Integration of Large Power Systems into Manned Space Stations

Essential design factors and system characteristics are explored for integration of large power systems into manned space stations. The impact of the type of power system selected upon the space station is outlined, as is the impact of the mission requirements upon the selection of power systems. Criteria for resolving the selection/application/ integration problems are provided. Comparisons between systems are based on recently defined space-station models for 90-day to five-year mission durations in the 1970' s, with four-to nine-man crews. Power systems encompass power levels from 3 to 50 kWe and include solar cell/battery. fuel cell, hybrid fuel cell/solar cell, radioisotope, and nuclear reactor systems. Thermoelectric, Brayton cycle, organic Rankine, and liquid-metal Rankine power conversion systems are considered for the nuclear energy sources. Both rigid and roll-out photovoltaic array configurations are analyzed with respect to the solar energy source.     

Energy and power

Energy sources for aerospace systems include electrochemicals, mechanical rotation, solar illumination, radioisotopes, and nuclear reactors. Energy is converted to power with engines, turbines, photovoltaics, thermoelectric and thermionic devices, and electrochemical processes. Although some early spacecraft flew with battery power, for longer flights the choice has been either solar or nuclear. Manned spacecraft must have power for the total mission duration including boost into orbit, on-orbit, and subsequent re-entry. Batteries are too heavy for extended manned space missions; tradeoff study alternatives range from radioisotope heated thermionic converters to hyperbolic-fueled engines. Arrays of solar cells are the obvious choice for powering space stations and for other extended-duration missions. This article emphasizes developments for space and airplane power systems. Enabling technologies are described along with significant spin-offs and future systems     

薄膜太阳能电池光电转换材料研究进展

在对太阳能电池基本原理进行介绍的基础上,综述了近年来光电转换材料的发展情况,重点对各种材料的优缺点、制备方法以及未来的发展趋势进行探讨。     

考虑局部遮挡的太阳能无人机能源控制

针对太阳能无人机在飞行状态下可能出现的太阳能电池局部遮挡情况，开展相应的太阳能电池最大功率点追踪算法和能源控制研究。通过将发光亮度引入相对吸引力计算过程对萤火虫算法进行改进，实现了局部阴影情况下太阳能电池最大功率点的高效追踪。以此为基础，设计了考虑局部遮挡情况下太阳能无人机的太阳能电池/蓄电池混合能源状态机控制规则。以"蒲公英I"无人机为例，建立了太阳能电池阵列模型，开展了考虑局部遮挡情况下太阳能电池最大功率点追踪仿真实验；基于"蒲公英I"飞行剖面，开展了考虑局部遮挡情况的混合能源控制仿真试验。研究结果表明：改进的萤火虫算法可以实现在局部阴影情况下太阳能电池最大功率点的有效跟踪，与萤火虫算法相比收敛时间更短、且功率波动幅度更小；采用改进萤火虫算法和状态机能源管理策略，在考虑局部遮挡的飞行状态下可以实现太阳能电池/蓄电池之间的合理功率分配与控制。     

The stretched lens array (SLA) [spacecraft solar power]

At IECEC 2001, this team presented a paper on the new stretched lens array (SLA), including its evolution from the successful SCARLET array on the NASA/JPL Deep Space 1 spacecraft. Since that conference, the SLA team has made significant advances in SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper describes the evolved version of the SLA, highlighting recent improvements in the lens, solar cell, photovoltaic receiver, rigid panel structure, and complete solar array wing. In addition to excellent durability in the space environment, the near-term SLA will provide outstanding wing-level performance parameters: 180 W/kg specific power; 300 W/m/sup 2/ power density; 300 V operational voltage; 85% savings in cell area (cm/sup 2//W) and cell-related cost ($/W) compared to planar arrays; 9 kW/m/sup 3/ stowed power at launch.     

The space performance of silicon vertical junction solar cells onthe LIPS-III satellite

The authors present the preliminary analysis and results of a space experiment to evaluate the performance of a new generation of silicon vertical junction solar cells and three adhesives for attaching coverglass to the solar cells. Two of the adhesives are used for the first time in coverglass applications in the space environment. The SOLAREX vertical junction solar cells, which are of 10-Ω-cm silicon with back surface fields (BSFs) and back surface reflectors (BSRs) are compared to SOLAREX planar junction cells, also of 10-Ω-cm, BSF, BSR silicon. The results up to 386 days in space indicate that the two types of solar cell show about the same degradation rate in power output. There are no significant differences at this point in the performances of the three different adhesives     

