Does Rocketry Work beyond Earth's atmosphere?

If NASA faked the moon landings, does the agency have any credibility at all? Was the Space Shuttle program also a hoax? Is the International Space Station another one? Do not dismiss these hypotheses offhand. Check out our wider NASA research and make up your own mind about it all.
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simonshack
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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Sun Jun 29, 2014 5:54 pm

RaoulMarz wrote:Coming back to the rocket - the propulsion is due to the pressure differential in this glob in which the rocket resides. So that it implies the high density gas would be in the area surrounding the rocket nozzle, and the lower density gas more or less above rocket nozzle in the direction of the nose cone.
Hi Raoul - and welcome to the forum. I will take your questions as an exercise towards perfecting / clarifying my argumentation against the possibility of rockets being propelled in the vacuum of space.

I think that what you're saying is similar to what this self-professed 'rocket scientist' is saying :
KAREN (self-professed rocket scientist of the Straightdope website) - says:

"The truth is that the rocket does have something to push against: namely, its own fuel."
http://www.straightdope.com/columns/rea ... m-of-space
The thing is, what Karen refers to is the recoil effect / or recoil force that occurs in nature when, for instance, you fire a gun: the bullet ( object A ) will exit at high speed from the gun's nozzle - and might even pierce an armor plate - while you ( object B ) will just feel a slight backward jolt in your wrist. The force of that jolt is given by the amount of air displaced by the gunpowder's explosion inside the gun's muzzle - while its energy is obviously proportionate to the bullet's weight / size / mass - AND SO ARE THE RELATIVE SPEEDS of the objects ( A & B ) involved: the bullet (object A ) will travel at maybe 1000km/h - while your wrist ( object B ) will be nudged backwards at, well... perhaps 10 km/h at the most?

Just for once - I'm going to trust Wickedpedia on this matter...
Misconceptions about recoil
Although energy must be conserved, this does not mean that the kinetic energy of the bullet must be equal to the recoil energy of the gun: in fact, it is many times greater. For example, a bullet fired from an M16 rifle has approximately 1763 Joules of kinetic energy as it leaves the muzzle, but the recoil energy of the gun is less than 7 Joules.
http://en.wikipedia.org/wiki/Recoil
Similarly, if you sit in a wheelchair holding a basketball - and throw it with all your strength in front of you (at a speed of, say, 40km/h), this will not propel your wheelchair backwards at 40km/h. Yes, It will make you and your wheelchair slowly roll a bit backwards - but not much.

This is to say that I do not deny the existence of the recoil effect / or recoil force. However, I do not think that - as NASA claims - this effect is sufficient to propel, say, a 100.000kg rocket (still bound by Earth's gravity) at hypersonic speeds - just by ejecting a certain amount of fuel-per-second out of its nozzle. You may argue: "but NASA says the fuel is ejected at the hypersonic speed of 4,4 km/s!". Well, here we have another big problem with NASA's claims - because they also tell us that their rockets need to attain almost twice that speed (the famous "8km/s escape velocity") in order to exit our planet's atmosphere & gravitational pull. So, even if a given, constant mass of fuel is being ejected at 4,4km/s - it couldn't possibly propel the 100.000kg rocket mass at 8km/s !

Here is a diagram to illustrate my points, once again. Hopefully, it isn't too cluttered / unreadable (sorry for the vertical text!) :

Image
(In the right-hand diagram, the puff seen below "A" symbolizes the free expansion of the rocket exhausts in the vacuum of space.
Any gases expelled in vacuum - as of the laws of thermodynamics - will not do any work whatsoever. Even Newton would agree!).


I dearly hope Karen-the-rocket-scientist (of the Straightdope website) will come by and defend her theories - and their website's slogan : "Fighting ignorance since 1973". <_< http://www.straightdope.com/columns/rea ... m-of-space

We (the human species - or any of our gravity-bound objects) have no means to propel our weights beyond the boundaries of the fluids of air, much as dolphins have no means to propel their weights beyond the boundaries of the fluids of water. Squibs (calamari) propel themselves very fast indeed by ejecting water out of their bodies (much like rockets eject hot air from their nozzles), and sometimes, squibs will even jump out of the sea and crash-land upon ship decks. But so far, we don't know of any high-flying, cosmic space-squibs.

RaoulMarz
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Re: Does Rocketry Work in the Vacuum?

Unread post by RaoulMarz » Sun Jun 29, 2014 9:46 pm

I am derailing myself it seems. Everytime I trust the form editor to make a lengthy post I get logged out when I click "submit" and lose my entire post. Is there a timeout setting somewhere?

