[garygreen]

Exhaust particles cannot be accelerated out of the nozzle without the application of a force, and the application of that force must correspond to a force of equal magnitude in the opposite direction.

Why must the exhaust of particles correspond to a force of equal magnitude in empty space? That does not make any sense.  What makes sense is if the particles are hitting something, pushing the entire vehicle system, exhaust and all, forward.

It makes perfect sense.  It's just Newton's Third Law and a little bit of deduction. If object A exerts a force on (accelerates) object B, then object A will experience a force of equal magnitude and in the opposite direction.  Therefore, if object B is observed accelerating in one direction, then we can be sure that object A was accelerated in the other.

The notion that pushing something applies a force to you in the opposite direction of the thing you pushed is also Newton's Third Law.  You can't have it both ways.

It also doesn't make sense to me that a wall could push a fluid in the way you describe.  How does a wall push a column of air that is flowing against it, keep the shape of the column, and then use that column to push a different wall, also without disrupting the shape of the column? 

The exhaust is a high pressure fluid. It is connected to the vehicle. As the exhaust encounters resistance, that resistance will trickle back to the vehicle.

You're just asserting all of this without warrant or investigation.  For one thing, the exhaust isn't always a high pressure fluid.  Airplanes fly using the same law of motion yet do not rely on high pressure fluids.  The air coming from the balloon in your video is not a high pressure fluid.  Water only exerts high pressure at depth (there's no such thing as high or low pressured water...it doesn't compress).  Plus, gasses actually lose pressure once they leaves the nozzle and begin expanding.

I also don't know what it means for "resistance" to "trickle back to the vehicle."  Are you thinking of it like doing a pushup?  Like how the floor applies a force to my hand that, connected to my wrist, arms, shoulder, etc, moves my body upward?  If so, I don't think fluids are very analogous to arms.  Arms are solid and mechanically attached to hands and shoulders.  Fluids and rockets are not similarly attached once the fluid leaves the rocket.

It's like one of those water jetpacks. The jetpack does not rise in altitude until the water has hit the surface. The high pressured water is connected to the jetpack as a single entity. Resistance on the water results resistance on the jetpack. The tension ripples upwards through the whole entity.

Ironically, water jetpacks are an excellent demonstration that I'm correct here.  For one thing, see my previous point about water and pressure.  For another, check out some videos of them on YouTube.  They don't at all correspond to your description.  The water isn't in some contiguous stream that pushes the jetpack up like an arm raises a shoulder.  Not even close.

Take this photo as an example.  There is no sense in which the water droplets splashing into the ocean below are still connected to the jetback in any way.  The exchange of forces between the droplets and the ocean has no effect or impact on the jetpack itself.  It's just the acceleration of water in one direction from the pack (which applies and equal and opposite force on the pack) that supplies the lift. 

[Tom Bishop]

In that photo the tension/resistance is rippling up the water stream in waves at the speed of sound. Imagine if we had a string stretched taught for 3000 miles across the USA, between California and New York. If we pull the string in California, will New York feel it instantly? No, it takes time for the message to be communicated.

In the jetpack photo there are trillions of streams of water in communication with the surface and resistance of the air. Some parts may not have a constant connection, and some may be disconnected below at some points, but the water is rushing so fast and in such quantity that there is always some kind of communication of resistance communicated to the wearer. A small gap in the water means only that the wearer will dip a little once that gap of resistance is communicated up to the jetpack.

[huh?]

While I understand the simple logic that something has to push off something else. It is simply not true

You need not take any ones word for it because you can prove it yourself through experiment.

The force of the exhaust pushes both directions at the same time.

We all know that the air gets thinner as you gain altitude but airplanes can go faster higher. If air at 30,000 ft is 1/3 the density of air at sea level
than a plane should only be able to go 1/3 as fast. Also a plane traveling at 30,000 ft would only be 1/3 as fuel efficient.  (although that is not exactly right because there is also less friction with thinner air)

The world speed record for a plane is the SR-71 and it flew much higher.

The ISS can be observed flying over and through triangulation it's distance and speed can be determined it is moving about 17,000 mph and about 240 miles above the surface and completes an orbit every 92 minutes.
   

[garygreen]

In that photo the tension/resistance is rippling up the water stream in waves at the speed of sound. Imagine if we had a string stretched taught for 3000 miles across the USA, between California and New York. If we pull the string in California, will New York feel it instantly? No, it takes time for the message to be communicated.

In the jetpack photo there are trillions of streams of water in communication with the surface and resistance of the air. Some parts may not have a constant connection, and some may be disconnected below at some points, but the water is rushing so fast and in such quantity that there is always some kind of communication of resistance communicated to the wearer. A small gap in the water means only that the wearer will dip a little once that gap of resistance is communicated up to the jetpack.

If you insist.  This reads like gibberish.  Of all the things about this that make absolutely zero sense to me, the biggest is that I don't understand how an object could push off of water with water.  You're just asserting continuously and without warrant that fluids behave like solid objects.  Water doesn't behave like rope.



This doesn't look anything like what you've described, even if your description had managed to use terms like resistance and tension correctly.

Also, what about the balloon car in your video?  You consider warm air gently escaping from a balloon to be a high pressure fluid?

And you still haven't addressed the fact that your description also requires Newton's Third Law to be true.  No matter how you dice it, every time you talk about a rocket pushing off of something to move, you're evoking Newton's Third.

