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	<title>SpaceBuild &#187; Nuclear</title>
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	<link>http://www.spacebuild.net/s1</link>
	<description>Spacecraft technology</description>
	<lastBuildDate>Thu, 10 Feb 2011 20:59:53 +0000</lastBuildDate>
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		<title>Project Prometheus – Nuclear Electric Engines</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/242/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/242/#comments</comments>
		<pubDate>Tue, 11 Jan 2011 14:57:48 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>
		<category><![CDATA[Prometheus]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=242</guid>
		<description><![CDATA[This project is a NASA / JPL attempt to develop a more heavily instrumented craft travelling farther from the Sun. The concept would need to power its ion thrusters with a nuclear fission reactor and a system for converting the reactor&#8217;s heat to electricity. This could give the craft more than 100 times more power than a non-fission system of comparable weight. Below is a conceptual design for the Prometheus 1 spacecraft would place a large array of heat-shedding radiator panels between the spacecraft&#8217;s power source and ion-propulsion thrusters. In order to explore the distant reaches of the solar system, new technologies must be developed. These technologies would allow spacecraft to travel further and conserve more energy until they reach their destination. Developing a safe nuclear power capability would enable NASA to meet its scientific goals for the next several decades and more thoroughly explore the outer edges of the solar system. The Jupiter Icy Moons Orbiter Mission would demonstrate that a nuclear fission reactor can be developed for use in deep space, flown safely, and operated reliably on long-duration missions in the deep space environment to return valuable science. A nuclear fission reactor could produce unprecedented amounts of electrical [...]]]></description>
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		<title>Project Orion – Nuclear Pulse Units (NPU)</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/238/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/238/#comments</comments>
		<pubDate>Tue, 11 Jan 2011 08:54:43 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>
		<category><![CDATA[npu]]></category>
		<category><![CDATA[project orion]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=238</guid>
		<description><![CDATA[While the US and the Soviet Union were beginning work on NTR systems, a group of American researchers also considered a more direct and dramatic way to use nuclear power to propel a spaceship: detonate small atomic bombs behind it. The ORION project, as it was named, seems to have originated with Dr. Theodore B. Taylor, well-known nuclear weapons designer. In 1957, he was working at General Atomic, a branch of the General Dynamics conglomerate, in San Diego, California, when the Soviet Union launched Sputnik I, the first Earth satellite. General Atomic was promoting the peaceful uses of atomic power, and Taylor thought that America could catch up with the Soviets by building a really big spacecraft, a true &#8220;spaceship&#8221;, powered by atomic bombs. The idea of a spaceship powered by atomic bombs had been around for a few years, but nobody had done any more than some conceptual paper studies of the idea. Taylor did some paper studies of his own and came to the conclusion that the bombs would be small as such things went, with only a few kilo-tonnes of explosive yield. Even at that size, they would be about a million times more powerful than a [...]]]></description>
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		<title>Gas Core Nuclear Rocket (GCNR) Engines</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/236/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/236/#comments</comments>
		<pubDate>Mon, 10 Jan 2011 20:54:06 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>
		<category><![CDATA[gcnr]]></category>
		<category><![CDATA[plasma]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=236</guid>
		<description><![CDATA[Researchers at the Los Alamos National Laboratory have also considered another interesting NTR propulsion scheme, known as a &#8220;gas core nuclear rocket (GCNR)&#8221;. In a GCNR, hydrogen is pumped into one end of a cylindrical reaction chamber, with an exhaust at the other end. The hydrogen expands as it passes through the chamber, and not all of it goes out the exhaust, instead flowing back up the chamber. This creates a toroidal vortex of hydrogen gas that can be used for fission reaction containment. Dust-sized particles of uranium are injected into the toroid and accumulate at its center. A number of long cylinders are mounted on the interior of the reaction chamber outside the toroid. These cylinders normally absorb radiation emitted by the uranium, but they can be rotated to reflect it, initiating a fission reaction. The cylinders are the equivalent of control rods in an Earth-based reactor and were apparently featured in earlier NTR designs. Once fission begins in the center of the hydrogen gas toroid, the high temperatures heat the gas into a plasma, which flies out the exhaust at high velocity to provide thrust. A small magnetic nozzle could be used to ensure that the uranium remains [...]]]></description>
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		<title>Nuclear Thermal Rocket (NTR) Engines</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/234/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/234/#comments</comments>
		<pubDate>Sun, 09 Jan 2011 20:53:10 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>
		<category><![CDATA[irgit]]></category>
		<category><![CDATA[nerva]]></category>
		<category><![CDATA[ntr]]></category>
		<category><![CDATA[pbr]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=234</guid>
		<description><![CDATA[The idea of using atomic power as the basis for a rocket engine pre-dates the First World War, but at that time neither liquid rocket engines nor atomic power were realities, and these concepts were essentially speculations about speculations. However, by the end of World War II, both large liquid-fuel rocket engines and atomic reactors were working technology. In 1946, Douglas Aircraft performed the first formal study of the use of nuclear power for rocket propulsion, followed by a study performed in 1947 by Dr. Hsue-Shen Tsien, then at MIT. With enthusiasm for space exploration and nuclear power rising in the 1950s and into the 1960s, interest in using &#8220;nuclear thermal rockets (NTR)&#8221; reached a high pitch. An NTR is very simple in concept. A light propellant, usually hydrogen, is pumped through a reactor core, which heats it to high temperatures, on the order of 2,500 degrees Celsius, and spews it out as a high-velocity exhaust. An NTR provides twice the exhaust velocity and about 3.5 times the specific impulse of LOX-RP propulsion. However, the improved mass ratio is partially cancelled by the mass of the reactor, and particularly the mass of the reactor shielding. For this reason, many NTR [...]]]></description>
