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A constant outward radial thrust acceleration can be used to reduce the radius of a circular orbit of specified period. Heliocentric circular orbits are designed to match the orbital period of Earth or Mars for various radial thrust accelerations and are defined as synchronous orbits. Minimum-time solar sail orbit transfers to these synchronous heliocentric orbits are presented.
Wave motions in plasma permeated by constant magnetic and gravitational fields, finding plus, minus and Alfven modes
Cadmium sulfide (Cu2s - CdS) solar cells were tested under simulated space environmental conditions. Some cells were thermally cycled with illumination from a Xenon-arc solar simulator. A cycle was one hour of illumination followed immediately with one-half hour of darkness. In the light, the cells reached an equilibrium temperature of 60 C (333 K) and in the dark the cell temperature dropped to -120 C (153 K). Other cells were constantly illuminated with a Xenon-arc solar simulator. The equilibrium temperature of these cells was 55 C (328 K). The black vacuum chamber walls were cooled with liquid nitrogen to simulate a space heat sink. Chamber pressure was maintained at 0.000001 torr or less. Almost all of the solar cells tested degraded in power when exposed to a simulated space environment of either thermal cycling or constant illumination. The cells tested the longest were exposed to 10.050 thermal cycles.
The appropriateness of the presently available X-ray and XUV multilayer emission lines for studies of solar outer atmosphere and corona is discussed. The spectral regions within which solar emission lines are formed are compared with the available multilayer passbands, with particular attention given to lines which are of interest for studying the various temperature regimes and variability time constants known to be present in the solar atmosphere. It is emphasized that, for many of the typical regions found in the outer solar atmosphere, the observable time scales for variability are determined by the ionization and recombination time scales of the plasma rather than by the inherent nature of the physical process causing the variability.
Organic solar cells (OSCs) have achieved power conversion efficiencies (PCEs) surpassing 20%, but their development remains hindered by the inherently low dielectric constant (εr) of organic semiconductors, which limits charge transport and contributes to serious recombination losses. Herein, we present a comprehensive strategy to overcome the challenge by engineering the dielectric properties of nonfullerene acceptors (NFAs). Two Y-series NFAs of BTP-N3F and BTP-C3F have been synthesized featuring trifluoromethyl (CF 3 ) end-capped alkyl side chains. This molecular design significantly enhances the dipole moment and ε r (up to ∼5.9) when compared to the reference acceptor Y6 (∼3), reducing the exciton binding energy (E b ) and improving charge transport. Furthermore, the incorporation of a high-εr polymer additive, poly(pentafluorostyrene) (PPFS), synergistically improves the active layer morphology and dielectric properties, enabling efficient charge extraction and reduced recombination losses. Devices based on the optimized D18-Cl/BTP-C3F system have achieved a record-high fill factor (FF) of 83.58% and an impressive PCE of 20.80%, setting a new benchmark for OSCs. Finally, our results underscore the pivotal role of ε r in enhancing device performance and establish a versatile pathway for advancing OSC efficiency and stability through molecular and morphological optimization.
Interplanetary plasma data taken near 1 AU by a variety of spacecraft (Imp 1, Vela 2-4, Explorer 33-35, and Heos 1) from 1963 to 1971 are used to study the long-term variations of the solar wind proton properties. An intercalibration among the different experiments is performed in order to obtain a coherent set of data. The most interesting result is a 40% reduction of the proton density between the minimum and the maximum of the solar activity cycle. The observed density variation occurs throughout the velocity range; however, a limited sample of data could suggest that at very low velocities (below 300 km/sec) the density is independent of the solar activity. The proton bulk velocity is remarkably constant during the period considered; small increases of the average speed occurring in 1968 and 1971 cannot be attributed to the solar cycle. No clear trend is exhibited by the proton temperature; differences among the various experiments probably have an instrumental origin.
