It's 2015 and you aren't even close to owning a Spaceship

Quote from: Papa Legba on April 25, 2015, 01:56:36 PM

Firstly, try learning how to apply Newtons 3rd law correctly to a device as simple as a rocket (clue: a rocket's exhaust column Pushes against an outside Mass, such as the atmosphere; no outside Mass, no Push).

I don't need to read all the thread to understand that u know nothing about rocket propulsion. this is from page one.

rocket do not push against an outside mass. rocket accelerates the propellant through the nozzle, which results in a force acting on the propellant. same force, opposite direction, acts on the nozzles, propelling the rocket.
often is more practical to consider the mass flow of the propellant, in that case the thrust is given by mass flow*speed of the propellant exiting the nozzle.

if u aren't satisfied and u want the math supporting my statement: http://web.mit.edu/16.unified/www/SPRING/propulsion/Propulsion.pdf
don't worry, u need to read only the first five pages and there are a couple of pictures as well.
no bs about the link being unsafe, is from MIT, not from military or government agencies.

This is how rocket propulsion work. Are u missing how the propellant is composed by millions of bodies to which 3rd law is applied?

Pay attention cause this is chemistry 101 and physics 101, they don't teach them to welder school apparently.

Hypothesis: solid rocket fuel
Millions of bodies make up the propellant.
There are very strong chemical bonds among them, they act as a single solid body.
Combustion occurs
Combustion reaction destroys strong chemical bonds
Each body is now free to move independently.
Solid propellant has become a gas.
Each particle of that gas is an independent body on which Newton's 3rd law can be applied.
Nozzle accelerates gas.
Nozzle produce a force on gas particles and gas particles produce an equal and opposite force on the nozzle.
Rocket is propelled
No atmosphere involved

Quote from: rabinoz on November 23, 2015, 02:58:42 AM

Anyone arguing that a rocket is propelled by pressure on the air is talking an absolute impossibility with any rocket where the exhaust velocity at the bell mouth is supersonic.

Ever heard of pressure differentials?
Pressure gradient forces?
Do these not exist in your tiny little world?
Oh, & nice to see you've come round since your last post; you sounded kinda... different in it.
Kinda foreign; like English may not have been your first language maybe?
LOL!!!

1) Yes, I must retract my earlier post, but I was looking for some logical reason for your simply acting like an utterly despicable character who calls everyone a liar at the slightest provocation.  You have dispelled that notion and I am sorry to say I am finally convinced that must be an utterly despicable character who just loves to call all and sundry liars!  Well, it's nice to know where we stand.
2) Yes, I know about pressure differentials and pressure gradient forces, but they still cannot propagate faster than the speed of sound - go look up a bit on supersonic aerodynamics.  Now, I am not saying a rocket requires a supersonic exhaust velocity, it's just that when it is there can be no possibility of relying on "pushing" on the air. 
It's no point carrying on with this of course, you know your position will not be changed and from all I have read I can't see me being readily convinced by anything I have seen from you.  Of course I have done NO practical "rocket science" - apart from a few trivial episodes of doubtful legality many many years ago -  and they were not "science", pure hands on.  Must have been successful as I still have both hands - ear drums - that's another matter!
3) No, I am afraid my native language is Strine, so I have to try hard to translate these posts into English.  Occasionally I break into Academic, but I'm trying to get over it!

Yes, I know about pressure differentials and pressure gradient forces, but they still cannot propagate faster than the speed of sound

The speed of sound changes with temperature.

Which is good news for supersonic jet aircraft.

Because they push on the air.

Quote from: luckyfred on November 22, 2015, 05:42:34 PM

Quote from: Papa Legba on April 25, 2015, 01:56:36 PM

Firstly, try learning how to apply Newtons 3rd law correctly to a device as simple as a rocket (clue: a rocket's exhaust column Pushes against an outside Mass, such as the atmosphere; no outside Mass, no Push).

I don't need to read all the thread to understand that u know nothing about rocket propulsion. this is from page one.

rocket do not push against an outside mass. rocket accelerates the propellant through the nozzle, which results in a force acting on the propellant. same force, opposite direction, acts on the nozzles, propelling the rocket.
often is more practical to consider the mass flow of the propellant, in that case the thrust is given by mass flow*speed of the propellant exiting the nozzle.

if u aren't satisfied and u want the math supporting my statement: http://web.mit.edu/16.unified/www/SPRING/propulsion/Propulsion.pdf
don't worry, u need to read only the first five pages and there are a couple of pictures as well.
no bs about the link being unsafe, is from MIT, not from military or government agencies.

This is how rocket propulsion work. Are u missing how the propellant is composed by millions of bodies to which 3rd law is applied?

Pay attention cause this is chemistry 101 and physics 101, they don't teach them to welder school apparently.

