Does Rocketry Work in the Vacuum?

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Re: Does Rocketry Work in the Vacuum?

Postby ObamaSimLaden on September 30th, 2016, 8:17 pm

allancw » August 12th, 2016, 5:58 pm wrote:Simon and I had a back and forth a couple years ago that I'll briefly repeat -- I haven't gone back on this thread to see if something similar has been posted, so forgive the possible redundancy.

I asked Simon to imagine the two of us floating in space, me with a loaded 9mm pistol. Would it be ok if I pointed it at him and pulled the trigger. Simon said, sure, it wouldn't shoot in the vacuum (this may be a bit oversimplified).

If you go to Youtube you'll find a vid wherein a pistol shoots just fine underwater. Mmmmm. See, the bullet plus casing contains all needed to go off, so being underwater is not a problem.

Yes, a vacuum is a bit different, but those who feel that rocketry won't work in a vacuum... are you sure enough to say 'OK' to my pulling the trigger? (I think Simon changed his mind.)

The point here isn't the bullet coming out of the barrel -- which I am sure it would -- but rather the recoil. The recoil is the point. Imagine a hundred shots per second.... via the continuous recoil you have a rocket, no?

Again, sorry if this is redundant.


I'm new here and skimmed some of this thread. I also question whether rocketry would work in a vacuum. I used to take it for granted, but not so sure. Interesting question. A gun is different than a rocket, though I get your analogy. Imagine floating in space and you fire a gun. The bullet (gasses) will push back on the chamber, which in turn pushes back on the shooter. I can see the recoil pushing the shooter back, but the bullet would probably also fire...perhaps at a lesser speed than in gravity environment (simplified for no atmosphere), but maybe still enough to be fatal. The bullet/gasses are going to take the path of least resistance, but also you have an equal and opposite reaction. You can feel the recoil of a gun, and I have no doubt it would propel you backwards in space.

A rocket just floating in space firing a rocket engine I'm not so sure. There's nothing to push against. I know they say the rocket is pushed upward by the thrust, but I wonder if it would just fire and fizzle in space? If the gun were to be free floating in space and could spontaneously fire the gun and bullet would presumably shoot off in opposite directions and I'm sure a formula can prove that.

Now imagine you are flying towards the moon in outer space at 25,000 mi/hr and you need to stop quickly and your engine happens to be facing forward and you fire it at full thrust. Is that going to slow you down to a halt in a vacuum? I'm not convinced yet. There's still the question of igniting the rocket in space, but we can assume the fuel is self contained. Seeing the Movie gravity made my eyes roll constantly. Like the whole Fire extinguisher propellant. I don't think that would happen period...without even considering the other stupid assumptions.

All that said, I don't think we could have gotten a lander to the moon and back....and it would have been far to risky to try.

Another thought is imagining an airplane (or helicopter) in space. The propellers or jet engines would have no atmosphere to Push. They would just spin and spin and go nowhere, no matter the angle of attack of the blades/wings. Imagine swimming in space. Your arms spinning and legs kicking, but you go nowhere. This is always a pet peeve with sci fi movies like Star Wars, Armageddon, buck rogers, with x wings and tie fighters banking and turning like they are on earth in a vacuum. Not possible. I think maybe the same with rocket engines. They just fire and you float stationary.
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Re: Does Rocketry Work in the Vacuum?

Postby Vera Obscurata on November 12th, 2016, 12:38 am

I just had an amazingly interesting discussion with a 75-80 year old astrophysicist. The very humble and decent old man allowed me to outline my arguments why Space Travel is impossible. The points from this topic plus more of my own, not published anywhere before I threw at him in a mature manner and his responses have given me new input for a new thread I planned already to create.

My last question of the hour long talk we had was "do you believe that from 1969 to 1972 6 times people were sent to the Moon and after that never again?"

He responded me with a "yes", which of course formed the basis for a new flow of objections from my side.

The old man ended the discussion with the words "I don't have any scientific arguments against your points".

Wow, what an amazing hour this was. Will be continued in a new topic soon.
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Re: Does Rocketry Work in the Vacuum?

