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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

The NEXT-C Power Processing Unit: Lessons Learned from the Design, Build, and Test of the NEXT-C PPU for APL's DART Mission

NASA’s Double Asteroid Redirection Test (DART) will be the first-ever planetary defense mission to demonstrate asteroid deflection using kinetic impactor technology. The DART spacecraft will utilize the NASA Evolutionary Xenon Thruster (NEXT), which is a successor to the NSTAR ion propulsion system that successfully propelled NASA’s Deep Space 1 and Dawn spacecraft. In 2015, NASA partnered with Aerojet Rocketdyne and ZIN Technologies on the NEXT-Commercial (NEXT-C) effort to manufacture a Flight-Qualified (TRL 8) power processing unit (PPU). The NEXT-C PPU was based on the heritage gridded ion thruster PPU from NSTAR and NEXT, but with significant improvements in performance and manufacturability. The design goals of the NEXT-C PPU were to achieve the technical performance goals of the PPU in size, mass, and efficiency over a wide range of input voltage and output power. This paper discusses the lessons learned from the design, build, and test of the NEXT-C PPU, and how challenges were overcome to deliver a Flight PPU.

NEXT-C↗
NASA NTRSDate not supplied

The NEXT-C Power Processing Unit: Lessons Learned from the Design, Build, and Test of the NEXT-C PPU for APL's DART Mission

NASA’s Double Asteroid Redirection Test (DART) will be the first-ever planetary defense mission to demonstrate asteroid deflection using kinetic impactor technology. The DART spacecraft will utilize the NASA Evolutionary Xenon Thruster (NEXT), which is a successor to the NSTAR ion propulsion system that successfully propelled NASA’s Deep Space 1 and Dawn spacecraft. In 2015, NASA partnered with Aerojet Rocketdyne and ZIN Technologies on the NEXT-Commercial (NEXT-C) effort to manufacture a Flight-Qualified (TRL 8) power processing unit (PPU). The NEXT-C PPU was based on the heritage gridded ion thruster PPU from NSTAR and NEXT, but with significant improvements in performance and manufacturability. The design goals of the NEXT-C PPU were to achieve the technical performance goals of the PPU in size, mass, and efficiency over a wide range of input voltage and output power. This paper discusses the lessons learned from the design, build, and test of the NEXT-C PPU, and how challenges were overcome to deliver a Flight PPU.

NEXT-C↗
NASA NTRS2016

Performance of a High-Fidelity 4kW-Class Engineering Model PPU and Integration with HiVHAc System

The High Voltage Hall Accelerator (HiVHAc) propulsion system consists of a thruster, power processing unit (PPU), and propellant feed system. An engineering model PPU was developed by Colorado Power Electronics, Inc. funded by NASA's Small Business Innovative Research Program. This PPU uses an innovative 3-phase resonant converter to deliver 4 kW of discharge power over a wide range of input and output voltage conditions. The PPU includes a digital control interface unit that automatically controls the PPU and a xenon flow control module (XFCM). It interfaces with a control computer to receive highlevel commands and relay telemetry through a MIL-STD-1553B interface. The EM PPU was thoroughly tested at GRC for functionality and performance at temperature limits and demonstrated total efficiencies a high as 95 percent. Integrated testing of the unit was performed with the HiVHAc thruster and the XFCM to demonstrate closed-loop control of discharge current with anode flow. Initiation of the main discharge and power throttling were also successfully demonstrated and discharge oscillations were characterized.

Power Processing Unit↗
NASA NTRS2016

Performance of a High-Fidelity 4kW-Class Engineering Model PPU and Integration with HiVHAc System

The High Voltage Hall Accelerator (HiVHAc) propulsion system consists of a thruster,power processing unit (PPU), and propellant feed system. An engineering model PPU was developed by Colorado Power Electronics, Inc. funded by NASA's Small Business Innovative Research Program. This PPU uses an innovative 3-phase resonant converter to deliver 4 kW of discharge power over a wide range of input and output voltage conditions.The PPU includes a digital control interface unit that automatically controls the PPU and a xenon flow control module (XFCM). It interfaces with a control computer to receive high level commands and relay telemetry through a MIL-STD-1553B interface. The EM PPU was thoroughly tested at GRC for functionality and performance at temperature extremes and demonstrated total efficiencies a high as 95 percent. It was integrated with the HiVHAc thruster and the XFCM to demonstrate closed-loop control of discharge current with anode flow. Initiation of the main discharge and power throttling were also successfully demonstrated and discharge oscillations were characterized.

