Worked out the three of the themes (Explorers, Space Missions and Greek Gods) but couldn't finish it - good one

Excellent

Very good

Frustrating. Saw what all the groups were within about ten seconds, but there were too many alternatives for each one, so I couldn't keep track of what I'd already tried, so failed to sort one single group. If my knowledge of US state capitals and US space programmes were more encyclopaedic, maybe I'd have had a chance.