Space Flight

Quote from: icanbeanything on June 05, 2013, 09:14:31 AM

I wrote a lot about pressure differential to him a few pages back, but I never got a response regarding it. I assume he just disregarded it, if he even read it. You just can't trust a scientist...

Oh, scientists can be trusted , just not trusted to always tell it how it should be, which may or may not be their fault, as my placebo post illustrates.

You see, it's not only students than can be duped...those that teach them were once students who were taught what they, themselves were taught and so on  and so on.

1. I'm never going to see a rocket go into space.
2. Rockets do not work in a vacuum.

How is it duping when I'm doing my own experiment with propulsion in a vacuum? It's right in front of me, I'm doing everything. And you can, too:

Quote from: sceptimatic

So what are you doing exactly that proves rockets work in a vacuum. Just explain it to me.

One example would be measuring the thrust generated by a special laser, testing for laser propulsion. Experiment done in a vacuum. You turn on the laser, the beam comes out one end, and it pushes the device the other way, with a very small force that I had to measure.

Quote from: markjo on June 05, 2013, 09:10:02 AM

I know that I'll probably regret this, but here goes.

Sceptimatic, I think understand your objection to rockets working in a vacuum.  You claim that the vacuum of space will suck out all of the rocket's exhaust gasses before they can do any work.  Well, that's true, up to a point.  Here is a simple experiment that you can try at home. 

Let's look at a typical kitchen funnel.  It has a wide end where stuff goes in and a skinny end where stuff comes out, right?  Well, let us take that funnel to the kitchen sink and start pouring water into the funnel.  If we start the water slowly, you will notice that it drains out of the skinny end just as fast as it pours into the big end.  This is just like the vacuum of space sucking the exhaust gasses out of a rocket engine that is only burning a little bit of fuel and oxidizer at a time. 

Now let us turn up the water at the sink. You will notice that after a certain point, the water going into the big end faster than the water can come out of the skinny end.  In the same way, if you burn enough fuel and oxidizer fast enough, the exhaust gasses build up in the rocket's combustion chamber faster than the vacuum of space can suck them out of the little hole in the combustion chamber. 

Basically, it all comes down to pressure.  In the same way that pressure can build up in a funnel or a water hose with a nozzle, gas pressure can build up in a rocket engine's combustion chamber. 

I realize that this is probably a waste of time, but I am an eternal optimist and hold out some faint hope that this funnel analogy will help you understand rockets a little better.

With all due respect Marko, you have your fuel backside first...can you see what I mean?

Also, ponder this.
The fuel in the combustion chamber has no time to expand, because for it to combust, it must have an outlet.... you know, just like a car engine, where fuel is sprayed into the piston area and ignites, pushing the piston down, aided by air coming into it, which is a key point here, because the minute...or should I say the millisecond that fuel and air exposes itself to the vacuum, that's it, game over.

If you don;t mind can you draw me a little diagram of what you actually did with this laser as I am seriously stuck here with this. Basically I cannot picture what you mean.

the minute...or should I say the millisecond that fuel and air exposes itself to the vacuum, that's it, game over.

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There you go,  rocket engine in a vacuum.

Quote from: DuckDodgers on June 05, 2013, 10:32:24 AM

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There you go,  rocket engine in a vacuum.

Posted just that a few pages back... he didn't believe there was a vacuum there.

Quote from: DuckDodgers on June 05, 2013, 10:32:24 AM

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There you go,  rocket engine in a vacuum.

Posted just that a few pages back... he didn't believe there was a vacuum there.

Quote from: icanbeanything on June 05, 2013, 10:57:39 AM

Quote from: DuckDodgers on June 05, 2013, 10:32:24 AM

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There you go,  rocket engine in a vacuum.

Posted just that a few pages back... he didn't believe there was a vacuum there.

Of course not, that would be a disaster for him.  Notice how anyone who explains that they have first hand experience countermanding what he describes is either a liar, or he forgets that they have spoken. Its astounding.