I realise I may have repeated a lot of what others have already said. Just to be clear: I don't believe your typical off the shelf rocket works in a vacuum as suggested by NASA. I certainly DO NOT say what this KAREN person is saying. What I was conjecturing about was a theoretical rocket that doesn't exist except in my mind, that is able to create a containment field in the vacuum, that could conceivably function in the vacuum. I am sorry that I was not clear on that, as I believe just as you and the others that the NASA rocket, is an "atmosphere" rocket. My understanding is that it works because of air pressure that "pushes" it upwards, and wouldn't work in a vacuum because there would be no such pressure in a vacuum, because of free expansion. I can't see that what I am writing here is in agreement with NASA's theories on rocketry. To me an area of interest is to refine all the forces at play as a rockets ascends through the atmosphere.

I certainly could have a detail wrong or could not be clear enough in my explanations but I truly do not believe in NASA's or KAREN's theory. To me, a NASA rocket in the vacuum, is like a car that is in neutral and with the parking brakes on and being revved to 5000 rpm but goes nowhere.

HonestlyNow
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Help in constructing your post

Unread post by HonestlyNow » Sun Jun 29, 2014 10:23 pm

RaoulMarz wrote: Everytime I trust the form editor to make a lengthy post I get logged out when I click "submit" and lose my entire post.
One way to get around worrying about timing out is to construct your post in Notepad (text editor). (Then copy/paste into Reply box. Make sure to use Preview to help in cleaning up any errors.) This way you can take as much time as you need. Learn the basic HTML tags, too.

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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Sun Jun 29, 2014 11:23 pm

RaoulMarz wrote:I am derailing myself it seems. Everytime I trust the form editor to make a lengthy post I get logged out when I click "submit" and lose my entire post. Is there a timeout setting somewhere?
Raoul, this may be because of my recent settings limiting to 3 hours the editing of posts. I have now extended it to 10 times as much. Sorry about that.

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Re: Does Rocketry Work in the Vacuum?

Unread post by hoi.polloi » Sun Jun 29, 2014 11:26 pm

Okay, thanks for your clarification Raoul. That is helpful.

As for the problem of messages disappearing: yes, we highly suggest you compose your messages in a separate text area which does not add extra carriage returns. A good program to use is WordPad which comes with Windows. Then you paste this into the content window, and carefully re-read it and edit it to fit the forum. I.e.; use tags, proper carriage returns, a good clean edited appearance and so on. We have suggested NotePad before, but this is stupid because people forget to remove the extra random and obnoxious line breaks and it makes their post indistinguishable from a post we would suspect of being made by a robot.

Also, browsers like Opera and Firefox tend to automatically cache your content such that hitting the 'go back' button in your browser (upon encountering an error) should restore what you were typing.

Finally, you can "select all" and "copy" the content once in a while. This will preserve your last edited content unless your computer freezes or crashes before you post. But the best option is using a separate composing document such as WordPad or a quick "notes" expansion/widget.

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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Mon Jun 30, 2014 12:20 am

RaoulMarz wrote: To me an area of interest is to refine all the forces at play as a rockets ascends through the atmosphere.
Alright - we're back on topic now, Raoul!

This is really an area of interest to me: the forces at play as rockets ascend through the atmosphere.

I like to discuss that. :)

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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Thu Jan 22, 2015 5:38 pm

*

NASA "PHYSICS": THICK AS A BRICK


My pen pal "P from the UK" just wrote me this brief / well-formulated point - which inspired me to make this post /and below graphic. I think we all know how NASA often uses 'clever, easy-to-understand-basic-physics" analogies when trying to explain the physics of how their rockets are propelled (up through the atmosphere - and beyond). I will hereby illustrate - using their own "children's-book" approach - how NASA's claims concerning rocket propulsion are wrong and, worse still, deliberately deceptive.
P from the UK wrote: As you are probably aware, NASA often use the analogy of a man sitting in a boat throwing bricks out the back to demonstrate how their rockets work; according to them the brick represents the rocket exhaust.

This is false.

In fact it is the man's hand that represents the rocket exhaust, whilst the brick represents the atmosphere.

You see what they did there?

The same principle can be applied to their 'Newton's Chariot' model as well.

