ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 17th April 2019, 09:47 AM   #41
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
I wonder if they performed the movie Gravity in space as well
If you want to discuss how motion pictures are made, there is probably a suitable place at this forum to do so. And I'm sure there are plenty of people with plenty of experience in practical special effects and cinematic visual effects to answer any questions you may have.

You have presented a physics proof you say establishes that rockets cannot provide momentum thrust in a vacuum. You have failed to address the several people who have shown the simple error you've made. It is unclear what relevance cinematography has to that proof.

You have lately asserted that no "unedited video of rockets in space" exists. You have failed to show how that is relevant to your proof. You have even failed to show that your assertion is true. It would help us understand your argument if you would, in addition to blurting out these claims, show how they tie into some overall conclusion.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:49 AM   #42
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
People need to realize that gas expands freely into a vacuum
That was discussed when I explained pressure thrust. That's the second term in the equation you proposed to disprove. But you need to understand that a rocket employs a nozzle that converts chamber pressure to linear velocity. The pressure in the chamber is produced by thermodynamic means. It is this velocity that resides in the momentum term of your equation. You derived the wrong value for that velocity in your proof by conflating it with mass flow rate. The static pressure that remains after this expansion is what produces vacuum thrust.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:51 AM   #43
dann
Philosopher
 
Join Date: Feb 2004
Posts: 7,665
Originally Posted by Gingervytes View Post
When wind blows on the back of your head, why donít you feel the air in front of you push off your face as it moves away from you?

If the air 'pushing off your face' came out of a rocket, you would feel it!
__________________
/dann
"Stupidity renders itself invisible by assuming very large proportions. Completely unreasonable claims are irrefutable. Ni-en-leh pointed out that a philosopher might get into trouble by claiming that two times two makes five, but he does not risk much by claiming that two times two makes shoe polish." B. Brecht
"The abolition of religion as the illusory happiness of the people is required for their real happiness. The demand to give up the illusion about its condition is the demand to give up a condition which needs illusions." K. Marx
dann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:53 AM   #44
sts60
Illuminator
 
sts60's Avatar
 
Join Date: Jul 2007
Posts: 3,190
Originally Posted by sts60 View Post
Indeed, why would video be the observational standard of evidence that rockets work in space? That makes little sense to me, but then again I work in this field.
Originally Posted by Gingervytes View Post
I wonder if they performed the movie Gravity in space as well
Nope. Would you care to address my question? Or my earlier comments?
sts60 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:53 AM   #45
dann
Philosopher
 
Join Date: Feb 2004
Posts: 7,665
Originally Posted by Gingervytes View Post
I wonder if they performed the movie Gravity in space as well

There is such a thing as fiction, so everything is obviously fiction ...
__________________
/dann
"Stupidity renders itself invisible by assuming very large proportions. Completely unreasonable claims are irrefutable. Ni-en-leh pointed out that a philosopher might get into trouble by claiming that two times two makes five, but he does not risk much by claiming that two times two makes shoe polish." B. Brecht
"The abolition of religion as the illusory happiness of the people is required for their real happiness. The demand to give up the illusion about its condition is the demand to give up a condition which needs illusions." K. Marx
dann is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:55 AM   #46
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
Originally Posted by dasmiller View Post
I think many of us understand that just fine. Can you elaborate on the significance for rocket propulsion?
The video demonstrates that there is no equal and opposite force from gas movement due to pressure gradient force. Itís just that you canít handle the truth
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:57 AM   #47
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by Gingervytes View Post
The video demonstrates that there is no equal and opposite force from gas movement due to pressure gradient force. Itís just that you canít handle the truth
Are you saying that gas won't accelerate due to a pressure gradient? Or that moving gas doesn't have momentum?
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:59 AM   #48
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
The video demonstrates that there is no equal and opposite force from gas movement due to pressure gradient force.
The momentum of the rocket exhaust doesn't derive from a "pressure gradient force" in the way your proof describes. The propellants enter the chamber at a certain mass flow rate. The pressure of those propellants is increased dramatically in the chamber by vigorous combustion. The de Laval nozzle converts that pressure into linear flow. The velocity of that linear flow is Ve. It is not the velocity you estimated from "pressure gradient force." The mass flow rate at the exit plane is the same as at the engine injector, but since the volume of the propellants is now vastly increased, it must leave at a faster velocity.