It has been known for some time that Taylor series (TS) integration is among the most efficient and accurate numerical methods in solving differential equations. However, the full benefit of the method has yet to be realized in calculating spacecraft trajectories, for two main reasons. First, most applications of Taylor series to trajectory propagation have focused on relatively simple problems of orbital motion or on specific problems and have not provided general applicability. Second, applications that have been more general have required use of a preprocessor, which inevitably imposes constraints on computational efficiency. The latter approach includes the work of Berryman et al., who solved the planetary n-body problem with relativistic effects. Their work specifically noted the computational inefficiencies arising from use of a preprocessor and pointed out the potential benefit of manually coding derivative routines. In this Engineering Note, we report on a systematic effort to directly implement Taylor series integration in an operational trajectory propagation code: the Spacecraft N-Body Analysis Program (SNAP). The present Taylor series implementation is unique in that it applies to spacecraft virtually anywhere in the solar system and can be used interchangeably with another integration method. SNAP is a high-fidelity trajectory propagator that includes force models for central body gravitation with N X N harmonics, other body gravitation with N X N harmonics, solar radiation pressure, atmospheric drag (for Earth orbits), and spacecraft thrusting (including shadowing). The governing equations are solved using an eighth-order Runge-Kutta Fehlberg (RKF) single-step method with variable step size control. In the present effort, TS is implemented by way of highly integrated subroutines that can be used interchangeably with RKF. This makes it possible to turn TS on or off during various phases of a mission. Current TS force models include central body gravitation with the J2 spherical harmonic, other body gravitation, thrust, constant atmospheric drag from Earth's atmosphere, and solar radiation pressure for a sphere under constant illumination. The purpose of this Engineering Note is to demonstrate the performance of TS integration in an operational trajectory analysis code and to compare it with a standard method, eighth-order RKF. Results show that TS is 16.6 times faster on average and is more accurate in 87.5% of the cases presented.
The knowledge of minority and majority charge carrier properties enables controlling the performance of solar cells, transistors, detectors, sensors, and LEDs. Here, we developed the constant light induced magneto transport method which resolves electron and hole mobility, lifetime, diffusion coefficient and length, and quasi-Fermi level splitting. We demonstrate the implication of the constant light induced magneto transport for silicon and metal halide perovskite films. We resolve the transport properties of electrons and holes predicting the material’s effectiveness for solar cell application without making the full device. The accessibility of fourteen material parameters paves the way for in-depth exploration of causal mechanisms limiting the efficiency and functionality of material structures. To demonstrate broad applicability, we further characterized twelve materials with drift mobilities spanning from 10 –3 to 10 3 cm 2 V –1 s –1 and lifetimes varying between 10 –9 and 10 –3 seconds. The universality of our method its potential to advance optoelectronic devices in various technological fields.
The Nimbus-7 TOMS version 6 data, corrected for the instrument degradation, are analyzed to delineate the solar UV related changes in total ozone (TOZ) against background signals of dynamical origin. It is shown that the solar UV related change in TOZ over a solar cycle is about 1.5 percent that may be attributed to about 6 percent change in the solar UV flux near 200 nm. This estimate is also consistent with the solar UV related changes in TOZ over a time scale of a solar rotation. In the solar rotation case, ozone lags the solar UV by 3-4 days and its sensitivity to solar UV change is a factor of 2-3 less than for the solar cycle case. Both these effects are attributed to chemical time constants in the lower stratosphere that are comparable to the period of a solar rotation.
A simple model of solar flare radiation event particle transport is developed to permit the calculation of fluxes and related quantities as a function of distance from the sun (R). This model assumes the particles spiral around the solar magnetic field lines with a constant pitch angle. The particle angular distributions and onset plus arrival times as functions of energy at 1 AU agree with observations if the pitch angle distribution peaks near 90 deg. As a consequence the time dependence factor is essentially proportional to R/1.7, (R in AU), and the event flux is proportional to R/2.
