Here is the full list of all 24 Ark Defender achievements.
Unlock Battleship
Unlock Cruise Ship
Unlock Converted Yacht
Unlock NX
Unlock Megakeep
Unlock Destroyer Ark
Unlock Ark of the Faithful
Encounter a specific alien race
The void reaches out...
Destroy or Koret class mining station
Destroy the oversized ornament
Fill 6 flotilla slots
Survive sectors 2 through 8 with your Ion Field turned off
Find an Ith Material
Produce a Nova Bomb
Officiate the wedding
Become a patron for the arts
Have 15000 RM in the bank
Unlock All data logs
Reach sector 53
Become the student
Reach sector 50 with no upgrades on Hard
Lower Your Science to -1
Die during the first six sectors of the tutorial