Siri Cruz schreef op 28-10-2013 4:47:
> In article <l4ki0f$ltv$
1...@dont-email.me>, Warhol <
Mol...@hotmail.com> wrote:
>
>> Tom Wolfe's book "The Right Stuff" documents high altitude flight tests
>> with rocket powered aircraft that would invariably fail in the thin air
>
> They were aerodynamic flights which used shaped surfaces to generate lift.
> Ballistic flight does not use lift and does not stall.
>
>> Force = Mass x Velocity + (Pressure Difference between inside the rocket
>> and the vacuum of space) x Nozzle Area
>
> That dot over m means it's dm/dt. You don't know how to read Newton's derivative
> notation. Congratulations, dingbat.
>
> F = dp/dt Newton.
> = d(mv)/dt Definition of momentum.
> = m dv/dt + dm/dt v Product rule.
> = 0 m + dm/dt v Assuming constant velocity.
> = dm/dt v
>
> Which is half of the sum. The other part, F/A = P, is the definition of pressure.
>
>> NASA sites also say that Mass x Velocity = Momentum which is not a
>> force. Momentum is potential energy. If you throw a rock it has
>
> No, momentum is vector quantity that is conserved. Energy is a scalar; potential
> energy alone is not conserved. Momentum increases linearly with velocity;
> kinetic energy increases quadratically.
>
>> momentum. If you throw it harder it has more momentum. No force is
>> generated until the rock hits something. Gas shot out of the back of a
>> rocket very fast does not create a force until it interacts with
>
> Why do gasses shoot out without some force applied to them?
>
>> vacuum of space) x Nozzle Area violates the �free expansion� effect,
>> part of the first law of thermodynamics by which pressurized gas moves
>> into a vacuum without any work being done. It does not matter how highly
>
> The generalised gas law is PV = kT, so as the pressure decreases, the
> temperature decreases. Temperature is energy (=work) within the gas. So, yes,
> work is being done.
>
>> does not do any work, does not expend any energy and does not create any
>> force or thrust.
>
> It does expend energy as slower gas particles and photon emissions as the gas
> cools.
>
>> Force = Mass x Acceleration
>
> That's only true for constant mass. The actual law is F = dp/dt.
>
>> In 1852 scientist James Prescott Joule, for whom the unit of energy
>> Joule is named, discovered that gas does no work in a vacuum
>
> When you considerred the entire system, rocket, exhaust, and photons, energy and
> momentum are conserved. When you consider just components, such as just the
> rocket, energy and momentum are not conserved. The exhaust from an earth launch
> is expected, and desired, to fall back to the earth.
>
> And you're still an idiot.
>
Rather than pull the quotes from Wolfe's book which I read many years
ago here are the details of his crash in the NF-104A aircraft which
failed at an altitude of 21 miles.
http://www.check-six.com/Crash_Sites/NF-104A_crash_site.htm
Let me repeat... you are in the impossibility of movement in a vacuum.
thats what the law says...
Moving gas into a vacuum, such as from inside a rocket in space to
outside, is not a process that requires work. This is because free
expansion allows enters a vacuum "for free", no work is needed or done.
The gas does not push outward from inside the rocket and is not pulled
in by the vacuum of space. Natures seeks to being the two sides, high
pressure and zero pressure, into equilibrium and does so for "no
charge". Although this is a well-known result in Physical Chemistry and
Thermodynamics you almost never hear of it in the context of space
rocketry because it wreaks havoc on the NASA-led theories of thrust.
I have noted free expansion several times and produced various web sites
describing it. Do you not believe that it exists? It can be and has been
tested in vacuum chambers here on earth. I have yet to see a convincing
experiment describing how rockets produce thrust inside a vacuum
performed on earth. All the testing seems to be done up there in space.
Free Expansion
http://www.etomica.org/app/modules/sites/JouleThomson/Background2.html
http://demonstrations.wolfram.com/JouleExperimentOnFreeExpansion/
Also, just because a mass is moving does not mean it does any work. Mass
in motion has the property of momentum which is not the same as force.
In order for momentum to be turned into force it must interact with
something. A mass of gas moving at any speed through the infinite
vastness of space never encountering any other object, never speeding up
or slowing down does not exert any energy, does not do any work and thus
cannot be used to propel anything.
Converting Momentum into Force
http://www.physlink.com/education/askexperts/ae462.cfm
the "I throw something forward and thus I move backwards" example is one
that is often used to "explain" rocket thrust. It is a false analogy.
Gas isn't being thrown from the rocket. Gas isn't propelled into space.
Gas can only be propelled into an atmosphere where it encounters
resistance to its flow. If there is no resistance gas flows out into the
vacuum without being "thrown". This is the result known as free expansion.
