her sweetheart: the person she loves
a cardboard cut-out: a photograph or drawing of someone or
something, cut to shape and stuck onto thick card
an extended mission: an official trip that is longer than
planned
to tie the knot: to get married
a cargo ship: a ship used to carry things, here a spaceship
the best man: the man who acts as attendant to the groom
at a wedding
cosmic: belonging to the universe or space
went ahead: took place, continued
the run-up to: the time before, the preparation time
controversy: a disagreement about something which leads
to a lot of discussion and argument