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     

Deep space travel energy sources

Exploration of the planets beyond Mars and their surroundings is already planned. Astronomy researchers are citing important information that can be obtained with instrumented spacecraft that fly beyond the planets of our solar system. Spacecraft flying these missions need power for performing their functions and communicating with Earth stations. Sunlight in these zones is so weak that alternative energy sources are needed. An alternative power source for deep-space missions is radioisotope heated energy converters.. The choice of heat-to-electric power conversion is narrowing to: 1) the Stirling engine; and 2) a combined cycle with thermionic and alkali-metal thermoelectric (AMTEC) heat-to-electricity conversion. For propulsion into deep space, a nuclear-reactor-heated AMTEC energy converter that powers ion engines can become the best alternative to hoisting tons of rockets into Earth orbit.     

The design of a nuclear power supply with a 50 year lifeexpectancy: the JPL Voyager's SiGe MHW RTG

Between 25 and 30 years ago, the IECEC Proceedings carried a series of papers by the present authors and other members of a JPL team on the problems and the desirable design features associated with the MHW RTGs to be used to power JPL's Voyager I and II spacecraft. The Voyager I and II spacecraft successfully completed their original 12 year missions 10 years ago and are at distances of over 55 AU and 70 AU from the sun. The power systems worked almost precisely as predicted. The Voyager spacecraft seem to have several decades of life left to make measurements outside the solar system. This paper gives a technical overview of the design process and problems     

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     

AMTEC cells challenge energy converters

Sodium-base alkali-metal-thermal-to-electric conversion (AMTEC) cells have been receiving attention. Recently they were selected for the next generation deep-space missions, which need a converter that makes electricity from radioisotope heat. The AMTEC cell, being an electrochemical converter of heat to electricity, has no moving parts and is not limited to Carnot-cycle efficiency. However, its heat source and sink have to be near each other, so the challenge in AMTEC design is to minimize thermal losses and maximize electricity production. This required clever thermal designs. By 1991, high-temperature materials and computer modeling became available. The important AMTEC application was generating power from radioisotope heat in deep space missions. These spacecraft power needs had previously been supplied by inefficient thermoelectric converters     

Engine-driven generators for deep space probes

Summarizes important developments relating to power for deep space missions. The important alternatives to thermocouples for converting radioisotope heat into electric power are Stirling engines, alkali-metal thermal-to-electric converters (AMTEC), thermionic converters, and thermo-photovoltaic converters. The operating principles and limitations of these converters are described.     

Conversations: with Carl Pilcher [interview by Johan Benson

An interview with Carl Pilcher, science program director for solar system exploration at NASA, examines NASA's past, present, and planned missions to explore the solar system. Specific questions relate to the status of current and planned missions, science results of the Pathfinder mission to Mars, cooperation with the Japanese space agency, the status of the search for extraterrestrial life in solar system meteoroids and asteroids, mission size for more in-depth exploration, reports of water on the moon, and the exploration of near-Earth objects.     

Radioisotope powered AMTEC systems

Alkali Metal Thermal to Electric Converter (AMTEC) systems are being developed for high performance spacecraft power systems, including small, General Purpose Heat Source (GPHS) powered systems. Several design concepts have been evaluated for the power range from 75 W to 1 kW. The specific power for these concepts has been found to be as high as 18-20 W/kg and 22 kW/m³. The projected area, including radiators, has been as low as 0.4 m²/kW. AMTEC power systems are extremely attractive, relative to other current and projected power systems, because AMTEC offers high power density, low projected area, and low volume. Two AMTEC cell design types have been identified. A single-tube cell is already under development and a multi-tube cell design, to provide additional power system gains, has undergone proof-of-principle testing. Solar powered AMTEC (SAMTEC) systems are also being developed, and numerous terrestrial applications have been identified for which the same basic AMTEC cells being developed for radioisotope systems are also suitable     

