Due to the "feature" of permanently deleting a character from the game disk, sales of Sub Mission were catastrophic.
While "wiping the character" was a real threat, the game gave 2 options: 1) a "secret code" to resurrect each character once, and 2) a "petition" you had to fill out and send in with your disk if you failed to win after the cheat code.
The game came with a cassette audio tape that was required listening for the game. Also, the threat that "the characters will be wiped from the disk" was for real -- if you didn't succeed, game characters would be permanently deleted from the diskette. These two concepts made Sub Mission unique for its time period.