Electric Propulsion↗
NASA NTRS2012

NASA's Evolutionary Xenon Thruster (NEXT) Power Processing Unit (PPU) Capacitor Failure Root Cause Analysis

The NASA s Evolutionary Xenon Thruster (NEXT) project is developing an advanced ion propulsion system for future NASA missions for solar system exploration. A critical element of the propulsion system is the Power Processing Unit (PPU) which supplies regulated power to the key components of the thruster. The PPU contains six different power supplies including the beam, discharge, discharge heater, neutralizer, neutralizer heater, and accelerator supplies. The beam supply is the largest and processes up to 93+% of the power. The NEXT PPU had been operated for approximately 200+ hr and has experienced a series of three capacitor failures in the beam supply. The capacitors are in the same, nominally non-critical location-the input filter capacitor to a full wave switching inverter. The three failures occurred after about 20, 30, and 135 hr of operation. This paper provides background on the NEXT PPU and the capacitor failures. It discusses the failure investigation approach, the beam supply power switching topology and its operating modes, capacitor characteristics and circuit testing. Finally, it identifies root cause of the failures to be the unusual confluence of circuit switching frequency, the physical layout of the power circuits, and the characteristics of the capacitor.

Soeder, James F.↗
NASA NTRS2012

NASA's Evolutionary Xenon Thruster (NEXT) Power Processing Unit (PPU) Capacitor Failure Root Cause Analysis

The NASA's Evolutionary Xenon Thruster (NEXT) project is developing an advanced ion propulsion system for future NASA missions for solar system exploration. A critical element of the propulsion system is the Power Processing Unit (PPU) which supplies regulated power to the key components of the thruster. The PPU contains six different power supplies including the beam, discharge, discharge heater, neutralizer, neutralizer heater, and accelerator supplies. The beam supply is the largest and processes up to 93+% of the power. The NEXT PPU had been operated for approximately 200+ hours and has experienced a series of three capacitor failures in the beam supply. The capacitors are in the same, nominally non-critical location the input filter capacitor to a full wave switching inverter. The three failures occurred after about 20, 30, and 135 hours of operation. This paper provides background on the NEXT PPU and the capacitor failures. It discusses the failure investigation approach, the beam supply power switching topology and its operating modes, capacitor characteristics and circuit testing. Finally, it identifies root cause of the failures to be the unusual confluence of circuit switching frequency, the physical layout of the power circuits, and the characteristics of the capacitor.

Soeder, James F.↗
NASA NTRS2013

High Temperature Boost (HTB) Power Processing Unit (PPU) Formulation Study

This technical memorandum is to summarize the Formulation Study conducted during fiscal year 2012 on the High Temperature Boost (HTB) Power Processing Unit (PPU). The effort is authorized and supported by the Game Changing Technology Division, NASA Office of the Chief Technologist. NASA center participation during the formulation includes LaRC, KSC and JPL. The Formulation Study continues into fiscal year 2013. The formulation study has focused on the power processing unit. The team has proposed a modular, power scalable, and new technology enabled High Temperature Boost (HTB) PPU, which has 5-10X improvement in PPU specific power/mass and over 30% in-space solar electric system mass saving.

Chen, Yuan↗
NASA NTRS2015

Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters

Arkansas Power Electronics International (APEI), Inc., is developing a high-efficiency, radiation-hardened 3.8-kW SiC power supply for the PPU of Hall effect thrusters. This project specifically targets the design of a PPU for the high-voltage Hall accelerator (HiVHAC) thruster, with target specifications of 80- to 160-V input, 200- to 700-V/5A output, efficiency greater than 96 percent, and peak power density in excess of 2.5 kW/kg. The PPU under development uses SiC junction field-effect transistor power switches, components that APEI, Inc., has irradiated under total ionizing dose conditions to greater than 3 MRad with little to no change in device performance.

