NASA is preparing for return to the Moon and innumerable activities to equip, shelter, and otherwise support future astronauts are underway.
The astronauts will be eating and drinking, and subsequently urinating and defecating in microgravity and lunar gravity.
NASA said that while astronauts are in the cabin and out of their spacesuits, they will need a toilet that has all the same capabilities as ones here on Earth.
The public designs for space toilet may be adapted for use in the Artemis lunar landers that take humans back to the Moon.
"Although space toilets already exist and are in use (at the International Space Station, for example), they are designed for microgravity only," the US space agency said in a statement.
NASA's Human Landing System Programme is looking for a next-generation device that is smaller, more efficient, and capable of working in both microgravity and lunar gravity.
The new NASA challenge includes a Technical category and Junior category and the last date to send designs is August 17.
NASA's Artemis Moon mission will land the first woman and next man on the lunar surface by 2024.
The Artemis programme is part of America's broader Moon to Mars exploration approach, in which astronauts will explore the Moon and experience gained there to enable humanity's next giant leap, sending humans to Mars.