共查询到20条相似文献,搜索用时 15 毫秒
1.
为有效解决在日蚀区太阳能热推进器推力失效、电力中断的问题,提出了蓄热式太阳能热光伏-热推进双模系统结构,并对系统各部件建立相关物理数学模型,分析了工质种类、工质流量等因素对推进性能的影响。结果表明,为保证推进器在日蚀区30min内持续提供推力和电力供应,砷化镓热光伏电池在无工质工况下能提供10W左右的低功率电力供应,在设计工况下能提供50W~110W的电力供应;液氢作为工质时,最大比冲将达到806s,随着工质流量的持续增加,比冲损失速率呈现先加快后减慢的变化趋势;液氨作为替代工质具有更快的加热速率,其比冲为240s~300s远低于氢工质比冲,其推力系数1.77要略高于氢工质推力系数1.7。通过本文研究,蓄热式太阳能双模推进系统具有较好的可行性,且推力及比冲适中,有望弥补低比冲化学推进和小推力电推进技术的不足。 相似文献
2.
A 1984 survey of the nickel hydrogen (NiH2) battery industry is updated. Late 1980s and early 1990s issues are identified, and usage and testing results of the survey are summarized. NiH2 is the system of choice for new geosynchronous-earth-orbit (GEO) satellites and is being seriously considered for low-earth-orbit (LEO) applications. In five years, the annual cell production rate has doubled from approximately 1000 to 2000 cells. A number of cells under test have exceeded 20000 cycles at 40% DOD in LEO regimes, while other cells have achieved over 35 seasons in accelerated GEO regimes. The LEO database clearly indicates that NiH2 performance is at least as good as the best conventional nickel-cadmium performance demonstrated under test 相似文献
3.
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. 相似文献
4.
EXOSAT observed LMC X-4 on November 17/19, 1983 for one 1.4 day binary period during the high state of the 30.5 day cycle. An eclipse with sharp ingress and slow egress was detected with an eclipse angle of 27.1±1.0 dgr. In the medium energy experiment the source showed a hard power law spectrum. Outside eclipse the source was remarkably constant and only one flare was detected on November 17 at 19 UT lasting for about 1 h. The energy spectrum of the source softens considerably during that time and shows an emission line of cold iron. 13.5 sec pulsations are strongly present during the flare and have also been detected during the quiescent period and during several 1 min flares in another EXOSAT LMC X-4 observation on November 22, 1983. A pulse delay time analysis results in the determination of the pulse period (13.5019±0.0002) s and of the semimajor axis of the orbit of the X-ray star (26.0±0.6) It-sec. These results, together with other available information on LMC X-4, allowed to improve the binary parameters. The mass of the neutron star is found to be 1.34
±0.44
0.48
Mo (95% confidence errors). 相似文献
5.
Kuo-Ying Wang Chao-Han Liu Lou-Chuang Lee Peter Braesicke 《Space Science Reviews》2012,168(1-4):261-282
Sudden tropospheric cooling and induced stratospheric warming were found during the 22 July 2009 total solar eclipse. Can the 22 July 2009 hallmark also be seen in other major solar eclipses? Here we hypothesize that the tropospheric cooling and the stratospheric warming can be predicted to occur during a major solar eclipse event. In this work we use the FORMOSAT-3/COSMIC (F3C) Global Positioning System (GPS) radio occultation (RO) data to construct eclipse-time temperature profiles before, during, and after the passages of major solar eclipses for the years 2006–2010. We use four times a day of meteorological analysis from the European Centre for Medium Range Weather Forecast (ECMWF) global meteorological analysis to construct non-eclipse effect temperature profiles for the same eclipse passages. The eclipse effects were calculated based on the difference between F3C and ECMWF profiles. A?total of five eclipse cases and thirteen non-eclipse cases were analyzed and compared. We found that eclipses cause direct thermal cooling in the troposphere and indirect dynamic warming in the stratosphere. These results are statistically significant. Our results show ?0.6 to ?1.2°C cooling in the troposphere and 0.4 to 1.3°C warming in the middle to lower stratosphere during the eclipses. This characteristic stratosphere-troposphere coupling in temperature profiles represent a distinctive atmospheric responses to the solar eclipses. 相似文献
6.
