Dreams about space, evacuation, and distressing situations can often reflect feelings of anxiety or uncertainty in your waking life. Here's a breakdown of some key elements in your dream:

1. Space and Evacuation: This might symbolize a desire to escape from current pressures or challenges. The idea of being trained for an unknown purpose could indicate feelings of being unprepared for something significant happening in your life.
2. Family Refusal to Join: This aspect may reflect feelings of separation or conflict within your family dynamics. It could be about differing beliefs or values, especially when faced with major changes.
3. Friend’s Actions: Your friend mistakenly believing she's doing good by launching missiles could symbolize feelings of betrayal or concern about someone close to you. It may also reflect how sometimes people can be oblivious to the consequences of their actions.
4. Korean Names: This could indicate a connection to your heritage or a desire to explore different aspects of your identity. It might also suggest feelings of being out of place or needing to adapt to new circumstances.
5. Wiping Out Cities: This destructive imagery might represent fears of loss or change in your life. It could also symbolize a feeling of powerlessness in the face of larger events or circumstances beyond your control.
6. Swimming with Mermaids: This part of the dream, while unsettling, offers a contrast to the earlier themes. Mermaids can signify beauty, freedom, and connection to emotions, suggesting a longing for escape or a more joyful experience amidst chaos.

Overall, the dream seems to express a mix of anxiety about the future, concerns about relationships, and a search for identity. It may be helpful to reflect on any current stressors in your life and consider how you can navigate them. Finding ways to communicate openly with loved ones and seeking clarity in your situation might help alleviate some of these feelings.