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(s)
Vanderbilt University, Nashville, TN, United States
Intel Corporation, Santa Clara, CA, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration:
April 2003 - April 2005Expeditions Assigned
7,8,9,10Previous ISS Missions
ISSI is a unique investigation that has not been conducted in microgravity before.
ISS Science Challenge Selected Project
I chose to research the In Space Soldering Experiment (ISSI) because I found it to be extremely relevant to the goal of maintaining a human presence in space. I also found it to be important in the development of repair capabilities in deep space, which could be crucial to a crew's survival and a mission's success. Another reason why I chose ISSI was because I have experience with soldering, and I thought that ISSI was more relatable because of this experience. Through researching ISSI, I learned about the effects of gravity on soldering, and how a microgravity environment can magnify these effects. I found it really interesting and exciting that this research will be used to develop better soldering techniques that could make in-flight repair of spacecraft more effective. I also learned about temperature gradients and thermo capillary flow, two subjects that I plan to study and learn more about after researching ISSI.
-Kelly, Grade 9, H.H. Dow High School, Midland, Michigan
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.
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.
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.
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)
Grugel RN, Cotton LJ, Segre PN, Ogle JA, Funkhouser G, Parris F, Murphy L, Gillies D, Hua F, Anilkumar AV. The In-Space Soldering Investigation (ISSI): Melting and Solidification Experiments Aboard the International Space Station. 44th Aerospace Sciences Meeting and Exhibit. Reno, NV; 2006
Pettegrew RD, Struk PM, Watson JK, Haylett DR. Experimental Methods in Reduced-Gravity Soldering Research. NASA Technical Memorandum; 2002.
Megaridis CM, McNallan M, Wallace DB. Microgravity Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology. NASA Technical Memorandum; 1999.
Limmaneevichitr C, Kou S. Experiments to Observe Marangoni Convection in Simulated Weld Pools and Its Effect on the Weld Pool Shape. NASA Technical Memorandum; 2001.