People on skateboards.

Quote from: Gaia_Redonda on December 16, 2015, 08:30:38 AM

Quote from: markjo on December 16, 2015, 07:33:11 AM

...you need energy to accelerate the combustion gasses that push against the rocket engine.

There is no gas in space. It's a near vacuum of <10^-16 bar and 3 K (-270 C) temperature.

I'm not referring to gas in space.  I'm referring to gas in the combustion chamber which can build to several thousand psi.

Right. Then the -under those pressures liquid- gases mix, exit the nozzle and instantaneously turn into solid solitary molecules floating away in space.

The molecules do not perform any work by "pushing against each other" to move any rocket.

Rockets are useless in space as they work on the basis of combustion of gases. They are made for and under atmospheric conditions.

Defying gravity and nature, jumping orbits! Amazing.

Any material to support your statement? Like a set of equations that describes orbit as a function of only gravity?

Quote from: markjo on December 16, 2015, 11:07:31 AM

Quote from: Gaia_Redonda on December 16, 2015, 08:30:38 AM

Quote from: markjo on December 16, 2015, 07:33:11 AM

...you need energy to accelerate the combustion gasses that push against the rocket engine.

There is no gas in space. It's a near vacuum of <10^-16 bar and 3 K (-270 C) temperature.

I'm not referring to gas in space.  I'm referring to gas in the combustion chamber which can build to several thousand psi.

Right. Then the -under those pressures liquid- gases mix, exit the nozzle and instantaneously turn into solid solitary molecules floating away in space.

The molecules do not perform any work by "pushing against each other" to move any rocket.

Rockets are useless in space as they work on the basis of combustion of gases. They are made for and under atmospheric conditions.

The work is being done in the nozzle which is not in vacuum conditions

Solitary molecules cannot be defined as solid or liquid since the solid or liquid state is due to different bonds between molecules.

Not every rocket is based on combustion between fuel and oxidizer

Quote from: markjo on December 16, 2015, 11:07:31 AM

Quote from: Gaia_Redonda on December 16, 2015, 08:30:38 AM

Quote from: markjo on December 16, 2015, 07:33:11 AM

...you need energy to accelerate the combustion gasses that push against the rocket engine.

There is no gas in space. It's a near vacuum of <10^-16 bar and 3 K (-270 C) temperature.

I'm not referring to gas in space.  I'm referring to gas in the combustion chamber which can build to several thousand psi.

Right. Then the -under those pressures liquid- gases mix, exit the nozzle and instantaneously turn into solid solitary molecules floating away in space.

Who care what happens after the gas leaves the nozzle?  All the work that we care about is done inside the combustion chamber.

The molecules do not perform any work by "pushing against each other" to move any rocket.

Correct.  The molecules perform work by pushing against the walls of the combustion chamber.

Rockets are useless in space as they work on the basis of combustion of gases. They are made for and under atmospheric conditions.

Do you have any personal experience designing rocket engines, or are you just assuming?

Why does it have to expand to be equal? Does the guy need put on a netal shell and nose cone to be equal to the rocket?

LOL!!!

He is.

Read again and answer the question:

The ball is the fuel/oxidizer exhaust.

But markjo claimed the fuel is EXPANDING.

Look:

the expanding (burning) propellant is ONE object using stored energy to create a force by expanding against a SECOND object, i.e. the combustion chamber.

If the ball is the fuel in your example, why is it NOT expanding?

The work is being done in the nozzle which is not in vacuum conditions

Oh, the work is already done!? So putting an exhaust on that skateboard, where you blow air from and bind a balloon around it, the skateboard still moves? The work is done in the closed compartment, here the balloon, you say...

Solitary molecules cannot be defined as solid or liquid since the solid or liquid state is due to different bonds between molecules.

This is actually true. But if they are in pairs solidifying immediately due to the near-zero temperatures and pressures, the mechanism is the same.

Not every rocket is based on combustion between fuel and oxidizer

The ones "going to space" are based on graphic cards and mouseclicks, indeed.

