Time-of-flight study of elementary propellants for ablative laser propulsion

The purpose of this study was to provide the first experimental investigation for Ablative Laser Propulsion, which utilizes direct laser ablation of solid targets for momentum transfer. Velocity and number density data are obtained from a time-of-flight (TOF) apparatus using 100 ps long pulses at 532 nm wavelength and 35 mJ pulse energy from an Nd:YAG-regenerative amplifier laser system. Results show that ion velocities from ablated targets range from 25 km/s (lead) to 200 km/s (carbon), corresponding to specific impulses (I_sp) in the range of 2.0–12.0 × 10 3 s. Ion yields are on the order of 1013 ions/pulse, with atomic yields at approximately 1015. Mass removal rate measurements show a trend that increases with increasing atomic mass, all on the order of μg/pulse. Momenta imparted to the samples are on the order of 10−7 kg m/s, corresponding to coupling coefficients (C_m) in the range ∼0.3–1.8 dyn/W. In contrast to I_sp, these values are found to increase with increasing atomic mass of the sample used.