Electronic Nose

NASA researchers are developing an exquisitely sensitive artificial nose for space exploration.

Onboard the space station, astronauts are surrounded by ammonia. It flows through pipes, carrying heat generated inside the station (by people and electronics) outside to space. Ammonia helps keep the station habitable.

But it's also a poison. And if it leaks, the astronauts will need to know quickly. Ammonia becomes dangerous at a concentration of a few parts per million (ppm). Humans, though, can't sense it until it reaches about 50 ppm.

Ammonia is just one of about forty or fifty compounds necessary on the shuttle and space station, which cannot be allowed to accumulate in a closed environment.

And then there's fire. Before an electrical fire breaks out, increasing heat releases a variety of signature molecules. Humans can't sense them either until concentrations become high.

Astronaut Mike Fincke onboard the International Space Station.

Astronauts need better noses!

That's why NASA is developing the Electronic Nose, or ENose for short. It's a device that can learn to recognize almost any compound or combination of compounds. It can even be trained to distinguish between Pepsi and Coke. Like a human nose, the ENose is amazingly versatile, yet it's much more sensitive.

"ENose can detect an electronic change of 1 part per million," says Dr. Amy Ryan who heads the project at JPL. She and her colleagues are teaching the ENose to recognize those compounds - like ammonia - that cannot be allowed to accumulate in a space habitat.

Here's how it works: ENose uses a collection of 16 different polymer films. These films are specially designed to conduct electricity. When a substance - such as the stray molecules from a glass of soda - is absorbed into these films, the films expand slightly, and that changes how much electricity they conduct.

Because each film is made of a different polymer, each one reacts to each substance, or analyte, in a slightly different way. And, while the changes in conductivity in a single polymer film wouldn't be enough to identify an analyte, the varied changes in 16 films produce a distinctive, identifiable pattern.

Electronic Noses are already being used on Earth. In the food industry, for example, they can be used to detect spoilage. There's even an Electronic Tongue, which identifies compounds in liquids. The ENose needs to be able to detect lower concentrations than these devices.

E-Nose

Right now, Ryan is working on a stand-alone version of ENose. "Everything is in one package," she explains: polymer films, a pump to pull air (and everything in the air) through the device, computers to analyze data, the energy source. The noses could simply be posted, like smoke detectors, at various points around the habitat.