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The Water Cooler
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NASA Test Fires New RS-25 Engine
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<blockquote data-quote="Dave70968" data-source="post: 2782267" data-attributes="member: 13624"><p>"Escape velocity" probably isn't the term you meant to use. <a href="https://en.wikipedia.org/wiki/Escape_velocity" target="_blank">Escape velocity</a> is speed necessary to get away from a body's gravity. For Earth, escape velocity is 11.2 km/sec; for the moon, it's 2.4 km/sec. Thus, to escape Earth's gravity, you'd be going more than four times as fast as you'd need to go to escape the moon.</p><p></p><p></p><p></p><p>Actually, probably not. Rocket engines (specifically, the nozzles) are designed for maximum efficiency at a given air pressure; first-stage engines are going to be optimized for use at or near ground level, while higher-stage engines will be profiled to be more efficient in a vacuum. Engines for use on the moon would always be operated in a vacuum, so they'd be designed with that in mind.</p></blockquote><p></p>
[QUOTE="Dave70968, post: 2782267, member: 13624"] "Escape velocity" probably isn't the term you meant to use. [URL="https://en.wikipedia.org/wiki/Escape_velocity"]Escape velocity[/URL] is speed necessary to get away from a body's gravity. For Earth, escape velocity is 11.2 km/sec; for the moon, it's 2.4 km/sec. Thus, to escape Earth's gravity, you'd be going more than four times as fast as you'd need to go to escape the moon. Actually, probably not. Rocket engines (specifically, the nozzles) are designed for maximum efficiency at a given air pressure; first-stage engines are going to be optimized for use at or near ground level, while higher-stage engines will be profiled to be more efficient in a vacuum. Engines for use on the moon would always be operated in a vacuum, so they'd be designed with that in mind. [/QUOTE]
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NASA Test Fires New RS-25 Engine
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