Quote:
It’s just that you can’t handle the truth
It's more like you don't understand the refutation of your proof. Do you realize that at least two of the people who are attempting to educate you on these points are professional rocket scientists?

Last edited by JayUtah; 17th April 2019 at 10:00 AM.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 09:59 AM   #49
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
Originally Posted by dann View Post
There is such a thing as fiction, so everything is obviously fiction ...
Therefore edited video could potentially be fiction and thus unreliable
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:00 AM   #50
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by JayUtah View Post
Do you realize that at least two of the people who are attempting to educate you on these points are professional rocket scientists?
At least 3
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:01 AM   #51
The Greater Fool
Illuminator
 
The Greater Fool's Avatar
 
Join Date: Feb 2007
Location: Scottsdale, AZ, USA, North America, Earth, Sol, Milky Way
Posts: 3,817
Originally Posted by Gingervytes View Post
Therefore edited video could potentially be fiction and thus unreliable
How long must the unedited video be for you to accept it's validity?
__________________
- "Who is the greater fool? The fool? Or the one arguing with the fool?" [Various; Uknown]
- "The only way to win is not to play." [Tsig quoting 'War Games']
The Greater Fool is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:01 AM   #52
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
Originally Posted by JayUtah View Post
The momentum of the rocket exhaust doesn't derive from a "pressure gradient force" in the way your proof describes. The propellants enter the chamber at a certain mass flow rate. The pressure of those propellants is increased dramatically in the chamber by vigorous combustion. The de Laval nozzle converts that pressure into linear flow. The velocity of that linear flow is Ve. It is not the velocity you estimated from "pressure gradient force." The mass flow rate at the exit plane is the same as at the engine injector, but since the volume of the propellants is now vastly increased, it must leave at a faster velocity.



It's more like you don't understand the refutation of your proof. Do you realize that at least two of the people who are attempting to educate you on these points are professional rocket scientists?
Doesnít matter how you release the pressure, gas always expands freely in a vacuum
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:03 AM   #53
sts60
Illuminator
 
sts60's Avatar
 
Join Date: Jul 2007
Posts: 3,190
Originally Posted by JayUtah View Post
That was discussed when I explained pressure thrust. That's the second term in the equation you proposed to disprove. But you need to understand that a rocket employs a nozzle that converts chamber pressure to linear velocity. The pressure in the chamber is produced by thermodynamic means. It is this velocity that resides in the momentum term of your equation. You derived the wrong value for that velocity in your proof by conflating it with mass flow rate. The static pressure that remains after this expansion is what produces vacuum thrust.
Although Jay and most regulars are well aware, it's also worth pointing out explicitly that you donít even need a proper nozzle to generate thrust in space (or on Earth). You just need a hole for the propulsive mass to get out. Itís a lousy way to do it - very inefficient - but it will generate thrust in the opposite direction. The numerous SF scenarios of a stranded spacefarer cracking open an oxygen tank, or opening a small hole in his suit, or for that matter firing a gun in the direction opposite to that desired, all more or less work - itís controlling oneís thrust vector thatís the problem, not actually generating thrust.
sts60 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:04 AM   #54
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by Gingervytes View Post
Doesn’t matter how you release the pressure, gas always expands freely in a vacuum
But it can be constrained from expanding in all directions. A non-uniform expansion generates a net force on whatever's constraining it.
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:06 AM   #55
Horatius
NWO Kitty Wrangler
 
Horatius's Avatar
 
Join Date: May 2006
Posts: 27,111
Originally Posted by Gingervytes View Post
Why is there no unedited video of a rocket in space?


