Effect of a drag force due to absorption of solar radiation on solar sail orbital dynamics

While solar electromagnetic radiation can be used to propel a solar sail, it is shown that the Poynting–Robertson effect related to the absorbed portion of the radiation leads to a drag force in the transversal direction. The Poynting–Robertson effect is considered for escape trajectories, Heliocentric bound orbits and non-Keplerian bound orbits. For escape trajectories, this drag force diminishes the cruising velocity, which has a cumulative effect on the Heliocentric distance. For Heliocentric and non-Keplerian bound orbits, the Poynting–Robertson effect decreases its orbital speed, thereby causing it to slowly spiral towards the Sun. Since the Poynting–Robertson effect is due to the absorbed portion of the electromagnetic radiation, degradation of a solar sail implies that this effect becomes enhanced during a mission.     

The Aurora project: Estimation of the optical sail parameters

The thrust model for computing a sailcraft trajectory contains thermo-optical parameters that are averages over the spectrum of the incident photons, namely, with respect to energy, intensity and polarization. These parameters are not observables and could change considerably from a sail to sail for a number of practical reasons. The mission analysis for a sailcraft is a progressive task from a simple trajectory propagator to the orbit determination. Aurora sailcraft mission analysis has advanced another step forward by processing experimental data related to aluminium. Once appropriate fitting functions have been selected, differential specular and diffused reflectance and differential absorptance have been averaged over incident solar spectrum, assumed a Planckian here. The result has been to get incident-angle-dependent optical parameters more reliable than mere literature values. The procedure has entailed the computation of grids of complicated definite integrals. They are particularly important during the trajectory optimization of the Aurora solar flyby, a very sensitive profile that would allow the sailcraft to achieve cruise speeds ranging from 12 to 20 AU/yr.     

游泳池太阳能加热系统设计及计算

文章选用U形铜管式太阳能集热器作为基本的太阳能光热转换单元,针对一个标准的室内游泳池的恒温加热,给出了游泳池太阳能加热系统的工程设计,并且通过相关计算,得到了优化的设计方案。     

From Halley's Comet to solar terrestrial science : The evolution of the Inter-Agency consultative group

The Inter-Agency Consultative Group (IACG) is an organization which seeks to maximize scientific returns from focused areas of space science through international cooperation. In its 11-year history the IACG has experienced both monumental success (with the collaborative exploration of Comet Halley) and, more recently, some serious growing pains in its second phase of operation, which focuses on solar terrestrial science. In this post-Cold War period, with increased interaction between countries offering greater opportunities for cooperation, the lessons to be learned from the IACG's experience will be valuable ones.     

Satellite solar power: Renewed interest in an age of climate change?

The concept of generating electricity using satellite solar power (SSP) has recently enjoyed renewed interest as a source of non-fossil fuel energy. First proposed in the 1960s, then studied sporadically in the past decade, SSP offers a potentially large supply of power but without the carbon emissions associated with evidence of global climate change. SSP faces challenges: competition from other non-fossil renewable energy, such as wind power, and the lead-time and costs required to assemble, test, and deploy an SSP system. At the request of a consortium of electric utilities, of NASA, and of the US National Science Foundation, this paper estimates the value of SSP in four distinct geographic regions, each differing in terms of their resource base for conventional renewable energy. Because deployment of SSP would be sometime in the future, we explicitly incorporate uncertainty in the model. We find the cost-effectiveness of SSP is highly sensitive to geographic region, to the reliability of SSP, and to the cost of carbon damages avoided by its use. The results offer guidance for decision makers in space, energy, and environment programs who must allocate scarce budgetary resources among competing public investment alternatives for clean energy.     

The Suess-Urey mission (return of solar matter to Earth)

The Suess-Urey (S-U) mission has been proposed as a NASA Discovery mission to return samples of matter from the Sun to the Earth for isotopic and chemical analyses in terrestrial laboratories to provide a major improvement in our knowledge of the average chemical and isotopic composition of the solar system. The S-U spacecraft and sample return capsule will be placed in a halo orbit around the L1 Sun-Earth libration point for two years to collect solar wind ions which implant into large passive collectors made of ultra-pure materials. Constant Spacecraft-Sun-Earth geometries enable simple spin stabilized attitude control, simple passive thermal control, and a fixed medium gain antenna. Low data requirements and the safety of a Sun-pointed spinner, result in extremely low mission operations costs.     

