The most common and most likely answer to this crossword clue is the 7 letter word ROOMFUL
R
O
O
M
F
U
L
More clues leading to the result ROOMFUL
Buddy explains!

The straight part
We know that "People going into space" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case people going into space = roomful.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ROOMFUL mean?
ROOMFUL noun- The amount that a room can hold, especially the number of people that can fit into a room.
- The people in a room, considered as a group.
- Abounding with room or rooms; roomy.