Space Flight

Quote from: markjo on June 29, 2013, 11:52:24 AM

Quote from: sceptimatic on June 29, 2013, 11:41:19 AM

I need people to work with me with a mind, away from indoctrination and fine tune this, because I genuinely believe I'm on the right track here.

What your really need to do is to ask yourself "what do I believe, what do I know and what can I prove?"  Please note, those are three different questions that will have three different answers.

I believe the earth has an ice dome.
What I know is in my own mind.
I can not prove anything to anyone who isn't prepared to contemplate it.

The beauty of proof is that it is used to show a theory to be correct, whether or not you really want to believe it to be correct.

Quote from: sokarul

So the wall, other walls, floor, and ceiling do nothing?

You didn't mention other walls and a bloody ceiling. What are you playing at?

I said your wall.
Not a stationary wall all by itself that will fall over when pushed.

Quote from: sokarul

Different process. It works with glass too.

What's different about it?

[/quote]
I was referring to fact that when something falls over air tries to escape and is compressed by the falling object.  Air touching a wall is not being compressed by a force.

There is a need for outside force, there has to be for everything on earth. It's always equal and opposite reaction to action. "ALWAYS."

There is an equal and opposite reaction, but it comes from the walls of the container itself, not from any outside force.

 Okay, let's go back over it: everything used to make pressure vessels has a certain tensile strength; a certain amount of strain it can handle before it breaks. My examples were a steel cable lifting a large weight, and a balloon clamped so that weights could be hung from it. In both these examples, there is no opposing force other than that supplied by the cable or balloon; they are solely responsible for carrying the loads placed on them.

 Pressurising a container made of steel, or blowing up a balloon, is not that different to hanging weights off it. You are simply placing the sides of the container under tension in the same way as hanging weights off it. And just like you can only hang so many weights off it before it breaks, you can only pressurise it to a certain point before it bursts. This limit is solely governed by the tensile strength of the container, and has absolutely nothing to do with the outside environment.

You have a basic grasp but you refuse to see the finer points and either can't understand them or you are simply refusing to, because it will wreck your rocket dream or something.

The finer points were details that you made up so that you can try to crush my rocket dreams. Air pressure was a well understood phenomenon before any plane even took off the ground.

Quote from: Puttah on June 29, 2013, 09:39:42 PM

Quote from: sceptimatic on June 29, 2013, 05:03:51 AM

You have a basic grasp but you refuse to see the finer points and either can't understand them or you are simply refusing to, because it will wreck your rocket dream or something.

The finer points were details that you made up so that you can try to crush my rocket dreams. Air pressure was a well understood phenomenon before any plane even took off the ground.

Do you agree that a rocket "must" be at "full" thrust to take off?

No. Since a rocket at full thrust has a significant acceleration upwards, then taking away a bit of that thrust will only take a way a bit of that upwards acceleration. If we took enough thrust away, then there's a point where the force of gravity downwards will equal the thrust upwards and the space ship will manage to hover.

Also, just in case you didn't know, since a rocket's thrusters provide roughly the same force throughout its journey but are continuously burning up fuel, as the mass of the rocket decreases and the force stays constant, the acceleration increases. So not only is the rocket increasing its velocity by acceleration, but the acceleration itself is increasing over time too.

Quote from: Scintific Method on June 29, 2013, 06:52:34 PM

Quote from: sceptimatic on June 29, 2013, 07:50:43 AM

There is a need for outside force, there has to be for everything on earth. It's always equal and opposite reaction to action. "ALWAYS."

There is an equal and opposite reaction, but it comes from the walls of the container itself, not from any outside force.

 Okay, let's go back over it: everything used to make pressure vessels has a certain tensile strength; a certain amount of strain it can handle before it breaks. My examples were a steel cable lifting a large weight, and a balloon clamped so that weights could be hung from it. In both these examples, there is no opposing force other than that supplied by the cable or balloon; they are solely responsible for carrying the loads placed on them.