Future trends in space photovoltaics

The Air Force, NASA, NRL and the commercial sector are all using small spacecraft to a greater extent in order to provide more cost-effective access to space. This paper discusses the generic photovoltaic technologies which are being studied and/or developed to support these smaller spacecraft, and identifies several specific examples. The unique requirements of these mission types include lower power arrays, arrays with lower mass and stowed volume which will be more compatible with small launch vehicles, and power systems with lower fabrication costs     

Tandem solar cells with 31% (AM0) and 37% (AM1.5D) energyconversion efficiencies

The authors demonstrate that the efficiency of GaAs satellite solar cells can be increased to 31% (AM0) with two straightforward modifications. First, the wire grid reflection losses on the GaAs cell can be eliminated by attaching and aligning a thin grooved cover slide. The grooves in this cover slide deflect the incident light rays away from the wire grid lines into the cell active area, increasing the efficiency from 22% to 24%. The second modification involves making the GaAs cell transparent to the infrared energy that normally is wasted and then placing an infrared sensitive GaSb booster cell behind the GaAs cell. This increases the AM0 solar energy conversion efficiency from 24% to 31%. The GaAs/GaSb tandem solar cells have conversion efficiencies of 37% if used for terrestrial (AM1.5) rather than space (AM0) solar electric power systems, high enough that utility-scale solar electric power may someday be economical     

太空环境下电子束原位制造技术

美国国家航空航天局（NASA）载人探索计划的提出给载人登月和载人火星等带来了机会和风险,NASA的工程师和科学家正在开展在月球或火星表面利用当地提炼的材料进行原位制造工艺技术的研究。首先,介绍了太空原位制造和修复（ISFR）技术的概念和特点,结合该技术的发展背景,介绍了电子束原位制造技术的概念、特点以及在太空环境下应用的优势和潜力。然后,根据所用原材料和成形工艺原理的不同,电子束原位制造技术又分为电子束熔融（EBM）和电子束自由成形制造（EBF³）技术两个分支,分别介绍了这两个分支技术的概念、原理、特点以及采用该技术研制出的零件的性能,结合硬件设备的情况介绍了在太空环境下应用的适用性,同时也详细介绍了NASA利用兰利研究中心的C-9抛物线飞行试验系统进行电子束原位制造微重力试验的研究成果、试验数据和未来的发展趋势。最后,结合中国未来空间事业发展的需要,提出了关于发展太空环境下电子束原位制造技术的设想与建议。     

High-efficiency GaInP/GaAs tandem solar cells

GaInP/GaAs tandem solar cells have achieved new record efficiencies, specifically 25.7% under air-mass 0 (AMO) illumination, 29.5% under AM 1.5 global (AM1.5G) illumination, and 30.2% at 140-180x concentration under AM 1.5 direct (AM1.5D) illumination. These values are the highest two-terminal efficiencies achieved by any solar cell under these illumination conditions. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance     

Review of Radiation Damage to Silicon Solar Cells

This paper reviews a large number of silicon solar cell irradiation experiments performed over the last 10 years, including 1-MeV and energy spectrum electron studies, and low-(100-keV) and high-energy (up to 155-MeV) proton studies on bare and covered silicon solar cells of several types. The results of satellite flight experiments on individual solar cells are also presented, as well as data from complete solar arrays and data on the new high-efficiency solar cells. Experimental evidence indicates that the percentage of degradation is smaller in thin solar cells than in thick ones, and that cells with high resistivity (10 ?·cm) degrade less than cells with lower resistivity (1 ?·cm). It is shown that high-efficiency silicon solar cells produced at COMSAT Laboratories and pilot production groups of these cells retain most of their increased power output under irradiation. It is emphasized that all surfaces and edges of the solar cells must be completely shielded from the large flux protons in the space environment. Insufficiencies in the published data are noted in certain areas, and recommendations for additional research are presented. Finally, an extensive bibliography is included.     

Parametric cost model for solar space power and DIPS systems

A detailed cost model has been developed to parametrically determine the program development and production cost of photovoltaic, solar dynamic, and dynamic isotope (DIPS) space power systems. The model is applicable in the net electrical power range of 3 to 300 kWe for solar power and 0.5 to 10 kWe for DIPS. Application of the cost model allows spacecraft or space-based power system architecture and design trade studies or budgetary forecasting and cost benefit analyses. The cost model considers all major power subsystems (i.e., power generation, power conversion, energy storage, thermal management, and power management/distribution/control). It also considers system cost effects such as integration, testing, and management. The cost breakdown structure, model assumptions, ground rules, bases, cost estimation relationship format, and rationale are presented, and the application of the cost model to 100-kWe solar space power plants and to a 1.0-kWe DIPS is demonstrated     

