Space.com
10-17-07
NASA's New Spacecraft Air Leak Sensor
By Bill Christensen
An air leak sensor under development by an Iowa State research team is finally
ready for installation as a prototype on a NASA spacecraft. Air leaks are
notoriously difficult to find, because instruments and other gear cover most of the
interior surface of spacecraft.
At present, astronauts aboard the International Space Station (ISS) use
microphones to listen for the telltale hiss of air escaping into space. However,
most of the sound energy goes out into space along with the air.
To give you some idea of the scope of the problem, consider the leak that
developed on the ISS in January of 2004. The leak, which turned out to be just
one millimeter wide, took several weeks to find and patch. If the leak had not
been found, the astronauts would have been forced to return home.
The new air leak sensor (see photos) uses structure-borne vibration to detect the
direction of the leak. The one-inch square sensor includes an array of 64
elements that detect vibration. The different elements pick up vibrations at
different times. The data is analyzed by a computer to determine the direction of
the leak; multiple sensors reduce the amount of time to detect a leak to a
approximately one minute.
The research team is being lead by Dale Chimenti, and Iowa State
University professor of aerospace engineering. The other team members are
Stephen Holland, an assistant professor of aerospace engineering; Ronald
Roberts, a scientist for Iowa State's Center for Nondestructive Evaluation; Ricky
Reusser, a recent Iowa State graduate who earned his bachelor's degree in
aerospace engineering; and Steven Sulhoff, a senior in aerospace engineering
from Avoca.
Chimenti's team is now working with Invocon, a company that has already
provided sensors to the ISS. If NASA approves Phase II funding, an air leak
system will be prepared for installation.
Creative thinking about air leaks in space preceded the actual space program.
Science fiction writer Robert Heinlein came up with a more colorful method in his
1948 short story Gentlemen, Be Seated, which described life in a lunar habitat.
"There were perhaps a dozen bladder-like objects in the tunnel, the size and
shape of toy balloons. They seemed to displace exactly their own weight of air;
they floated without displaying much tendency to rise or settle. Konski batted one
out of his way and answered me before I could ask.
'This piece of tunnel was pressurized today,' he told me.
'These tag-alongs search out stray leaks. They're sticky inside. They get sucked
up against a leak, break, and the goo gets sucked in, freezes and seals the
leak.'"