 Pressurising a container made of steel, or blowing up a balloon, is not that different to hanging weights off it. You are simply placing the sides of the container under tension in the same way as hanging weights off it. And just like you can only hang so many weights off it before it breaks, you can only pressurise it to a certain point before it bursts. This limit is solely governed by the tensile strength of the container, and has absolutely nothing to do with the outside environment.

I've already said the container , obviously holds the compressed air molecules but it's being expanded but cannot be seen.
Air molecules are colder inside than outside due to compression and the more agitated molecules outside are bombarding the vessel, trying to stretch it to equalise the pressure inside of it.
That's the reason why cylinders are so thick.
Surely you must be able to understand now.

Well actually when you compress air, it gets hotter. Equally, when you decompress a gas, it gets colder.
You can easily verify by yourself.
This brings down your explanation.

Quote from: Puttah on June 30, 2013, 05:40:51 AM

Quote from: sceptimatic on June 30, 2013, 04:30:52 AM

Quote from: Puttah on June 29, 2013, 09:39:42 PM

Quote from: sceptimatic on June 29, 2013, 05:03:51 AM

You have a basic grasp but you refuse to see the finer points and either can't understand them or you are simply refusing to, because it will wreck your rocket dream or something.

The finer points were details that you made up so that you can try to crush my rocket dreams. Air pressure was a well understood phenomenon before any plane even took off the ground.

Do you agree that a rocket "must" be at "full" thrust to take off?

No. Since a rocket at full thrust has a significant acceleration upwards, then taking away a bit of that thrust will only take a way a bit of that upwards acceleration. If we took enough thrust away, then there's a point where the force of gravity downwards will equal the thrust upwards and the space ship will manage to hover.

Also, just in case you didn't know, since a rocket's thrusters provide roughly the same force throughout its journey but are continuously burning up fuel, as the mass of the rocket decreases and the force stays constant, the acceleration increases. So not only is the rocket increasing its velocity by acceleration, but the acceleration itself is increasing over time too.

So you don't think a rocket needs maximum thrust to take off.
Hmmm.
No wonder you are confused.

I already answered why a rocket doesn't need its maximum thrust to take off, but since you asked, I'll give a little Mathematical proof, so get ready to be bored.

Let the thrust of a rocket be a force F_r and the mass of the rocket be m_r hence the acceleration due to the thrust is F_r/m_r = a_r. Newton's equation F=ma then gives us the force of gravity to be F_g=m_r(-g) since the acceleration is in the opposite direction to the rocket's acceleration due to the thrusters.

The net force on the rocket is then
F_n = F_r-F_g
m_ra_n = m_ra_r-m_rg
a_n = a_r-g

where a_n is the resultant acceleration. This value is positive since the rocket takes off, so then a_r-g is positive and hence as long as the acceleration due to the thrust a_r > g, the resultant acceleration a_n > 0 and the rocket will take off.



To think that the rocket is only designed to JUST be able to lift off the ground is ludicrous, and obviously wrong considering we can observe how quickly it lifts off the ground and is gone into the sky.

Quote from: Puttah on June 30, 2013, 06:09:40 AM

Quote from: sceptimatic on June 30, 2013, 05:43:36 AM

Quote from: Puttah on June 30, 2013, 05:40:51 AM

Quote from: sceptimatic on June 30, 2013, 04:30:52 AM

Quote from: Puttah on June 29, 2013, 09:39:42 PM

Quote from: sceptimatic on June 29, 2013, 05:03:51 AM

You have a basic grasp but you refuse to see the finer points and either can't understand them or you are simply refusing to, because it will wreck your rocket dream or something.

The finer points were details that you made up so that you can try to crush my rocket dreams. Air pressure was a well understood phenomenon before any plane even took off the ground.

Do you agree that a rocket "must" be at "full" thrust to take off?

No. Since a rocket at full thrust has a significant acceleration upwards, then taking away a bit of that thrust will only take a way a bit of that upwards acceleration. If we took enough thrust away, then there's a point where the force of gravity downwards will equal the thrust upwards and the space ship will manage to hover.