I suppose you're going to quibble about if this counts as "in space":


https://www.youtube.com/watch?v=9HQfauGJaTs
__________________
Obviously, that means cats are indeed evil and that ownership or display of a feline is an overt declaration of one's affiliation with dark forces. - Cl1mh4224rd
Horatius is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:08 AM   #56
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
Doesnít matter how you release the pressure, gas always expands freely in a vacuum
Yes, and that was covered under the discussion of pressure thrust. The static pressure of the exhaust as it expands freely acts preferentially on the spacecraft, because the spacecraft is preferentially on one side of the expanding gas volume.

However, how you release the pressure matters a great deal in how much momentum there is in it. And that's where the momentum term in your equation comes from. Specifically, if you release the pressure in a way that creates a unidirectional uniform flow, that flow has net momentum in one direction, whereas the net momentum in an expanding volume of gas is zero.

You don't get to ignore the effect of the de Laval nozzle just because it is inconvenient to your proof or your understanding of how it was refuted. Pressure released through such a nozzle creates momentum in one direction. Newton's law says there must be equivalent but opposite momentum, and that is what results in thrust.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:10 AM   #57
bknight
Graduate Poster
 
bknight's Avatar
 
Join Date: Apr 2017
Location: Houston, Texas
Posts: 1,543
Originally Posted by Horatius View Post
I suppose you're going to quibble about if this counts as "in space":


https://www.youtube.com/watch?v=9HQfauGJaTs
Well since rockets don't work in space there was no landing on the Moon and subsequent takeoff.
bknight is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:12 AM   #58
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by sts60 View Post
You just need a hole for the propulsive mass to get out.
Correct. In fact, solid-fueled motors generally use conical nozzles as a compromise between ideal expansion and the methods used to construct the nozzles out of materials that can take the heat. I don't mean to conflate the optimization of the nozzle geometry with the purer physics of gas expanding in a container with an opening in it.

Originally Posted by dasmiller View Post
But it can be constrained from expanding in all directions. A non-uniform expansion generates a net force on whatever's constraining it.
A hole in one end of the thrust chamber creates non-uniform expansion and a net force. Constraining the expansion to result in a linear flow optimizes and maximizes that effect.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:13 AM   #59
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by bknight View Post
Well since rockets don't work in space there was no landing on the Moon and subsequent takeoff.
That's where I think we're going with this. He's probably about to argue that there is no such thing as space flight in general, including the Apollo missions.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:14 AM   #60
sts60
Illuminator
 
sts60's Avatar
 
Join Date: Jul 2007
Posts: 3,190
Originally Posted by Gingervytes View Post
The video demonstrates that there is no equal and opposite force from gas movement due to pressure gradient force. Itís just that you canít handle the truth
Your garbled interpretation of Newtonian mechanics aside, why would video be better than tracking data, or radar, or onboard inertial telemetry, the primary ways we (people who launch and operate spacecraft for a living) actually measure the response of spacecraft to rocket operation in space?

Bonus question: you do understand that NASA did not invent the equations of motion, nor the equations of rocketry, and that spacecraft are routinely operated by civil, military, and commercial organizations from many nations? Right?
sts60 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:16 AM   #61
Horatius
NWO Kitty Wrangler
 
Horatius's Avatar
 
Join Date: May 2006
Posts: 27,111
Originally Posted by JayUtah View Post
That's where I think we're going with this. He's probably about to argue that there is no such thing as space flight in general, including the Apollo missions.


It's actually kind of refreshing to have a proper old-school CTist posting again. Demanding video of rockets in space, but likely to reject the video as faked because rockets can't work in space.
__________________
Obviously, that means cats are indeed evil and that ownership or display of a feline is an overt declaration of one's affiliation with dark forces. - Cl1mh4224rd
Horatius is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:18 AM   #62
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by JayUtah View Post
A hole in one end of the thrust chamber creates non-uniform expansion and a net force. Constraining the expansion to result in a linear flow optimizes and maximizes that effect.
I was going to start with popping a balloon next to a steel plate . . .
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:24 AM   #63
Hans
Philosopher
 
