created hyperlinks to other web pages
which describe the exact equations used in this program. Just click on the variable
listed below to view these equations.
If the "Design" or "Trim" mode is chosen, the following variables are displayed.
of the kite is calculated based on the input geometry and
the materials selected. The weight is displayed in ounces or gram-weights and
does not include the weight of the control line.
are computed by the program and displayed in ounces or gram-weights.
in the line is displayed in ounces or grams. This is computed based on the
forces on the kite and the weight of the line.
Center of Gravity (Cg) and
Center of Pressure (Cp)
are the average location of the weight and aerodynamics forces, respectively.
They are computed by the program in inches or centimeters from the bottom of the kite
as shown in the "Front" view.
of all the material and the length of all the components of the
needed to make your kite
are computed based on your geometric input and the type of kite selected.
These values are used in the computation of the weight and Cg.
of attack is displayed in degrees and
may be either input by the user or calculated by the program.
If the value is calculated by the program, the output numerals are
green and the value is calculated to eliminate any torque on the kite.
If the value is input, the output numerals are yellow
to warn the user that the resulting flight conditions may be unstable.
The program calculates the net
on the kite about the bridle point. In stable flight the value is zero (in this
program it is computed to a very small but non-zero number).
The units for torque are ounces-inch.
Using the "Side" view of the kite, a positive torque is clockwise and a
negative torque is counter-clockwise about the bridle point.
If the "Fly" mode is selected, four additional variables are displayed.
is the horizontal distance of the kite from your location during
flight. This value is related to the Height-Y and is also displayed on
the "Field" view.
is the predicted altitude at which your kite flies. This value depends
on the flight characteristics of the kite, the wind velocity, the atmospheric
conditions, and the
amount of control line that you use. The value is computed in feet or meters and
is shown on the "Field" view.
is displayed in pounds per square inch (psi) or or kilo-Pascals (kPa) and
depends on the altitude and planet chosen on the input panel.
is also displayed in degrees Fahrenheit (F) or Celsius (C).
Input variables are displayed on input panels at the upper right of the screen.
There are four sets of input variables which depend on the program mode.
In the "Design" mode, the default input panel is the Shape panel.
On the Shape panel you first select the type of kite to be designed
by using the drop menu at the upper right. You can choose from five
Depending on the design, you then vary the height,
H1 and H2,
and width parameters,
W1 and W2,
to alter the shape of your kite.
The "Front" view shows the meaning of these variables and also indicates if your
design is unstable.
There are default geometries for each kite based on the width W1. If you
change the type of kite, you will get the new kite default with the current
value of W1 held constant. Pushing the Reset button on the view panel
will return the default geometry with W1 = 10 inches.
In the "Design" mode, you can also change the material properties of all
of the parts of your kite. Push the white
"Material" button to display the
Material input panel.
On the Material panel you change the material used for the Surfaces, Frame,
and control Line by using the drop menu at the far right of each part.
Each material has a characteristic
which is displayed in the black output
box. This density is used to compute the weight and Cg of your kite and the
sag of the control line. For each part you
can Specify your own material density by making this selection on the drop
menu. The black output box then becomes a white input box and you can enter your own
data as described above.
You can use the Max Dimension input box to change the size of your kite. The
max dimension is used on the height, width, and bridle input sliders and boxes.
You can use this parameter to design very large or very small kites.
In the "Trim" mode, the default input panel is the Trim panel.
On the Trim panel you can select to have the program
the trimmed angle
of attack or your can input your own flight angle of attack
by using the
drop menu at the upper right. If you decide to input your angle of attack,
you then input the
in degrees. The "Side" view shows the inclination
of your kite relative to the wind. The most important variables used to trim
your kite are the
variables. Bridle gives the
total length of the bridle string in inches or centimeters. Knot gives the length along the
bridle string from the base of the kite to the attachment of the control line.
These two variables affect the trim angle of the kite which affects the magnitude
of the aerodynamic forces. Because the kite pivots about the knot in flight, the
location of the knot has a large effect on the stability of the kite.
The length of the Tail also affects stability and trim by shifting the Cg.
In the "Fly" mode, you may choose to fly your kite on
Earth or on Mars by using the menu button at the right.
The gravitational constant on Mars is different than the earth, so you
will notice that the weight of your kite changes. (The material densities
and payload weight are still based on "earth" values).
You can set the altitude in feet or meters which changes the
atmospheric pressure and temperature using an
You can set the
speed in feet or meters per second and the
length of the control
in feet or meters. The weight of the control line is
calculated and causes the line to sag as shown in the "Field" view. Eventually
a point is reached where the line touches the ground at your feet. The program
then ignores any additional line input that you make.
You can also attach a payload to your kite at the center of gravity using
the input box and slider at the bottom of the panel.
The Educational Programs Office will continue to improve and update KiteModeler
based on user input. Changes from previous versions of the program include:
On 28 Aug 12, version 1.5a was released. This version includes
the max dimension variable on the Materials input panel. This allows for
the design of very large kites, as requested by users of the program. We
have also re-arranged the input panels and the color of some buttons to
be consistent with other simulators at the Beginner's Guide to Aeronautics.
On 14 May 12, version 1.4c was released. This version includes
some minor fixups on the displays and labels.
On 3 Nov 04, version 1.4b was released. This version includes
the "Tumbleweed" kite design which was requested by NASA Langley in
support of a study of a passive Mars rover design. The layout of the
program was modified and the planet, altitude, and payload inputs were
On 25 Sep 03, version 1.3b was released. This version includes
the "Twin Trap" kite design which was requested for a NASA Connect
broadcast concerning the Centennial of Flight.
On 1 Oct 02, version 1.3 was released. This version includes
the output text field at the bottom of the program, the default geometries
for all the kites, the Reset feature, the line tension output,
and a fixed bug in the line weight.
On 29 July 02, version 1.2 was released. This version includes
English and Metric units and the Twin-Trap kite geometry.