Does Rocketry Work beyond Earth's atmosphere?

[Boethius]

I have some confidence in your ability to phrase things, but please correct your posts' numerous grammar/spelling problems. e.g.;

problems comes

inter[e]st

So what you are saying is that a ship with not enough momentum will have no way of correcting said momentum once it reaches the vacuum, and it will be helplessly drawn back into Earth's gravity no matter how much fuel is expended.

Conversely, if the ship has too much momentum, it could go flying off into deep space with no means of correcting itself and finding its way back home. The ship would be lost until it was captured by the gravity of a body in space like a planet or moon.

In short, an introduction to the vacuum would mean complete loss of control of the ship until it were once again free from the vacuum and in some kind of atmosphere, unless that ship achieved an 'orbit' which required no course corrections for the foreseeable future?

Hello, hoi.

Thanks for your examples. I have been focused, up to this point, on rockets in deep space, outside of any significant gravitational field. If a rocket is in a vacuum yet still under the influence of gravity, the situation is different.

Near-Earth
A ship that reaches the vacuum but without the momentum to continue past earth's gravitational field will be pulled back.
While it is being pulled back it is accelerated by gravity. In this case although the rocket produces no thrust the loss of mass actually creates force (because the rocket is accelerating) and we can (finally) apply Newton's 3rd law in space.

Obviously a rocket plummeting towards each will not be able to generate enough force due to lost mass to stop falling but what happens if the rocket sheds mass while gravity's pull is still weak (near the apex of its flight)? Could a rocket effectively bob like a cork shedding just enough fuel to keep gravity at bay? I need to do some research/calculations before I can say anything more on the subject.

NB: I was going to look into this under my investigation of "thrust in a vacuum" experiments performed by Goddard et. al. that seem to ignore the fact that these tests are done in earth's gravitational field and not in a simulation of deep space.

Deep Space
A ship that escapes into deep space, free of the earth's gravity, will not accelerate (change velocity) or change direction via rockets. Without a gravitational field accelerating the rocket its changing mass mass (due to lost fuel) will generate no force. Changing its mass would only change it's momentum.

P.S. I will try to keep a keener eye on my spelling and grammar.

[hoi.polloi]

Changing its mass would only change [its] momentum.

Edit: sorry, I misunderstood your point at first.

You are saying that a change in its momentum would not actually result in any change in vector or rate of orientation. You're just saying that recalculating the momentum (after expending fuel) would result in different numbers (because of its changed mass) but it would not allow the ship to manipulate itself through empty space.

In other words, I am hearing you say that Near Earth Orbit is highly dangerous but much more likely than the prospects of launching something that could successfully make it to the Moon, manipulate itself above the Moon's surface, then reorient itself and return home.

Briefly: The recent missions are more plausible but still highly unlikely. Apollo is bunk.

?

[simonshack]

You also haven't explained thrust (as from rocket motors) and how it relates to all this.

Neither has NASA, dear Lux... for almost half a century now!

I agree but I still see holes in Boethius' argument.

Dear Lux,

There may well be holes in Boethius' argument - but do not NASA's claimed feats and achievements over the decades have more holes than a Swiss cheese - including some very dense and dark ones? With this in mind, one must logically ask oneself: WHY is this so? WHY does NASA appear to lie about pretty much everything? Why produce fake imagery of the ISS if it is physically possible to place a spacecraft in low orbit - 'in free fall', as they call it - and circle the Earth endlessly for free, with virtually no fuel needed once it's up there? (This, in spite of the fact that - we are told - 90% of Earth's gravity pull is still exerted upon the spacecraft?).

My core question being: If rockets really can reach 'outer space' (more about that term in my next post) and be thrusted / steered around and even rejoin/dock with other spacecraft with utter precision, or satellites be placed in any desired orbit and altitude - why would then NASA not be doing so? In short: wouldn't there have to be, in all logic, a fundamental and insurmountable problem with space travel (hidden from the public) behind this evident / continuous NASA skullduggery - and for it to exist in the first place?

