Nichelle Nichols’s impact can not be understated.
She was the first black woman to go to space on tv (and her impact on representation on TV should also not be understated) but she also campaigned for NASA applications of diverse voices. Her campaign led to the recruitment of Sally Ride (first woman in space), col. Guion Bluford (first black astronaut in NASA), and Mae Jeminson (first black woman in space).
Without her personal recruitment campaign (which she threatened to sue NASA if she put her reputation on the line to bring in these applications if they then did not go on to hire any of them) who knows how much longer it would have taken to get anyone other than a white man as a NASA astronaut.