出典:Wiktionary
space exploration (countable かつ uncountable, 複数形 space explorations)
宇宙旅行.
space beyond the earth's atmosphere
the vast frontiers of space science
宇宙時代.
the space age
the space known as the universe
relative to the earth, a portion of universal space called deep space
the thrills of space travel
the know‐how of space travel