way from big g, the space shuttle and the ISS are filled with
little g's of their own. 

Is that a problem?

"Not usually," answers John Charles, the chief scientist for shuttle
mission STS-107. Most of these vibrations are vanishingly small--less
than one-millionth the acceleration of gravity here on the ground.
(Hence the term "microgravity;" the prefix "micro" means
one-millionth.) But sometimes, he says, occasional jolts and ill-timed 
vibrations can upset the most delicate experiments.

For example, "combustion experiments really don't like thruster
firings." Charles explains: Flames in space do something odd. Instead
of forming the familiar teardrop shape of candle flames on Earth, they 
contract into little balls, which float around and burn using almost 
no fuel. Scientists suspect these flame balls hold the secrets to 
leaner burning auto engines. The problem is, flame balls are delicate. 
A gentle bump is enough to knock one out. 

The mission that Charles leads, STS-107--a 16-day flight of the
shuttle Columbia, has 80+ science experiments on board. Three of them
involve flames and combustion. 

One called SOFBALL (short for "Structure of Flame Balls at Low Lewis
number") will ignite some of these flame balls in a special chamber
where scientists can experiment with them and measure their
properties. The shuttle's thrusters will be turned off to avoid
sending the floating balls careening into the walls of their chamber.
But what if a flame ball winks out anyway? Did scientists just learn
something new about flame balls? Or was it one of those g's in the
machine? 

"This is why we have SAMS--the Space Acceleration Measurement System," 
continues Charles. SAMS is a sensitive accelerometer that monitors 
vibrations and other small accelerations. "SAMS picks up everything," 
he says. People coughing. Things bouncing off walls. A knob gently 
twisted. "The device is so sensitive," he notes, "that thruster 
firings can overwhelm it." 

SAMS was developed for space research missions by a group of engineers 
and scientists at the Glenn Research Center. "When NASA started doing 
microgravity experiments onboard the shuttle, we realized that we 
would have to measure the vibratory g-levels," says Thomas Kacpura of 
ZIN Technologies, Inc., a contractor who works on SAMS. "Otherwise how 
would you know if a blip in your data was real or not?"

SAMS sensors have flown before on 22 shuttle missions, on the Mir
space station, and one is permanently mounted in the Destiny lab
module of the International Space Station. "It's indispensable for
space research," adds Charles.

On the shuttle Columbia (STS-107), SAMS is located near the SOFBALL
experiment, which is inside the SPACEHAB module in the middle of the
shuttle's cargo bay. Data from SAMS are transmitted directly to Earth
where researchers can monitor the microgravity environment in
near-real time and make decisions accordingly. If the shuttle is still 
vibrating after a thruster firing, for instance, they might wait a 
while before igniting their flame balls. SOFBALL isn't the only 
experiment that will benefit because SAMS can detect vibrations
throughout the ship. Its record of micro-accelerations will be like a
communal well--all are free to draw from the well as needed. 

So astronauts can go ahead and
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