Space Station Electrical Power System Research Articles

Modeling and simulation of the International Space Station (ISS) electrical power system

Modeling and simulation of the International Space Station (<scp>ISS</scp>) electrical power system

Operational Workarounds for the Space Station Beta Gimbal Anomaly

The International Space Station (ISS) is the largest and most complex spacecraft ever assembled and operated in orbit. The first U.S. photovoltaic module, containing two solar arrays, was launched, installed, and activated in early December 2000. After the first week of continuously rotating the U.S. solar arrays, engineering personnel in the International Space Station Mission Evaluation Room observed higher than expected electrical currents on the drive motor in one of the beta gimbal assemblies, the mechanism used to maneuver a U.S. solar array. The magnitude of the motor currents continued to increase over time on both beta gimbal assemblies, creating concerns about the ability of the gimbals to continue pointing the solar arrays towards the sun, a function critical for continued assembly of the ISS. A number of engineering disciplines convened in May 2001 to address this on-orbit hardware anomaly. This paper reviews the International Space Station electrical power system analyses performed to develop viable operational workarounds that would minimize beta gimbal assembly use while maintaining sufficient solar-array power to continue assembly of the International Space Station. Additionally, electrical power system analyses performed in support of on-orbit beta gimbal assembly troubleshooting exercises are reviewed.

Stability Analysis for a Large-scale Space Power Network, International Space Station and Japanese Experiment Module

The International Space Station (ISS), which is scheduled to start the operation fully in early 2000’s, is being developed and assembled on orbit since 1998 with international cooperation of the USA, Russia, Europe, Canada, and Japan. Japan participates in this ISS program and will provide the Japanese Experiment Module (JEM, named “Kibo") which will be attached to the ISS core. Japan Aerospace Exploration Agency (JAXA), which is responsible for the JEM system development and integration, has been developed JEM Electric Power System (JEM EPS) as part of the Space Station Electric Power System (EPS). The International Space Station Electric Power System is the world’s largest orbiting direct-current (DC) power system. The ISS electric power is generated by solar arrays, and distributed to the each module in 120 Vdc bus voltage rating. When designing a large-scale Space Power System using direct current (DC), special attention must be placed on the electrical stability and control of the system and individual load on the system. For a large-scale Space Power System, it is not feasible to design the entire system as a whole. Instead, the system can be defined in term of numerous small blocks, and each block then designed individually. The individual blocks are then integrated to form a complete system. The International Space Station (ISS) is one of good example for these issue and concerns as a large-scale Space Power System. This paper describes the approach of the stability analysis for a large-scale space power network.

Space-Station nickel-hydrogen battery orbital replacement unit test

The International Space Station electrical power system utilizes nickel-hydrogen (Ni-H2) batteries as part of its power system to store electrical energy. The batteries are charged during insolation and discharged during eclipse. The batteries are designed to operate at a 35% depth of discharge maximum during normal operation. Thirty-eight individual pressure vessel Ni-H2 battery cells are series-connected and packaged in an orbit replacement unit (ORU). Two ORUs are series connected, a total of 76 cells, to form one battery. The International Space Station will be the first application for low Earth orbit cycling of this quantity of series connected cells. The Space Station Photovoltaic Electronics Team, consisting of NASA and Rocketdyne personnel, began a unique test program at the Power Systems Facility at the NASA Lewis Research Center. The test plan was created to evaluate near- and long-term performance as a battery as well as charge management characteristics. The testing would also validate the ORU configuration including the ORU box and thermal interface design. This article describes the test program and the results of the 3000 LEO cycles on a Space Station engineering model battery.

Current status, architecture, and future technologies for the International Space Station electric power system

The Electric Power System (EPS) being built for the International Space Station has undergone several significant changes over the last year, as major design decisions have been made for the overall station. While the basic topology and system elements have remained the same, there are important differences in connectivity, assembly sequence, and start-up. The key drivers for these changes in architecture have been the goal to simplify verification, and most significantly, the introduction of extensive Russian participation in the program. Having the Russians join the international community in this project has resulted in an expanded station size, larger crew, and almost doubled the observable surface of the Earth covered by the station. For the power system it has meant additional interfaces for power transfer, and new challenges for solar tracking at the higher inclination orbit. This paper reviews the current architecture and emphasizes the new features that have evolved, as the design for the new, larger station has developed. Additionally, the possible application of developing technology to the station, and other future missions is considered.

Modeling the protection system components of the space station electric power system

To facilitate protection system studies on the space station electric power system, there is a need to develop a model that can accurately and conveniently simulate both the power system and the protection system. Models for two major protective devices, the remote bus isolator and the remote power controller, are described. These models have been installed in a power system model resembling one channel of the space station power system. The usefulness of these models in protection system studies Is demonstrated. >