The ISS is a Gulfstream jet.

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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #660 on: March 22, 2016, 04:22:57 AM »
You need to stop thinking a rocket exhaust pushes off vacuum.

I don't, you retarded lying disinfo-thing.

Plus, a rocket is an Open System and Conservation of Momentum only applies to Closed Systems.

Strawman Rejected.

It is a simple matter of applying Newton's 3rd Law.

A Force is defined as a push or pull on an object as a result of its interaction with another object.

So, if the Action of the exhaust of a rocket is a Push on something at 5,000 mph then the resulting Reaction can never exceed that speed.

Never.

And you will find no example in nature, or any simple experiment, that contradicts what I say.

I have owned you on this subject twice already; your next move will be to start banging on about nebulous 'forces' like a Star Wars nerd, playing with numbers, trying to confuse the terms velocity & acceleration, as well as citing Inertial Frames of Reference & other such junk-science.

Well with the exception that you're wrong on the math, wrong on the experiments and wrong again on the demonstrations.

3 for 3 not bad.
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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #661 on: March 22, 2016, 04:38:08 AM »
Mistaking Words for Reality again?

You're good at that.

It's the only way you can justify 'shpayze-shippz', that's why.

Now; please show me the experiments you claim to have provided which demonstrate the oxymoronic notion that an object being pushed can somehow exceed the speed at which it is being pushed.

It may involve some kind of free-energy device?

Or perhaps gravity-assistance?

Or the cunning use of smoke & mirrors?

Anything is possible when teh Clown Derfers do physics!
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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #662 on: March 22, 2016, 05:05:39 AM »
Mistaking Words for Reality again?

You're good at that.

It's the only way you can justify 'shpayze-shippz', that's why.

Now; please show me the experiments you claim to have provided which demonstrate the oxymoronic notion that an object being pushed can somehow exceed the speed at which it is being pushed.

It may involve some kind of free-energy device?

Or perhaps gravity-assistance?

Or the cunning use of smoke & mirrors?

Anything is possible when teh Clown Derfers do physics!

Papa Short Bus, they have been posted on several threads in several different parts of this forum. Being that you are (self proclaimed) well read on the goings one of these forums you should know where to find them. If not, the search function in the upper right is quite useful too.

You, Mr. Short Bus, on the other hand have not once disproved, with math, experimentation nor demonstration the maths presented other than just saying they are wrong.  That is behavior one expects of  young child. I was hoping for more of an adult discussion.
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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #663 on: March 22, 2016, 05:14:40 AM »
So; you have no experiments or evidence.

Just pompous boasting & puffery.

Right.

Plus, teh silly fake ISS is still a Gulfstream Jet with a spotlight stuck to it.

The Emperor has ALL his New Clothes on today!
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Re: The ISS is a Gulfstream jet.
« Reply #664 on: March 22, 2016, 05:54:01 AM »
Evidence???

At cruise a 747 is doing what 500-550mph?

The four engines are producing exhaust gas and expelling it about 200mph.

A unit of thrust gives a given acceleration to a given mass. It doesn't matter how fast the exhaust is as long as it is providing enough thrust to give enough force to continue to accelerate the rocket.

Feel like an idiot now?

Gonna cry?

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markjo

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Re: The ISS is a Gulfstream jet.
« Reply #665 on: March 22, 2016, 06:26:48 AM »
No jet or rocket can exceed the maximum velocity of its own exhaust.
Yes, just like no sail boat can exceed the velocity of the wind that's pushing it.
http://www.sail-world.com/USA/how-does-a-sailboat-go-faster-than-the-wind?/54408
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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #666 on: March 22, 2016, 07:46:21 AM »
Feel like an idiot now?

LOL!!!

No.

If it doesn't matter how fast the exhaust is then why does every rocket engineer do all they can to maximise it?

You know, with De Laval nozzles & such?

Indeed, why even ignite the fuel?

And why do you keep referring to 'acceleration'?

An object can only accelerate UP TO its maximum velocity; thereafter it can accelerate no more.

And the maximum velocity of a rocket is set by the maximum velocity of its exhaust.

This is fundamental.

As usual, you have just spammed out a lot of science-y sounding jargon with no practical experiments or genuine evidence.

Also, the exhaust velocity of a turbofan engine exceeds 200 mph by a considerable margin...

In fact the effective exhaust velocity is over 6,000 mph.

But, as you have a history of Lying this is only to be expected.

Markjo; if you actually read the links you spam (and you deliberately found a very dumb one too) you would find it actually says that no, a sailboat cannot exceed the speed it is being pushed at.

Nothing can; Newton is very specific on this.

So; another Lie to add to your tally, too.

Feel like Idiots now?
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Re: The ISS is a Gulfstream jet.
« Reply #667 on: March 22, 2016, 08:27:00 AM »
Because you know. Higher velocity equates to a higher force. Thus a higher thrust.

why ignite the fuel? If you need that answering you're a retard.

