[thors_evil_twin]

What I asked, was would you believe them?

[totallackey]

What I asked, was would you believe them?

That sounds like a future based questioned that has no objective basis on which to form any conclusion at this time.

More information is needed.

[Tumeni]

Just ask scientists.

Name one that agrees with you, or cite a reliable scholarly source authored by one.

[thors_evil_twin]

Would you believe any of these scientists?
Bill Nye, Ahmed Mahjub, Paul Gradl, Shiva Prasad , Alessandro Gardi, Roberto Sabatini, Lynn Thalaal, Jeff Kang, Roland Schmehl

Books and there Authors
Advanced Control of Aircraft, Spacecraft, and Rockets (Tewari), Modern Engineering for Design of Liquid-Propellant Rocket Engines (Huzel, Huang), Rocket Propulsion Elements (Sutton, Biblarz), Elements of Propulsion, Gas Turbines and Rockets (Mattingly), Rocket Spacecraft Propulsion (Turner), Fundamentals of Compressible Flow with Aircraft and Rocket Propulsion (Yahya)

[stack]

I never said that the rocket would "blow away the entirety of the atmoplane of the earth." Where did that come from?

You asked for more clarity concerning how air under 14.7 psi provides resistance to the thrust of a rocket engine.

I suggest you search the internet for that clarity.

You completely dodged the question and refuse to support your own claim.

You claim that rockets push off the 14.7 psi of air underneath it. I asked you how 3+million pounds of thrust pushes off of 14.7 psi of air resistance. You said look it up (lame). I did, I can't find any scientific source that says a rocket pushes off of the atmosphere. What's your source for saying it does?

Here's a succinct explanation:

"If someone ever says "free expansion does no work" all they mean is that it does no work on the vacuum...This doesn't mean the gas doesn't do anything. Think of it this way: First, you have a closed container, sitting in vacuum and containing a gas with some nonzero pressure P inside. The force on the walls is the same in all directions, no matter the shape of the container, but for simplicity you can picture it as a cube with side length s. Each wall will have a force Ps2 pushing on it.

Now remove one wall. There will no longer be any force acting on it (your "free expansion" principle), but until the gas is fully evacuated there will be a force on the opposite wall. So your container has a net force in the opposite direction from the gas expulsion lasting for some time. Momentum is conserved; rockets work."

[Tumeni]

Think of it this way: First, you have a closed container, sitting in vacuum and containing a gas with some nonzero pressure P inside. The force on the walls is the same in all directions, no matter the shape of the container, but for simplicity you can picture it as a cube with side length s. Each wall will have a force Ps2 pushing on it.

Now remove one wall. There will no longer be any force acting on it (your "free expansion" principle), but until the gas is fully evacuated there will be a force on the opposite wall. So your container has a net force in the opposite direction from the gas expulsion lasting for some time. Momentum is conserved; rockets work."

I concur. I use a similar example over at YouTube;

Imagine the container, floating free in space; sealed, filled with rocket fuel and a means to ignite it remotely
Ignite the fuel
One of two things happens; the box is strong enough to contain the reaction, and holds, or - the expansion exceeds the strength of the box, which then ruptures at its weakest point
Debris is cast outward in the second scenario, showing the pressure exerted by the expansion on the inside surfaces, and showing all surfaces acted upon

Imagine the same fuel ignition with one side missing, and the result is as described above

[AATW]

A gas has no velocity when ejected, expelled, released into a vacuum...

Wow.

Dude, velocity is simply something moving in a given direction.
Just ask scientists. Or a dictionary.
Not having a go but if you don't even understand simple concepts like this then you really need to do a course on basic physics before thinking you understand how rockets work.

[totallackey]

I never said that the rocket would "blow away the entirety of the atmoplane of the earth." Where did that come from?

You asked for more clarity concerning how air under 14.7 psi provides resistance to the thrust of a rocket engine.

I suggest you search the internet for that clarity.

You completely dodged the question and refuse to support your own claim.

You claim that rockets push off the 14.7 psi of air underneath it. I asked you how 3+million pounds of thrust pushes off of 14.7 psi of air resistance. You said look it up (lame). I did, I can't find any scientific source that says a rocket pushes off of the atmosphere. What's your source for saying it does?