Quote from: sokarul on December 16, 2015, 10:34:54 AM

Why does it have to expand to be equal? Does the guy need put on a netal shell and nose cone to be equal to the rocket?

LOL!!!

He is.

Read again and answer the question:

Quote from: sokarul on December 16, 2015, 10:17:03 AM

The ball is the fuel/oxidizer exhaust.

But markjo claimed the fuel is EXPANDING.

Look:

Quote from: markjo on December 14, 2015, 09:02:26 AM

the expanding (burning) propellant is ONE object using stored energy to create a force by expanding against a SECOND object, i.e. the combustion chamber.

If the ball is the fuel in your example, why is it NOT expanding?

Try reading again.

Quote from: Papa Legba on December 16, 2015, 10:27:24 AM

Quote from: sokarul on December 16, 2015, 10:17:03 AM

The ball is the fuel/oxidizer exhaust.

But markjo claimed the fuel is EXPANDING.

Look:

Quote from: markjo on December 14, 2015, 09:02:26 AM

the expanding (burning) propellant is ONE object using stored energy to create a force by expanding against a SECOND object, i.e. the combustion chamber.

If the ball is the fuel in your example, why is it NOT expanding?

Why does it have to expand to be equal? Does the guy need put on a netal shell and nose cone to be equal to the rocket?

All the work that we care about is done inside the combustion chamber.

The combustion chamber is open to the vacuum.

Therefore:

The combustion chamber of a rocket is open to the near-infinite vacuum of space.

Therefore, no gas can even be meaningfully said to exist within it, let alone combust.

Any gas introduced therein when the pressurised fuel tank leading to the combustion chamber is opened will simply expand freely into the enormous, zero-pressure vacuum, following the path of least resistance & doing no work whatsoever.

This will continue for as long as the fuel tank & chamber are open to the vacuum, until both exterior & interior pressures are equalised at zero.

It is a beautifully simple concept, fully supported by All the laws of physics, yet you 'round earthers' (lol!) just can't seem to grasp it...


Plus this:

You all claim that the recoil of a gun is a valid analogy for how a rocket works in a vacuum.

Here is why it is not:

With a gun you have object A, the mass of the gun; the expanding propellant, P, the gunpowder, sited between them; and object B, the mass of the bullet.

But with a rocket you ONLY have object A, the mass of the rocket,  & the expanding propellant, P, the fuel.

No object B, see?

Thus, you have removed the necessary recoil mass 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.

No matter how hard you try to spin it, cultists, every child knows that You cannot Push on Nothing.

No maths required; only common sense.


Then there's the fact that you are all trying desperately to confine this 'debate' to the wrong branch of physics, i.e. Solid Mechanics rather than Fluid Mechanics...

Kinda dishonest of you, dontcha think?

Pressure-Gradient Forces, Gas Laws, Fluid Mechanics, Continuum Assumption & Joules Expansion are the areas I suggest neutral readers research.

Oh; & Thermodynamics too - thanks for that, markjo!



Sokarul:

The ball is the fuel/oxidizer exhaust.

Simple question: IS THE BALL EXPANDING?

No
Why does it need to expand?

Quote from: luckyfred on December 16, 2015, 11:20:35 AM

The work is being done in the nozzle which is not in vacuum conditions

Oh, the work is already done!? So putting an exhaust on that skateboard, where you blow air from and bind a balloon around it, the skateboard still moves? The work is done in the closed compartment, here the balloon, you say...

Quote

Solitary molecules cannot be defined as solid or liquid since the solid or liquid state is due to different bonds between molecules.

This is actually true. But if they are in pairs solidifying immediately due to the near-zero temperatures and pressures, the mechanism is the same.

Quote

Not every rocket is based on combustion between fuel and oxidizer

The ones "going to space" are based on graphic cards and mouseclicks, indeed.

In your case u don't have mass leaving the skateboard so thrust cannot be produce, all the enrgy will end up in inflating the baloon.


So no set of equations to suport your statement?

No. Why does it need to expand?

Because you said this:

The ball is the fuel/oxidizer exhaust.

Whilst markjo said this:

the expanding (burning) propellant is ONE object using stored energy to create a force by expanding against a SECOND object, i.e. the combustion chamber.

