This
is a beta 2.1f version of the RocketModeler II program. 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 benson@grc.nasa.gov.
The original
RocketModeler program, written by Eric Bishop, is
also still available, if you prefer the older version.
RocketModeler II
With this software
you can investigate how a rocket flies
by changing the values of different design variables.
There are several different versions of RocketModeler II which
require different levels of experience with the package,
knowledge of aerodynamics, and computer technology.
This web page contains the on-line student version of the program.
It includes an on-line user's manual which describes the
various options available in the program and includes hyperlinks to
pages in the
Beginner's Guide to Rockets
describing the math and science of rockets.
More experienced users can select a
version of the program which does not include
these instructions and loads faster on your computer.
You can download these versions 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.
GENERAL INSTRUCTIONS
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 may need to get a newer version of Java. Go to this link:
http://www.java.com/en/index.jsp,
try the "Download It Now" button, and then select "Yes" when the download box from Sun
pops up.
This program is designed to be interactive, so you have to work with the program.
There are several different types of input "widgets" which you use to send
information to the program to change the analysis and display results:
Some of your selections are made 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 from the menu which is displayed.
Some selection are made by using the buttons on the panels. To
activate a button move your cursor over the button and click your mouse. The different
colored buttons have different effects:
Blue buttons are option buttons which you can select.
Most option buttons turn Yellow to indicate your current selection.
White buttons are processes which you must complete in order to launch your rocket.
You indicate that the process is complete
by pushing a white "GO" button on an input panel. The process button
and the "GO" button turn Green when you are successful. You must have all green
buttons in "Mission Control" before you can launch your rocket.
Red buttons demand immediate attention or "Aborts" the mission.
On each input panel,
the current value of a design variable is presented to you in a text box.
Different colored boxes have different meanings:
A white box with black numbers is
an input box and you can change the value of the number.
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.
A black box with colored numbers is an output box
and the value is computed by the program. Red numbers indicate trouble.
If the CG or CP output is red, your rocket is
unstable and you must change the design. If the Weight output is red, you have
insufficient thrust to lift the rocket and you must either decrease the weight
or increase the thrust.
For most input variables you can also use a slider,
located next to the input box, to change the input value. To operate
the slider, click on the slider bar,
hold down and drag the slider bar, or
you can click on the arrows at either end of the slider.
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.
SCREEN LAYOUT
The program screen
is divided into two main parts:
On the left
of the screen is the graphics window in which you will see your rocket
design, the test flight, and output data.
Details are given in Graphics.
On the right
of the screen are the input sliders and boxes that you use to change
your design or to set flight conditions. Details of the
Input Variables
are given below.
GRAPHICS
You move the graphic within the view window by moving your cursor into the
window, hold down the left mouse button and drag to a new location.
You can change the size of the graphic by moving the "Zoom" widget in the same way.
If you loose your picture, or want to return to the default settings, click on the
"Find" button at the bottom of the view window. The grid behind your design is toggled on or
off by using the "Grid" button located above the Zoom widget.
There are three main graphics displays:
During the "Design" and "Fuel" processes you see the
design graphics. As you change any input variable, like the tube length or fin geometry,
the graphic changes. There are two colored circles on the rocket. The yellow circle
is the location of the center of gravity (CG).
The black circle is the location of
the center of pressure (CP). The location of
the CG and CP change during design and fueling. For a stable
rocket, keep the CP below the CG. When the white "Fuel" button is pushed,
the graphic includes some information about the propulsion system of
your rocket. The form of the graphic depends on the type of rocket.
During the "Pad" and "Launch" processes the
graphic changes to display the flight graphics.
The location and orientation of the rocket is displayed during flight, although the
rocket is not drawn to scale with the grid and surroundings.
After a successful flight you can save the flight trajectory by clicking the "Save" button
below the zoom widget. You can save 5 flights for comparisons. During the flight you have
two viewing options. The default is the "Tracking Mode" option which keeps the rocket
centered in the view window during the flight. The zoom widget is disabled during
tracking mode. The other viewing option keeps the view fixed on the ground. The
"Find" button takes you to the launch pad. Use the zoom widget and the graphic
movement to
examine the entire flight trajectory with this option. Viewing options
are toggled using the "Track" button located below the graphics window.
The blue "Data" button on the "Launch" input panel
displays output graphics in the view window.