Here's a succinct explanation:

"If someone ever says "free expansion does no work" all they mean is that it does no work on the vacuum...This doesn't mean the gas doesn't do anything. Think of it this way: First, you have a closed container, sitting in vacuum and containing a gas with some nonzero pressure P inside. The force on the walls is the same in all directions, no matter the shape of the container, but for simplicity you can picture it as a cube with side length s. Each wall will have a force Ps2 pushing on it.

Now remove one wall. There will no longer be any force acting on it (your "free expansion" principle), but until the gas is fully evacuated there will be a force on the opposite wall. So your container has a net force in the opposite direction from the gas expulsion lasting for some time. Momentum is conserved; rockets work."

I claimed that air, at 14.7 psi, provides resistance.

This:

You claim that rockets push off the 14.7 psi of air underneath it.

I have not written.

The rest of the stuff you have written is fallacious, as the equal and opposite reaction to 0 = 0.

[Tumeni]

A gas has no velocity when ejected, expelled, released into a vacuum...

So if we took that engine test rig that I linked to earlier, and placed it in a vacuum, the engine exhaust would switch from having 418,000 lb/f of thrust to simply having exhaust that stood still?

[totallackey]

A gas has no velocity when ejected, expelled, released into a vacuum...

So if we took that engine test rig that I linked to earlier, and placed it in a vacuum, the engine exhaust would switch from having 418,000 lb/f of thrust to simply having exhaust that stood still?

Gas, when released into a vacuum, freely expands and performs 0 work.

Since gas still has mass and force (i.e., work) = m*a, then a must = 0, if the outcome is 0.

[AATW]

Since gas still has mass

Yes, it does. And what does it also have? Contrary to your statement above, it has velocity. It's moving in a direction, that's what velocity is.

Momentum = mass x velocity.

Both of those are clearly > 0, so the gas has momentum.

And that's why the rocket moves, because of conservation of momentum. Find a reputable scientist who disagrees.

[totallackey]

Since gas still has mass

Yes, it does. And what does it also have? Contrary to your statement above, it has velocity. It's moving in a direction, that's what velocity is.

Momentum = mass x velocity.

Both of those are clearly > 0, so the gas has momentum.

And that's why the rocket moves, because of conservation of momentum. Find a reputable scientist who disagrees.

Please...

Acceleration =/= velocity.

The rate of change of momentum in a particle is directly related to the change of force upon it.

Now you are claiming to have a different way of achieving 0 as an outcome to a simple math problem.

Free expansion states the following: Gas, when released into a vacuum, performs 0 work.

Since force (i.e., work) = mass*acceleration, and gas still has mass > 0...

If f = 0, that must mean that a also = 0.

That is math and there is no arguing against it.

Plus, if an object is freely expanding into nothingness, define the frame of reference to determine its exact velocity...

[AATW]

Now you are claiming to have a different way of achieving 0 as an outcome to a simple math problem.

I'm simply claiming these definitions:

velocity - something moving at a speed in a direction
mass - how much "stuff" something is made of

momentum - mass x velocity

Those are not my definitions, that is how physics defines those things.

Gas clearly has mass.
It is expelled out of the rocket at speed so it has velocity.

If mass and velocity are both greater than 0 then the momentum is greater than zero because maths.
And momentum is conserved because physics.

And that's how rockets work, not because they are "pushing" against anything.

You are the one erroneously equating the free expansion and word done result with the working of rockets. I believe somerled did too. I asked him to provide a credible source agreeing with him, I ask you the same. We both know you won't find one.

You might want to put "Free expansion states the following: Gas, when released into a vacuum, performs 0 work." in your signature to save you typing it in each post, but you are not correct in believing that this result shows that rockets can't work. Rockets work because they expel gas (mass) at speed out of the rocket (velocity). This gas has momentum. Momentum is conserved so the rocket is pushed in the opposite direction.

I'm sure you can find sources for the free expansion result but you are alone in equating that with the claim that rockets don't work in a vacuum.
Find a source which agrees with you.

[Tumeni]

Plus, if an object is freely expanding into nothingness, define the frame of reference to determine its exact velocity...

The frame of reference is the rocket. The exhaust gas starts out within it, and moves to a position outwith. It therefore covers some distance, over a period of time. Distance and time are used to compute velocity.

Unless you're suggesting that we are unable to determine the position of something(s) within a vacuum, because it's "nothingness" ... ?

[totallackey]

Now you are claiming to have a different way of achieving 0 as an outcome to a simple math problem.