Postby aa5 on November 13th, 2016, 6:51 am

I'm looking forward to that thread you plan to create! That old scientist sounds like someone you want to keep as a friend. It is so hard to find people who are willing to have open scientific debate, where nothing is sacred, the logic just goes where it will.

At the end of a discussion a friend can still be leaning in the other direction for their belief, than you. That is ok, sometimes even beneficial as he will challenge your arguments!
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Re: Does Rocketry Work in the Vacuum?

Postby theyBOUGHTit! on December 26th, 2016, 4:56 pm

EXTREMELY SIMPLE:

Home science experiment.

Go to sea level with several "Estes" rockets on some sort of track, and a way to measure the time it takes for the rockets to go from point A to point B.

NOW-- take your set up to the highest elevation you can reach, and perform the experiments again.

WHICH ROCKETS will reach the end of the track the fastest? the ones at SEA LEVEL, or say perhaps you found a place higher than some 20,000 feet. Will the high elevation launches be faster than the sea level launches? Will the high elevation launches be SLOWER because there was less air to push from?

If the rockets are IN FACT slower at high elevation, THEN YOU HAVE PROOF that the thinner the air gets, the less thrust can result.

NO BRAINER!

How can it be this easy to confirm, and nobody seems to have tried this?

VERY simple.
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 27th, 2016, 12:32 am

theyBOUGHTit! » December 26th, 2016, 3:56 pm wrote:EXTREMELY SIMPLE:

Home science experiment.

Go to sea level with several "Estes" rockets on some sort of track, and a way to measure the time it takes for the rockets to go from point A to point B.

NOW-- take your set up to the highest elevation you can reach, and perform the experiments again.

WHICH ROCKETS will reach the end of the track the fastest? the ones at SEA LEVEL, or say perhaps you found a place higher than some 20,000 feet. Will the high elevation launches be faster than the sea level launches? Will the high elevation launches be SLOWER because there was less air to push from?

If the rockets are IN FACT slower at high elevation, THEN YOU HAVE PROOF that the thinner the air gets, the less thrust can result.

NO BRAINER!

How can it be this easy to confirm, and nobody seems to have tried this?

VERY simple.


Please don't use all-caps unless you are justified in doing so. Your posts are rather irritating to read when you are typing as though you are speaking. Please, try to compose your writings as if they will be read and not acted, if you could at all help this. I am sorry if that seems prejudiced of me.

I am not sure this would be an excellent proof because there may be a threshold that makes rocketry much less viable.

It would also be difficult and expensive to test. High elevations have different climates, air movements and all sorts of variables that a pure vacuum is theoretically said to not have. I don't know about you but I don't get up to extremely high elevations very often anyway.
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Re: Does Rocketry Work in the Vacuum?

Postby patrix on December 28th, 2016, 11:02 am

This guy does an experiment to prove rockets work in vacuum
https://youtu.be/uf6158lBjGo
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 28th, 2016, 5:37 pm

patrix » December 28th, 2016, 10:02 am wrote:This guy does an experiment to prove rockets work in vacuum
https://youtu.be/uf6158lBjGo



full link: http://www.youtube.com/watch?v=uf6158lBjGo

And fails to prove that rockets work in infinite vacuum. All this experiment shows is that a propulsion can destroy a vacuum scenario by activating. I would like to see an experiment showing that rocket propulsion works in an absolute vacuum that can take on a great more many changes.

There is no infinite vacuum in a tiny pressurized or depressurized chamber where propulsion is changing the conditions.

If you'd read this thread or actually shown that you've used your brain and not borrowed official stances in thinking about this subject, you might have already noticed this argument and its failure to address the problems.

Now regardless of all the vacuum discussion (and perhaps to save you from this and other equivocating you are doing on the forum) why would you be arguing for the lying scam agency? Your presence is growing tiresome and you're not adding anything to the discussion except a rather useless baseless belief in liars.
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 28th, 2016, 5:41 pm

The comment section of that video does contain the classic gems of either side, which basically go something like this:

Doubter: Why is NASA lying?

Believer: It's not just NASA lying. It's many organizations around the world backing up NASA's stories.

Doubter: Let's not change "lies" to "stories". You still haven't addressed the fact that NASA has lied about its space missions.

Believer: (plugs ears) la la la la la

Doubter: Okay, that's not really an argument.

