Change of direction, in Space.

Replies

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  Anoop Mathew

  Shashank Moghe

  Did it ever occur to you, how difficult a change of direction could be, for a spacecraft? Before I actually knew how it was done, Newtonian Physics made my mind go crazy 😀 But then again, Newtonian Physics showed the way.

  How is it done exactly? Does energy play any role in Vacuum (aka Space)?
  
  I think that short bursts of force from the engine of the spacecraft can change the direction of the craft. There should be like minimum of two engines, one on either sides of the spacecraft; and one would be OFF while the other is ON based on which direction you want to go. (Sort of like the propelling bottles found in that Android game called Bad Piggies)
  
  #untechnical.answer
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  Shashank Moghe

  Anoop Mathew

  Does energy play any role in Vacuum (aka Space)?

  Well, Energy always plays a role (energy is all there is, after all) and vacuum is not the same as space. Space is not vacuum (comes close, but still not entirely vacuum).
  
  Well, thrusts of energy part is correct. But, as per your two-engines solution, why should the spacecraft change its direction? On earth, we go upwards because we have the surface to push against. What is there to push against in space?
  
  Think 😀
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  Anoop Mathew

  Shashank Moghe

  Well, Energy always plays a role (energy is all there is, after all) and vacuum is not the same as space. Space is not vacuum (comes close, but still not entirely vacuum).
  
  Well, thrusts of energy part is correct. But, as per your two-engines solution, why should the spacecraft change its direction? On earth, we go upwards because we have the surface to push against. What is there to push against in space?
  
  Think 😀

  In space things get weightless. And you don't stay stationary in space either. So I figured that a little thrust can keep a freely moving object to keep moving. The two engines can act based on the design of the craft.
  
  eg: Moving football kicked from one end and again from the other will change directions. Now think of this football as your spacecraft and if the football had it's own means (aka engines) to move/rotate left or right.
  
  There may be more engines in the spacecraft, I'm not sure. I think even a single engine which is rotatable upto about 120 degrees (or more) can propel the craft in various angles around space. eg: Like the spotlights used at events.
  
  Or maybe there's something in the wings that adjust the weights on the craft to sort of move it. 😨
  
  Disclaimer: These comments are purely based on thinking not googling. So don't expect to find sense in everything I say.
  
  #-Link-Snipped-# : What do you think Sir?
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  Shashank Moghe

  Oh don't be worried. You are doing a great job at thinking your way out of this. I am just facilitating your thought process. What I am saying is, why should something change direction if there is nothing to push against?
  
  I did not understand your football analogy. Please explain if you can, in more detail.
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  Anoop Mathew

  Shashank Moghe

  Oh don't be worried. You are doing a great job at thinking your way out of this. I am just facilitating your thought process. What I am saying is, why should something change direction if there is nothing to push against?

  Every action has an equal and opposite reaction. Maybe it's this reaction that you want to get based on the action you just performed i.e. thrust.
  
  

  I did not understand your football analogy. Please explain if you can, in more detail.

  My Theory: Your football is rolling on the field at a slow pace, kind of like how a spacecraft would 'move' in the vast 'near-like-vacuum' nature of space as you've mentioned. A small kick on one side can move the ball. This kick could be from the force exerted by your leg. Now, if your ball had some engines to create thrust, it can move. But again, there is a field (aka surface) for the thrust to hit at.
  
  In space, i feel there is some kind of gas which can give this thrust. Or it may be purely a case in which the thrust exerted creates an opposite reaction that just pushes the body.
  
  Another analogy: What if the entire universe has an energy that is kind of like magnetically positive, and the thrust you gave was magnetically negative?
  
  #drowning.in.thought!
• 

  Shashank Moghe

  Anoop Mathew

  the thrust exerted creates an opposite reaction that just pushes the body

  This is correct.
  
