Thrust Profile Data Files

This page describes the files my altitude-predicting rocket flight simulator uses for motor thrust versus time profiles. I got most of them from Kevin Carder of the Teeniemünde Rocketry Club but I don't know where he found them.

If you want a motor added to the simulator's menu, prepare a file in this format and email it to me at

Format

There is one file for each motor. The files are simple ASCII text files with lines separated by either a single line feed character (hex 0A) or a carriage-return, line-feed sequence (hex 0D 0A).
Any number of lines at the beginning of the file may start with an asterisk. These are comments. The first one shows up on the simulator result page as the motor name.
The first non-asterisk line contains two numbers. The first, an integer, is the number of data points following. The second is the difference in mass, in grams, of the motor between ignition and burnout and is used during the simulation to adjust the rocket's mass as the motor burns.
This is the mass of the propellant and any other mass that is lost during the burn. I casually call this the "fuel", but in the case of a bipropellant system, this means all propellants, including the oxidizer.
The remaining lines are the thust data points. Each line has a time, in seconds, and the thrust, in Newtons, at that time. The time is the total time since ignition. It is not the amount of time at the specified thrust value. The simulator linearly interpolates the thrust between data points. The first point should have a time of 0 and the thrust at T=0, which is going to be 0 in any real motor.

Below is an example, for the Estes C6 motor. You can also download this file from http://webalt.markworld.com/profiles/E-C6.PRF 

*Estes C6
13 10.8
0.000 0.000
0.050 2.000
0.110 8.000
0.160 13.300
0.180 13.300
0.200 10.500
0.210 8.500
0.250 7.500
0.270 6.500
0.340 6.000
0.450 5.650
1.390 5.650
1.450 0.000
  • This is the profile for an Estes C6 motor
  • The profile has 13 data points and the propellant weight is 10.8 grams.
  • Thrust is 0 at time 0
  • And ramps up to 2 Newtons at 0.05 seconds

  • The peak thrust is 13.3 Newtons, occuring 0.160 seconds after ignition and sustained until 0.180 seconds.
    So the duration of this peak is 0.02 seconds.





  • The burn ends at 1.450 seconds.

The total impulse is about 8.5 Newton-Seconds. This isn't recorded in the file, but may be obtained by integrating the profile.
Here is a run of the simulator using this profile. The red trace is the thrust contour described by the above point set.