IN SPACE SOLDERING INVESTIGATION (ISSI)
Research Area: Spacecraft Materials
Expedition(s): 7-10
Principal Investigator(s): ● Richard N. Grugel, PhD, NASA’s Marshall Space Flight Center,
Huntsville, Alabama
RESEARCH OBJECTIVES
The In Space Soldering Investigation (ISSI) was rapidly developed after the Columbia accident as
a low-mass experiment using hardware already aboard the International Space Station (ISS).
While it was designed to promote understanding of joining techniques, shape equilibrium,
wetting phenomena, and micro-structural development in space, its primary objective was to
better understand the effects and consequences of soldering in microgravity. On Earth,
soldering has a defined behavior and
relies on gravity and convection to
assist in solidification, joint shape,
integrity, and microstructure.
Unfortunately, detrimental gas
bubbles (void spaces) can form in the
solder joint and at contact surfaces.
These voids reduce thermal and
electrical conductivity and provide
sites for crack initiation. In the
microgravity environment, bubbles
have less chance to escape, and
therefore, are likely to be more of a
problem. To better understand this
potential problem, a systematic series
of soldering samples was designed to
investigate and understand porosity development, surface wetting, and equilibrium shape
formation. The samples were heated in orbit and then returned to Earth for property testing
and metallographic examination.
EARTH BENEFITS
The study of soldering in space leads to a better comprehension of materials processing
techniques and fluid dynamic processes.
SPACE BENEFITS
The ISSI experiment provides unique insight into microgravity soldering methods, which could
play a fundamental role in maintaining the ISS as well as providing repair capabilities during
future exploration missions.
Video screen shot of science officer Mike Fincke using a
soldering iron to perform In Space Soldering Investigation
during Expedition 9.