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	<title>SpaceBuild &#187; Solar</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>Solar Thermal Rocket (STR)</title>
		<link>http://www.spacebuild.net/s1/propulsion/solar-propulsion/240/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/solar-propulsion/240/#comments</comments>
		<pubDate>Mon, 10 Jan 2011 20:56:26 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Solar]]></category>
		<category><![CDATA[sotv]]></category>
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		<description><![CDATA[Ultimately, the unsolved problem of radioactive fallout killed ORION for good. Any ORION launch would have led to public protests, and the Atmospheric Test-Ban Treaty, signed in August 1963, basically made an ORION launch illegal. ORION was finally canned for good in December 1965. It remains an interesting footnote to a time when people were crazy about space, crazy about the atom, and thought they could accomplish anything. ORION proved to be a dead end, but NTR remains attractive. It is basically a simple idea, involving no more than heating up a gas to use for an exhaust jet. The biggest drawback is that the means that it uses to heat up the gas, nuclear power, is unfashionable these days. NASA has considered an alternative approach that is much trendier, in which solar power is used to heat up a propellant instead of a nuclear reactor. The idea is not new, having been proposed by German-American space flight engineer Krafft Ehricke in 1956, but little was done on the concept until recently. In 1997, NASA launched a study of such a &#8220;solar thermal rocket (STR)&#8221; engine named &#8220;Shooting Star&#8221;. Shooting Star was envisioned strictly as a test system, using a [...]]]></description>
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		<title>Solar Propulsion</title>
		<link>http://www.spacebuild.net/s1/propulsion/solar-propulsion/14/</link>
		<comments>http://www.spacebuild.net/s1/propulsion/solar-propulsion/14/#comments</comments>
		<pubDate>Tue, 14 Jul 2009 17:42:30 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Solar]]></category>
		<category><![CDATA[Propulsion]]></category>
		<category><![CDATA[solar]]></category>

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		<description><![CDATA[Solar Propulsion Interplanetary Solar Sails A solar sail is a spacecraft that has an immense, lightweight mirror attached to it. It derives its propulsion by being pushed by light reflecting off of the mirror, instead of traditional rocket engines. The light used could be supplied by sunlight or lasers placed in orbit. Sunlight exerts a very gentle force. There are two identified ways to deploy a sail and keep it rigid. One is to use a deployment frame to maintain the sail shape, with the advantag that shape and position of the sail can be controlled, but at teh expense of having to deploy a large structure. the other method is to use centrifugal force to both deploy and maintain the sail structure through keeping it spinning. The power of sunlight in space at Earth&#8217;s distance from the sun is between 1.3-1.4 kilowatts per square meter. When you divide 1.4 kilowatts by the speed of light, about 300 million meters per second, the result is very small. A square mirror 1 kilometre on a side would only feel about 9 Newton or 2 pounds of force. Fortunately, space is very empty and clean compared to Earth, so there is plenty [...]]]></description>
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