Laser beam welding experiment in vacuum and microgravity: System development, parabolic-flight demonstration, in-situ diagnostics, and preliminary results

Laser beam welding offers a promising solution for In Space Servicing, Assembly, and Manufacturing (ISAM). It is a precise, high-efficiency joining process and does not emit x-ray radiation like electron beam welding. There is a lack of experimental data for welding processes in space conditions. This data is needed to develop welding parameters and designs for ISAM in orbit, on the moon, and beyond. This paper reports on the design, qualification, and parabolic-flight demonstration of a laser beam welding platform intended to mature welding technologies for ISAM. The system integrated a vacuum chamber, a fiber-delivered quasi-continuous wave 1070 nm laser, motion control, and in-situ diagnostics. 99 out of 100 planned welds were completed over 3 parabolic flight missions on aerospace alloys including Al2219, SS316L, Ti6Al4V, and pure Ti. These successes demonstrated the robustness of the system and its ability to repeatably capture in-situ data under reduced gravity conditions. Low gravity periods in parabolic flights were monitored with accelerometers (mean 0.027 g ± 0.016 g). Progressive metal-vapor deposition on the inner optical window resultant from vaporization during welding was quantified post-flight by transmission mapping, with losses up to ∼72% off the beam path. Ion-gauge data showed pressure spikes in vacuum levels coincident with weld initiation with the magnitude of change in pressure dependent on energy and alloy. Selected Ti6Al4V trials revealed a difference between the penetration of continuous wave welds: 1-g welds were full penetration, whereas low-g welds were only partial penetration. The first hermetic welds produced in low-g conditions were fabricated on all alloys. This experimental platform enables variable gravity parameter development at a fraction of on-orbit cost.