Wave Propagation in the Multilayered Low-pressure Near-space Atmosphere

The variation of sound speeds of air and nitrogen gas at temperatures from 15 to -80 °C, and at gas pressures from 10⁵ to 150 Pa have been measured in a KM2G space simulator. The objective is to provide the primary acoustic parameters to set up a proper multi-layered near-space atmosphere model, so that to simulate propagation paths of acoustic waves. From experimental data, sound speeds of both air and nitrogen gas decrease with the decreasing temperature from 15 to -80 °C and with the decreasing pressure from 10⁵ to about 5000 Pa. However, sound speeds in the 15°C rare air and nitrogen gas slightly increase with the dropping pressure below 5000 Pa, and this trend becomes more obviously when the temperature is low. This dispersion characteristic of acoustic wave in the near-space atmosphere should be considered during simulation of wave propagation.