[BRrollin]

Lackey, JP Joule would be turning in his grave at how some people are misinterpreting his work and claiming his support for their own theories. 

I think everyone is happy with his "free-expansion into a vacuum" experiment.  In the demonstration normally presented, the gas is released from its containment on the left, along the x-axis, into the evacuated containment on the right, such that it then occupies both parts of the vessel.  The gas comes to rest.  The vessel is insulated.  The internal mass and energy and heat remain unchanged during the process.  No work.

Lets consider the first individual molecule of gas to make that journey.  When the gas is released, that molecule is accelerated through the aperture into vacuum.  It has velocity.  That velocity is the result of the pressure of all its fellow molecules pushing against it.  It is an action to the right, and at some point will produce a reaction to the left. 

The next molecule does the same thing; same action, same reaction.  But now there are 2 molecules in the right hand containment, and they ADDITIONALLY repel each other, so also accelerating along the y- and z-axes.  They are expanding freely in a vacuum.  But they still have their initial velocity to the right on the x-axis. 

Pretty soon, roughly half of the remaining molecules will join their colleagues on the journey.  The acceleration of each along the x-axis will be infinitesimally less than the first, because the right-hand containment is beginning to pressurise.  Each will accelerate to the right on the x-axis, an action, creating the need for a reaction.  They will also expand freely along the y- and z-axes.  But you have to remember that whatever acceleration they receive through free-expansion is ADDITIONAL to the velocity they had to the right initially. 

Meanwhile, our first molecule has hit the right-hand wall af the containment, and comes to rest.  By reducing its velocity to zero, it has accelerated to the LEFT on the x-axis.  This is an action to the left, and will produce a reaction to the right.  But just a minute, we left an action/reaction pair hanging a few paragraphs back, which is convenient because when we dial that in, then the algebraic equation for all the force applied to Molecule #1 is zero.  It started at rest and finished at rest.  No action.  No reaction.  No work.  Thank you JPJ. 

Now lets transfer the left-hand containment to the infinite majesty of space.  When released, our molecules accelerate to the right, an action.  Yes, the gas disperses freely in 3 dimensions into the vacuum but the individual molecules retain their velocity along the x-axis.  Although the gas is very, very, very dispersed, it hasn't ceased to exist, the molecules still have mass and velocity.  They got that velocity by being accelerated out of the containment; an action to the right, producing a reaction of the containment to the left.  And because they don't hit the wall of a right hand containment, so there is no second action/reaction pair, they keep going.  For ever. 

As does the containment, to the left.  For ever. 

Work done.

Wrong...just totally wrong...

Any gas released to a vacuum does 0 work.

No matter how you try to fluff it up or otherwise hold on to your fantasy.

Look at all the videos provided here for plain visual proof you are wrong.

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

[totallackey]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Because every single video posted here clearly demonstrate that rockets do not work in a vacuum.

[BRrollin]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Becasue every single video posted here clearly demonstrate that rockets do not work in a vacuum.

It might be helpful for you to learn a bit more about how rockets work - beyond these opinion videos that are not scientifically sound.

Anyone can make a video. What we want to do is assess content on its merits. We don’t want to just accept a source because it confirms what we want it to.

Anyway, many here claim that the NASA videos are fake, so I suppose by that same standard I could just say that these videos are fake, and insist on different evidence to support your claim.

[totallackey]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Because every single video posted here clearly demonstrate that rockets do not work in a vacuum.

It might be helpful for you to learn a bit more about how rockets work - beyond these opinion videos that are not scientifically sound.

Anyone can make a video. What we want to do is assess content on its merits. We don’t want to just accept a source because it confirms what we want it to.

Anyway, many here claim that the NASA videos are fake, so I suppose by that same standard I could just say that these videos are fake, and insist on different evidence to support your claim.

Yeah, I suppose we should never mind these videos were done up with the outcome designed to PROVE rockets can work in a vacuum...

And, I suppose, we should all ignore the fact the videos were offered here as PROOF that rockets do indeed in work in a vacuum...

And I definitely KNOW you want to IGNORE the FACT the videos clearly show otherwise...

But go ahead...your chance to KILL TWO BIRDS WITH ONE STONE...show us an actual video of an actual rocket working in a vacuum...

[BRrollin]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Becasue every single video posted here clearly demonstrate that rockets do not work in a vacuum.

It might be helpful for you to learn a bit more about how rockets work - beyond these opinion videos that are not scientifically sound.

Anyone can make a video. What we want to do is assess content on its merits. We don’t want to just accept a source because it confirms what we want it to.

