Does Rocketry Work in the Vacuum?

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Re: Does Rocketry Work in the Vacuum?

Postby molodyets on May 5th, 2017, 3:23 pm

I might not have spent the sufficient time to go through all the comments on this thread, but from the hours I did spend, I do not think anyone has properly explained the free expansion idea. This concept has been incorrectly used to claim that rockets cannot work in a vacuum. I am not, however, giving nasa any credibility.

To understand the concept of free expansion, the situation needs to be viewed molecularly, at the boundary of the compressed gas and the vacuum. At these boundaries, 1 side faces the other gas molecules and the other side faces the vacuum. When a molecule bounces off another, in the direction of the vacuum, it flies off into space. For elastic collisions, then no energy is lost and hence no work has been performed. This process will continue, until all the gas has been dispersed. The big but in all of this, is that with rocket propulsion, there is only a limited space (haha) where free expansion is happening. Therefore, this concept cannot be used to discredit rocket propulsion theory in a vacuum.

In a vacuum, if one side of a container is opened and gas is being expelled, there will be a pressure difference between the closed side and the opened side. The acceleration of the container can then be calculated by the momentum of the escaping gas. If the same situation is performed in a fluid medium (gas/liquid/fluidized bed...) there are so many other factors to take into account. That situation is not as simple. A significant difference in a fluid medium is pressure of the medium. In a vacuum, this is zero. If the pressure is greater than zero, it might aid in the propulsion which could explain the decreasing thrust at higher altitudes. This cannot be extrapolated to zero....
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Re: Does Rocketry Work in the Vacuum?

Postby Flabbergasted on May 5th, 2017, 5:01 pm

I think you got it wrong.

molodyets wrote:To understand the concept of free expansion, the situation needs to be viewed molecularly.

The trendy word "molecularly" adds nothing new to the discussion.

molodyets wrote:For elastic collisions, then no energy is lost and hence no work has been performed.

That is a bit hazy. Would you care to explain?

molodyets wrote:The big but in all of this, is that with rocket propulsion, there is only a limited space (haha) where free expansion is happening. Therefore, this concept cannot be used to discredit rocket propulsion theory in a vacuum.

What "limited space" are you referring to? The nozzle? The combustion chamber? If energy has to be transferred to an external medium for propulsion to happen, it makes no difference how many "limited spaces" you create inside the rocket. The conclusion does not follow from the premises.

molodyets wrote:In a vacuum, if one side of a container is opened and gas is being expelled, there will be a pressure difference between the closed side and the opened side.

I am not, however, giving nasa any credibility.

In what way is that different from NASA´s claim that rockets are propelled by recoil (pushing on the roof of the combustion chamber)?

molodyets wrote:A significant difference in a fluid medium is pressure of the medium. In a vacuum, this is zero. If the pressure is greater than zero, it might aid in the propulsion which could explain the decreasing thrust at higher altitudes. This cannot be extrapolated to zero.

I don´t follow you. If pressure is zero in a vacuum (your words), then what is your argument?

By the way, pressure is so low at a mere 50 km altitude that no type of aircraft (that I am aware of) can remain air-borne. The difference between theoretical zero pressure and the actual near-absolute zero pressure in outer space can be dismissed as utterly insignificant. Molecularly speaking.
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Re: Does Rocketry Work in the Vacuum?

Postby molodyets on May 6th, 2017, 5:02 pm

Flabbergasted » May 5th, 2017, 5:01 pm wrote:I think you got it wrong.


You made some good points so I rewrote it for better clarity.

I might not have spent the sufficient time to go through all the comments on this thread, but from the hours I did spend, I do not think anyone has properly explained the free expansion idea. This concept has been incorrectly used to claim that rockets cannot work in a vacuum. I will also attempt to explain why rocket thrust would decrease at higher altitudes. I am not, however, trying to defend NASA.

To understand the concept of free expansion, the situation needs to be viewed at the molecular level, at the boundary of the compressed gas and the vacuum. At these boundaries, 1 side faces the other gas molecules and the other side faces the vacuum. When a molecule bounces off another, in the direction of the vacuum, it flies off into space. No energy is transferred outside the gas/vacuum system, and hence no work has been performed on any other matter. This process will continue, until all the gas has been dispersed. The big but in all of this, is that with rocket propulsion, free expansion is not occurring at the combustion chamber surfaces. Therefore, this concept cannot be used to discredit rocket propulsion in a vacuum.

