People on skateboards.

Quote from: Yendor on October 01, 2015, 12:55:24 PM

Guys, Guys, enough of this bickering. Let me show you how rockets work.



So you see, rockets do need the ground and even the atmosphere to push against or they won't go anywhere, especially in space.

Your explaination is garbage. The exhaust exits the rocket and hits the ground. The exhaust pushes against the ground an the ground pushed against the exhaust. The exhaust had already left the rocket at this point so how does that then push the rocket......?

The reality. Reactants ignite in the combustion chamber and impact the reaction chamber walls. the exhaust pushes against the walls pushing the rocket and the walls push against the exhaust forcing it out the nozzle. The is a hole at the bottom meaning no force is imparted down. Therefore net force is up.

No. A force was imparted onto the exhaust to force it out of the nozzle, so the exhaust imparted a force equal and opposite on the rocket.

Quote from: TexasH on October 01, 2015, 02:19:11 PM

Is that a yes or no?

That was a LOL!!!

At your stupid questions.

Cos you asked two btw, both of which were irrelevant.

In summation: Learn to read.

Then buy a book on gas laws.

Then realise space travel is fake.

Then get a life.

Oh, & Yendor; you make a good point; but I've been here already with these bozos, so don't expect a logical answer... Ever.

If you can't be bothered to answer simple questions, then why respond in the first place?  Where did I imply that I didn't know how many questions I asked?  I'm not sure why you felt the need to point that out.  Why would I take educational advice from someone that can't form proper sentences or construct paragraphs?  I have plenty of books on gas laws.  I don't quite understand your constant use of LULZ and LOL.   Isn't that how a 15 year old girl speaks in a text message?

Quote from: Papa Legba on October 01, 2015, 01:32:45 PM

Oh, & Free/Joules Expansion is NOT exclusively limited to a closed system; that's a big fat LIE right there, so knock it off, okay?

Not a lie.  It is ALWAYS described in a closed system. 

Yes a Lie.

Stop it.

Place small can of pressurised gas (rocket) into Infinite vacuum (space); then open can & the gas will EXPAND FREELY into zero pressure of vacuum, meeting zero resistance, doing zero work: FACT.

Because you cannot Push on Nothing.

Deny the above & you deny Newton, Joules & Thomson, not me.

Remember that.

Same goes for you, TexasH.

Who has a shrill, needy, nagging tone & tendency to insist I answer stupid & irrelevant 'yes or no' questions that is strangely reminiscent of bijane btw...

LULZ!!!

Quote from: frenat on October 01, 2015, 02:59:10 PM

Quote from: Papa Legba on October 01, 2015, 01:32:45 PM

Oh, & Free/Joules Expansion is NOT exclusively limited to a closed system; that's a big fat LIE right there, so knock it off, okay?

Not a lie.  It is ALWAYS described in a closed system. 

Yes a Lie.

Stop it.

Place small can of pressurised gas (rocket) into Infinite vacuum (space); then open can & the gas will EXPAND FREELY into zero pressure of vacuum, meeting zero resistance, doing zero work: FACT.

Because you cannot Push on Nothing.

Deny the above & you deny Newton, Joules & Thomson, not me.

Remember that.

Same goes for you, TexasH.

Who has a shrill, needy, nagging tone & tendency to insist I answer stupid & irrelevant 'yes or no' questions that is strangely reminiscent of bijane btw...

LULZ!!!

Which is why rockets don't push on nothing. They push on their exhaust and their exhaust pushes back.  Newton's third law. 

Quote from: frenat on October 01, 2015, 02:59:10 PM

Quote from: Papa Legba on October 01, 2015, 01:32:45 PM

Oh, & Free/Joules Expansion is NOT exclusively limited to a closed system; that's a big fat LIE right there, so knock it off, okay?

Not a lie.  It is ALWAYS described in a closed system. 

Yes a Lie.

Stop it.

Place small can of pressurised gas (rocket) into Infinite vacuum (space); then open can & the gas will EXPAND FREELY into zero pressure of vacuum, meeting zero resistance, doing zero work: FACT.

Oh, you've tried it?  No?  What changes the direction and velocity of the gas molecules that were moving away from the opening when you open it?  A vacuum can't do it.  A vacuum is nothing and can do no work.  To change the velocity it takes work.

Because you cannot Push on Nothing.