200mph yeah no. Letting you know what it's like to read half the shit that flies out your mouth. Ask yourself WHY a jet engine cannot fly faster than its exhaust. Then proceed to compare why a rocket engine doesn't intake air.

Your missing the point here. A rocket doesn't push of anything but the rocket. It doesn't intake air. It has no external drag force in a vacuum. Well in fact nothing but gravity until it leaves the earths field.

So it's pushing 1000kg/s of thrust to produce an acceleration increase of 10m/s. At 1000m/s let's say that is the exhaust speed.

So the rocket reaches 1000m/s. What variable tells it to stop producing thrust?
« Last Edit: March 22, 2016, 08:45:53 AM by TylerJRB »

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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #668 on: March 22, 2016, 09:04:12 AM »
LOL!!!

Having a little disinfo-tizzy cos you got caught Lying about the exhaust velocity of a jumbo jet being lower than its cruising velocity, are you?

What a Loser.

Fact is that turbofan engines are VASTLY more efficient than the shitty toy rockets you worship...

So if a turbofan cannot exceed the velocity of its exhaust, no way a rocket can do it.

Grow up; learn to respect Newton; stop Lying.

Thanks please!
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sokarul

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Re: The ISS is a Gulfstream jet.
« Reply #669 on: March 22, 2016, 09:17:20 AM »
Feel like an idiot now?

LOL!!!

No.

If it doesn't matter how fast the exhaust is then why does every rocket engineer do all they can to maximise it?

You know, with De Laval nozzles & such?

Indeed, why even ignite the fuel?

And why do you keep referring to 'acceleration'?

An object can only accelerate UP TO its maximum velocity; thereafter it can accelerate no more.

And the maximum velocity of a rocket is set by the maximum velocity of its exhaust.

This is fundamental.

As usual, you have just spammed out a lot of science-y sounding jargon with no practical experiments or genuine evidence.

Also, the exhaust velocity of a turbofan engine exceeds 200 mph by a considerable margin...

In fact the effective exhaust velocity is over 6,000 mph.

But, as you have a history of Lying this is only to be expected.

Markjo; if you actually read the links you spam (and you deliberately found a very dumb one too) you would find it actually says that no, a sailboat cannot exceed the speed it is being pushed at.

Nothing can; Newton is very specific on this.

So; another Lie to add to your tally, too.

Feel like Idiots now?
Lol

The faster the exhaust velocity the greater the force created.

Lol


Apply a constant force to an object and let me know when it will stop accelerating.

Lol

Maximum velocity.


Lol

Retard


Lol
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markjo

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Re: The ISS is a Gulfstream jet.
« Reply #670 on: March 22, 2016, 10:42:00 AM »
Fact is that turbofan engines are VASTLY more efficient than the shitty toy rockets you worship...

So if a turbofan cannot exceed the velocity of its exhaust, no way a rocket can do it.
Except that turbofans and rocket engines don't work exactly the same way.  A key differences is that a rocket engine does get the vast majority of its reaction mass from the atmosphere like a turbofan does. 

Essentially, the mass that a turbofan engine takes in is the same as the mass that it ejects out the back (give or take a bit for the burned fuel), so you're more or less right that a jet engine can't really go much faster than its exhaust (remember that effective exhaust velocity is not exactly the same as actual exhaust velocity).

However, rocket engines are different because they carry all of their reaction mass, therefore the initial and exhaust velocities of the reaction mass are measured relative to the rocket's frame of reference, not that of the atmosphere or free space.
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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #671 on: March 22, 2016, 10:59:03 AM »
So; you have no experiments or evidence.

Just pompous boasting & puffery.

Right.

Plus, teh silly fake ISS is still a Gulfstream Jet with a spotlight stuck to it.

The Emperor has ALL his New Clothes on today!

Dear, dear, Mr. Papa Short Bus, print this out and take it to you mommy or better yet a responsible grown up and have them read this to you along with the previous posts, to help you understand that stomping your foot and pouting is not a proper way to prove you point.

Fuel and oxidizer are pumped into a chamber that is wide open on one end. This mixture is ignited causing it to expand at and explosive rate. One liter of LOX (liquid Ox) is more than 860.26 liters of gas.  One liter of Liquid Hydrogen is 849.22 liters of gas.

Burning this mixture creates a mass of water and unburned gasses which expands the mass and is ejected out the open end of the chamber with a force measured from a few foot pound to many tons, depending on the size and design of the engine. The fuel/water mass is pushing against the mass of the rocket not against a vacuum.

Simple middle school math and science and easy to prove in a vacuum chamber.