Anyway, many here claim that the NASA videos are fake, so I suppose by that same standard I could just say that these videos are fake, and insist on different evidence to support your claim.

Yeah, I suppose we should never mind these videos were done up with the outcome designed to PROVE rockets can work in a vacuum...

And, I suppose, we should all ignore the fact the videos were offered here as PROOF that rockets do indeed in work in a vacuum...

And I definitiely KNOW you want to IGNORE the FACT the videos clearly show otherwise...

But go ahead...your chance to KILL TWO BIRDS WITH ONE STONE...show us an actual video of an actual rocket working in a vacuum...

Why would anyone try to “prove” how rockets work by addressing thermodynamics?

It’s like trying to prove the existence of god by investigating rainbows.

Anyway, since you asked, check out these fake videos





I gotta tell ya man, all pretense aside, out of all the arguments against a round earth, the whole “rockets can’t work in space” (aka conservation of linear momentum isn’t a thing) has to be the most ridiculous position possible. We can make vacuum chambers on Earth! This is testable.

Question: can flies fly in a vacuum?

There’s a nice YouTube video showing the answer to this question. Watching it might help you think this through.

[totallackey]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Becasue every single video posted here clearly demonstrate that rockets do not work in a vacuum.

It might be helpful for you to learn a bit more about how rockets work - beyond these opinion videos that are not scientifically sound.

Anyone can make a video. What we want to do is assess content on its merits. We don’t want to just accept a source because it confirms what we want it to.

Anyway, many here claim that the NASA videos are fake, so I suppose by that same standard I could just say that these videos are fake, and insist on different evidence to support your claim.

Yeah, I suppose we should never mind these videos were done up with the outcome designed to PROVE rockets can work in a vacuum...

And, I suppose, we should all ignore the fact the videos were offered here as PROOF that rockets do indeed in work in a vacuum...

And I definitiely KNOW you want to IGNORE the FACT the videos clearly show otherwise...

But go ahead...your chance to KILL TWO BIRDS WITH ONE STONE...show us an actual video of an actual rocket working in a vacuum...

Why would anyone try to “prove” how rockets work by addressing thermodynamics?

It’s like trying to prove the existence of god by investigating rainbows.

Anyway, since you asked, check out these fake videos





I gotta tell ya man, all pretense aside, out of all the arguments against a round earth, the whole “rockets can’t work in space” (aka conservation of linear momentum isn’t a thing) has to be the most ridiculous position possible. We can make vacuum chambers on Earth! This is testable.

Question: can flies fly in a vacuum?

There’s a nice YouTube video showing the answer to this question. Watching it might help you think this through.

The videos which you just provided have already been provided in the thread.

I think I have discovered the nature of your problem.

You can't read.

Kindly point out where I have written that rockets do not work in space.

I never wrote that rockets do not work in space.

Now, once again...please post a video of a rocket working in a vacuum.

Because you have not posted one (and nobody else has either).

Because rockets do not work in a vacuum.

The video evidence clearly demonstrates that rockets do not work in a vacuum.

[BRrollin]

So if you fart in outer space, then the expansion of your fart gas does zero work.

BUT(T), in the act of farting, the fart gas leaves your anus with a momentum. So by conservation of momentum, your body moves in the opposite direction.

The only things rockets do is make the gas leave at very high speeds - burning the fuel converts stores chemical energy into kinetic energy. Since the gas leaves at high speeds, this gives the rocket more momentum.

It’s like if you had a really big, powerful fart - you would get a bigger boost.

In this way, you could fart yourself around outer space.

Rather than this continued empty content repost of “expansion of gas in vacuum does zero work.”

Which is a straw man, because the expansion of the gas is irrelevant for rocket propulsion. Whatever the gas does after it leaves the rocket just doesn’t matter.

Well, I suggest you look at the videos posted here and inform everyone that what you just wrote is the equivalent of a gigantic fart in the wind...

It stinks.

Becasue every single video posted here clearly demonstrate that rockets do not work in a vacuum.

It might be helpful for you to learn a bit more about how rockets work - beyond these opinion videos that are not scientifically sound.

Anyone can make a video. What we want to do is assess content on its merits. We don’t want to just accept a source because it confirms what we want it to.

Anyway, many here claim that the NASA videos are fake, so I suppose by that same standard I could just say that these videos are fake, and insist on different evidence to support your claim.

Yeah, I suppose we should never mind these videos were done up with the outcome designed to PROVE rockets can work in a vacuum...

And, I suppose, we should all ignore the fact the videos were offered here as PROOF that rockets do indeed in work in a vacuum...

And I definitiely KNOW you want to IGNORE the FACT the videos clearly show otherwise...

