Test Data Tab

The Test Data tab (next to Results and Notes, bottom right of the main window) lets you bring real motor-test data into BurnSim and compare it against a simulation.

Test data imported and overlaid on the simulated curves

Importing

• Import File... - import a CSV file; see Import from CSV for the required format
• Import Clipboard - paste data copied from a spreadsheet directly, in the same Time/Pressure/Thrust column order
• Each import becomes a named dataset, selectable from the dropdown at the top of the tab; Delete removes the selected one

Working with a Dataset

• Use in simulation - when checked, the dataset's pressure/thrust traces are drawn on the graph alongside the simulated ones, so you can see how closely the simulation matches reality. This setting is saved with the motor, so a motor you saved with its test data graphed comes back that way next time you open it.
• The grid below is a live, editable view of the dataset's raw points - edit a cell, or use Add Row / Delete Row to fix bad points
• Trim... - removes a number of points from the start of the dataset, and shifts the time base of what's left so the trimmed trace still begins at about zero. Useful for dropping a run of leading zeros recorded before the igniter fired. Note that you do not need to trim an ignition spike or a post-burnout tail for characterization - BurnSim finds and excludes those itself, and it needs the full burn to measure burn time. See Import the whole trace.

On the Graph

With a dataset checked "Use in simulation", three extra checkboxes appear above the graph (see Graph):

• Imported Pressure - the dataset's raw pressure trace
• Imported Thrust - the dataset's raw thrust trace, if it has one
• Thrust From Imported Pc - thrust back-calculated from the imported pressure trace through the motor's actual nozzle, useful when your test data only recorded pressure

All three are drawn over the full length of the imported data, however long the simulated burn turned out to be. If an imported trace carries on past the point where the simulated curves drop to zero, you are seeing real recorded data from after the motor burned out - which is normal and expected - BurnSim uses it.

Characterizing a Propellant from Test Data

BurnSim 4 can fit a propellant's burn rate coefficient and exponent (a and n) directly from a dataset imported here - open Action → Characterize Propellant... with the dataset you want to fit against selected in the dropdown above. See Characterizing a propellant inside BurnSim 4 for the full walkthrough.

Import the trace complete, from before ignition to after burnout. Earlier advice to trim the ignition spike and the post-burnout tail by hand no longer applies: BurnSim excludes both from the curve fit automatically, and it needs the whole burn to measure burn time from. See Import the whole trace.