Does Rocketry Work beyond Earth's atmosphere?

[Penelope]

by starfish prime on March 29th, 2018, 11:15 am
An object dropped and one projected forward from the same height will land at the same moment. There is no orbital velocity that an object can reach allowing it to simply freefall around the Earth without constantly consuming fuel.

You know, starfish, I originally thought this was correct. But upon reflection I have doubts: Imagine we have two pickup trucks drop off over a cliff's edge at the same instant. But one is going 5 mph & the other 85 mph. Surely the one going 85 would make a considerable inertial path pretty close to horizontal before he began his gravity-pulled descent. His path would actually be longer than that of the slow truck. Also his time to hit bottom.

We've all seen this "temporary defiance of gravity" by skiiers and skateboarders. It's actually just that their paths are the result of the gravity force vector at right angles to the horizontal inertia of motion vector-- with the resultant path being an hypotenuse whose dimension is largely determined by their initial velocity.

As for a velocity which would allow an object to orbit, defying a reduced gravity long-term, I wouldn't know how to compute that. Wikipedia says
Near the surface of the Earth (sea level), gravity decreases with height such that linear extrapolation would give zero gravity at a height of one half of the earth's radius

So at 2,000 mi above Earth we'd have 0 gravity. We don't want that. Is there a distance where satellites would neither fly off at 0 gravity, nor fall to earth? Since we do have natural satellites, it appears so. And it's logical that speed of orbit would help to offset gravity, allowing a lower orbit.

Do we have the fuel-carrying and other technology to get there? I haven't a clue. Obviously they've told us a lot of lies about nonexistent programs. It's possible that the lies dovetail with the constant refreshing of the "alien visitation" hoax. Another major psy-op that could be pulled out of the hat if it suits some scenario.

[Kham]

Penelope,

Why don’t you do your own research and THEN present your findings here at Clues Forum instead of presenting half finished thoughts expecting members to resolve your issues. I think we would all appreciate that.

You are engaging in tactics that are sucking time from members over tired old issues. How things fall is a pretty basic idea, a straight drop or the parabolic motion of projectiles. Perhaps you can start your research there and then make an awesome post of your findings of which you will be proud.

Take care.

[patrix]

I agree Scacredcowslayer and Kham. And if this is deliberate "noise making", (which I have no way of knowing) it's about seeding doubt. To accept that there's no way for rockets and satellites to work "because physics" is a hell of a leap. At least it was for me. Cognitive dissonance kicks in and looks for the slightest reason to be able to dismiss it.

But as it turns out, much of science, including physics have been turned upside down during the entire 20th century. Einstein, the "rocket equation" and so much more is utter propaganda BS.

I encourage everyone interested in physics to go back about hundred years, to unlearn and relearn. Look at the works of Joule, Thomson, Michelson and Morley for example. And this is possible from your armchair because of the wonders of internet :-)

A suggested starting point:
https://archive.org/details/baltimorelecture00kelviala

Edit:
Penelope made a comment that was derailed and rightfully so. This is supposed to be a thread about Rocketry and I've slided away from that subject as well. But forgive me for commenting on it in an edit. I will also keep non rocketry issues elsewhere from now on.

Patrix, I guess Isaac Newton would be even safer then, since he lived in the 17th century.

Penelope, it's not about the age of the science, it's about if it follows the scientific method that stipulates that if you have an hypothesis, you should try to find observations and experiments that falsify your hypothesis. And if you and others fail to do this, then you have something more than a hypothesis - a theory and if it stands the test of time, a law. But this principle has eroded. It started as far as I know with Kepler who made elliptical orbits to seemingly make the Copernican model work. A hypothesis that's been falsified through observations as Simon shows in his book. Then we have Newton and his "laws" of gravity. Another hypothesis disproven by observations, if we are not willing to accept binary stars have absurdly high masses. Something I'm not willing to do because there are no evidence what so ever that could be the case.

So the entire field of science needs a renaissance, and hopefully this forum and its discussions is the first steps towards that. And at the bottom lies in my view a media that for a very long time has been about selling lies and hiding the truth. Einstein, Kepler and Newton has been raised to the skies by media, even though their hypotheses have been falsified. And the ones who have not like Joule-Thomson expansion, are ignored. So I'd definitely say this falls into the realm of media fakery.

