SCREEN
LAYOUT
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 this panel. The selected mode
is indicated by a yellow button. Depending on your choice, different
input panels appear at the top. 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" button, 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 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.
GRAPHICS
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 unstable a red and yellow banner appears
over the graphics. You should then change either a Shape input
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.
- Front shows
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.
Surfaces are shown as white areas, while the frame is shown as
black lines. The 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 bottom.
- Side shows
the kite as viewed looking along the surface. This view is the
default during the Trim phase of your kite.
The wind is blowing over the kite from left to right and the
magnitude 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.
The bridle of the kite is given by the white line
below the kite surface. The bridle length (B) is set on the trim
input panel. The control line 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. The lift, drag, and weight 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.
- Field shows
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
line sags 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
Output variables
are displayed at the bottom right of the program screen. In most cases,
these output variables are calculated by the computer program using
mathematical equations.
If the "Design" or "Trim" mode is chosen, the following variables are
displayed. The Weight 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. The aerodynamic Lift and
Drag are computed by the program and displayed in ounces or
gram-weights. The Tension 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. The 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. The Surface Area
of all the material and the length of all the components of the
Frame 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. The trimmed Angle
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
Torque 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. The
Range-X 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. The Height-Y
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.
The atmospheric pressure 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. The atmospheric
temperature is also displayed in degrees Fahrenheit (F) or
Celsius (C).
INPUT VARIABLES
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
basic designs. 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, Tail, and control Line
by using the drop menu at the far right of each part. Each
material has a characteristic "density" 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 also change the size of your kite by
using the Max Dimension input. This value is used for the
maximum value on the height, width, and bridle sliders and input
boxes on the "Shape" panel.
- In the "Trim" mode, the default input panel is the
Trim panel. On the Trim panel you can select to have the
program compute 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 angle 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
Bridle and Knot 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 atmospheric
model. You can set the Wind speed in
feet or meters per second and the length of the control
Line 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.
NEW FEATURES
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
a new variable to set the maximum size of the kite. This allows the user
to design very large, or very small kites. We have also re-arranged the
input panels and changed the colors on some buttons to be more
consistent with other simulators at the Beginner's Guide to
Aeronautics.
- On 14 May 12, version 1.4c was released. This version includes
some small 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
added.
- 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.
- On 28 Mar 02, version 1.1 was released.
Enjoy!