Fwd: Next Big Future - 2 new articles

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Date: Sun, Jun 2, 2013 at 2:20 PM
Subject: Next Big Future - 2 new articles
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"Next Big Future" - 2 new articles

1. Small modular reactors might end up being lower cost energy if the full advantages of factory mass production can be leveraged
2. Electric Sail components and technical details
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Small modular reactors might end up being lower cost energy if the full advantages of factory mass production can be leveraged Analysts and decision makers frequently want estimates of the cost of technologies that have yet to be developed or deployed. (PNAS - Expert assessments of the cost of light water small modular reactors) Small modular reactors (SMRs), which could become part of a portfolio of carbon-free energy sources, are one such technology. Existing estimates of likely SMR costs rely on problematic top-down approaches or bottom-up assessments that are proprietary. When done properly, expert elicitations can complement these approaches. We developed detailed technical descriptions of two SMR designs and then conduced elicitation interviews in which we obtained probabilistic judgments from 16 experts who are involved in, or have access to, engineering-economic assessments of SMR projects. Here, we report estimates of the overnight cost and construction duration for five reactor-deployment scenarios that involve a large reactor and two light water SMRs. Consistent with the uncertainty introduced by past cost overruns and construction delays, median estimates of the cost of new large plants vary by more than a factor of 2.5. Expert judgments about likely SMR costs display an even wider range. Median estimates for a 45 megawatts-electric (MWe) SMR range from $4,000 to $16,300/kWe and from $3,200 to $7,100/kWe for a 225-MWe SMR. Sources of disagreement are highlighted, exposing the thought processes of experts involved with SMR design. There was consensus that SMRs could be built and brought online about 2 years faster than large reactors. Experts identify more affordable unit cost, factory fabrication, and shorter construction schedules as factors that may make light water SMRs economically viable.   A problem is that current [US] law prohibits more than two reactors from being operated from the same control room, making it illegal to site lots of the small modular reactors together. However, most of the experts believed that, if legal, installing a series of the small reactors could increase economies of scale and reduce costs. The main advantage to a small module reactor is the standardized factory production, which would certainly be cheaper than custom components. China does not have the limitation on control rooms. Read more »      • Email to a friend • Article Search • Electric Sail components and technical details The electric solar wind sail (E-sail) is a new type of propellantless propulsion system for Solar System transportation, which uses the natural solar wind for producing spacecraft propulsion. This paper discusses a mass breakdown and a performance model for an E-sail spacecraft that hosts a scientifi c payload of prescribed mass. In particular, the model is able to estimate the total spacecraft mass and its propulsive acceleration as a function of various design parameters such as the tethers number and their length. A number of subsystem masses are calculated assuming existing or near-term E-sail technology. In light of the obtained performance estimates, an E-sail represents a promising propulsion system for a variety of transportation needs in the Solar System.   A baseline, full-scale, E-sail propulsion system comprises 2000 km of total main tether length (for example 100 tethers, each one being 20 km long), with 25 kV tether voltage, 960W electron gun power consumption and 1.16 Newtons nominal thrust at 1 au from the Sun. If the main tethers are su fficiently long such that the potential sheath overlapping between them is negligible, the propulsive thrust varies as 1=r, where r is the Sun-spacecraft distance. Note, for comparison, that in the classical photonic solar sail the propulsive thrust decreases more rapidly (that is, as 1=r2) with the solar distance. Therefore the E-sail concept is especially attractive for a mission towards the outer Solar System, such as a Jupiter rendezvous or a mission towards the Heliopause and the Solar System boundaries. Esail schematic Read more »      • Email to a friend • Article Search • More Recent Articles Nasal Spray gene therapy could protect against flu and pandemic flu Electric Solar Sail Is the Phillippines shifting to prolonged 6-7% annual GDP growth ? NASA Eagleworks Space Warping and Quantum Vacuum Plasma Thruster - Propellentless propulsion Attosecond clock accuracy that is one thousand times better than atomic clocks of 20 years ago

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