The John E Chambers N-Body integrator

This software was initially created by John E. Chambers. It is the N-Body integrator based on Bulirsh-Stoer, Everhart and other methods. As-is, it can integrate any star system like our Solar System.

Currently, this Gnu Fortran github project is configured for Linux and Mac OS X users. It is certainly adaptable for Windows and other O/S environments.

Manual Authored by John E. Chambers

See JOHN_E_CHAMBERS.md

How to Prepare for use

• Clone the repository from github to local storage somewhere.
• Position (cd) into the mercury folder.
• make build # Compile and link edit all programs.

Try the Sample files

• make gen-in # Copy the sample files to the mercury6 input files.
• mercury6 # Execute the N-Body integrator.

Mercury6 Standard Output (displayed) based on the Sample Files

   Integrating massive bodies and particles up to the same epoch.
   Beginning the main integration.
 Date:       2119  8  6.4   dE/E:  3.38494E-13   dL/L: -9.19199E-15
 Date:       2229  2 15.8   dE/E:  7.94146E-13   dL/L:  7.57420E-14
 Date:       2338  8 24.1   dE/E:  9.69144E-13   dL/L:  1.50381E-13
 Date:       2448  2 29.8   dE/E:  1.47573E-12   dL/L:  2.74473E-13
 Date:       2557  9 11.2   dE/E:  1.43055E-12   dL/L:  2.25571E-13
 Date:       2667  3 23.6   dE/E:  9.88369E-13   dL/L: -2.38992E-14
 Date:       2776 10  2.8   dE/E:  6.86847E-13   dL/L: -2.16380E-13
 Date:       2886  4 10.5   dE/E:  1.19048E-12   dL/L: -2.06268E-13
 Date:       2995 10 21.6   dE/E:  1.01778E-12   dL/L: -2.15460E-13
 Date:       3105  5  1.7   dE/E:  1.36844E-12   dL/L: -1.03502E-13
 Date:       3214 11  7.1   dE/E:  5.73796E-13   dL/L: -4.11434E-13
 Date:       3324  5 16.7   dE/E:  6.31800E-13   dL/L: -3.48928E-13
 Date:       3433 11 26.4   dE/E: -1.85514E-13   dL/L: -7.66980E-13
   Integration complete.

Executables Produced by Make

mercury6

This is the basic integration programme. It contains all of the code to carry out integrations using any of the algorithms described by John E. Chambers and elsewhere.

Text-format output files (*.dmp, *.tmp) are not used by the subsequent element6 and close6 programmes. They seem to be historical intermediate files. Note that file X.tmp = file X.dmp. They could use more explanation!

Binary output files ce.out (used by close6) and xv.out (used by element6) are produced in a machine-independent compressed format. They could use more explanation!

Text-format output file info.out contains a summary of the input parameters.

NOTE: Some of the parameters reside in the *.in files (changes probably do not requiring recompilation) and some of the parameters are specified in the Fortran include files - mercury.inc and swift.inc (changes require recompilation).

element6

This programme converts the mercury6 output file xv.out into a set of text-format files (*.aei) that contain Keplerian orbital elements for each of the objects of the integration. These files allow you to see how the orbit of each object change with time, thus can be used as the basis for making graphs or movies using a graphics/video package.

The resultant text-format element.out file contains a summary of body features.

The sample input files will yield element6 output files for the Solar System planets, Apollo, and Apophis.

close6

This programme converts the mercury6 output file ce.out into a set of text-format files (*.clo) containing details of close encounters between objects during the integration.

The sample input files will yield close6 output for the Solar System planets, Apollo, and Apophis.

Makefile Options

- make build   : Build the Fortran programs
- make unbuild : Remove all Fortran program executables
- make gen-in  : Generate input files by copying them from samples
- make rm-gen  : Remove all files generated by the Fortran programs
- make rm-in   : Remove all input files used by the Fortran programs
- make clean   : Remove all input files, generated files, and the executables

Fortran Include Files

mercury.inc

This contains constants and general parameters used by programmes in the mercury package.

CAUTION: Make sure that you understand the implications of changing any of the parameter values.

swift.inc

This contains constants and parameters used in the subroutines written by H.Levison and M.Duncan (1994, Icarus, vol 108, pp18). These subroutines have names that begin with either drift' or orbel'.

CAUTION: Make sure that you understand the implications of changing any of the parameter values.

Input Data from other Programmes

Please note that if you use other programs to create input data files you must maintain data items in gfortran double precision format (e.g. use "d" exponent)