Hypothesis: solid rocket fuel
Millions of bodies make up the propellant.
There are very strong chemical bonds among them, they act as a single solid body.
Combustion occurs
Combustion reaction destroys strong chemical bonds
Each body is now free to move independently.
Solid propellant has become a gas.
Each particle of that gas is an independent body on which Newton's 3rd law can be applied.
Nozzle accelerates gas.
Nozzle produce a force on gas particles and gas particles produce an equal and opposite force on the nozzle.
Rocket is propelled
No atmosphere involved

Papa, nothing to say about this?

This is how rocket propulsion work. Are u missing how the propellant is composed by millions of bodies to which 3rd law is applied?

For someone who claims to be conversant with fluid mechanics not to have heard of the Continuum Assumption is rather odd...

But for a laughably inept shill-entity it is par for the course.

Quote from: tomfi on November 23, 2015, 04:14:59 AM

This is how rocket propulsion work. Are u missing how the propellant is composed by millions of bodies to which 3rd law is applied?

For someone who claims to be conversant with fluid mechanics not to have heard of the Continuum Assumption is rather odd...

But for a laughably inept shill-entity it is par for the course.

continuum assumption is only use full as a simplification of reality. Would be more correct to model every single molecule and their reciprocal interaction but u would end up with to many variables for practical calculations.
 Btw continuum assumption is only valid for low value of the Knudsen's number.

Quote from: tomfi on November 23, 2015, 04:14:59 AM

This is how rocket propulsion work. Are u missing how the propellant is composed by millions of bodies to which 3rd law is applied?

For someone who claims to be conversant with fluid mechanics not to have heard of the Continuum Assumption is rather odd...

But for a laughably inept shill-entity it is par for the course.

Sorry Papa. Continuum assumption is a just method of simplifying the modelling for materials. Using the concept of millions of separate particles is what happens in reality but is harder to model.

Would be more correct to model every single molecule and their reciprocal interaction but u would end up with to many variables for practical calculations.

Would it?

Funny how no-one ever does that, though, & just uses continuum mechanics

But whatever; here we go again...

Mainframe's 'tiny billiard balls banging about in a box' analogy rises from the grave.

Speaking of whom; hiya Walter Mitty!

How odd that you should pop up right now...

Still Pretending to be a scientist, are we?

LOL!!!

Quote from: tomfi on November 23, 2015, 02:02:59 AM

Propellant's particles are bodies!!!!!!
If particles of a fluid are not bodies to which Newton 3rd law can be applied how would u explain pressure?

I'm not sure what your point is, but try this:

*Buy a firework rocket.

*Look at it.

*Count the Number of objects it is.

If the Number you count to is higher than One, then there's not much to be done for you.

Papa Legba claims to work in construction yet doesn't understand the concept of a bill of materials.

Aaand markjo gets top post in again, with a typically inane shitpost.

You lot have given up even trying, haven't you?

Sad bastards.

Anyhoo; I'll just leave this here for easy reference & the education of Walter 'mainframes' Mitty:

To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.

Quote from: tomfi on November 23, 2015, 04:56:41 AM

Would be more correct to model every single molecule and their reciprocal interaction but u would end up with to many variables for practical calculations.

Would it?

Funny how no-one ever does that, though, & just uses continuum mechanics

But whatever; here we go again...

Mainframe's 'tiny billiard balls banging about in a box' analogy rises from the grave.

Speaking of whom; hiya Walter Mitty!

How odd that you should pop up right now...

Still Pretending to be a scientist, are we?

LOL!!!

Continuum assumption is more practical for fast calculations but... Have u ever heard of computational fluid dynamics CFD and finite element model FEM. They basically divide your object into many parts,  continuum then becomes a union of discrete elements. This is done in order to give a better approximation of reality and allows  more precise calculations

Have u ever heard of computational fluid dynamics CFD and finite element model FEM.

Yes, & it's still based on the continuum assumption...

Do you have a point?

Or are you, as I suggested you would earlier, simply working your way towards filling a whole post with Navier-Stokes equations in order to really stink the place out?

Yes, & it's still based on the continuum assumption...

Emphasis on assumption! It's an assumption they use to make modelling simpler. Reality shows that everything (including fluids we are discussing) is made from many discrete particles.

The concept of tiny billiard-ball molecules banging off each other has no place in Fluid Mechanics.

So stop trying to crow-bar it in there so you cann hazz spayze-shippz.

Body of rocket

Propellant

That's two objects. Why are we going backwards?

Body of rocket

Propellant

That's two objects. Why are we going backwards?

So the propellant of an unlit rocket is outside the body of the rocket?

Idiot.

Still; strange how you & Walter Mitty seem to always come as a pair, isn't it?

LOL!!!

No, it isn't!

Quote from: tomfi on November 23, 2015, 05:33:49 AM

Have u ever heard of computational fluid dynamics CFD and finite element model FEM.

Yes, & it's still based on the continuum assumption...

Do you have a point?

