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Ann Arbor, MI, United States

Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.79K | Year: 2014

The proposed work investigates an approach that would allow an annular ion engine geometry to achieve ion beam currents approaching the Child-Langmuir limit. In this respect, the annular engine, whose design inherently allows for significant increases in perveance by resolving the span-to-gap problem, can achieve the projected high current densities necessary for high thrust, high power applications. The case for high power gridded ion thrusters is compelling if not only for risk reduction in contrast to lower TRL Hall thruster variants such as the nested channel systems. This point cannot be over emphasized as there is now significant effort and resources applied to Hall engine development. Yet there still remains some uncertainty as to how high power variants or magnetically insulated variants will actually perform in space. Interpretation of high power Hall engine operation in ground test facilities is also not completely well understood. This is in contrast with gridded ion technology whose facility corrections are well understood. The current investment in high power gridded ion thruster technology is minimal. This effort seeks to address this gap in technology development and in the process continue the advancement of a credible risk reducing technology for high power mission applications.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.98K | Year: 2015

The innovation proposed is a hollow cathode that integrates mitigation methods to suppress wear to the keeper. Recent advances in the magnetic topology in Hall thrusters has eliminated erosion of the thruster walls. As such the life limiting component of Hall thrusters has shifted to the cathode lifetime. Under a previous investigation aimed at understanding the impact of high energy ions in high current hollow cathodes, we mapped the energy spectra of cathode derived ions for both a barium oxide hollow cathode and a LaB6 hollow cathode. Energetic ions were clearly present and their intensity and peak energy tended to increase with increasing discharge current. Preliminary mitigations experiments showed promise in the use of an externally applied magnetic field as a way to reduce the peak energy of the emitted ion flux. The overall goal of this proposal is to produce a hollow cathode with integrated energetic ion mitigation technology. This cathode will be tested in magnetic field environments characteristic of Hall and gridded ion engines. It will provide a good body of experimental evidence of how to successfully mitigate cathode erosion for the high powered thrusters currently under development. Additionally, an energetic ion mitigation method could be directly integrated into the cathode design for the recently proposed Asteroid Retrieval Mission (ARM) which is currently baselined to use 4-5 10 kW class magnetically shielded Hall thrusters.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 99.48K | Year: 2011

Abstract


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase I | Award Amount: 99.97K | Year: 2010

Advances in high power, photovoltaic technology has enabled the possibility of reasonably sized, high specific power, high power, solar arrays. New thin film solar arrays have demonstrated specific powers of over 4000 W/kg (exceeding the current SOA of ~130 W/kg). At high specific powers, power levels ranging from 50 to several hundred kW are feasible for communication satellites. Coupled with gridded ion thruster technology, this power technology can be mission enabling for a wide range of missions ranging from ambitious near Earth NASA missions to those missions involving other customers as well such as DOD and commercial satellite interests. The appeal of the ion thrusters stems from their overall high efficiency, typically >70%. At present, the most advanced and mature gridded ion thruster technology is that embodied in the 7-kW NEXT ion thruster. The proposed Phase I effort seeks to design and fabricate a ion thruster discharge chamber with an equivalent beam area of a 50-cm-diameter cylindrical ion thruster with the capacity to fill the 7 to 25-kW void that currently exist for ion thrusters. The overall effort (Phases I and II) will advance the TRL level of the discharge chamber for the 50-cm thruster by understanding and optimizing the discharge chamber.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase II | Award Amount: 599.24K | Year: 2011

Advances in high power, photovoltaic technology has enabled the possibility of reasonably sized, high specific power, high power, solar arrays. At high specific powers, power levels ranging from 50 to several hundred kW are feasible. Coupled with gridded ion thruster technology, this power technology can be mission enabling for a wide range of missions ranging from ambitious near Earth NASA missions to those missions involving other customers as well such as DOD and commercial satellite interests. Indeed the HEFT clearly identified the need for high power electric. The appeal of the ion thrusters for such applications stems from their overall high efficiency, typically>70% and long life. In response to the need for a single, high powered engine to fill the gulf between the 7 kW NEXT system and a notional 25 kW engine, a Phase I activity to build a 25 kW, 50 cm ion thruster discharge chamber was completed with a laboratory model fabricated. The proposed Phase II effort aims to mature the laboratory model into a proto-engineering model ion thruster. The proposed effort involves the evolution of the discharge chamber to a high performance thruster by performance testing and characterization via simulated and full beam extraction testing. Through such testing the design will be optimized leading ultimately to the proposed design, build and preliminary checkout of a proto-engineering model thruster, thereby advancing the TRL level to 4-5 range. Deliverables include the thruster, a design package, and a performance data document.

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