People on skateboards.

Witness the reason rab downunder gets blocked so often for his youtube trolling:

Object A is the Rocket + unburnt fuel, Object F is the burning fuel, and Object B is the thousands of pounds of fuel being ejected out the back.

Note that he is trying to tell us that Objects F & B are the exact same thing.

Massive Troll; Massive Fail.

Quote from: rabinoz on December 15, 2015, 11:03:48 PM

You clearly have no understanding of the operation of a choked de Laval nozzle.

Has your convergent/divergent nozzle got a hole in it?

Yes.

Then the gas will simply expand, freely, through that hole, doing no work on the way.

Now back to youtube with you, there must be some flat earth/rocket-fraud videos you haven't trolled yet.

Of course it has a hole in it - could be quite a big one!
You have not shown a hint of knowing anything about  what choked flow actually means, or any idea of supersonic gas flow.
And, I did ask how the de Laval nozzle worked at very low pressure, say 0.0038 Atm, but you can't even answer that. Note that 0.0038 Atm is not a vacuum so your rocket should work happily here.
I just wondered,  how come you know so much more about this stuff than de Laval himself or Robert Goddard?
Either you are one smart cookie or one big kook - which is it?

PS. I didn't notice in the law of conservation of momentum that we needed  Object A,  Object F and Object B anyway.  We just go along with that to keep you happy"!  I suppose somehow the mass of gases is excluded from "the law of conservation of momentum".  I never noticed that in "Philosophiĉ Naturalis Principia Mathematica", but then my Latin is non-existent!

Wrong!!!!
Pressure gradient is the same between 1 bar-vacuum and 2 bar-1bar.
Vacuum doesn't have special property, is just the absence of material

Pretty solid physical description of a vacuum. 

T & P are almost zero. "Nothing special about it, you can just traverse with some propellant"

Voyager "flew around" for what, 30 years?? How much "fuel" did that monster have on board? 

Voyager "flew around" for what, 30 years?? How much "fuel" did that monster have on board? 

Very little. Probably only a tiny amount of pressurized propellant for course corrections.
Once you are moving in space you will need another force to stop you.
In a vacuum it is hard to find anything to stop you.

Quote from: luckyfred on December 15, 2015, 10:47:07 PM

Wrong!!!!
Pressure gradient is the same between 1 bar-vacuum and 2 bar-1bar.
Vacuum doesn't have special property, is just the absence of material

Pretty solid physical description of a vacuum. 

T & P are almost zero. "Nothing special about it, you can just traverse with some propellant"

Voyager "flew around" for what, 30 years?? How much "fuel" did that monster have on board? 

The voyager is a fictional probe to make us believe in a universe.

Anyway back to the rocket propulsion in a vacuum. Anyone care to tell me why they bother using fire in this space vacuum?
What is the point?

Quote

Voyager "flew around" for what, 30 years?? How much "fuel" did that monster have on board? 

Very little. Probably only a tiny amount of pressurized propellant for course corrections.
Once you are moving in space you will need another force to stop you.
In a vacuum it is hard to find anything to stop you.

How does this voyager manage to simply float in this vacuum when gravity is pulling at it, as we are told?
How does it get into outer space away from earth's so called gravitational pull when apparently it's still being spun around it.
Tell me how it catapults away from the Earth?

Quote

Voyager "flew around" for what, 30 years?? How much "fuel" did that monster have on board? 

Very little. Probably only a tiny amount of pressurized propellant for course corrections.
Once you are moving in space you will need another force to stop you.
In a vacuum it is hard to find anything to stop you.

"Course corrections"? You just design a path on a computer, send the thingy up and then you correct the course of it, against what and how exactly? 

Once you are in space the only force working on you is the gravity.

That's why we couldn't get into space. Ever.

So far the chemical reaction of fuel and oxidizer is resulted to be the most practical source of energy for propulsion

So far the chemical reaction of fuel and oxidizer is resulted to be the most practical source of energy for propulsion

Why do they need to be ignited in this near vacuum?

Effects of the gravity of all the planets are not calculated exactly, as everything u have a degree of approximation, u need the possibility to correct errors. U have thrusters to correct the course.
U have gravity, no drag. But u can produce thrust and once u've reached your final orbit I just need a tiny amount of energy to eventually correct the trajectory

Quote from: luckyfred on December 16, 2015, 06:46:25 AM

So far the chemical reaction of fuel and oxidizer is resulted to be the most practical source of energy for propulsion

Why do they need to be ignited in this near vacuum?

The chemical reaction between fuel and oxidizer is called combustion

Quote from: sceptimatic on December 16, 2015, 06:48:25 AM

Quote from: luckyfred on December 16, 2015, 06:46:25 AM

So far the chemical reaction of fuel and oxidizer is resulted to be the most practical source of energy for propulsion

Why do they need to be ignited in this near vacuum?

The chemical reaction between fuel and oxidizer is called combustion

Ok then why do they need  to chemically react to create combustion to propel them in this space vacuum?
Unless you want to play dodge.

But u can produce thrust and once u've reached your final orbit...

How does this work, before the thingy is in "orbit", where is it before? Out of orbit?

How can you move from orbit to orbit? Is there an orbit in between the orbits or what is there?