So, if the ball is NOT expanding, then your whole analogy FAILS.

Forgetfull at your old age? Remember evidence vs proof? You think you proved a science argument thereby proving general relativity. When do you think your Nobel Orize will show up?

First, it's "Nobel Prize".  Second, I never claimed to have proven General Relativity.  That would be silly.  Please provide the quote where I said this.

My request of based of your claim I'm always wrong.  It turns out you don't think my content is wrong, rather my typing is wrong, based on your continued refusal to find a post of mine with incorrect statements in it.

Well, your content made no sense, since you suck at everything.  Haven't you claimed to be a chemist all over these forums?  And you are this bad at writing?  All the chemists I work with perform experiments and write technical papers on their results.  If any of them wrote as bad as you constantly do, they would have been fired long ago.  Are you a discount chemist?  You work at a lower pay rate since you suck at everything?

Now, please provide the quote I've requested above, and I'll simply use that one to show you a post of yours with incorrect statements.  I'll wait.

Here you go, 'engy baby'; one sokarul post that is completely & utterly Incorrect:

Man is the rocket.
The ball is the fuel/oxidizer exhaust.
His arms are like the reaction to apply a force to a mass to get acceleration.

You can thank me later...

Toodle-pip!

Because there's nothing for the exhaust to push against.  Duh.

You realize that once the rocket escapes the Earth's gravitational pull it does not require more fuel to move it.

In your case u don't have mass leaving the skateboard so thrust cannot be produce, all the enrgy will end up in inflating the baloon.

Exactly.

It is the release of the mass in 1 direction which pushes the rocket in the opposite direction. The "work is done" before the gas exits is impossible; it is the exhaust of the gas that moves a rocket, so that is the work done.

So both your closed off chamber and the balloon will not move the rocket resp. skateboard as no counterforce is created.

That moment only comes when you pop the balloon or open the nozzle to the vacuum.

So your statement that "the work is already done in the combustion chamber" cannot be correct as that would move the skateboard too.

I said nozzle.
Energy is produced in the combustion chamber, then thermal and pressure energy are partly converted into work by the nozzle.

But if u close the system all changes since the work produced by the espanding gas in the nozzle is then utilized to compress the exhausted gasses in the balloon so the total work of the system is zero.

Let us again consider the 'combustion chamber' of  a rocket:

The combustion chamber of a rocket is open to the near-infinite vacuum of space.

Therefore, no gas can even be meaningfully said to exist within it, let alone combust.

Any gas introduced therein when the pressurised fuel tank leading to the combustion chamber is opened will simply expand freely into the enormous, zero-pressure vacuum, following the path of least resistance & doing no work whatsoever.

This will continue for as long as the fuel tank & chamber are open to the vacuum, until both exterior & interior pressures are equalised at zero.

It is a beautifully simple concept, fully supported by All the laws of physics, yet you 'round earthers' (lol!) just can't seem to grasp it...


Plus this:

You all claim that the recoil of a gun is a valid analogy for how a rocket works in a vacuum.

Here is why it is not:

With a gun you have object A, the mass of the gun; the expanding propellant, P, the gunpowder, sited between them; and object B, the mass of the bullet.

But with a rocket you ONLY have object A, the mass of the rocket,  & the expanding propellant, P, the fuel.

No object B, see?

Thus, you have removed the necessary recoil mass 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.

No matter how hard you try to spin it, cultists, every child knows that You cannot Push on Nothing.

No maths required; only common sense.


Then there's the fact that you are all trying desperately to confine this 'debate' to the wrong branch of physics, i.e. Solid Mechanics rather than Fluid Mechanics...

Kinda dishonest of you, dontcha think?

Pressure-Gradient Forces, Gas Laws, Fluid Mechanics, Continuum Assumption & Joules Expansion are the areas I suggest neutral readers research.

Oh; & Thermodynamics too - thanks for that, markjo!

...pressure energy....

I may have missed a physics class or two, but "pressure energy" is a physical term I am unfamiliar with.

