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Author Topic: thrust does not work in space  (Read 58604 times)

Offline PmbPhy

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Re: thrust does not work in space
« Reply #200 on: 31/01/2015 23:12:27 »
There seems little point in discussing this further with SuS until he has answered my question: at what point, during its ascent through the atmopsphere, has he observed the efficiency of a rocket to decrease?

Science is begins with data, not conjecture or analogy, and this is a science forum.
He seems to refuse to answer any question which so obviously proves him wrong. For example: how did all the communications satellites get into orbit.

Lately he's been trying to confuse the issue by using the fact that a perfect vacuum doesn't exist. He doesn't really grasp how small the pressure is even 200 miles above the surface of the Earth. For all practical purposes, especially this one, it can be assumed that the pressure is exactly zero.
 

Offline dlorde

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Re: thrust does not work in space
« Reply #201 on: 01/02/2015 12:24:00 »
SteinUntStein seems to be one of a growing number of 'skeptics' who don't understand the application of Newton's Laws in certain situations. For example, this painful thread on CluesForum. There seems to be an associated conspiracy theory about NASA...
 

Offline PmbPhy

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Re: thrust does not work in space
« Reply #202 on: 01/02/2015 16:03:05 »
SteinUntStein seems to be one of a growing number of 'skeptics' who don't understand the application of Newton's Laws in certain situations. For example, this painful thread on CluesForum. There seems to be an associated conspiracy theory about NASA...
That thread is absolutely horrible. Sometimes I think that talking about physics should be banned by those who don't know what they're talking about. Lol!

It's as if none of these crackpots have ever follow the derivation of the rocket equation or when they try they say incredible stupid things. Like in that thread they say
Quote
The problem with applying Newton’s 3rd is that the rocket’s propellant does not generate force in a vacuum according to the laws of physics and chemistry. If the force of the propellant is 0 then Newton’s 3rd states that
Force on Rocket=-Force of Gas.
If Force of Gas = 0 the rocket does not move.
This crackpot doesn't understand anything and its evident in his statement The problem with applying Newton’s 3rd is that the rocket’s propellant does not generate force in a vacuum according to the laws of physics and chemistry. which is total rubbish. He's making a ridiculous claim with no attempt at backing it up. The chemicals detonate, some go out the back and some hit the nose end of the combustion chamber. The waste products of the explosion bounce off the chamber wall and by Newton's third law the chamber wall recoils taking the rocket with it. It's as simple as that and they simply can't grasp it. Yet they can't even get to the first point where the propellant generates a force on the chamber wall. Oh puleeeeseee!!!


Here's another nut in that thread
Quote
Short answer: Yes a gun recoils in space. No, the analogy does not apply to rockets.


Longer version: Shooting a gun in space would happen theoretically as follows: pressurized gas accelerates the bullet through the barrel until the bullet leaves the muzzle. At that point the gas that was pushing the bullet escapes without doing any more work i.e. via free expansion. The energy of the bullet (its momentum) travels with the bullet and the gun recoils by principle of conservation of momentum.

The gun analogy does not apply to a NASA-type space rocket as their pressurized gas escapes without doing any work at all. A NASA rocket is a gun without a bullet.
This nut can't figure out his mistake. What he did wrong was to ignore that its the recoil itself that makes the rocket accelerate and its the gas that is the bullet. Sort of like shotgun shot. Reading this nonsense makes me real angry because it leads people to make mistakes and never recover from them so the live in ignorance and it hurts them somehow or another.

Either these crackpots never ask themselves why all the physicists that have existed on the planet since the rockets was invented know this and they don't or they think they're smarter than the rest of the planet. That's arrogance in the extreme.

The derivation under MITs website is at
http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node103.html

Want to know what really pisses me off about all of this? It's the fact that experimentation and observation dictate that rockets work exactly like we're (e.g. NASA, MIT etc) state that it does.
« Last Edit: 01/02/2015 16:20:15 by PmbPhy »
 

Offline CliffordK

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Re: thrust does not work in space
« Reply #203 on: 01/02/2015 19:53:21 »
Too much

I'm closing this thread.
 

The Naked Scientists Forum

Re: thrust does not work in space
« Reply #203 on: 01/02/2015 19:53:21 »

 

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