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# Re: A new way of DEcelerating

```>Are their any numbers on how much power per thrust the magnetic break would
>take?

I'm not certain if you understood the mechanism. It seems that I didn't either:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Now looking at the formulas again, I notice that the plasma needs to move
traverse to the flightpath and my assumption of towing the wires behind the
ship is probably not right either. They need to be in a network in front of
the ship (the plane of the net is perpendicular to the direction of movement.)

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

The interstallar plasma is moving, don't ask me why or whereto but the book
says it does. What we do is use the magnetic field component that is
traverse to the velocity of the ship.

/\
||
---------------- moving conducting wire

X O X O X O X O  magnetic field lines going up or down or aside

If the field lines are perpendicular to the direction the wires are moving,
then an electric current will start to flow in these wires. The electric
resistance turns this current into heat and radiates it away in all
directions. All that heat comes from the kinetic energy of the starship and
thus the ship slows down.

They use the following formula:

Drag force= rho V Va A

rho=mass density of the plasma
V=ships velocity
Va="Alfven" velocity=Sqrt[B^2/(4 Pi rho)]=10 km/sec
B=traverse magnetic field
A=frontal area of the net

They use also another way of writing:

Drag force = Sqrt(Dh Dm)

Dh=hydronamic drag= rho V^2 A       (Dh=normal drag due to mass-collisions)
Dm=magnetic drag = A B^2/(4 Pi)

This system looks a lot like the solid plate in front of the ship catching
the ISM to decelerate. The book tries to explain that this magnetic sister
may be more usefull due to the size:mass ratio. While one can use thin wires
to make use of the magnetic field, one needs a rather thick plane to stop
fast moving particles.

By the way, Steve, would it be possible for you to explain how a normal
magnetic scoop could be constructed.

Timothy

```