Does Rocketry Work beyond Earth's atmosphere?

[Penelope]

Postby patrix on March 28th, 2018, 7:09 am
Oh please Penelope I am not "ignoring/invalidating" Newtons 3rd. Or "his" 1 or 2 either.

Patrix, it's my understanding that the very heart of your argument is that "Newton's 3d is not valid in space (vacuum). I agree with you that your version of Newton's 3d isn't valid in space.

I'm making the point that your version of Newton's 3d doesn't work here on Earth either, because it is a mistaken interpretation of Newton's 3d.

Patrix said, I'm explaining that they never come to play when gas expands in vacuum since no action/reaction occurs.

I can't think that discussing the effects of a mistaken interpretation of the Free Expansion experiment upon a mistaken interpretation of Newton's 3d will possibly illuminate the matter. I challenge you to defend your version of Newton's 3d here on earth where we are aided by observation and have the hope of some intuitive knowledge or perception.

Let me show you why I think your version of Newton's 3d is false.

As you know, Newton's 3d states that when material objects interact the force that object A exerts upon Object B must be synchronous and equal in magnitude to an obligatory force which Object B exerts on Object A, but in a direction 180 degrees opposite. "Obligatory" because there are no unmatched forces, there are only paired forces.

STANDARD NEWTON'S 3D AT LIFT-OFF

At lift-off the force vector which indicates the rise of the rocket is a line from bottom to top of the rocket with an arrowhead at the top. This vector MUST be matched by one in the opposite direction, so we draw another in the opposite direction indicating en masse the many exiting molecules and particles of the exhaust. The exhaust arrowhead points downward 180 degrees opposite to the rise of the rocket. Newton's 3d is satisfied and, provided the mass x velocity of the exhaust is sufficient, the rocket rises.

YOUR VERSION OF NEWTON'S 3D AT LIFT-OFF

Let's start at the element that you have added to Newton's 3d, the "push off" of the exhaust gases upon the ground as a means of raising the rocket: The exhaust vector points downward and is met by one pointing upward from the ground, indicating that the ground is exerting a resistant force equal in magnitude to that of the exhaust vector. Now what? We have stasis, cancellation of forces. How do we get from this a vector to push on the rocket? (Not even a supplementary force.) You have paired the forces of your entities in such a way that your rocket will never rise.

I say "you", Patrix, but I mean anyone's adherence to the idea that a rocket can lift off only if its exhaust pushes on the ground; or propel itself only by pushing on air. It's just that you've been the only one brave enough to speak up. And I do appreciate your response.

I don't mean to be unresponsive to your point about Free Expansion, so I will say this much: The reason for Boetius' inserting it into the discussion was to give scientific buttress to the idea that rockets cannot propel themselves by trying to gain traction through spewing exhaust against vacuum.

But Patrix, this is not an idea at issue. I agree. I'll wager so would FervidGus. No one doubts that pushing on vacuum will get you nowhere; in fact it is impossible to push on vacuum, for it doesn't resist and you therefore have a violation of Newton's 3d regarding paired forces. You try, right now, to push on air & you'll see what I mean.

Rockets don't use this method of propulsion; they have Newton's 3d. The real one, sans pushing their exhaust against ground, air or vacuum.

[simonshack]

Dear Penelope,

Please read & view this old post of mine (from 2013): http://cluesforum.info/viewtopic.php?p=2385791#p2385791

Then, come back to us and explain :

1: Why do NASA / ESA / SpaceX rockets always lift off sooo very slowly?
2: Why do real amateur rockets (such as Steve Eves' 1/10 scale replica of the [alleged] Saturn V ) lift off ... like a shotgun's bullet?

See, it doesn't really matter what Isaac Newton has to say about this. We can, more simply, use our own brains to detect the fakery being sold to us.
If you really believe that those two silly TV ladies are standing in front of real rocket launches, I'm afraid that you are beyond help (sorry, no offense meant).

Needless to say, Steve Eves' 1/10-scale replica rocket didn't make it out from our atmosphere: it only reached one kilometer or so of altitude - and then fell back to Earth (he states that his rocket was completely full of fuel - and had no 'payload', such as astronauts, etc...). So what sort of magical technology (or special fuel) do you think NASA has to make a 10X larger rocket with three adult men aboard reach 100 km of altitude - and beyond (all the way to the Mooon - and back)?