[simonshack]

*


PROPULSION REALITY CHECK


Perhaps the most common question inquiring minds have about space travel is: "how can rockets function in the vacuum of space - or in very thin air pressure"? To this question, NASA (and its believers) unfailingly respond roughly like this: "that's because rocket thrust is not achieved by pushing against air. Air has little or no influence on rocket propulsion. What makes a rocket move is the rocket fuel pushing onto itself. Have you ever heard of Newton's 2nd & 3d laws of motion?" Well, the claim that "air density has NO influence on rocket propulsion" has to be the silliest of all NASA lies. This is akin of saying that sea water has no influence on the motion of ships propelled with waterjet engines (see p. 4 below). NASA fans will then bring up the age-old example of someone standing on a wheeled office chair, throwing a medicine ball. Their tedious, triumphant punch line will always be: "See? As you throw the ball - the chair will move in the opposite direction"

1: CAR PROPULSION
The question is: just how much force / thrust can be produced in this way? Could a car be propelled by these NEWTON laws alone - with sufficient efficiency? Why then don't we apply these amazing forces here on Earth? Anyways, here's my proposal for a "NEWTON car". Just imagine, ladies and gents: if this works out - we could soon eliminate our dependence on air-and-fuel-propelled vehicles:


Yes! NASA teaches Newton-car experiments to kids! http://www.nasa.gov/pdf/153412main_Rock ... on_Car.pdf

Will I be able to sell this invention to General Motors? Volkswagen perhaps? I doubt it - but wish me luck! Yet, the principle of the above F1 force is what NASA claims to propel their magic rockets in a (near)vacuum. It also works, apparently, for precisely steering / docking their space vessels launched at tremendous orbital speeds - and to brake / decelerate them for re-entry so that they don't burn up in a fireball - like meteors do.

2:JET ENGINE PROPULSION
Now, we the people may never have launched a rocket into outer space - but this doesn't mean we rocket-less earthlings have no empirical / comparative knowledge with which to gauge the plausibility of NASA's claims. For one thing, we know that jet airplanes need air to be able to fly. They just won't fly in the absence of air. At a certain altitude, a jet plane will be starved of air - and both its engine and wings will cease to function. The plane will eventually stall catastrophically - and plummet back to Earth. There's no way, for instance, for a modern-day F-18 fighter to just point upwards and reach the Kàrmàn line - considered to be (at 100km of altitude) the threshold between our atmosphere and outer space.

THE KARMAN LINE
When studying aeronautics and astronautics in the 1950s, Kármán calculated that above an altitude of roughly 100 km (62 mi), a vehicle would have to fly faster than orbital velocity in order to derive sufficient aerodynamic lift from the atmosphere to support itself. At this altitude, the air density is about 1/2200000 the density on the surface.

For an airplane that is trying to fly higher and higher, the thinning air gives less and less lift, requiring a higher speed to create enough lift to hold the airplane up. There comes an altitude where it needs to fly so fast to generate lift that it reaches orbital velocity. The concept of the Kármán line is the altitude where the flying speed necessary to aerodynamically support the full weight of the airplane would be equal to orbital velocity (assuming the wing loading of a typical airplane).
http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line

Only NASA knows how they managed to send their "X-15" beyond the Kàrmàn Line (at 107km)- back in the sixties! http://www.astronautix.com/craft/x15a.htm


3: BALLOON PROPULSION http://hypertextbook.com/facts/1997/CassandraEng.shtml
There is also a limit beyond which balloons won't go. They will reach a (theoretical) maximum of 43km of altitude - and no further. That's quite simply a physically-dictated limit: no gases we know of are light enough to ascend beyond that altitude with a balloon. At that point, the air (atmosphere) is too thin and the balloon will be very much like a piece of wood floating on the surface of the ocean. Indeed, this brings us nicely to our next - and most interesting - form of propulsion: let us now imagine our Earth's atmosphere (and the air that we breathe) as a big, water-filled ocean - and let's conceptually replace oxygen with the thicker liquid known as 'water':