But go ahead...your chance to KILL TWO BIRDS WITH ONE STONE...show us an actual video of an actual rocket working in a vacuum...

Why would anyone try to “prove” how rockets work by addressing thermodynamics?

It’s like trying to prove the existence of god by investigating rainbows.

Anyway, since you asked, check out these fake videos





I gotta tell ya man, all pretense aside, out of all the arguments against a round earth, the whole “rockets can’t work in space” (aka conservation of linear momentum isn’t a thing) has to be the most ridiculous position possible. We can make vacuum chambers on Earth! This is testable.

Question: can flies fly in a vacuum?

There’s a nice YouTube video showing the answer to this question. Watching it might help you think this through.

The videos which you just provided have already been provided in the thread.

I think I have discovered the nature of your problem.

You can't read.

Kindly point out where I have written that rockets do not work in space.

I never wrote that rockets do not work in space.

Now, once again...please post a video of a rocket working in a vacuum.

Because you have not posted one (and nobody else has either).

Because rockets do not work in a vacuum.

The video evidence clearly demonstrates that rockets do not work in a vacuum.

Really? I think they clearly demonstrate the opposite. Care to explain?

The first shows that they can fire just fine, and propel gas.

The second shows that conservation of momentum works in a vacuum.

[totallackey]

Really? I think they clearly demonstrate the opposite. Care to explain?

The first shows that they can fire just fine, and propel gas.

Yeah, they can fire...but they do not move until the pressure in the container is of a sort to be able to provide a defined plume.

The second shows that conservation of momentum works in a vacuum.

There is no vacuum present when the can starts moving.

Once gas is expelled the vacuum ceases to exist.

[iCare]

Yeah, they can fire...but they do not move until the pressure in the container is of a sort to be able to provide a defined plume.

You have claimed so before und it still can't validly be concluded from what is shown in the videos - as explained e.g. here:

Rockets will always remain still for a short while after ignition, as thrust needs to build and inertia must be overcome.
To draw a valid conclusion from the videos that would have to be taken into account, i.e. by a series of experiments to calibrate for different levels of pressure .
With the data provided in the videos this may or may not be coincidental.

That may be what you want to see in them, but it cannot validly be concluded from those videos.
First of all, those experiments are more "proof of concept" on an enthusiast level than reliable scientific experiments. (No offence to the creators; I appreciate their effort and the experiments do illustrated some aspects well.)
We don't really know enough about the setup and all parameters in detail to tell if what you believe to see is a direct result of pressure rising or just coincidence.

As far as I recall, you haven't responded to either explanation, so they stand unchallenged.

iC

[BRrollin]

Really? I think they clearly demonstrate the opposite. Care to explain?

The first shows that they can fire just fine, and propel gas.

Yeah, they can fire...but they do not move until the pressure in the container is of a sort to be able to provide a defined plume.

The second shows that conservation of momentum works in a vacuum.

There is no vacuum present when the can starts moving.

What do you think this “defined plume” does, exactly?

So as with the can, wouldn’t this also be the case in outer space?

[Dr Van Nostrand]

Wrong...just totally wrong...

Any gas released to a vacuum does 0 work.

No matter how you try to fluff it up or otherwise hold on to your fantasy.

Look at all the videos provided here for plain visual proof you are wrong.

So again, just to be clear, if you're floating in space sitting on a hand grenade and we detonate it, you will not move?

No work will be done?

[stack]

Okay will do!

I’ll probably start with those same articles. They seem to know about it.

Unless you have some other sources about entropy that might help me learn about it in the way you do?

Simply put, entropy is a quantity representing the availability of the thermal energy in a system to be converted into work.

A rocket cannot possibly maintain constant entropy.

Incorrect, as you will see in a moment.

As stack writes falsely:

Rocket engines are considered Isentropic systems where entropy remains unchanged.

Isentropic nozzle flow
"Whenever a gas is forced through a tube, the gaseous molecules are deflected by the tube's walls. If the speed of the gas is much less than the speed of sound, the gas density will remain constant and the velocity of the flow will increase. However, as the speed of the flow approximates the speed of sound, compressibility effects on the gas are to be considered. The density of the gas becomes position dependent. While considering flow through a tube, if the flow is very gradually compressed (i.e. area decreases) and then gradually expanded (i.e. area increases), the flow conditions are restored (i.e. return to its initial position). So, such a process is a reversible process. According to the Second Law of Thermodynamics, whenever there is a reversible and adiabatic flow, constant value of entropy is maintained. Engineers classify this type of flow as an isentropic flow of fluids.”