飞机电源系统故障诊断方法综述及发展趋势

飞机电源系统是机上一切用电设备的电能来源,其安全性与可靠性至关重要。在环保和高效发展需求的背景下,现代航空工业正在推进以电能为核心的多电/全电飞机技术的研究和应用。电驱动装置和电力电子器件的广泛使用导致飞机电源系统结构的复杂化,对飞机的可靠性、安全性、测试性和维修性提出了更高的要求,研究飞机电源系统的故障诊断技术具有重要意义。首先介绍了飞机电源系统的组成结构和各自功能,概述了飞机电源系统的发展历程,对比了国内外典型电源系统的特征,总结了飞机电源系统中的主要故障模式、故障特点和失效原因,并提出了一种飞机电源健康管理系统的设计架构,然后综述了国内外基于模型和基于数据的故障诊断方法研究进展,从准确度、数据需求量、适用性和实现难易程度等方面评述了各类诊断方法的特点,最后指出了飞机电源系统故障诊断技术面临的挑战和发展趋势。     

深空导航无线电干涉测量技术的发展历程和展望

结合世界各航天大国和组织所开展的深空探测活动和深空测控系统建设中,对无线电干涉测量技术的开发、应用以及深空导航技术试验验证情况,系统地梳理和总结了深空导航无线电干涉测量技术的发展历程,并通过该技术未来在国际上几个主要深空探测任务中的应用规划,分析了无线电干涉测量领域未来的发展方向.该领域技术的最新发展对我国深空测控网无线电干涉测量系统的后续建设也具有重要的借鉴意义.     

大功率空间核电推进技术研究进展

大功率空间核电推进系统是空间核电源技术和大功率电推进技术的高度融合,具有高能量密度、超高比冲、较大推力的优势,可适用于超大型航天器轨道转移任务、远距离无人深空探测任务、载人火星等大型深空探测任务,能够极大地拓展人类深空探测的能力。本文针对大功率空间核电推进技术,对其工作原理和系统组成进行了介绍,同时开展了关键技术梳理,重点归纳了国内外在技术领域的研究历程和最新进展。     

我国深空探测地面站发射机的发展及展望

随着深空探测任务的发展,对地面站发射机输出功率有了越来越高的要求.在讨论了测控系统地面站发射机的国内外发展现状和应用趋势的基础上,重点分析了未来我国发射机的主要发展方向和趋势,并对其中的关键技术进行了详细描述;提出了我国未来发展深空探测地面站发射机应该开展关键技术、关键元器件或零部件的研究工作,以及一些技术发展方向性的理论研究的建议,为我国深空探测技术的发展提供了参考.     

The New Horizons Spacecraft

The New Horizons spacecraft was launched on 19 January 2006. The spacecraft was designed to provide a platform for seven instruments designated by the science team to collect and return data from Pluto in 2015. The design meets the requirements established by the National Aeronautics and Space Administration (NASA) Announcement of Opportunity AO-OSS-01. The design drew on heritage from previous missions developed at The Johns Hopkins University Applied Physics Laboratory (APL) and other missions such as Ulysses. The trajectory design imposed constraints on mass and structural strength to meet the high launch acceleration consistent with meeting the AO requirement of returning data prior to the year 2020. The spacecraft subsystems were designed to meet tight resource allocations (mass and power) yet provide the necessary control and data handling finesse to support data collection and return when the one-way light time during the Pluto fly-by is 4.5 hours. Missions to the outer regions of the solar system (where the solar irradiance is 1/1000 of the level near the Earth) require a radioisotope thermoelectric generator (RTG) to supply electrical power. One RTG was available for use by New Horizons. To accommodate this constraint, the spacecraft electronics were designed to operate on approximately 200 W. The travel time to Pluto put additional demands on system reliability. Only after a flight time of approximately 10 years would the desired data be collected and returned to Earth. This represents the longest flight duration prior to the return of primary science data for any mission by NASA. The spacecraft system architecture provides sufficient redundancy to meet this requirement with a probability of mission success of greater than 0.85. The spacecraft is now on its way to Pluto, with an arrival date of 14 July 2015. Initial in-flight tests have verified that the spacecraft will meet the design requirements.     

