For a single rocket, gender falls within the engineering slack. But—and NASA didn’t like very much to discuss it—the more you invest, mission-resources-wise, in your astronauts, the more you want them to be female.
Every gram counts, and women end up being preferable due to cascading effects of this rule. Women are, on average, a bit lighter, but the real benefits are secondary. Lighter means less EVA fuel, less transfer fuel, smaller boost costs, smaller and lighter spacesuits and clothes—and over a mission lifetime, vastly less food, less water, less mass that needs to be heaved out of Earth’s gravity well at thousands of dollars per precious kilogram. Then make everything modular and tailored to one gender instead of two, and everything gets simpler, smaller, and, yes, lighter. Every gram counts.
And so, in the early years, more and more astronauts just sortof happened to be women. Only by slashing launch costs could a compelling economic (and let’s face it, sociological) argument for equality be made. Construction began on ISS Clarke, the terminus of the first space elevator, the instant the required materials were developed. The politicians, so statistically male, so staunchly and implicitly anti-science for so long, had finally looked up at all the smiling ladies in the heavens and found envy. The funding for ISS Clarke, long proclaimed impossible to acquire, somehow materialized immediately.
And they painted it red . . .
Ed. note: This story was derived from my own reasoning but apparently, real engineers think the same way.