MadSci Network: Physics

Re: is it possible to create a magnetic rocket

Date: Fri Oct 20 08:04:33 2000
Posted By: Kenneth Chivers, Grad student, B.S. Aerospace Engineering, In school for MBA:Management of Information Systems, NAWCAD, Lakehurst, NJ
Area of science: Physics
ID: 971308511.Ph

Peter, yes it is possible!  However, I'm not sure if the method you 
prescribe is practical with today's technology.  

Theoretically, when you pass current through a coil, an electromagnetic 
force is generated in a direction normal to the current.  An easy way to 
envision this, without getting bogged down into vector geometry, etc., is 
to use your hand to illustrate.  First, take your right hand, and make it 
flat on a surface like a table at home.  Next, extend your thumb straight 
out away from your hand, like a "thumbs up".  Keep your fingers together 
and flat, with the palm against the table.  Now imagine 3 axis, x, y and 

The z axis extends up from your wrist, towards the ceiling.  For this 
situation, as different situations may use a different illustration, 
rotate your hand flat against the table to angle your thumb in the 
direction you wish to apply your force.  If you want to move away from 
that direction-push off-simply curl your fingers around the imaginary bar 
running under your thoumb and across your palm.  This is what a positive 
or counter-clockwise current will do.  If you wanted to move in the 
direction of your thumb, simply flip your hand over-rather than breaking 
your fingers to get them to curl the opposite way-and curl them as 
before.  This is a negative or clockwise current.  Noticee your thumb is 
pointing the opposite way, unless you've broken your fingers :)

The thumb represents the resultant force, normal to the current.  

That being said, the hard part comes in the nature of the force.  Unlike a 
rocket or turbine, which react directly with the simpler physical aspects 
of their environment, an electro-magnetic engine or thrust generator 
requires a similar field to interact with.  In other words, in order for 
the rocket idea to work, you would need a nother field, generating a force 
normal to the rocket's field.  

Now, you've opened a whole new can of worms :)

Most important in this situation, is your thrust.  The thrust in 
this case results from the repulsion strength between the two fields.  The 
closer the two fields are to being exact opposites, the more resultant 
thrust will effect the mass of the rocket; make it move faster.  An 
electro-magnetic field's strength or force is reduced by a factor of 1 
over the square of the increasing distance.  This affects both the design 
of the rocket and the design of the launching platform as well.  

Simply put, as the distance increases between the rocket and the launching 
platform's field generator the velocity of the rocket will drop off 
dramatically in proportion to the square of the distance between the 
rocket and the field.  

Let's say you were moving at speed x at "lift off".  At distance z, the 
rocket is now only moving at x/(z^2)-SIGNIFICANTLY SLOWER!!!  

To combat this effect, either the rocket and/or the launch platform 
generator would have to significantly ramp up the strength of their 
fields, consuming much much larger ammounts of energy.  

Therefore, although your model is possible, with today's technology and 
energy generation capabilities, your model is not practical.  However, 
more simple kinetics, like firing bullets, etc...a simple modification to 
your model for "short range" use could prove to be worth looking into.  
Militaries around the world are spending more and more money into this who day...when we've discovered fusion...

Thanks for your question, I hope this hasn't dampened your thoughts, but 
given you some helpful information.


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