NASA requires some of the most advance hardware available in order to construct vehicles capable of slipping out of earth’s gravity and into the wilderness of space. As the organization sets its sights on pushing manned space travel further and further away from our little blue marble to destinations like Mars, the techniques used to manufacture space vehicles are only growing more complex.
Only the highest quality standards will do for man-rated space flight hardware, requiring a highly technical, dedicated work force and a unique facility filled with some of the world’s most advanced fabrication technology.
That’s why NASA’s Marshall Space Flight Center, with its Advanced Welding and Manufacturing Facilities, is responsible for much of the success of NASA’s manual spaceflight program. Using technologies that have grown increasingly sophisticated since the 1960s, the MSFC has developed advanced welding techniques that have allowed for more capable propulsion and space launch systems.
The popularity of welding processes in NASA can be easily broken down into different eras; with Gas Tungsten Arc Welding covering NASA’s welding needs in the early 1980s, Variable Polarity Plasma Welding covering the later 1980s to the mid-1990s, and finally Friction Stir Welding rising to prominence from the early 1990s to present.
The current favorite, Friction Stir Welding, became popular after the development of a particular variation of the FSW process: Self-Reacting Friction Stirred Welding. FSW works well for the longitudinal barrel welding necessary to join many space vehicle components. However, the barrel weld joints are tapered in their thickness along the weld length. As a result, the pin used in the FSW process needs to be extracted or extended so that the pin’s length can vary depending on the thickness of the weld.
Once a retractable weld pin was developed, it was possible to add a root-side shoulder to the pin, resulting in self-reacting friction in which a two-shouldered pin rotates as a single unit as it travels along the joint.
SR-FSW enables NASA to use Friction Stir Welding on a much broader range of applications without the the expensive anvil tooling needed by the standard FSW process. However, the process leaves a hole where the pin tool is extracted. Thus, MSFC developed Friction Pull Plug Welding, a process in which the closeout hole is drilled out for cleaning, and then plugged using an extruded rod of the same aluminum alloy as the hardware being produced.
This Pull Plug welding process is just one example of the innovative welding techniques developed at the MSFC. For example, in the past, the facility investigated the use of Variable Polarity Plasma Welding and promoted the process after it was found to reduce the costly need to repair porosity that is often found in Gas Tungsten Arc Welds. The facility is also currently investigating the uses of Thermal Stir Welding and Ultrasonic Stir Welding.
The goal of all of these developments is to improve our ability to reach out into the stars, and the developments at the MSFC have been critical to the production of better space crafts and launch systems.
Right now, the MSFC is being used by NASA and aerospace contractors to develop a state of the art Space Launch System that will eventually allow manned and un-manned vehicles to more easily travel beyond low-earth orbit to the moon, asteroids and eventually Mars. The facility is also devoted to education and research, maintaining numerous projects about how weld processes work. Whenever possible, these projects involve as many students and educators as possible.
If you’d like to read more about NASA and the MSFC, we invite you to check out Welding Technology Takes Flight with NASA by Carolyn Russell, Jeff Ding, Arthur Nunes and Kirby Lawless. You can find the article in the May 2014 issue of the Welding Journal free with your membership to the AWS. We also invite you to visit American Welding Online, where you can find resources like online courses, virtual seminars and more to help you advance your welding career.