Good thing that isn't what happens then.

Deny the above & you deny Newton, Joules & Thomson, not me.

Newton would agree with conservation of momentum.  Joule and thomson ALWAYS described free expansion in a closed system.

They push on their exhaust and their exhaust pushes back.

LULZ!!!

I love it when you satanic sci-fi cultists get backed into a corner & end up saying things like this...

You simply cannot come up with a coherent model for rocket thrust, can you?

That's because you ignore Joules & Thomson & try to create a mechanical model for what is clearly a matter of pressure gradients...

In other words, you can only 'prove' that a rocket works in a vacuum by ignoring the fact that it is in a vacuum.

Cognitive dissonance much?

Oh, & frenat; stop lying; it's getting disgusting now.

Quote from: sokarul on October 01, 2015, 05:02:55 PM

They push on their exhaust and their exhaust pushes back.

LULZ!!!

I love it when you satanic sci-fi cultists get backed into a corner & end up saying things like this...

You simply cannot come up with a coherent model for rocket thrust, can you?

That's because you ignore Joules & Thomson & try to create a mechanical model for what is clearly a matter of pressure gradients...

In other words, you can only 'prove' that a rocket works in a vacuum by ignoring the fact that it is in a vacuum.

Cognitive dissonance much?

Oh, & frenat; stop lying; it's getting disgusting now.

I'm not lying.  If you could prove free expansion was described in an open system you would have by now.  Free expansion is also described as an adiabatic process.  An adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings.  A rocket is most certainly NOT an adiabatic process.

And you haven't answered the question.
What changes the direction and velocity of the gas molecules that were moving away from the opening when you open it?  A vacuum can't do it.  A vacuum is nothing and can do no work.  To change the velocity it takes work.

Quote from: sokarul on October 01, 2015, 05:02:55 PM

They push on their exhaust and their exhaust pushes back.

LULZ!!!

I love it when you satanic sci-fi cultists get backed into a corner & end up saying things like this...

You simply cannot come up with a coherent model for rocket thrust, can you?

That's because you ignore Joules & Thomson & try to create a mechanical model for what is clearly a matter of pressure gradients...

In other words, you can only 'prove' that a rocket works in a vacuum by ignoring the fact that it is in a vacuum.

Cognitive dissonance much?

Oh, & frenat; stop lying; it's getting disgusting now.

It's just like when the guy pushes on the medicine ball and it pushes back.
#" class="bbc_link" target="_blank" rel="noopener noreferrer">! No longer available

Try harder.

Back to the trusty old man on skateboard!

Remove the ball from the experiment & what would happen when the man pushes his arms out?

Nothing!

There: fixed it for you.

Back to the trusty old man on skateboard!

Remove the ball from the experiment & what would happen when the man pushes his arms out?

Nothing!

There: fixed it for you.

How is that supposed to prove your point? He pushes off the ball so of course he won't move if you remove the ball.
Are you drunk?

Quote from: frenat on October 01, 2015, 02:59:10 PM

Quote from: Papa Legba on October 01, 2015, 01:32:45 PM

Oh, & Free/Joules Expansion is NOT exclusively limited to a closed system; that's a big fat LIE right there, so knock it off, okay?

Not a lie.  It is ALWAYS described in a closed system. 

Yes a Lie.

Stop it.

Place small can of pressurised gas (rocket) into Infinite vacuum (space); then open can & the gas will EXPAND FREELY into zero pressure of vacuum, meeting zero resistance, doing zero work: FACT.

Because you cannot Push on Nothing.

Deny the above & you deny Newton, Joules & Thomson, not me.

Remember that.

Same goes for you, TexasH.

Who has a shrill, needy, nagging tone & tendency to insist I answer stupid & irrelevant 'yes or no' questions that is strangely reminiscent of bijane btw...

LULZ!!!

How much thrust does a Boeing 747 lose as it climbs from sea level to a cruising altitude of 35,000 feet?

He pushes off the ball so of course he won't move if you remove the ball.

Exactly! Now you're getting there...

Learning to think at last.

Of course, a more accurate way of factoring the vacuum into your model would be to reduce the mass of the ball to Zero, thus reproducing the Zero pressure found therein.

But that may be a little confusing for you, so let's stick with just removing it altogether for now...

Baby steps, eh?

Still, you've got the basic idea: you can't push off Nothing.

