By the way, adults may want to pay attention, too. There are unsolved problems in this field that could make you rich beyond your dreams. (Seriously.)

Urination

Even before reaching outer space, an astronaut is likely to have problems with urination.

When seated in their acceleration couches before liftoff, astronauts are on their back, with legs elevated above their trunk. This position enhances blood flow to the kidneys, which respond by increasing production of urine. Staying in such a position for hours is likely to fill the bladder to capacity.

Shuttle astronaut Jerry Linenger comments:

I can personally attest to the fact that it is impossible not to have a tremendous urge to urinate when your legs are elevated above your head for three hours. Whenever one of the crew began to whistle softly, we knew what he was up to. 1a

Pre-Flight: The Early Days

The movie The Right Stuff, famously (and humorously) depicts Alan Shepard's confrontation with this problem, in the first American manned space mission. (In the movie, Shepard's pre-flight coffee intake was blamed for his urge.) Shepard was ultimately forced to urinate in his space suit.

[Grissom, Truman 2a] [Gagarin and the right rear tire]

During Flight

Space Walks and Moon Walks

Women

When Dr. Zebra worked at the Johnson Space Center in 1982, he was taken on a tour of the Hamilton Standard Company, the makers of the astronaut spacesuits. He was told that the male astronauts of the 1960s and 1970s had worn a condom catheter under the spacesuits they used for space-walks and moon-walks. Condom catheters have been routinely used by men in hospitals for years, but there is no analog for women despite the fervent wish for one by many physicians, nurses, and patients.

So, with the "can do" attitude characteristic of the American space program of those years, the Hamilton Standard engineers set out to solve this problem of plumbing that had so far resisted solution on earth ... and they succeeded. Dr. Zebra's guide told him that the new device would fit into the opening of the female urogenital tract and remain in place. To describe the shape of the device, he made his hand into the shape shown, and described it as looking like "a venus fly-trap, with spikes." The proud engineers, presumably all male, approached various secretaries in the company to be test subjects, but after one look at the device, all the secretaries said no. They probably said something a little stronger, as the project was dropped, and a diaper system (then called DACT: disposable absorptive collecting something-or-other) was fielded.