A ceramic material having a large dielectric constant at 77 K, ε=8000-12000, has been developed for capacitive energy storage at this temperature. A large matrix of multilayer ceramic capacitors were fabricated using conventional tape-casting methods to optimize the dielectric breakdown strength at 77 K, and measured energy storage values on these capacitors range up to 6 J/cm3 at 77 K. An unfused bank of these capacitors was voltage-cycled 105 times at 77 K without failure, and the heating effects during cycling were immeasurably small (i.e., nitrogen boiloff was monitored). An electrocaloric effect on discharge (ΔT~1 K) contributes to the thermal stability. Measurements of the frequency dependence of the dielectric properties of the ceramic at 77 K indicate a fundamental limit of about 8 μs for the switching repetition rate. Improved capacitor-manufacturing methods are discussed which can increase the energy density to the 20-30 J/cm3 range 相似文献
7.
The US Air Force NiH2 LEO (low earth orbit) life test consists of 200 cells undergoing real-time LEO cycling, pulse discharge testing, and storage testing. To date, three of the program's four objectives have been met: NiH2 performance in LEO applications has been demonstrated. A significant number of cells have completed more than 20,000 cycles at 40% DOD. A database for cells of both 3.5 in. and 4.5 in. diameter has been generated. There have been no indications of any performance problems related to scaling up in terms of cell size. Initial data on the pulse discharge performance of a small number of cells has been demonstrated. Concerning the goal of achieving 20,000 cycles at 60% DOD, the data are mixed. Overall, it appears highly unlikely that cell designs such as those currently in the US Air Force test can achieve 20,000 cycles at 60% 相似文献
8.
An update of validation test results confirming the advanced design nickel-hydrogen cell is presented. An advanced 125 Ah individual pressure vessel (IPV) nickel-hydrogen cell was designed for storing and delivering energy for long-term, low-earth-orbit (LEO) spacecraft missions. The new features of this design are: the use of 26% rather than 31% potassium hydroxide (KOH) electrolyte; a patented catalyzed wall wick; serrated-edge separators to facilitate gaseous oxygen and hydrogen flow within the cell, while maintaining physical contact with the wall wick for electrolyte management; and a floating rather than a fixed stack to accommodate nickel electrode expansion. The resulting improvements include extended cycle life and enhanced thermal, electrolyte, and oxygen management; and accommodation of nickel electrode expansion. Six 125-Ah flight cells based on this design are in the process of being evaluated in a LEO cycle life test 相似文献
9.
The logic and the schedule for a rule-based optimization technique useful for energy management onboard the Space Station are presented. A diverse array of experiments is scheduled within the constraints of limited solar energy and battery storage availability, taking into account the uneven energy supply between the sunshine and eclipse periods and the occasional need to serve a peak load and the full battery charging load simultaneously. In addition, the noninterruptible and nonrestartable nature of many experiments has to be accounted for in the schedule. These factors have been accounted for by using various time intervals and priority weighting factors. Supply/demand windows of various durations are tested for the typical load profile. This shows under what circumstances fewer scheduling tasks are needed and how a closer match between the supply and demand can be obtained. The optimal supply/demand is expressed in terms of the excess and shortage of electricity, the peak load, and the time displacement of the individual payloads. This technique is implemented using Prolog and Fortran 相似文献
10.
针对LEO(Low Earth Orbit,近地轨道)卫星的太阳电池阵输出功率衰减问题,在分析卫星轨道半长轴、太阳入射角、日地距离等参数变化与影响的基础上,提出按照轨道衰减快慢来区分太阳活动高年与低年,进而通过区分高年与低年,再根据不同季节分别进行太阳电池阵输出功率的衰减估计,而无须做功率归一化。同时,重点关注了夏至前后的最低输出功率的衰减情况,以此作为在轨卫星长期管理中的能源参考,建立平均电流和功率衰减因子估计模型,并结合实际工程数据进行了衰减估计。结果表明,太阳电池阵输出功率的年衰减因子约为-0.012,年衰减率约为1.2%。该结果可应用于在轨卫星长期管理的遥测诊断辅助。 相似文献
11.
本文用再结晶法测定了等幅循环载荷中施加超载后在裂纹尖端发生的高应变区内的塑性应变,求得了此区域的各参数与J积分、裂纹尖端张开位移CTOD及超载对疲劳裂纹扩展的延缓效应。实验结果表明,用再结晶法研究超载对裂纹扩展的延缓效应是一种很有效的方法。 相似文献
12.
