Wide Throttling, High Throughput Hall Thruster for Science and Exploration Missions

In response to Topic S3.04 "Propulsion Systems," Busek Co. Inc. will develop a high throughput Hall effect thruster with a nominal peak power of 1-kW and wide throttling range in terms of both power and Isp. In Phase I the preliminary thruster design was completed. Project activities focused on achieving a magnetic field that shields the discharge channel from ion induced erosion. The goal is to achieve a propellant throughput greater than 100 kg/kW. Numerical modeling is playing a critical role in the thruster design. In Phase I, we used a fluid based code developed by JPL to model the plasma in an existing thruster that is currently undergoing life testing. The erosion predictions of the model were found to agree well with actual measurements. The numerical model was then applied to the magnetically shielded 1-kW thruster and preliminary results were found to be reasonable. The goal is to demonstrate a thruster design where channel erosion is entirely eliminated as a life limiting mechanism. In Phase II, we will build and test the extended lifetime thruster. The performance, lifetime, and plume properties of the thruster will then be evaluated, and the design will be optimized. Numerical modeling will be used throughout the process to ensure that magnetic shielding is achieved. Code predictions will be grounded in plasma measurements taken with a variety of diagnostics including channel wall probes, high speed intrusive channel probes, and plume probes. The ability of the thruster to achieve its lifetime goals will be assessed through a 500 hour wear test. When the design is finalized, an engineering development unit (EDU) thruster will be designed, built, validated, and delivered to NASA. The EDU thruster design will be modeled thermally and structurally to facilitate the transition to Phase III. At the end of the Phase II, the TRL will be 5/6.

Implementing magnetic shielding has application across the spectrum of thruster power and sizes and is therefore a cross-cutting technology. The thruster will be well suited for orbit raising and interplanetary transfers, supporting exploration and science missions. The demonstrated throttling ability is important for a singular thruster that might be called upon to propel a spacecraft from Earth to Mars or Venus. Mars orbits at 1.52 AU, which reduces the solar constant to 43% of the value at Earth. As a result the output power of a nominal 600 W array reduces to 260 W at Mars as a spacecraft travels between these planets. For NASA low power, high throughput electric propulsion systems are an enabling technology for radio isotope powered spacecraft for sample and return missions identified in the NASA Decadal Survey. A study conducted by the SMD ISPT Project in 2004 confirmed the significant potential of REP for space science, especially with recent advancements in enabling, high –specific-power RPS technology (from 3 to over 8 We/kg). The study also concluded that REP would be ready for near-term NASA science missions if an electric propulsion thruster with the appropriate specific impulse and propellant throughput capability could be developed. Examples of missions examined by this study include: 1) Trojan Asteroid Orbiters, 2) Jupiter Polar Orbiter with probes and 3)Comet Surface Sample Return (Tempel 1)

Commercial applications for the proposed system include orbit raising, circularization, inclination changes, repositioning, and station-keeping. For higher power missions, the system would be clustered. Commercial applications for a clustered system include a small electric upper-stage. Other applications include a system for de-orbiting spacecraft that have reached their end of life.

This is early/mid-stage (TRL 5) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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