摘要:

The expansion of a high temperature fusion plasma through an expanding magnetic field is a process common to most fusion propulsion concepts. The efficiency of this process has a strong bearing on the overall performance of fusion propulsion. In order to simulate the expansion of a fusion plasma, a concept has been developed in which a high velocity plasma is first stagnated in a converging magnetic field to high (100’s of eV) temperatures, then expanded though a converging/diverging magnetic nozzle. A Magnetoplasmadynamic (MPD) plasma accelerator has been constructed to generate the initial high velocity plasma and is currently undergoing characterization at the Ohio State University. The device has been operated with currents up to 300 kA and power levels up to 200 MWe. The source is powered by a 1.6 MJ, 1.6 ms pulse‐forming‐network. In addition to experimental tests of the accelerator, computational and theoretical modeling of both the accelerator and the plasma stagnation have been performed using the MACH2 MHD code. Insights into plasma compression and attachment to magnetic field lines have led to recommended design improvements in the facility and to preliminary predictions of nozzle performance. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649591

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

For some future space power systems using high temperature nuclear heat sources most of the output energy will be used in other than electrical form, and only a fraction of the total thermal energy generated will need to be converted to electrical work. The paper describes the conceptual design of such a “partial energy conversion” system, consisting of a high temperature fusion reactor operating in series with a high temperature radiator and in parallel with dual closed cycle gas turbine (CCGT) power systems, also referred to as closed Brayton cycle (CBC) systems, which are supplied with a fraction of the reactor thermal energy for conversion to electric power. Most of the fusion reactor’s output is in the form of charged plasma which is expanded through a magnetic nozzle of the interplanetary propulsion system. Reactor heat energy is ducted to the high temperature series radiator utilizing the electric power generated to drive a helium gas circulation fan. In addition to discussing the thermodynamic aspects of the system design the authors include a brief overview of the gas turbine and fan rotor‐dynamics and proposed bearing support technology along with performance characteristics of the three phase AC electric power generator and fan drive motor. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649592

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The Colliding Beam Fusion Reactor Space Propulsion System, CBFR‐SPS, is an aneutronic, magnetic‐field‐reversed configuration, fueled by an energetic‐ion mixture of hydrogen and boron11(H‐B11). Particle confinement and transport in the CBFR‐SPS are classical, hence the system is scaleable. Fusion products are helium ions, &agr;‐particles, expelled axially out of the system. &agr;‐particles flowing in one direction are decelerated and their energy recovered to “power” the system; particles expelled in the opposite direction provide thrust. Since the fusion products are charged particles, the system does not require the use of a massive‐radiation shield. This paper describes a 100 MW CBFR‐SPS design, including estimates for the propulsion‐system parameters and masses. Specific emphasis is placed on the design of a closed‐cycle, Brayton‐heat engine, consisting of heat‐exchangers, turbo‐alternator, compressor, and finned radiators. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649593

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The research and development status of the 150‐mN‐class xenon ion thruster is described. After a couple of redesigns and trial fabrications, the first breadboard thruster achieved a very low ion production cost of 104 W/A. Endurance tests suggest that the grid system will have a lifetime of about 25,000 h. A hollow cathode wear test suggests that it will be over 30,000 h before its orifice plate is completely worn out. A thrust range of 80 to 200 mN without performance degradation has been demonstrated. In the power conditioner development, efficiencies of 87 to 88&percent; have been achieved in the main power supplies. Its compatibility with the thruster was demonstrated. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649594

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Recent US and European initiatives in Nuclear Propulsion lend themselves naturally to raising the question of comparing various options and particularly Nuclear Electric Propulsion (NEP) with Solar Electric Propulsion (SEP). SEP is in fact mentioned in one of the latest versions of the NASA Mars Manned Mission as a possible candidate. The purpose of this paper is to compare NEP, for instance, using high power MPD, Ion or Plasma thrusters, with SEP systems. The same payload is assumed in both cases. The task remains to find the final mass ratios and cost estimates and to determine the particular features of each technology. Each technology has its own virtues and vices: NEP implies orbiting a sizeable nuclear reactor and a power generation system capable of converting thermal into electric power, with minimum mass and volumes compatible with Ariane 5 or the Space Shuttle bay. Issues of safety and launch risks are especially important to public opinion, which is a factor to be reckoned with. Power conversion in space, including thermal cycle efficiency and radiators, is a technical issue in need of attention if power is large, i.e., of order 0.1 MW and above, and so is power conditioning and other ancillary systems. Type of mission, Ispand thrust will ultimately determine a large fraction of the mass to be orbited, as they drive propellant mass. For manned missions, the trade‐off also involves consumables and travel time because of exposure to Solar wind and cosmic radiation. Future manned NEP missions will probably need superconducting coils, entailing cryostat technology. The on‐board presence of cryogenic propellant (e.g., LH2) may reassure the feasibility of this technology, implying, however, a trade‐off between propellant volume to be orbited and reduced thruster mass. SEP is attractive right now in the mind of the public, but also of scientists involved in Solar system exploration. Some of the appeal derives from the hope of reducing propellant mass because of the perceived high Ispof ion engines or future MPD. The comparison, in fact, will show whether the two systems could have the same type of thruster or not, for automatic or for manned missions. The main drawback of SEP is due to photovoltaics and the total solar cell area required, driving spacecraft mass and orbiting costs up. In addition, the question of using superconducting coils holds also for SEP, while no space radiator is, in principle, needed. These and other factors will be considered in this comparison. The goal is to provide preliminary guidelines in evaluating SEP and NEP that may be useful to suggest closer scrutiny of promising concepts, or even potential solutions. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649595

