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MAGFORCE
INTRODUCTION
Magnetic forces have been invoked for maglev levitation of trains and for launching space
vehicles. In each case, the magnetic forces between the moving object and a rail are exerted
over a very short distance such as between the launch vehicle and rails. This section describes
two magnetic force effects that can lead to unique methods of reaching space. The first, is the
Magnetic force between two current loops that are close together. The second force is the
forces exerted by the magnetic field gradients of a stationary current loop with a moveable
smaller current loop. These forces can lead to novel space related applications.
MAGNETIC FORCE BETWEEN TWO CURRENT LOOPS
The fall off with distance to the fourth power only applies when the current loops are separated
by a large distance. When the current loops are within about one loop radius of each other, the
forces are considerable. This web page presents the basic equations and examples of forces
between two current loops. These equations will be invoked in the web pages regarding space
cities. The forces between two realizable current loops, with one located at 150 KM is a net one
billion pounds. This is usable weight and can be translated into space facilities, such as launch
equipment to achieve orbital or escape velocities.
MAGNETIC FORCE BETWEEN CURRENT LOOP AND MAGNETIC
FIELD GRADIENT
A magnetic field gradient is a method of describing the change in magnetic field strength as you
move closer to or farther away from a magnet. For example, as you come close to a magnet
with a metal object, such as a screw driver, you begin to feel a force, then suddenly, the object
is snapped into the magnet. Such forces are described below, and are utilized in the heavy lift.
Concept.
Magnetic forces have been invoked for maglev levitation of trains and for launching space
vehicles. In each case, the magnetic forces between the moving object and a rail are exerted
over a very short distance such as between the launch vehicle and rails. This section describes
two magnetic force effects that can lead to unique methods of reaching space. The first, is the
Magnetic force between two current loops that are close together. The second force is the
forces exerted by the magnetic field gradients of a stationary current loop with a moveable
smaller current loop. These forces can lead to novel space related applications.
MAGNETIC FORCE BETWEEN TWO CURRENT LOOPS
The fall off with distance to the fourth power only applies when the current loops are separated
by a large distance. When the current loops are within about one loop radius of each other, the
forces are considerable. This web page presents the basic equations and examples of forces
between two current loops. These equations will be invoked in the web pages regarding space
cities. The forces between two realizable current loops, with one located at 150 KM is a net one
billion pounds. This is usable weight and can be translated into space facilities, such as launch
equipment to achieve orbital or escape velocities.
MAGNETIC FORCE BETWEEN CURRENT LOOP AND MAGNETIC
FIELD GRADIENT
A magnetic field gradient is a method of describing the change in magnetic field strength as you
move closer to or farther away from a magnet. For example, as you come close to a magnet
with a metal object, such as a screw driver, you begin to feel a force, then suddenly, the object
is snapped into the magnet. Such forces are described below, and are utilized in the heavy lift.
Concept.
MAGNETIC FORCE BETWEEN TWO
CURRENT LOOPS
The force between two current loops is calculated
using the equation below. The geometry and
definition of terms is shown in the figure on the right.
The equation is from Portis, A." Electromagnetic
Fields, Sources and Media", John Wiley and Sons,
1968. The equation has been programmed in
MathCad and those calculations are used in the
Space Cities page and in the Heavylift page of the
web site.
CURRENT LOOPS
The force between two current loops is calculated
using the equation below. The geometry and
definition of terms is shown in the figure on the right.
The equation is from Portis, A." Electromagnetic
Fields, Sources and Media", John Wiley and Sons,
1968. The equation has been programmed in
MathCad and those calculations are used in the
Space Cities page and in the Heavylift page of the
web site.
FORCES ON A CURRENT LOOP IN A MAGNETIC FIELD GRADIENT
Magnetic field lines are created in predictable directions around a current loop as shown
below. The gradients of these field lines cause forces on a smaller current loop placed within
the fields. This force is a function of the gradients of the magnetic field. The details are shown
below in a series of figures.
Magnetic field lines are created in predictable directions around a current loop as shown
below. The gradients of these field lines cause forces on a smaller current loop placed within
the fields. This force is a function of the gradients of the magnetic field. The details are shown
below in a series of figures.
THE FORCE EQUATIONS FOR A SMALL CURRENT LOOP ABOVE A
LARGE CURRENT LOOP
When a small current loop is located within the magnetic field gradients of a large current loop, a
force is exerted on the loop as a function of the gradients (rate of change) of the magnetic fields
in different directions. An analytic expression for those forces in terms of the gradients is
presented below:
LARGE CURRENT LOOP
When a small current loop is located within the magnetic field gradients of a large current loop, a
force is exerted on the loop as a function of the gradients (rate of change) of the magnetic fields
in different directions. An analytic expression for those forces in terms of the gradients is
presented below:
OBSERVATIONS
1. The forces between two current loops scale as the area of the loops. It is that scaling that allows the
extremely large net forces to be exerted on the loops, making a space city technically possible. This is
discussed in more detail on the SPACECITY page.
2. The forces on a small current loop in the magnetic fields of a large current loop are the basis for HEAVYLIFT
of freighter like spacecraft that would ferry materials and people from the earth's surface, to the space city port.
3. Orbital and interplanetary vehicles would take off from the space city via a number of means. Conventional
chemical rockets could be used. Alternatively, rotating outer rings could sling the vehicles on to the planets or
the stars.
1. The forces between two current loops scale as the area of the loops. It is that scaling that allows the
extremely large net forces to be exerted on the loops, making a space city technically possible. This is
discussed in more detail on the SPACECITY page.
2. The forces on a small current loop in the magnetic fields of a large current loop are the basis for HEAVYLIFT
of freighter like spacecraft that would ferry materials and people from the earth's surface, to the space city port.
3. Orbital and interplanetary vehicles would take off from the space city via a number of means. Conventional
chemical rockets could be used. Alternatively, rotating outer rings could sling the vehicles on to the planets or
the stars.