As for your (old & tired) example of a person throwing an object from a wheeled desk chair on a smooth concrete surface, it just doesn't seem to be comparable to the forces necessary to lift a person vertically up from the ground - so as to escape 'gravity' - and fly up in the sky at great speeds :

Yet, NASA tells us that - as rockets exit our atmosphere, they keep rising thanks to the rocket's fuel being flung out of the same!
"Newton's 3d law!", they say... I say: duh!

Please get real, dear Penelope - you are obviously a very smart (yet ever-so-slightly brainwashed) individual!

(Dearest Penelope, please excuse me - but I think we are all very, very weary of having Newton's 3d law being used to support the idea of space travel. Thanks for your kind comprehension)

[patrix]

Rockets don't use this method of propulsion; they have Newton's 3d. The real one, sans pushing their exhaust against ground, air or vacuum.

Oh, Newtons 3d the real one! Forgot about that one

For the third time, I have no problem with Newton's laws of motion, except maybe that I doubt if he actually is the one who formulated them. But the laws are perfectly fine and valid.

Thing is, they never come into play in the rockets in vacuum scenario and I have explained why, and it's been proven with controlled experiments.

But let's give another example just for fun

Imagine you have a popcorn machine on wheels in an empty room. Now would the machine move if the finished popcorns came out at the back? Well probably eventually when a sufficient pile of popcorns had built up so that the newly popped popcorns could act against them.

Same thing with a rocket in vacuum. If the molecules resulting from a gas expansion have nothing outside the system to interact with then no reaction and hence no Newton.

And there can be no "piling" in an unrestricted vaccum. The molecules following the first cannot act on them since they all drift away at constant speed in the frictionless vacuum.

[Penelope]

Simon and Patrix,

Notwithstanding distractions like Free Expansion of gases, how airplanes work, the extent of the space program hoax, whether numerous "lift-offs" are fakery, and evidence pertaining to all-- notwithstanding all this I cleave to the single point which I made in my opening comment and expressed at length in my March 28 7:09 post.

My demonstration that a rocket on lift-off could not benefit from any force consequent to the exhaust hitting the pad or ground demolishes CluesForum's argument that this force is necessary for lift-off. Likewise, that rockets derive force from the exhaust hitting air.

It does not mean that all rocketry problems are solved, Van Allen belt, etc, or that the oligarchs choose to spend resources on space rather than on our subjugation.

I know that neither of you are interested in this analysis new to CF, and I will therefore spare you the longer explanation of how Newton's 3d works, in favor of explaining how one aspect works:

As I sat in my wheeled chair on the smooth surface and threw the sandbag which resulted in my chair moving backwards I noticed that the determining instant was the last one prior to the sandbag separating from my palms. When we had separated by a hairsbreadth, both our propulsions had already been determined and neither could be affected by what became of the other. (ahem, ahem) Capisce?

I challenge anyone on this site to disprove my interpretation of Newton's 3d in the March 28 7:09 post or on this one. I welcome all questions or comments concerning the point that I am making: That rocket lift-off & propulsion are not accomplished via exhaust pushing against ground or air.

[Penelope]

by patrix » March 28th, 2018, 1:02 pm
I have no problem with Newton's laws of motion. . . perfectly fine and valid. they never come into play in the rockets in vacuum scenario

Patrix, your belief that Newton's 3d doesn't come into play in vacuum is because you interpret Newton's 3d to mean that rockets travel by pushing against either air or ground. This is expressly denied by Newton's 3d because it deals only with relationships between pairs. Air or ground makes 3.

You may avow Newton's 3d or that third entities like air or ground determine the outcome of paired forces transacted by paired material objects-- namely the rocket and its exhaust one instant before it separates from the rocket. You can't have both; you have to choose. Please review my discussion last post concerning force vectors. Just as numbers are necessary for math, force vectors are necessary to analyze forces.

Further, regardless of the misinterpretation & misapplication of the Free Expansion experiment, I'm sure that you are aware that vacuum is not a force, and therefore cannot stop or slow speeding bits of exhaust. However this is actually irrelevant because the transactional force between the exhaust & rocket will have already taken place, an instant prior to separation. This means that the force (resulting in motion) will already have been apportioned between them, so that nothing which happens to one can now affect the other.

