Hello all. Thanks Tok-Tokkie.
What really matters is the engines and the control of the flight.
PORTABLE FLYER CONTROL
To analyze the exact motion and the response of the pilot is difficult, if not impossible.
When a problem is difficult, the reductionism is the way to go.
1. The astronaut.
The case with the astronaut who “flies” in empty space (out of the air), outside or inside a gravitational field, shows that the “Weight Displacement Control” provides full control
The propulsion unit provides a pure thrust force and is secured to astronaut’s body.
The pilot displaces the overall center of gravity relative to the thrust force axis by varying their body posture.
The offset thrust force – relative to the center of gravity – turns the assembly and redirects / re-vectors the thrust force.
The astronaut can turn at any desirable direction and can go from any point A to any point B avoiding any obstacles between these points, following any path they like.
The astronaut can also take off and land.
2. The wind dancer.
- The photo shows just an astronaut, not the astronaut we talk about.
Without air to interact, the astronaut has no aerodynamic control, at all.
The thrust axis is what matters, not the exact point where the propulsion unit is located; for instance, if the “thrust provider” has zero weight, then either the thrust provider is above the head of the astronaut, or below their feet, or around their waist, it is exactly the same.
And talking for center of gravity: the Portable Flyer is to be driven by thin persons, by women, by gymnasts, by fat persons, by anyone; to provide / define the exact weight and the exact location of the center of gravity is meaningless, especially considering that the center of gravity is displaceable (for the “weight displacement control”) and that the overall weight decreases as the fuel is consumed.
In the case with the “wind dancer” (video) the “Weight Displacement Control” is not applicable.
Because the thrust force (i.e. the weight of the “wind dancer”) permanently passes through the center of gravity of the “wind dancer” (this is the definition of the center of gravity in physics).
With zero offset of the thrust force (i.e. of her weight) from her center of gravity, there is no torque to turn / to re-vector the “wind dancer”.
But the “wind dancer” is in a high speed air stream (say, 150mph) and her body can interact with the air creating forces and torques that turn and displace her.
She has full control over her flight: she can turn at any direction (pitch, yaw, roll) in a fraction of a second, she can also move at any direction (upwards, downwards, to the left, to the right, forwards, backwards).
3. The Portable Flyer
With its "true neutral propulsion unit" (neither vibrations, nor reaction torque, nor gyroscopic rigidity; only a force that can "instantly" and effortlessly be vectored towards the desirable direction) the pilot has full control over their flight by combining both:
the “Weight Displacement Control” (of the astronaut) and the “Aerodynamic Control” (of the “wind dancer”).