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Very low specific‐mass power generation in space is possible using Vapor Core Reactors with Magnetohydrodynamic (VCR/MHD) generator. These advanced reactors at the conceptual design level have potential for the generation of tens to hundreds of megawatts of power in space with specific mass of about 1 kg/kWe. Power for nuclear electric propulsion (NEP) is possible with almost direct power conditioning and coupling of the VCR/MHD power output to the VASIMR engine, MPD, and a whole host of electric thrusters. The VCR/MHD based NEP system is designed to power space transportation systems that dramatically reduce the mission time for human exploration of the entire solar system or for aggressive long‐term robotic missions. There are more than 40 years of experience in the evaluation of the scientific and technical feasibility of gas and vapor core reactor concepts. The proposed VCR is based on the concept of a cavity reactor made critical through the use of a reflector such as beryllium or beryllium oxide. Vapor fueled cavity reactors that are considered for NEP applications operate at maximum core center and wall temperatures of 4000 K and 1500K, respectively. A recent investigation has resulted in the conceptual design of a uranium tetrafluoride fueled vapor core reactor coupled to a MHD generator. Detailed neutronic design and cycle analyses have been performed to establish the operating design parameters for 10 to 200 MWe NEP systems. An integral system engineering‐simulation code is developed to perform parametric analysis and design optimization studies for the VCR/MHD power system. Total system weight and size calculated based on existing technology has proven the feasibility of achieving exceptionally low specific mass (&agr; ∼1 kg/kWe) with a VCR/MHD powered system. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649596

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Interest in high power electromagnetic propulsion has been revived to support a variety of future space missions, such as platform maneuvering in low earth orbit, cost‐effective cargo transport to lunar and Mars bases, asteroid and outer planet sample return, deep space robotic exploration, and piloted missions to Mars and the outer planets. Magnetoplasmadynamic (MPD) thrusters have demonstrated, at the laboratory level, the capacity to process megawatts of electrical power while providing higher thrust densities than current electric propulsion systems. The ability to generate higher thrust densities permits a reduction in the number of thrusters required to perform a given mission and alleviates the system complexity associated with multiple thruster arrays. The specific impulse of an MPD thruster can be optimized to meet given mission requirements, from a few thousand seconds with heavier gas propellants up to 10,000 seconds with hydrogen propellant. In support of NASA space science and human exploration strategic initiatives, Glenn Research Center is developing and testing pulsed, MW‐class MPD thrusters as a prelude to long‐duration high power thruster tests. The research effort includes numerical modeling of self‐field and applied‐field MPD thrusters and experimental testing of quasi‐steady MW‐class MPD thrusters in a high power pulsed thruster facility. This paper provides an overview of the GRC high power electromagnetic thruster program and the pulsed thruster test facility. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649597

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A radical new Inertial Electrostatic Confinement (IEC) concept, the Magnetically‐Channeled Spherical‐IEC Array (MCSA) fusion propulsion system, was proposed earlier for use in the high performance Space Ship II fusion propulsion ship (Burton, 2003). This ship was designed for a fast manned round trip mission to Jupiter. The MCSA fusion power plant represents a key enabling technology needed for this mission. The details of the proposed MCSA design are presented here, along with a discussion of some possible experiments that could be performed to confirm key physics aspects. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649598

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Ion injection into the Inertial Electrostatic Confinement (IEC) fusion power plant used in the design of the high performance Fusion Ship II (Burton et al., 2003) is a key technological issue for development of this concept. This paper discusses the design and initial experiments with a radiofrequency (RF) ion gun designed for this purpose. The RF Gun design described here was found to have some important advantages over other ion gun designs: simple construction, a higher extraction efficiency; 10 ((mA/cm2)/W), a lower divergence; 10.8 ± 0.36 mrad, and a very intensive ion flux; 6 × 1018ions/(cm2.sec) measured at 0.27 Pa. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649599

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

From the late 1950s to the early 1970s a major program successfully developed the capability to conduct space exploration using the advanced technology of nuclear rocket propulsion. The program had two primary elements: pioneering and advanced technology work—Rover—at Los Alamos National Laboratory and its contractors provided the basic reactor design, fuel materials development, and reactor testing capability; and engine development—NERVA—by the industrial team of Aerojet and Westinghouse building on and extending the Los Alamos efforts to flight system development. This presentation describes the NERVA program, the engine system testing that demonstrated the space‐practical operation capabilities of nuclear thermal rockets, and the mission studies that point the way to most effectively use the NTR capabilities. Together, the two programs established a technology base that includes proven NTR capabilities of (1) over twice the specific impulse of chemical propulsion systems, (2) thrust capabilities ranging from 44kN to 1112kN, and (3) practical thrust‐to‐weight ratios for future NASA space exploration missions, both manned payloads to Mars and unmanned payloads to the outer planets. The overall nuclear rocket program had a unique management structure that integrated the efforts of the two government agencies involved—NASA and the then‐existing Atomic Energy Commission. The objective of this paper is to summarize and convey the technical and management lessons learned in this program as the nation considers the design of its future space exploration activities. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1649600

出版商:AIP    

年代:1904

数据来源: AIP