[patrix]

Patrix, your belief that Newton's 3d doesn't come into play in vacuum

That no work occurs during free expansion is not a "belief". It is a proven physical fact.

[pov603]

Without wishing to trivialise matters can someone consider the following?
A "closed tube" is managed to be placed into "space" in an area relatively free of gravity but, nevertheless, supposedly in a vacuum.
We then insert a human within the "tube" and ask that he spend time walking to one end of the "tube" and running as fast and hard as he could towards the other end of the "tube" smashing into the wall/closed end, then calmly walking back to the other end to repeat the exercise over and over again.
Would we achieve forward momentum in this friction-less abyss?
Would a "transactional" force between the "tube" & man have already taken place, an instant prior to the impact?
Would it be safe to assume that the "tube" would not only move forward but also go faster and faster, after each repeat of the above, as there would be an absence of friction/air-resistance to slow it down?

[patrix]

Without wishing to trivialise matters can someone consider the following?
A "closed tube" is managed to be placed into "space" in an area relatively free of gravity but, nevertheless, supposedly in a vacuum.
We then insert a human within the "tube" and ask that he spend time walking to one end of the "tube" and running as fast and hard as he could towards the other end of the "tube" smashing into the wall/closed end, then calmly walking back to the other end to repeat the exercise over and over again.
Would we achieve forward momentum in this friction-less abyss?
Would a "transactional" force between the "tube" & man have already taken place, an instant prior to the impact?
Would it be safe to assume that the "tube" would not only move forward but also go faster and faster, after each repeat of the above, as there would be an absence of friction/air-resistance to slow it down?

Of course it would not move. I mean it could bounce back an forth but this would never cause it to travel in any different direction than it did in the first place. If it did it would be a violation of Newtons laws of inertia, that rocket believers hold so dearly to their chest.

If the body is not affected by an outside force it will keep its current direction and momentum. The human inside is not an outside force.

Take it from the horses mouth: https://www.grc.nasa.gov/www/k-12/WindT ... otion.html

[pov603]

Believe me, I would not have expected it to move either (almost like trying to pull oneself up by ones own laces...it ain’t gonna happen...), nevertheless we are told that satellites use Reaction Wheels to rotate etc.
Anyway, back to the tube, consider that when running at the wall of the tube it miraculously opened for a nano-second and allows the human to pass through.
What happens to him and what happens to the “tube”?
They both move in opposite directions?
He moves in one direction and the tube remains stationary?
Neither of them move?

[patrix]

Believe me, I would not have expected it to move either (almost like trying to pull oneself up by ones own laces...it ain’t gonna happen...), nevertheless we are told that satellites use Reaction Wheels to rotate etc.
Anyway, back to the tube, consider that when running at the wall of the tube it miraculously opened for a nano-second and allows the human to pass through.
What happens to him and what happens to the “tube”?
They both move in opposite directions?
He moves in one direction and the tube remains stationary?
Neither of them move?

An action/reaction can only occur when a force outside the system/body acts on it. This is why the gun/bullet scenario would work in the assumed frictionless and gravity free space. The bullet becomes something outside the system that the gas expansion from the gunpowder can react against. So if the tube is open in one end and that human jumps, pushing the tube one way and itself the other way, the tube would change direction. But that can never occur as long as that human remains inside the system.

[bongostaple]

by patrix » March 28th, 2018, 1:02 pm
I have no problem with Newton's laws of motion. . . perfectly fine and valid. they never come into play in the rockets in vacuum scenario

Patrix, your belief that Newton's 3d doesn't come into play in vacuum is because you interpret Newton's 3d to mean that rockets travel by pushing against either air or ground. This is expressly denied by Newton's 3d because it deals only with relationships between pairs. Air or ground makes 3.

You may avow Newton's 3d or that third entities like air or ground determine the outcome of paired forces transacted by paired material objects-- namely the rocket and its exhaust one instant before it separates from the rocket. You can't have both; you have to choose. Please review my discussion last post concerning force vectors. Just as numbers are necessary for math, force vectors are necessary to analyze forces.