I agree with the official explanation of why a rocket can work in a vacuum. To convince me completely, I would have to see experimental evidence from a credible source, but I do not consider the people at NASA as a credible source. If one side of a container is opened in a vacuum and gas is being expelled, there will be a pressure difference between the closed side and the opened side. The acceleration of the container should then be calculated by the momentum of the escaping gas. This makes sense to me.

If the same situation occurs in a fluid medium (gas/liquid/fluidized bed...) there are so many other factors to take into account. That situation is not as simple. In the atmosphere, the atmospheric pressure is probably the most significant factor. I suspect that the atmospheric pressure adds to the thrust of the combustion chamber which would explain the decreasing thrust at higher altitudes. As explained above, the thrust cannot be extrapolated to zero outside the atmosphere, but again, only experimental evidence would completely convince me. Considering the large mass of the rocket, however, the thrust might not be sufficient to transport it all the way into space...the reason for all the lies.
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on May 6th, 2017, 9:49 pm

I don't disagree with your conundrum, but I think you are right to assume there is no adequate thrust from rocket chambers. Here is why. I think we are meant to understand the "free expansion of gas" concept in, let's say, at least three problems:

1. There is some difference between "inside" the rocket and "outside" but that delineation is not clear to everyone (or anyone?). It is therefore magical reasoning until the point is clearly discussed. Already we have a problem with the functions of the rocket just by trying to understand the so-called design. Where is the one-way diaphragm? How is this osmosis mechanically controlled at different atmospheric pressures from 1 to 1/2 all the way down to 0?

2. In the case of explosive combusting fuel, you have molecules belonging to that process and the unrelated solids of the chamber. The third party is the atmosphere. In atmosphere, the exploding gas can push already impacted gas between atmospheric gasses and the solid chamber. Without atmosphere, the exploding gas cannot be as impacted from the start. You need greater explosions to begin to simulate one atmosphere's worth of pressure on the exploding gas. This robs the exploding gas of a great deal of the formula that works in Earth's atmosphere "for free", as it were. Just how much the fuel explosions must be "stacked" to attempt to create the same effectiveness is largely in question. I agree that solid experiments must be done to determine this; but at least with language like this the average person can begin to conceive of better ways of phrasing it, and designing experiments. This explosion concept is already a problem because of how an ignition behaves differently with or without air about it.

3. The very point of the reaction (the combustion at the moment the chemicals mix/transform/ignite) will not be determined as much by atmosphere (or lack thereof) as much as the time immediately following the beginning of a reaction process will be. That is to say, the fuel is supposed to be mixed at a specific location (presumably, for durability already "outside" the mysterious osmosis process of the chamber — see: the first problem), at which point the reaction is "released" to do its job in whatever environment is "outside". Unfortunately for NASA's theories of "space travel", the greater time this reaction is "in vacuum", the less and less effective the combustion will be, as you can not only fail to push the explosion against the atmosphere (which would give it more power bouncing around inside this vacuum-exposed chamber) but you cannot even get the molecules to keep as close together to remain a potent pushing force against each other. This may sound like the same argument as the second problem but I think there is an important difference, and that is our knowledge of how explosions react within vs. how they react against a vacuum. In vacuum, the entire force of the explosion is supposed to be this fuel propelling from pure chemical reaction alone what was previously aided by all the forces that ordinarily create the "buoyancy" effect of this vehicle lifting through atmosphere.

The argument NASA makes is that the shape of the thrust cone or the shape of the fuel ejector plus the certain balancing of their fuel and/or their other devices is enough to compensate and adjust for all effects from a whole atmosphere to none at all, while maintaining effectiveness in space for days. To me, without their proofs (and I believe the onus is on them to explain why they fake videos of their so-called achievements in the first place) people just accepting this concept, and accepting the videos as authentic without examination, indicates that we have a great deal of faith (perhaps too much) in the power of NASA to solve issues they themselves admit are too complex for them to explain as simply as I have just done. And I trust you'll understand what I mean when I say that is pretty pathetic of them, coming from a 20-some billion dollar annual budget.
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Re: Does Rocketry Work in the Vacuum?

Postby Intothevoid on May 8th, 2017, 1:15 am

Would it not make more sense to use water as a fuel in the upper stages of a rocket in a vacuum as it easily boils when exposed to said vacuum? Perhaps the "cold" of space prevents it's feasibility :P. On a side note, what stopped the Apollo astroNots from being pushed around by their sublimation cooling apparatus? Where did the vapor and or ice particles from these systems go? I didn't notice any steam or ice coming from their suits.
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Re: Does Rocketry Work in the Vacuum?