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Then there is this proofs which of course you will AGAIN ignore because you cannot disprove it.
A rocket engine is a device in which propellants are burned in a combustion chamber and the resulting high pressure gases are expanded through a specially shaped nozzle to produce thrust. The function of the nozzle is to convert the chemical-thermal energy generated in the combustion chamber into kinetic energy. The nozzle converts the slow moving, high pressure, high temperature gas in the combustion chamber into high velocity gas of lower pressure and temperature. Gas velocities from 2 to 4.5 kilometers per second can be obtained in rocket nozzles. The nozzles which perform this feat are called DeLaval nozzles (after the inventor) and consist of a convergent and divergent section. The minimum flow area between the convergent and divergent section is called the nozzle throat. The flow area at the end of the divergent section is called the nozzle exit area.

Hot exhaust gases expand in the diverging section of the nozzle. The pressure of these gases will decrease as energy is used to accelerate the gas to high velocity. The nozzle is usually made long enough (or the exit area great enough) such that the pressure in the combustion chamber is reduced at the nozzle exit to the pressure existing outside the nozzle. It is under this condition that thrust is maximum and the nozzle is said to be adapted, also called optimum or correct expansion. To understand this we must examine the basic thrust equation:

   F = q × Ve + (Pe - Pa) × Ae

   where F = Thrust
         q = Propellant mass flow rate
         Ve = Velocity of exhaust gases
         Pe = Pressure at nozzle exit
         Pa = Ambient pressure
         Ae = Area of nozzle exit
The product qVe is called the momentum, or velocity, thrust and the product (Pe-Pa)Ae is called the pressure thrust. As we have seen, Ve and Pe are inversely proportional, that is, as one increases the other decreases. If a nozzle is under-extended we have Pe>Pa and Ve is small. For an over-extended nozzle we have Pe<Pa and Ve is large. Thus, momentum thrust and pressure thrust are inversely proportional and, as we shall see, maximum thrust occurs when Pe=Pa.
Let us now consider an example. Assume we have a rocket engine equipped with an extendible nozzle. The engine is test fired in an environment with a constant ambient pressure. During the burn, the nozzle is extended from its fully retracted position to its fully extended position. At some point between fully retracted and fully extended Pe=Pa (see figure below).


As we extend the nozzle, the momentum thrust increases as Ve increases. At the same time the pressure thrust decreases as Pe decreases. The increase in momentum thrust is greater than the decrease in pressure thrust, thus the total thrust of the engine increases as we approach the condition Pe=Pa. As we continue to extend to nozzle the situation changes slightly. Now the pressure thrust changes in magnitude more rapidly than the momentum thrust, thus the total thrust begins to decrease.

Let's now apply some numbers to our example and run through the calculations to prove that this is true. Assume our rocket engine operates under the following conditions:

   q = Propellant mass flow rate = 100 kg/s         
   k = Specific heat ratio = 1.20           
   M = Exhaust gas molecular weight = 24             
   Tc = Combustion chamber temperature = 3600 K       
   Pc = Combustion chamber pressure = 5 MPa         
   Pa = Ambient pressure = 0.05 MPa       
If the nozzle is properly adapted to the operating conditions we have Pe=Pa, or Pe=0.05 MPa.

The gas pressure and temperature at the nozzle throat is less than in the combustion chamber due to the loss of thermal energy in accelerating the gas to the local speed of sound at the throat. Therefore, we calculate the pressure and temperature at the nozzle throat,

   Pt = Pc × [1 + (k - 1) / 2]-k/(k-1)
   Pt = 5 × [1 + (1.20 - 1) / 2]-1.20/(1.20-1)
   Pt = 2.82 MPa = 2.82x106 N/m2

   Tt = Tc × [1 / (1 + (k - 1) / 2)]
   Tt = 3,600 × [1 / (1 + (1.20 - 1) / 2)]
   Tt = 3,273 K
The area at the nozzle throat is given by

   At = (q / Pt) × SQRT[ (R' × Tt) / (M × k) ]
   At = (100 / 2.82x106) × SQRT[ (8,314 × 3,273) / (24 × 1.20) ]
   At = 0.0345 m2
The hot gases must now be expanded in the diverging section of the nozzle to obtain maximum thrust. The Mach number at the nozzle exit is given by

   Nm2 = (2 / (k - 1)) × [(Pc / Pa)(k-1)/k - 1]
   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.05)(1.20-1)/1.20 - 1]
   Nm2 = 11.54
   Nm = (11.54)1/2 = 3.40
The nozzle exit area corresponding to the exit Mach number is given by

   Ae = (At / Nm) × [(1 + (k - 1) / 2 × Nm2)/((k + 1) / 2)](k+1)/(2(k-1))
   Ae = (0.0345 / 3.40) × [(1 + (1.20 - 1) / 2 × 11.54)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.409 m2
The velocity of the exhaust gases at the nozzle exit is given by

   Ve = SQRT[ (2 × k / (k - 1)) × (R' × Tc / M) × (1 - (Pe / Pc)(k-1)/k) ]
   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.05 / 5)(1.20-1)/1.20) ]
   Ve = 2,832 m/s
Finally, we calculate the thrust,