Further, regardless of the misinterpretation & misapplication of the Free Expansion experiment, I'm sure that you are aware that vacuum is not a force, and therefore cannot stop or slow speeding bits of exhaust. However this is actually irrelevant because the transactional force between the exhaust & rocket will have already taken place, an instant prior to separation. This means that the force (resulting in motion) will already have been apportioned between them, so that nothing which happens to one can now affect the other.

Your dismissal of air or ground making a total of three forces and not a pair, is fundamentally wrong. Anything fired out the exhaust of a rocket will be met with resistance from any kind of matter that's in that location, whether it's solid or fluid. The amount of resistance will be much higher in the case of solid concrete, for instance, than water, or air. But regardless of that, whatever the rocket emits is effectively pushing against what's just outside, and all matter takes some effort to move. Therefore your three things are just two things. The opposing force is highest for solids, and decreases for fluids.

This makes sense when you light a firework rocket, which accelerates from the ground very strongly, but then slows down. But for some reason, every 'space' launch I've ever seen on TV has the rocket lifting incredibly slowly from the launchpad, before apparently getting to tens of thousands of mph once out of sight. The only logical explanation I have for this slowness is that we are not watching a real thing.

Rocket thrust decreasing as the density of the outside medium decreases makes complete sense to me, and a natural extrapolation of the concept makes no surprise of tending toward zero thrust if the local material is a vacuum.

As regards the 'vacuum of space' though, I'm by no means wed to the idea that a vacuum is what 'space' consists of - as I'm certain man has never been there to find out.

By all means stick to theoretical arguments, but much of the history of space travel suggests that about 100km is pretty much the limit for any man-made technology to date. The US Air Force nudged up to that height with the experimental rocket planes , and encountered great difficulty staying there. If it was possible to go further, I very much doubt that the military, who were owning the effort then, would suddenly lose all interest and hand it over to a newly created civilian body, i.e. NASA. As a rule, when military are in posession of some technology that would allow military use, they get right on and use it, they don't give it away to a bunch of civilians.

[Penelope]

by patrix on March 28th, 2018, 9:39 pm
That no work occurs during free expansion is not a "belief". It is a proven physical fact.

You are sticking to your preference that we discuss the rocket in space first. And I am sticking to mine that we shall resolve the applicability of Newton's 3d to rocketry outside space first. In order not to annoy others with our endless repititions, I propose a compromise:

I promise on my honor to give a full and complete critique of Free Expansion of gases and its relationship to rocketry in vacuum after we have the resolution of the matter in atmosphere and on the ground. You know I didn't want to discuss Free Expansion at all until the earthly questions were resolved. Yet I have bent quite a bit on the topic and given you some indications. No more. Please discuss rocketry on lift-off and in atmosphere. Please, pretty please?

[Penelope]

pov603,

Thankyou for entering the fray. Until now Patrix, with a little help from Simon, has been holding down the fort. You question the effect of a man within a tube upon the velocity of the tube if he repeatedly crashes into one wall of it. It isn't a trivializing question, but one which requires an understanding of Newton's 3d. Will you permit me to transfer the situation out of space and into atmosphere or on the ground? I am quite insistent that we should resolve Newton's 3d with rocketry flight here before we transfer the problem to space/vacuum.

Newton's 3d refers to the paired forces of paired objects and how they affect each other. They may be flung apart, as my chair and the thrown sandbag, or the forces may cancel each other as when rocket exhaust pushes on the pad or you push on a wall which resists your push.

As I'm sure you realize, in order for the paired objects to be pairs whose behavior is described by Newton's 3d in the "flung apart" example they must be separate in mass. One may not be within the other. The sand bag acts as a part of the me+chair mass and has no effect on the chair's velocity if I make all the motions of throwing it but still maintain contact with my hands.

pov 603 said, Would a "transactional" force between the "tube" & man have already taken place, an instant prior to the impact?
Would it be safe to assume that the "tube" would not only move forward but also go faster and faster, after each repeat of the above. . . .

Yes, I knew someone would get me on this. For me, it is a grammatical conundrum. You may interpret it as something else, and I would like your thoughts on the matter. I explain it this way: If I describe the moment at which the two separating bodies (chair & sandbag) apportion the forces incumbent on their separation as occurring just prior to separation then I am stuck with your little man making his tube accelerate.

