THERMCAS.EXE  (DOS Executable program)						Version 1.00 (1-00)
Motor Casing Thermal Analysis for Amateur Rockets						by R.A.Nakka
					
						
The purpose of the THERMCAS program is to calculate the temperature distribution through the thickness						
of a rocket motor casing wall. The casing may be insulated or non-insulated, as specified by the user.						
The analysis technique utilized by this program is similar to the Schmidt method, detailed in Rocket Propulsion						
Elements (G.Sutton), 4th ed.						

Heating of the casing wall occurs during combustion and is primarily due to convective heat transfer.						
The program requires as part of the input various properties associated with the combustion and flow						
process. Specifically, the convection coefficient may be calculated using THERMCAS.XLS for input into	
the THERMCAS program.	

Thermal properties of the material used for both the casing and the insulation are required as input data.	
These properties are provided in THERMCAS.XLS for some of the more common materials that may	
be used for this purpose.	

Output of the THERMCAS program is in the form of a text file (THERM.OUT), in the form of a matrix	
indicating the temperature at 11 "nodes" through the thickness of the casing wall. Since the heating	
process is a transient one, this temperature profile is given at various time increments, based upon	
the total analysis time duration specified by the user. For convenience and for visual aid in interpreting	
the output, the contents of the output file may be easily plotted in THERMCAS.XLS. This is accomplished	
by opening the output file in EXCEL and performing a simple "copy and paste" of the output data into	
the specifed range of cells.	

Important notes:	

1) When using THERMCAS to calculate wall temperatures in a material with a low thermal conductivity, 
and a thick wall, the program may not run successfully. The reason is that the temperature gradient
through the full wall thickness is very large. This problem can be overcome by specifying a reduced
thickness. For example, if the material is PVC with a wall thickness of 7 mm, try using a value of
2 mm for the material thickness. If required, the temperature in the remaining thickness can be
estimated by extrapolation.

2) The thickness of the insulation, specified by the user, is "idealized" by the program, and may not match
exactly the specified value. This is due to the process whereby the material is divided into finite
thickness "slabs" by the analysis routine, the number of which is rounded to the nearest integer.
For reference, the idealized thickness is printed to the screen during execution of the program.

3) Generally, this program was written to cater to short burn times. However, longer duration analyses
may be performed by running the program more than once, using a sequence of shorter duration steps.
To facilitate this, the user is allowed to specify the starting time associated with each analysis step, as
well as the initial temperature of the casing. For example,  an analysis totalling 5 seconds may be 
accomplished by running THERMCAS five times, each of 1 second duration. After each run, the wall
temperature of the previous run is input as the initial wall temperature.