Data is displayed as "strip charts" of
thrust,
weight,
drag,
velocity, and
height.
Depending on the rocket type, some of these variables
do not change. The horizontal grid increments are 1 second on the strip charts.
You return to the flight mode graphics
by clicking the "View" button on the "Launch" input panel.
INPUT
VARIABLES
Input variables are located on the right side of the screen. You first select the type of
rocket by using the blue buttons at the top of the screen:
A Ballistic projectile is an object which has no propulsion system and
is shot into the air at some initial velocity. Gravity eventually brings the
object back to the surface. Ballistic objects have only one input panel which is located
at the lower right. You can select several different types of objects by using the
choice box at the upper right of the input panel. A representative
weight, cross-sectional
area, and
drag coefficient (CD)
are then loaded onto the input panel. You can reset these values as described above.
The launch speed must also be specified before launch.
You then click "GO" to complete the design and move to the launch pad.
An Air rocket is a special case of a ballistic projectile. The weight of
the compressed air rocket is determined by your design and a check is made
for rocket stability. The fuel for the air rocket
is compressed air. You
increase
the pressure of the air by using a pump. The program computes the launch speed
based on an integration of Newton's
second law. The launch speed depends on the length
of the launch tube.
A Water rocket uses a standard 2-Liter plastic bottle for the
body of the rocket. You design the other parts of the rocket, including
the nose cone and fins. The fuel for the water rocket is water which is
pressurized by an air pump.
You specify the amount of water, the air pressure, the diameter of the nozzle and
the length of the launch tube. Because water is forced out of the nozzle under
pressure, the weight of the rocket changes during the flight.
The Solid rocket is powered by a
solid rocket engine that you purchase from a hobby store.
You design the shape of the rocket and the program checks for stability.
You fuel the rocket by selecting the number and type of rocket engine.
The thrust
characteristics
of many types of engines are modeled in the program.
During rocket Design, you have
four choices of input panels; Nose, Payload, Body, and Fins. You
select the input panel by using the blue buttons located above the graphics window on the left.
On each input panel, you select the material for the part being designed by using the choice
button at the top of the panel. The density of the material is shown to the left
of the choice button and
is used in computation of the weight of the part. The weight of the part
affects the location of the center of gravity and the stability of the rocket.
There are input sliders and boxes on each panel which change the geometry of each part:
On the Nose panel, you can select the shape by using the choice box
at the top. For each shape, you can change the vertical length of the
nose and the base diameter of the nose. The program calculates the
area and
volume of the nose which is then used in the
weight calculation.
At the bottom of the Nose input panel, you can select the type of
recovery system by using the choice box and you can add ballast weight
to the nose to keep CG above CP.
When you finish the nose design you can select another part by using
the blue buttons, or you can click "GO" to complete the design.
The Payload panel is used to design the section between the nose and
the body of the rocket. As before, you can vary the length and the
diameter of the payload tube. As the payload diameter is varied, the nose
diameter is also changed, and the area, volume, and weight of the payload
is calculated. On most rockets there is a fairing or transition section
between the payload and the body tube. You can vary the length and material
of the fairing.
When you finish the payload design you can select another part by using
the blue buttons, or you can click "GO" to complete the design.
The Body panel is used to size the body tube of the rocket. You
can specify the length and diameter of the tube for the
air rocket and the solid rocket. For the solid rocket, the program insures
that the tube diameter is large enough to hold the engine. For all types
of rockets you can add a fairing to the bottom of the rocket. The exit diameter
of the fairing is the nozzle diameter. A fairing reduces the amount of base
drag of your rocket.
On the Body panel you must specify the
drag coefficient
of the rocket. (In future versions of the program, the drag coefficient will be
calculated. For now, you must input a value.)
When you finish the body tube design you can select another part by using
the blue buttons, or you can click "GO" to complete the design.
The Fins panel is used to design the shape and number of stability fins.
You can choose a trapezoidal or an elliptical class of geometry.
Rectangles, squares, rhombuses, and triangles are included in the trapezoidal
class; circles are a special case of the elliptical class. You specify the
location of the fins along the body tube as measured from the
bottom of the rocket. You also specify the length of the
fin root along the tube, and the width of the fin from the surface
of the tube. For the trapezoidal class, you can specify the leading edge
(L.E.) angle and the trailing edge (T.E.) angle as measured from
the horizontal.
