Here is the full list of all 9 Planet Busters achievements.
Launched bombs in 3 consecutive turns.
Launched bombs in 5 consecutive turns.
Finished a mission with < 10% shield.
Played through the whole game without losing a life.
No missiles used in a 3+ level mission.
No missiles used in a 5+ level mission.
Finished a mission with 1% shield.
Highest honor possible. Your bravery knows no bounds.
All optional missions were completed.