4: WATER-JET PROPULSION http://en.wikipedia.org/wiki/Pump-jet



In the thicker liquid known as water, the most modern method of propulsion is called "water jet, pump-jet or hydrojet". What do such jets do in order to propel these ships? Well, they pump out at great speed a jet of water into ... water! Surely, this propulsion can only take place if those waterjets are immersed in water. Now, imagine the above-pictured, docked / serviced ferry (filled with imaginary water tanks) suddenly switching on those powerful hydrojet engines at full throttle. Do you think the ferry would move forwards - or would the water (with only air to push against) just flush out from those two nozzles? Well, the ship would probably rock about a little - and perhaps even fall off its flimsy support pillars. But it surely wouldn't start travelling forwards at its seafaring cruising speed.

ROCKET PROPULSION
But those NASA ships (such as the 100.000+kg Space Shuttle) we are told, are a wholly different thing: neither air/atmospheric pressure nor gravity is of any concern to them - for producing either lift or combustion... As they soar towards the Kàrmàn line, where air/atmosphere is 2,2million times thinner than at sea level, the NASA rockets will keep providing the necessary, EVER INCREASING rocket thrust which any airborne object has to maintain in order not to stall and plunge back to Earth. In fact, NASA claims that the Space Shuttles achieved the required escape velocity of 27.000km/h. This, in spite of jettisoning their two main rockets (the SRB's) at only 45km of altitude, leaving the Shuttle (with its weeny three rear rockets) and its huge main tank to pull away from 90% Earth gravity, in near-vacuum air density towards the Kàrmàn line, for another 55km-long ascent ...

http://en.wikipedia.org/wiki/Space_Shut ... et_Booster

I am ready to hear evidence to the contrary, but as far as I can gather at this time of my life, mankind still hasn't overcome the - perhaps insurmountable - problems of propelling any earthly object into this magical "outer space" - where all things apparently freely orbit / float around - in circular or elliptical fashion - and with little or no fuel needed.

[Boethius]

Changing its mass would only change [its] momentum.

Edit: sorry, I misunderstood your point at first.

You are saying that a change in its momentum would not actually result in any change in vector or rate of orientation. You're just saying that recalculating the momentum (after expending fuel) would result in different numbers (because of its changed mass) but it would not allow the ship to manipulate itself through empty space.

In other words, I am hearing you say that Near Earth Orbit is highly dangerous but much more likely than the prospects of launching something that could successfully make it to the Moon, manipulate itself above the Moon's surface, then reorient itself and return home.

Briefly: The recent missions are more plausible but still highly unlikely. Apollo is bunk.

?

Well hoi, I have done a bit of number crunching and I have come up with something that might keep a spaceship afloat in an orbit, for at least a time, although it won't be terribly "near earth".

Propel the ship to, say 20,000 km, then, just as it starts to fall back towards earth, eject mass in the form of old shoes, bowling balls, whatever you have on board, so long as you are expelling mass down towards the earth. This ejection creates a force which by Newton's third law pushes the ship upwards.

(I feel that fuel, if expelled, would need to be in liquid form as gas would be removed via free expansion in the near vacuum).

How much mass needs to be ejected depends on how high up you are. At 20,000 km you need to dump roughly 10% of the mass of the ship. Obviously every time you drop a chunk of mass the equation changes (after the first dump of 10% your ship has only 90% of its original mass, etc...)

Go higher and your mass ejection requirements are lower however you are still going to eventually run out of ballast to release. Note that although vertical velocity is arrested for a period of time there still is horizontal motion. The ship will enter a type of orbit.

Yes, we can probably put things into space and push them a little while they are in low gravity but as for having rockets that can reach the moon, orbit and return, that is likely a fantasy.

[lux]

Would someone please explain how the air surrounding a rocket launched in the atmosphere causes it to move?

No equations please (not that I don't understand them -- they are just too easily used to obfuscate) but a diagram would be nice.

[Boethius]

Would someone please explain how the air surrounding a rocket launched in the atmosphere causes it to move?