So you see, a Nonisentropic process, like Free Expansion, does not apply to an Isentropic system. Apples and oranges.

...it is obviously written by someone trying to engage in double speak...

And stack, while he talks of the rocket engine, does NOT want you to look behind the curtain containing the rocket exhaust, which is where the meat and potatoes is at.

A rocket has a fixed amount of fuel and a fixed amount of potential energy.

Rockets have a fixed rate of discharge at any particular point of time.

Sooner or later, there is no more more potential energy available.

Therefore, rockets cannot maintain unchanged entropy when in operation.

And that process is not "reversible," nor can it possibly be "adiabatic," as described in stacks' ridiculous post, once initiated. Rockets experience no reverse flow of fluids or exhaust. The exhaust is supposedly taking place in the vacuum of outer space...again, where all the fakers want you to believe that gas, just because it is coming from a rocket, can somehow, someway...be different...but it, of course...cannot.

Gas released into a vacuum...does no work.

All of what you wrote is false and backed by zero evidence or science. Regarding Rockets and Isentropic Flow:

"As a gas is forced through a tube, the gas molecules are deflected by the walls of the tube. If the speed of the gas is much less than the speed of sound of the gas, the density of the gas remains constant and the velocity of the flow increases. However, as the speed of the flow approaches the speed of sound we must consider compressibility effects on the gas. The density of the gas varies from one location to the next. Considering flow through a tube, as shown in the figure, if the flow is very gradually compressed (area decreases) and then gradually expanded (area increases), the flow conditions return to their original values. We say that such a process is reversible. From a consideration of the second law of thermodynamics, a reversible flow maintains a constant value of entropy. Engineers call this type of flow an isentropic flow; a combination of the Greek word "iso" (same) and entropy."

More information and equations can be found here:
https://www.grc.nasa.gov/WWW/k-12/airplane/isentrop.html

You see, engineers call this type of flow an isentropic flow. You are neither an engineer, nor a rocket scientist, nor an expert in thermodynamics yet you claim to know more than people who are without providing any evidence. Your "free expansion does no work" is nonisentropic and does not apply here to rocket engines, so that argument you originally had is toast.

For once, please provide some evidence for you claims rather than just ignorant unfounded bluster.

For once, understand what the hell you are reading and where the flow is taking place.

I mean, read the whole thing...

And make note of the word TUBE!

Gas...in a...TUBE...

Not gas...in a...nozzle.

Now, goodbye to your lack of understanding.

Just how you never provide evidence you apparently don't read evidence either. Here's the next paragraph after the one the one I cited above:

"Isentropic flows occur when the change in flow variables is small and gradual, such as the ideal flow through the nozzle shown above. The generation of sound waves is an isentropic process. A supersonic flow that is turned while the flow area increases is also isentropic. We call this an isentropic expansion because of the area increase."

Here's the image 'shown above' that it refers to:



You really have to start providing some evidence rather than just jibber-jabber. For once and for all the nonisentropic law of free expansion where gas in a vacuum 'does no work' does not apply to rockets. Rockets are isentropic, period. Read the literature. If you disagree, provide some evidence to back up your claims, not just your own ignorance of the subject.

Holy crap...isentropic relative to the sound?

LOL!

Like, A: Sound could even travel in a vacuum...

The speed of sound is a measurement, approximately 343 m/s. Read up on it.

2) Gas does no work when released to a vacuum...

Take your nonsense peddling show elsewhere.

Again, for the umpteenth time, free expansion or, "gas does no work in a vacuum", is in reference to nonisentropic systems. Rockets, as has been shown over and over again, are an isentropic system. If you don't agree then I suggest you bone up on your rocket science curriculum. If you are unwilling to learn something then why don't you answer Dr Van Nostrand's question:

So again, just to be clear, if you're floating in space sitting on a hand grenade and we detonate it, you will not move?

No work will be done?

[totallackey]

Yeah, they can fire...but they do not move until the pressure in the container is of a sort to be able to provide a defined plume.

You have claimed so before und it still can't validly be concluded from what is shown in the videos - as explained e.g. here:

Rockets will always remain still for a short while after ignition, as thrust needs to build and inertia must be overcome.
To draw a valid conclusion from the videos that would have to be taken into account, i.e. by a series of experiments to calibrate for different levels of pressure .
With the data provided in the videos this may or may not be coincidental.

The measurements relative to the amount of vacuum can be seen in the videos on the same gauges they used to demonstrate the presence of vacuum.

