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 the cheat-code dethweezul.
If it works you should see the word outcome with a number underneath each 
completed mission. 
The cheat mode enables the following cheat keys:

In the player history screen: 
[Left-Shift Backspace]Add mission 
[Left-Shift =]  Toggle outcome of selected mission
[Left-Shift 0] (zero on top row)  Add all missions (Make all missions ccessible) 

In the game: 
[Left-Shift P]   Dump an image file to PSG\RESOURCE\ART\SCREENS 
[Left-Shift 8]   Jump to vicinity of target 
[Left-Shift 9]   Match velocity with target 
[Left-Shift 0]   Explode targeted ship 
[Left-Shift I]   Make player invulnerable 
[Left-Shift N]   Instant repair 
[Left-Shift W]   Force mission win 
[Left-Shift G]   Show all reachable planets and moons as waypoints 
[Left-Shift J]   Jump instantly to current lagrange point destination 

Command Line Options: 
If you edit the games shortcut you can enable several functions by adding one
or more options to the command line. 
-w    Play in a window on your desktop (256 color mode recommended)
-xsound     Turn off the sound 
-start1     Start from savepoint 1* 
-start2     Start from savepoint 2* 
-start3     Start from savepoint 3* 
-start4     Start from savepoint 4* 
-slot0Use save slot 0 
-slot1Use save slot 1
-slot2Use save slot 2 
-slot3Use save slot 3 
-slot4Use save slot 4 
-slot5Use Save slot 5 
-nozlock    If you get corrupted screenshots in 3Dfx mode, then use this option
to output screenshots correctly. 

* WARNING: Using the savepoint command line options can cause serious gameplay
problems or even crash the game if used incorrectly