Hans's Avatar
 
Join Date: May 2007
Posts: 7,884
Originally Posted by JayUtah View Post
Wow, this guy is foaming all over the forum trying to discredit NASA. This should be entertaining.
Sorry Jay but the term 'foaming' is incorrect it should be 'sloshing about in a mad an inept rage'.
Hans is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:24 AM   #64
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by dasmiller View Post
I was going to start with popping a balloon next to a steel plate . . .
Slow down there, Von Braun.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:25 AM   #65
Steve
Philosopher
 
Steve's Avatar
 
Join Date: May 2005
Posts: 5,039
C'mon all you science guys! There is a video! This trumps all of your sciencey mumbo jumbo. Rockets don't work and never have. You just have to believe hard enough.
__________________
Caption from and old New Yorker cartoon - Why am I shouting? Because I'm wrong!"
Steve is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:29 AM   #66
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Hans View Post
Sorry Jay but the term 'foaming' is incorrect it should be 'sloshing about in a mad an inept rage'.
Yeah, that's kind of my point. One of the first things he did here was jump over to the religion section and, in a thread about atheism (now happily cleansed of the distraction), shout out of the blue that belief in NASA and space was a religion. Someone that intent on a crusade is probably not going to get the physical science right, or have any interest in being corrected on it.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:31 AM   #67
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
why Is there no opposite force when smoke rises up. Shouldnít the smoke from a campfire push off the ground?
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:33 AM   #68
sts60
Illuminator
 
sts60's Avatar
 
Join Date: Jul 2007
Posts: 3,190
Originally Posted by Gingervytes View Post
why Is there no opposite force when smoke rises up. Shouldnít the smoke from a campfire push off the ground?
How about answering the questions and rebuttals already provided you?
sts60 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:34 AM   #69
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
why Is there no opposite force when smoke rises up. Shouldnít the smoke from a campfire push off the ground?
Smoke is an aerosol entrained in the ambient. Its motion has nothing to do with rockets. And if your contention is that smoke rises and should be analogous to rocket exhaust, why would an equal an opposite reaction in the Newtonian sense want to make the campfire also rise? You really are stumbling over basic ideas in Newtonian dynamics.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:36 AM   #70
catsmate
No longer the 1
 
catsmate's Avatar
 
Join Date: Apr 2007
Posts: 20,243
Originally Posted by Gingervytes View Post
Rockets cannot propel in the vacuum of space.
Yes they can.
__________________
As human right is always something given, it always in reality reduces to the right which men give, "concede," to each other. If the right to existence is conceded to new-born children, then they have the right; if it is not conceded to them, as was the case among the Spartans and ancient Romans, then they do not have it. For only society can give or concede it to them; they themselves cannot take it, or give it to themselves.
catsmate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:37 AM   #71
bknight
Graduate Poster
 
bknight's Avatar
 
Join Date: Apr 2017
Location: Houston, Texas
Posts: 1,543
Originally Posted by Gingervytes View Post
why Is there no opposite force when smoke rises up. Shouldnít the smoke from a campfire push off the ground?
Non sequitur as there is no constraining "structure" for the campfire.
bknight is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:38 AM   #72
Dr.Sid
Graduate Poster
 
Join Date: Sep 2009
Location: Olomouc, Czech Republic
Posts: 1,895
Yet another case of not understanding basic principles. I don't blame him though. People learn 'action equals reaction', but the implication of the fact are hard to grasp. And not taught well most of the time.
One of the implications for example is, that every closed system maintains its center of gravity. That also applies to rocket in space. You start with rocket full of fuel, standing still in vacuum of space ('standing still' in some frame of reference). You mark position of the enter of gravity of the rocket, including fuel.
Then you fire the rocket. The fuel burns, shoots out of the rocket, and the rocket moves in the opposite direction.
Now, at any time, if you take the rocket (moving in one direction), and the byproducts of the burning (moving in opposite direction), the center of gravity of this system stays still in the same spot in the original frame of reference.
Things like that are IMHO really counter-intuitive. And some could even argue, that rocket indeed does not work, because the system did not move. Just parts of the system did move in opposite direction, compared to some others. The rocket engine is thus not device to move stuff. It's device to expand stuff ;-)
Dr.Sid is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:38 AM   #73
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by Gingervytes View Post
why Is there no opposite force when smoke rises up. Shouldn’t the smoke from a campfire push off the ground?
This is actually a more complicated question than you think. The smoke we see above a campfire isn't in contact with the ground, so it can't push off the ground. When the smoke is first created within the flame, there's a lot of expanding gas so I'd expect that there is some net pressure on the ground.

