James H. Matsumoto

Lithium ion battery performance and charge control

This paper presents the initial results from testing of SONY US18650B Li-ion cells from 0 to 40/spl deg/C. Charge rates from C/10 to C/1.4 and discharge rates of C/2.4 to C/0.8 have been studied, which covers 24% to 70% depth-of-discharge (DOD) in simulated low Earth orbit (LEO). When cells are rated at the capacity delivered to 3.00 V at the C/2 rate, following a C/10 charge to 4.07 V at 20/spl deg/C, the specific energy of the cells is 70 Wh/kg. This specific energy is significantly higher than the specific energy of Ni-H/sub 2/ cells. The preferred operating temperature range for these cells is 10 to 30/spl deg/C. Constant current charging to a battery voltage was effective, and this method of charge control may be adequate for short life missions with eight series cell batteries. For longer life missions, it will probably be desirable to supplement available current limited, constant potential battery charging with small electronic circuits to assure no cell exceeds the charge voltage maximum.

Rate coefficients for the reactions of BF with O and O2

Abstract Bimolecular reaction rate coefficients of k = (1.4 ± 0.2) × 10 −10 and −17 cm 3 /molecule s have been measured at T = 294 K in a flowtube facility for BF + O → BO + F and BF + O 2 → products, respectively. These results are discussed in terins of the electronic structure of boron monofluoride.

Advancements in the development of thin film amorphous silicon space solar cell for the PowerSphere concept

The authors describe how the development of the PowerSphere concept over the last year focused on the design and fabrication of amorphous silicon solar cells that would meet the space environmental requirements. This is a cooperative effort between The Aerospace Corporation and Iowa Thin Film Technologies, Inc. Modifications to the terrestrial product line necessary to produce a thin film amorphous silicon solar cell suitable for space applications have been identified. A number of experiments have been performed in The Aerospace Corporations Laboratories to develop a more robust top contact to collect cell current for the otherwise terrestrial cell produced by Iowa Thin Film Technologies production line. The up-to-date results of this effort are presented in this paper.

Engineering Development Model Testing of the PowerSphere

The Aerospace Corporation, NASA Glenn Research Center, Lockheed-Martin, and ILC Dover over the past two years have been engaged in developing a Multifunctional Inflatable Structure for the PowerSphere Concept under contract with NASA (NAS3-01115). The PowerSphere concept consists of a relatively large spherical solar array, which would be deployed from a micro satellite. 1–8 The PowerSphere structure and the deployment method was patented by the Aerospace Corporation (U.S. Patent Numbers 6,284,966 B1 and 6,318,675). The work on this project has resulted in a number of technological innovations in the state of the art for integrating flexible thin-film solar cells with flex circuit harness technology and inflatable ultraviolet-light-rigidizable structures.

Development of flex circuit wiring harness for the PowerSphere concept

The PowerSphere is a spherical solar array designed to power small satellites. The spherical shape allows the uniform collection of solar energy without regards to orientation to the sun. The PowerSphere is a geodetic sphere which uniquely incorporates thin film solar cells, ultra light deployable structures/mechanisms, and flexible circuits and inter-connect technologies. The focus of this paper will be on the on-going efforts to integrate flexible circuits and inter-connect technologies with the thin film solar cells and ultra light deployable structure.

Fabrication and Testing of a PowerSphere Engineering Development Unit

During the past three years the team of The Aerospace Corporation, Lockheed Martin Space Systems, NASA Glenn Research Center, and ILC Dover LP have been developing a multifunctional inflatable structure for the PowerSphere concept under contract with NASA (NAS3-01115). The PowerSphere attitude insensitive solar power-generating microsatellite, which could be used for many different space and Earth science purposes as discussed elsewhere, is ready for further refinement and flight demonstration. The project culminated during the third year with the manufacturing of the Powersphere Engineering Development Unit (EDU). One hemisphere of the EDU system was tested for packing and deployment and was subsequently rigidized. The other hemisphere was packed and stored for future testing in an uncured state. Both cured and uncured hemisphere components were delivered to NASA Glenn Research Center for thermal cycle testing and long term storage respectively. This paper will discuss the design, manufacturing, and thermal cycle testing of the PowerSphere EDU. The program also had a significant Education Outreach segment that will also be discussed.

Powersphere Power System demonstration station

The PowerSphere Power System, and in particular, its power management and distribution (PMAD) architecture was conceived to be a solution to provide adequate power for micro-satellite and nano-satellite spacecrafts. The PowerSphere Power System, which was introduced at the 1999 IECEC in the Aerospace Power Management Session, is a means to deploy a large area of thin film solar cells with minimum weight on a sphere that requires no pointing and that can be sized for various desired power levels. This paper reports on the PMAD architecture for the electrical property characterization of a typical DC-DC converter chosen for the PowerSphere Power System. The solar array portion of the development station consists of a combination of 32 pentagonal and hexagonal shaped thin-film amorphous silicon solar cells mounted on an aluminum buckyball sphere approximately two feet in diameter. The buckyball sphere is mounted on a motorized drive mechanism to provide some degree of rotational movement, limited only by the wiring harness. The solar cells are electrically connected in pairs so those on opposite faces feed an individual integrated circuit DC-DC converter unit.

Self-discharge characteristics of spacecraft nickel—cadmium cells at elevated temperatures

Abstract It is shown that thermal runaway can occur from self-discharge of sealed NiCd batteries at elevated temperatures. The process can be fast enoug