Laser Beam Welding Experiment in Vacuum and Microgravity: System Development, Parabolic-Flight Demonstration, In-Situ Diagnostics, and Results

Laser beam welding (LBW) offers a promising solution for in-space servicing, assembly, and manufacturing (ISAM) by enabling precise, high-efficiency joining processes in space environments without producing harmful ionizing radiation. However, there is a lack of experimental data under reduced gravity and vacuum conditions to develop robust welding parameters and system designs for orbital or lunar deployment. This paper reports the design, flight qualification, and parabolic-flight demonstration of a self-contained LBW platform intended to mature welding for ISAM. The system integrates a modular vacuum chamber (steady operation at 0.0013 Pa), a fiber-delivered 1070 nm laser with continuous-wave and pulsed modes, motion control, and synchronized in-situ diagnostics (thermal and weld cameras, thermocouples, accelerometer, and pressure sensors). Two flight campaigns completed 99/100 planned welds across Al2219, Ti6Al4V, and SS316L alloys, demonstrating mechanical/electrical robustness and repeatable data capture under reduced gravity. Accelerometer traces verified microgravity windows (mean 0.027 g ± 0.016 g), while ion-gauge data showed discrete pressure spikes in high vacuum coincident with weld initiation that scaled with energy and alloy. Selected Ti6Al4V trials revealed a consistent gravity dependence: both environments exhibited dwell-induced breakthrough at weld start, but only 1-g samples sustained through-thickness penetration, whereas low-g runs reverted to surface melting. This contrast is explained by a free-surface balance in which recoil pressure depresses the pool and surface tension restores it, with 1-g adding a hydrostatic bias that promotes sagging and stabilizes penetration; pulsed operation showed less sensitivity due to shorter molten lifetimes. Progressive metal-vapor deposition on the inner optical window was quantified post-flight by transmission mapping, with losses up to ~72% off the beam path and smaller losses along the irradiated path. Initial hermetic welds were produced on all three alloys. Overall, the reusable, instrumented platform enables gravity-aware parameter development and model validation at a fraction of on-orbit cost; future work targets simulation-based optimization of welding conditions in microgravity and the integration of thermal control systems to extend process capabilities.