This PhD thesis is dedicated to the study of non-premixed flame spread with a specific attention paid to detection and mitigation in a reduced gravity environment. These works intend to contribute to an enhanced fire safety of spacecraft. To this end, an existing rig that enables experiments in parabolic flights has been further equipped at Inst. d'Alembert. With this setup, cylindrical samples can be ignited and the subsequent flame spread documented in a reduced gravity environment. Within the spread, the surrounding laminar oxidizer flow is finely controlled, the inlet oxygen content, pressure, and flow velocity being especially adjustable. Fire detection is one of the priorities of spacecraft fire safety. It especially relies on the identification of soot particles. As a result, the lack of understanding of the soot morphology in microgravity affects the accuracy of fire detection. In this context, a novel soot sampling technique using electric fields is developed and successfully applied for the first time in microgravity to a flame spreading over cylindrical electric wire. The sampled soot particles are analyzed under Transmission Electron Microscope (TEM). With the developed TEM image analysis tools, soot particle projected area, radius of gyration, fractal dimension, and primary particle size are extracted. Then, the influence of gravity is investigated and evidenced on the evolution of these morphological properties within the flame. The lack of data on flame spread in partial gravity is also an imminent challenge to fire safety for upcoming deep space exploration. Experiments on flame spread over cylindrical samples are performed for the first time at Lunar and Martian gravity. The characteristics of flame spread are analyzed under different oxidizer flow conditions and different configurations of samples. Varying gravity and oxygen content, the extinction limits of the different sample configurations are identified and the flame spread rates are extracted. At high gravity (Mars gravity and normal gravity), droplet leakage affects the extinction limit of wire samples with lower thermal conductivity metallic cores. At the same time, it also impacts the flame spread mechanism. In particular, at Martian gravity, a cyclic flame spread is unveiled and its original mechanism is analyzed. Fire prevention has always been the key concern of spacecraft firefighting strategies, where the flammability of materials largely limits the choice of materials. Drawing on the experience of ground-based fire prevention, the enhancement of materials' performances with flame retardants may overcome the limitations imposed by material flammability. Cylindrical samples loaded with flame retardants are investigated in microgravity. Two flame retardants with different expansion mechanisms are considered, i.e., Expanded Graphite (EG) and Ammonium polyphosphate/Pentaerythritol (AP). The observed results are then reported and compared with those obtained with different flame retardant loads under normal gravity, for a given ambient pressure and flow rate, with variations in oxygen content. In microgravity, increasing the retardant load does not detectably improve the extinction limit while the reduction in flame spread rate is not as obvious as at normal gravity for the range of flame retardant loads studied. In addition, the increase in flame retardant loads under microgravity resulted in smoke emissions. This observation was more pronounced for EG loaded samples. These conflicting effects of adding AP and EG on fire safety in microgravity are not evident in normal gravity, requiring careful integration of flame retardants within the context of space exploration. The results obtained in this study provide useful information and new insights for fire detection and prevention in microgravity, while the experimental data in partial gravity might serve as a database for future fire safety design in space exploration.