When you finish the fin design you can select another part by using
the blue buttons, or you can click "GO" to complete the design.
After the rocket is designed, you use the Fuel input panel to
specify the propulsion system inputs. The type of input panel
depends on the type of rocket. A Ballistic object has no fuel,
so the input panel is the same as the design panel.
An Air rocket has a pump with a beginning and ending volume
that can be used to
compute
the pressure in the rocket. You can choose to input the pressure by
using the choice button on the input panel. The pump pressure and
length of the launch tube
determines the launch velocity.
A Water rocket is filled to some level with water and then
pumped to some launching pressure before launch.
You select the volume of water, the pump pressure, and the
length of the launch tube and the program computes the weight
of the water and the lift off (LO) thrust.
You must have lift off
thrust greater than weight in order to launch. For the Solid
rocket, small solid rocket engines are inserted in the rocket. The thrust
and weight characteristics of these engines are described on a
separate page.
With solid rockets, you can also choose a two-stage or clustered configuration
of multiple engines.
When you finish fueling you click "GO" and proceed to the launch "Pad".
On the launch Pad input panel you specify the flight conditions
for your rocket.
The default location of your launch pad is on the Earth at sea level.
You may also launch from an "ideal" Earth, where there is gravity but
no drag, or from the Moon, where there is no drag and 1/6th of the Earth's
gravity, or from Mars, where there is reduced drag and roughly 1/3rd of the
Earth's gravity. You may change the altitude of the launch pad
and the wind conditions on Earth or Mars.
You may choose to model the effects of
weather cocking
on the launch by using the choice box on the input panel.
And finally, you select the angle from the vertical and the length of
the launch rail.
When you finish selecting your flight conditions click "GO" and
proceed to "Launch" control.
On the Launch input panel you have a white button to "Fire"
the rocket. As the countdown begins, the button turns yellow, then
green during the flight, and finally red after touchdown. During the
flight, the time and telemetry information changes. You can interrupt
the flight by pushing the blue "Pause" button. You can then proceed
a time step at a time by pushing the white "Step" button, or resume the
flight by pushing "Resume". When your flight is finished, you can "Reset"
the same flight conditions and shoot again, or you can re-fuel
or change flight conditions. At any time you can "Abort" the mission.
At the bottom of the "Launch Control" panel, the current and maximum values
of the height, speed, and range (distance from the launch pad) are displayed.
The current value of
thrust,
weight, and
drag
are also displayed.
If a Water rocket is being launched, the instantaneous
pressure and fuel weight inside the bottle are also displayed.
Have fun!
NEW FEATURES
We will continue to improve and update RocketModeler II based on your
input. The history of changes is included here:
On 26 Sep 05,
version 2.1f was released. This version was re-sized to better
fit the default size of the NASA Portal.
On 9 Sep 05,
RocketModeler II was moved from its old location on the NASA Glenn
LTP web site to its present location in the Exploration Systems Mission
Directorate Education site.
On 25 May 05,
version 2.1e was released. This version included some bug-fixes involved
with the integration of the equations of motion and with the thrust
calculation for the water rocket.
On 10 May 05,
this "User's Manual" page was modified to support the NASA Portal.
On 9 Dec 04,
version 2.1d was released. This version includes a recovery system
for the Water Rocket and a change in the grid for flights from the
Moon and Mars.
On 22 Nov 04,
version 2.1c was released. This version allows flights from
the Earth, Moon, and Mars. Some cosmetic changes in button location and
function are also included.
On 25 Oct 04,
version 2.1b was released. This version is a "clean-up" of Version 1.1a
and moves the component design buttons over to the view window.
The version number was changed to avoid some confusion with the
previous RocketModeler program.
On 8 Oct 04,
version 1.1a of RocketModeler II was released.
This version includes ballistic shells, air rockets and water rockets
as well as solid model rockets.
The input panels have been redesigned with more and different material
properties. This version supports either English or metric units.
This version also support strip chart output for flight conditions and
models weather cocking.
On 14 Jan 03,
version 1.2 was released. This version includes the multi-stage capability and
some bug fixes associated with the calculation of the engine weight.
On 14 Dec 01,
version 1.1 was released. This version includes controls on the speed of the animation,
options for the number of fins, output of instantaneous velocity and altitude, and a
countdown to launch.
On 1 Jan 01,
version 1.0 of RocketModeler was released.
