Subject:
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Re: A dark blue starfighter
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Thu, 20 Oct 2005 17:50:52 GMT
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Viewed:
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2973 times
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In lugnet.space, Ryan Wood wrote:
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In lugnet.space, Tony Hafner wrote:
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Nits only, but:
Logically, the engine exhausts seem small and are so far below the center
of mass that this would never work in space... but they look so durn good!
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I don’t understand the science of real spaceflight, but I thought the
engines worked pretty well where they are!
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Don’t get me wrong- they look great. And a lot of popular sci-fi (especially
Anime) does the same thing. This is Lego, where for the most part style trumps
reality.
I’m assuming Newtonian (reactionary) physics. In other words,
you’re pushing something out behind you to propel yourself forward, as opposed
to hyperspace, warp bubbles, gravitic or magnetic propulsion, etc. Rocket
engines and fusion thrusters would typically be Newtonian reaction thrusters.
The basic principle is that the center of thrust needs to push through the
center of mass. Picture a line running up the tailpipe- the ship needs to
balance along that line. If you have multiple engines, you sort of average
their centerlines. If the ship isn’t balanced on that line, it will tumble.
In atmosphere, you would still want to be mostly balanced on the centerline, but
you can use aerodynamics to make up for some degree of offset. In space it’s
way more critical. You can use directional thrusters to prevent tumbling, but
unless you’re willing to spend a ton of fuel on it, that only works for small
corrections.
I found an article on the web on
lunar module stability. It covers this
subject in very readable terms.
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