[Altair]

Ok, here we go again... Sorry for the crude graphics, but it's much fasterthis way than fiddling with graphing applications.
To illustrate my, point, the one and only thing that can move a rocket (or any other thing) upwards is a FORCE exerted in the same direction as the desired movement. That's physics 101.

As we're dealing with gases, the one and only way a gas can exert a force upon a solid body is by means of PRESSURE. We're not absolutely concerned about action-reaction and such niceties, because we don't need to know how much and how fast the gas is ejected. That is just a nice-to-know datum, but what we want is just to have the maximum possible force applied to our dear rocket. Right?

So, as we see in the graphic, the most important thing is to build a huge pressure in the combustion chamber. Being it a closed recipient except for one end (where the gases exit), assuming a more or less homogeneous pressure, the horizontal components of the force neutralize themselves leaving only the vertical component, that would be dependent upon the throat's surface, as only in this part of the chamber pressure is zero or near zero.

The same would happen also for the nozzle, but forces there would be much less, as it is the pressure.

Now, the problem is whether it's possible to maintain such pressure in the combustion chamber in a vacuum, or the gases would be effectively 'sucked' out of it as soon as they're generated. And no pressure, no thrust! It's that simple.

I've looked at the purported parameters of a 'real' rocket engine as the Merlin 1C: https://en.wikipedia.org/wiki/Merlin_(r ... #Merlin_1C



This thing is supposedly capable of generating 480 kN of thrust, roughly 48 tons of weight. To make an idea of it, that's enough to lift three 15 ton fully loaded articulated trucks. Yet, I cannot see any massive attachment fixtures capable of sustaining such a force and transmit it to the rocket's structure. Another issue is that most of the force is applied to the combustion chamber, which de facto would be 'pulling' from the inside.

Also, the purported pressure inside the combustion chamber is 6.7 MPa. So if we want to have a forward thrust of 480 kN, we need a 'zero pressure' area in the bottom of the chamber of 0.07 sq. meters, what tells us that the throat should have a radius of 0,011m, or 11 cm, which more or less could match the photo.

Now, all what rests is to find out whether such pressure in the chamber can be maintained in vacuum conditions. In fact, that would be a near-perfect implementation of the Joule-Thompson box experiment!

As a corollary, it's quite funny that all discussions verse about the 3rd law, the gas exit speed and so on, which are absolutely irrelevant points.

[Altair]

Interesting vintage documentary about the attempts to build a nuclear powered rocket. Funnily enough, they performed just ONE test plugging the nozzle to a vacuum chamber in order to test how well it would perform in space...


full link: http://www.youtube.com/watch?v=Zm7PNlK5Aco

[patrix]

Altair wrote:

As we're dealing with gases, the one and only way a gas can exert a force upon a solid body is by means of PRESSURE. We're not absolutely concerned about action-reaction and such niceties,

I just want to clarify that the pressure inside the system/rocket has no significance. In order for a system to move it must be able to create an external force. And the only way for a rocket to do that is by creating a pressure difference outside itself. It doesn't matter if there's high pressure inside the rocket. In the atmosphere, the difference is mainly created when the rocket heats up the air behind it, causing it to expand and thus pushes the rocket forward. In a vacuum however, there is of course no way to create the needed pressure difference. A gun works (once) because it can create this pressure difference between itself and the bullet (that is external to the system since it leaves it). When the bullet is exiting, there is higher external pressure on that side of the gun.

[molodyets]

Now, the problem is whether it's possible to maintain such pressure in the combustion chamber in a vacuum, or the gases would be effectively 'sucked' out of it as soon as they're generated. And no pressure, no thrust! It's that simple.

Very nice illustration and description! And yes, it is simple.

Just one clarification.

Maintaining such a pressure differential depends more on the area of the escape path. As an extreme example, consider the path as a tiny pin hole. Sure, that size can maintain the pressure, like a gas cylinder. Only a small amount of gas can flow through it. But the larger the size, the more gas can escape until the hole can't maintain the pressure. It's funny though, when mainstream engineers/scientists think that showing the formula proves the rocket thrust. I don't think that enough gas can escape at a high enough speed to give the required thrust.