For instance if you open a balloon at sea level the air seeps out
slowly, based on pressure difference. If you want to empty the balloon
faster you exert a force, press on the balloon and the air comes out
faster. If you try to same experiment inside a vacuum you cannot press
on the balloon to make the air come out faster, the air goes flying out
of the balloon without any force, because the nature of the vacuum has
already done all the work, for free, trying to equalize the pressure
inside the vacuum with that inside the balloon.
When high pressure gas enters a vacuum there is not even heat generated
from molecules bouncing off each other trying to leave the high pressure
area. The entire evacuation happens for free. No heat. No work. No muss.
No mess.
Part of the philosophy of science is determining what results are even
possible. For example, can you prove that all crows are black? In my
opinion it is a philosophical question to say that man does not create
new forces but only uncovers and harnesses existing ones. I could be
proven wrong when tomorrow someone invents some unheard of force. As per
my beliefs, if gas as it exists in nature cannot exert force upon
objects in while inside of a vacuum I cannot see how a rocket made to
operate in a vacuum, powered by gas, would work.
The idea that they can produce force outside of the atmosphere is a
fantasy/dream.
This feels a lot like trying to push the rocket from inside the rocket.
Lets say a pressure imbalance occurs against only one wall. There will
be a force generated but that energy goes into the hull of the ship
where is it turns into vibration, heat, etc... there is nowhere for the
energy of the hull to go because the ship is a closed system, insulated
by the vacuum of space.
There are "how does a rocket work" sites that realize this closed system
problem and use the nozzle / escaping gasses as a way to "open" the
system. However this is an error because free expansion means that no
work, energy or heat is transferred out via the escaping gasses and the
system remains closed just spread out over a larger distance. Think of
it like money. If I have $1 it doesn't matter if I break it into
nickels, dimes, pennies my net worth only changes when I spend it (or
earn more). So breaking my dollar has no affect my financial status.
Changing the energy of the ship from potential to kinetic won't move the
ship until that energy does work.
If the spaceship were a railway car on a track, as an open system
example, the force of a pressure imbalance would find its way to the
wheels which would start to turn, possibly the car would only rock back
and forth but at least it would move. As for a spaceship I don't believe
any motion would occur. There is no way for the ship to roll, slide,
rock, float (as on water), etc... the energy delivered to the hull
simply has nowhere to go hence no motion.
Closed systems
http://blowers.chee.arizona.edu/201project/EBclosedsys.pg1.HTML
This feels a lot like trying to push a car from inside the car.
of course you have pushed from within a car but that has nothing to do
with how rockets theoretically can move through space.
When you push from within a car some of the energy of the pushing goes
to the wheels which start to turn. A space ship is not analogous to a
wheeled vehicle. A spaceship does not move because of the physics of a
curved surface (wheel) interacting with a flat surface (ground).
These analogies of spaceships to cars, boats, etc... are all over the
Internet. I would say to you that attempts to connect motion in the
gravitational field and atmospheric conditions of earth to those in the
near-vacuum and near-zero gravity of space are tricks used to deceive
and mislead.
You have to go back to the basic physics of mass, velocity, momentum,
acceleration, force, energy and work and apply these to the space rocket
problem to see that the NASA and other apologists are faking all of the
science and fooling the public who seem pretty happy to be fooled by the
way.
Here is an article from the Journal of Physical Chemistry with
experimental results on Free Expansion
http://pubs.acs.org/doi/abs/10.1021/j150043a002?journalCode=jpchax.2
None of the analogies I have seen take into account that on earth
physics operates within a gravitational field and inside an atmosphere.
I consider "space" to be a near-vacuum with almost zero gravity. These
analogies always involve vehicles physically connected to and
interacting with the environment (planes->air, boats->water,
cars->ground, etc...) whereas a rocket in space is isolated. Forces are
not transferred between the vacuum and the ship in either direction. The
vacuum does not affect the ship nor the ship the vacuum.
Getting back to the original intention this thread....
It appears to me that NASA is using its reputation as the masters of all
that is science to pull the wool over the collective public eye,
misapplying physics, presenting fake formulas, much the same way they
present fake pictures, counting on apologists, shills and useful idiots
to discourage critical thinking (Newton's 3rd law, idiot!).
Earlier I proposed that the NASA equation for rocket propulsion is
invalid according to the laws of physics.
http://www.grc.nasa.gov/WWW/k-12/airplane/rockth.html
1. They use the formula "Force=MV" where "Force=MA" is the correct
version of Newton's 2nd law. "MV" = momentum which is not a force.
2. They incorrectly state that exhaust from a rocket exerts a force in a
vacuum. No force is generated in this case via the principle of free
expansion[i/]. If anyone thinks that I am inventing a term, [i]free
expansion appears in NASA's own glossary (under the first law of
thermodynamics)
http://er.jsc.nasa.gov/seh/f.html
Some people seem to believe that NASA/government hides "advanced
science" from the public when in fact they are better served hiding
basic science, principles known for over a hundred years, such as free
expansion or the correct form of Newton's 2nd law, if they want to
maintain their aura of technological superiority, doers miraculous feats
in space.