Postby kickstones on May 9th, 2017, 9:28 am

hoi.polloi » May 6th, 2017, 9:49 pm wrote: To me, without their proofs (and I believe the onus is on them to explain why they fake videos of their so-called achievements in the first place) people just accepting this concept, and accepting the videos as authentic without examination.


Hoi, the below video (1983: STS-8 Challenger (NASA) uploaded by the International Astronautical Federation) has had recent examination and a few folk have not accepted its authenticity, namely the scene at 3:28 and head right of the shuttle. One explanation, put forward in the comments section, is that it is a recording off a TV set and the face is a refection from that, another explanation is there are giants in space, maybe NASA could clarify?

https://www.youtube.com/watch?v=ZJw5lE9089o


full link: http://www.youtube.com/watch?v=ZJw5lE9089o
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Re: Does Rocketry Work in the Vacuum?

Postby simonshack on May 9th, 2017, 10:52 am

*
Thanks for the find, Kickstones - what a 'classic'. I guess that's what you would call "in-your-face" fakery. :P

However, there's something even MORE "in-your-facey" about these silly NASA productions: the commentary of the same.

At the 14:35 mark (of above-embedded video), the speaker/actornaut throws THIS lame line at our faces (commenting on the ubercrappy "Shuttle-night-landing-filmed-with-infrared-camera") :

"We defy Hollywood to match this sequence". :rolleyes:

Who writes this stuff? Well, "Hollywood" I presume. -_-
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Re: Does Rocketry Work in the Vacuum?

Postby brianv on May 9th, 2017, 12:48 pm

simonshack » May 9th, 2017, 10:52 am wrote:*
Thanks for the find, Kickstones - what a 'classic'. I guess that's what you would call "in-your-face" fakery. :P

However, there's something even MORE "in-your-facey" about these silly NASA productions: the commentary of the same.

At the 14:35 mark (of above-embedded video), the speaker/actornaut throws THIS lame line at our faces (commenting on the ubercrappy "Shuttle-night-landing-filmed-with-infrared-camera") :

"We defy Hollywood to match this sequence". :rolleyes:

Who writes this stuff? Well, "Hollywood" I presume. -_-


Oh that was hilarious. Don't they even bother to watch their own productions? No neither would I!
Giants in Space
looking through the viewfinder of a Camera indeed!
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Re: Does Rocketry Work in the Vacuum?

Postby molodyets on May 9th, 2017, 2:52 pm

Thanks for the vid. That was one of the most ridiculous things I've ever seen, especially the landing. From orbital speed to landing speed, and all they needed was just a little bit of heat dissipation. It's no wonder that they stopped the shuttle program. I think they were pushing their luck keeping it going for as long as they did.

When the satellite exited the bay, spinning, there was no sign of a counter spin of the shuttle, to maintain angular momentum of the system. They're always talking about little details, like the name of the equipment they're using and where it originated, but never about all the little things they have to do to maintain their orientation.
On a similar point, I've never heard them mention how they have to match the vehicle rotation to match their orbital period so they are always facing the Earth in the same orientation. For example, one side of the ISS is always facing the Earth which means the whole thing has to rotate every 90minutes.
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Re: Does Rocketry Work in the Vacuum?

Postby dblitz on May 9th, 2017, 5:16 pm

When something explodes, anything nearby is pushed away by the force of a blast wave. This is what I thought propelled rockets, the restriction of the blast wave into a narrow channel, pushing not against air, but against the rocket. I never thought a terrestrial rocket was pushing against air, it seemed like the blast of the continuously exploding fuel pushed the rocket upward because anything near an explosion is going to move away from it at speed. I'm not sure why there is a need for something to push against like air, The explosion pushes the rocket along.

I don't believe anything either way, but I lean towards no rocketry because of NASA fakery of Earth images. If they could do it, why wouldn't they? I'm just not sure the free expansion idea really debunks it.
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Re: Does Rocketry Work in the Vacuum?

Postby pov603 on May 10th, 2017, 10:19 am

kickstones » 09 May 2017, 10:28 wrote:
https://www.youtube.com/watch?v=ZJw5lE9089o


full link: http://www.youtube.com/watch?v=ZJw5lE9089o


Prior to the 3:28 mark (0:50, 1:36, 1:44 etc) they show the Astro-nots with helmets on going into space with their shirtsleeves rolled up and bare arms exposed! :blink:

That is standard practice for entering a vacuum and risking full rapid decompression?
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Re: Does Rocketry Work in the Vacuum?

