INSTRUCTIONS FOR USING ROCKET

The problem of getting into orbit must be approached as an integration
of the contribution of all the stages of the vehicle.  While the
problem can be stated in simple terms of "delta V" requirements, there
are many factors which make each stage a different character in the
unfolding play.

Generally, DELTA V = LN(MASS RATIO)* ISP*G That means that the Specific
Impulse (ISP), or how much thrust you get from each pound of fuel is
very important, and the Mass Ratio, or what percentage of your vehicle
is propellant is less important.  For each stage you can set an ISP to
determine how much propellant you will use for the thrust you need.
Then set a mass ratio to determine how much metal you wish to wrap
around the propellant.  The rule of Thumb is that higher stages get the
better ISPs and Mass Ratios because they are smaller and they include
the cost of the boosters.  Boosters are the work horses, low ISP
because of atmospheric back pressure, and heavy, but you can buy them
by the pound cheap.  Also, the ISP is set mostly by the propellant
choice, the Mass Ratio on the other hand is determined by how much
money you wish to spend on light weight materials.  The lightest know
material for construction is Unobtainium.


The booster (S0) terms consist of:

Weight, for the engines and the tanks.  The weights are stated
separately because engine weight for a booster is a major term.  If you
wish, you can zero out the engine weight and lump the weight under the
tank term.

Propellant, remember to include enough to not run out.

Flow rate, the assumption here is that the engine uses fuel at a
constant rate.

Thrust, this is the sea level thrust of the booster engines or main
stage engines.

Expansion ratio thrust increase, this is the added thrust you expect to
get due to the size of the nozzle and the reduction in atmospheric
pressure with altitude.  The program automatically adds the corrected
thrust to the engine as the vehicle ascends.  Ten percent is typical.

Drag area, this is the square footage of the forward aspect of the
boosters.  A 0.5 cd nose cone is assumed.

Stop seconds, the booster if used is assumed to start at launch, you
must however tell the program when to shut down and jettison the
boosters.  The thrust, weight, and drag, are all adjusted at staging.

The main stage (S1) has the same terms, but adds a delayed start if you
want to ignite the engine at altitude.  It's not really a good idea,
but some vehicles do it so I included the option here.

The second and third stages (S2, S3) do not allow separate engine
weights.  The weight of the engine for an upper stage is a smaller
percentage of the weight.  The start and stop times can delayed to
allow the vehicle to drift between stages, but the times are cumulative
and must be defined even if the stage is not used.

The payload faring weight is included as a separate item because the
program jettisons the faring at 200,000 ft.

Payload stack drag area is the square footage of the front aspect of
the main stack.

Guidance, this is one of the areas that needs work.  Several formulas
are presented in the remarks in the program, but I'm still working on
another.  The problem is that there are lots of tricks that you can
play with the guidance program.  More updates later.

The Loft Factor is one of those tricks.  It puts a kink in the flight
path to use the booster to kick the upper stages high so that they can
work to gain orbital velocity.  It's something to play with.

Processor Delay,  If you want to slow it down put in a bigger number.

And now an example.
Booster mass ratio of 0.8, ISP 230, 100 Sec burn. 460,000# thrust,
expansion ratio thrust gain 46000#.
1. propellant flow = 460,000/230 = 2000#/sec
2. 2000#/sec * 100 sec = 200000# total propellant
3. weight = (200000#/0.8)*(1 - 0.8)=50000#
4. the drag area depends on the density of the propellant and the
finness ratio of the vehicle.  You can figure it out or just make a
good guess.  My guess 100 sqft

Main stage mass ratio of 0.8, ISP 230, 150 Sec burn, 115,000# thrust,
expansion ratio thrust gain 23000#, pad ignition.  pretty much the same
calculation.

Second stage mass ratio of 0.9, ISP 310, 300 sec burn, 24000# thrust.  ect.

No third stage.
Payload 10# to start.
Faring 1#
Payload drag 12 sqft.
Loft factor 100

The program will stop to allow you to change any of the variables that
you might have messed up, type cont when ready.  The data display
appears with the rocket weight, and the attitude display in the upper
right corner.  When you type Y, the launch begins.  Data will appear,
and a velocity direction display will appear to the right.  When the
process has reached a conclusion, crash, out of propellants, or orbit,
the program stops to allow you to change variables and start over
again.

This program does not have a plotting display.  However, I have a
simple plotting program which is either included in the .zip file or
is available on my web site.  You will need to insert the file
instructions in the program ( they're in the remarks ) and then,
without leaving qbasic, start xyplot.bas.

BASIC FOR , WELL

Sorry, I started out with basic, well actually I started out with
machine language on a Data General Nova.  You will have to find a DOS
file called gwbasic.exe, put it under an Icon in program manager.  You
can also use Qbasic.exe, but, the .bas file must be saved as an ASCII
file, and Qbasic won't stop and wait when you get to a stop point in
the program.  You can also run the programs from the c:> prompt. When
you start basic, type in "LOAD ROCKET47.BAS" if the file is in the same
directory it should load "OK".  then type "RUN".  You can also use the
function keys to operate basic, F1 = list, F2 = run, F3 = load, etc.,
they are usually labeled on the bottom of the screen.  If you type in
LLIST, basic will print out a copy of the program.  To exit the program
hit CTRL BREAK, then type SYSTEM to exit basic.  You can run basic in a
window, but it's very slow, while in basic hit ALT ENTER.


When this program was first written I ran it on a TRS Color Computer.
Processor speed was 300k, and it took 15 minutes to complete a run with
one second integration.  The program has grown somwhat since then, and
uses 0.1 second integration, it now takes a 486 the same 15 minutes to
run the program.

This program is freeware and may be freely distributed as long as the
title remarks stay intact.

Mark Goll
19785 Marbach Lane
San Antonio, Texas
78266

markgoll@wt.net
web.wt.net/~markgoll