   F = q × Ve + (Pe - Pa) × Ae
   F = 100 × 2,832 + (0.05x106 - 0.05x106) × 0.409
   F = 283,200 N


Let's now consider what happens when the nozzle is under-extended, that is Pe>Pa. If we assume Pe=Pa × 2, we have

   Pe = 0.05 × 2 = 0.10 MPa   
   
   At = 0.0345 m2

   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.10)(1.20-1)/1.20 - 1]
   Nm2 = 9.19
   Nm = (9.19)1/2 = 3.03

   Ae = (0.0345 / 3.03) × [(1 + (1.20 - 1) / 2 × 9.19)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.243 m2

   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.10 / 5)(1.20-1)/1.20) ]
   Ve = 2,677 m/s

   F = 100 × 2,677 + (0.10x106 - 0.05x106) × 0.243
   F = 279,850 N


Now we consider the over-extended condition, that is Pe<Pa. If we assume Pe=Pa / 2, we have

   Pe = 0.05 / 2 = 0.025 MPa   
   
   At = 0.0345 m2

   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.025)(1.20-1)/1.20 - 1]
   Nm2 = 14.18
   Nm = (14.18)1/2 = 3.77

   Ae = (0.0345 / 3.77) × [(1 + (1.20 - 1) / 2 × 14.18)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.696 m2

   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.025 / 5)(1.20-1)/1.20) ]
   Ve = 2,963 m/s

   F = 100 × 2,963 + (0.025x106 - 0.05x106) × 0.696
   F = 278,900 N


We see that both the under-extended and over-extended nozzles produce thrusts less than that produced when the condition Pe=Pa is satisfied. When we plot a graph of total thrust versus the ratio Pa/Pe we obtain the following:

As can be easily seen, thrust is maximum when Pa/Pe=1, or when Pe=Pa.
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Re: The ISS is a Gulfstream jet.
« Reply #672 on: March 22, 2016, 11:30:12 AM »
Finally a post with full math explanation and equations. Way to elegantly shut off people.

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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #673 on: March 22, 2016, 12:34:23 PM »
LOL!!!

None of that had anything to do with what I'm talking about.

It's just copy-pasta gibberish that none of you actually understand...

You even had to activate the Goebbels sock-puppet ID for a bit of creepy psychic driving duty.

And you only do that when you're really desperate.

Anyhoo; I'll just quickly destroy it before moving on...

The fuel/water mass is pushing against the mass of the rocket not against a vacuum.

How can it push against a vacuum? A vacuum is nothing.

I never made such a claim.

Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

Especially in an Open System such as a rocket.

Well, that's what the Laws of Physics say, anyway.

Now; back to our impossible 17,500 mph ISS lol-tube full of gaylords.

I am truly sorry that you cannot understand the meaning of the words 'equal & opposite'.

Or that a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

Perhaps if you used 28,000 sock-ID's to tell me it isn't someone will believe you?

That someone will not be me...

But it may represent a tiny win in your War against Truth.
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Heiwa

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Re: The ISS is a Gulfstream jet.
« Reply #674 on: March 22, 2016, 12:36:53 PM »
Finally a post with full math explanation and equations. Way to elegantly shut off people.
Not really. You must also know where you are (A) and where you want to go (B) and the trajectory between A and B and how to apply forces to do it. Not easy.

However the ISS seems to be a simple artificial satellite in regular orbit around Earth that can be seen, when it passes above us from West to East lit up by the setting Sun since years.

It has no means of propulsion. It just orbits Earth. I have taken photos of it many times. It looks like a silver balloon (a round bright dot!) and why not? It is easy to send up such a satellite into orbit and expand it in vacuum space and then allow it to orbit.

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palmerito0

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Re: The ISS is a Gulfstream jet.
« Reply #675 on: March 22, 2016, 12:48:18 PM »
Finally a post with full math explanation and equations. Way to elegantly shut off people.
Not really. You must also know where you are (A) and where you want to go (B) and the trajectory between A and B and how to apply forces to do it. Not easy.

However the ISS seems to be a simple artificial satellite in regular orbit around Earth that can be seen, when it passes above us from West to East lit up by the setting Sun since years.

It has no means of propulsion. It just orbits Earth. I have taken photos of it many times. It looks like a silver balloon (a round bright dot!) and why not? It is easy to send up such a satellite into orbit and expand it in vacuum space and then allow it to orbit.

The ISS does need propulsion to maintain its orbit, it slows down very slightly due to atmospheric drag.
Heiwa on the impossibility of space travel:

There are no toilets up there and sex is also a problem, just to mention a few difficulties.

WHEEEEEEEEEEE

Re: The ISS is a Gulfstream jet.
« Reply #676 on: March 22, 2016, 01:44:58 PM »
Firstly
Quote
But pressure is impossible to create in an Infinite vacuum...