That may be what you want to see in them, but it cannot validly be concluded from those videos.
First of all, those experiments are more "proof of concept" on an enthusiast level than reliable scientific experiments. (No offence to the creators; I appreciate their effort and the experiments do illustrated some aspects well.)
We don't really know enough about the setup and all parameters in detail to tell if what you believe to see is a direct result of pressure rising or just coincidence.

As far as I recall, you haven't responded to either explanation, so they stand unchallenged.

iC

I have responded to all of the points raised.

The concept the creators of these videos demonstrate is that clearly rockets do not work in a vacuum.

[totallackey]

Okay will do!

I’ll probably start with those same articles. They seem to know about it.

Unless you have some other sources about entropy that might help me learn about it in the way you do?

Simply put, entropy is a quantity representing the availability of the thermal energy in a system to be converted into work.

A rocket cannot possibly maintain constant entropy.

Incorrect, as you will see in a moment.

As stack writes falsely:

Rocket engines are considered Isentropic systems where entropy remains unchanged.

Isentropic nozzle flow
"Whenever a gas is forced through a tube, the gaseous molecules are deflected by the tube's walls. If the speed of the gas is much less than the speed of sound, the gas density will remain constant and the velocity of the flow will increase. However, as the speed of the flow approximates the speed of sound, compressibility effects on the gas are to be considered. The density of the gas becomes position dependent. While considering flow through a tube, if the flow is very gradually compressed (i.e. area decreases) and then gradually expanded (i.e. area increases), the flow conditions are restored (i.e. return to its initial position). So, such a process is a reversible process. According to the Second Law of Thermodynamics, whenever there is a reversible and adiabatic flow, constant value of entropy is maintained. Engineers classify this type of flow as an isentropic flow of fluids.”

So you see, a Nonisentropic process, like Free Expansion, does not apply to an Isentropic system. Apples and oranges.

...it is obviously written by someone trying to engage in double speak...

And stack, while he talks of the rocket engine, does NOT want you to look behind the curtain containing the rocket exhaust, which is where the meat and potatoes is at.

A rocket has a fixed amount of fuel and a fixed amount of potential energy.

Rockets have a fixed rate of discharge at any particular point of time.

Sooner or later, there is no more more potential energy available.

Therefore, rockets cannot maintain unchanged entropy when in operation.

And that process is not "reversible," nor can it possibly be "adiabatic," as described in stacks' ridiculous post, once initiated. Rockets experience no reverse flow of fluids or exhaust. The exhaust is supposedly taking place in the vacuum of outer space...again, where all the fakers want you to believe that gas, just because it is coming from a rocket, can somehow, someway...be different...but it, of course...cannot.

Gas released into a vacuum...does no work.

All of what you wrote is false and backed by zero evidence or science. Regarding Rockets and Isentropic Flow:

"As a gas is forced through a tube, the gas molecules are deflected by the walls of the tube. If the speed of the gas is much less than the speed of sound of the gas, the density of the gas remains constant and the velocity of the flow increases. However, as the speed of the flow approaches the speed of sound we must consider compressibility effects on the gas. The density of the gas varies from one location to the next. Considering flow through a tube, as shown in the figure, if the flow is very gradually compressed (area decreases) and then gradually expanded (area increases), the flow conditions return to their original values. We say that such a process is reversible. From a consideration of the second law of thermodynamics, a reversible flow maintains a constant value of entropy. Engineers call this type of flow an isentropic flow; a combination of the Greek word "iso" (same) and entropy."

More information and equations can be found here:
https://www.grc.nasa.gov/WWW/k-12/airplane/isentrop.html

You see, engineers call this type of flow an isentropic flow. You are neither an engineer, nor a rocket scientist, nor an expert in thermodynamics yet you claim to know more than people who are without providing any evidence. Your "free expansion does no work" is nonisentropic and does not apply here to rocket engines, so that argument you originally had is toast.

For once, please provide some evidence for you claims rather than just ignorant unfounded bluster.

For once, understand what the hell you are reading and where the flow is taking place.

I mean, read the whole thing...

And make note of the word TUBE!

Gas...in a...TUBE...

Not gas...in a...nozzle.

Now, goodbye to your lack of understanding.

Just how you never provide evidence you apparently don't read evidence either. Here's the next paragraph after the one the one I cited above:

"Isentropic flows occur when the change in flow variables is small and gradual, such as the ideal flow through the nozzle shown above. The generation of sound waves is an isentropic process. A supersonic flow that is turned while the flow area increases is also isentropic. We call this an isentropic expansion because of the area increase."

Here's the image 'shown above' that it refers to:



You really have to start providing some evidence rather than just jibber-jabber. For once and for all the nonisentropic law of free expansion where gas in a vacuum 'does no work' does not apply to rockets. Rockets are isentropic, period. Read the literature. If you disagree, provide some evidence to back up your claims, not just your own ignorance of the subject.