Reese, Bradley↗
NASA NTRS2007

Performance of the NEXT Engineering Model Power Processing Unit

The NASA s Evolutionary Xenon Thruster (NEXT) project is developing an advanced ion propulsion system for future NASA missions for solar system exploration. An engineering model (EM) power processing unit (PPU) for the NEXT project was designed and fabricated by L-3 Communications under contract with NASA Glenn Research Center (GRC). This modular PPU is capable of processing up from 0.5 to 7.0 kW of output power for the NEXT ion thruster. Its design includes many significant improvements for better performance over the state-of-the-art PPU. The most significant difference is the beam supply which is comprised of six modules and capable of very efficient operation through a wide voltage range because of innovative features like dual controls, module addressing, and a high current mode. The low voltage power supplies are based on elements of the previously validated NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) PPU. The highly modular construction of the PPU resulted in improved manufacturability, simpler scalability, and lower cost. This paper describes the design of the EM PPU and the results of the bench-top performance tests.

Pinero, Luis R.↗
NASA NTRS2016

High Temperature Boost (HTB) Anode Power Supply for a Modular and Scalable Power Processing Unit

A concept of a modular and scalable 10kW to 80kW High Temperature Boost (HTB) Power Processing Unit (PPU) capable of operating at temperatures beyond the standard military temperature range was proposed for solar electric in-space propulsion. Within the PPU, the Anode Power Supply (APS) module is a 10kW modular power stage and is the key to the HTB PPU. This paper is to present the design, development, fabrication, testing and thermal demonstration of the 10kW HTB APS. The system architecture and the paradigm shift of the HTB PPU is also to be described. In addition, the extreme environments electronic and packaging technologies are addressed as the fundamental technology path. The HTB PPU is intended for power processing in the area of space solar electric propulsion, where reduction of in-space mass and volume are desired, and sometimes even critical, to achieve the goals of future space flight missions. The concept of the HTB PPU can also be applied to other extreme environment applications, such as geothermal and petroleum deep-well drilling, where higher temperature operation is required.

Carr, Gregory A.↗
NASA NTRS1995

Development Status of the NSTAR Ion Propulsion System Power Processor

A 0.5-2.3 kW xenon ion propulsion system is presently being developed under the NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) program. This propulsion system includes a 30 cm diameter xenon ion thruster, a Digital Control Interface Unit, a xenon feed system, and a power processing unit (PPU). The PPU consists of the power supply assemblies which operate the thruster neutralizer, main discharge chamber, and ion optics. Also included are recycle logic and a digital microcontroller. The neutralizer and discharge power supplies employ a dual use configuration which combines the functions of two power supplies into one, significantly simplifying the PPU. Further simplification was realized by implementing a single thruster control loop which regulates the beam current via the discharge current. Continuous throttling is possible over a 0.5-2.3 kW output power range. All three power supplies have been fabricated and tested with resistive loads, and have been combined into a single breadboard unit with the recycle logic and microcontroller. All line and load regulation test results show the power supplies to be within the NSTAR flight PPU specified power output of 1.98 kW. The overall efficiency of the PPU, calculated as the combined efficiencies of the power supplies and controller, at 2.3 kW delivered to resistive loads was 0.90. The component was 6.16 kg. Integration testing of the neutralizer and discharge power supplies with a functional model thruster revealed no issues with discharge ignition or steady state operation.

Hamley, John A.↗
NASA NTRS1992

Simulating the arcjet thruster using a nonlinear active load

Arcjet thrusters are known to have distinctly nonlinear electrical characteristics with negative incremental resistance throughout their normal operating region. The 1-kW arcjet simulator proposed here accurately mimics these characteristics statically, and dynamically up to 40 kHz. Testing with a power-processing unit (PPU) and the simulator, a 1-kW arcjet, and a resistive load bank established that the simulator accurately predicted the transient behavior of the PPU-arcjet combination, while the resistive load bank did not. The simulator uses resistors and insulated-gate bipolar transistors to dissipate the PPU output power; a nonlinear feedback is applied to produce the desired v-i characteristics. This feedback is analyzed dynamically. The arcjet simulator allows development of a PPU to a higher level of confidence before beginning testing at an arcjet facility.