[model 29]

I think this could be a subject worth further investigation. I would like to see one more experiment tried, with a barrier that is not attached to the vehicle. For instance, what would happen if he put his outstretched palm following the exhaust pipe at a distance of two inches as the car sped away? Would the car speed up since his hand is more solid than the atmosphere? I think that might be more conclusive evidence.

Are there any other ways which can prove or disprove his theory which seems to suggest that Newton's Third Law is false?

Note how much force is pushing back against your hand while operating a garden hose nozzle.  Now place that same nozzle in a bucket of water.  Does the force increase or decrease?

[andruszkow]

The exhaust is a high pressure fluid. It is connected to the vehicle. As the exhaust encounters resistance, that resistance will trickle back to the vehicle.

It's like one of those water jetpacks. The jetpack does not rise in altitude until the water has hit the surface. The high pressured water is connected to the jetpack as a single entity. Resistance on the water results resistance on the jetpack. The tension ripples upwards through the whole entity.

The exhaust is NOT a high pressure fluid. The fuel is 2 compressed fluids, where one is an oxidizer.

The fuel is fed into a combustion chamber. The combustion chamber is closed in the top, fed with fuel through nozzles in the sides, and open in the bottom (the rockets nozzle). When the combustion of the fluids occur, it expands under extreme conditions multiple of times, thus filling the combustion chamber with exhaust gas (expansion = energy).

Now, the exhaust exists the nozzle at the bottom of the chamber, pushing against the top of the chamber (action/reaction), which ultimately is the thrust that is pushing the rocket, since the combustion chamber is rigidly connected to the rest of the vessel.

So yes, rockets do very much work in space.

[andruszkow]

I think this could be a subject worth further investigation. I would like to see one more experiment tried, with a barrier that is not attached to the vehicle. For instance, what would happen if he put his outstretched palm following the exhaust pipe at a distance of two inches as the car sped away? Would the car speed up since his hand is more solid than the atmosphere? I think that might be more conclusive evidence.

Are there any other ways which can prove or disprove his theory which seems to suggest that Newton's Third Law is false?

Note how much force is pushing back against your hand while operating a garden hose nozzle.  Now place that same nozzle in a bucket of water.  Does the force increase or decrease?

Do we care that the density of water is 784 times greater than air at sea level?

[andruszkow]

In that photo the tension/resistance is rippling up the water stream in waves at the speed of sound. Imagine if we had a string stretched taught for 3000 miles across the USA, between California and New York. If we pull the string in California, will New York feel it instantly? No, it takes time for the message to be communicated.

In the jetpack photo there are trillions of streams of water in communication with the surface and resistance of the air. Some parts may not have a constant connection, and some may be disconnected below at some points, but the water is rushing so fast and in such quantity that there is always some kind of communication of resistance communicated to the wearer. A small gap in the water means only that the wearer will dip a little once that gap of resistance is communicated up to the jetpack.

This is scientifically very, very unsound claims, I have to say.

[markjo]

The exhaust is NOT a high pressure fluid

Actually, it is.  In physics, both gasses and liquids are considered to be fluids (along with plasma and plastic solids, to some extent).  So rapidly expanding, hot exhaust gasses are, indeed, fluid in nature.

The fuel is 2 compressed fluids, where one is an oxidizer.

Close, but not quite.  In liquid fuel rockets, the fuel and oxidizer are (as the name suggests) liquids being fed under pressure.  Unlike gasses, most liquids don't compress very well.

[andruszkow]

The exhaust is NOT a high pressure fluid

Actually, it is.  In physics, both gasses and liquids are considered to be fluids (along with plasma and plastic solids, to some extent).  So rapidly expanding, hot exhaust gasses are, indeed, fluid in nature.

The fuel is 2 compressed fluids, where one is an oxidizer.

Close, but not quite.  In liquid fuel rockets, the fuel and oxidizer are (as the name suggests) liquids being fed under pressure.  Unlike gasses, most liquids don't compress very well.

I stand corrected. It's a language barrier - Liquids and fluids are more or less the same translated to my language, so I get them mixed up. However, the point of my reply doesn't change at all.

[mister bickles]

rockets quite obviously work....even @ great heights....as seen by these recent, Y-tb vids...

how-ever....do they work in space ?  (as commonly understood....viz "outer space")

i/no-one's ever been up there to prove they do!
ii/they could never penetrate through the upper layers of the thermo-sphere any-way
iii/they won't work in a vacuum ......and there's no real proof that they can
(assuming, of course, that the very upper regions of 'the atmosphere' are a vacuum, as such....again....no-one's been up that high)

[huh?]

As far as I know the moon is in outer space so: Yes -people have been there.

The thermosphere is not some kind of impenetrable zone and a lot of rockets have gone through it

Lots of proof that they work in a vacuum from many probes and satellites that have gone and are currently in it.

[andruszkow]

i/no-one's ever been up there to prove they do!

Plenty of probes has been up there to prove this. If you chose to disregard all the evidence and facts as manipulated, then there's not really anything one can tell you to prove otherwise. I guess you have to make an effort of disproving the known facts instead. Everybody can do it, it's just a matter of budget.

ii/they could never penetrate through the upper layers of the thermo-sphere any-way

Wait, what? I didn't know the thermosphere was a impenetrable titanium shield.

iii/they won't work in a vacuum ......and there's no real proof that they can
(assuming, of course, that the very upper regions of 'the atmosphere' are a vacuum, as such....again....no-one's been up that high)

There's plenty of proof that they do. This have been proven numerous times, and been tested to death in vacuum chambers on the Earth. Again, this is something which is possible for everyone, it's just a matter of budget.