The earth is surrounded by an infinite vacuum, is it impossible for the earth to have an atmosphere creating pressure.

Secondly
Quote
Or that a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.
So mph measures force now? Lol.
« Last Edit: March 22, 2016, 03:50:51 PM by Empirical »

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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #677 on: March 22, 2016, 01:45:33 PM »
Finally a post with full math explanation and equations. Way to elegantly shut off people.

I was responding to Papa Short Bus Legba. He SAID he wanted to know. And of course he ignored it. He can't handle facts and truth.

He cannot handle being challenged, it is too much for him.
Stupidity cannot be cured with money, or through education, or by legislation. Stupidity is not a sin, the victim can't help being stupid. But stupidity is the only universal capital crime...

Re: The ISS is a Gulfstream jet.
« Reply #678 on: March 22, 2016, 01:56:14 PM »
LOL!!!

Having a little disinfo-tizzy cos you got caught Lying about the exhaust velocity of a jumbo jet being lower than its cruising velocity, are you?

What a Loser.

Fact is that turbofan engines are VASTLY more efficient than the shitty toy rockets you worship...

So if a turbofan cannot exceed the velocity of its exhaust, no way a rocket can do it.

Grow up; learn to respect Newton; stop Lying.

Thanks please!

Like I said NO. The reason a jet engine cannot go faster than its exhaust is its intake.

There is only so much oxygen a turbo jet can intake. Due to the air it's intaking. A jet engine intakes air, slows it down, compresses it, mixes with fuel and ignites it.

A rocket doesn't do any of that. It just pumps in fuel and oxidiser at high pressure and ignites it.

A rocket in space has no external force to deal with. A jet has drag to deal with. And the limitations and intake velocity of the air its intaking to produce the thrust to overcome that drag and keep on accelerating.

Toy rocket?

They make any turbo jet look like a hair dryer.

Like I said. What is the variable that stops the rocket from accelerating when it equals its exhaust speed?

Simple question. Answer it.

Or crying are we because you got your rocket thread locked and thus have lost that entire argument?

« Last Edit: March 22, 2016, 02:02:05 PM by TylerJRB »

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Papa Legba

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Re: The ISS is a Gulfstream jet.
« Reply #679 on: March 22, 2016, 02:01:22 PM »
^Read all the Shite above.

Then read this:

I have owned you on this subject twice already; your next move will be to start banging on about nebulous 'forces' like a Star Wars nerd, playing with numbers, trying to confuse the terms velocity & acceleration, as well as citing Inertial Frames of Reference & other such junk-science.

Yeah, Legba called it...

Been here before.

Like I said; the words 'equal & opposite' don't seem to be in these geek's dictionaries.

Oh, & TylerJRB; Newton's 3rd Law is not a 'variable' you crank.

It is a LAW.

And your silly toy shpayze-rokkits violate it six ways from sunday.

& Heiwa; a balloon?

LOL!!!
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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #680 on: March 22, 2016, 02:05:11 PM »
^Read all the Shite above.

Then read this:

I have owned you on this subject twice already; your next move will be to start banging on about nebulous 'forces' like a Star Wars nerd, playing with numbers, trying to confuse the terms velocity & acceleration, as well as citing Inertial Frames of Reference & other such junk-science.

Yeah, Legba called it...

Been here before.

Like I said; the words 'equal & opposite' don't seem to be in these geek's dictionaries.

Oh, & TylerJRB; Newton's 3rd Law is not a 'variable' you crank.

It is a LAW.

And your silly toy shpayze-rokkits violate it six ways from sunday.

& Heiwa; a balloon?

LOL!!!

Papa Short Bus, here is the math. Prove it wrong.
Fuel and oxidizer are pumped into a chamber that is wide open on one end. This mixture is ignited causing it to expand at and explosive rate. One liter of LOX (liquid Ox) is more than 860.26 liters of gas.  One liter of Liquid Hydrogen is 849.22 liters of gas.

Burning this mixture creates a mass of water and unburned gasses which expands the mass and is ejected out the open end of the chamber with a force measured from a few foot pound to many tons, depending on the size and design of the engine. The fuel/water mass is pushing against the mass of the rocket not against a vacuum.

Simple middle school math and science and easy to prove in a vacuum chamber.

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Then there is this proofs which of course you will AGAIN ignore because you cannot disprove it.
A rocket engine is a device in which propellants are burned in a combustion chamber and the resulting high pressure gases are expanded through a specially shaped nozzle to produce thrust. The function of the nozzle is to convert the chemical-thermal energy generated in the combustion chamber into kinetic energy. The nozzle converts the slow moving, high pressure, high temperature gas in the combustion chamber into high velocity gas of lower pressure and temperature. Gas velocities from 2 to 4.5 kilometers per second can be obtained in rocket nozzles. The nozzles which perform this feat are called DeLaval nozzles (after the inventor) and consist of a convergent and divergent section. The minimum flow area between the convergent and divergent section is called the nozzle throat. The flow area at the end of the divergent section is called the nozzle exit area.

