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Experiment/Payload Overview

Brief Summary

Without gravity, gas bubbles form pores in a soldering joint can reduce its strength. In this experiment, astronauts solder different sets of materials (small wires wrapped with solder in different configurations) while taking video images. By looking at the soldering process and microscopically examining the different samples, it will be possible to determine better methods for soldering in space.

Principal Investigator

Richard Grugel, Ph.D., Marshall Space Flight Center, Huntsville, AL, United States

Co-Investigator(s)/Collaborator(s)

Information Pending

Payload Developer

Vanderbilt University, Nashville, TN, United States
Intel Corporation, Santa Clara, CA, United States

Sponsoring Space Agency

National Aeronautics and Space Administration (NASA)

Sponsoring Organization:

Exploration Systems Mission Directorate (ESMD)

ISS Expedition Duration:

April 2003 - April 2005

Expeditions Assigned

7, 8, 9, 10

Previous ISS Missions

ISSI is a unique investigation that has not been conducted in microgravity before.

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Experiment/Payload Description

Research Summary

• Soldering is an important general technique that may be needed for repair of spacecraft either in orbit or on the way to the Moon or Mars.



• On Earth, soldering depends on gravity and convection for proper solidification, joint shape, joint integrity and microstructure. Some detrimental gas bubbles or void spaces form in the solder joint at contact surfaces. These voids reduce the thermal and electrical conductivity as well as provide sites for crack initiation.



• In the reduced gravity environment on orbit, bubbles have less chance to escape and weaker joints are more of a problem than on Earth.



• In this experiment, soldering is done on a set of samples that were systematically selected to have pore development, surface wetting and shape formation. The soldering process is observed using a video camera and then the samples will eventually return to Earth for critical evaluation.

Description

The In-space Soldering Experiment (ISSI) is another payload that was rapidly developed after the Columbia accident to provide a lowmass experiment using hardware already on board station. 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 a microgravity environment such as that found on ISS. In Earth?s gravity, soldering has a defined behavior and is reliant on gravity and convection to assist in solidification, joint shape, integrity, and microstructure. Unfortunately, on Earth detrimental gas bubbles (void spaces) are still found in the solder joint and at contact surfaces. These voids reduce the thermal and electrical conductivity and provide sites for crack initiation. Bubbles have less chance to escape in the reduced-gravity environment of space 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. After the samples were heated on orbit, they were returned to Earth for property testing and metallographic examination.

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Applications

Space Applications

The ISSI payload provides unique insight into microgravity soldering methods, which could play a fundamental role in maintaining the International Space Station as well as provide understanding of repair capabilities on future missions to the Moon and to Mars.

Earth Applications

The study of soldering in space could lead to better soldering techniques here on Earth.

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Operations

Operational Requirements

The experiments are being conducted in the ISS Maintenance Work Area (MWA), which serves to contain the smoke produced and the debris created during the soldering procedure. The soldering iron used is that already available on space station. It runs off of a rechargeable battery and can heat up to 315.6 degrees C (600 degrees F). After soldering, the samples will be returned to Earth.

Operational Protocols

The ISS Maintenance Work Area (MWA) is set up with a video camera mounted to observe the procedure. Then the samples of wire wrapped in solder (called coupons) are heated with the soldering iron.

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Results/More Information

Five soldering sessions resulted in 86 samples. The experiment samples were returned to the investigator team in late 2005, and were evaluated both nondestructively and then destructively.

Real-time downlink video of the experiment yielded direct observation of the solder melting, equilibrium shape attainment by the liquid, and flux movement. The flux movement was particularly noteworthy because it was entirely unexpected. When the flux was released from the solder during heating, it formed a droplet that spun around the larger solder drop. This surprising movement is driven by thermocapillary flow induced by the temperature gradient. This type of behavior cannot be duplicated on Earth. (Evans et al. 2009)

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Related Web Sites

Science @ NASA

NASA Fact Sheet

Science @ NASA Soldering Surprise

Aerospace America - Engineering Notebook: Soldering in Space Holds Surprises

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Publications

• Grugel R N,Cotton L J,Segre P N,Ogle J A,Funkhouser G ,Parris F ,Murphy L ,Gillies D ,Hua F ,Anilkumar A V,The In-Space Soldering Investigation (ISSI): Melting and Solidification Experiments Aboard the International Space Station Proceedings of the 44th AIAA Aerospace Sciences Meeting and Exhibit 2006

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Ground Based Results Publications

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ISS Patent Publications

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Related Publications

• Pettegrew R D,Struk P M,Watson J K,Haylett R D,Experimental Methods in Reduced-Gravity Soldering Research NASA TM 2002
• Limmaneevichitr C ,Kou S ,Experiments to Observe Marangoni Convection in Simulated Weld Pools and Its Effect on the Weld Pool Shape NASA TM 2001
• Megaridis C M,McNallan M ,Wallace D B,Microgravity Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology NASA TM 1999

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Images

Video Screen Shot of ISS Science Officer Mike Fincke using a soldering iron to perform the ISSI experiment on ISS during Expedition 9.

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NASA Image: ISS009E14473 - During expedition 9 Mike Fincke worked on the ISSI payload in the Maintenance Work Area.

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NASA Image: ISS010E9379 - Soldered ISSI sample from Expedition 10.

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NASA Image: ISS010E932 - Soldered ISSI samples from Expedition 10.

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