Speaker
Gouji Yamada
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.3004.pdf
Internal energy relaxation processes of nitrogen plasmas at different
electronic states in an entry flight condition
G. Yamada1, M. Kajino1, H. Kawazoe2
1
Tokai University, Hiratsuka, Japan
2
Tottori University, Tottori, Japan
Entry flight is a technical issue on the development of space vehicles used for planetary
exploration. Particularly, characteristics of plasma flows around the space vehicles should be
clarified for the better prediction of aerodynamic forces and heating rates on the body during
entry flight. In the present study, to investigate the internal energy relaxation process of nitrogen
plasma behind a shock wave, spectroscopic measurements are conducted using a shock tube
facility in an entry flight condition. The shock velocity and the spectrum position from the
shock front are determined by the double laser schliren measurement system. Emission spectra
of N2(1+), and N2+(1-) are obtained by means of the spatially- resolved imaging spectroscopy.
The rotational and vibrational temperatures are derived from the measured spectra by a
spectrum fitting method and finally temperature distributions correlated to the shock front are
obtained as shown in Figs.1(a) and (b). In these figures, the calculated temperatures are plotted
as solid lines for comparison. From Fig.1(a), it is found that the measured rotational
temperatures of N2(1+) and N2(2+) are almost same behind the shock wave and much lower
than the calculated rotational temperatures, showing the notational nonequilibrium process. On
the other hand, from Fig.1(b), the measured vibrational temperature of N2(1+) is much higher
than that of N2(2+) . This is considered to be due to the difference of internal energy relaxation
process depending on the electronic energy state. The present result has indicated that the
electronic state has great influence on the relaxation process behind the shock wave.
(a) Rotational temperature (b) Vibrational temperature
Fig. 1 The spatial distribution of temperatures correlated to the distance from shock front