TexasH: irrelevant; off-topic; goodbye!

Back to the trusty old man on skateboard!

Remove the ball from the experiment & what would happen when the man pushes his arms out?

Nothing!

There: fixed it for you.

It seems you had trouble understanding my last post (too complicated for you?) so here is another post that hopefully you can understand.


Let's look at 3 different systems, and label each component in those systems, to see if they have any similarities.

Firstly, let's look at the cannon and cannonball system.  Let's label the cannon as Object A and the cannonball as Object B. The action of expelling the cannonball out of the cannon, causes the cannon to move in the opposite direction to that of the cannonball. This is a simple 'action' and 'reaction' scenario, and is obviously consistent with Newton's laws concerning conservation of momentum.

Secondly, let's look at the man and the medicine ball system (the system is sitting on a skateboard, the only purpose of which is to simulate a frictionless surface).  Let's label the man as Object A and the medicine ball as Object B. The action of throwing the medicine ball, causes the man to move in the opposite direction to that of the medicine ball. This is a simple 'action' and 'reaction' scenario, and is obviously consistent with Newton's laws concerning conservation of momentum.

Thirdly, let's look at the rocket and the fuel system. Let's label the rocket as Object A and the fuel as Object B. The action of throwing the fuel (burnt exhaust gases) out of the rocket, causes the rocket to move in the opposite direction to that of the fuel (burnt exhaust gases). This is a simple 'action' and 'reaction' scenario, and is obviously consistent with Newton's laws concerning conservation of momentum.


So as we can see from the 3 separate examples above, the act of 'throwing' mass (Object B) in one direction out of the system, causes Object A to be forced in the opposite direction.

At this point I thought it would be beneficial to actually look at the weights of Object B (the thrown objects) in the 3 examples above, ie the cannonball, the medicine ball and the rocket fuel.

A cannonball typically weighs 12 kilograms.
A medicine ball typically weighs 8 kilograms.
For the weight of rocket fuel, let's look at the 1st stage of the Apollo Saturn V rocket. It burnt a staggering 15 tons of fuel EVERY SECOND, and virtually ALL OF THIS MASS was expelled out of its engine nozzles at over 4 kilometres per second (= a HUGE amount of momentum).

Conclusion -

The 3 separate systems that we have looked at above, ALL have the same principles involved concerning the conservation of momentum.

Each of the 3 systems has an Object B (mass) which is being forced in one direction, which is causing Object A to be forced in the opposite direction.


If there is anything that you don't agree with, I would welcome your explanation as to specifically which aspect is troubling you?

I realise that it's your opinion that rockets cannot operate in the vacuum of space, but at this stage of the discussion could you please just deal with rocket propulsion within the atmosphere.

 I am just trying to ascertain your stance on how a rocket actually propels whilst still in the earth's atmosphere, and specifically whether you think a rocket propels due to 'pushing' off the atmosphere, or whether a rocket propels due to Newton's conservation of momentum laws?  Thanks in advance.

Thirdly, let's look at the rocket and the fuel system. Let's label the rocket as Object A and the fuel as Object B.

Aaaaand FAIL!

This is not the same system as in your previous examples; in the cannon example you had object A & object B with the propellant (i.e. gunpowder) between them. In your man on skateboard you had object A & object B with the propellant (i.e. the man's arm) between them.

But in your rocket example you ONLY have object A & the propellant (i.e. the fuel).

No object B, see?

Thus, you have removed the necessary recoil object required to produce motion.

But we know a rocket DOES produce motion, don't we?

Ergo, some other mass MUST be taking the place of object B.

& the ONLY possibility for that other mass is the Atmosphere.

Ergo, NO atmosphere, NO motion; rockets CANNOT function in a vacuum.

Q.E.D.

Object B is the exhaust. It has mass and therefore acts to transfer momentum.

Now I know you're just trolling.

Read my last post; the 1st two examples have object A & object B, with the propellant, P, sitting between them.

But in the case of the rocket, we only have object A & the propellant, P.

There is clearly no object B.

Ergo, no motion can be produced.

But, as rockets do produce motion, another mass must replace object B.

The only possibility for that mass is the atmosphere.

Ergo, rockets push on the atmosphere.

This is VERY simple stuff, mainframes; a child could see it; yet you can not.

Conclusion: Sucks to be you.