Johnson G. Hunt M.E. Determan W.R. HoSang P.A. Ivanenok J. Schuller M. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(2):33-40
A 1,200-W solar AMTEC (alkali metal thermal-to-electric conversion) power system concept was developed and integrated with an advanced global positioning system (GPS) satellite. The critical integration issues for the SAMTEC with the GPS subsystems included: (1) packaging within the Delta II launch vehicle envelope; (2) deployment and start-up operations for the SAMTEC; (3) SAMTEC operation during all mission phases; (4) satellite field of view restrictions with satellite operations; and (5) effect of the SAMTEC requirements on other satellite subsystems. The SAMTEC power system was compared with a conventional planar solar array/battery power system to assess the differences in system weight, size, and operations, Features of the design include the use of an advanced multitube, vapor anode AMTEC cell design with 24% conversion efficiency, and a direct solar insolation receiver design with integral LiF salt canisters for energy storage to generate power during the maximum solar eclipse cycle, The modular generator design consists of an array of multitube AMTEC cells arranged into a parallel/series electrical network with built-in cell redundancy. Our preliminary assessment indicates that the solar generator design is scaleable over a 500 to 2,500-W range. No battery power is required during the operational phase of the GPS mission. SAMTEC specific power levels greater than 5 We/kg and 160 We/m2 are anticipated for a mission duration of 10 to 12 years in orbits with high natural radiation backgrounds 相似文献
13.
14.
The limiting performance of any orbital transfer vehicle (OTV) is fixed by its mass characteristics and the energy content of its propellant. The direct heating of hydrogen to high temperatures can produce practical specific impulses of 790 s which is to be compared with the liquid oxygen/liquid hydrogen limit of about 480 s in practical systems. A solar orbital transfer vehicle (SOTV) has been designed which utilizes a 100 m diameter concentrator system to provide the approximate 10 MW of thermal power needed to provide a nominal thrust level of 2780 N. The SOTV offers a compromise between typical chemical OTVs and electric propulsion OTVs. The SOTV can deliver 16 000 kg to geosynchronous orbit and 5000-10 000 kg to the inner planets. A four-week period for the assembly and payload integration for the SOTV has been found necessary. Several techniques for controlling the thrust level and thermal soak of the heat exchanger have been examined. Two of these, an expandable pupil stop reflector and concentrator surface deformation, are highly competitive. Considerable mission injection opportunity flexibility is possible with more than a 10 h launch window centered about each of local dusk and dawn. 相似文献
15.
16.
17.
A cathode mandrel with translational and rotational motion, which was supposed to obtain uniform friction effect on surface, was employed in abrasive-assisted electroforming for revolving parts with complex profile. The effects of current density, translational speed and rotational speed on the deposit properties were studied by orthogonal test. The tensile strength, elongation and micro hardness value were measured to find out how the factors affected the properties. The optimized results show that changes of current density affect the tensile strength of nickel layer most, while translational speed has the most remarkable influences on both elonga-tion and micro hardness. The low rotational speed affects the properties least. In this experiment, a smooth nickel layer with tensile strength 581 MPa, elongation 17%and micro hardness 248HV is obtained by the orthogonal test. 相似文献
18.
White N. E. Culhane J. L. Parmar A. N. Kellett B. Kahn S. van den Oord G. H. J. Kuijpers J. 《Space Science Reviews》1985,40(1-2):25-33
The X-ray emission from Algol is thought to originate in a corona associated with the K star in this system. We report the results of a 35 hr continuous EXOSAT observation through secondary optical eclipse that was designed to measure the structure of the corona. No obvious X-ray eclipse was seen. The spectrum measured by the ME gives a temperature of 2.5 × 107 K, consistent with the hard component previously seen by the Einstein SSS. The soft component previously reported by the SSS would only contribute at most 25% to the count rate seen in the LE (used with Al/P). The lack of a hard X-ray eclipse indicates the dimensions of the higher temperature emission region to be comparable to or greater than the size of the K star. An X-ray flare was detected with a peak luminosity of 1.4 × 1031 erg s-1 and a total duration of 8 hours. The peak temperature was 5.0 keV with an emission measure of 9.4 × 1053 cm-3. The thermal nature of the flare is confirmed by the detection of an iron line with an EW of 2 keV. By equating the observed decay time of the flare to a known cooling law gives a dimension for the flaring loop of 0.3 stellar radii. This is much smaller than the dimensions of the hard component inferred from the lack of an eclipse. It seems probable that the flare occurred in one of the loops responsible for the lower temperature component seen by the SSS. 相似文献
19.
A study conducted in 1991 on nickel-hydrogen (NiH2) battery cells, to assess their use for space-based radar satellites, is discussed. Current NiH2 and related programs were investigated. Cell performance data were assessed, focusing on pulsed-load operation, cell design factors, and life expectancy. A need for pulsed-load testing of candidate cells, especially to characterize their effective series resistance, dynamic impedance, and possible degradations, was identified. A NiH2 cell test program was planned, and test preparations started in mid-1992 相似文献
20.
Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 wh/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, Earth observation, resource mapping, and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS 相似文献