To create thrust u need to accelerate a mass. To accelerate a mass u need energy.
A practical way to obtain these energy is through combustion which has also the advantage of providing also the mass that is going to be accelerated.
U burn the fuel, that releases energy which is used to accelerate the mass of burnt fuel thus providing thrust

Of course u can move from one orbit to another. U use the thrust to put your object into an orbit intersecting the initial and final orbit

Of course u can move from one orbit to another.

Ah, of course.

U use the thrust to put your object into an orbit intersecting the initial and final orbit

Oh, intersecting orbits? And what if the orbits never intersect? You're stuck in an orbit forever, or "u" use some special JPL-propellant to steer out?

Have you ever been on a carrousel and tried walking inward or outward? 

Quote from: luckyfred on December 16, 2015, 06:53:32 AM

Quote from: sceptimatic on December 16, 2015, 06:48:25 AM

Quote from: luckyfred on December 16, 2015, 06:46:25 AM

So far the chemical reaction of fuel and oxidizer is resulted to be the most practical source of energy for propulsion

Why do they need to be ignited in this near vacuum?

The chemical reaction between fuel and oxidizer is called combustion

Ok then why do they need  to chemically react to create combustion to propel them in this space vacuum?
Unless you want to play dodge.

You might just as well ask why you burn the gasoline in a car's engine.  Because that's how you release the energy stored in the propellant and you need energy to accelerate the combustion gasses that push against the rocket engine.

Orbits are trajectory that can be designed, all u need is enough energy to put your object in the intersecting orbit and then in the final one.

I notice rab downunder avoided addressing this troll-post:

Object A is the Rocket + unburnt fuel, Object F is the burning fuel, and Object B is the thousands of pounds of fuel being ejected out the back.

Note that he is trying to tell us that Objects F & B are the exact same thing.

Here's a hint for you, rab: One, Two, Three.

Remember that!

Not One, Two, Two...

But One, Two, Three.

I believe there is a puppet vampire called Count Von Count on Sesame Street who may be able to help you further should you require it?

...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.

Everything must be solid or superfluid (H, He) under those conditions.

Even if this Mickey Mouse molestation of Newtons work were true, there is no work to be done; every "gas" molecule that exits the nozzle dissepates away into the vast nothingness of space as a solid, almost non-vibrating Rémy...

Orbits are trajectory that can be designed

 

Thanks for this one.

, all u need is enough energy to put your object in the intersecting orbit and then in the final one.

Great physical explanation. Truly astounding.

When talking about satellites the orbit in which it wil travel is designed according to satellite's mission.

https://en.m.wikipedia.org/wiki/Hohmann_transfer_orbit
This is just one example of maneuvers that can be executed to change orbit.

Since physics rely on math and u seem a great expert of physics, can u provide a set of equation showing u need antigravitation or infinite energy to get into orbit around the earth?

When talking about satellites the orbit in which it wil travel is designed according to satellite's mission.

https://en.m.wikipedia.org/wiki/Hohmann_transfer_orbit
This is just one example of maneuvers that can be executed to change orbit.

Since physics rely on math and u seem a great expert of physics, can u provide a set of equation showing u need antigravitation or infinite energy to get into orbit around the earth?

Aah, the transfer orbit! Now, that's clear! And is it a bit stable, such a "transfer orbit"?

From your link:

Hohmann was influenced in part by the German science fiction author Kurd Lasswitz and his 1897 book Two Planets.

Freaky clowns.

Consider a geostationary transfer orbit, beginning at r1 = 6,678 km (altitude 300 km) and ending in a geostationary orbit with r2 = 42,164 km (altitude 35,786 km).

In the smaller circular orbit the speed is 7.73 km/s; in the larger one, 3.07 km/s. In the elliptical orbit in between the speed varies from 10.15 km/s at the perigee to 1.61 km/s at the apogee.

The Δv for the two burns are thus 10.15 − 7.73 = 2.42 and 3.07 − 1.61 = 1.46 km/s, together 3.88 km/s.

And that's it. You've done it! From 300 km to 35,000 km orbit! Defying gravity and nature, jumping orbits! Amazing.

It is interesting to note that this is greater than the Δv required for an escape orbit: 10.93 − 7.73 = 3.20 km/s. Applying a Δv at the LEO of only 0.78 km/s more (3.20−2.42) would give the rocket the escape speed, which is less than the Δv of 1.46 km/s required to circularize the geosynchronous orbit. This illustrates that at large speeds the same Δv provides more specific orbital energy, and energy increase is maximized if one spends the Δv as quickly as possible, rather than spending some, being decelerated by gravity, and then spending some more to overcome the deceleration (of course, the objective of a Hohmann transfer orbit is different).

Who writes this crap? 

Anyhoo; back to the old 'man on skateboard' false analogy...

Can any of you shpayze-tards tell me exactly what each of the elements in this analogy represents when it comes to rocketry?

Thank you please!

Here you go: one geek, one skateboard...

#" class="bbc_link" target="_blank" rel="noopener noreferrer">!

What represents what?

Thank you please!

Quote from: sokarul on December 15, 2015, 06:34:05 PM

Where's your Nobel Prize for proving General Relativity?

What?

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?

Like I said, here in the real world you couldn't find where I was wrong.

But I just posted where you were wrong last (relative to the request).  Which is what you asked for.  And I easily found.
[/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.

Here you go: one geek, one skateboard...

#" class="bbc_link" target="_blank" rel="noopener noreferrer">!

What represents what?

Thank you please!

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.

Are you going to claim he pushes off the air again?

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?

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?

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.