The natural environment design requirements for the Spacelab, carried to orbital altitudes as cargo in the space shuttle bay, were presented. This includes consideration of the following: neutral atmosphere, charged particles, radiation (galactic cosmic, trapped, and solar particle events), meteoroids, and astrodynamic constants.
The observed low open-circuit voltage in 0.1 Ohm-cm solar cells is probably related to an excessively high diode saturation current. Theoretical studies conducted by Lindholm et al. (1975) and by Godlewski et al. (1975) have shown that a high saturation current could be produced by either high recombination rates or bandgap narrowing effects. A description is given of an investigation which shows that bandgap narrowing effects have a first order significance in determining the charge carrier transport controlling the open-circuit voltage of 0.1 Ohm-cm silicon solar cells.
The test procedure used and the results obtained from an evaluation test program, conducted to obtain thermal performance data on a Solaron double glazed air solar collector under simulated conditions in a solar simulator are described. A time constant test and incident angle modifier test were also conducted to determine the transient effect and the incident angle effect on the collector. These results and the results of the collector load test are also discussed. The Solaron collector absorber plate is made of 24-gage steel, the coating is baked-on black paint, the cover consists of two sheets of 1/8-inch low-iron tempered glass, and the insulation is one thickness of 3 5/8-inch fiberglass batting.
High-dispersion photoelectric scans of the interstellar 3384-A line of Ti II have been obtained for 68 stars. Column densities of Ti II are derived for the various individual kinematic components in the scans. These column densities, and those integrated over all components in the respective directions, are compared with corresponding results for Na I, Ca II, K I, H I, and H2. The column densities of titanium and hydrogen show directly that the depletion of titanium from the interstellar gas is large and variable. The abundance of titanium in the gas also varies strongly relative to the Na, K, and the grains responsible for reddening. In contrast, the titanium/calcium column-density ratio is relatively constant at about 4 times its solar value. Lower depletions are found in four out of five cases of absorption in the intercloud medium and toward each of two stars at high galactic z-distances. The column densities of Ca II and Ti II are used to estimate the electron densities in individual kinematic components. These electron densities are uncorrelated with the depletions of titanium, indicating that depletion is not a simple or unique function of local density.
Solar energy is collected by using a vertical deflector assembly, a stationary reflector and a horizontally mounted solar collector. The deflector assembly contains a plurality of vanes which change the direction of the solar energy to the vertical, while constantly keeping the same side of the deflector facing the sun. The vertical rays are then reflected off the stationary reflector and are then absorbed by the collector.
An attempt is made to correlate available observations within the framework of a simple two-component model of the full-disk flux which divides the solar surface into quiet and active areas with a constant average contrast factor for the intensity at a particular wavelength. The expected range of variability over the solar cycle of the far UV flux is examined within the 1175-2100 A wavelength range. Two possible indices of solar variability, the calcium plage index and the Zurich sunspot number, are investigated as guides to the fraction of disk covered by active regions and the possible resulting flux variability. In addition, contrast factors I(plage)/I(quiet region) are determined for various lines and continua, and the fraction of the disk covered by plages at various times is estimated. Results are in good agreement with the L-alpha fluxes of Vidal-Madjar (1975) and the broadband observations by Hinteregger (1979), but disagree with the flux variability reported by Heath and Thekaekara (1977) over the 1700-3000 A range.
The EASY5 macro component models developed for the spacecraft power system simulation are described. A brief explanation about how to use the macro components with the EASY5 Standard Components to build a specific system is given through an example. The macro components are ordered according to the following functional group: converter power stage models, compensator models, current-feedback models, constant frequency control models, load models, solar array models, and shunt regulator models. Major equations, a circuit model, and a program listing are provided for each macro component.
Nonthermal radio emissions from earth, Jupiter, Saturn, and Uranus are reviewed. The dominant source of emission at each planet appears to be AKR-like auroral emission in the X-mode. O-mode emissions are substantially responsible. There is a remarkably constant scaling factor relating the total solar wind input power into each planetary system and the AKR-like auroral emissions.