A zero-gravity cup lets astronauts get a handle on their coffee

Science Friday
A screenshot from a NASA video explaining the development of the zero-gravity cup.

Drinking beverages from a plastic bag just isn't a proper way to be social with your astronaut colleagues. But since the dawn of spaceflight, that's the only way people in orbit could take a drink — until now.

A new zero-gravity coffee cup now lets astronauts get a literal handle on their beverages. It looks kind of like a giant nose with a handle, a design that's almost entirely informed by the physics needed to keep liquid inside.

"We actually don't have too much input to that shape," says Mark Weislogel, a senior scientist at IRPI, an Oregon-based technology company, and a professor of mechanical engineering at Portland State University in Oregon. "There's no up, no down, so we're using the properties of the shape. ... So, hey, we're stuck with it."

Weislogel helped develop the cup, which uses capillary flow — the ability of a liquid to flow in narrow spaces without the assistance of gravity, and even in opposition to it — and a specially shaped design to control the surface tension of the beverage. If you tip the cup, its shape, along with the surface tension of the liquid, brings the beverage to the person’s mouth, even in the microgravity of space. That lets the astronauts ditch the plastic bags and drink somewhat normally.

“You'll get the sensation like you're drinking on Earth, but it's still going to be a different process because gravity isn't doing it, it's surface tension that's bringing it there,” Weislogel says.

The cups were actually first made aboard the International Space Station in 2008 using available materials. That earned it the distinction of holding the first patent ever granted for something solely invented in space. The second-generation cups, however, were made on the ground and recently delivered via cargo capsule to the space station.

There's still the challenge of getting the liquid into the cup. For that, the space station has a machine on board that makes coffee, tea and 48 other beverages.

"It's got some nondescript NASA acronym, but I just like to call it 'The Galley,'" says Don Pettit, a NASA astronaut and co-inventor of the zero-gravity coffee cup.

"You can inject either room-temperature water or warm water into your bag ... you can also inject it straight into one of these cups," Pettit explains. "Then the espresso machine has a mechanism that can inject it also, straight into one of these cups."

So far, the new version of the cup has only been tested on Earth and in low-gravity simulations. It'll be up to the astronauts in the space station to put the cup through its paces — which Weislogel thinks will be no problem:

"Those astronauts," he says, "they're going to get a kick out of this."

This story is based on an interview from PRI's Science Friday with Ira Flatow.

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