Despite being a running joke for more than 30 years of space travel, what to do with human excrement and urine has been a long-time problem for the National Aeronautics and Space Administration (NASA) and its astronauts, and the space agency is looking to the public for some new ideas.

This problem will be particularly troubling on long space missions to Mars, which NASA is planning in the next 15-20 years, or possibly sooner.  Currently, the astronauts use a funnel-type system for urination and a vacuum system for excreting waste material.

That’s not a real problem as long as they are not confined to their space suits, which practically make the process impossible.  Those suits are designed to be pressurized for the astronaut’s protection and even scratching an itch becomes quite difficult, much less relieving oneself.

Diapers can provide temporary relief, but wearing them for more than one day could lead to a variety of issues, not excluding diaper rashes.

And the last thing you would want in a weightless environment would by urine and waste matter floating around the capsule and attaching itself to the controls and monitor screens.

So, the agency is asking the public for ideas of how to deal with the space waste.  Calling it the “Space Poop Challenge,” NASA has set up a website asking for public ideas on how to deal with the issue, and challenging interested parties to come up with a “system inside a space suit that collects human waste for up to 144 hours and routes it away from the body, without the use of hands.”

The challenge comes with a total prize amount of $30,000 to prove they are serious about the issue, and is open to individuals age 18 or older, as well as private, public and college teams.  Submissions must be uploaded by 11:59 EST on December 20, 2016 in order to be considered.

The designs will be evaluated for suit integrity, health and safety, comfort and ease of use, among other categories.

As the website says, “when you gotta go, you gotta go.”  And on a several month journey to Mars, you gotta go a lot, and how to deal with it is certainly NASA’s mind.