Postby Peter on May 12th, 2017, 8:10 pm

dblitz » May 9th, 2017, 4:16 pm wrote:When something explodes, anything nearby is pushed away by the force of a blast wave. This is what I thought propelled rockets, the restriction of the blast wave into a narrow channel, pushing not against air, but against the rocket. I never thought a terrestrial rocket was pushing against air, it seemed like the blast of the continuously exploding fuel pushed the rocket upward because anything near an explosion is going to move away from it at speed. I'm not sure why there is a need for something to push against like air, The explosion pushes the rocket along.

I don't believe anything either way, but I lean towards no rocketry because of NASA fakery of Earth images. If they could do it, why wouldn't they? I'm just not sure the free expansion idea really debunks it.


I agree. I think this is all being over-complicated and all this “pushing against air”, “no air to push against in space” is missing the point. To re-phrase what you said a little: The combustion expands rapidly pushing against the top of the combustion chamber pushing the rocket along. There is no cancelling force from the expansion in the opposite direction because that end of the combustion chamber is open, ie the flames you see coming out the back of the rocket are all sound and fury signifying nothing. The combustion also expands to all sides of the combustion chamber - these forces cancel each other out, but if the chamber is cone shaped, as most are, then the molecules hitting the sides also create a component of forward thrust.

So in theory a rocket can work in space. Presumably the the fuel and oxidant would need to enter the combustion chamber with force and be ignited instantly before the “vacuum” disperses them.

A bigger problem before the rocket gets anywhere near space is the amount of rocket fuel needed. NASA’s large fireworks (Saturn V, Space Shuttle) can only carry enough fuel to go a couple of miles before they fall back into the Atlantic. You can see rockets level off and then head down in extended launch films. Officially they are entering orbit and following the curvature of the earth but in reality are only a couple of miles away. (The flat earthers have posted this kind of analysis, they are actually educating me lol, but not about the shape of the earth).

The 3 stage rocket idea (illogically complex and heavy at launch with redundant rocket motors) was invented so if a plane or ship got into the cordoned area a few miles out of Cape Canaveral and saw something fall into the ocean they would merely think that was the first stage rather than the whole thing. Or in the case of the Shuttle – one of the detachable solid rocket boosters.
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Re: Does Rocketry Work in the Vacuum?

Postby Flabbergasted on May 12th, 2017, 11:48 pm

Peter wrote:You can see rockets level off and then head down in extended launch films. Officially they are entering orbit and following the curvature of the earth but in reality are only a couple of miles away. (The flat earthers have posted this kind of analysis, they are actually educating me lol, but not about the shape of the earth).

The 3 stage rocket idea (illogically complex and heavy at launch with redundant rocket motors) was invented so if a plane or ship got into the cordoned area a few miles out of Cape Canaveral and saw something fall into the ocean they would merely think that was the first stage rather than the whole thing. Or in the case of the Shuttle – one of the detachable solid rocket boosters.

So, basically you are saying that:
i) NASA launches real rockets and real shuttles.
ii) NASA´s launch videos are legit.
iii) NASA´s rockets and shuttles never reach space.
iv) NASA´s rockets would work in space if only they could get there.
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Re: Does Rocketry Work in the Vacuum?

Postby Peter on May 14th, 2017, 9:11 pm

Flabbergasted » May 12th, 2017, 10:48 pm wrote:
Peter wrote:You can see rockets level off and then head down in extended launch films. Officially they are entering orbit and following the curvature of the earth but in reality are only a couple of miles away. (The flat earthers have posted this kind of analysis, they are actually educating me lol, but not about the shape of the earth).

The 3 stage rocket idea (illogically complex and heavy at launch with redundant rocket motors) was invented so if a plane or ship got into the cordoned area a few miles out of Cape Canaveral and saw something fall into the ocean they would merely think that was the first stage rather than the whole thing. Or in the case of the Shuttle – one of the detachable solid rocket boosters.

So, basically you are saying that:
i) NASA launches real rockets and real shuttles.
ii) NASA´s launch videos are legit.
iii) NASA´s rockets and shuttles never reach space.
iv) NASA´s rockets would work in space if only they could get there.


i) No. The close ups are Hollywood. The long shots seem to be the launch of some kind of large firework based on the (possibly wrong) assumption that Floridians would expect to see something in the distance . The idea of a complex rocket is just that, an idea.
ii) No.
iii) Nowhere near.
iv) Sure, if only they could find a way to refuel, navigate, orientate, slow down, change direction, protect from intense heat, protect from probably intense radiation, come back and land safely.
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