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The Properties and the Nature of Light
Published in Lazo M. Manojlović, Fiber-Optic-Based Sensing Systems, 2022
Besides the energy transfer, electromagnetic radiation carries also the momentum, so when electromagnetic wave impinges the surface of some object, it exerts force. As Maxwell showed, the radiation pressure is equal to the energy density of the electromagnetic wave. The radiation pressure exerted on the object that perfectly absorbs the radiation can be found by using virtual work principle. Therefore, we will observe the electromagnetic radiation that impinges the perfectly absorbing body, as it is presented in Figure 1.4. If we allow force, which is generated by the radiation, to virtually move the object for an infinitesimally short distance δ z, the work done by this force will, according to the first principle, be equal to the change in stored electromagnetic energy. Thus, the energy conservation law gives: PA?δ?z=wA?δ?z. where P is the radiation pressure and A is the cross section of the observed elementary volume. From eq 1.36, it is simply obtained P = w.
Modular Systems for Energy Usage in Vehicles
Published in Yatish T. Shah, Modular Systems for Energy Usage Management, 2020
A few spacecraft operating within the orbit of Mars have used solar power as an energy source for their propulsion system. All current solar-powered spacecraft use solar panels in conjunction with electric propulsion, typically ion drives as these give a very high exhaust velocity and reduce the propellant over that of a rocket by more than a factor of 10. Since propellant is usually the biggest mass on many spacecraft, this reduces launch costs. Other proposals for solar spacecraft include solar thermal heating of propellant, typically hydrogen or sometimes water is proposed. An electrodynamic tether can be used to change a satellite’s orientation or adjust its orbit. Another concept for solar propulsion in space is the light sail; this doesn’t require conversion of light to electrical energy, instead relying directly on the tiny but persistent radiation pressure of light. Perhaps the most successful solar-propelled vehicles have been the “rovers” used to explore surfaces of the Moon and Mars. The 1977 and the 1997 Mars Pathfinder used solar power to propel remote-controlled vehicles. The operating life of these rovers far exceeded the limits of endurance that would have been imposed, had they been operated on conventional fuels [75, 78, 83].
Current and Outlook on Manufacturing and Processing Technologies
Published in Yoseph Bar-Cohen, Advances in Manufacturing and Processing of Materials and Structures, 2018
The use of flexible structures in the form of gossamer or inflatable systems offers enormous potential for many applications, including planetary exploration missions. Such structures can be used to reduce launch mass and stowed volume, where they are launched in a packed form, then inflated to shape and rigidized to create large structures. Gossamer structures may include solar sails, concentrators, and shields (Chmielewski and Jenkins, 2000). Solar sails are large flat spacecraft structures that provide propulsion using radiation pressure that is exerted by sunlight. It operates analogously to sailing boats, where the light provides a pushing force similar to sails being blown by wind (Figure 20.5). As an alternative to sunlight as the source, high-energy laser beams could be used to exert much greater force, and the concept is called beam sailing. Experimenting with this spacecraft concept has been done by the Japan Aerospace Exploration Agency with its Interplanetary Kite-craft Accelerated by the Radiation Of the Sun (IKAROS), which was launched on May 21, 2010, aboard an H-IIA rocket. This spacecraft has been the first to successfully demonstrate solar sail technology in interplanetary space, and on December 8, 2010, it passed at a distance of about 80,800 km (50,200 mi) from Venus.
Airborne power ultrasound for drying process intensification at low temperatures: Use of a stepped-grooved plate transducer
Published in Drying Technology, 2021
R. R. Andrés, E. Riera, J. A. Gallego-Juárez, A. Mulet, J. V. García-Pérez, J. A. Cárcel
Generally, ultrasonic energy is used to produce permanents changes in the treated medium. Its use is based on the adequate exploitation of a series of mechanisms activated by the high-intensity ultrasonic waves, such as radiation pressure, acoustic streaming, agitation, instability at the interfaces, and structural diffusion.[11] When a high-intensity ultrasonic wave propagates in a medium in the presence of obstacles, continuous radiation forces that act on the obstacles give rise to what is known as radiation pressure. The radiation pressure is linked to any wave process and has its origin in the change of momentum that the wave experiences when acting on an obstacle. These forces are intense enough to give rise to processes of drag and interaction.[3,10,23,24] As the ultrasonic absorption processes on the high-intensity waves, radiation forces are generated inducing movements in the irradiated fluid, which improve the transfer of matter and heat.[10,24–26]
The time step constraint in radiation hydrodynamics
Published in Geophysical & Astrophysical Fluid Dynamics, 2020
In this paper, we discuss two distinct models where severe time step constraints have been encountered. One is the model of Spiegel (2006) and the other is a local model of an accretion disc, similar to that of Coleman et al. (2018). Radiation pressure is included in the former, but not in the latter. It will turn out that the time step constraints are quite different from each other in the two cases, although this difference is not explicitly linked to the presence or absence of radiation pressure. Nevertheless, when the radiation pressure becomes extremely large, it can in principal also restrict the time step. We discuss this possibility at the end of our penultimate section 5.