Also, just in case you didn't know, since a rocket's thrusters provide roughly the same force throughout its journey but are continuously burning up fuel, as the mass of the rocket decreases and the force stays constant, the acceleration increases. So not only is the rocket increasing its velocity by acceleration, but the acceleration itself is increasing over time too.

So you don't think a rocket needs maximum thrust to take off.
Hmmm.
No wonder you are confused.

I already answered why a rocket doesn't need its maximum thrust to take off, but since you asked, I'll give a little Mathematical proof, so get ready to be bored.

Let the thrust of a rocket be a force F_r and the mass of the rocket be m_r hence the acceleration due to the thrust is F_r/m_r = a_r. Newton's equation F=ma then gives us the force of gravity to be F_g=m_r(-g) since the acceleration is in the opposite direction to the rocket's acceleration due to the thrusters.

The net force on the rocket is then
F_n = F_r-F_g
m_ra_n = m_ra_r-m_rg
a_n = a_r-g

where a_n is the resultant acceleration. This value is positive since the rocket takes off, so then a_r-g is positive and hence as long as the acceleration due to the thrust a_r > g, the resultant acceleration a_n > 0 and the rocket will take off.



To think that the rocket is only designed to JUST be able to lift off the ground is ludicrous, and obviously wrong considering we can observe how quickly it lifts off the ground and is gone into the sky.

It needs maximum thrust, to be propelled vertically, there is no other way it can take off.
If there isn't maximum thrust, then it would take off and hover and boom, crash back to the ground.

Have a look at when a plane is at maximum thrust.

Irrelevant, but anyway, you'd be surprised...Commercial planes very often take off with a reduced power setting.

Have a look at when a plane is at maximum thrust.

It might be of interest to you that reduced thrust (ie less than maximum thrust) takeoffs are common practice in aviation.

I've already said the container , obviously holds the compressed air molecules but it's being expanded but cannot be seen.
Air molecules are colder inside than outside due to compression and the more agitated molecules outside are bombarding the vessel, trying to stretch it to equalise the pressure inside of it.
That's the reason why cylinders are so thick.
Surely you must be able to understand now.

The compressed gas is actually hotter when it is first compressed, but cools to ambient temperature eventually. The gas outside the vessel only ever applies as much pressure to the vessel as it does to anything else.
Cylinders are as thick as they need to be to cope with their design pressure. Aerosol cans are quite thin, but still contain gas at quite a high pressure.
All of this is glaringly obvious when approached in an open minded, logical fashion. I am surprised that it is still being discussed after such an awfully long time.

...you will never get any further by burying your head in the sand.

Says he who accepts no point of view other than his own.

It needs maximum thrust, to be propelled vertically, there is no other way it can take off.
If there isn't maximum thrust, then it would take off and hover and boom, crash back to the ground.

Have a look at when a plane is at maximum thrust.

Ok... so some space ship has a certain maximum thrust that lifts it off the ground. The next gen design is the exact same space ship EXCEPT that it has some form of turbo boost switch that gives it extra oomph. So now this space craft's maximum thrust is beyond that of its predecessor. What happens if the thrust of this new design turns off its turbo? Does it crash back down?

Quote from: Scintific Method on June 30, 2013, 06:54:47 AM

Quote from: sceptimatic on June 30, 2013, 06:41:49 AM

...you will never get any further by burying your head in the sand.

Says he who accepts no point of view other than his own.

Not when I'm correct.

lol do you ever think you're wrong on this forum?

Scepti can you finish this equation for me? It relate to the nitrogen gas cylinders at my work.

3000 PSI nitrogen gas = ?

Quote from: Scintific Method on June 30, 2013, 06:35:21 AM

Quote from: sceptimatic on June 30, 2013, 06:19:48 AM

Have a look at when a plane is at maximum thrust.

It might be of interest to you that reduced thrust (ie less than maximum thrust) takeoffs are common practice in aviation.