Holy crap...isentropic relative to the sound?

LOL!

Like, A: Sound could even travel in a vacuum...

The speed of sound is a measurement, approximately 343 m/s. Read up on it.

Yeah, we know...having nothing to do with what you tried to introduce and nothing to do with gas performing no work in a vacuum.

2) Gas does no work when released to a vacuum...

Take your nonsense peddling show elsewhere.

Again, for the umpteenth time, free expansion or, "gas does no work in a vacuum", is in reference to nonisentropic systems. Rockets, as has been shown over and over again, are an isentropic system. If you don't agree then I suggest you bone up on your rocket science curriculum.

When gas is flowing in a tube, isentropic...not relevant to the exhaust.

When sound is emitted as a result of the exhaust, isentropic...not possible for sound to travel in a vacuum...

So, isentropic for both, up to the point when a rocket enters any part of a vacuum.

At that point, the gas flow in the tubes remains isentropic...any gas flow from the nozzle becomes, because of the law of free expansion, becomes freely expanding gas.

Gas that freely expands does no work.

Bye bye now...

[BRrollin]

Okay will do!

I’ll probably start with those same articles. They seem to know about it.

Unless you have some other sources about entropy that might help me learn about it in the way you do?

Simply put, entropy is a quantity representing the availability of the thermal energy in a system to be converted into work.

A rocket cannot possibly maintain constant entropy.

Incorrect, as you will see in a moment.

As stack writes falsely:

Rocket engines are considered Isentropic systems where entropy remains unchanged.

Isentropic nozzle flow
"Whenever a gas is forced through a tube, the gaseous molecules are deflected by the tube's walls. If the speed of the gas is much less than the speed of sound, the gas density will remain constant and the velocity of the flow will increase. However, as the speed of the flow approximates the speed of sound, compressibility effects on the gas are to be considered. The density of the gas becomes position dependent. While considering flow through a tube, if the flow is very gradually compressed (i.e. area decreases) and then gradually expanded (i.e. area increases), the flow conditions are restored (i.e. return to its initial position). So, such a process is a reversible process. According to the Second Law of Thermodynamics, whenever there is a reversible and adiabatic flow, constant value of entropy is maintained. Engineers classify this type of flow as an isentropic flow of fluids.”

So you see, a Nonisentropic process, like Free Expansion, does not apply to an Isentropic system. Apples and oranges.

...it is obviously written by someone trying to engage in double speak...

And stack, while he talks of the rocket engine, does NOT want you to look behind the curtain containing the rocket exhaust, which is where the meat and potatoes is at.

A rocket has a fixed amount of fuel and a fixed amount of potential energy.

Rockets have a fixed rate of discharge at any particular point of time.

Sooner or later, there is no more more potential energy available.

Therefore, rockets cannot maintain unchanged entropy when in operation.

And that process is not "reversible," nor can it possibly be "adiabatic," as described in stacks' ridiculous post, once initiated. Rockets experience no reverse flow of fluids or exhaust. The exhaust is supposedly taking place in the vacuum of outer space...again, where all the fakers want you to believe that gas, just because it is coming from a rocket, can somehow, someway...be different...but it, of course...cannot.

Gas released into a vacuum...does no work.

All of what you wrote is false and backed by zero evidence or science. Regarding Rockets and Isentropic Flow:

"As a gas is forced through a tube, the gas molecules are deflected by the walls of the tube. If the speed of the gas is much less than the speed of sound of the gas, the density of the gas remains constant and the velocity of the flow increases. However, as the speed of the flow approaches the speed of sound we must consider compressibility effects on the gas. The density of the gas varies from one location to the next. Considering flow through a tube, as shown in the figure, if the flow is very gradually compressed (area decreases) and then gradually expanded (area increases), the flow conditions return to their original values. We say that such a process is reversible. From a consideration of the second law of thermodynamics, a reversible flow maintains a constant value of entropy. Engineers call this type of flow an isentropic flow; a combination of the Greek word "iso" (same) and entropy."

More information and equations can be found here:
https://www.grc.nasa.gov/WWW/k-12/airplane/isentrop.html

You see, engineers call this type of flow an isentropic flow. You are neither an engineer, nor a rocket scientist, nor an expert in thermodynamics yet you claim to know more than people who are without providing any evidence. Your "free expansion does no work" is nonisentropic and does not apply here to rocket engines, so that argument you originally had is toast.

For once, please provide some evidence for you claims rather than just ignorant unfounded bluster.