航天项目风险管理——预先识别与控制风险到可接受程度

风险是对成功实现项目目标的威胁。航天项目风险管理是预先对风险进行系统地识别、评估、跟踪和降低的活动,是一个在整个项目生命周期内连续、反复进行的过程。风险管理的目的是将风险降低到一个可接受的水平。根据风险对成功威胁的程度排序,可以使管理的关注点集中到风险程度较大的问题上。技术风险管理关注影响技术性能的风险,是项目风险管理的组成部分。     

网上客户服务中心技术与方案建设

本文主要介绍了网上客户服务中心技术采用的三层体系架构,通过通用数据库业务接口的设计,采用J2EE技术和WebLogic开发平台开发Web服务,通过中间件来整合业务以及帐务系统的数据资源和业务逻辑。此方案能满足代理合作和客户自助服务的业务受理和查询的实际要求,能满足移动业务不断变化的需求,为新的业务支撑系统的建设进行了有益的探索。     

网上客户服务中心技术与方案建设

本文主要介绍了网上客户服务中心技术采用的三层体系架构,通过通用数据库业务接口的设计,采用J2EE技术和WebLogic开发平台开发Web服务,通过中间件来整合业务以及帐务系统的数据资源和业务逻辑。此方案能满足代理合作和客户自助服务的业务受理和查询的实际要求,能满足移动业务不断变化的需求,为新的业务支撑系统的建设进行了有益的探索。     

The heliospheric magnetic field and its relation to the temperature,density, and velocity of solar plasma: Experimental evidence

Using daily and hourly data on solar plasma parameters at the Ulysses spacecraft orbit and at 1 AU it is demonstrated that there is a simple relationship between plasma temperature and density with the heliospheric magnetic field (HMF). A mathematical expression connecting HMF with plasma temperature and density is suggested. Correlation coefficients and regression equations for measured and calculated magnetic fields are presented for the 1990–2009 period according to Ulysses spacecraft data and for 2003–2010 at 1 AU (OMNI database). The roles played by density, temperature, and high-speed solar wind streams in forming the magnetic-field peaks are demonstrated using hourly data of OMNI2 and Ulysses.     

The LEO Archipelago: A system of earth-rings for communications,mass-transport to space,solar power,and control of global warming

Man's quest to get into space is hindered by major problems (e.g., system-development and capital costs, expense of putting mass into orbit, trapped-radiation belts, and environmental impact of a large increase in rocket launches). A multi-purpose low-earth-orbit system of rings circling the earth – the “LEO ARCHIPELAGO^TM” – is proposed as a means of solving or bypassing many of them. A fiber-optic ring about the earth would be an initial testing and developmental stage for the Ring Systems, while providing cash-flow through a LEO-based, high-band-width, world-wide communication system. A low-earth-orbit-based space-elevator system, “Sling-on-a-Ring^TM”, is proposed as the crucial developmental stage of the LEO Archipelago. Being a LEO-based heavy-mass lifter, rather than earth- or GEO-based, it is much less massive and therefore less costly than other proposed space-elevators. With the advent of lower-cost, higher-mass transport to orbit, the options for further space development (e.g., space solar power, radiation, and space-debris dampers, sun shades, and permanent LEO habitation) are greatly expanded.This paper provides an update of the Sling-on-a-Ring concept in terms of new materials, potential applications, and trade-offs associated with an earlier model. The impact of Colossal Carbon Tubes, CCT, a new material with high tensile strength, extremely-low density, and other favorable properties, and other new technologies (e.g., solar-powered lasers, power beaming to near-space and earth, and thermal-control systems) on the development of associated LEO-Ring systems is also explored. The material's effect on the timeline for the system development indicates the feasibility of near-term implementation of the system (possibly within the decade). The Sling-on-a-Ring can provide a less-expensive, environment-friendly mode of access to space. This would pave the way (via eventual operation at >1000 t per day by 2050) for large scale development of space-based technologies.     