Nuclear Power Systems for Spacecraft

A review and comparison of the weights, sizes, and costs of nuclear and non-nuclear spacecraft power systems is presented and discussed. Nuclear power systems include the range below 10 kW, with an electrical output to weight ratio of 0.5 to 1.0 pounds per watt. Comparisons show that primary batteries are lighter for short-duration missions of a few hours; fuel cells are lighter for durations of one to two months; and solar-cell/secondary battery combinations are to be preferred when sunlight is adequate.     

Performance enhancement using power beaming for electric propulsionEarth orbital transporters

Power requirements for an electric propulsion Earth orbital transport vehicle (EOTV), which can effectively deliver large payloads using much less propellant than chemical transfer methods, are addressed. The power beaming concept is described. Arcjets, magnetoplasmadynamic (MPD) thrusters, and ion engines are covered. Power supply characteristics are discussed for nuclear, solar and power-beaming systems. Operational characteristics are given for each, as are the effects of the power supply alternative on the overall craft performance. Because of its modular nature, the power beaming can meet the power requirements of all three electric propulsion types. Commonality of approach allows different electric propulsion approaches to be powered by means of a single power supply approach. Power beaming exhibits better flexibility and performance than onboard nuclear or solar power systems     

载人火星探测进展及其EDL过程GNC关键技术

随着火星探测技术的不断发展和探测任务的不断推进，载人火星探测在未来将会成为火星探测的重要手段。首先，回顾了无人火星探测任务的发展历程，对比分析了部分无人火星探测器进入、下降与着陆（EDL）过程的参数。然后，结合无人火星探测、载人月球探测和载人航天再入过程，梳理了载人火星探测的特点及需求，系统地总结了前苏联/俄罗斯和美国的载人火星探测研究进展以及技术储备。接着，归纳了载人火星探测的体系构成、集结方式和主要的技术挑战。最后，概括了载人火星EDL过程面临的难题，重点阐述了EDL的导航、制导与控制（GNC）关键技术。     

超大功率电推进电源处理单元关键技术研究

针对深空探测等空间任务对超大功率(10kW~100kW范围)电推进系统的需求,通过对国内外超大功率电推进技术的调研,提出了一种50kW超大功率霍尔电推进系统电源处理单元（Power Processing Unit,PPU）设计方案,重点对核心的阳极电源关键技术进行研究,提出了四管Buck-Boost变换器和三相LLC谐振变换器级联的设计方案,为我国超大功率PPU的发展提供了技术参考。     

Engineering test beds on the International Space Station

The International Space Station is a unique multi-faceted orbiting laboratory supporting research, development, test and evaluation of new innovative space and Earth-based applications. While NASA sponsored investigations on the ISS are focused largely on enabling future long duration human space exploration missions, Congress designated the US portion of the space station as a National Laboratory making its facilities available to other Federal agencies and private entities for non-exploration related ventures. RDT&E activities on the ISS encompass a number of technical areas including environmental control and life support, communications, materials science, guidance, navigation and control, propulsion, electrical power, and thermal control systems.     

The past as prologue: a look at historical flight qualificationsfor space nuclear systems

The author examines what it means to flight qualify a space nuclear system. He reviews several qualification programs, including the general-purpose heat source radioisotope thermoelectric generators (GPHS-RTGs) as developed for the Galilee and Ulysses missions, the SNAP-10A space reactor, the Nuclear Engine for Rocket Vehicle Applications (NERVA), the F-1 chemical engine used on the Saturn-V, and the Space Shuttle Main Engines (SSMEs). Similarities and contrasts are noted     

基带滤波调制技术深空测控应用性能分析

深空测控的下行链路包括测控和数传2种典型的传输信道,其中数传信道一般具有发射功率大和数据传输速率高的特点,其带外辐射容易对测控信道产生干扰。以典型月球探测器为例,分析比较了数传信道采用常规BPSK（二进制相移键控）调制和基带滤波BPSK调制时,对测控信道的带外辐射影响,并对基带滤波BPSK调制的误码率性能进行了仿真分析,相应结论对未来深空探测任务测控系统总体设计具有十分重要的参考意义。