高性能树脂基体的最新研究进展

高性能热固性树脂是航空航天、交通及微电子等领域重要的基础材料。本文论述了国内外主要的高性能热固性树脂,如双马来酰亚胺树脂、聚酰亚胺树脂、氰酸酯树脂、邻苯二甲腈树脂、聚三唑树脂和有机/无机杂化树脂的研究和应用现状,并提出相应的发展趋势。     

Wireless power transmission: the key to solar power satellites

Maturing of the enabling technologies has provided much of the infrastructure to support the development of a commercial Solar Power Satellite program. Solar Space Industries was formed to accomplish this goal. The basis of their development plan is to build a Ground Test Installation that will duplicate, in small scale on the Earth, all aspects of the power generating and power transmission systems except for the space environment and the range and size of the energy beam. Space operations issues will be separated from the power generation fixation and verified by testing. Doing the developmental testing on the ground instead of in space will result in a low cost program that can be accomplished in a very short time. The concept is to build a Ground Test Installation that couples an existing 100 kW terrestrial solar cell array to a phased-array wireless power transmitter based on a subarray. Power will be transmitted over a 1-¼ mile range to a receiving antenna and then fed into a commercial utility power grid. The objective is to demonstrate the complete function of the Solar Power Satellites, with the primary issue being the validation of practical wireless power transmission. The key features to demonstrate are: beam control, stability, steering, efficiency, reliability, cost, and safety     

Flywheel technology: past, present, and 21st century projections

This paper describes the present status of flywheel energy storage technology, or mechanical batteries, and discusses realistic future projections that are possible based on stronger composite materials and advancing technology. The origins and use of flywheel technology for mechanical energy storage began several hundred years ago and was developed throughout the Industrial Revolution. One of the first “modern” dissertations on the theoretical stress limitations of rotational disks (isotropic only) is the seminal work by A. Stodola whose first translation to English was made in 1917. The next big milestones were during the 1960s and 1970s when NASA sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980's when microelectronics, magnetic bearing systems and high power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications     

Applications of Brayton cycle technology to space power

The Closed Brayton Cycle (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat sources include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turboalternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration. applications. The CBC consists of a heater, turboalternator compressor (TAC), cooler, and recuperator. A mixture of He and Xe is used as the working fluid in the CBC system. The He provides superior heat transfer characteristics in the heater, cooler, and recuperator. The Xe adjusts the molecular weight to provide superior aerodynamic performance for maximized turbine and compressor efficiency. Cycle studies are performed to select the optimum He/Xe molecular weight or He to Xe mixture ratio. The following presents the characteristics and advantages of using the CBC for space power applications, CBC development status, characteristics and applications of the CBC with each of the heat sources, and finally performance projections     

Space power systems requirements and issues: the next decade

Some of the more important space power technology issues, requirements, and challenges of the 1990s are described, and the impact of new component technology on the overall performance of space power systems is assessed. Advanced component, subsystem and system technologies that will significantly affect the performance, reliability, and survivability of next-generation baseload and burst mode space power systems are emphasized. Technology disciplines related to power sources (solar/nuclear and chemical), power conversion, energy storage, power conditioning/distribution and control, and waste-heat acquisition, transport, and rejection are primarily addressed. For some of them, performance trends that can be used as the basis for projecting future advanced power-system performance are developed. Performance capabilities for several different types of space power system for both baseload and burst mode applications are postulated on the basis of evolving technology and point designs that incorporate projections of advanced component capabilities     

ATS-6 Solar Cell Flight Experiment After 325 Days in Synchronous Orbit

Preliminary Applications Technology Satellite-6 (ATS-6) solar cell flight experiment data through the first 325 days in synchronous orbit is present. The experiment is transmitting data on 16 different solar cell/cover glass configurations. The experiment is designed to study the effect of this orbit on select solar cells and cover glass parameters such as solar cell thickness and base resistivity, cover glass thickness variation, new cover and adhesive processes and materials such as 7940 and 7070 integral covers and the fluorinated ethylene propylene (FEP) covers, the COMSAT "violet" cell, and backside irradiation effects. The in-spece solar cell data indicate short circuit currents are higher by 1 to 8 percent than measurements made with solar simulations; maximum power varied between -1 to +6 percent . Degradation of /sc due to ultraviolet effects was determined to be about 2 percent after 50 days in orbit. All cells performed well through 325 days in orbit, except the FEP-covered cells, which appear to have increased their rate of degradation during the first eclipse season.     

Flexible Solar Cell Arrays for Increased Space Power

The importance of solar cells for space power supplies continues with increased emphasis. The need for advances in the design of solar cell arrays becomes more pressing as the requirement for increased power levels is apparent. This paper discusses a flexible solar cell concept, includes a brief history of the development, describes a conceptual design for a 20-kW array, giving weight breakdown, and describes an existing design effort.