In space, the pressure differential is only 1 atm more than at the surface of the Earth so the vacuum of space is not that harsh of an environment for the rocket. As an example, if the pressure inside the chamber is 500 atm, the pressure differential for the combustion chamber at the surface of the Earth would be 500atm-1atm = 499atm. In space it would be 500atm - 0atm = 500atm.
499atm versus 500atm is not that big of a difference.

BTW, gas is not sucked out by the vacuum. It's just like in our atmosphere, gas always flows from higher pressure to lower pressure --> it's pushed.

[Flabbergasted]

As an example, if the pressure inside the chamber is 500 atm, the pressure differential for the combustion chamber at the surface of the Earth would be 500atm-1atm = 499atm. In space it would be 500atm - 0atm = 500atm. 499atm versus 500atm is not that big of a difference.

If we calculate the difference as a ratio, we get:
500 : 1 = 500
500 : 0 = infinite

It is not a question of a difference in absolute numbers, but of the absence of an external medium (as far as we know). In the near-absolute vacuum of space there is no medium to interact with, thus no transfer of force between the rocket and the environment, thus no propulsion (beyond a minor recoil effect).

[patrix]

thus no propulsion (beyond a minor recoil effect).

And not even that I would say. The gas expansion has to act on something for an action/reaction (recoil) to be created. I don't know if this video has been up before. I discovered it when doing a presentation about the implausibility of rocketry in space the other day. I find it rather telling that 3 minutes into the video, when the presenter explains action/reaction, he holds up a pen in one hand, representing the action, but holds nothing in the hand representing the reaction. Perhaps a subtle hint?


full link: http://www.youtube.com/watch?v=2UcQC23sZ-I

Original link: https://youtu.be/2UcQC23sZ-I

[kickstones]

*
Interesting, maybe a subtle hint that rocketry cannot get beyond Earth's atmosphere?

Successful Orion abort test is good news for NASA astronauts
https://bgr.com/2019/07/02/orion-abort- ... sa-launch/

NASA describes how things unfolded:

The Orion test spacecraft traveled to an altitude of about six miles, at which point it experienced high-stress aerodynamic conditions expected during ascent. The abort sequence triggered and, within milliseconds, the abort motor fired to pull the crew module away from the rocket. Its attitude control motor flipped the capsule end-over-end to properly orient it, and then the jettison motor fired, releasing the crew module for splashdown in the Atlantic Ocean

A suite of 12 data recorders helped collect data on the launch and abort procedure, and all that information will be closely studied by NASA in order to better understand exactly how well the abort went. That said, initial impressions appear to be very good, and Orion seems to have performed its duty well.

“We’re building the most powerful rocket in the world to send astronauts to the Moon in the Orion spacecraft for Artemis missions,” NASA’s Bill Hill said in a statement. “With this exploration system designed to safely carry humans farther into space than ever before, we’ll also have an equally powerful launch abort system that will pull the crew away if there is a problem with the rocket during the early portion of ascent.”

[simonshack]

*

Father and 10-year-old son dialogue (about NASA) - in 2019




- Daddy?

- Yes, sonny?

- I just read that NASA is currently testing a rocket designed to carry humans into space.

- Yup, sonny - I heard that too last night, on TV.

- But didn't NASA send many astronauts to the Moon and back, like 50 years ago - without a single hitch? I mean, no one died!

- They sure did, sonny. But you see, NASA has now lost that technology - and they have to start from scratch all over again.
And here's why: imagine if you wished to build a Ford Model T today...



... well sonny, you simply wouldn't find anyone capable of building it - because those who knew how to build it have all passed away.

- Oh. I see.

[long pause / silence / young brain cells processing]

[-----------*crickets*----------------]

- Daa-addy!!!... You're kidding me, right?






