Changjun Ke

Experimental Investigation on Air‐ Breathing Mode of Laser Propulsion

The recent progress in our experimental investigation on the air‐breathing mode of laser propulsion has been reported. With a high power TEA‐CO2 pulsed Laser, both horizontal and vertical propulsion experiments were conducted. The energy of each pulse is 15–18J. The frequency can be adjusted from 20–180Hz. Several parabolic reflectors of aluminum alloy with different focus f were used in the experiments. A high speed CCD camera was applied to record movement variables of the reflectors. For single pulse experiments, the measured momentum coupling coefficient Cm is 27.7dyne.s/J for f=10mm, and 22.82dyne.s/J for f=15mm. For multi‐pulse experiments (frequency 50Hz, work time 0.5s), the horizontal propulsion distance was greater than 1.5m, and the vertical propulsion height exceeded 1m, but the average Cm is lower than that of single pulse experiments.

Experimental Study on Laser Propulsion of Air‐breathing Mode

A series of experiments were done to investigate the effect of laser parameters on laser propulsion. A high power high repetition rate TEA CO2 laser was employed in the experiments. The output energy of the laser is up to 15J and the repetition rate is up to 150 pps. The light craft models in the experiments were two parabolic aluminum shells with the exit diameter of 50 mm, the focus lengths were 5mm and 10mm respectively. The effect of the laser’s repetition rate on coupling coefficient was mainly investigated. The value of optimal repetition rate for laser propulsion of air‐breathing mode is discussed. On the basis of our investigation, a setup of laser propulsion demonstration experiment was designed. And laser‐powered free flight demonstration was realized. The 4.2g parabolic craft with 10mm focus length was boosted by the TEA CO2 laser to the altitude of more than 2.6m (limited by the ceiling of the laboratory) in a flight lasting 1.75s. The output pulse energy is 13J and the repetition rate is 50 pps.

Investigation on momentum coupling coefficient for a parabolic shell

Momentum coupling coefficients of TEA CO2 laser pulses for a parabolic aluminum shell were investigated. Momentum coupling coefficients were measured with a pendulum in a chamber, the energy of the incident laser pulse was varied from 8.3J to 50.9J, and the gas pressure in the chamber was changed from 100 kPa to 20 kPa in our experiments. Experimental data were analyzed thoroughly. It was found that the coupling coefficients under the air pressure of 100kPa decreased very slowly from 242 N/MW to 170 N/MW for the incident energy from 50.9J to 15.1J but decreased sharply for the energy between 15.1 J to 13.8 J. And it was different for the air pressure below 100 kPa. Indoor free flight of our parabolic shell was also analyzed, coupling coefficients and some other parameters were deduced from the experimental data.