Press Start to pause game play after landing on a planet. Press A, L(2), Y, A, L(2), Y, A, L(2), Y. The word "Invincible" will appear to confirm correct code entry.
Start a new game and play the following missions in order: Riot Duty on Zhada, Riot Duty on Solaris, Assault on Quilon, and Siege on Dalview. All four missions must be completed without talking to Cearle. Enter the Zero-Zero club and speak with Larmen Sholest to receive the money.
Choose "Start Game" from the Title screen. Highlight the third option on this screen, and press the B button. On the next screen, choose what you want and exit. The previous screen will appear again, except there will be a new option on the left. Choose it and your mech and go into the game. At this point, press START to pause the game and press these buttons in this order: A, L button, L button, Y, A, L button, L button, Y, A, L button, L button, Y. You will then see the word "Invincible" appear. Your mech is now invulnerable to any harm!