Impulse Measurements of Electric Solid Propellant in an Electrothermal Ablation-Fed Pulsed Plasma Thruster

Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled and extinguished) through the application and removal of an electric current. These propellants are also being considered for use in the ablative pulsed plasma thruster. In this paper, the performance of an electric solid propellant operating in an electrothermal ablation-fed pulsed plasma thruster was investigated using an inverted pendulum micro-Newton thrust stand. The impulse bit and specific impulse of the device using the electric solid propellant were measured for short-duration test runs of 100 pulses and longer-duration runs to end-of-life, at energy levels of 5, 10, 15 and 20 J. Also, the device was operated using the current state-of-the-art ablation-fed pulsed plasma thruster propellant, polytetrafluoroethylene or PTFE. Impulse bit measurements for PTFE indicate 10020 N-s at an initial energy level of 5 J, which increases linearly by ~30 N-s/J with increased initial energy. Measurements of the impulse bit for the electric solid propellant are on average lower than PTFE by 10% or less. Specific impulse for when operating on PTFE is calculated to be about 450 s compared to 225 s for the electric solid propellant. The 50% reduction in specific impulse is due to increased mass ablated during operation with the electric solid propellant relative to PTFE

Performance Measurements of Electric Solid Propellant in an Ablative Pulsed Electric Thruster

Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled and extinguished) through the application and removal of an electric current. These propellants may also be used for electric in-space propulsion, specifically in the ablative pulsed plasma thruster. In this paper, we will investigate the performance of an electric solid propellant operating in an ablation-fed pulsed plasma device by use of an inverted pendulum micro-Newton thrust stand. Namely, the impulse-per-pulse and the specific impulse of the device using the electric solid propellant will be reported for test runs of 100 pulses and energy levels of 5, 10, 15 and 20 J. Further, the device will also be tested using the current state-of-the-art pulsed plasma thruster propellant, polytetrafluoroethylene. The performance of each propellant will be compared for each energy level using an identical setup and apparatus. This comparison of performance between propellants in a controlled setting will allow for better understanding of previous experimental observations

Impulse and Performance Measurements of Electric Solid Propellant in a Laboratory Electrothermal Ablation-Fed Pulsed Plasma Thruster

Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled and extinguished) through the application and removal of an electric current. This behavior may enable the propellant to be used in multimode propulsion systems utilizing the ablative pulsed plasma thruster. The performance of an electric solid propellant operating in an electrothermal ablation-fed pulsed plasma thruster was investigated using an inverted pendulum micro-newton thrust stand. The impulse bit and specific impulse of the device using the electric solid propellant were measured for short-duration test runs of 100 pulses and longer-duration runs to end-of-life, at energy levels of 5, 10, 15 and 20 J. Also, the device was operated using the current state-of-the-art ablation-fed pulsed plasma thruster propellant, polytetrafluoroethylene (PTFE). Impulse bit measurements for PTFE indicate 100 ± 20 µN-s at an initial energy level of 5 J, which increases linearly with energy by approximately 30 µN-s/J. Within the error of the experiment, measurements of the impulse bit for the electric solid propellant are identical to PTFE. Specific impulse when operating on PTFE is calculated to be about 450 s. It is demonstrated that a surface layer in the hygroscopic electric solid propellant is rapidly ablated over the first few discharges of the device, which decreases the average specific impulse relative to the traditional polytetrafluoroethylene propellant. Correcting these data by subtracting the early discharge ablation mass loss measurements yields a corrected electric solid propellant specific impulse of approximately 300 s

Specific Impulse of Electric Solid Propellant in an Electrothermal Ablation-Fed Pulsed Plasma Thruster

Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled, and extinguished) through the application and removal of an electric current. Recent work has focused on application of this propellant in an electrothermal ablation-fed pulsed plasma thruster. In this paper, impulse bit measurements in such devices fed by either the electric solid propellant or a traditional state-of-the-art propellant, polytetrafluoroethylene, are expanded upon. It is demonstrated that a surface layer in the hygroscopic electric solid propellant is rapidly ablated over the first few discharges of the device, which correspondingly decreases specific impulse relative to the traditional polytetrafluoroethylene propellant. Correcting these data by subtracting the early discharge ablation mass loss measurements yields a corrected electric solid propellant specific impulse of approximately 300 s. As the test duration increases to a large number of discharges, and the initial mass loss is a reduced fraction of the total, the effect of absorbed water in the propellant is decreased and the specific impulse without any corrections approaches the corrected 300 s value

Ceramics and the political economy of Moundville: a compositional study using Neutron Activation Analysis

Neutron Activation Analysis (NAA) is used to determine the chemical composition of 80 stylistically local and nonlocal ceramics recovered from the Mississippian civic-ceremonial center of Moundville in west-central Alabama. The chemical data derived from NAA is compared to a previously analyzed ceramic chemical database produced for the Mississippian Southeast in order to: (i) independently confirm if pottery specimens are locally made or imports; (ii) evaluate the accuracy of traditional sourcing of pottery by style techniques as compared to NAA sourcing; and (iii) identify the sources of pottery, allowing for the mapping of the spatial extent of Moundville's trade and interaction network. These results are then used to critique our current model of Moundville's political economy, especially as it relates to the use of prestige goods as an ideological source of elite authority. The analysis demonstrates that NAA can successfully differentiate between locally produced and nonlocal pottery. NAA generally confirms the accuracy of stylistic analyses in identifying the foreign nature of archaeological ceramics, but the results also indicate the need for chemical compositional analysis in order to fully and accurately map the distribution and production sources of prehistoric ceramics at Moundville. Confirmation of nonlocal trade in ceramics leads to the conclusion that elites at Moundville maintained links with distant populations, providing some evidence to support the efficacy of the prestige goods model in describing the establishment and legitimization of chiefly power in the Mississippian world. (Published By University of Alabama Libraries