Let the thermal part rest, we are talking near-zero temperatures in space. No rocket can ever survive that.

we are talking near-zero temperatures in space.

Are we?

What about the alleged properties of the thermosphere, plus the insulating nature of a vacuum?

Quote from: Gaia_Redonda on December 16, 2015, 01:47:48 PM

we are talking near-zero temperatures in space.

Are we?

What about the alleged properties of the thermosphere, plus the insulating nature of a vacuum?

Good question:

we have:
- Atmosphere - part of the skies where some pressure is there to have gases
- Space - part of the skies above that; P ~ 0

The upper part of the atmosphere, with an unknown boundary between atmosphere and space as nobody nor instruments have been there, is the thermosphere.

Wiki states some things quite well:

Even though the temperature is so high, one would not feel warm in the thermosphere, because it is so near vacuum that there is not enough contact with the few atoms of gas to transfer much heat.

...the energy lost by thermal radiation would exceed the energy acquired from the atmospheric gas by direct contact.

And of course is infected with such crap:

The International Space Station orbits within the middle of the thermosphere, between 330 and 435 kilometres (205 and 270 mi) (decaying by 2 km/month and raised by periodic reboosts), whereas the Gravity Field and Steady-State Ocean Circulation Explorer satellite at 260 kilometres (160 mi) utilized winglets [??] and an innovative ion engine to maintain a stable orientation and orbit.

Whoops, gravity is messing with Santa NASA, we have to correct here...

So it's a bit difficult to speak of temperature in low pressure conditions.

The value for space is set at 3 K. That may or may not be true, but does it make sense? I would say yes:

Heat is transferred either by:
- convection - needs a medium for that
- conduction - idem
- radiation

The higher you come the lower the pressure; less molecules / km2
convection: The higher you come the less thermal effects as there is less "air" to transfer this effect
conduction: will come to that
radiation: every particle receiving heat through radiation from the only source possible (the Sun) will heat up and no possibility to give off the heat due to the low pressure (explaining the thermosphere values)

I was stating that the low temperature of the vacuum would not let the rocket survive.

That is because if you imagine a rocket there (which cannot come there in the first place), it is black and white.

50% of this cilinder is heated by the Sun through radiation, and the surface of that cilinder conducts the received heat according to the thermal conductivity of the material
but 50 % of that same cilinder is in the stone cold un-radiated shadow surrounded by near vacuum...

The problem is that the material properties of the rocket (some Al-Ti-Fe-alloy) are drastically affected by its temperature itself.

Mechanical (rigidity, cohesive strength) and other material properties are affected by that temperature. The thermal conductivity itself is also depending on the temperature of the material.

Having 50% of Sun shine alloy of some 300 degrees would be ok. But how does the other side work? It would crumble away and the thermal distribution along the cilinder circumference would go nuts. It would shatter to crumbles just as you can break metals which are kept under very low temperatures easily; no rigidity anymore...

From +300 to almost -270 in the same medium made of the same material...

The materials will fail and the rocket would be shattered to space dust.

I don't understand what you mean with an "insulating effect" of a vacuum?

Quote from: luckyfred on December 16, 2015, 01:36:04 PM

...pressure energy....

I may have missed a physics class or two, but "pressure energy" is a physical term I am unfamiliar with.

Let the thermal part rest, we are talking near-zero temperatures in space. No rocket can ever survive that.

pressure potential energy....bernoulli's equation, static pressure represent a sort of potential energy while dynamic pressure is like a kinetical energy.

sorry but vacuum can be even a zero temperature but all bodies in our solar system are heated by the sun, so the rocket is not at zero temperature.

actually the control of the heating of a satellite by the sun is quite a fascinating topic

during apollo mission they used a very simple heating control....the made the spacecraft spin so that the sun would irradiate all the craft homogeneously

during apollo mission they used a very simple heating control....the made the spacecraft spin so that the sun would irradiate all the craft homogeneously

Sure, in the 60s people were able to keep a perfect thermal balance 300,000 km away. While everybody was dancing with flowers in their hairs, NASA was doing something pretty extraordinary. Pretty disappointing we don't have this technology implemented anywhere... in 2015...