Do you think there isn't any net pressure on the ground from the expanding gasses in the flame, and if so, why do you think that?

ETA: But the smoke is rising due to buoyancy. Any initial acceleration at the flame would have almost immediately been lost to air drag.
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt

Last edited by dasmiller; 17th April 2019 at 10:39 AM.
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:45 AM   #74
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
You canít prove anything

All you can pick at is that I used nasa. Well I got the equation from NASAís website
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:47 AM   #75
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by dasmiller View Post
When the smoke is first created within the flame, there's a lot of expanding gas so I'd expect that there is some net pressure on the ground.
And, if you want to get picky, some rocket propellant formulations can produce solid species in the exhaust, which are entrained and become part of the exhaust flow.

Quote:
ETA: But the smoke is rising due to buoyancy. Any initial acceleration at the flame would have almost immediately been lost to air drag.
That's where I was going. The dynamics of the ambient fluid completely overwhelm the problem. I was more laughing at his notion that the propulsive force would act to elevate the campfire, not push it downwards. That illustrates a fundamental misunderstanding of the laws of motion, irrespective of our new attempts to reckon it in a macroscale fluid flow.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:49 AM   #76
Gingervytes
Critical Thinker
 
Join Date: Mar 2019
Posts: 283
And gas moving out of the chamber is due to pressure gradient force
Gingervytes is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:50 AM   #77
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
You canít prove anything.
We don't have to. Newton proved it centuries ago. You're literally trying to undermine one of the most well-established principles in elementary physics.

Quote:
All you can pick at is that I used nasa.
No, that's not all we can pick at. We can pick at your abysmal knowledge of basic physics. And, given that you're falling all over yourself to throw shade on NASA elsewhere in the forum, we can wonder whether that is biasing you to the facts.

Quote:
Well I got the equation from NASAís website
That doesn't mean NASA invented it.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:51 AM   #78
JayUtah
Penultimate Amazing
 
JayUtah's Avatar
 
Join Date: Sep 2011
Posts: 17,184
Originally Posted by Gingervytes View Post
And gas moving out of the chamber is due to pressure gradient force
And you're wrong about what creates that pressure, how much of it is there is, and what can be done with that pressure in order to create momentum. This has been explained to you at length. Your inability to grasp it doesn't make elementary physics go away.
JayUtah is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:51 AM   #79
dasmiller
Just the right amount of cowbell
 
dasmiller's Avatar
 
Join Date: Oct 2008
Location: Well past Hither, looking for Yon
Posts: 6,194
Originally Posted by Gingervytes View Post
You canít prove anything

All you can pick at is that I used nasa. Well I got the equation from NASAís website
Do you believe that rockets can generate thrust in an atmosphere? If so, why is it possible with an atmosphere but impossible without?

Now for my balloon & steel plate:

Imagine you have a big vacuum with a balloon sitting just to the left of a big vertical steel plate. Now, pop the balloon. Will the expanding gas exert any net force on the steel plate?
__________________
"In times of war, we need warriors. But this isn't a war." - Phil Plaitt
dasmiller is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 17th April 2019, 10:51 AM   #80
sts60
Illuminator
 
sts60's Avatar
 
Join Date: Jul 2007
Posts: 3,190
Originally Posted by Gingervytes View Post
You canít prove anything
Well, actually, your proof was explicitly found to be incorrect. And numerous counter examples to your claim were provided.

Originally Posted by Gingervytes View Post
All you can pick at is that I used nasa. Well I got the equation from NASAís website
Which you described as essentially belonging to NASA, although as has been repeatedly pointed out the theory was developed long before there was such a thing as NASA. Please donít blame us for your failure to understand this.

You still havenít answered my questions and counterexamples, by the way. Will you?
sts60 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 05:29 AM.
Powered by vBulletin. Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.