*****************************************************



full link: http://www.youtube.com/watch?v=16MMZJlp_0Y

From Wikipedia:

"Donald Roy Pettit (born April 20, 1955) is an American chemical engineer and a NASA astronaut. He is a veteran of two long-duration stays aboard the International Space Station, one space shuttle mission and a six-week expedition to find meteorites in Antarctica. As of 2018, at age 63, he is NASA's oldest active astronaut."

https://en.wikipedia.org/wiki/Donald_Pettit

I have to laugh: Donald Pettit was born on the exact same day (April 20, 1955) as my estranged elder brother, Mario - a compulsive liar and mofo (he stole the bulk of my mother's lifetime savings). Perhaps there's some truth in astrology after all?...

[antipodean]

I have to laugh: Donald Pettit was born on the exact same day (April 20, 1955) as my estranged elder brother, Mario - a compulsive liar and mofo

They both share a birthday with the Gentleman mentioned below. Bit ironic as NASA allegedly pinched Nazi technology.

https://www.google.com/search?biw=1358& ... gPnju55bTw

[simonshack]

I have to laugh: Donald Pettit was born on the exact same day (April 20, 1955) as my estranged elder brother, Mario - a compulsive liar and mofo

They both share a birthday with the Gentleman mentioned below. Bit ironic as NASA allegedly pinched Nazi technology.

https://www.google.com/search?biw=1358& ... gPnju55bTw

Thanks Antipodean! You made my day!

[nokidding]

Just got to the end…may I add something from personal experience? I burnt off lot of gas at high rates from drilling rigs. I was interested in the thread because a few years back I tried to calculate the thrust produced by a horizontal gas flare - someone had angled the flare tip up and I was concerned that the down thrust would exceed the design utilisation for the boom suspension. This was a gas well being flowed full bore for production testing. Like people here I assumed the gas flare itself pushed back.

When you watch a high rate gas stream exiting an open pipe under pressure and burning off you see the ignition point commences a few metres out and appears to race back unstably. The gas needs to draw in Oxygen from the surrounding air to burn. This runs counter to the idea that pressure is built up by resistance of the air. However between the tip and where it starts to burn there is clearly a high pressure jet.

Beyond the ignition point you have what looks much like a rocket launch - imagine 2000 m3 / min shooting out of a 6 inch pipe and igniting (you are perhaps 20 - 30m away – the noise is extreme). The flare is obviously dissipating huge energy but does it push back? Any force has to be pressure in the burning gas stream - and this is only seen at the nozzle / pipe exit. Air pressure may make this greater than in a vacuum but only by 1 bar or 15 psi (at sea level).

What relevance has a gas flare to rockets in space or in air? The rocket engine produces a stream of gas, much like the oil rig flare boom. It may be extremely hot and the product of a chemical reaction, but it is still just gas. The nozzle is an open pipe much like the flare tip, but designed to maximise the velocity of the gas (in speed and direction).

How does pressure build up in a pipe/nozzle with an open end and a void beyond? Because gas is pushing from behind against the inertia of the moving gas forcing it to increase its speed. Force = Mass x Acceleration (not Mass x Velocity as someone stated here). Acceleration is the key to it. I could model the mass flow rate etc using process engineering software so could then put a figure on the thrust.

Both air and vacuum provide a void for the gas to expand into. The pipe/nozzle stays pressurised as long there is sufficient gas supply to accelerate the expanding gas out of the open end into the void. The gas goes one way and the rocket goes the other, or stays put (hopefully) in the case of the flare boom.

To those in doubt just consider - this is the same Law that makes the image of the ‘plane’ going into the WTC so unphysical.

nokidding

[Altair]

Very good explanation, nokidding. In fact it's quite puzzling that all pop physics explanations about how rocketry works are centered around Newton's 3rd law, blindly assuming that if you eject a given amount of matter at a given speed from a rocket, it will generate an equal and opposite force upon the later. While from an engineering perspective, if you want to accelerate a body, you must exert a pressure against it, so all calculations should be centered around where and how much of this pressure is applied.

Extrapolating from your rig example, we could say that the rocket would indeed be subject to some force, but this would be only generated by the fuel being accelerated by the pumps (that would apply pressure upon the pumps), but combustion wouldn't add much to this, as pressure in the combustion chamber wouldn't be significantly higher. Amateurs build 'pressure water rockets' (search in YT) that would work in a vacuum, as a liquid would transmit a force to the rocket's body, but of course you cannot store the needed energy in that way.