How did the astronauts feel when they "stepped" on the Moon in the shade?

The -270 was ok, because the suits were made for -150, no problem, that extra -120 is a piece of space cake...

Quote from: luckyfred on December 16, 2015, 02:36:42 PM

during apollo mission they used a very simple heating control....the made the spacecraft spin so that the sun would irradiate all the craft homogeneously

Sure, in the 60s people were able to keep a perfect thermal balance 300,000 km away. While everybody was dancing with flowers in their hairs, NASA was doing something pretty extraordinary. Pretty disappointing we don't have this technology implemented anywhere... in 2015...

How did the astronauts feel when they "stepped" on the Moon in the shade?

The -270 was ok, because the suits were made for -150, no problem, that extra -120 is a piece of space cake...

which technology? the one that control the temperature by spinnig?
btw the only shade i can think of is the one provided by the lem and u're forgetting that there is the refraction of the moon soil.

actually i find it very fascinating... what man can do when is given basically illimitated funding and nothing else to worry apart reaching his goal.

which technology? the one that control the temperature by spinnig?

What was the time of the spin? How long did it take for the rocket to make 1 spin and have 360 degrees of 50% radiation and 50% shade? Any numbers on that?

And how did Michael Collins keep his seat warm those 3 days his buddies Ed and Neil were playing in the sand pit below? He was allegedly making orbits around the Moon. That means at least 50% of the time he must have been on the dark, stone cold side of the Moon. No spinning solution there, my friend, how did he keep himself from being scattered onto the helmets of his mates?

btw the only shade i can think of is the one provided by the lem and u're forgetting that there is the refraction of the moon soil.

You don't even know the "landing" of the Eagle by heart? For a shill you're really amateur.

actually i find it very fascinating... what man can do when is given basically illimitated funding and nothing else to worry apart reaching his goal.

Sure. Illimitated funding, indeed.

Quote from: markjo on December 16, 2015, 11:33:24 AM

All the work that we care about is done inside the combustion chamber.

The combustion chamber is open to the vacuum.

Yes, it is.  However, that doesn't mean that expansion of the gas is unconstrained within the combustion chamber.  The expansion of the gas is constrained by the geometry of the chamber and the viscosity of the gas itself.

Quote from: luckyfred on December 16, 2015, 02:54:27 PM

which technology? the one that control the temperature by spinnig?

What was the time of the spin? How long did it take for the rocket to make 1 spin and have 360 degrees of 50% radiation and 50% shade? Any numbers on that?

And how did Michael Collins keep his seat warm those 3 days his buddies Ed and Neil were playing in the sand pit below? He was allegedly making orbits around the Moon. That means at least 50% of the time he must have been on the dark, stone cold side of the Moon. No spinning solution there, my friend, how did he keep himself from being scattered onto the helmets of his mates?

Quote

btw the only shade i can think of is the one provided by the lem and u're forgetting that there is the refraction of the moon soil.

You don't even know the "landing" of the Eagle by heart? For a shill you're really amateur.

Quote

actually i find it very fascinating... what man can do when is given basically illimitated funding and nothing else to worry apart reaching his goal.

Sure. Illimitated funding, indeed.

 spinnig method is a passive method that helps but there's also a lot of heat sources inside the spacecraft, for example every single electrival component produces heat.

if u want more details
http://www.esa.int/esapub/bulletin/bullet87/paroli87.htm

i don't know the first moon landing site by earth, there was something else, apart the lem, to cast a shadow?

ps still waiting matematichal backup to your theory that orbit are determinend only by gravity

Quote from: sokarul on December 16, 2015, 10:13:51 AM

Forgetfull at your old age? Remember evidence vs proof? You think you proved a science argument thereby proving general relativity. When do you think your Nobel Orize will show up?

First, it's "Nobel Prize". 

Learn what a smart phone is and report back.

Second, I never claimed to have proven General Relativity.  That would be silly.  Please provide the quote where I said this.

I literally explained it to you in the quote.  “You think you proved a science argument thereby proving general relativity.” The proof vs evidence debate we had. You can't prove an argument by using General Relativity because you would have to prove General Relativity and you can't prove theories.

