WASHINGTON (ISNS) -- It's a phenomenon that is annoyingly familiar to almost everyone.  You walk across a carpeted room on a dry winter day and touch a metal doorknob. The static electricity that built up when trillions of electrons were scraped off the atoms in your shoes as you crossed the room reveals itself in a minor, but startling, shock.

This isn't exactly what happens in space, but static electricity can develop, and for a spacewalking astronaut reaching out to touch the surface of the international space station (ISS), it could be a serious problem.

Like a person walking across a carpet, the ISS accumulates a charge as it orbits the Earth, plowing through the ionosphere, the upper atmosphere containing charged particles.

The interaction of charges in Earth's upper atmosphere with spacecraft surfaces have been studied for many years, but predicting how they will behave in a specific situation, such as an accumulation of excess charge on a cargo bay door, is very difficult.

Furthermore, large differences in charging between two adjacent surfaces can lead to an arc discharge that can physically harm surfaces of the ISS, especially the thermal control coating.  If such an arc discharge were to strike an astronaut, it could be very dangerous.

A new voltage-sampling device for monitoring the local electrical environment of the ISS has been successfully tested. The device, called the floating potential measurement unit, was built by scientists from Utah State University in Logan, Utah. One of the instrument team members, Aroh Barjatya of the Embry-Riddle Aeronautical University in Daytona Beach, Fla., said that the peak measured voltage is about 35 volts which does not represent a significant threat for an arc-discharge. But as the space station increases in size as it achieves its final configuration, it could build up electrical current that could trigger an arc.

The ISS has a device called the plasma contactor unit that can mitigate and counter any charging hazard, and it can be used during spacewalks so that astronauts who touch an outer surface of the space station aren't in danger of arcing.

Barjatya said that a side benefit from the new voltage sampling device is that its measurements can be used to provide new "in situ" measurements for researchers who study the ionosphere.

Inside Science News Service is supported by the American Institute of Physics.