Mugen no Ryvius, Kakumeiki Valvrave Recommendations
Both are Sunrise anime about teenagers floating in space while defending off attacks from outside forces with their mecha. Both deal heavily with the personal relationships of the teenagers involved while they "struggle" to survive in the hostile environment.
Both are Sunrise mecha anime centered about a school of teenagers in space who must use their spaceship and mecha to fend off constant attackers while coping with the social and emotional problems of growing up.
A bunch of kids attending a space academy are involved in an accident and get stranded on a space vessel with no adults. However, they do a good job though at developing the story by showing all the ordeals and troubles that the kids go up against and more importantly how they affect each character's state of mind individually.
The show features several space combat scenes altho the focus of the story is around the struggle of young students trying to grasp their future.