Quote

My request of based of your claim I'm always wrong.  It turns out you don't think my content is wrong, rather my typing is wrong, based on your continued refusal to find a post of mine with incorrect statements in it.

Well, your content made no sense, since you suck at everything.

Strange, you figured it out just fine.

Haven't you claimed to be a chemist all over these forums?  And you are this bad at writing?  All the chemists I work with perform experiments and write technical papers on their results.

Yes. Not all chemists write papers. Just like not all engineers design bridges. But no, chemists you work with would not write papers on their results. That would be part of them, but there's a few more parts of the scientific method they would include.

If any of them wrote as bad as you constantly do, they would have been fired long ago.  Are you a discount chemist?  You work at a lower pay rate since you suck at everything?

How many of them write their papers on iPhones? It's funny though, you changes from saying I’m always wrong to saying I suck at everything. Probably because you couldn't find any mistakes that weren't typos.

Learn what a smart phone is and report back.

Too bad for you a smart phone is not smart enough to overcome your idiocy.

I literally explained it to you in the quote.  “You think you proved a science argument thereby proving general relativity.” The proof vs evidence debate we had. You can't prove an argument by using General Relativity because you would have to prove General Relativity and you can't prove theories.

'Literally explained' what?  I asked for you to provide the quote.

Strange, you figured it out just fine.

I have 3 kids; I'm used to deciphering gibberish.

But no, chemists you work with would not write papers on their results

Really?  Then why do I have a stack of reports written by chemists on the results of experiments I have asked for?  Maybe only real chemists write reports.

How many of them write their papers on iPhones?

I would assume none.  Are you trying to blame your smart phone for your inability to properly convey a message?  That's lame.

It's funny though, you changes from saying I’m always wrong to saying I suck at everything.

I gave you too much credit apparently.

So, I'm still waiting for that quote...

Let us again consider the 'combustion chamber' of  a rocket:
The combustion chamber of a rocket is open to the near-infinite vacuum of space.
Therefore, no gas can even be meaningfully said to exist within it, let alone combust.

When can you get the simple fact that the combustion chamber (and nozzle) are NOT exposed to the extremely low outside pressure, so long as we have choked flow in the throat of the nozzle.
The "choked flow" condition in the de Laval (or convergent-divergent) nozzle is reached when the flow velocity in the throat reaches sonic speed.  The gas  expanding past the throat increases to hypersonic speeds before exiting the nozzle.

One of the most elementary principles of supersonic flow (of which I am no expert!) is that disturbances cannot propagate back up the flow.  At sub-sonic speeds the air can flow smoothly over an object, because the disturbance caused by the obect is "signalled ahead", but once we get to supersonic speeds this cannot happen, hence the shock waves and other effects.

In the case of the choked de Laval nozzle, the gases in the combustion chamber and nozzle never feel the changes in outside pressure (hence choked) change, because we simply cannot get disturbance propagation against the supersonic gas flow - can't happen.

I'd get you the equation for (mass flow rate) ~ (ambient pressure) or (exhaust velocity) ~ (ambient pressure), but I know how papa hates "NASA approved equations" - even though de Laval knew this in 1888!  No point giving any equations or graphs, papa takes no notice.

The important point is that, once the choked flow condition is reached, the outside pressure, no matter how low, can have no effect on mass flow.

papa legba comments that the gases in the combustion could never be ignited, well:
(1) In the ascending rocket they are already ignited, so no problem unless the "fire goes out".
(2) On the ground, or under low pressure conditions ignition can be produced by starting with a hypergolic fuel and changing over to the primary fuel after ignition, as on the F-1 engine.
The law of conservation of momentum could have told you all this right from the start - of course it was used to derive the equations.

So papa the de Laval works under vacuum conditions because the combustion chambers is not exposed to the near-infinite vacuum of space, it simply does not know about it!
Of, course I might have all this wrong, so maybe papa could explain simply what the significance of the choked condition of a de Laval nozzle means.
PS I did not know you "believed in space", so what is the point of all your rantings and ravings?