I don't recall if this was pointed out in your 'rocketry in vacuum' thread; if so apologies, if not I hope it is useful in simplifying & clarifying the subject.
MAN IN DRIFTING BOAT
A man in a boat on a river is drifting downstream. He has three piles of bricks on board: B (pile of Big bricks), M /pile of Medium bricks) and S (pile of small bricks). He wishes to move upstream, so in order to combat the force of the constant waterflow (which we may think of as the constant Force of Gravity), he starts throwing his bricks overboard - in 'downstream' direction :
BoatPropulsion_trio.jpg
Fig.1: At first, his boat is drifting sideways, so he needs to overcome the strong DRAG pushing his boat downstream (think of it as the combined forces of gravity and atmospheric / aerodynamic drag which a rocket must overcome at sea level - in order to take off from the launch pad). He therefore starts throwing the BIG bricks overboard, as fast as he can. He is happy to see that the boat is being propelled upstream (much like a rocket will, in fact, lift off from the ground).

Fig.2: Luckily, the boat somehow straightens itself up (thus reducing the hydrodynamic drag - much like a rocket reaching thinner air / atmospheric pressure at higher altitudes) and, although he has run out of BIG bricks, he is now happy to see that he can keep moving upstream by throwing his MEDIUM-sized bricks off the aft of his boat / downstream.

Fig.3: But as he runs out of MEDIUM-sized bricks, the man is now distressed to see that, as he throws overboard his remaining pile of SMALL bricks (representing the very thin / ever-dwindling atmospheric pressure of a rocket approaching 100km altitude or so), the boat has stopped ascending and is now drifting downstream again - being now overwhelmed by the force of the waterflow (think "Force of Gravity").

And no - contrary to widespread popular myth - gravity does NOT abruptly cease to exist at 100km of altitude.
"At 100 km, you would officially be in space, yet the weight force of gravity would still be nearly the same."
http://sciencelearn.org.nz/Contexts/Sat ... ite-motion

In conclusion: NO known man-made propulsion system can make a rocket ascend beyond a certain altitude (100km or so) where the quickly dwindling atmosphere pressure drops to near-zero levels, or near-vacuum.
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lux
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Re: Does Rocketry Work in the Vacuum?

Unread post by lux » Thu Jan 22, 2015 8:32 pm

How do the bricks represent the atmosphere?

HonestlyNow
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Re: Does Rocketry Work in the Vacuum?

Unread post by HonestlyNow » Thu Jan 22, 2015 8:37 pm

lux wrote:How do the bricks represent the atmosphere?
As I envision it, the bricks are something to push against. And they get lighter (less atmosphere) as you move further away from the starting point.

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Re: Does Rocketry Work in the Vacuum?

Unread post by lux » Thu Jan 22, 2015 10:08 pm

But, it says he throws the bricks overboard. And it also says the bricks represent the atmosphere. So, if the bricks represent the atmoshere then he's throwing the atmosphere overboard?

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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Thu Jan 22, 2015 10:18 pm

HonestlyNow wrote:
lux wrote:How do the bricks represent the atmosphere?
As I envision it, the bricks are something to push against. And they get lighter (less atmosphere) as you move further away from the starting point.
Precisely my thoughts, dear HonestlyNow.

The action><reaction force of a given brick launched by a man in a boat is proportional to the mass of the brick - much like the air mass (i.e. the DENSITY of the atmospheric pressure against which a rocket exhaust pushes) determines the action><reaction force which propels the rocket upwards - and away from the force of gravity (constantly reclaiming the rocket's weight).

So, in answer to Lux's question: the B/M/S bricks (Big/Medium/Small) in my above graphic represent the dwindling atmospheric pressure - and its undisputed, decreasing density with increasing altitudes.

As the boat man runs out of bricks altogether (think: "a rocket reaching the vacuum of space"), there are no more forces available to him to make the boat (or the rocket) ascend.

The man in the boat may try and throw imaginary / non-existent bricks downstream - but his muscular actions will just generate a minuscule recoil effect/force on the boat - far too weak to keep his boat from drifting downstream. What NASA keep claiming is that IT IS THIS minuscule recoil effect that keep their big rockets flying upwards - and into the outer space.

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Re: Does Rocketry Work in the Vacuum?

Unread post by lux » Thu Jan 22, 2015 10:31 pm

Do rockets fly slower at higher altitudes than lower?

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Re: Does Rocketry Work in the Vacuum?

Unread post by simonshack » Thu Jan 22, 2015 11:03 pm

lux wrote:Do rockets fly slower at higher altitudes than lower?
Dear Lux,

As I have previously pointed out in THIS OLD POST of mine (June 2013), NASA says that their rockets' OPTIMAL "100%" performance (for speed & efficiency) occurs at a certain (unspecified) altitude when - in their own words - "the atmospheric pressure equals the pressure at the nozzle." NASA therefore implicitly admits that the action><reaction forces needed to propel their rockets up in the sky are directly related to / dependent on the surrounding atmospheric pressure /density:

Image
Source of original rocket nozzle over/under expansion diagram: http://en.wikipedia.org/wiki/Rocket_engine

It stands to reason that a rocket ascending through our atmosphere will reach its highest speed at some given, ideal moment of its ascent - when the ratio between the opposed forces of its exhaust-thrust (regulated by air density) versus aerodynamic drag (regulated by air density) reach an optimal balance. The problem is: what happens when the exhaust-thrust runs out of molecules and mass (think: "Brick-molecules and mass") against which to exert its very thrust?

