# The Poynting Vector and Field Propulsion

## Poynting Vector

“However, the amplitude of the vector field increases at a greater rate than the two (electrical and magnetic) fields which generate it and, at high resonance levels, becomes very strong. The vector field, whose direction is perpendicular to each of the other two, creates an effect similar to, and in fact identical with a gravitational field.”

There is only one known vector force in physics which results from electrical and magnetic fields oscillating at right angles to one another and that is the Poynting vector. It is perpendicular to both the magnetic and electrical fields(see slide 11).

As we know, photons are merely magnetic and electrical fields of equal amplitude and equal phase, which oscillate perpendicularly to one another and the direction of propagation. When a photon is absorbed or reflected from matter, the Poynting vector conveys a small unit of momentum to the object, in the direction of propagation (at any angle smaller than 90 degrees with respect to the incident vector). In fact, whenever there’s a differential in the energy absorbed or reflected by matter along a given axis, a force of pressure is manifested.

The photon energy differential across a given surface area during a given interval, divided by C, is the magnitude of the Poynting vector force, and it’s called the ‘radiation pressure’.

This vector force possesses some interesting qualities which conform to Fry’s description above. Firstly, it is a very small force at mid-to-low range frequencies and amplitudes – for example, one can’t feel the radiation pressure of the photons from the Sun upon the skin, but it is physically present and calculable (it’s roughly 4.6 x 10-6 Pascals aka Newtons/m2). This is the pressure produced by the >1 kilowatt of photon energy which is incident per m2 per second, at the Earth’s surface.

Surprisingly, the magnitude of the Poynting vector increases at a rate proportional to the fourth power of the frequency . Clearly, at both high amplitude and high frequency levels, the radiation pressure of the Poynting vector becomes significant.

If the radiation pressure acting on two sides of a body along a given axis are of equal and opposite amplitude, the inertial mass of that object will be increased along that axis, just as a piston under pressure from opposite sides of an enclosing cylinder possesses an increased resistance to acceleration along its central axis. Conversely, a differential in the radiation pressure across a material object will result in a net force of acceleration. This behavior appears to confirm Fry’s following statement:

“If the center of the field coincides with the craft’s center of mass, the only effect will be to increase the inertia, or mass, of the craft. If the center of mass does not coincide with the center of force, the craft will tend to accelerate toward that center. Since the system which creates the field is a part of the ship, it will, of course, move with the ship, and will continue constantly to generate a field whose center of attraction is just ahead of the ships center of mass, so that the ship will continue to accelerate as long as the field is generated.”

Up to this point, Daniel Fry’s description of the field propulsion mechanism of the cargo craft conforms to well-established physics, although the precise means by which a radiation pressure differential may be induced across the craft remains unclear.

1. "Electromagnetic Energy" (PDF), Physics 54, Duke University, page 5