Hot exhaust gases expand in the diverging section of the nozzle. The pressure of these gases will decrease as energy is used to accelerate the gas to high velocity. The nozzle is usually made long enough (or the exit area great enough) such that the pressure in the combustion chamber is reduced at the nozzle exit to the pressure existing outside the nozzle. It is under this condition that thrust is maximum and the nozzle is said to be adapted, also called optimum or correct expansion. To understand this we must examine the basic thrust equation:

   F = q × Ve + (Pe - Pa) × Ae

   where F = Thrust
         q = Propellant mass flow rate
         Ve = Velocity of exhaust gases
         Pe = Pressure at nozzle exit
         Pa = Ambient pressure
         Ae = Area of nozzle exit
The product qVe is called the momentum, or velocity, thrust and the product (Pe-Pa)Ae is called the pressure thrust. As we have seen, Ve and Pe are inversely proportional, that is, as one increases the other decreases. If a nozzle is under-extended we have Pe>Pa and Ve is small. For an over-extended nozzle we have Pe<Pa and Ve is large. Thus, momentum thrust and pressure thrust are inversely proportional and, as we shall see, maximum thrust occurs when Pe=Pa.
Let us now consider an example. Assume we have a rocket engine equipped with an extendible nozzle. The engine is test fired in an environment with a constant ambient pressure. During the burn, the nozzle is extended from its fully retracted position to its fully extended position. At some point between fully retracted and fully extended Pe=Pa (see figure below).


As we extend the nozzle, the momentum thrust increases as Ve increases. At the same time the pressure thrust decreases as Pe decreases. The increase in momentum thrust is greater than the decrease in pressure thrust, thus the total thrust of the engine increases as we approach the condition Pe=Pa. As we continue to extend to nozzle the situation changes slightly. Now the pressure thrust changes in magnitude more rapidly than the momentum thrust, thus the total thrust begins to decrease.

Let's now apply some numbers to our example and run through the calculations to prove that this is true. Assume our rocket engine operates under the following conditions:

   q = Propellant mass flow rate = 100 kg/s         
   k = Specific heat ratio = 1.20           
   M = Exhaust gas molecular weight = 24             
   Tc = Combustion chamber temperature = 3600 K       
   Pc = Combustion chamber pressure = 5 MPa         
   Pa = Ambient pressure = 0.05 MPa       
If the nozzle is properly adapted to the operating conditions we have Pe=Pa, or Pe=0.05 MPa.

The gas pressure and temperature at the nozzle throat is less than in the combustion chamber due to the loss of thermal energy in accelerating the gas to the local speed of sound at the throat. Therefore, we calculate the pressure and temperature at the nozzle throat,

   Pt = Pc × [1 + (k - 1) / 2]-k/(k-1)
   Pt = 5 × [1 + (1.20 - 1) / 2]-1.20/(1.20-1)
   Pt = 2.82 MPa = 2.82x106 N/m2

   Tt = Tc × [1 / (1 + (k - 1) / 2)]
   Tt = 3,600 × [1 / (1 + (1.20 - 1) / 2)]
   Tt = 3,273 K
The area at the nozzle throat is given by

   At = (q / Pt) × SQRT[ (R' × Tt) / (M × k) ]
   At = (100 / 2.82x106) × SQRT[ (8,314 × 3,273) / (24 × 1.20) ]
   At = 0.0345 m2
The hot gases must now be expanded in the diverging section of the nozzle to obtain maximum thrust. The Mach number at the nozzle exit is given by

   Nm2 = (2 / (k - 1)) × [(Pc / Pa)(k-1)/k - 1]
   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.05)(1.20-1)/1.20 - 1]
   Nm2 = 11.54
   Nm = (11.54)1/2 = 3.40
The nozzle exit area corresponding to the exit Mach number is given by

   Ae = (At / Nm) × [(1 + (k - 1) / 2 × Nm2)/((k + 1) / 2)](k+1)/(2(k-1))
   Ae = (0.0345 / 3.40) × [(1 + (1.20 - 1) / 2 × 11.54)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.409 m2
The velocity of the exhaust gases at the nozzle exit is given by

   Ve = SQRT[ (2 × k / (k - 1)) × (R' × Tc / M) × (1 - (Pe / Pc)(k-1)/k) ]
   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.05 / 5)(1.20-1)/1.20) ]
   Ve = 2,832 m/s
Finally, we calculate the thrust,

   F = q × Ve + (Pe - Pa) × Ae
   F = 100 × 2,832 + (0.05x106 - 0.05x106) × 0.409
   F = 283,200 N


