'Impossible' rocket drive works and could get to Moon in four hours

[tinman]

I wasn't referring to conservation of momentum.  The boat example is in reference to phase displacement and motion without inertia or resistance.  In other words, there is no external or outside force acting on the boat to give it a net motion.

Gravock

Rock-et motor
The ejection of mass-nothing more,nothing less.

[gravityblock]

Rock-et motor
The ejection of mass-nothing more,nothing less.

Wrong!  A rocket doesn't eject mass in opposite directions to achieve motion as is being done with throwing rocks from a boat in opposite directions.  Ejecting mass in opposite directions from a rocket simultaneously or throwing rocks of equal mass from a boat simultaneously in opposite directions doesn't induce a net motion (the forces are cancelled).  However, throwing rocks of equal mass in opposite directions at different times does induce a net motion through phase displacement, which is motion without inertia or resistance.

Gravock

[MarkE]

Wrong!  A rocket doesn't eject mass in opposite directions to achieve motion as is being done with throwing rocks from a boat in opposite directions.  Ejecting mass in opposite directions from a rocket simultaneously or throwing rocks of equal mass from a boat simultaneously in opposite directions doesn't induce a net motion (the forces are cancelled).  However, throwing rocks of equal mass in opposite directions at different times does induce a net motion through phase displacement, which is motion without inertia or resistance.

Gravock

Rockets operate on the basis of Newton's Third Law:  They eject propellant in one direction creating a reaction force that accelerates the rocket in the opposite direction.

[gravityblock]

Rockets operate on the basis of Newton's Third Law:  They eject propellant in one direction creating a reaction force that accelerates the rocket in the opposite direction.

ROFLMAO.  Yes, and this is the reason why a rocket isn't the same as throwing rocks in opposite directions simultaneously from a boat in order to achieve motion.  According to Newton's Third Law, the forces should be cancelled when throwing rocks in opposite directions from a boat, but this isn't always the case as previously shown by the boat/rock example.


Gravock

[MarkE]

I wasn't referring to conservation of momentum.  The boat example is in reference to phase displacement and motion without inertia or resistance.  In other words, there is no resistance or external force acting on the boat to give it a net motion.

Gravock

The boat example does not negate inertia.  It demonstrates it.  Let us assume that the water is frictionless as was stated.  The boat accelerates in the opposite direction of each ejected mass.  When the first mass is ejected, the boat attains a velocity proportional to the ejected mass and inversely proportional to the remaining mass of the boat.  When the second mass is ejected, the boat velocity changes by an amount proportional to the speed of the second mass and inversely proportional to the newly reduced mass of the boat.  If the two ejected masses are equal and their velocities relative to the external frame of reference are equal and opposite then the boat comes to rest albeit at a position that has shifted from the starting point.  If an equal amount of energy is imparted to each mass as it is thrown, then the boat ends up moving at a low speed in the same direction as the first rock was thrown.  This is all because of Newton's three laws.