The knowledge of knots: an interdisciplinary literature review

ABSTRACT

Knots can be found and used in a variety of situations in the 3D world, such as in vines, in the DNA, polymer chains, electrical wires, in mountaineering, seamanship and when ropes or other flexible objects are involved for exerting forces and holding objects in place. Research on knots as topological entities has contributed with a number of findings, not only of interest to pure mathematics, but also to statistical mechanics, quantum physics, genetics, and chemistry. Yet, the cognitive (or algorithmic) aspects involved in the act of tying a knot are a largely uncharted territory. This paper presents a review of the literature related to the investigation of knots from the topological, physical, cognitive and computational (including robotics) standpoints, aiming at bridging the gap between pure mathematical work on knot theory and macroscopic physical knots, with an eye to applications and modeling.     

The catalytic potential of cosmic dust: implications for prebiotic chemistry in the solar nebula and other protoplanetary systems

The synthesis of important prebiotic molecules is fundamentally reliant on basic starting ingredients: water, organic species [e.g., methane (CH(4))], and reduced nitrogen compounds [e.g., ammonia (NH(3)), methyl cyanide (CH(3)CN) etc.]. However, modern studies conclude that the primordial Earth's atmosphere was too rich in CO, CO(2), and water to permit efficient synthesis of such reduced molecules as envisioned by the classic Miller-Urey experiment. Other proposed sources of terrestrial nitrogen reduction, like those within submarine vent systems, also seem to be inadequate sources of chemically reduced C-H-O-N compounds. Here, we demonstrate that nebular dust analogs have impressive catalytic properties for synthesizing prebiotic molecules. Using a catalyst analogous to nebular iron silicate condensate, at temperatures ranging from 500K to 900K, we catalyzed both the Fischer-Tropsch conversion of CO and H(2) to methane and water, and the corresponding Haber-Bosch synthesis of ammonia from N(2) and H(2). Remarkably, when CO, N(2), and H(2) were allowed to react simultaneously, these syntheses also yielded nitrogen-containing organics such as methyl amine (CH(3)NH(2)), acetonitrile (CH(3)CN), and N-methyl methylene imine (H(3)CNCH(2)). A fundamental consequence of this work for astrobiology is the potential for a natural chemical pathway to produce complex chemical building blocks of life throughout our own Solar System and beyond.     

人工智能气动特性预测技术在火箭子级落区控制项目的应用

发展了一种基于人工智能算法的气动特性预测技术,在开展部分工况风洞试验基础上,结合少量数值仿真结果,通过机器学习模型预测全部工况气动特性.该方法能够降低研制成本,缩短周期.先后解决了相关函数选择、模型超参数训练、数据检验和"人在回路"应用等关键算法与技术问题,应用于运载火箭子级栅格舵落区控制项目气动研制,获得了设计所需完...     

Project Icarus: A review of local interstellar medium properties of relevance for space missions to the nearest stars

I review those properties of the interstellar medium within 15 light-years of the Sun, which will be relevant for the planning of future rapid (v≥0.1c) interstellar space missions to the nearest stars. As the detailed properties of the local interstellar medium (LISM) may only become apparent after interstellar probes have been able to make in situ measurements, the first such probes will have to be designed conservatively with respect to what can be learned about the LISM from the immediate environment of the Solar System. It follows that studies of interstellar vehicles should assume the lowest plausible density when considering braking devices, which rely on transferring momentum from the vehicle to the surrounding medium, but the highest plausible densities when considering possible damage caused by the impact of the vehicle with interstellar material. Some suggestions for working values of these parameters are provided. This paper is a submission of the Project Icarus Study Group.     

Survival and germinability of Bacillus subtilis spores exposed to simulated Mars solar radiation: implications for life detection and planetary protection

Bacterial spores have been considered as microbial life that could survive interplanetary transport by natural impact processes or human spaceflight activity. Deposition of terrestrial microbes or their biosignature molecules onto the surface of Mars could negatively impact life detection experiments and planetary protection measures. Simulated Mars solar radiation, particularly the ultraviolet component, has been shown to reduce spore viability, but its effect on spore germination and resulting production of biosignature molecules has not been explored. We examined the survival and germinability of Bacillus subtilis spores exposed to simulated martian conditions that include solar radiation. Spores of B. subtilis that contain luciferase resulting from expression of an sspB-luxAB gene fusion were deposited on aluminum coupons to simulate deposition on spacecraft surfaces and exposed to simulated Mars atmosphere and solar radiation. The equivalent of 42 min of simulated Mars solar radiation exposure reduced spore viability by nearly 3 logs, while germination-induced bioluminescence, a measure of germination metabolism, was reduced by less than 1 log. The data indicate that spores can retain the potential to initiate germination-associated metabolic processes and produce biological signature molecules after being rendered nonviable by exposure to Mars solar radiation.     