Let's now consider what happens when the nozzle is under-extended, that is Pe>Pa. If we assume Pe=Pa × 2, we have

   Pe = 0.05 × 2 = 0.10 MPa   
   
   At = 0.0345 m2

   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.10)(1.20-1)/1.20 - 1]
   Nm2 = 9.19
   Nm = (9.19)1/2 = 3.03

   Ae = (0.0345 / 3.03) × [(1 + (1.20 - 1) / 2 × 9.19)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.243 m2

   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.10 / 5)(1.20-1)/1.20) ]
   Ve = 2,677 m/s

   F = 100 × 2,677 + (0.10x106 - 0.05x106) × 0.243
   F = 279,850 N


Now we consider the over-extended condition, that is Pe<Pa. If we assume Pe=Pa / 2, we have

   Pe = 0.05 / 2 = 0.025 MPa   
   
   At = 0.0345 m2

   Nm2 = (2 / (1.20 - 1)) × [(5 / 0.025)(1.20-1)/1.20 - 1]
   Nm2 = 14.18
   Nm = (14.18)1/2 = 3.77

   Ae = (0.0345 / 3.77) × [(1 + (1.20 - 1) / 2 × 14.18)/((1.20 + 1) / 2)](1.20+1)/(2(1.20-1))
   Ae = 0.696 m2

   Ve = SQRT[ (2 × 1.20 / (1.20 - 1)) × (8,314 × 3,600 / 24) × (1 - (0.025 / 5)(1.20-1)/1.20) ]
   Ve = 2,963 m/s

   F = 100 × 2,963 + (0.025x106 - 0.05x106) × 0.696
   F = 278,900 N


We see that both the under-extended and over-extended nozzles produce thrusts less than that produced when the condition Pe=Pa is satisfied. When we plot a graph of total thrust versus the ratio Pa/Pe we obtain the following:

As can be easily seen, thrust is maximum when Pa/Pe=1, or when Pe=Pa.
Stupidity cannot be cured with money, or through education, or by legislation. Stupidity is not a sin, the victim can't help being stupid. But stupidity is the only universal capital crime...

Re: The ISS is a Gulfstream jet.
« Reply #681 on: March 22, 2016, 02:18:44 PM »
Well if the rocket is accelerating at 10m/s. What stops it from accelerating any further when it reaches 1000m/s exhaust velocity?

Quite clearly there is still the same amount of thrust being produced at 999m/s. So when it reaches 1000m/s what stops it? there is physically no force externally to stop it from accelerating in a vacuum.

Newtons 3rd. HAHAHAHAHA. Wasn't you the one saying it doesn't apply to a gas? Thus a rocket won't work because it's gas cannot push it.

Lol that sneaky mind change there. Moved from rockets cannot produce thrust in a vacuum. To rockets cannot go faster than their exhaust velocity. Any bets on which thread you make next?
« Last Edit: March 22, 2016, 02:22:14 PM by TylerJRB »

Re: The ISS is a Gulfstream jet.
« Reply #682 on: March 22, 2016, 02:56:18 PM »
How can it push against a vacuum? A vacuum is nothing.

First Law of Poppa-Fhysics: state the bleeding obvious while ignoring the actual point.

Quote
Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

2nd Law of Poppa-Fhysics: continue to lie in the face of insurmountable odds and unimpeachable evidence.

Quote
a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

That's not one of Newton's Laws: It's Poppa-Fhysics Law of Conservation of Velocity.
I made up some completely random sh!te on the Flat Earth Society forum and now I feel completely and utterly EPIC!!!

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Re: The ISS is a Gulfstream jet.
« Reply #683 on: March 22, 2016, 03:14:23 PM »
How can it push against a vacuum? A vacuum is nothing.

First Law of Poppa-Fhysics: state the bleeding obvious while ignoring the actual point.

Quote
Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

2nd Law of Poppa-Fhysics: continue to lie in the face of insurmountable odds and unimpeachable evidence.

Quote
a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

That's not one of Newton's Laws: It's Poppa-Fhysics Law of Conservation of Velocity.

one more Papa Fhysics law. A jet and a rocket in the atmosphere pushes on a gas for thrust. But in space gas cannot push against combustion chamber to do the something.
Stupidity cannot be cured with money, or through education, or by legislation. Stupidity is not a sin, the victim can't help being stupid. But stupidity is the only universal capital crime...

Re: The ISS is a Gulfstream jet.
« Reply #684 on: March 22, 2016, 03:58:26 PM »
How can it push against a vacuum? A vacuum is nothing.

First Law of Poppa-Fhysics: state the bleeding obvious while ignoring the actual point.

Quote
Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

2nd Law of Poppa-Fhysics: continue to lie in the face of insurmountable odds and unimpeachable evidence.

