Radioisotope AMTEC power system designs for spacecraft applications

The authors describe and compare small (two-module) and larger (16-module) AMTEC (alkali metal thermal-to-electric converter) radioisotope powered systems and describe the computer model developed to predict their performance. The high efficiency and static conversion process combined with minimized parasitic losses and operating temperatures that allow the use of current materials while still maintaining a competitive radiator area are found to make AMTEC an excellent candidate for enhanced performance space power systems. AMTEC has the capability of reducing mission costs relative to other static conversion systems because of its high efficiency. AMTEC can also reduce cost relative to dynamic systems simply by being less massive (10 to 5000 W level), and its use eliminates the torque and vibration issues of dynamic systems     

Simulation and control of a 20-kHz spacecraft power system

A detailed computer representation of four Mapham inverters connected in a series-parallel arrangement has been implemented. System performance is illustrated by computer traces for the four Mapham inverters connected to a Litz cable with parallel resistance and DC receiver loads at the receiving end of the transmission cable. Methods of voltage control and load sharing between the inverters are demonstrated. The computer representation is used to design and demonstrate the advantages of a feedforward voltage-control strategy. It is shown that with a computer simulation of this type, the performance and control of spacecraft power systems can be investigated with relative ease and facility     

Loop gain of a spacecraft switched shunt power system

A novel approach of deriving the loop gain of a spacecraft switched shunt power system is presented. The system hardware elements contain both the analog and the digital components. Transfer functions of the analog circuits are easily identified employing the conventional approach. Gain function of the digital block is however conceived following a quite unconventional route. The digital gain is shown to include the effects of comparator thresholds, digital clock, shift register, sinusoidal amplitude, and ac frequency. The dependence of the digital gain on voltage thresholds, clocking period, and the integrational property of threshold comparator is expected. The dependence on sinusoidal amplitude contradicts the traditional concept of small signal analysis. The overall loop gain in the analytic form yields a computational result that matches the actual measurement very well. This fact proves, to some extent, the validity of the digital gain function and the basis of its derivation     

Thermodynamic cycles for spacecraft power plants

A problem of applying closed multiloop thermodynamic cycles with mixing of dissimilar working gases in spacecraft power plants has been considered. The advantage of these cycles that is due to reduction of a heat quantity being rejected into space has been shown for ecologically clean generation of electric energy in prolonged space flights.     

Modeling and simulation of spacecraft power systems

Modeling of a complete spacecraft power processing system is presented, using the Boeing EASYS software. Component models are developed, and several system models including a solar array switching system, a partially shunted solar system, and cosmic background explorer (COBE) system are simulated. The modes of operation of the power system, such as shunt mode, battery-charge mode, and battery-discharge mode, are simulated for a complete orbit cycle     

浮空器太阳辐射模型研究

采用理论分析和试验测定相结合的办法,对浮空器太阳辐射进行了研究,建立太阳直射辐射模型、天空散射辐射模型和地面反射辐射模型,计算值与试验测定值吻合较好。     

Conception of spacecraft centralized power supply

A reliable power supply for spacecraft is one of the central problems determining the future development of space technology. The traditional solution to this problem implies having an autonomous power plant on board each spacecraft. The most widely used are power plants with solar cells. However, there exists an alternative power supply concept of using a centralized power supply system (CPSS) and power transmission to the user satellites by laser or microwave beams. Use of a CPSS has a number of advantages. In particular, it allows the spacecraft to increase power supply level and service life as well as to decrease the spacecraft mass and cost. However, it sets new physical and technical problems associated with long distance power transmission and requires some changes in spacecraft structure and concepts. The feasibility study of CPSS development and use has to rely on existing or firmly forecastable technologies. An attempt of such an analysis has been done by a group of scientists at Moscow State Aviation Institute during 1994-1996. The very first results have already been published. This paper discusses new results obtained lately regarding a space based CPSS     

Simulation of DC spacecraft power systems

A modular state-variable approach is presented for DC spacecraft power system modeling and simulation. Each modular component is treated as a multiport network, and a state model is written with the port voltages as the inputs. The state model of a component is solved independently of the other components, using its state transition matrix. The state variables of each component are updated, assuming that the inputs are constant. Network analysis principles are then utilized to calculate the component inputs     

Design and testing of spacecraft power systems using VTB

A study is presented on the design and testing of spacecraft power systems using the virtual test bed (VTB). The interdisciplinary components such as solar array and battery systems were first modeled in native VTB format and validated by experiment data. The shunt regulator and battery charge controller were designed in Simulink according to the system requirements and imported to VTB. Two spacecraft power systems were then designed and tested together with the control systems.     