But if I describe that moment as occurring just after separation-- well, obviously the two masses aren't in contact and can't influence each other. So if I compromise and say "at separation" the picture in my mind's eye is somehow always of 2 things no longer touching. So should I say during separation? Perhaps I should. But then, at what point during separation? Surely not that last instant when only the fingernail of my right index finger is in contact.

[hoi.polloi]

Although we have had this same seemingly endless discussion about ten times in this thread already (with Penelope representing my excuses for rocketry that never actually add up to a feasible way to move beyond the atmosphere since moving beyond Earth's atmosphere is the discussion), it seems it's still a "mental hurdle" for people to understand that rocketry encounters serious issues once the momentum ends and gravity takes over.

However NASA seems to be hedging their bets as usual, since the latest in exciting space technology news includes phasing out rocketry. Yes, the latest from NASA and private spacecases is the following:

Rockets, people and satellites will "now" (as if it hasn't been done the same way for the last half-century) be brought up by balloon. In fact, a private company is considering a sort of "space ride" (with tickets in the several thousands of dollars per ride) as a means of bringing people up nearly to the Karman line (though I wouldn't put it past the rich industry moguls to build all their instruments specifically to lie to the pilots and all the passengers that it's going higher than it actually goes, by a smidgen) via balloon — and then descending through the release of flotation and finally parachuting back to Earth.

In addition, satellite launches are now speculated to be cheaper, safer and more ecologically sound by bringing a rocket up as far as a balloon will take it, and then launching from there. You might even hear spokespersons for NASA, Space X and other enthusiasts contradict themselves once more and say "the balloon brings you so high that gravity is significantly reduced and therefore launching from higher conserves resources".

This is what I've heard from one of my favorite astronomer friends and I couldn't come up with the words to query him before we were on to the next subject. Now it may conserve rocket fuel to bring us up by non-incendiary buoyancy, but to say there is less gravity at the Karman line is weird when contrasted with the notion that Earth's full gravity is almost fully present hundreds of kilometers from the surface, or so it's said. I guess we ought to bring that to the "What is Gravity?" topic so ... moving on ...

Erdgvarp.png (2.24 KiB) Viewed 5033 times

The point is it seems NASA is already smelling the end of their rocket fables. All it will take to cement the change in the public's imagination is some fluffed up "disaster" or "pseudo-disaster" or "narrowly averted catastrophe" that never took place; and we'll all be primed for the change to new, exciting balloon technology.



It's been balloons the whole time, with rockets for show and expensive (and maybe even somewhat wasteful) experiments, no doubt. And personally, I am coming to the appreciation that high speed lightweight military balloons and aircraft may be the best explanation for artificial so-called satellites. But in any case it seems "the age of rocketry" as we know it is presently little more than a marketing gimmick of the most expensive corporations to run: namely, imperial governments.

[Penelope]

by pov603 on March 29th, 2018, 1:07 pm
consider that when running at the wall of the tube it miraculously opened for a nano-second and allows the human to pass through. What happens to him and what happens to the “tube”?

How inventive you are. Back to me on the wheeled chair with a sandbag on my lap. Whether the chair (tube for you) moves backward away from the departing sandbag depends on at least three things. Obviously the velocity & mass of the departing item. If it's only a feather, regardless how fast (within reason) I make it depart by blowing on it, its departure won't move the chair. (too little mass)

Sufficient velocity of departure is also necessary if we are to move the chair: If I bend over and drop the sandbag 2 inches to the floor, the chair will not move backward.

But here is the factor you may not expect. If the action of departure by one of the paired entities is accomplished by a third entity, that action will not cause the remaining one of the pair to move. If a giant sucking vacuum (no pun) removes the sandbag from my lap at astronomical speed, my chair will not move backward.

If your man in the tube jumps to his death, and if his mass and velocity are sufficient, then your tube will move synchronously, in equal magnitude and 180 degrees in opposite direction. But before your little man contemplates suicide for the sake of our experiment I want to remind him that any velocity which he acquires from the passing wind (or any entity other than himself or the tube) will not contribute to the "reactive" movement of the tube.

Any energy internal to the man which adds to his velocity at? separation counts-- like getting a running headstart & leaping with all his might. Any energy from the tube which adds to his velocity also counts-- the use of pistons, compressed gases, etc.