Believer: My dada works for NASA* and he would never lie.


:rolleyes: Close curtain

* substitute for:
- I've had military training
- I've looked in a telescope
- I've watched a lot of television
- etc.
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 28th, 2016, 6:08 pm

This comment in that video seems to make a bit more sense than the palaver offered by patrix so far:

dxguy wrote:So, yes, the nozzle opens at the bottom. Completely. There may be steering vanes or shutters (like the German V1 pulse rocket) or platinum catalytic grids, etc, but, yes it's open to space. If you look at videos of rockets being fired


... if you start from NASA's videos, you're already in for brain hurt from having to justify and explain how special effects are real photography. Luckily, that's already happened to this (possibly brain damaged?) fellow.

the combustion plume comes from inside the nozzle and goes out beyond the nozzle opening by some considerable distance


:rolleyes:

perhaps 5 to 50 X the length of the entire motor. What are we looking at?


Indeed. What are we looking at? Here's this salesman's take:

a bunch of burning rocket fuel rapidly exiting through the nozzle opening.


... and combusting in open space as well as it has in atmosphere, while remaining just as effective and orderly and shaped as if it were operating in atmosphere! :o

It is a very highly dense, pressurized plume of burning gas stuck right on the end of the nozzle, and in fact the external burn is part of the motor system.


Right, that's what the graphics depict, but would it happen in real life and would it remain effective? Faked evidence does not make it so.

Just looking at the rocket you're holding in your hand you'd think that all of the fuel would just dump out with no effect.


Uh, really? :blink:
That's what we would think? He doesn't seem to understand the arguments of his intellectual opponents.

In reality, every new inch of thrust generated exits the nozzle and quickly expands giving a massive cloud of combustion material to push against.


Yes, it quickly expands to ... a nice shapely cone, because hand waving NASA reason. :rolleyes:

I wonder why he's chosen inches. Just a turn of speech, I suppose. Like "screaming" fuel he mentions later ...

This accounts for much of the efficiency of the rocket, but most of the thrust is from the rapid burning of the fuel sending it's mass quickly to the exterior. We do have conservation of momentum where M1*v1 (plume mass) = M2*v2 (spacecraft mass). I'm not ignoring you, am writing an appropriate response to your question, if I thought you were in a hurry I would have just sent you an insult.... Feel free to write back with any other questions. I carefully picked these white papers I sent you as they describe operation in layman's terms but also includes the calculus based derivation so you can easily compare one paper with the next. I have to admit, I found no papers or discussion on the open web or the tech subscriptions about the derivation and formulae you are using. Perhaps I need to refine my search? So, you make some accusation that I don't understand how the earth's ambient air causes something or other or not?. Go back to the equation:

F = q * Ve +( Pe - Pa ) * Ae

Where F=Force generated by the total motor thrust q = mass flow in motor Ve = Ejection speed Pe = Ejection pressure Pa = Ambient air pressure (0 for space, 15 psi sea level) Ae = Exit area Pe is very large compared with ambient air Pa. Ae is very large compared with ambient air Pa So, Look at the term (Pe-Pa) and note that there is very little change in thrust from sea level to space. Look at the term (Pe - Pa) * Ae, there is very little effect of having the earth's atmosphere present or not! In fact, the motor will operate a very little bit better in space, ceteris paribus [other things equal].


Funny moment.

The video comments above this lengthy and ineffective argument refer to this old link as an "answer":

We know, the rockets in space use Newton's 3rd law to increase their velocity and hence move. What I don't understand is how it is possible in space aka vacuum-state without air? From what I know, Joule's "Free Expansion of Gas" says that free-expansion compresses the gas and is therefore "affected" by vacuum so it can't make the rocket move as the gas will have zero press/force. Could someone please explain me how rockets do really work and the above-mentioned statement?

Actually, please have a look at this site: viewtopic.php?f=23&t=1632

Not: The site appears to include some conspiracy theory thingummies, but made me wonder anyway.

-http://physics.stackexchange.com/questions/91789/rocket-thrust-gas-free-expansion-of-gas

This thread! B)

---

This entire discussion is old news, patrix. It's failed. As you browse earlier posts in this thread, you'll see we are still rather cutting edge for posting these questions, and NASA still hasn't come up with a better response than defending and arguing from their fake videos. Now, why would that be I wonder?