The visible imaging system (VIS) for the polar spacecraft

The Visible Imaging System (VIS) is a set of three low-light-level cameras to be flown on the POLAR spacecraft of the Global Geospace Science (GGS) program which is an element of the International Solar-Terrestrial Physics (ISTP) campaign. Two of these cameras share primary and some secondary optics and are designed to provide images of the nighttime auroral oval at visible wavelengths. A third camera is used to monitor the directions of the fields-of-view of these sensitive auroral cameras with respect to sunlit Earth. The auroral emissions of interest include those from N ₂ ⁺ at 391.4 nm, Oi at 557.7 and 630.0 nm, Hi at 656.3 nm, and Oii at 732.0 nm. The two auroral cameras have different spatial resolutions. These resolutions are about 10 and 20 km from a spacecraft altitude of 8R _e . The time to acquire and telemeter a 256×256-pixel image is about 12 s. The primary scientific objectives of this imaging instrumentation, together with thein-situ observations from the ensemble of ISTP spacecraft, are (1) quantitative assessment of the dissipation of magnetospheric energy into the auroral ionosphere, (2) an instantaneous reference system for thein-situ measurements, (3) development of a substantial model for energy flow within the magnetosphere, (4) investigation of the topology of the magnetosphere, and (5) delineation of the responses of the magnetosphere to substorms and variable solar wind conditions.     

近地航天器量子导航定位卡尔曼滤波算法研究

针对近地航天器量子导航定位系统,为了进一步提高其定位精度,利用滤波技术将QPS测量值结合航天器的运动模型进行状态量的滤波估计.给出了基于基线干涉原理的量子定位系统观测方程和以二体运动为主的航天器轨道运动模型,在此基础上详细推导了扩展卡尔曼滤波处理过程,并针对该模型进行了仿真.仿真结果表明,基于EKF的量子导航定位精度有明显提高.     

Event-triggered and consensus-based attitude tracking alignment for discrete-time multiple spacecraft system exploiting interference

This paper presents a discrete-time attitude control strategy with equi-global practical stabilizability for aligning the attitude of multiple spacecraft to a predesigned configuration according to a time-variant reference. By utilizing the interference of the wireless channel, the communication scheme designed in this paper can save communication resources, amount of computation, and energy proportionally to the number of spacecraft. The exact discrete-time model and approximate discrete-time model of the consensus-based spacecraft tracking system are given. Then the framework for the design of an event-triggered control scheme for the exact discrete-time system via its approximate models is developed, which avoids the periodic actuation, and Zeno behavior is proved to be excluded. Furthermore, the control scheme can handle the presence of the unknown fading channel. Finally, simulation results are presented to demonstrate the effectiveness of the control strategy.     

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.     

An approach to forming the design performance of the attitude control system for small spacecraft

The elements for various types of attitude control systems used in a number of small spacecraft are considered. An approach for assessment of such system effectiveness based on design requirements for spacecraft purpose and restriction in accuracy, mass and energy is proposed.     

Solar system observations and future missions

This paper aims at placing infrared (IR) and submillimeter (submm) observations of the Solar Sytem in the context of future space missions. First, the information that mm, submm and IR observations bring on planets, satellites and comets is reviewed. Then, some lines of future research in this field are explored, and a number of observations that could enhance our understanding of Solar System objects are suggested. Finally, the adequacy of future space missions in this respect is discussed. The specific cases of ISO, FIRST and the proposed Edison are considered.     

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.     

空间飞行器实时仿真多体系统动力学建模

为了解决传统的多体系统动力学模型因必须显式表达多体系统的拓扑构型信息,使得所建数学模型非常复杂而不太适合空间任务级实时仿真的问题,针对具有中心体结构的空间飞行器,采用拟坐标拉格朗日方程推导出简洁的多体系统姿态动力学数学模型,并利用通用仿真平台建立了可实时运行的多体系统姿态动力学仿真模型.在仿真模型上施加测试用极限环控制律,模型输出正常的姿态动力学响应.仿真结果表明,所建模型在模型粒度和运行效率间取得了平衡,满足空间任务级仿真对模型逼真度和实时性的要求.     

Displacement simulation for spacecraft structure

The paper presents a technique of forming and evaluating the allowable clearance between a launch vehicle fairing and spacecraft.     

Single-phase power distribution system power flow and faultanalysis

Alternative methods for power flow and fault analysis of single-phase distribution systems are presented. The algorithms for both power flow and fault analysis utilize a generalized approach to network modeling. The generalized admittance matrix, formed using elements of linear graph theory, is an accurate network model for all possible single-phase network configurations. Unlike the standard nodal admittance matrix formulation algorithms, the generalized approach uses generalized component models for the transmission line and transformer. The standard assumption of a common node voltage reference point is not required to construct the generalized admittance matrix. Therefore, truly accurate simulation results can be obtained for networks that cannot be modeled using traditional techniques