No equations please (not that I don't understand them -- they are just too easily used to obfuscate) but a diagram would be nice.

Hello, lux,

I'm not sure if what you're asking falls under the scope of this discussion. The question is not how do rockets work in the atmosphere but will they work in the vacuum of space.

If you are interested in atmospheric rocketry there are many forums on the net to assist. It is a complicated subject involving fluid dynamics, airflow, air density, etc... I don't feel that any of it applies to space which has no atmosphere. A greater understanding of how rockets work in the atmosphere may be intellectually pleasing but we have to lay all of that knowledge to the side when we enter a discussion about space.

As for how formulas can be used to obfuscate, I am very, very aware of this. Saying we should avoid them when evaluating NASA's claims is like saying we should not look at their pictures because they can be manipulated by computers. It is the very purpose of this thread to investigate their equations, to see if they are fraudulent. Fraudulent equations are important pieces when it comes to uncovering a scientific hoax to my way of thinking. Keep in mind that is not necessarily the equations in and of themselves that are to be seen as frauds (although sometimes they are silly) it is the model that they use to create them which should be seen as pure fantasy, going against the principles of science and chemistry.

[lux]

In my quest for the elusive straight answer I will try rephrasing the question:

The title of the thread is: Why Rocketry Doesn't Work in the Vacuum

Now, in view of the fact that ...
1) A vacuum is an absence of atmosphere.
and
2) Rockets do fly when in an atmosphere

My question then becomes: (Assuming the rocket is supplied with oxygen so its fuel can burn) When you remove the atmosphere and thus create a vacuum what are you removing as far as the rocket's ability to move is concerned?

Or, to put it another way:
When a rocket flying in the atmosphere enters a vacuum what change takes place that causes the rocket to no longer be able to fly as it did before?

[Boethius]

Hoi, I have thought more about your interesting questions about creating pressure imbalances within a rocket as a way to create thrust.

[Space, for the purposes of this posting and all subsequent ones unless otherwise specified, is an environment without gravity or atmosphere. It is completely devoid of molecules or forces. Nothing acts on an object in space nor does any object act on space.]

If a space ship converts liquid fuel (potential energy) to accelerating gasses (kinetic energy) and then to a pressure imbalance against the combustion chamber (potential energy again) all it has done is moved energy around in a circle without doing any work.

In physics work is done only when energy leaves the boundary of a system. Since the rocket in this example has no place to deliver it's energy, (nothing borders the rocket: no atmosphere, no ground, no water, no gravitational field), then the energy stays within the rocker forever, doing no work and hence the rocket does not move.

So, looking at two models of rocket thrust
1. If we open the exhaust to let out gas free expansion takes over and no work is done. (NASA model)
2. If we create an imbalance inside the ship's combustion chamber we are in a closed system and no work is done. (Postulated alternative model)

[lux]

In physics work is done only when energy leaves the boundary of a system.

This statement differs greatly from this definition of work:

In physics, a force is said to do work when it acts on a body so that there is a displacement of the point of application, however small, in the direction of the force. Thus a force does work when it results in movement.

[Boethius]

In physics work is done only when energy leaves the boundary of a system.

This statement differs greatly from this definition of work:

In physics, a force is said to do work when it acts on a body so that there is a displacement of the point of application, however small, in the direction of the force. Thus a force does work when it results in movement.

Take a charged battery as an example. It is possible for the battery to exert a force without energy leaving the battery?
As per the equation Work = Force x Distance a battery does no work, generates no force until it's energy is passed to some object outside of the battery.

Perhaps it was unclear that I was referring to a closed system in my previous post. A closed system is one where no energy is exchanged with any object outside of itself. A ship in space represents a closed system as it does not interact with space and space does not interact with it nor does a ship in space interact with any field or force. If a ship cannot transfer energy to some object or entity outside of itself, how does it use its energy, potential or kinetic, to do work?