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Re: Does Rocketry Work in the Vacuum?

Unread post by SteinUntStein » Thu Jan 22, 2015 11:29 pm

Interesting thread.

I want to side with Boethius (for nickname alone :)) here, and maybe bring up some other aspects of this issue.

First thought is it makes me think the old ether debate is relevant. The ether being discarded (by Einstein's crowd, Michelson-Morley, etc.), perhaps when it should not have been, adds to the difficulty.

For Newton, as I recall, a vacuum is a space totally devoid of matter. It is arguable that no such state can exist anywhere, certainly not on Earth, and such a vacuum has never to my knowledge been constructed.

The ether was itself a "type" of matter that contained all other matter, of the sort of background fabric which would make vacuum thrust a very real possibility.

https://www.lhup.edu/~dsimanek/philosop/ether.htm

Space could be no vacuum at all, but perhaps containing of a different type of matter.

Here from Department of physics, U. of Illinois (https://van.physics.illinois.edu/qa/listing.php?id=1046):
"We don’t know of any examples of a perfect vacuum, but know some bits of space that get pretty close. Space beyond the Earth’s atmosphere isn’t a bad approximation to a vacuum, but it is filled with solar wind particles, light from the sun, cosmic rays and cosmic microwave background radiation. It’s probably also filled with dark matter which doesn’t interact with other stuff (except gravitationally, and possibly only through the feeble weak interaction), as well as neutrinos. If you manage to pump all the air out of a steel can, for example, you will have a vacuum in there, but there will be photons constantly radiated off of the walls and re-absorbed by them. This soup of photons will be in thermal equilibrium with the walls, and therefore will have a defined "temperature". In fact, even the deepest of deep space (outside the galaxy, for example), is in a radiation bath of temperature 3K, left over from the Big Bang. There may be other stuff, like the neutrinos, for example, which are not in thermal equilibrium with the 3K radiation because they don’t interact with it, and so space may have two or more 'temperatures'."
So, I guess where I stand now is, if they did go to outer space, it's probably not a vacuum, and the whole idea of a true vacuum could be just another fairy tale. NASA justifies their propulsion strongest when they say that the thrust actually is designed to push against the rocket rather than the exhaust. Not sure I buy it, or how the thing works (I did see some diagrams...), but this, at least theoretically, eliminates any "need" to have air or anything else to thrust against. Because as it stands it seems to me as soon as that rocket hit space the exhaust would die out,, and I have my doubts about the sustainability of any fire-based, or even electrical ignition functioning under vacuum-like conditions.

http://www.chem.elte.hu/foundations/alt ... CERN01.pdf

For the record I do not believe in anti-matter, dark matter, or even black holes, and I think that if a rocket really broke completely away from Earth atmosphere (I think there could be a layer of "sub-space" between the two, perhaps where satellites or space stations go?) it would probably crumble onto itself like a tin can under the transitional pressure. The difference between maintaining the pressure in a pressurized airliner, and at the extents of the atmosphere, is tremendous.

http://www.engineeringtoolbox.com/air-a ... d_462.html

From Google (search-"how high is atmosphere"):
"The Earth's atmosphere is about 300 miles (480 km) thick, but most of the atmosphere (about 80%) is within 10 miles (16 km) of the surface of the Earth. There is no exact place where the atmosphere ends; it just gets thinner and thinner, until it merges with outer space." (!)

According to that chart cited above, sea level pressure is @1.03 kg/sq.cm or 14.7 psi. 50,000 feet measures 0.113 kg/sq.cm or 1.16 psi. 300 miles is 1,584,000 feet, this means the pressure at that altitude should be something like 30 times less what it is at 50,000 feet. Still in atmosphere, and frankly, I find the 300 mile line a little too tidy.

I apologize in advance if I rehashed something I must have missed, and yes I have been considered sane usually. Also happy to make your acquaintance. :D

PS:
On a side note, If we've been to space, then manifestly the propulsion works.
But if we have not been to space, how would we know what happens in space (re: Heiwa HELLO!), or even what it is like in any way?

lux
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Re: Does Rocketry Work in the Vacuum?

Unread post by lux » Fri Jan 23, 2015 12:12 am

Simon, what part of the rocket pushes against the air behind it?

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