  Your leg is an external force. On the spacecraft, there cannot be any external force (unless you are relying for a space body to hit you for a change of direction. Possible, but unprobable.) You must rely on the internal components (for action and reaction, as you rightly mentioned) for the change of direction. Now this can be achieved in various ways. A thrust (a small impactful thrust) which pushes against some other free-to-move body (inside the spacecraft) will change your direction. Why does it have to be free to move, and not attached to the rest of the body of the spacecraft, is another question for you (it has been a personal deduction for me, earlier) 😀
  
  I have also learnt about gyroscopes being fit (in the Hubble space telescope), which help change the direction in which the viewfinder is pointing at.
  
  Exciting things to learn 😀 Space science is fun.
• 

  Anoop Mathew

  Shashank Moghe

  This is correct.
  
  Your leg is an external force. On the spacecraft, there cannot be any external force (unless you are relying for a space body to hit you for a change of direction. Possible, but unprobable.) You must rely on the internal components (for action and reaction, as you rightly mentioned) for the change of direction. Now this can be achieved in various ways. A thrust (a small impactful thrust) which pushes against some other free-to-move body (inside the spacecraft) will change your direction. Why does it have to be free to move, and not attached to the rest of the body of the spacecraft, is another question for you (it has been a personal deduction for me, earlier) 😀
  
  I have also learnt about gyroscopes being fit (in the Hubble space telescope), which help change the direction in which the viewfinder is pointing at.
  
  Exciting things to learn 😀 Space science is fun.

  I've answered based on Space Movies seen over the years.
  
  

  Why does it have to be free to move, and not attached to the rest of the body of the spacecraft, is another question for you (it has been a personal deduction for me, earlier) 😀

  Because if it's attached then it would carry the same charge as the spacecraft. If it's free, it'd be neutral to any force/charge that's part of the spacecraft. But it'd be interesting to know how they keep a separate free-to-move body inside the spacecraft without making it touch the body of the spacecraft. Will that be stored in vacuum inside the spacecraft? I bet it is.
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  Shashank Moghe

  Well, I am not sure if there is a mechanism like that, it is just my hypothesis. There could be similar systems though, for instance imagine a part of the spacecraft detached from it (thrown away forever). The Gyroscope solution sounded very neat to me though 😀
  
  So many things that skip our attention, but are actually engineering nightmares for the people involved.
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  Anoop Mathew

  Shashank Moghe

  imagine a part of the spacecraft detached from it (thrown away forever)

  Rockets used to launch the spacecraft are detached once they leave Earth's atmosphere. The initial thrust to start the space craft engine could begin likewise if it was the case as you said in your analogy. But that could pretty much leave the spacecraft in one direction (unless some other medium hits/opposes it in order to change its direction).
  
  But moving around and changing directions multiple times would not be possible I guess without some other ingenious solution (like the free-to-move object inside the craft or attached somewhere to the craft.). You also don't want to be throwing stuff in space each time you visit.
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  Shashank Moghe

  Which is why I believe Gyroscopes are a better solution. Now, we can start googling. We have attained an understanding of things that can and cannot work. And also, why they can and cannot work. Do share any interesting results you find here. I will do the same.
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  Ramani Aswath

  All that a gyroscope does is to to retain its axis of rotation invariant in space. If an attempt is made to change this direction the gyro applies a torque perpendicular to the torque applied. All that one can achieve by that is to change the direction the space craft is pointed at. It will still move in the same trajectory.
  
  One has to use a rocket engine (and Newton's Third law of motion) to change the direction of motion. A space craft in free fall is stationary as for as the craft is concerned. Peripheral rockets (can be just gas jets) can be used to orient the craft to face the intended direction. Rear rockets are fired to impart forward movement.
  Orbital Maneuver
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  durga ch

  like this :
  #-Link-Snipped-#
  
  ???
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  Shashank Moghe

  A.V.Ramani

  All that a gyroscope does is to to retain its axis of rotation invariant in space. If an aatempt is made to change this direction the gyro applies a torque perpendicular to the torque applied. All that one can achieve by that is to change the direction the space craft is ppointed at. It will still move in the same trajectory.
  