The astrobiology primer: an outline of general knowledge--version 1, 2006

The Astrobiology Primer has been created as a reference tool for those who are interested in the interdisciplinary field of astrobiology. The field incorporates many diverse research endeavors, but it is our hope that this slim volume will present the reader with all he or she needs to know to become involved and to understand, at least at a fundamental level, the state of the art. Each section includes a brief overview of a topic and a short list of readable and important literature for those interested in deeper knowledge. Because of the great diversity of material, each section was written by a different author with a different expertise. Contributors, authors, and editors are listed at the beginning, along with a list of those chapters and sections for which they were responsible. We are deeply indebted to the NASA Astrobiology Institute (NAI), in particular to Estelle Dodson, David Morrison, Ed Goolish, Krisstina Wilmoth, and Rose Grymes for their continued enthusiasm and support. The Primer came about in large part because of NAI support for graduate student research, collaboration, and inclusion as well as direct funding. We have entitled the Primer version 1 in hope that it will be only the first in a series, whose future volumes will be produced every 3-5 years. This way we can insure that the Primer keeps up with the current state of research. We hope that it will be a great resource for anyone trying to stay abreast of an ever-changing field.     

The definition of life: a brief history of an elusive scientific endeavor

In spite of the spectacular developments in our understanding of the molecular basis that underlies biological phenomena, we still lack a generally agreed-upon definition of life, but this is not for want of trying. Life is an empirical concept; and, as suggested by the many unsuccessful efforts to define it, this task is likely to remain, at best, a work in progress. Although phenomenological characterizations of life are feasible, a precise definition of life remains an elusive intellectual endeavor. This is not surprising: as Nietszche once wrote, there are concepts that can be defined, whereas others only have a history. The purpose of this essay is to discuss some of the manifold (and often unsatisfactory) definitions of life that have been attempted from different intellectual and scientific perspectives and reflect, at least in part, the key role that historical frameworks play. Although some efforts have been more fruitful, the lack of an all-embracing, generally agreed-upon definition of life sometimes gives the impression that what is meant by life's origin is defined in somewhat imprecise terms and that several entirely different questions are often confused. The many attempts made to reduce the nature of living systems to a single living compound imply that life can be so well defined that the exact point at which it started can be established with the sudden appearance of the first replicating molecule. On the other hand, if the emergence of life is seen as the stepwise (but not necessarily slow) evolutionary transition between the non-living and the living, then it may be meaningless to draw a strict line between them.     

From initial ideas to a European plan: GMES as an exemplar of European space strategy

Global Monitoring for Environment and Security (GMES) is an idea which originated during a meeting in Baveno, Italy, in May 1998, which generated a call for Europe to get its act together in the field of environmental monitoring from space, to define a well articulated strategy in this area and to build upon its excellent scientific research community, its proven technical prowess in Earth observation from space and its nascent political will to express its objectives in international fora related to climate change and other global environment topics. While Europe was already active in the most advanced areas of global monitoring, its rather uncoordinated efforts (even within the European Commission) lacked visibility and did not appear to fit into a clearly established strategy. The ‘Baveno initiative’ was an attempt to remedy this situation and find a place within a developing ‘European Strategy for Space’, which requires ESA and the European Union to work more closely together. GMES was extended to include the ‘security’ (in its wider sense) aspects of global monitoring, a move that produced a number of questions and misunderstandings, but which allowed many in Europe to realize that monitoring the activities of the Earth’ land masses, oceans and atmosphere do include a security dimension. GMES will eventually incorporate an implementation plan which will call upon various monitoring techniques, ambitious modelling projects and connections with society's more urgent requirements with respect to environmental protection and prevention or reduction of risks related to natural hazards. This will entail significant efforts to inform the user communities and to convince them of the relevance and usefulness of this initiative. It will also provide a sound basis for the European contribution to the new initiative for improved coordination of strategies and systems for Earth observations called for by the July 2003 Earth Observation Summit.