Is this statement correct?

Question

"2 magnets of equal size repulse one another at a constant velocity that is relative to their mass. Remember, the force of gravity is very weak, and in fact, magnets of any size are capable of exceeding it temporally."


This person is claiming that half mile long magnets will push a vehicle into orbit.

??

Answer 1

The statement "repulse one another at constant velocity that is relative to their mass" is not correct. It does not make logical sense from a physics standpoint. However, magnets are capable of overpowering gravity, and not just temporarily.

Magnets exert forces on each other. A force is simply a push or a pull. When a force is exerted on an object, it will accelerate in the direction the force was applied.

The trouble with using magnets to get into space is that if the magnets attract you while you approach the magnet, it will also attract you once you've passed the magnet (which will slow you down again by exerting a backwards force on you).

What is needed is a way to turn the magnets off as you pass them. The solution is the electromagnet, a coil of wire. When you run electric current through it, it becomes a magnet. Turn off the electricity, it's not a magnet anymore. So, you can activate and deactivate the electromagnets in sequence to propel an object. The name for this device is a "Gauss gun", and it's a real device.

Gauss guns work well enough on a small scale, but friction and electrical issues make it fairly impractical on a large scale. Nobody has ever succeeded in making one large enough to, say, launch a space ship into orbit.

Answer 2

There are good answers here. I just thought to add that no matter what the launch method is, there is a certain amount of energy represented in an orbiting body that MUST be put there, or else it won't orbit the Earth. Some methods just waste a lot of extra energy in various forms....

Take the space shuttle at an altitude to rendezvous with the ISS:

mass = 2,029,203kg + 24,400kg (max payload)
mass = 2,053,603kg
V = 27,743.8Km/hr = 7706.6 meters / second
G = 9.8m/s^2
H = 333km = 333000m

Ek = 1/2 mv^2 = 60983645614803
Ep = mgh = 6701728030200
E = Ek + Ep (excluding the energy stored in the mass itself)
E = 67,685,373,645,003 joules
E = 67.6 million megajoules!
This would be 18 megawatt hours!

To put that in perspective, the total US electrical power production in April 07 was 303,300,000 megawatt hours. Assuming equal production for 30 days, this would be 10.11 million megawatt hours produced each day.

So in just about 9 minutes, the space shuttle is given energy equivalent to a noticeable portion of the entire national daily electrical output just to get it into orbit. This excludes waste in the form of mechanical inefficiency, aerodynamic drag, course corrections once in orbit, etc. Just the bare minimum to be at the same orbital charicteristics as the ISS!

Oh yeah - then they burn it all back off by aerobraking upon reentry. ;)

Again, this is just the amount of energy left over in the orbiter and its cargo after launch. The shuttle actually expends a LOT more energy than this during a launch.

Imagine how much electricity it would take to fire off electromagnets capable of transferring this much energy into a craft, and in only 1/2 a mile? That would be more G forces than a human could survive!

Answer 3

The statement repulse at a constant velocity is not correct. Repulse would imply a net force acting on an object. If there is a net force, the object must have an acceleration, and thus cannot move at a constant velocity.

Answer 4

you lost me at "velocity that is relative to their mass."