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The Gyroscope Forum |
23 November 2024 20:54
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Welcome to the gyroscope forum. If you have a question about gyroscopes in general,
want to know how they work, or what they can be used for then you can leave your question here for others to answer.
You may also be able to help others by answering some of the questions on the site.
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Question |
| Asked by: |
Nitro MacMad |
| Subject: |
understanding basics |
| Question: |
Dear webmaster,
Thank you for considering re-examining the influence of gyro-dynamics on a cornering bike. This, by the way, was not intended as a dig at this web site but at an American teacher who should know better.
Could you or one of the visitors to this site explain a cause and effect to which I cannot find the answer? When an orbiting spacecraft approaches another to dock, an interesting phenomenon not unlike precessional reactions comes into play in most planes. This caused any amount of problems for early astronauts until computers got a bit better than a Sir Clive Sinclair calculator, and were ably to take on this non-intuitive task.
If you want to go up (in relation to the Earth), you have to throw material not, as might be thought, out the bottom of the craft but out the back. If you wish to move forwards toward the docking port of the other craft, you have to throw material out the top. If you wish to go down you have to throw material out the front and if you want to go backwards, you have to throw material out the bottom. All of the above moves are, like gyros, strange to start with but I understand them (please say if you don‘t and I‘ll try to explain in a way that can be read in less than a week).
Am I correct, though, that if you wanted to move your craft to the left, the intuitive takes over again and material needs be thrown out of the right and conversely if you wanted to go right you would need to throw stuff to the left?
Come on you bright US of A space scientists lets have some help here in this backward motherland! (By the way, please tell Boston we do not want the tea back ((have you ever tasted salt water tea?)) - just the accent and the good manners!).
Kind regards
NM
PS Would any Americans please excuse the stereotypical remark about Boston but, as I hate flying, my view of the “land of the fee” is, of necessity, based on American TV programmes (Sorry, programs). I hope to save enough to “boat it” one day and find if it really is like Sergeant Ernie Bilko and Lucille Ball and “Cheers” say and if your wonderful Pogo possum will ever make President - what do you mean he is?
PPS My spell checker (wife, lawyer, politically correct humour adviser and all round boss and spoilsport) says that I should not make jokes that might be taken badly. However she will have to go to bed soon and was daft enough too show me how to transfer “word” (hcht - ptooee) to web first………….Hm! Sorry anyway, if I have upset anyone - I suppose I should write before the Neuf (that’s Chateau Neuf du Pape) is put in front of me.
Have a good week everyone.
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| Date: |
28 June 2004
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Answers (Ordered by Date)
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| Answer: |
Ram Firestone - 28/06/2004 19:02:50
| | | I think you are talking about objects in earth's orbit. I don't know the details but when you are docking with another craft you have to remember that both are moving around the earth. Therefore you need to change the orbit of one so it approaches the other. I don’t believe this is a gyroscopic effect however. It has more to do with gravity. If you are in open space where the effects of gravity are much less, then conservation of momentum laws take over.
Ram
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| Report Abuse |
| Answer: |
Nitro Macmad - 02/07/2004 18:15:12
| | | Dear Ram,
Thank you for replying to my last. I must apologise for my usual waffle as it has made you scan through (don’t we all?) and miss my point and my question.
My point was that the motion of orbiting craft represents a further example (as well as gyro - dynamics) of our need to question (the opposite part of) Newton’s third. We just seem to have unquestioningly accepted the way the conservation of momentum law is blindly thown in as though that excuses this shortcoming in the third law. Up, down, forward or back movement has the thrust applied to an orbiting craft is (as in gyroscopes) ninety degrees displaced from the desired movement. As I‘ve said before; “shed loads of equal but not a gnats of opposite“.
In paragraph two I did explained that I was referring to an orbiting spacecraft and my question did involve gyro - dynamics, but on a giant scale. Put crudely - if, by throwing stuff out of your craft to the right, you shove your craft to the left does the orbital circle change (like a giant gyroscope would) as though an axis were at the point of shove or would it change (in a non gyroscopic, or Newtonian, way) as though the axis was ninety degrees round from the point of shove?
Strictly speaking, for the sake of accuracy (and understanding), in the example above the mass of the craft is constant and therefore the law referred to should be not be called the conservation of momentum law but “the conservation of speed law” (understood by Newton when he said that a body would remain in motion or at rest etc. etc. in his second law - the “momentum” bit seems to have crept in later). Thus a craft that has a force applied to reduce its orbital path will maintain its speed (velocity if you must) and, as its orbital path is made shorter, will increase its rpm. (rpd., more like) and move forward in relation to the space craft it is docking with.
If you head starts to bleed at this point don’t worry as I’m told this is normal (though that may only be “normal“ for nutters like me in sheds).
Incidentally Ram you have got the wrong end of the stick a bit about gravity. Gravity goes on and on and the effects of it are hardly diminished at all in earth orbit (follows the inverse square law I assume - most radiating things do) “weightlessness” is caused by the inward pull of gravity being exactly balanced by the centrifugal force (sorry you scientists) on the craft.
Kind regards
NM
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