Bill McMurtry wrote:
>
> Hi William,
>
> Don't you get it? How does a rocket in space accelerate? - it squirts
> MATTER in the opposite direction in which it wants to travel - right? The
> maximum velocity attainable by the rocket is determined by the maximum
> velocity of the matter it is squirting out.
Sorry Bill, close but wrong answer. Rocket velocity is determined by how
long it accelerates at a given rate. In newtonian terms, the rocket will
continue to accelerate indefinitely so long as a force is applied from
its motor.
In simplified terms the thrust force from the rocket motor will be
roughly: (the combustion chamber pressure x the area of the front of the
combustion chamber) x (the area of the nozzle / the area of the front of
the combustion chamber) - outside ambient pressure. The velocity of the
motor does not enter into the thrust formula. In other words, the
algebraic sum of all the forces in the motor equals a non-zero force
vector in the direction of thrust regardless of velocity of the motor.
Of course the pressure differential in the conventional rocket motor is
due to the acceleration of the mass of the combustion gasses so it is
practically limited and in practical terms the final result is similar
to what you said though and is expressed as the 'specific impulse' of
the motor. The momentum of the rocket's mass x its velocity = the
momentum of the exhaust gas x its velocity.
> Lets just say that the rocket is squirting mass out it's exhaust at 50,000
> miles per hour. How could the rocket ever attain a velocity greater than
> that of its own exhaust reaction mass? This rocket is incapable of a
> velocity greater than 50,000 miles per hour.
>
> Once again, using common Newtonion physics (every action has an equal and
> opposite reaction) all the fuel in all the worlds in all the galaxies in
> the whole (known) universe would not get you even close to light speed with
> a rocket. The answer to your question should be clear... Rocket + infinite
> amount of fuel = Velocity less than C.
Newtons third law which you quoted applies to forces. Velocity alone is
not force. You must consider the change in velocity or acceleration of
the ejected mass. Newtons second law can be expressed: f=ma
The acceleration of a rocket then will be: f/m=a or: thrust(in force
units)/ mass of rocket = acceleration. Acceleration is defined as the
'time rate of change of velocity' or (dV/dt). We could for example say:
Thrust = 100lbs, rocket mass = 1000lbs, duration = 100sec. Then by
substitution: change in rocket velocity will be: dV=(f/m)(dt) or
(100lbs/1000lbs)(32.2f/s/s)(100s)= 322f/s
Now applying newtons third law we can quickly answer the ultimate
velocity question. In a reaction motor the acceleration of the rocket
will always be proportional to the accelleration of the fuel mass and
will vary by the ratio of the masses. So the best case will be that the
rocket is 100% fuel mass. This means there is a 1 to 1 acceleration.
Using nuclear fuel, such that 100% of the fuel is converted to energy,
the entire mass being accelerated by the power of e=mc^2, you will have
zero mass left and it will be at the velocity of c.
So the long answer is NO you can't accelerate a rocket past light speed
using any KNOWN technology if the rocket must contain its own fuel and
work on the mass reaction principle. The problem boils down to the fact
that the more fuel you have, the more fuel mass that needs to be
accelerated. And none of this takes into account mass increase due to
relativity. What we need is over-unity power to get beyond this dillema.
> What you need is an inertial drive that does not rely on thrust from an
> expendable reaction mass. You should read Eric Laithwaite's paper on "Mass
> Transfer". Then again, maybe you should start with a good text book on
> basic physics and mechanics (seriously... I'm not having a go at you).
Such an inertial drive is considered to be impossible based on Newtons
third law.
> How can you disagree with Einstien, Newton, or any other fellow explorer if
> you don't understand their theories or 'proofs'? Answer me that!
>
> Bill.
Cheers,
Gerald O'