Actually, move that a few notches: It WON'T be heterosexual.
As part of their 'studies', they'll determine that non-hetero is the only way to go with the justification that removes the issue of pregnancy, childbirth, day care, Space 'Schooling', etc. They'll push the notion that ONLY homos go into space for pragmatic reasons.
Aye, and Gomorrah...