Quote from: chtwrone on October 02, 2015, 01:05:37 AM

Thirdly, let's look at the rocket and the fuel system. Let's label the rocket as Object A and the fuel as Object B.

Aaaaand FAIL!

This is not the same system as in your previous examples; in the cannon example you had object A & object B with the propellant (i.e. gunpowder) between them. In your man on skateboard you had object A & object B with the propellant (i.e. the man's arm) between them.

But in your rocket example you ONLY have object A & the propellant (i.e. the fuel).

No object B, see?

Thus, you have removed the necessary recoil object required to produce motion.

But we know a rocket DOES produce motion, don't we?

Ergo, some other mass MUST be taking the place of object B.

& the ONLY possibility for that other mass is the Atmosphere.

Ergo, NO atmosphere, NO motion; rockets CANNOT function in a vacuum.

Q.E.D.

Sorry, but the fail is YOU.

It seems your reading skills are VERY poor, as I most certainly DID label Object B in the rocket example, and here is the relevant quote from my post -

'Thirdly, let's look at the rocket and the fuel system. Let's label the rocket as Object A and the fuel as Object B. The action of throwing the fuel (burnt exhaust gases) out of the rocket, causes the rocket to move in the opposite direction to that of the fuel (burnt exhaust gases). This is a simple 'action' and 'reaction' scenario, and is obviously consistent with Newton's laws concerning conservation of momentum.'

The FUEL is 'the necessary recoil object required to produce motion'. 

You do realise that the fuel when expelled out of the rocket at great speed, has considerable mass (15 tons per second in the Apollo Saturn V rocket), and therefore HUGE momentum?  The mass of the fuel does not magically disappear when it's ignited and expelled out of the rocket. Did you not know this?

This is why the 3 examples I gave in my previous post, are using exactly the same conservation of momentum laws to give cause to the motion of the cannon, the man, and the rocket, as they are ALL forcing mass in one direction, ie, the cannonball, the medicine ball, and the burnt fuel.

It seems to me, that you're having trouble realising that the burnt fuel being 'thrown' out of the rocket in one direction, is causing the rocket to be propelled in the opposite direction?  This is EXACTLY the same reason why a cannon moves in one direction because of the weight of the cannonball being expelled in the opposite direction.

EXACTLY the same conservation of momentum laws are applicable in these examples.

The FUEL is 'the necessary recoil object required to produce motion'. 

LULZ!!!

Trolls say the funniest things!

Poor chtwrone; cannot count to three...

Sucks to be him.

If you could prove free expansion was described in an open system you would have by now.  Free expansion is also described as an adiabatic process.  An adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings.  A rocket is most certainly NOT an adiabatic process.

*Sigh!*

For a demonstration of adiabatic free expansion of a gas, the gas is contained in an insulated container and then allowed to expand into a vacuum. Because there is no external pressure for the gas to expand against, the work done by or on the system is Zero.

What is a rocket in space if not an insulated container full of gas?

What is space if not a vacuum?

Why are you so reluctant to acknowledge the truth of the gas laws of Joules & Thomson?

Last chance...

Quote from: frenat on October 01, 2015, 05:30:49 PM

If you could prove free expansion was described in an open system you would have by now.  Free expansion is also described as an adiabatic process.  An adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings.  A rocket is most certainly NOT an adiabatic process.

*Sigh!*

For a demonstration of adiabatic free expansion of a gas, the gas is contained in an insulated container and then allowed to expand into a vacuum. Because there is no external pressure for the gas to expand against, the work done by or on the system is Zero.

What is a rocket in space if not an insulated container full of gas?

What is space if not a vacuum?

Why are you so reluctant to acknowledge the truth of the gas laws of Joules & Thomson?

Last chance...

A rocket exhausting into space is NOT an adiabatic process.  Again, an adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings.  That is why free expansion is always described as a closed system.  A rocket is most definitely transferring heat and matter with its surroundings.  Joules and Thomson knew that which is why they always described it as a closed system.  If it is an open, non-adiabatic system then free expansion does not apply.  That is the truth of the gas laws of Joules & Thomson.

And you still haven't answered the question.
What changes the direction and velocity of the gas molecules that were moving away from the opening when you open it?  A vacuum can't do it.  A vacuum is nothing and can do no work.  To change the velocity it takes work.

TexasH: irrelevant; off-topic; goodbye!