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		<title>Nuclear Magnetic Confinement Fusion (MCF) Engines</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/230/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/230/#comments</comments>
		<pubDate>Sat, 08 Jan 2011 20:50:45 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>
		<category><![CDATA[mcf]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=230</guid>
		<description><![CDATA[While an inertial confinement fusion (ICF) would use lasers or particle beams to achieve fusion, a magnetic confinement fusion (MCF) might achieve fusion by confining plasma with strong magnetic fields. This should be possible, since the fusion plasma is composed primarily of ions and electrons that are susceptible to magnetic forces. The fusion plasma is carried to the magnetic nozzle by magnetic fields inside the reactor. Mixing a propellant such as hydrogen to the plasma reduces the specific impulse and increases the thrust level. The most common configuration considered for MCF propulsion systems is the &#8220;tandem mirror&#8221; system shown in the schematic below. This system uses magnets to confine the plasma, with two magnetic &#8220;mirrors&#8221; for to confine the plasma at each end. One mirror is made slightly weaker (&#8220;leaky&#8221;), which permits some of the plasma to escape, producing propulsive thrust. While recent estimates for this system suggest performance similar to ICF systems, tandem mirror system is very long (~.5 km), maximising plasma residence time.]]></description>
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		<title>Nuclear Inertial Confinement Fusion (ICF) Engines</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/228/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/228/#comments</comments>
		<pubDate>Fri, 07 Jan 2011 20:50:03 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=228</guid>
		<description><![CDATA[This would use high-power lasers or particle beams to compress a pellet of fusion fuel (typically deuterium-tritium, D-T), heating it to fusion conditions. Functionally, this would work by placing the fuel pellet at the focal point of several lasers or particle beams. Together, they would compress and heat the pellet at the same time. Conforming to Newton&#8217;s Third Law, the compression of the pellet is balanced by an equal and opposite outward explosion of the fuel pellet. Theoretically, the pellet&#8217;s own inertia would be enough to confine the plasma long enough to achieve fusion. Unfortunately, systems needed to drive the ICF reaction are large, heavy and dependant on electrical power. This makes ICF unattractive to near-term spacecraft design. Luckily, there is another option for fusion propulsion.]]></description>
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		<slash:comments>0</slash:comments>
		</item>
		<item>
		<title>Early Nuclear Propulsion attempts</title>
		<link>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/226/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/nuclear-propulsion/226/#comments</comments>
		<pubDate>Thu, 06 Jan 2011 20:48:46 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Nuclear]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=226</guid>
		<description><![CDATA[In the late 1960s and early 1970s, the U.S. developed a nuclear rocket. The fissionable material in the graphite fuel element was in the form of particles of uranium carbide coated with pyrolytic carbon. The engine that was developed as a result of this program was called NERVA (Nuclear Engine for Rocket Vehicle Application). NERVA was designed to operate at 1500 MW, provide 333 kN of thrust at a specific impulse of 825 lbf-s/lbm, and have an engine weight of 10.4 metric tons. It was engineered for a ten-hour life and sixty operating cycles. (Frisbee, 2000k) The NERVA engine was nearly completely developed when the project was terminated in 1972. Since then, there has been a limited amount of research done on fuels and materials, but they indicate that with modern materials and technologies, a NERVA-derivative engine could achieve an Isp in the 900 lbf-s/lbm range. Fusion There are two major methods for providing the confinement necessary to sustain a fusion reaction: inertial confinement fusion (ICF), and magnetic confinement fusion (MCF). These confinement schemes result in two very different propulsion system designs.]]></description>
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		<item>
		<title>Nuclear Thermal Propulsion</title>
		<link>http://www.spacebuild.net/s1/general/222/</link>
		<comments>http://www.spacebuild.net/s1/general/222/#comments</comments>
		<pubDate>Wed, 05 Jan 2011 20:47:23 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[General]]></category>
		<category><![CDATA[Nuclear]]></category>

		<guid isPermaLink="false">http://www.spacebuild.net/s1/?p=222</guid>
		<description><![CDATA[Radiation created by nuclear technologies is dangerous to both humans and their machines. Any use of nuclear propulsion technology would have to be accompanied by the use of extensive shielding and &#8220;hardening.&#8221; The potential advantages of nuclear propulsion over chemical methods are staggering. The energy that is available from nuclear reactions (fission, fusion, and matter-antimatter annihilation) can exceed a hundred times that of chemical reactions. Fission The energy available from a unit mass of fissionable material is approximately 107 times larger than that available from the most energetic chemical reactions. A &#8220;typical&#8221; solid-core nuclear rocket engine utilising fissionable material is shown in the diagram below. In this engine, the propellant is heated as it passes through a heat-generating solid fuel core (nuclear reactor). Material constraints are a limiting factor in the performance of solid core nuclear rockets. The maximum operating temperature of the working fluid (e.g., hydrogen) must be less than the melting point of the fuel, moderator, and core structural materials. This corresponds to specific impulses of around 800 to 900 lbf-s/lbm. (Frisbee, 2000k)]]></description>
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