Boiling of droplets on a hot surface in low gravity

The boiling of single droplets of water and n-heptane on a hot stainless steel surface was observed in a low gravity environment, obtained on board a platform in free fall. Droplet impact was photographed using a single-shot flash-photographic method. Surface temperature variation during droplet impact was recorded using a fast-response thermocouple. Droplets could not be maintained in stable film boiling in low gravity: the pressure of vapour under droplets pushed them away from the surface. Nucleate boiling of droplets was not affected by a reduction in gravity. Vapour bubbles nucleating on the solid surface separated and rose into the liquid even in the absence of buoyancy forces.