The NASA In-Space Propulsion Technology project's current products and future directions
Since its inception in 2001, the objective of the In-Space12 Propulsion Technology (ISPT) project has been developing and delivering in-space propulsion technologies that enable or enhance NASA robotic science missions. These in-space propulsion technologies are applicable, and potentially enabling for future NASA flagship and sample return missions currently under consideration, as well as having broad applicability to future Discovery and New Frontiers mission solicitations. This paper provides status of the technology development, applicability, and availability of in-space propulsion technologies that recently completed, or will be completing within the next year, their technology development and are ready for infusion into missions. The paper also describes the ISPT project's future focus on propulsion for sample return missions.
The status of spacecraft bus and platform technology development under the NASA ISPT program
The In-Space Propulsion Technology (ISPT) program is developing spacecraft bus and platform technologies that will enable or enhance NASA robotic science missions. The ISPT program is currently developing technology in four areas that include Propulsion System Technologies (electric and chemical), Entry Vehicle Technologies (aerocapture and Earth entry vehicles), Spacecraft Bus and Sample Return Propulsion Technologies (components and ascent vehicles), and Systems/Mission Analysis. Three technologies are ready for near-term flight infusion: 1) the high-temperature Advanced Material Bipropellant Rocket (AMBR) engine providing higher performance; 2) NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system, a 0.6-7 kW throttle-able gridded ion system; and 3) Aerocapture technology development with investments in a family of thermal protection system (TPS) materials and structures; guidance, navigation, and control (GN&C) models of blunt-body rigid aeroshells; and aerothermal effect models. Two component technologies being developed with flight infusion in mind are the Advanced Xenon Flow Control System and ultra-lightweight propellant tank technologies. Future directions for ISPT are technologies that relate to sample return missions and other spacecraft bus technology needs like: 1) Mars Ascent Vehicles (MAV); 2) multi-mission technologies for Earth Entry Vehicles (MMEEV); and 3) electric propulsion. These technologies are more vehicles and mission-focused, and present a different set of technology development and infusion steps beyond those previously implemented. The Systems/Mission Analysis area is focused on developing tools and assessing the application of propulsion and spacecraft bus technologies to a wide variety of mission concepts. These in-space propulsion technologies are applicable, and potentially enabling for future NASA Discovery, New Frontiers, and sample return missions currently under consideration, as well as having broad applicability to potential Flagship missions. This paper provides a brief overview of the ISPT program, describing the development status and technology infusion readiness of in-space propulsion technologies in the areas of electric propulsion, Aerocapture, Earth entry vehicles, propulsion components, Mars ascent vehicle, and mission/systems analysis.
Characterization of Plasma Flux Incident on a Multi - Thruster Array
NASA Glenn Research Center performed a multi -thruster arra y test as part of the NASA’ s Evolutionary Xenon Thruster (NEXT) project. The test article was an array of 40 cm engineering model engines in a “3+1” configuration . The plasma environment in the immediate vicinity of the array potentially has an effect on t he erosion of the thruster system as well as of the spacecraft surfaces. To better assess this effect , an assortment of electrostatic probes was used to characterize the plasma i n the plane of and behind the array. The probes included a variety of Langmuir probes, retarding potential analyzers , and a bias -able dorman t thruster accelerator grid. At various operating conditions, the Langmuir probes were used to determine the plasma density, plasma potential, and electron temperature of the plasma at discre te locations in the plane of and behind the array. The retarding potential analyzers and bias -able dormant thruster accelerator grid were used to determine the back -flowing ion energy and ion impingement current, respectively, as a function of array configura tion and operating condition. These data were acquired over the NEXT throttle range. When the thrusters operated in an array configuration the plasma potential and electron temperature values measured at the array were similar in magnitude to those measur ed at the array during single thruster operation. Results also indicate d that facility effects contribute d to the plasma density in the vicinity of the array, causing a nonlinear increase in plasma density and ion saturation current as a function of operat ing condition. However, it was shown that the ions back -streaming to the array were of low energy; therefore , they should not cause wear to the array.