Gravity-sensitive cellular responses are regularly observed in both specialised and non-specialised cells. One potential mechanism for this sensitivity is a changing viscosity of the intracellular organelles. Here, we report a novel viscosity-sensitive molecular rotor based on meso-substituted boron-dipyrrin (BODIPY) used to investigate the response of viscosity of cellular membranes to hypergravity conditions created at the Large Diameter Centrifuge at the European Space Agency Technology Centre ESA-ESTEC. Mouse osteoblastic (MC3T3-E1) and endothelial (HUVEC) cell lines were tested and an increase in viscosity was found with increasing hypergravity loading. This response is thought to be primarily biologically driven, with the potential for a small, instantaneous physical mechanism also contributing to the observed effect. This work provides the first quantitative data for cellular viscosity changes under hypergravity, up to 15 g.