Interior Spectroscopic Investigation of the Propellant Energy Modes in an Arcjet Nozzle
Abstract : Internal emission spectroscopy measurements were performed in the nozzle expansion region of a 26 kW class ammonia arcjet. A series of three optical access ports (0.020-inch diameter) were equally spaced along the center line of the expansion nozzle. Atomic and ionic excitation temperatures of H and NII were determined through the use of Boltzmann plots. Electron density measurements were also taken based upon Stark broadening of the hydrogen beta Balmer transition. It is believed that a change in the mechanism governing the electron density occurred just downstream of the constrictor between the first two access ports lending evidence that arc attachment is occurring in this region. Although the trends for excitation temperatures and electron density were similar to those previously observed in 1 kW arcjets, the temperature values were found to be significantly less. In addition, vibrational and rotational temperatures of NH were measured and appeared to be frozen throughout the expansion nozzle.
Integration and diagnostics for the US air force phillips laboratory Electric Propulsion Space Experiment (ESEX)
The Electric Propulsion Space Experiment (ESEX) comprises a 30 kW ammonia arcjet system, on-board diagnostics, and a remote observations program. A scientific plan encompassing implementation, operation, and data analysis has been developed. Onboard instruments will provide accurate measurements of spacecraft acceleration, thruster operating characteristics, performance, radiated thermal loads, and will document arcjet operation through filtered imagery. Instruments will also provide upper limits for spacecraft contamination and communications band electromagnetic interference. Remote observations will accurately characterize high-rate communications links and will determine the arcjet optical and RF signatures.
Experimental Determination of the Oscillator Strength of the First Negative Bands of N2
The radiative lifetime of the upper state of the 3914 A transition of N2+ was measured to be (6.58±0.35) 10—8 sec, corresponding to an oscillator strength f of (3.48±0.20) 10—2. The apparent radiative lifetime of the upper state of the 3371 A transition of the second positive system of N2 was found to depend upon the conditions of excitation. Extrapolation to excitation threshold yields a lifetime of (4.45±0.6) 10—8 sec.