I can't re-convert to a pack of lies, can I.
Flat earth is the way forward and it's you and others that need to re-evaluate to be fair.

Quote from: icanbeanything on June 05, 2013, 12:00:09 PM

Scepti, it's just a laser. You turn on the laser, and because light is coming out one end, it's pushing the laser the other end. This happens in every laser, it's just that it's a very very very weak effect.

I used a pretty powerful laser in a vacuum chamber so I could measure the force it pushed with.

My eye rolling was for your feeble attempt at trying to prove a rocket works in a vacuum with a bloody laser man.lol

Quote from: markjo on June 05, 2013, 10:14:18 AM

Quote from: sceptimatic on June 05, 2013, 09:22:00 AM

Quote from: markjo on June 05, 2013, 09:10:02 AM

I know that I'll probably regret this, but here goes.

Sceptimatic, I think understand your objection to rockets working in a vacuum.  You claim that the vacuum of space will suck out all of the rocket's exhaust gasses before they can do any work.  Well, that's true, up to a point.  Here is a simple experiment that you can try at home. 

Let's look at a typical kitchen funnel.  It has a wide end where stuff goes in and a skinny end where stuff comes out, right?  Well, let us take that funnel to the kitchen sink and start pouring water into the funnel.  If we start the water slowly, you will notice that it drains out of the skinny end just as fast as it pours into the big end.  This is just like the vacuum of space sucking the exhaust gasses out of a rocket engine that is only burning a little bit of fuel and oxidizer at a time. 

Now let us turn up the water at the sink. You will notice that after a certain point, the water going into the big end faster than the water can come out of the skinny end.  In the same way, if you burn enough fuel and oxidizer fast enough, the exhaust gasses build up in the rocket's combustion chamber faster than the vacuum of space can suck them out of the little hole in the combustion chamber. 

Basically, it all comes down to pressure.  In the same way that pressure can build up in a funnel or a water hose with a nozzle, gas pressure can build up in a rocket engine's combustion chamber. 

I realize that this is probably a waste of time, but I am an eternal optimist and hold out some faint hope that this funnel analogy will help you understand rockets a little better.

With all due respect Marko, you have your fuel backside first...can you see what I mean?

No, I don't.  Please explain.  Also, please understand that there is a difference between fuel and exhaust gasses.  The fuel doesn't do the work, the expanding gasses created when the fuel burns does the work.

Yes. They expand into the atmosphere.

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Also, ponder this.
The fuel in the combustion chamber has no time to expand, because for it to combust, it must have an outlet.... you know, just like a car engine, where fuel is sprayed into the piston area and ignites, pushing the piston down, aided by air coming into it, which is a key point here, because the minute...or should I say the millisecond that fuel and air exposes itself to the vacuum, that's it, game over.

Okay, so you don't understand how internal combustion engines work either.  Got it.

Misconstruing what I said, I see. I know it's a closed unit on combustion but it takes "air" and "fuel" into it , is what I meant.

Quote from: mathsman on June 05, 2013, 07:22:27 AM

Quote from: Manarq on June 05, 2013, 07:06:10 AM

You may also want to read http://en.wikipedia.org/wiki/Rocket_engine

And you might want to read the opening few sentences fron the wikipedia entry on the Tsiolkovsky rocket equation:

'The Tsiolkovsky rocket equation, or ideal rocket equation, describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself (a thrust) by expelling part of its mass with high speed and move due to the conservation of momentum. '

My emphasis.

1: I had just about got Sceptimatic to accept that expanding gases in a vacuum can create motion, thanks for derailing that.
2: By all means why don't you explain how gases coming out of the back of a rocket can create motion in the opposite direction without exerting any force on the rocket.

