Contents of the LAUNCHER.DOC file
August 25, 1987
A single stage to orbit launch vehicle simulator. Written by
Robert Castle, CIS 70330,605. The source code for launcher
(written in Quickbasic) is available for a $20 charge from
306 Lost Rock Dr.
Webster Tx. 77598
This software is for the enjoyment and hopefully the
enlightenment of the user. No warranty of any kind is expressed
Getting Started Quickly
The launcher program is written for the IBM PC or compatible. A
CGA card or equivalent is required.
The program is started by simply typing "launcher" at the DOS
You will be prompted for your name and the name of your next of
kin. Any answer here will do.
You will then be asked if you have EGA capability. If you do hit
the "Y" key. If you don't hit any other key.
You will be presented with a vehicle selection menu. Since no
single stage to orbit vehicle currently exists I made up some
reasonable numbers. There are 2 already defined launchers and a
third "make up your own". I suggest you start with the
"advanced" launcher for your first several tries.
Use the arrow keys to position the arrow on the screen to the
vehicle of your choice and hit enter.
You will get a brief page of explanation. After reading it press
enter and you will start the simulator. You have control over
only 2 (but critically important) flight control parameters: the
pitch angle of the vehicle and the throttle.
This is the angle of the vehicle relative to the surface of the
earth. An angle of 0 is "level" and an angle of 90 is straight
up. The up and down arrows change this angle by 5 degrees. The
page up and Page down keys change the angle by 1 degree.
The throttle has only limited control. The HOME key gives you
full throttle, the left arrow key gives you 65% of Full and the
End key shuts down the engines. You can go from 65% to Full and
back as many times as you like but after a SHUTDOWN you can only
go to the ORBIT throttle setting (by pressing HOME). This
throttle setting is designed for Orbit adjust maneuvers. ie do
not shut down until you are in orbit or very close to it. The
throttle will automatically limit itself to keep the "G" level on
the vehicle below limits (usually 3 Gs).
The object (other than learning a "feel" for orbital mechanics)
is to get into a 250 nmile circular orbit to rendezvous with a
space station. The program will display how well you did if:
1. you run out of fuel
2. you press escape
DESCRITPION OF DISPLAY AND MORE DETAIL
The number display looks like this
Alt= xxxxx Vel= xxxxx
Throt= xxxxx Gs= xxxxxx
Ang= xxxxx Vh= xxxxx
FPA= xxxxx Qbar= xxxx
Ha= xxxxx Hp= xxxx
Alt= Current altitude, in feet if altitude less than 1 nautical
mile, in nautical miles otherwise.
Vel= Current velocity in feet per second. This is the inertial
velocity (in this model the earths rotation is NOT modelled).
Throt= The throttle setting in percent.
Gs= The G level or acceleration level being felt by the
occupants of the vehicle (that is YOU).
Ang= The pitch angle of the vehicle in degrees. This is
relative to the surface of the earth and not inertial.
Vh = The horizontal component of velocity. This is the same as
plotted. In feet per second.
FPA = This is the Flight Path angle of the vehicle in degrees.
This is the angle of your travel relative to horizontal. If the
angle is positive you are climbing toward apogee (your highest
point). If it is negative you are falling toward perigee. Note
this is NOT the same as the pitch angle. That indicates the
direction at which you are THRUSTING. FPA indicates the
direction you are actually going in.
Qbar= This is the aerodynamic pressure on your vehicle. You may
have heard of MAX Q or Maximun aerodynamic pressure mentioned
with regard to space launches. The Qbar is one half the velocity
squared times the atmospheris density. As you velocity goes up
the Qbar will go up but as you climb the atmospheric density goes
down so the Qbar goes down. Qbar is thus only a problem at low
altitudes and high speeds. Keeping the Qbar down is the only
reason to throttle down to 65%.
Ha and Hp. The apogee and perigee altitudes in nautical miles.
These will constantly change as you are thrusting. While you are
climbing into orbit you should think of these as the apogee and
perigee altitudes that would result if you stoped thrusting NOW.
These are the primary things your are trying to target. To be
perfect you should get them both to 250 (the target orbit).
The Apogee is plotted against the horizontal velocity. The
apogee is the main thing you are trying to target.
ANGLE to APOGEE
A "clock face" is drawn that shows the angle to apogee. This is
required so you can tell where you are in the orbit. You are at
the "tic mark" at the 12 o'clock point and the hand points to the
apogee or highest point of your orbit. Note that during the
climb into orbit the apogee may move quickly. This does not mean
you have moved around you orbit that quickly but that you have
changed the shape of the orbit by applying thrust.
1. Slowly decrease the pitch angle at first. WATCH YOUR QBAR.
Go to 65% throttle only to keep from violating the Qbar limit. Go
back to Full as soon as you can.
2. Watch the plot. You want to hit a 250 nmile apogee at orbital
velocity (about 25000 fps).
3. Watch the angle to apogee and the FPA. You want to keep
apogee in front of you. Bring the pitch angle down to almost
zero after a couple of minutes.
4. Shut down with both apogee and perigee low and use orbit
thrust to tweak them up. F9 will run the simulation at 10 times
5. Remember orbit burns at perigee affect the apogee altitude
and vice versa. To increase altitude burn posigrade (pitch of 0),
to decrease altitude burn retrograde (pitch of 180).
6. Don't be afraid to use negative pitch angles late in the
climb into orbit. This can "push the apogee" around ahead of you
and keep from it getting to high.