Explaining the Fluid Drive V3 with two astronauts and a steel ball
(previously three kids, an umbrella, a skateboard and batman)
Tongue in cheek
explanation of how the Fluid Drive proposal works using a spaceship, astronauts
and Batman (Adam West version)
In fig 1 we
have a spaceship in microgravity, inside are two astronauts (A and B) and a
steel ball.
Fig 1
Astronaut A
and astronaut B are at the forward and rear end of the spacecraft, if astronaut
B pushes the steel ball at astronaut A with force F1 (red arrow) he will
receive a counter force F2 (blue arrow) that will be transferred to the
spacecraft
Fig 2
As the
steel ball travels towards astronaut A with velocity V2 (fig 2) the spaceship
is traveling in the +X direction at velocity V1.
Fig 3
Collision.
The steel
ball collides with astronaut A (no doubt he feels the force that is transferred
to the spaceship) as their momentums are equal (momentum = velocity x mass) system
(spaceship and all inside) returns to original velocity 0.
Fig 4
If
astronaut A pushes the steel ball back at astronaut B (fig 4), when the ball
collides with astronaut B the result will be the same (the spaceships velocity
returns to 0), they can play all day but all the spaceship will do is wobble.
What happens if an air brake
is activates when the steel ball is traveling from B to A?
Fig 5
When
speeding towards astronaut A, the steel ball activates an air brake (fig 5)
that increases the steel ball’s drag reducing its velocity from V2 to V3i, the
spacecrafts V1 velocity is not affected (not very much).
Fig 6
Collision
When the
steel ball collides with astronaut A, the spaceship’s momentum P1 is almost
identical to instant illustrated in fig 3, but as the steel ball’s velocity has
decreased from V3i to V3f its
momentum p3 is less than momentum p1 and the force excreted by the steel ball
on astronaut A (and the spaceship) is not sufficient to return the spaceship’s
original velocity therefore it will gain velocity in the +X direction.
Astronaut A
can return the steel ball to astronaut B with a very slight push (it does not
matter that it takes longer to travel the length of the spaceship) so astronaut
B repeats this cycle and the spaceship will gain velocity with every cycle.
At this point I generally get the following comment:
This
will not work because all the impulse of the mass (steel ball), that you
"get rid of" by using airbrakes, is actually transferred to the air
inside the cylinder which pushes against the wall of the cylinder and
accelerates it. It is all a closed system, so there will be no change in
impulse and no acceleration at all.
This idea that the airbrake pushes against the AIR and the AIR pushes
against the rear wall of the cylinder is illustrated in fig 6a.
Fig 6a
But that is not really how drag works, the airbrake does not push
against an “AIR”, it pushes (collides) against individual fast moving gas
molecules (fig 6b 1), for every collision of molecule against air brake there
are two equal and opposite forces (no problem with Newton’s Laws), and the
molecules that have been hurled in the general direction of the rear wall of
the cylinder encounter billions and billions of fast moving molecules (fig 6b
2), as air has a tendency to expand in every direction to fill the container
(equalizing local differences in air pressure) some of the force is apparently
diverted towards the other walls of the container(1).
Fig 6b
There are also some that say when the airbrake collides with the air, the
air in front of the airbrake is compressed (fig26c 1) and that it will travel
to the rear wall of the cylinder like a Kamehameha (2). However as one of the
basic characteristic of a gas is its tendency to equalize its pressure when
contained (we do not see a tendency for higher pressures inside a container at
rest) part of the momentum will be diverted to the other walls of the cylinder.
Fig 26c
(1) Actually I do not really know with absolute
certainty how the air molecules behave for I cannot directly observe them (I do
not have a Schlieren set up available), I can expect air to behave in a certain
manner because of the kinetic theory of gases. But what I do know is what I can
observe, and the experiment described in http://www.wjetech.cl/e/
, and the experiment described in a DIY test (figs 13 to 21) work as described.
(2) Totally unnecessary dragon ball reference.
A step by
step explanation of the principles involved
The batman postulation
Chris from
Fig 9
I think
not, picture yourself as batman (Adam West incarnation) trapped in a box with a
wheeled cart speeding towards him.
If the
speeding cart is slowed and stopped by a propeller (fig 9 B) you (you’re batman
remember) WILL feel a strong breeze to say the least but if the speeding cart
is slowed and stopped by a parachute (like a drag racing car) you will not feel
the same “breeze”
A DIY test
This idea
can be tested (or disproved) with a very simple test setup.
Fig 13
We need a
box on a near frictionless surface, inside the box a test car and a mechanism
(in this example a compressed spring)
Fig 14
When the
spring is released the box (M1) will gain a velocity (V1) in the +X direction
and the car will gain a velocity (V2) in the –X direction. borrar
Fig 15
As they
travel in opposite directions their velocities (V1 and V2) remain approximately
constant.
Fig 16
Collision
When the
car collides with the box’s inner wall, it’s momentum (mass X velocity) will be
sufficient to stop the box that will return to its original velocity 0.
|
This test must be repeated various times If the box final velocity is different from 0 (however slightly) it means the test bed is flawed and the resulting velocity must be subtracted from any results obtained. |
Fig 17
We can now
repeat the experiment with an air brake attached to the test car.
Fig 18
When the
spring is released the box (M1) will gain a velocity (V1) in the +X direction
and the car will gain a velocity (V2) in the –X direction.
Fig 19
Fig 20
As the test
car moves in the –X direction (Figs 19and 20) the addition of the air brake
will (should) decreases it’s velocity (V2i > V2a > V2b > V2f)
Fig 21
Collision
When the
test car collides with the box, if the drag produced by the air brake on the
test car does not affect the box, then the test car’s momentum (V2f x cars mass)
will have decreased while the box’s momentum will have remained the same
therefore the box should have a noticeable +X final velocity
This has been a Tongue-in-cheek description of the idea, the serious
minded please see step by step
(no kids, no skateboard, no batman, no puns)
See
description of this effect for propulsion here.
Main Page, Other
versions, testing the principle,
testing version 2
(This document is a work in
progress)
If you wish to be informed of changes/updates on this
document please request with a mail to wjeconsultant@gmail.com