Quote from: Manarq on June 05, 2013, 08:36:27 AM

Quote from: mathsman on June 05, 2013, 07:22:27 AM

Quote from: Manarq on June 05, 2013, 07:06:10 AM

You may also want to read http://en.wikipedia.org/wiki/Rocket_engine

And you might want to read the opening few sentences fron the wikipedia entry on the Tsiolkovsky rocket equation:

'The Tsiolkovsky rocket equation, or ideal rocket equation, describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself (a thrust) by expelling part of its mass with high speed and move due to the conservation of momentum. '

My emphasis.

1: I had just about got Sceptimatic to accept that expanding gases in a vacuum can create motion, thanks for derailing that.
2: By all means why don't you explain how gases coming out of the back of a rocket can create motion in the opposite direction without exerting any force on the rocket.

How difficult is it to understand conservation of momentum? The gases expelled have a certain mass and are expelled at high speed. This means they have a momentum. The rocket and its remaining fuel also have a mass and must move at a speed in the opposite direction so that they have a momentum equal in magnitude but opposite in direction and therefore opposite in sign to the momentum of the gases. This maintains the total momentum of the system.
Mass of gases x speed of gases = mass of rocket x speed of rocket. This is how rockets work in a vacuum.
By all means don't bother to learn about conservation of momentum.

Quote from: Scintific Method on June 05, 2013, 06:44:16 AM

Quote from: sceptimatic on June 05, 2013, 06:33:40 AM

Quote from: Scintific Method on June 05, 2013, 06:24:23 AM

Something else: try stepping off a small boat onto a jetty without mooring the boat or holding onto anything. Typically, the boat will be pushed out from under you and you will fall into the water. Why is this? Going by your logic, the water, being denser than air, should provide more resistance to the movement of the boat than the air does to the movement of your body, so the boat should stay put while you step onto the dock. Why doesn't it?

stepping off a boat onto a jetty will only push the boat away once you create a force which comes from your imbalance, meaning one foot is on the boat and the other is about to hit the jetty, meaning you are leaning forward so naturally you kick your foot back against the boat, it's just action/reaction, so what.

What's this got to do with rockets working in a vacuum?

Action/reaction, Newton's 3rd law, which is one way to explain how rockets work. Picture the rocket as the boat, and the person stepping off as the exhaust gasses. The person moves one direction, the boat moves the other; the exhaust gasses move one direction, the rocket moves the other. Do you get it yet?

Wait just one cotton picking minute here.

You are explaining, now, how rockets actually do work...why have you changed your mind?

A rocket burns it's fuel...that's all it does and that burned fuel is pushed against the atmosphere, expanded into it and the atmosphere fights back. It's as simple as that.

Here is someone else who seems to have thought the whole "rockets can't work in a vacuum" through a little better than Sceptimatic.  He's still wrong, but at least he tries to give specific reasons.
http://cluesforum.info/viewtopic.php?f=23&t=1632&sid=859ccbe6e2bec4c0fa4419addac7bd92

Quote from: mathsman on June 05, 2013, 12:47:04 PM

Quote from: Manarq on June 05, 2013, 08:36:27 AM

Quote from: mathsman on June 05, 2013, 07:22:27 AM

Quote from: Manarq on June 05, 2013, 07:06:10 AM

You may also want to read http://en.wikipedia.org/wiki/Rocket_engine

And you might want to read the opening few sentences fron the wikipedia entry on the Tsiolkovsky rocket equation:

'The Tsiolkovsky rocket equation, or ideal rocket equation, describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself (a thrust) by expelling part of its mass with high speed and move due to the conservation of momentum. '

My emphasis.

1: I had just about got Sceptimatic to accept that expanding gases in a vacuum can create motion, thanks for derailing that.
2: By all means why don't you explain how gases coming out of the back of a rocket can create motion in the opposite direction without exerting any force on the rocket.

How difficult is it to understand conservation of momentum? The gases expelled have a certain mass and are expelled at high speed. This means they have a momentum. The rocket and its remaining fuel also have a mass and must move at a speed in the opposite direction so that they have a momentum equal in magnitude but opposite in direction and therefore opposite in sign to the momentum of the gases. This maintains the total momentum of the system.
Mass of gases x speed of gases = mass of rocket x speed of rocket. This is how rockets work in a vacuum.
By all means don't bother to learn about conservation of momentum.