[hoi.polloi]

So, looking at two models of rocket thrust
1. If we open the exhaust to let out gas free expansion takes over and no work is done. (NASA model)
2. If we create an imbalance inside the ship's combustion chamber we are in a closed system and no work is done. (Postulated alternative model)

I read these to mean:

1. No work is done at the time free expansion takes over.
and
2. Imbalance creates vibration that - when settled - results in no work being done.

However, does that still leave open the possibility for:

The front part of the chamber to warp in the opening of a vibration, followed by the free expansion 'take over'?

---

Also, to address the crux of lux's grievance with Boethius' writings, let me try to rephrase the 'problem':

If a balloon is somehow situated in space and its end were opened, it would collapse instantly, all its helium or air being released without any real struggle to do so, and this would theoretically result in no momentum for the balloon. However, if the collapse didn't go perfectly and some part of the balloon had to squirm and squiggle to let the last bit of air out of itself, isn't it likely that the balloon's sudden deformity would cause it to spin, dash or tumble? Nothing is holding the balloon in place so it is free to go nuts. Are we assuming — even given a flawless, precision opening of its end — this would result in a perfect collapse, revealing no imbalance in the rubber skin, in the air itself, etc.?

Similarly, a perfect jet engine that could somehow survive the journey into a pressureless environment, and somehow maintain use of the liquid fuel combustion machine, should be going through some kind of rapid transformation as its fuel were exiting in whatever form.

lux seems to be asking if it is the rapid and violent transformation itself which is propelling the rocket through the air, rather than a build-up of pressure beneath and/or behind the rocket. So, is it?

We are not concerned about the philosophical or scientific idea of whether the subject is using perfect definitions of potential energy, kinetic energy or work. We are concerned with its ability to move from some designated relative point from Earth to a different controlled distant point — point A to point B, so to speak — on a course that its pilot(s) intend(s).

[Boethius]

In my quest for the elusive straight answer I will try rephrasing the question:

The title of the thread is: Why Rocketry Doesn't Work in the Vacuum

Now, in view of the fact that ...
1) A vacuum is an absence of atmosphere.
and
2) Rockets do fly when in an atmosphere

My question then becomes: (Assuming the rocket is supplied with oxygen so its fuel can burn) When you remove the atmosphere and thus create a vacuum what are you removing as far as the rocket's ability to move is concerned?

Hello lux, I hope the following answers are straightforward enough for you. Here is what happens to a NASA style rocket powered by liquid propellant when it turns on it's engines in the vacuum of space:

1) The gasses inside the rocket do not to produce a force as they exit
In the vacuum of space the accelerated gasses inside the ship's nozzle are no longer pushed out of the ship. They enter the vacuum via the principle of free expansion (without performing work) and thus do work neither against the rocket itself nor the vacuum of space.
=>No work done by gasses inside of the ship

2) The gasses that leave the rocket do not produce a force once they have exited
In the vacuum of space the gasses that exit the rocket do not accelerate, they move at a constant velocity forever. If an object (including a molecule of gas) travels without accelerating it cannot produce a force. Hence the rocket produces no force.
=>No work done by gasses outside of the ship

I do not see where the force comes from that moves a NASA space rocket.

You have been asking me, I believe, to explain how rockets work in the atmosphere and I continue to say that I do not feel it's worthwhile to investigate the subtleties and nuances of atmospheric flight. The question at hand is,
do rockets produce thrust in space via NASA's theories and equations or is it all part of the same great space hoax?

[Boethius]

So, looking at two models of rocket thrust
1. If we open the exhaust to let out gas free expansion takes over and no work is done. (NASA model)
2. If we create an imbalance inside the ship's combustion chamber we are in a closed system and no work is done. (Postulated alternative model)

I read these to mean:

1. No work is done at the time free expansion takes over.
and

Yes, hoi. Also remember that the only work that can possibly be done on the ship is due to the expansion of the gasses as there is no gravity or other force available to accelerate it. If the gas in the ship is not allowed to do any work (prohibited by free expansion) the ship has no source of thrust.

2. Imbalance creates vibration that - when settled - results in no work being done.

However, does that still leave open the possibility for:

The front part of the chamber to warp in the opening of a vibration, followed by the free expansion 'take over'?

