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.     

Investigation of nuclear electric powered interstellar precursor missions

Nuclear Electric Propulsion (NEP) is a technology conceptually proposed since the 1940s by E. Stuhlinger in Germany. The JIMO mission originally planned by NASA in the early 2000s produced at least two designs of ion thrusters fed by a 20–30 kW nuclear powerplant. When compared to conventional (chemical) propulsion, the major advantage of NEP in the JIMO context was recognized to be the much higher I_sp (lab-tested at up to 15,000 s) and the capability for sustained power generation, up to 8–10 years when derated to I_sp about 8000 s.The goal of this paper is to show that current or near term NEP technology enables missions far beyond our immediate interplanetary backyard. In fact, by extending the semi-analytical approach used by Stuhlinger, with reasonable ratios α≡power/mass of the propulsion system (i.e., 0.1– 0.4 kW/kg), missions to the Kuiper Belt (40 AU and beyond) and even the so-called FOCAL mission (at 540 AU) become feasible with an attractive payload fraction and in times of order 10–15 years.Further results regarding missions to Sedna’s perihelion/aphelion, and to Oort’s cloud will also be presented, showing the constraints affecting their feasibility and mass budget.     

Autocatalytic fission–fusion microexplosions for nuclear pulse propulsion

Autocatalytic fission–fusion microexplosions, mutually amplifying fission and fusion reactions, are proposed for propulsion. Autocatalytic fission–fusion microexplosions can be realized by imploding a shell of uranium 235 (or plutonium) onto a magnetized deuterium–tritium (DT) plasma. After having reached a high temperature, the DT plasma releases fusion neutrons making fission reactions in the fissile shell increasing the implosion velocity which in turn increases the fusion reaction rate until full ignition of the DT plasma. To implode the fissile shell a small amount of high explosive and to magnetize the DT plasma a small auxiliary electric discharge are required. In comparison to nuclear bomb pulse propulsion, the energy released per pulse is much smaller and the efficiency higher. And in comparison to laser- or particle-beam-ignited fusion microexplosions, there is no need for a massive fusion ignition driver.     

中国航天固体火箭技术的发展

叙述了20世纪50年代以来中国航天固体火箭推进技术的发展历程,介绍了9种最具代表性的固体火箭发动机的技术特征、研制过程、地面试验和飞行情况,这些发动机分别应用于中国的探空火箭、运载火箭上面级和应用卫星变轨系统。文中还简要地评述了中国固体推进各单项技术的发展水平。     

A direct fusion drive for rocket propulsion

The Direct Fusion Drive (DFD), a compact, anuetronic fusion engine, will enable more challenging exploration missions in the solar system. The engine proposed here uses a deuterium–helium-3 reaction to produce fusion energy by employing a novel field-reversed configuration (FRC) for magnetic confinement. The FRC has a simple linear solenoid coil geometry yet generates higher plasma pressure, hence higher fusion power density, for a given magnetic field strength than other magnetic-confinement plasma devices. Waste heat generated from the plasma?s Bremsstrahlung and synchrotron radiation is recycled to maintain the fusion temperature. The charged reaction products, augmented by additional propellant, are exhausted through a magnetic nozzle. A 1 MW DFD is presented in the context of a mission to deploy the James Webb Space Telescope (6200 kg) from GPS orbit to a Sun–Earth L2 halo orbit in 37 days using just 353 kg of propellant and about half a kilogram of ³He. The engine is designed to produce 40 N of thrust with an exhaust velocity of 56.5 km/s and has a specific power of 0.18 kW/kg.     

核热推进技术综述

分析了核热推进相对于现有传统推进技术的优势,介绍了可能的技术实现途径,重点是目前已经实现的固相核热推进技术,并归纳了有关文献对于固相核热推进技术的空间应用分析结果;介绍了核热推进技术的发展历程,并对当前发展态势进行了分析;最后针对我国发展核热推进技术提出几点考虑。     

Societal imperatives and the need for space nuclear power and propulsion systems

The development and exploitation of nuclear power and propulsion represent certain didactic imperatives for human civilization. Among these are economic, epistemological, moral and commercial propositions. Developing space nuclear power and propulsion represents one future; the choice of not to pursue the course barring some breakthrough in physics represents a dramatically different future. The author argues that the time is now fortuitous for deployment and operation of nuclear propulsion and power, primarily nuclear electric propulsion, at significant levels, employing figures of merit that transcend simple cost models used to justify nuclear power sources in the past. The proposition is examined, in the light of US and UN restrictions, to ascertain how best to proceed. The author argues that viewpoints of certain vocal albeit uninformed public interest groups are typically self-serving and generally categorically incorrect; it can be asserted that these same groups do not truly represent the public interest at all. It is, therefore, necessary to present an even-handed assessment of both sides of the argument to determine the virtues and liabilities of embarking on such a developmental path. Given the imperatives mentioned, the author argues that nuclear power and propulsion for space systems is a societal necessity.     