Could it be because their best "argument" is ... fake evidence?
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Re: Does Rocketry Work in the Vacuum?

Postby patrix on December 28th, 2016, 7:35 pm

All this experiment shows is that a propulsion can destroy a vacuum scenario by activating. I would like to see an experiment showing that rocket propulsion works in an absolute vacuum that can take on a great more many changes.


I agree. And I also agree that NASA and the other space agencies are lying through their teeth about everything, but as I said, I'm interested in finding out the extent of the lie.

And I know science, especially medicine and physics, have been poisoned ad absurdum throughout the 20th century. But I still believe the scientific method works:
I observe something and set up an hypothesis and to try to disprove it by controlled experiments. If I perform a sufficient number of experiments that all fails to refute my hypothesis, the hypothesis holds. If it is not possible to design experiments to refute the hypothesis, I'm out of luck. Then you have to use other tools to figure things out.

For example: Since NASA is lying on just about everything, I set up the hypothesis that rockets don't work in vacuum. I perform an experiment that others can repeat and discover that rockets seem to work in vacuum. If others can repeat the experiment to confirm my findings, then the hypothesis should be considered refuted.

Of course the design of the experiments is of importance. This only shows that a rockets work in a confined vacuum. But since the title of the thread was "Does Rocketry Work in the Vacuum?" I figured this experiment would be interesting. I don't know anything about how the video was made and I have not verified this experiment myself.

Edit: A comment to the other things you write hoi: Yes of course this experiment is made by a true believer in all the space fakery, but I still think it is an interesting experiment. Lets not do the discredit by association thing.
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 28th, 2016, 7:51 pm

Of course. Well, when we and legitimate scientists can rent one of those giant vacuum spaces we've mentioned earlier in the thread, we can actually conduct things that barely approach experiments close to what NASA proposes happens in space. Even that would not be right because we would need to get above and stay above the Karman line.

Unfortunately, following developments in real science is tricky because we must train people to also be skeptical of so-called "peer reviewed" massively accepted lies. Do you really believe you are helping people do that with your present contributions to this thread?

In any case, I would appreciate your eye on subjects where you can actually help.
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Re: Does Rocketry Work in the Vacuum?

Postby Flabbergasted on December 28th, 2016, 8:04 pm

You are completely missing (or avoiding) the point, patrix. In order to be propelled, rockets must transfer energy to an external medium which offers some degree of resistance. Experiments in vacuum chambers, even huge ones, provide such a medium (the walls of the chamber). The void of space does not. This has been expounded over and over in this thread, if you´d care to read it.
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Re: Does Rocketry Work in the Vacuum?

Postby patrix on December 28th, 2016, 9:13 pm

Flabbergasted » December 28th, 2016, 8:04 pm wrote:You are completely missing (or avoiding) the point, patrix. In order to be propelled, rockets must transfer energy to an external medium which offers some degree of resistance. Experiments in vacuum chambers, even huge ones, provide such a medium (the walls of the chamber). The void of space does not. This has been expounded over and over in this thread, if you´d care to read it.


Well if the hypothesis that rockets do not work in vacuum can only be refuted by an experiment performed in an infinite vacuum then I guess we're out of luck. Maybe you could put sensors on the walls of a big vaccum chamber to see if anything happens there when the rocket moves?
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Re: Does Rocketry Work in the Vacuum?

Postby hoi.polloi on December 28th, 2016, 10:18 pm

Yes, refer to the title of the thread.

"Does Rocketry Work in the Vacuum?" Rather than a vacuum.
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Re: Does Rocketry Work in the Vacuum?

Postby Flabbergasted on December 28th, 2016, 10:30 pm

patrix wrote:Maybe you could put sensors on the walls of a big vaccum chamber to see if anything happens there when the rocket moves?

It´s not that "something happens to the wall when the rocket moves". A rocket will move in a vacuum chamber (or any chamber, for that matter) because the exhaust bridges the space between the nozzle and the end wall of the chamber, pushing against it. No experiment is necessary to understand that.
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