If you think that question was irrelevant and off-topic, you don't even understand your own argument.  Atmospheric pressure at 35,000 feet is 3.46 psi,  compared to 14.7 at sea level.  If it was pushing off the atmosphere for thrust, it would lose a lot of thrust.  Hell, based on your theory, the U2 wouldn't have worked at 70,000 feet.

Frenat: stop twisting words to suit your own delusions.

I just described how adiabatic free expansion is experimentally proven; argue with the proof, not the meaning of individual phrases.

A rocket in space is a very small container of pressurised gas in a very large Zero-pressure environment.

When opened to that Zero-pressure environment, the gas will expand, freely, doing no work, until it encounters resistance.

It is simple stuff, no matter how hard you try to obscure that Fact.

TexasH: Hi bijane! Still as needy, irrelevant & off-topic as ever I see.

Frenat: stop twisting words to suit your own delusions.

I just described how adiabatic free expansion is experimentally proven; argue with the proof, not the meaning of individual phrases.

A rocket in space is a very small container of pressurised gas in a very large Zero-pressure environment.

When opened to that Zero-pressure environment, the gas will expand, freely, doing no work, until it encounters resistance.

It is simple stuff, no matter how hard you try to obscure that Fact.

Adiabatic free expansion is proven.  A rocket is NOT adiabatic.  I have twisted nothing.

TexasH: Hi bijane! Still as needy, irrelevant & off-topic as ever I see.

What does that even mean?  Are you making up words now?

Do you even know what the topic is?  Is the topic not how rockets achieve thrust in space?  Do you think that as the pressure drops, there is a magical cutoff where thrust drops to zero?  Based on your theory how rockets work, the thrust would be directly affected by the number of particles surrounding the rocket, correct?

Quote from: sokarul on October 01, 2015, 06:12:02 PM

He pushes off the ball so of course he won't move if you remove the ball.

Exactly! Now you're getting there...

Learning to think at last.

Of course, a more accurate way of factoring the vacuum into your model would be to reduce the mass of the ball to Zero, thus reproducing the Zero pressure found therein.

But that may be a little confusing for you, so let's stick with just removing it altogether for now...

Baby steps, eh?

Still, you've got the basic idea: you can't push off Nothing.

TexasH: irrelevant; off-topic; goodbye!

Mass is independent of air pressure. Why would we set it to zero?

A rocket in space is a very small container of pressurised gas in a very large Zero-pressure environment.

When opened to that Zero-pressure environment, the gas will expand, freely, doing no work, until it encounters resistance.

How does this (free expansion):


resemble this:


Also, for your amusement:
http://physics.stackexchange.com/questions/91789/rocket-thrust-gas-free-expansion-of-gas

Do you think that as the pressure drops, there is a magical cutoff where thrust drops to zero? 

Bingo!

The penny finally drops...

Well done, not-bijane-even-though-you-sound-exactly-like-her!

I have twisted nothing.

You're twisting both my melon & your knickers.

Now; Troll on, vieux chou-fleur!

& oh, look! Even as I type this, both sock-arul & markjo turn up to open the shitpost flood gates...

Gotta make me look as out-numbered as possible, ain't you?

LOL!!!

No, markjo; they DON'T resemble each other, do they?

Clever boy!

& a link too; how unlike you to just provide links instead of explaining things in your own words...

LULZ!!!

& p.s: in your silly nasa drawing it says force=mass x velocity; I thought it was force=mass x acceleration?

Have NASA informed Newton of their decision to change his 2nd Law?

BONUS LULZ!!!

and no response to the FACT that a rocket is not adiabatic.  Typical.

Quote from: TexasH on October 02, 2015, 05:50:18 AM

Do you think that as the pressure drops, there is a magical cutoff where thrust drops to zero? 

Bingo!

The penny finally drops...

Well done, not-bijane-even-though-you-sound-exactly-like-her!

So what is that magical cutoff?  Are you saying as long as there is one gas molecule, it will have full thrust, but remove that one molecule, it will have zero thrust?  How does that make any kind of sense?  You realize that space isn't a perfect vacuum, right? 

Ah, great, you think I sound like a woman.  Well, I think you type like a 15-year-old girl at times, so I guess we are all good.

I have no idea what you two are on about now...

Get some fresh air.

Force = mass x velocity...

LMFAO!!!