Overview and status of a mirror fusion propulsion system design study

The main goal of this paper is to describe and emphasize the important discoveries made since 1986 in the engineering design of space fusion propulsion plants.

Among the important discoveries are four fundamental design principles (DPs) which should be used when adapting candidate Earth-based fusion-electric power plants to propulsion in space.

1. DP1. Maximize direct access to space for waste radiation.

2. DP2. Operate components as passive radiators whenever possible.

3. DP3. Optimize the plasma characteristics for best specific jet power

4. DP4. Optimize mission capability versus lifetime-mass-to-orbit (LMTO).

Another discovery is a design philosophy called IDEAs (Integrated Design Environment Algorithms) which is a tool for discovering new fundamental design principles.

These discoveries allowed us to adapt, and then to optimize, an earth-based fusion-electric magnetic-mirror-fusion reactor concept for propulsion in space. The resulting design is called the Mirror Fusion Propulsion System (MFPS); and its design status is reviewed.

This work can be used as a general road map for others attempting to convert earth-based designs to propulsion in space. It also has applicability to matter-antimatter propulsion systems engineering.     

核火箭原理、发展及应用

人类在不懈地对浩瀚的宇宙进行着探索,而强劲的推力是人类探索宇宙的关键。化学火箭在人类宇宙探索活动中书写了一页又一页的华丽篇章,现今在人类新的探索使命下,出现了激光、太阳能、微波、核热能等新的推进技术。在这些技术中,核火箭推进无疑是人类继续探索太空最有希望的技术之一。对核火箭的原理、发展状况以及应用前景进行了介绍。     

Space nuclear power: technology, policy, and risk considerations in human missions to Mars

There is a large discrepancy between potential needs for nuclear propulsion and power systems for the human exploration of Mars and the current status of R&D funding, public opinion, and governmental support for these technologies. Mission planners and spacecraft designers, energized by the recent claims of possible discovery of life on Mars and responding to increased public interest in the human exploration of Mars, frequently propose nuclear reactors and radioisotope thermoelectric generators (RTGs) for interplanetary spacecraft propulsion and for power supply on the surface of Mars. These plans and designs typically assume that reactors will be available "on-the-shelf," and do not take the extensive R&D costs required to develop such reactors into consideration. However, it is likely that current U.S. policies, if unchanged, will prohibit the launch of nuclear reactors and large RTGs in response to a perceived risk by the public.     

Project of the space test&fitting-out dock for solar-powered electric propulsion on-board international space station

A concept of a universal fitting-out module applicable for space flight test of a solar-powered electric propulsion (EP) as well as for the assembly and deployment of small spacecraft (S/C) from the international space station (ISS) is proposed.     

Future earth observation missions for oceanographic applications: Indian perspectives

Significant progress has been achieved in India in demonstrating the utility of remote sensing data for various oceanographic applications during the last one decade. Among these, techniques have been developed for retrieval of ocean surface waves, winds, wave forecast model, internal waves, sea surface temperature and chlorophyll pigments. Encouraged from these results as well as for meeting the specific and increasing data requirements on an assured basis by oceanographers, India is making concerted efforts for developing and launching state-of-the-art indigenous satellites for ocean applications in the coming years.

The first in the series of ocean satellites planned for launch is Oceansat-1 (IRS-P4) by early 1999. Oceansat-1 carries on-board an Ocean Colour Monitor (OCM) and a Multi-frequency Scanning Microwave Radiometer (MSMR). OCM will have 8 narrow spectral bands operating in visible and near- infrared bands (402–885 nm) with a spatial resolution of 360 m and swath of 1420 km. The MSMR with its all weather capability is configured to have measurements at 4 frequencies viz., 6.6, 10.65, 18 & 21 GHz in dual polarisation mode with a spatial resolution of 120, 80, 40 & 40 km, respectively with an overall swath of 1360 km. The Oceansat-1 with repetitivity of once in two days will provide global data for retrieval of various oceanographic and meteorological parameters such as chlorophyll (primary productivity), sea surface temperature and wind speed, besides a host of other parameters of relevance to meteorology.

A full fledged satellite for ocean applications known as Oceansat-2 (IRS-P7) is also planned for launch during 2002. This satellite with payload mix of microwave (Scatterometer, Altimeter & Passive Microwave Radiometer), Thermal (TIR) and Optical (OCM) sensors, will provide greater in-sight into the global understanding of ocean dynamics/resources. This mission is expected to provide a complete set of oceanographic measurements, which are useful for providing operational oceanographic services.

Efforts are also on towards development of missions having multi-frequency, multipolarisation and multi-look angle microwave payloads including Synthetic Aperture Radar (SAR) and advanced millimeter wave sounders, besides development of imaging spectrometers by 2005.

A well-knit plan has been initiated in India for utilisation of planned Oceansat data. Important efforts initiated in this direction include SATellite Coastal and Oceanographic Research and Ocean Information Services, which are being carried out on an integrated basis aiming at providing services to the down stream users. The paper highlights these efforts in India towards providing an operational ocean information services in the coming years.     