  One has to use a rocket engine (and Newton's Third law of motion) to change the direction of motion. A space craft in free fall is stationary as for as the craft is concerned. Peripheral rockets (can be just gas jets) can be used to orient the craft to face the intended direction. Rear rockets are fired to impart forward movement.
  Orbital Maneuver

  Very right. Thank you. I should have said this, but did not. I would be frank in accepting that I made a mistake. #-Link-Snipped-# take note of what #-Link-Snipped-# sir said. This is a better (more complete) solution to the problem we were discussing.
• 

  Ramani Aswath

  Shashank Moghe

  I have also learnt about gyroscopes being fit (in the Hubble space telescope), which help change the direction in which the viewfinder is pointing at.
  
  Exciting things to learn 😀 Space science is fun.

  While working at Trivandrum I had interacted a lot with the division of VSSC that used to make vacuum sealed gyros. These use Beryllium (a very toxic metal) for the rotor. I produced a document on the handling of this metal. Out of personal interest I also spent time in the division studying what they did. These gyros are used for navigation. since magnetic compasses are useless in space.
  I have been interested in gyros since child hood. We had a few we used to play with.
  I now have a Levitron, a pure physics toy my son sent from the US.
  
  #-Link-Snipped-#
• 

  Shashank Moghe

  A.V.Ramani

  While working at Trivandrum I had interacted a lot with the division of VSSC that used to make vacuum sealed gyros. These use Beryllium (a very toxic metal) for the rotor. I produced a document on the handling of this metal. Out of personal interest I also spent time in the division studying what they did. These gyros are used for navigation. since magnetic compasses are useless in space.
  I have been interested in gyros since child hood. We had a few we used to play with.
  I now have a Levitron, a pure physics toy my son sent from the US.
  
  #-Link-Snipped-#

  Sir, any reasons that you can disclose why they use Beryllium?
  
  Besides, gyros are amongst the innumerable "mysteries" of the physics world, I am fascinated by them as well 😀
• 

  Ramani Aswath

  Exceptional stiffness, stability, corrosion resistance, high temperature performance, and a low TEC make it very suitable for high spin (>100,000RPM) gyro rotors.
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  Garvit Garg

  using gyroscope principle to change direction in space...as in having two sets of perpendicular heavy wheels(to create good momentum) attached with motor and space craft will be changing accordingly to maintain angular momentum...??? if this is your idea than salute...awesome thought....
• 

  Ramani Aswath

  A gyro can only apply a torque and that too only if its axis of rotation is attempted to be altered. If there are a pair of them each with a different orientation one ends up with two torques in different directions with a resultant new torque.
  
  All that one can do using a gyro is to change the direction of orientation of the space craft. It will still be moving at its original velocity in the original direction. In the case of the Hubble telescope that is exactly what is wanted. Make the telescope look at different celestial objects and remain locked to the selected object for a leisurely examination or photography.
  
  The other issue is that a gyro with enough angular momentum to be able to turn a space craft with a large inertia will be quite heavy and difficult to send up in the first place.
  
  To get the space craft to move in a different direction still requires an impulse engine like a rocket or jet.
  
  What is a Gyroscope and How Does it Work? - Science Video
  
  
• 

  Shashank Moghe

  Garvit Garg

  using gyroscope principle to change direction in space...as in having two sets of perpendicular heavy wheels(to create good momentum) attached with motor and space craft will be changing accordingly to maintain angular momentum...??? if this is your idea than salute...awesome thought....

  #-Link-Snipped-# This idea for change of direction (as #-Link-Snipped-# sir pointed out in detail in the post following you) has been in practice for the Hubble for a long time. Salute to NASA and other space agencies for using such an enigmatic yet resourceful application called the Gyroscope. #-Link-Snipped-# Sir said this was also employed by our very own Vikram Sarabhai Space Center.