The issue is that the ship is a closed system much like a charged battery. There is nowhere for the energy to go, no way for it to do any work until it is connected to something external. The ship is perfectly insulated by space.

Yes, the ship can deform, bend, crinkle, etc... but this will not generate work. Much in the same way that while you cannot lift yourself off the floor by the scruff of your neck, because you and the floor are a closed system under influence of gravity and friction. Still, you can pull out your teeth, poke out your eyes, etc... (you can twist and deform your body but you cannot generate force enough to leave the floor).

Note that you can jump off the floor when you add potential energy by flexing your knees. This amounts to opening the system (interacting with gravity to create more force).

Also, to address the crux of lux's grievance with Boethius' writings, let me try to rephrase the 'problem':

If a balloon is somehow situated in space and its end were opened, it would collapse instantly, all its helium or air being released without any real struggle to do so, and this would theoretically result in no momentum for the balloon. However, if the collapse didn't go perfectly and some part of the balloon had to squirm and squiggle to let the last bit of air out of itself, isn't it likely that the balloon's sudden deformity would cause it to spin, dash or tumble? Nothing is holding the balloon in place so it is free to go nuts. Are we assuming — even given a flawless, precision opening of its end — this would result in a perfect collapse, revealing no imbalance in the rubber skin, in the air itself, etc.?

From the experiments I have read about when gas exits via free expansion it does not generate heat, that is the gas molecules do not "fight to get out", they don't bump into each other or push each other out of the way. It is an orderly exit which makes sense if no work is done. Therefore the balloon should collapse without motion.

Similarly, a perfect jet engine that could somehow survive the journey into a pressureless environment, and somehow maintain use of the liquid fuel combustion machine, should be going through some kind of rapid transformation as its fuel were exiting in whatever form.

lux seems to be asking if it is the rapid and violent transformation itself which is propelling the rocket through the air, rather than a build-up of pressure beneath and/or behind the rocket. So, is it?

Discussing the mechanics of rocket flight in an atmosphere is a potential quagmire that I see only having value after the question of space flight is more or less concluded one way or the other. The problem is atmospheric flight is experimentally verifiable, well-studied, provable and extremely complicated. Once a discussion starts down this avenue it would be very easy for someone to drag it out forever. Rather than have an army of fluid mechanics/aerodynamic experts come crashing the party, given that these disciplines do not apply to space, lets keep our eyes on space and what actually does/can go on up there.

We are not concerned about the philosophical or scientific idea of whether the subject is using perfect definitions of potential energy, kinetic energy or work. We are concerned with its ability to move from some designated relative point from Earth to a different controlled distant point — point A to point B, so to speak — on a course that its pilot(s) intend(s).

Well, I would say the first question is, if a ship is motionless in space, not under the influence of gravity and having no momentum, will NASA rockets allow the ship to move?

If we give the ship some initial momentum we are increasing the problem's complexity. If the rocket doesn't move from a dead stop then what is it, just a big cannonball with lights and sparkles?

[lux]

You have been asking me, I believe, to explain how rockets work in the atmosphere and I continue to say that I do not feel it's worthwhile to investigate the subtleties and nuances of atmospheric flight. [/b]

I asked you for the difference between atmospheric flight and flight in a vacuum. Since we know that rockets fly in an atmosphere and since you are introducing the idea that they won't fly in a vacuum, I am asking you what the specific difference is between these 2 conditions such that the rocket won't fly in a vacuum.

Further, I am not asking for any "subtleties and nuances" of anything. Just a simple straight answer to the question asked.

Since you haven't given a straight answer to any of the questions I have asked you so far I presume this will be the case here so I will answer my own question:

In the case of a rocket flying through the atmosphere with its own supply of oxygen for burning fuel the only atmospheric factor affecting the rocket is air friction slowing the forward speed of the rocket.

The atmosphere provides no other force and is in no way assisting the forward motion of the rocket.

Therefore when this rocket enters a vacuum the only possible result is the removal of air friction thus speeding up the flight of the rocket.