A Comparison of Laser and Microwave Approaches to CW Beamed Energy Launch

One approach to beamed energy propulsion uses a solid heat exchanger to absorb energy from a distant source and transfer it to a working fluid. Systems of this type can be designed using either microwave or laser sources. In general, microwave sources have been expected to be less expensive than lasers for a given power, but to be more limited in range and/or energy density. With the development of high power millimeter-wave sources and low-cost diode laser arrays, both assumptions are open to question. In this paper, we compare current and projected microwave and laser source technologies for a 100-kilogram-class ground-to-orbit launch system and identify key issues affecting the system-level trade between the two approaches

BATSE Observations of Gamma-Ray Burst Spectra. IV. Time-Resolved High-Energy Spectroscopy

We report on the temporal behavior of the high-energy power law continuum component of gamma-ray burst spectra with data obtained by the Burst and Transient Source Experiment. We have selected 126 high fluence and high flux bursts from the beginning of the mission up until the present. Much of the data were obtained with the Large Area Detectors, which have nearly all-sky coverage, excellent sensitivity over two decades of energy and moderate energy resolution, ideal for continuum spectra studies of a large sample of bursts at high time resolution. At least 8 spectra from each burst were fitted with a spectral form that consisted of a low-energy power law, a spectral break at middle energies and a high-energy continuum. In most bursts (122), the high-energy continuum was consistent with a power law. The evolution of the fitted high-energy power-law index over the selected spectra for each burst is inconsistent with a constant for 34% of the total sample. The sample distribution of the average value for the index from each burst is fairly narrow, centered on -2.12. A linear trend in time is ruled out for only 20% of the bursts, with hard-to-soft evolution dominating the sample (100 events). The distribution for the total change in the power-law index over the duration of a burst peaks at the value -0.37, and is characterized by a median absolute deviation of 0.39, arguing that a single physical process is involved. We present analyses of the correlation of the power-law index with time, burst intensity and low-energy time evolution. In general, we confirm the general hard-to-soft spectral evolution observed in the low-energy component of the continuum, while presenting evidence that this evolution is different in nature from that of the rest of the continuum.Comment: 30 pages, with 2 tables and 9 figures To appear in The Astrophysical Journal, April 1, 199

Ecological foresight in the nuclear power of XXI century

The access to reliable sources of energy is the key to sustainable development of mankind. The major part of the energy consumed by people is generated with a chemical reaction of fossil fuel burning. This leads to quick depletion of natural resources and progressing environmental pollution. The contribution of the renewable energy sources to the general energy production remains insignificant. A modern 1,000 MW coal-fired thermal power plant (TPP) burns 2.5 million tons of coal per year and produces significant amount of solid and gaseous waste. TPPs are the largest consumers of atmospheric oxygen and sources of carbon dioxide. A nuclear power plant (NPP) of the same power consumes less than 50 tons of fuel per year. Environmentally significant NPP’s waste (liquid, solid and gaseous) is carefully collected, reduced in volume (evaporation, filtering, compaction, incineration, etc.) and securely isolated from the environment at the plant. The annual volume of waste for storage is less than 100 m3. The waste is under the control of a special NPP’s service and regulatory authorities. The energy of fission reaction millions of times exceeding the energy of burning has an enormous potential that mankind can receive. Four hundred and thirty-three nuclear power units with a total capacity of about 400 GW exist in the world. The accident at the Fukushima Daiichi NPP in Japan in March 2011 caused anxiety about nuclear safety throughout the world and raised questions about the future of nuclear power. Now, it is clear that the use of nuclear power will continue to grow in the coming decades, although the growth will be slower than was anticipated before the accident. Many countries with existing nuclear power programmes plan to expand them. Many new countries, both developed and developing, plan to introduce nuclear power. Some countries, such as Germany, plan to abandon nuclear energy. The IAEA’s latest projections show a steady rise in the number of NPPs in the world in the next 20 years. They project a growth in nuclear power capacity by 23% by 2030 in the low projection and by 100% in the high projection [1,2]. The basis of modern nuclear power comprises water-cooled nuclear reactors which use the energy potential of natural uranium inefficiently (thermal reactors). The thermal reactors use isotope U-235 in which the content of natural uranium is <1%. Breeder reactors are capable of using the significant part of energy potential, which is unavailable to thermal light water reactors. As a result, the same starting quantity of uranium can produce 50 times more energy. These reactors can transform U-238 into fissile Pu-239 in larger amounts than they consume fissile material. This feature is called ‘breeding’ [3]. The key problem of using the basic benefitsv of nuclear power is to ensure the safety of its use, as well as decommissioning and reliable isolation of process waste from the biosphere. The long-term large-scale nuclear power should possess guaranteed safety, economic stability and competitiveness, absence of the raw material base restrictions for a long period of time and environmental sustainability (low waste). The nuclear power systems with fast neutron reactors and liquid metal coolant can satisfy these conditions. More than 40 years of Russian experience in the field of construction and operation of sodium fast reactors makes it possible to summarize and analyze the ecological features of reactors of this type, the possibility of their use for sustainable energy supply of mankind and solving environmental problems

Program THEK energy production units of average power and using thermal conversion of solar radiation

General studies undertaken by the C.N.R.S. in the field of solar power plants have generated the problem of building energy production units in the medium range of electrical power, in the order of 100 kW. Among the possible solutions, the principle of the use of distributed heliothermal converters has been selected as being, with the current status of things, the most advantageous solution. This principle consists of obtaining the conversion of concentrated radiation into heat by using a series of heliothermal conversion modules scattered over the ground; the produced heat is collected by a heat-carrying fluid circulating inside a thermal loop leading to a device for both regulation and storage