I'm simply claiming these definitions:

velocity - something moving at a speed in a direction
mass - how much "stuff" something is made of

momentum - mass x velocity

Those are not my definitions, that is how physics defines those things.

Gas clearly has mass.
It is expelled out of the rocket at speed so it has velocity.

If mass and velocity are both greater than 0 then the momentum is greater than zero because maths.
And momentum is conserved because physics.

And that's how rockets work, not because they are "pushing" against anything.

You are the one erroneously equating the free expansion and word done result with the working of rockets. I believe somerled did too. I asked him to provide a credible source agreeing with him, I ask you the same. We both know you won't find one.

You might want to put "Free expansion states the following: Gas, when released into a vacuum, performs 0 work." in your signature to save you typing it in each post, but you are not correct in believing that this result shows that rockets can't work. Rockets work because they expel gas (mass) at speed out of the rocket (velocity). This gas has momentum. Momentum is conserved so the rocket is pushed in the opposite direction.

I'm sure you can find sources for the free expansion result but you are alone in equating that with the claim that rockets don't work in a vacuum.
Find a source which agrees with you.

The source that agrees with me is this.

The science of free expansion.

I noticed you totally ignored that velocity is a vector quantity.

Thus ignoring the frame of reference necessary for operating in an expanse of nothingness.

Ignored momentum has a direct relation to force.

Since force (work) = 0 in free expansion and work (w) = mass (m) * acceleration (a), if w = 0, then either m = 0, or a = 0, or both = 0. We know m >0, then that a = 0.

Sorry.

Those are all facts.

[AATW]

The source that agrees with me is this.

The science of free expansion.

You are claiming that result shows that rockets don't work in a vacuum. Please find a link which agrees with you.

I noticed you totally ignored that velocity is a vector quantity.

Correct. It has a magnitude and direction. The frame of reference is the rocket.

Do you disagree the gas has momentum?

[Tumeni]

I notice that the vacuum we were previously discussing is now "nothingness". Wonder why?

[totallackey]

The source that agrees with me is this.

The science of free expansion.

You are claiming that result shows that rockets don't work in a vacuum. Please find a link which agrees with you.

What link would I need?

Rockets are containers of gas.

If the gas they contain is expelled into a vacuum, the work performed by the gas = 0.

Since the equal and opposite reaction to 0 is also 0, the rocket does 0 work.

I noticed you totally ignored that velocity is a vector quantity.

Correct. It has a magnitude and direction. The frame of reference is the rocket.

Do you disagree the gas has momentum?

Since momentum is directly related to force, then yes.

Since the force (i.e., work) performed by gas expelled into a vacuum = 0, that must mean that

A. Mass = 0; or,
B. Acceleration = 0.

We already know Mass > 0.

Therefore, acceleration = 0, and therefore momentum = 0.

I notice that the vacuum we were previously discussing is now "nothingness". Wonder why?

Now claiming outer space is not a vacuum?

Not that I believe in such a thing as outer space anyway, but this would be a better argument on your part...

[AATW]

What link would I need?

Rockets are containers of gas.

If the gas they contain is expelled into a vacuum, the work performed by the gas = 0.

I'm not entirely convinced that a rocket which expels gas with explosive force is equivalent to the free expansion result.
But OK, let's say it is.
Find a link which agrees with you that this means rockets don't work in a vacuum. You are stating these two things are linked.
Do scientists agree with you?

Since momentum is directly related to force, then yes.

Oh. Well, momentum is velocity x mass. That isn't my definition, it's the one from physics.
Since the gas clearly has velocity - it's expelled from the rocket at high speed - and clearly has mass and the momentum is the product of those two things.
Both those things are > 0 so the product of them is.

[totallackey]

What link would I need?

Rockets are containers of gas.

If the gas they contain is expelled into a vacuum, the work performed by the gas = 0.

I'm not entirely convinced that a rocket which expels gas with explosive force is equivalent to the free expansion result.
But OK, let's say it is.
Find a link which agrees with you that this means rockets don't work in a vacuum. You are stating these two things are linked.
Do scientists agree with you?

Since momentum is directly related to force, then yes.

Oh. Well, momentum is velocity x mass. That isn't my definition, it's the one from physics.
Since the gas clearly has velocity - it's expelled from the rocket at high speed - and clearly has mass and the momentum is the product of those two things.
Both those things are > 0 so the product of them is.

We get your not entirely convinced.

That does not change the fact that gas expelled into a vacuum does 0 work.