Optimization of the propulsion for meteorological probe

The paper discusses the problem of optimization of the power distribution between a rocket booster and a ramjet second stage of meteorological probe. The best solution was found for the case when the ramjet stage starts to operate at the velocity equal to 1.5 M.     

Astromedicine and astrolaw: Emerging issues for advanced missions beyond Earth orbit

It is generally agreed within the scientific community that provision of appropriate medical facilities and administration of quality health care to astronauts are of great importance. However, for the more complex and remote missions envisaged for the future, issues of liability, responsibility and damage relating to medical practice may take on a greater significance and will need to be addressed. The author briefly reviews potential issues which may arise in the context of medical emergencies, crew autonomy and environmentally altered physiological status which characterize some projected advanced space missions and argues that the law of outer space will need to be expanded to take account of them.     

Manned missions to Mars: Minimizing risks of failure

Some major risks-of-failure issues for the future manned missions to Mars are discussed, with an objective to address criteria for making such missions possible, successful, safe and cost-effective. The following astronautical and instrumentation-and-equipment-reliability related aspects of the missions are considered: redundancies and backup strategies; costs; assessed probability of failure as a suitable reliability criterion for the instrumentation (equipment); probabilistic assessment of the likelihood of the mission success and safety. It is concluded that parametric risk modeling is a must for a risk-driven decision-making process.     

Optimization of space orbits design for Earth orbiting missions

In Earth orbiting space missions, the orbit selection dictates the mission parameters like the ground resolution, the area coverage, and the frequency of coverage parameters. To achieve desired mission parameters, usually Earth regions of interest are identified and the spacecraft is maneuvered continuously to visit only these regions. This method is expensive, it requires a propulsion system onboard the spacecraft, working throughout the mission lifetime. It also requires a longer time to cover all the regions of interest, due to the very weak thrust forces compared to that of the Earth's gravitational field. This paper presents a methodology to design natural orbits, in which the regions of interest are visited without the use of propulsion systems, depending only on the gravitational forces. The problem is formulated as an optimization problem. A genetic algorithm along with a second order gradient method is implemented for optimization. The design process takes into consideration the gravitational second zonal harmonic, and hence allows for the design of repeated Sun-synchronous orbits. The field of view of the payload is also taken into consideration in the optimization process. Numerical results are presented that demonstrates the efficiency of the proposed method.     

火星探测器推进系统初步设想

火星探测是深空探测的重要内容之一,全面了解和掌握火星探测器的特点对进行火星探测具有重要意义.本文分析了国外火星探测器推进系统的系统组成和工作原理,介绍了我国火星探测器推进系统的初步设计方案,结合工程应用现状,提出了火星探测器推进系统的关键技术.     

Lunar precursor missions for human exploration of Mars--III: studies of system reliability and maintenance

Discussions of future human expeditions into the solar system generally focus on whether the next explorers ought to go to the Moon or to Mars. The only mission scenario developed in any detail within NASA is an expedition to Mars with a 500-day stay at the surface. The technological capabilities and the operational experience base required for such a mission do not now exist nor has any self-consistent program plan been proposed to acquire them. In particular, the lack of an Abort-to-Earth capability implies that critical mission systems must perform reliably for 3 years or must be maintainable and repairable by the crew. As has been previously argued, a well-planned program of human exploration of the Moon would provide a context within which to develop the appropriate technologies because a lunar expedition incorporates many of the operational elements of a Mars expedition. Initial lunar expeditions can be carried out at scales consistent with the current experience base but can be expanded in any or all operational phases to produce an experience base necessary to successfully and safely conduct human exploration of Mars.     

一种姿控动力装置热防护研究

酚醛树脂作为一种烧蚀材料,凭借其耐高温的特性应用于航天器防热系统,其防热性能在工程实际中需进行考核。以某航天器一段包覆80纤维布/酚醛树脂的液路管路作为研究对象,以定热流为边界条件,采用仿真计算和热流试验的研究方法对空导管以及注水导管的温度场进行研究:仿真计算得出导管表面平衡温度分布以及导管表面具有代表性某点瞬态温度变化;为验证仿真计算的准确性,进行了热流试验,得出了导管表面以及水中温度测点的瞬态温度变化;根据热流试验的温度结果,分析比对了热流试验对仿真计算的验证情况。研究结果表明:80纤维布/酚醛树脂的防热性能符合温度指标要求;仿真结果和热流试验结果一致度良好,证明了仿真计算的合理性和准确性。     

空间推进系统可靠性评估方法的改进

空间推进系统可靠性评估时,采用Lindstrom-Maddens(L-M)法评估比传统方法得到的结果更高。对比分析评估数据后发现L-M法更合理,因此建议采用L-M法进行可靠性评估,可以在满足可靠性指标前提下防止对产品提出过分苛刻的要求,从而降低设计难度和减少试验费用。