Quote
a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

That's not one of Newton's Laws: It's Poppa-Fhysics Law of Conservation of Velocity.

one more Papa Fhysics law. A jet and a rocket in the atmosphere pushes on a gas for thrust. But in space gas cannot push against combustion chamber to do the something.
That is Poppas law of vacuums, being in a vacuum removes all the normal properties of a gas (being able to have mass, momentum and pressure to name a few). This is because the vacuum instantly sucks away all the gas, so the normal laws of physics have no time to work.

Re: The ISS is a Gulfstream jet.
« Reply #685 on: March 22, 2016, 04:11:57 PM »
How can it push against a vacuum? A vacuum is nothing.

First Law of Poppa-Fhysics: state the bleeding obvious while ignoring the actual point.

Quote
Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

2nd Law of Poppa-Fhysics: continue to lie in the face of insurmountable odds and unimpeachable evidence.

Quote
a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

That's not one of Newton's Laws: It's Poppa-Fhysics Law of Conservation of Velocity.

one more Papa Fhysics law. A jet and a rocket in the atmosphere pushes on a gas for thrust. But in space gas cannot push against combustion chamber to do the something.
That is Poppas law of vacuums, being in a vacuum removes all the normal properties of a gas (being able to have mass, momentum and pressure to name a few). This is because the vacuum instantly sucks away all the gas, so the normal laws of physics have no time to work.

Not forgetting rocket and propellant are the same object. Therefore rocket does not work because they are same object.

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Round and Proud

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Re: The ISS is a Gulfstream jet.
« Reply #686 on: March 22, 2016, 04:14:43 PM »
All this is too funny.
Stupidity cannot be cured with money, or through education, or by legislation. Stupidity is not a sin, the victim can't help being stupid. But stupidity is the only universal capital crime...

Re: The ISS is a Gulfstream jet.
« Reply #687 on: March 23, 2016, 01:42:58 AM »
How can it push against a vacuum? A vacuum is nothing.

First Law of Poppa-Fhysics: state the bleeding obvious while ignoring the actual point.

Quote
Nonetheless, it must be creating pressure in order to push against SOMETHING.

But pressure is impossible to create in an Infinite vacuum...

2nd Law of Poppa-Fhysics: continue to lie in the face of insurmountable odds and unimpeachable evidence.

Quote
a Push of 5,000 mph can never equal a Push of more than 5,000 mph in the opposite direction.

But Newton's 3rd seems to be totally beyond you...

That's not one of Newton's Laws: It's Poppa-Fhysics Law of Conservation of Velocity.

one more Papa Fhysics law. A jet and a rocket in the atmosphere pushes on a gas for thrust. But in space gas cannot push against combustion chamber to do the something.
That is Poppas law of vacuums, being in a vacuum removes all the normal properties of a gas (being able to have mass, momentum and pressure to name a few). This is because the vacuum instantly sucks away all the gas, so the normal laws of physics have no time to work.

Not forgetting rocket and propellant are the same object. Therefore rocket does not work because they are same object.
That's Poppa's law of counting, when counting objects you can only count the ones you see, so if one object is inside another, you don't count it as an object. E. G. If you look at a house that has someone inside of it, the person inside is the same object as the house, so they get stuck to the floor because you can't push against yourself.

Re: The ISS is a Gulfstream jet.
« Reply #688 on: March 23, 2016, 05:41:45 AM »
If you look at a house that has someone inside of it, the person inside is the same object as the house, so they get stuck to the floor because you can't push against yourself.

Wow! Not only did Poppa prove rockets don't work in a vacuum, he also proved people can't walk inside a house! ROFLMTO!  ;D
I made up some completely random sh!te on the Flat Earth Society forum and now I feel completely and utterly EPIC!!!

Re: The ISS is a Gulfstream jet.
« Reply #689 on: March 23, 2016, 06:06:51 AM »
In fairness to PL (and I'm not sure why I should be, given his nature), he may possibly be referring to the Tsiolkovsky equation. However, this doesn't limit the final velocity of the rocket to the velocity of the exhaust, it is simply a factor.

The equation is:-

Vdelta  = Ve x ln (m0/m1)

Vdelta = change in velocity
Ve = exhaust velocity
m0 = initial rocket mass including propellant
m1 = final rocket mass minus burnt propellant

So you can see the 2 velocities are mathematically related.

You can also see that providing  ln (m0/m1) > 1 , then the rocket velocity will exceed the velocity of the exhaust gas. On other words, providing m0 >= 2.72 * m1, then the rocket's change in velocity will be greater than the velocity of the exhaust gas.

All of which I'm sure Poppa meant to say, but just got... confused?

That's OK, we all get confused occasionally. I'm not confused now I'm on the right meds. I don't like taking them though - I feed them to the gorilla that sleeps in my wardobe here on the unit. He's gonna need them more than me for his next spell in the ISS Gulfstream jet.
I made up some completely random sh!te on the Flat Earth Society forum and now I feel completely and utterly EPIC!!!