How does a rocket force the gases out at high speed?

http://exploration.grc.nasa.gov/education/rocket/TRCRocket/rocket_principles.html

Now because a rocket burns fuel with massive force that creates huge thrust..this is where the wide rocket nozzle comes in to move it's mass...because that rocket nozzle allows the burning gases to expand into a wide atmospheric area, meaning the atmosphere must create an equal force to push back against it, so basically your rocket is pushed up by the gases fighting against each other.

So now you know why rockets need atmosphere, you should have no problem understanding that rockets in space is an impossibility.

Next time you're in your garden with the garden hose , you will be watering the garden and seeing a stream of water just coming out of the end of the hose.
No problem right?
Well that water coming out of the hose, is your rocket and fuel. The hose is your rocket and the water is the fuel coming out of your rocket.
We need to make that hose move though, so what can we do?
Well because the water is only coming out in a steady stream, it has little thrust so we need to create a barrier to make that hose move.

This would be worth setting up as an experiment, arranging the hose so that thrust with and without a hand in the way of the flow of water could be compared. Seeing as you brought it up, how would you like to do the experiment and let us know what you find?

Quote from: icanbeanything on June 06, 2013, 04:38:19 AM

Quote from: Scintific Method on June 06, 2013, 04:25:33 AM

This would be worth setting up as an experiment, arranging the hose so that thrust with and without a hand in the way of the flow of water could be compared. Seeing as you brought it up, how would you like to do the experiment and let us know what you find?

It's easy enough, but you're asking Scepti to do an experiment...

I've done it and so have you and most others, so what's difficult about it.

Think of riot police shooting a water cannon at a person.
The water cannon is the rocket and the water is the fuel and the rioter is the atmosphere.
The water gets aimed at the rioter but he won't back down and tries to stay upright and push against the water coming from the cannon right?

Now imagine that the police say, ok lads we need more thrust to knock this man back, so they turn up the water pressure...but as they do so, they are now met with the rioters accomplice, who stands behind him, so they turn up the pressure again, only to see another accomplice behind the second man and so on and so on and it becomes a fight until someone gives up, which would be the police as they run out of water.

Can you see how the atmosphere works against the rockets gases now?

Quote from: Scintific Method on June 06, 2013, 04:25:33 AM

Quote from: sceptimatic on June 06, 2013, 03:01:32 AM

Next time you're in your garden with the garden hose , you will be watering the garden and seeing a stream of water just coming out of the end of the hose.
No problem right?
Well that water coming out of the hose, is your rocket and fuel. The hose is your rocket and the water is the fuel coming out of your rocket.
We need to make that hose move though, so what can we do?
Well because the water is only coming out in a steady stream, it has little thrust so we need to create a barrier to make that hose move.
[/quote

Whoa buddy, hang on there! You go on to say that putting your hand in front of the hose will increase the force pushing it back, but have you actually tried this?

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I would imagine everyone who's used a hose has tried this but it will have had no meaning to just about all of them.

I know that turning up the flow will definitely increase the thrust, but I have never experienced an increase in thrust by putting my hand in front of the nozzle.

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I never implied you were. I stated that your hand is a barrier and the closer you put your hand to the hose water coming out of the hose, then at some stage, the closer your hand gets, it will create a more stronger barrier against the water coming out and eventually creating a force against that water, so it creates a small force on your hand and also on the water, in which case, the hose is forced back the closer your hand gets. go and try it...I have.

This would be worth setting up as an experiment, arranging the hose so that thrust with and without a hand in the way of the flow of water could be compared. Seeing as you brought it up, how would you like to do the experiment and let us know what you find?

Yeah, I still get a far more noticeable increase in thrust by turning up the pressure. To feel an increase by putting my hand in the way, I have to almost block the hose off with that hand to feel any difference.