This achievement is fairly easy to unlock. Simply destroy 1000 vehicles in adventures while playing in the space stage and you will unlock it.
Like "Demolition Expert", the vehicles must be directly destroyed by your captain's attacks in order to count. If the vehicles are destroyed via grenades, mines, or any other methods that aren't your own attacks, they are not counted. The Missile Flinger is the best tool for this, as it is the only captain part that does splash damage and can destroy several vehicles at once.
A good way to get this achievement is if you create an adventure where 1000 vehicles must be destroyed. Make sure to test the adventure's "mission summary" and see if your method of destroying vehicles is counted in "Destroyed X Vehicles". If you're lucky enough to be given the mission in the Space stage, you will earn the achievement upon completing it. You can increase your luck by creating multiple copies of the same adventure, or downloading more adventures tailor-made for the achievement off the Sporepedia.
You can replay the same adventure in the space stage as many times as you want until you get the achievement.