For once, understand what the hell you are reading and where the flow is taking place.

I mean, read the whole thing...

And make note of the word TUBE!

Gas...in a...TUBE...

Not gas...in a...nozzle.

Now, goodbye to your lack of understanding.

Just how you never provide evidence you apparently don't read evidence either. Here's the next paragraph after the one the one I cited above:

"Isentropic flows occur when the change in flow variables is small and gradual, such as the ideal flow through the nozzle shown above. The generation of sound waves is an isentropic process. A supersonic flow that is turned while the flow area increases is also isentropic. We call this an isentropic expansion because of the area increase."

Here's the image 'shown above' that it refers to:



You really have to start providing some evidence rather than just jibber-jabber. For once and for all the nonisentropic law of free expansion where gas in a vacuum 'does no work' does not apply to rockets. Rockets are isentropic, period. Read the literature. If you disagree, provide some evidence to back up your claims, not just your own ignorance of the subject.

Holy crap...isentropic relative to the sound?

LOL!

Like, A: Sound could even travel in a vacuum...

The speed of sound is a measurement, approximately 343 m/s. Read up on it.

Yeah, we know...having nothing to do with what you tried to introduce and nothing to do with gas performing no work in a vacuum.

2) Gas does no work when released to a vacuum...

Take your nonsense peddling show elsewhere.

Again, for the umpteenth time, free expansion or, "gas does no work in a vacuum", is in reference to nonisentropic systems. Rockets, as has been shown over and over again, are an isentropic system. If you don't agree then I suggest you bone up on your rocket science curriculum.

When gas is flowing in a tube, isentropic...not relevant to the exhaust.

When sound is emitted as a result of the exhaust, isentropic...not possible for sound to travel in a vacuum...

So, isentropic for both, up to the point when a rocket enters any part of a vacuum.

At that point, the gas flow in the tubes remains isentropic...any gas flow from the nozzle becomes, because of the law of free expansion, becomes freely expanding gas.

Gas that freely expands does no work.

Bye bye now...

So nice to have you back

Gas flowing in a tube is isentropic only in the case of ideal fluid flow.

Also, sound can travel in a vacuum. Any detonation, like a supernovae, sends a shock front.

These are fairly basic concepts many study in college.

[iCare]

I have responded to all of the points raised.

I only found a response to my first statement - are you referring to this?

Rockets will always remain still for a short while after ignition, as thrust needs to build and inertia must be overcome.

Sure they do, even in a pressurized environment.

Doesn't alleviate the fact a pressurized environment is required, as evidenced and presented in the videos in this thread.

You agree, that rockets remain still for a short while after ignition in any environment, thereby invalidating your claim, that the delay would prove a vacuum/lack of pressure.
The "requirement of a pressurized environment" is not a fact, but what has been challenged; those videos do not evidence that requirement, much less do they make it a fact.. 

To draw a valid conclusion from the videos that would have to be taken into account, i.e. by a series of experiments to calibrate for different levels of pressure .
With the data provided in the videos this may or may not be coincidental.

If you watch the videos, it demonstrates that gas begins to perform work at about the same levels on the gauges.

If you repeat an experiment with roughly the same parameters, you would expect to get roughly the same results. That (being one of the points I made) doesn't really tell us anything.
Without a baseline and a set of experiments to eliminate potential unwanted effects, you can't validly tell, if the level on the gauges is
- really same because of the pressure reached at that time,
- coincidentally the same at time at which inertia has been overcome or
- coincidentally the same due to any other aspect of the experiment we may not even be aware of.

So yes, you did respond to that.
However, you agreed with me for an important part and didn't provide valid reason for disagreeing with the remaining part.

The concept the creators of these videos demonstrate is that clearly rockets do not work in a vacuum.

As repeatedly explained (e.g. see above), that is not what those videos demonstrate.

Rockets do not care about the vacuum (or any environment) because the relevant parts of the propulsion process (isentropic flow through a nozzle; creating thrust) is independent of the environment.
When the exhaust "enters the vacuum" and dissipates, the work has already been done.
=> Rockets work in a vacuum.

iC

[totallackey]

I have responded to all of the points raised.

I only found a response to my first statement - are you referring to this?

Rockets will always remain still for a short while after ignition, as thrust needs to build and inertia must be overcome.

Sure they do, even in a pressurized environment.

Doesn't alleviate the fact a pressurized environment is required, as evidenced and presented in the videos in this thread.

You agree, that rockets remain still for a short while after ignition in any environment, thereby invalidating your claim, that the delay would prove a vacuum/lack of pressure.
The "requirement of a pressurized environment" is not a fact, but what has been challenged; those videos do not evidence that requirement, much less do they make it a fact..

