I successfully built my first Explorer ship in NextColony (on 2020.04.02)
But I still cannot start an Exploring mission, because I need to enhance the mission control skill.
That would cost more resources than I currently have.
Cost: 2400 C, 1200 Fe, 600 Cu, 288 U / 05:00:00:00.
And yes, 5 days.
Image source: Screenshot (NextColony).
Screenshot was taken on 2020.04.02, 18:55 CEST.