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Author Topic: Could magnets be used to propel spacecraft?  (Read 1520 times)

Offline Josh Carne

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Could magnets be used to propel spacecraft?
« on: 03/11/2015 02:26:39 »
 I recently read that a object attracted by a magnet has the ability to reach light speed. This is providing that you have a gigantic and powerful magnet that is focusing all it's power on something far enough away to gain that speed and i'm sure there's a bunch of other stuff involved. However just based on the concept of that powerful attraction.....

 If a series of electromagnetic producing stations are placed around our planet and then a spaceship is sent close  enough to get a slight increase in speed from each of them, could the spaceship eventually reach incredible speeds that we could then release towards a desired destination?
« Last Edit: 03/11/2015 09:33:16 by chris »


 

Offline alancalverd

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Re: Spaceship or projectile propulsion question
« Reply #1 on: 03/11/2015 08:05:14 »
Magnetic acceleration has been proposed many times, and small "railguns" have been demonstrated. The underlying problem is how to rotate the projectile from horizontal motion along the earth's surface into vertical motion to leave the planet. Alas, it is generally easier to fire a rocket directly upwards.

 

Offline evan_au

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Re: Spaceship or projectile propulsion question
« Reply #2 on: 03/11/2015 09:14:45 »
Quote from: Josh Carne
I recently read that a object attracted by a magnet has the ability to reach light speed.

Not quite so.

The Large Hadron Collider has just such a ring of powerful magnets, which consume huge amounts of electricity (about a quarter of a nuclear power plant).

But the objects it accelerates are bunches of protons or lead nuclei, rather than spacecraft.

And it can't reach lightspeed - relativity says that objects effectively increase in mass as they approach the speed of light. The 7 TeV LHC can only accelerate protons until their mass is 7460 times normal.

From the Lorentz factor (1-v2/c2)-1/2, you can work out that the LHC accelerates protons to 99.9999991% of the speed of light.

And the new, upgraded 14TeV LHC will be able to go slightly faster. But it cannot ever reach the speed of light just by pouring in more energy, or by building a ring of larger diameter.

See: http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/lhc-machine-outreach-faq.htm
 

Offline chris

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Re: Could magnets be used to propel spacecraft?
« Reply #3 on: 03/11/2015 09:35:32 »
the objects it accelerates are bunches of protons

Given that a charge is being accelerated in order to turn the bends in the accelerator, is the circulating proton beam shedding radiation on its journey around the ring, in the same way that an X-ray beam issues from a  synchrotron?
 

Offline evan_au

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Re: Could magnets be used to propel spacecraft?
« Reply #4 on: 03/11/2015 10:35:57 »
Quote from: Chris
is the circulating proton beam shedding radiation on its journey around the ring?
Yes, this is one of the major energy losses from the LHC.

You can reduce this radiation loss by making the ring a larger diameter; there are proposals to add a 100km ring at CERN, but it's unclear whether CERN's funding partners would pay for this.
The diameter of the Earth would be an extreme example of this, with equally extreme funding problems...

Quote
a charge is being accelerated
A spacecraft could not be accelerated by magnets in quite the same manner as the LHC accelerates protons, as it would involve ripping all the electrons off all the atoms in the spacecraft. This would fry any electronics, and tear the whole spacecraft apart.
 

Offline jeffreyH

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Re: Could magnets be used to propel spacecraft?
« Reply #5 on: 03/11/2015 21:56:44 »
You would need to generate a repulsive force rather than an attractive force. So instead of a magnetic component you would need a negative mass component. That is so hypothetical that it is Hollywood physics.
 

Offline jeffreyH

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Re: Could magnets be used to propel spacecraft?
« Reply #6 on: 03/11/2015 22:00:57 »
P. S. Look up Alcubierre drive.
 

Online chiralSPO

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Re: Could magnets be used to propel spacecraft?
« Reply #7 on: 03/11/2015 23:07:41 »
Well, you can use magnets to propel spacecraft, but it is a little more complicated. Check out the related articles in wikipedia here: https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion#Electromagnetic

Essentially, one can use a particle accelerator to shoot ions out the back of a spaceship at extreme velocities (the greater the velocity of the ejected particles, the greater the specific impulse of the thruster)
 

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Re: Could magnets be used to propel spacecraft?
« Reply #7 on: 03/11/2015 23:07:41 »

 

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