Shellcalc© was originally developed by John Harradine to model shell and comet trajectories. The original paper was published by John Harradine and Tom Smith in the Journal of Pyrotechnics in 2005.
The program has been extensively revised in the subsequent years by Tom Smith.
Details of the changes and uses can be found at the following links
What is the “safe distance” for a shell?
Announcement of Shellcalc version 4.12
Announcement of Shellcalc Version 5
Announcement of Shellcalc Version 5.23
Announcement of Shellcalc Mobile
Announcement of Shellcalc Version 6 Beta
Comparison of national “Safety Distances” and ShellCalc distances
ShellCalc 