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Towing Asteroids by Gravity
I'm intrigued as to why there are no references to the above in any of the
'space' newsgroups. Do you guys know something that the public doesn't? It seemed such an interesting idea to me. At risk of embarrassing myself before some clever people, I played with some figures in a spreadsheet and was startled as to how little gravitational attraction the '20 ton space craft' would have. But what if it had hydraulic grabs (very long arms, to fragile to be deployed in Earth gravity) and picked a rock from the asteroid mass of a few hundred tons? Thoughts please. Dave W. |
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Towing Asteroids by Gravity
Dave W wrote:
I'm intrigued as to why there are no references to the above in any of the 'space' newsgroups. um, I think you may be under the false impression that doing this would somehow magically save fuel or something. If I understand you correctly, you seem to think that if I move a large, and if that large body's gravity pulls a smaller body, then I am pulling the smaller body for free. Sorry, but it don't work that way. The smaller, "towed" body pulls back on the larger body, and you expend exactly the same about of fuel as you would expend if you connected then up via a cable and pulled them both. I note that this is similar to a misconception that I often hear voiced about magnetic rail guns. Many people seem to think that there would be no recoil in such a gun, because "the gun isn't pushing the bullet, the magnet is pushing it." It just doesn't work that way. The gun is pushing the bullet, and the bullet is pushing back on the gun. |
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Towing Asteroids by Gravity
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Towing Asteroids by Gravity
I note several grammar errors in my Nov 23 post and I think they make
it difficult to understand. I've corrected the errors (that I see) in the text below. Sorry! Dave W wrote: I'm intrigued as to why there are no references to the above in any of the 'space' newsgroups. um, I think you may be under the false impression that doing this would somehow magically save fuel or something. If I understand you correctly, you seem to think that if I move a large body (such as an asteroid), and if that large body's gravity pulls a smaller body (a towed asteroid), then I am pulling the smaller body for free (without expending additional fuel). Sorry, but it don't work that way. The smaller, "towed" body pulls back on the larger body, and you expend exactly the same amount of fuel as you would expend if you connected then up via a cable and pulled them both. I note that this is similar to a misconception that I often hear voiced about magnetic rail guns. Many people seem to think that there would be no recoil in such a gun, because "the gun isn't pushing the bullet, the magnet is pushing it." It just doesn't work that way. The gun is pushing the bullet, and the bullet is pushing back on the gun. |
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Towing Asteroids by Gravity
wrote in message oups.com... I note several grammar errors in my Nov 23 post and I think they make it difficult to understand. I've corrected the errors (that I see) in the text below. Sorry! Dave W wrote: I'm intrigued as to why there are no references to the above in any of the 'space' newsgroups. um, I think you may be under the false impression that doing this would somehow magically save fuel or something. If I understand you correctly, you seem to think that if I move a large body (such as an asteroid), and if that large body's gravity pulls a smaller body (a towed asteroid), then I am pulling the smaller body for free (without expending additional fuel). Sorry, but it don't work that way. The smaller, "towed" body pulls back on the larger body, and you expend exactly the same amount of fuel as you would expend if you connected then up via a cable and pulled them both. Actually, using gravity to tow the body is likely less efficient, because you have to angle your engine's exhaust off the centerline which goes from the engine through the center of mass of the body you're trying to tow. To balance this out, you use engines in pairs. This extra angle will result in some loss of efficiency when compared to landing on the body and orienting your engine(s) such that the exhaust is expelled along the centerline which goes from the engine through the center of mass of the body. The advantage of towing the body with gravity is that you don't have to worry about other issues, like designing your spacecraft to not only land on, but affix itself to a body which has potentially unknown surface features and material properties. Jeff -- Remove icky phrase from email address to get a valid address. |
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