Ma. Bourham et al., ANALYSIS OF SOLID-PROPELLANT COMBUSTION BEHAVIOR UNDER ELECTROTHERMALPLASMA INJECTION FOR ETC LAUNCHERS, IEEE transactions on magnetics, 33(1), 1997, pp. 278-283
Enhanced burn rates of solid propellants through plasma erosion has be
en studied showing evidence of increased burn rate with injection of e
lectrothermal plasmas into the propellant. These experiments are desig
ned to evaluate the effectiveness of maximizing energy versus momentum
transport, and the influence of geometry on the burn rates of the JA-
2 solid granular propellant. A series of experiments has shown an evid
ence of enhanced burn rate at pressures between 55 and 90 MPa (8,000 a
nd 12,000 psi, respectively) over 400 mu s pulse length. A 20 to 40% e
nhancement in the burn rates has been observed when plasma is injected
parallel to the surface of the propellant. When plasma is injected no
rmal to the surface, the burn rate increases by about a factor of thre
e. A set of experiments has been designed to measure the burn rates wh
en the electrothermal plasma is injected at various angles, from 0 deg
rees to 90 degrees, to the surface of the propellant. Experiments were
conducted at a constant input energy of 5 kJ+/- 2% to the electrother
mal plasma source and constant base pressure of 15 Torr, which provide
s a 12,300 psi plasma pressure at the source exit close to the surface
of the propellant. Results indicate increased burn rates with increas
ed angle of injection. Optical emission spectroscopy measurement revea
led a decrease in plasma temperature, at the plasma-propellant interfa
ce, with increased angle of injection. The plasma temperature at 90 de
grees injection angle is about 30% less than that at 0 degrees. The te
mperature decrease may be attributed to increased burn rates at larger
angles, which results in an increased effectiveness of the vapor shie
ld plasma. the plasma density also decreases with increased angle of i
njection, but increases again at 90 degrees. There effects may also be
due to increased neutral constituents at the plasma-propellant interf
ace at larger injection angles. However, the plasma density at 90 degr
ees, where the burn rate is at a maximum, increases by approximately a
factor of two higher than that of the source plasma.