To activate the cheat mode select the pilot roster and choose
a slot as normal. You should see the history and missions screen.

The history box must be selected before the cheat will work so
click in the history box. Make sure caps lock is off and type
darkgoat.

If it works you should see the word outcome with a number
underneath each completed mission. Some missions lead on to
different missions depending on the decisions you make, and
the number tells you which outcome was selected.

The cheat mode enables the following cheat keys:

In the player history screen:

[LeftShift][Backspace] Add mission
[LeftShift][=]         Toggle outcome of selected mission
[LeftShift][0]         Make all missions accessible

In the game:

[LeftShift][P] Dump a PCX image file to PSG\RESOURCE\ART\SCREENS
[LeftShift][M] Dump a continuous stream of PCXs (fills up your
                hard disk very quickly!)
[LeftShift][8] Jump to vicinity of target
[LeftShift][9] Match velocity with target
[LeftShift][0] Explode targeted ship
[LeftShift][i] Make player invulnerable
[LeftShift][w] Force mission win
[LeftShift][g] Show all reachable planets and moons as waypoints
[LeftShift][j] Jump instantly to current lagrange point destination

Or more complicated :

Here is a level cheat for IWAR:

Open the IWAR directory on your hard drive. Inside there should
be a folder named "PSG". Open it. Inside of the PSG folder
there is a folder named "RESOURCE". Open this too. Inside of
the "RESOURCE" folder there is a folder named "SCRIPTS". Inside
of "SCRIPTS" there should be a folder named "PRECEDENCE".
Inside of the "PRECEDENCE" folder there should be a file named
"PREC" which you should open with a spreadsheet program, like
Excel, and change all the numbers in the "PREC" column to 0,
and save. Now you can access all the levels of IWAR from the
beginning.