Why wouldn't this space propulsion work?

In summary, the conversation is discussing a proposed spacecraft design that violates conservation of momentum. The design involves using electromagnets to propel weights through a tube to create forward motion. However, it is pointed out that this design would not work because the forces are out of balance and it violates the principles of perpetual motion. The conversation is closed and the thread will not remain open for further discussion.
  • #1
Szkeptik
2
0
Hi!
I'm pretty sure someone would have already made this if it did work, but I don't know why it wouldn't. Can someone explain why this spacecraft couldn't move forward?
 

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  • #2
Can you explain why you think it would?

Hint:
How much work is done to get the ball to the far end of the tube?
How much work is done to bring it back to its starting point?
(Note, btw, that you have not actually completed a full cycle back to the starting state in your diagram.)
 
  • #3
DaveC426913 said:
Can you explain why you think it would?
Where are the forces out of balance?

There is acceleration when the weights are first repelled by the elecromagnet and the weights would not lose all their momentum before they reached the other electromagnet on the other end of the tube, meaning that less force would be burned in the other direction that the force that was created by the original "push".
 
  • #4
Szkeptik said:
There is acceleration when the weights are first repelled by the elecromagnet and the weights would not lose all their momentum before they reached the other electromagnet on the other end of the tube, meaning that less force would be burned in the other direction that the force that was created by the original "push".
The ball, by contacting the bend, will exert a rearward force. This makes up the "missing" force in your diagram.
 
  • #5
Note that your device is technically a perpetual motion device, which is a forbidden topic here on PF.
It's all right to ask why the design won't work (and there are several PPM principals that describe why), but be warned, this thread probably won't remain open long.
 
  • #6
Closed pending moderation.

This isn't technically a perpetual motion machine. As described it violates conservation of momentum rather than conservation of energy. However it is close enough that we need to moderate.

EDIT: the thread will remain closed. Dave has identified the reason that it won't work. Working out the details is a good exercise for personal study, but not a good topic for PF.
 
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FAQ: Why wouldn't this space propulsion work?

Why wouldn't this space propulsion work?

There could be several reasons why a space propulsion system may not work. Some common reasons include technical limitations, lack of funding or resources, and safety concerns.

What are the main limitations of space propulsion technology?

Some of the main limitations of space propulsion technology include the high cost of development and implementation, the need for advanced materials and engineering, and the difficulty of achieving the necessary speeds for interstellar travel.

Can't we just use traditional forms of propulsion for space travel?

Traditional forms of propulsion, such as chemical rockets, are limited in their ability to travel long distances in space. They also require a large amount of fuel, which adds weight and reduces efficiency. Newer forms of propulsion, such as ion engines and solar sails, are being developed to overcome these limitations.

Is it possible to travel faster than the speed of light with space propulsion?

According to our current understanding of physics, it is not possible to travel faster than the speed of light. Therefore, space propulsion systems are designed to achieve the highest speeds possible within the constraints of physics.

How can we address the environmental impact of space propulsion?

Space propulsion systems can have a significant environmental impact, especially in terms of space debris and pollution. To address this issue, scientists and engineers are working on developing more sustainable and eco-friendly propulsion technologies, such as using renewable energy sources and reducing waste and emissions.

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