Interstellar travels aboard radiation-powered rockets

We model accelerated trips at high-velocity aboard light sails (beam-powered propulsion in general) and radiation rockets (thrust by anisotropic emission of radiation) in terms of Kinnersley's solution of general relativity and its associated geodesics. The analysis of radiation rockets relativistic kinematics shows that the true problem of interstellar travel is not really the amount of propellant, nor the duration of the trip but rather its tremendous energy cost. Indeed, a flyby of Proxima Centauri with an ultralight gram-scale laser sail would require the energy produced by a 1 GW power plant during about one day, while more than 15 times the current world energy production would be required for sending a 100 tons radiation rocket to the nearest star system. The deformation of the local celestial sphere aboard radiation rockets is obtained through the null geodesics of Kinnersley's spacetime in the Hamiltonian formulation. It is shown how relativistic aberration and Doppler effect for the accelerated traveller differ from their description in special relativity for motion at constant velocity. We also show how our results could interestingly be extended to extremely luminous events like the large amount of gravitational waves emitted by binary black hole mergers.Comment: 18 pages, 11 figures ; Open Acces

Fast spectral fitting of hard X-ray bremsstrahlung from truncated power-law electron spectra

&lt;p&gt;&lt;b&gt;Context:&lt;/b&gt; Hard X-ray bremsstrahlung continuum spectra, such as from solar flares, are commonly described in terms of power-law fits, either to the photon spectra themselves or to the electron spectra responsible for them. In applications various approximate relations between electron and photon spectral indices are often used for energies both above and below electron low-energy cutoffs.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Aims:&lt;/b&gt; We examine the form of the exact relationships in various situations, and for various cross-sections, showing that empirical relations sometimes used can be highly misleading especially at energies below the low-energy cutoff, and consider how to improve fitting procedures.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; We obtain expressions for photon spectra from single, double and truncated power-law electron spectra for a variety of cross-sections and for the thin and thick target models and simple analytic expressions for the non-relativistic Bethe-Heitler case.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; We show that below the low-energy cutoff Kramers and other constant spectral index forms commonly used are very poor approximations to accurate results, but that our analytical forms are a good match; and that above a low-energy cutoff, the Kramers and non-relativistic Bethe-Heitler results match reasonably well with results for up to energies around 100 keV.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; Analytical forms of the non-relativistic Bethe-Heitler photon spectra from general power-law electron spectra are good match to exact results for both thin and thick targets and they enable much faster spectral fitting than evaluation of the full spectral integrations.&lt;/p&gt

Atmosphere, Magnetosphere and Plasmas in Space (AMPS). Spacelab payload definition study. Volume 7, book 3: Supporting Research and Technology (SR and T) report

The items identified as required to support the AMPS mission and requiring SR and T support and further work are: (1) a general purpose Experiment Pointing Mount; (2) a technique for measuring the attitude of the pallet-mounted or deployed experiments; (3) the development of a common optics cryogenically cooled interferometer spectrometer; (4) the development of a differential absorption lidar system for the measurement of ozone densitites in the earth's atmosphere; (5) the development of dc to dc power processors which are capable of converting energy stored in a capacitor system at 500 V to energy supplied to equipment operating at 40 kV and at 20 kW (eventually up to 100 kW); and (6) the development of a magnetic or possibly electrostatic deflection system capable of bending the beam of an electron accelerator. A data sheet is included for each item, briefly describing the background and need for each item, and the general objectives of the required development, and identifying the schedule requirements in support of the AMPS program

The Pulse Scale Conjecture and the Case of BATSE Trigger 2193

The pulses that compose gamma-ray bursts (GRBs) are hypothesized to have the same shape at all energies, differing only by scale factors in time and amplitude. This "Pulse Scale Conjecture" is confirmed here between energy channels of the dominant pulse in GRB 930214c (BATSE trigger 2193), the single most fluent single-pulsed GRB that occurred before May 1998. Furthermore, pulses are hypothesized to start at the same time independent of energy. This "Pulse Start Conjecture" is also confirmed in GRB 930214c. Analysis of GRB 930214c also shows that, in general, higher energy channels show shorter temporal scale factors. Over the energy range 100 KeV - 1 MeV, it is found that the temporal scale factors between a pulse measured at different energies are related to that energy by a power law, possibly indicating a simple relativistic mechanism is at work. To test robustness, the Pulse Start and Pulse Scale Conjectures were also tested on the four next most fluent single-pulse GRBs. Three of the four clearly passed, with a second smaller pulse possibly confounding the discrepant test. Models where the pulse rise and decay are created by different phenomena do not typically predict pulses that satisfy both the Pulse Start Conjecture and the Pulse Scale Conjecture, unless both processes are seen to undergo common time dilation.Comment: 19 pages, 9 figures, analysis revised and extended, accepted to Ap

SAS-2 observations of the galactic gamma radiation from the Vela region

Data from a scan of the galactic plane by the SAS-2 high energy gamma ray experiment in the region 250 deg l2 290 deg show a statistically-significant excess over the general radiation from the galactic plane for gamma radiation of energy 100 MeV in the region 260 deg l2 270 deg and -7.5 deg b2 0 deg. If the enhanced gamma radiation results from interactions of cosmic rays with galactic matter, as the energy spectrum suggests, it seems reasonable to associate the enhancement with large scale galactic features, such as spiral arm segments in that direction, or with the region surrounding the Vela supernova remnant, with which PSR 0833-45 is associated. If the excess is attributed to cosmic rays released from this supernova interacting with the interstellar matter in that region, then on the order of 3.10 to the 50th power ergs would be released by that supernova in the form of cosmic rays