Metal Foam Casting: Earth vs Microgravity (2D)

Space manufacturing is not only about 3D printing — casting metal foam is one of the clearest cases where removing gravity changes the physics of a material outright. This 2D cross-section simulator nucleates gas bubbles inside a molten-metal mold, moves each one every frame by the real Stokes' law buoyancy formula that governs real foundries (v = 2/9 · Δρ·g·r²/μ, which drops to zero the instant gravity is switched off), lets nearby bubbles coalesce, and freezes the structure in place as a solidification front climbs from the mold floor. Toggle gravity from Earth's 1 g down to ISS-level microgravity, save a run from each, and compare the frozen foam patterns and their measured uniformity side by side — coarse and top-heavy on Earth, fine and uniform in orbit, exactly the outcome that has driven real orbital foam-casting experiments.