Chemical effects in plasma ignition

Experiments have been carried out to explore the role of chemical effects in the plasma-propellant interaction (PPI) process. The experiments involve varying the chemical composition of a confined, ablatively "fed" plasma, and then observing the response of the propellant (JA2, M9, or M30) via the recorded pressure traces. The combustion is terminated by rapid depressurization, allowing recovery and chemical analysis. In situ light emission measurements provide information on the relative temperatures of the plasmas investigated, as well as on the relative radiation levels at the propellant surface. The standard polyethylene (PE)-fed plasma contains carbon, hydrogen, and aluminum (the exploding wire is aluminum). A carbon-rich plasma (without hydrogen) is formed with a graphite (Gr) or lampblack (LB)-fed plasma, and a hydrogen-rich plasma with an aluminum hydride (AlH/sub 3/)-fed plasma. In addition, ammonia triborane (ATB), another hydrogen-rich reducing agent, has been tested. The results show widely varying extents of plasma-feeding for the different plasma chemistries, higher plasma temperatures (and longer duration of high temperature and radiation) for the chemistries that feed the plasma least, and post-discharge propellant combustion rates that suggest competition between the opposing radiative and pressure-producing properties of the additive.