Or are you, as I suggested you would earlier, simply working your way towards filling a whole post with Navier-Stokes equations in order to really stink the place out?

of course i have a point.
fem uses continuum mechanics, in which u need to solve less equations, in a very small volume in order to represent better the reality which is not made up by continuum material but by atom and molecules.
think of concrete. continuum mechanics approximates it as a single material, fem uses the continuum mechanics model of cement and aggregate in order to reproduce the concrete as the interaction of every single grain of cement and aggregate.

u prefer continuum mechanics. no problem: the mass flow of propellant gains speed through the nozzle, this means that thrust is produced since mass flow*velocity=force.
do u want proper math, as u prefer:
http://web.mit.edu/16.unified/www/SPRING/propulsion/Propulsion.pdf

u're not scared by intregals and derivates, right?
I'm sure u've been taught integrals and derivatives while u're following the course "how not to hit your thumb with the hammer".

Quote from: sokarul on November 23, 2015, 05:59:35 AM

Body of rocket

Propellant

That's two objects. Why are we going backwards?

So the propellant of an unlit rocket is outside the body of the rocket?

Idiot.

Still; strange how you & Walter Mitty seem to always come as a pair, isn't it?

LOL!!!

No, it isn't!

Lol

Objects can touch each other and still be separate objects.

Lol

Quote from: sokarul on November 23, 2015, 05:59:35 AM

Body of rocket

Propellant

That's two objects. Why are we going backwards?

So the propellant of an unlit rocket is outside the body of the rocket?

Who said that the second body needs to be outside the first? 

Objects can touch each other and still be separate objects.

Great - I get two fireworks for the price of one!

thrust is produced since mass flow*velocity=force.

LOL!!!

What a Loser.

Who said that the second body needs to be outside the first?

Dunno; a gynaecologist maybe?

GTFO, Shitpost King!

Quote from: tomfi on November 23, 2015, 06:10:48 AM

thrust is produced since mass flow*velocity=force.

LOL!!!

What a Loser.

why i'm a loser?
do u mean that mass flow*velocity is not a force?!?

why i'm a loser?

You don't even know, do you, poor sod...

That's why you're a Loser I guess.

Quote from: tomfi on November 23, 2015, 07:37:31 AM

why i'm a loser?

You don't even know, do you, poor sod...

That's why you're a Loser I guess.

am I a loser cause I've said something wrong?

am I a loser cause I've said something wrong?

No; it's a bit more obvious than that.

But at least you've admitted you ARE a Loser...

That's a start!

Now the healing process can begin.

Quote from: tomfi on November 23, 2015, 08:00:50 AM

am I a loser cause I've said something wrong?

No; it's a bit more obvious than that.

But at least you've admitted you ARE a Loser...

That's a start!

Now the healing process can begin.

so i'm right and you're wrong, thank u for your admission.

now u can't stop playing with the quote.
really dude? that's all u've got? u have no valid argument against what i've said?
and u were claiming i'm the one using shill tactics 101. all u have done in the last ten pages is evanding and insulting.
little Liar I challenge u to bring up evidence against my claims...
 make clear to everybody on this forum that i know nothing about rocket and that u're right, come on
u've got none cause u're ignorant?
next time debate whether it's better the hammer or the nail gun, that's more on your level

make clear to everybody on this forum that i know nothing about rocket and that u're right

I already have done.

& if they've been paying close attention I proved you're a Shill too.

Toodle-Pip, Loser; I'm off to grate some cheese for my pasta.

Using your unique interpretation of Newton's 3rd the Cheese can be both itself AND the Grater...

Extra Cheese all round!

Quote from: tomfi on November 23, 2015, 08:17:23 AM

make clear to everybody on this forum that i know nothing about rocket and that u're right

I already have done.

& if they've been paying close attention I proved you're a Shill too.

Toodle-Pip, Loser; I'm off to grate some cheese for my pasta.

Using your unique interpretation of Newton's 3rd the Cheese can be both itself AND the Grater...

Extra Cheese all round!

 yeah is unique, sure..... execpt is the one u should have been taught in chemistry and physics.
btw if my knowledge is so fundamentally wrong, how come i can rely on MIT professor to support my claim and u can rely on welders?
http://web.mit.edu/16.unified/www/SPRING/propulsion/Propulsion.pdf

dude, suggestion, just stop answering.
 i won't let u get away with this. too many people have dedicated their lives to achieve flight and space flight, i just won't let u saying BS about their lives' work.
just stop answering this thread, i don't care about solar eclipses and other stuff, u can continue trolling on every other thread on this forum, just stop answering in this one... just a suggestion

The concept of tiny billiard-ball molecules banging off each other has no place in Fluid Mechanics.

So stop trying to crow-bar it in there so you cann hazz spayze-shippz.

In breaking news Papa Legba does not accept reality......

Quote from: markjo on November 23, 2015, 06:53:23 AM

Who said that the second body needs to be outside the first?

Dunno; a gynaecologist maybe?

GTFO, Shitpost King!

If I'm the shipost king, what does that make you?  God Emperor of the Shitpost?