The delay you see when rockets launch on TV (i.e., the government or private industry launches) is due to the fact that the plume is not yet contained enough by the surrounding pressure in order for the rocket to take flight.

This does not apply to model rockets of course, because the weight is not sufficient enough to require it.

And yet, what you see here is model rocket engines, failing to perform, until such time as the only constant (sufficient surrounding pressure) is met. 

To draw a valid conclusion from the videos that would have to be taken into account, i.e. by a series of experiments to calibrate for different levels of pressure .
With the data provided in the videos this may or may not be coincidental.

If you watch the videos, it demonstrates that gas begins to perform work at about the same levels on the gauges.

If you repeat an experiment with roughly the same parameters, you would expect to get roughly the same results. That (being one of the points I made) doesn't really tell us anything.
Without a baseline and a set of experiments to eliminate potential unwanted effects, you can't validly tell, if the level on the gauges is
- really same because of the pressure reached at that time,
- coincidentally the same at time at which inertia has been overcome or
- coincidentally the same due to any other aspect of the experiment we may not even be aware of.

So yes, you did respond to that.
However, you agreed with me for an important part and didn't provide valid reason for disagreeing with the remaining part.

The concept the creators of these videos demonstrate is that clearly rockets do not work in a vacuum.

As repeatedly explained (e.g. see above), that is not what those videos demonstrate.

Rockets do not care about the vacuum (or any environment) because the relevant parts of the propulsion process (isentropic flow through a nozzle; creating thrust) is independent of the environment.
When the exhaust "enters the vacuum" and dissipates, the work has already been done.
=> Rockets work in a vacuum.

iC

The described isentropic flow through the nozzle applies to sound and has nothing to do with propulsion, so just quit writing about stuff you have no clue about.

[totallackey]

So nice to have you back

Gas flowing in a tube is isentropic only in the case of ideal fluid flow.

Also, sound can travel in a vacuum. Any detonation, like a supernovae, sends a shock front.

These are fairly basic concepts many study in college.

Sound has nothing to do with the issue of propulsion.

Isentropic process of gas flowing in a tube has nothing to do with propulsion.

[BRrollin]

So nice to have you back

Gas flowing in a tube is isentropic only in the case of ideal fluid flow.

Also, sound can travel in a vacuum. Any detonation, like a supernovae, sends a shock front.

These are fairly basic concepts many study in college.

Sound has nothing to do with the issue of propulsion.

Isentropic process of gas flowing in a tube has nothing to do with propulsion.

You got it! Finally.

None of these things has to do with propulsion.

Conservation of momentum is what creates the propulsion.

If you fart in space, you move in the opposite direction to your fart plume.

It took a while, but we got there!

[iCare]

Despite quoting it, you skipped the part explaining, why those videos show no valid prove of rockets not working in a vacuum.
Fine with me, I'll accept it as tacit agreement.

The delay you see when rockets launch on TV (i.e., the government or private industry launches) is due to the fact that the plume is not yet contained enough by the surrounding pressure in order for the rocket to take flight.

How about this explanation:
A rocket engine (like many engines) needs a certain time to get up to full working power.
While the thrust provides less acceleration than gravitation (or UA if one leans that way) working the other way, the rocket remains stationary.
Then acceleration will be very slow, but increasing until the rocket engine provides constant acceleration (depending on the rocket engine, that might be adjustable, but for take-off it's reasonable to assume constant full thrust).
The observable result would be a delay until somethings happens, then slow and finally constant acceleration.

On the other hand:
How can a gaseous atmosphere "contain" a plume?
The atmosphere will do some "shaping", as it is being displaced by exhaust, but that effect quickly evens out, as the amount of exhaust is rather insignificant in comparison to the amount of atmosphere surrounding it.
The exhaust is expelled at speed and will be slowed done by the resistance of the surrounding atmosphere. At the same time it will dissipate, as exhaust and atmosphere mix.
Impressive to look at, but irrelevant for propulsion. Pushing yourself off "thin air" doesn't work much better than pushing yourself off a vacuum.
Rockets work in any environment, because they do neither.
 

This does not apply to model rockets of course, because the weight is not sufficient enough to require it.

Why are you making a special case for model rockets?
 

The described isentropic flow through the nozzle applies to sound and has nothing to do with propulsion.

Why would isentropic flow through the nozzle have anything to do with sound? It is about thermodynamics not acoustics. The speed of sound is relevant, but not sound as such.
In contrast isentropic flow is relevant to work being done, so it is relevant to propulsion.

iC