Zero gravity breaks the basic bodily functions we never think about

Roach reports that engineers spent decades solving problems most people never consider, because gravity normally handles them invisibly: without it, urine and feces don't simply fall away, they float and cling, turning waste management into one of spaceflight's genuinely difficult engineering problems. Early space toilets required astronauts to precisely position themselves over small suction openings, and mistakes produced messes that became, unglamorously, part of mission folklore.

She traces the evolution from crude early bags and tubes toward more sophisticated suction-based toilet systems, noting that NASA invested serious engineering resources and money into solving what sounds like a joke but is actually a life-or-death sanitation and crew-morale issue on long missions.

Roach uses this as an entry point into her larger argument: the parts of space travel that look silly or embarrassing from the outside are frequently among the hardest problems mission planners face, precisely because they involve human biology behaving in ways engineers must design around rather than simply command.

Takeaway: the unglamorous, embarrassing problems in any ambitious project often demand more genuine engineering ingenuity than the glamorous ones.