Altenburger, Gene P.↗
NASA NTRS1995

Direct drive options for electric propulsion systems

Power processing units (PPU's) in an electric propulsion system provide many challenging integration issues. The PPU must provide power to the electric thruster while maintaining compatibility with all of the spacecraft power and data systems. Inefficiencies in the power processor produce heat, which must be radiated to the environment in order to ensure reliable operation. Although PPU efficiencies are generally greater than 0.9, heat loads are often substantial. This heat must be rejected by thermal control systems which generally have specific masses of 15-30 kg/kW. PPU's also represent a large fraction of the electric propulsion system dry mass. Simplification or elimination of power processing in a propulsion system would reduce the electric propulsion system specific mass and improve the overall reliability and performance. A direct drive system would eliminate all or some of the power supplies required to operate a thruster by directly connecting the various thruster loads to the solar array. The development of concentrator solar arrays has enabled power bus voltages in excess of 300 V which is high enough for direct drive applications for Hall thrusters such as the Stationary Plasma Thruster (SPT). The option of solar array direct drive for SPT's is explored to provide a comparison between conventional and direct drive system mass.

Hamley, John A.↗
NASA NTRS1997

Power Electronics for a Miniaturized Arcjet

A 0.3 kW Power Processing Unit (PPU) was designed, tested on resistive loads, and then integrated with a miniaturized arcjet. The main goal of the design was to minimize size and mass while maintaining reasonable efficiency. In order to obtain the desired reductions in mass, simple topologies and control methods were considered. The PPU design incorporates a 50 kHz, current-mode-control, pulse-width-modulated (PWM), push-pull topology. An input voltage of 28 +/- 4V was chosen for compatibility with typical unregulated low voltage busses anticipated for smallsats. An efficiency of 0.90 under nominal operating conditions was obtained. The component mass of the PPU was 0.475 kg and could be improved by optimization of the output filter design. The estimated mass for a flight PPU based on this design is less than a kilogram.

Pinero, Luis R.↗
NASA NTRS2005

Development of the NEXT Power Processing Unit

Boeing Electron Dynamic Devices, Inc. (EDD) has designed and fabricated a breadboard version of a 6 kW power processing unit (PPU) for gridded ion thrusters. This breadboard PPU will be integrated with an engineering model 40 cm ion engine designed and tested at NASA Glenn. The results of our tests using resistive loads are reported in this paper. The PPU demonstrated efficiencies to date are higher than 95 percent for the beam supply and higher than 92 percent for the discharge supply at full power. Overall PPU efficiency is greater than 94 percent at full throttle settings.

Phelps, Thomas K.↗
NASA NTRS1999

Ion Thruster and Power Processor Developed for the Deep Space 1 Mission

The NASA Solar Electric Propulsion Technology Applications Readiness (NSTAR) Program has provided a single-string primary propulsion system to NASA's Deep Space 1 spacecraft. This spacecraft will carry about 81 kg of xenon propellant for the ion thruster, which can be throttled down from 2.3 to 0.5 kW as the spacecraft moves away from the Sun. The propellant load will provide about 20 months of propulsion at the one-half power throttle setpoint of 1.2 kW. This mission will validate the 2.5-kW ion propulsion system and will fly by the asteroid 1992 KD in 1999. If funding permits, Deep Space 1 also will encounter comets Wilson-Harrington and Borrelly in 2001. NASA Lewis Research Center's On-Board Propulsion Branch was responsible for the development of the 30-cm-diameter ion thruster, the 2.5-kW power processor unit (PPU), and the Digital Control and Interface Unit (DCIU) that controls the PPU/thruster/feed system and provides data and recovery from fault conditions. Lewis transferred the thruster and PPU technologies to the Hughes Electron Dynamics Division, which was selected to build two sets of flight thrusters, as well as the PPU's and DCIU's. Hughes subcontracted the DCIU development to Spectrum Astro Incorporated. The Jet Propulsion Laboratory (JPL) was primarily responsible for the NSTAR project management, thruster lifetests, the feed system, diagnostics, and the propulsion subsystem integration. A total of four engineering model thrusters and three breadboard PPU's were built, integrated, and tested. More than 50 development tests were conducted along with thruster design verification tests of 2000 and 1000 hours. In addition, an 8000-hr life demonstration test was successfully completed and demonstrated wear-rates consistent with full-power lifetimes in excess of 12,000 hours.

Sovey, James S.↗