PROFILER Documentation v0.0 95-08-21

Program profiler computes the CP and the centroid of the plan area of a rocket using the Barrowman equations. As a special bonus, if you own gnuplot, profiler dumps data for gnuplot to draw a pretty plan area of your rocket.

A rocket lends itself handily to the cylindrical coordinate system so just for clarification, in the following doc, Z values are length measurements and R values are radial measurements.

This program is a little different in it's approach to fin data entry. All you do is enter the (Z,R) coords of the vertices on the fins, and profiler figures the Cr, Ct, Xb, S and Lf for you. The other lengths and diameters are entered as usual.

How to Enter Rockets of Your Own

What is a fin can? Well, I don't know about the real definition but as far as profiler is concerned, the fincan is the segment of body tube under the fins. The value is entered in Lf ( see file .pro ) and is usually the distance from the leading edge of the fin to the end of the rocket. Any units of length can be entered -- just be sure to use the same units for all measurements.

Get your ruler. Measure the length & diameter of the nose. Enter the data in Ln and Dn respectively.
Measure the Length & Diameter of the Body Tube and enter the data next to Lb and Db. Be sure to subtract the fincan length from the Lb! ( That usually means to measure the BT from the end of the nose to the leading edge of a fin. Alternatively, you can leave out the BT and make the whole rocket a Nose and a Fin Can ;-)
Not implemented in WEB version YET!! Enter transition data if applicable. Profiler will accept any number of transitions, defined by begin tran -- end tran pairs. Transitions can be entered with the same front and rear diameter and the data is handled properly ( i.e. ignored ) for the BEq's. This feature allows you to enter short sections of MMT aft of the fins or a Booster Stage Tube or whatever you can dream up.
Enter the fin data. This is the important part. The fins are entered as vertices ( which I errantly called edges ) starting at the leading, root and proceding clockwise.
The first value is the Z-val ( distance back along the body tube ) the second val is the purpendicular radial distance ((Z,R) in cylindrical coords ).
Start with the (Leading,Root) point. Enter the (Z,R) val for each vertex. Set the other parameters and you are done.

The Small Print

There is a lot of data ( too much ) in the .dat file. But I am leaving it in there for now because profiler was written as a module for an off-vertical altitude simulator ( overt ).

How to Plot a Rocket

PROFILER will produce a .ps plot file for your postscript ready printer and a .dat file which contains numeric data from the calculations. The picture will be marked with some crosses, indicating the centroids and/or CP of various elements. On the Body Tube, one cross ( almost always the 'front' one ) is the centroid of the rocket plan area. The aft one is the CP.

There is also a plot of a disembodied fin(s) that shows the centroid(s) and the Midchord(s). This is especially useful for odd-numbered-finned rockets because the fins on the BT are distorted by the cylindrical to cartesian transformation. ( NOTE: I have not really done any rockets with other than 3 or 4 fins and the algorithm I use won't work on all of them, depending on the fin shape ).