Quote from: sceptimatic on June 30, 2013, 04:29:59 AM

I've already said the container , obviously holds the compressed air molecules but it's being expanded but cannot be seen.
Air molecules are colder inside than outside due to compression and the more agitated molecules outside are bombarding the vessel, trying to stretch it to equalise the pressure inside of it.
That's the reason why cylinders are so thick.
Surely you must be able to understand now.

The compressed gas is actually hotter when it is first compressed, but cools to ambient temperature eventually. The gas outside the vessel only ever applies as much pressure to the vessel as it does to anything else.
Cylinders are as thick as they need to be to cope with their design pressure. Aerosol cans are quite thin, but still contain gas at quite a high pressure.
All of this is glaringly obvious when approached in an open minded, logical fashion. I am surprised that it is still being discussed after such an awfully long time.

When you understand how it all works, then you will have a clearer view. Until then, I agree, you will never get any further by burying your head in the sand.

You didn't respond directly to my post but this is very close to what we were talking about.

Does the state of air surrounding a container change somehow when the temperature of pressurized container has equalized? According to you it is not possible to see compression of a container's walls, how do you know this is what happens, do you have a method for observing and measuring this invisible compression? Above all what I'd like to know is exactly what agitates the air outside a container to make them compress against it's walls when the container becomes pressurized and how can we observe and measure this newly discovered phenomenon. A direct answer would be very much appreciated, thank you + pretty please. Answers to these questions are vital for arranging an experiment so we all could stop burying our heads in the sand.

Quote from: Puttah on June 30, 2013, 07:34:39 AM

Quote from: sceptimatic on June 30, 2013, 06:19:48 AM

It needs maximum thrust, to be propelled vertically, there is no other way it can take off.
If there isn't maximum thrust, then it would take off and hover and boom, crash back to the ground.

Have a look at when a plane is at maximum thrust.

Ok... so some space ship has a certain maximum thrust that lifts it off the ground. The next gen design is the exact same space ship EXCEPT that it has some form of turbo boost switch that gives it extra oomph. So now this space craft's maximum thrust is beyond that of its predecessor. What happens if the thrust of this new design turns off its turbo? Does it crash back down?

It either starts off on "maximum" thrust to springboard it into the air, or it crashes, it's as simple as that.
Mass to weight ratio has to be equal. If you add a person, you have to add that persons mass of fuel and so on.
There is no way around it with vertical take off.

Scepti,

This is easy to experiment on, I have done it as a child and you can too, and the experiments immediately prove you to be mistaken here. Practically all rocket engines are designed to have more thrust than necessary for liftoff because quick acceleration right off the launch is important for fuel economy. Get yourself a rocket, a 2$ fireworks rocket will do, you certainly can attach a small amount of additional weight to it and it will still lift off the ground, thus, the rocket provided more thrust than necessary for getting off the ground, thus, it would have lifted off with less power, thus you've mistaken about this.

Quote from: sokarul on June 30, 2013, 07:38:13 AM

Scepti can you finish this equation for me? It relate to the nitrogen gas cylinders at my work.

3000 PSI nitrogen gas = ?

Go back to your works and ask them about this.

I thought you understood what you were saying. My mistake.

Quote from: sokarul on June 30, 2013, 08:14:54 AM

Quote from: sceptimatic on June 30, 2013, 07:55:31 AM

Quote from: sokarul on June 30, 2013, 07:38:13 AM

Scepti can you finish this equation for me? It relate to the nitrogen gas cylinders at my work.

3000 PSI nitrogen gas = ?

Go back to your works and ask them about this.

I thought you understood what you were saying. My mistake.

I know exactly what I am saying. You don't.

Then finish the equation.

Quote from: sokarul on June 30, 2013, 08:21:06 AM

Quote from: sceptimatic on June 30, 2013, 08:18:36 AM

Quote from: sokarul on June 30, 2013, 08:14:54 AM

Quote from: sceptimatic on June 30, 2013, 07:55:31 AM

Quote from: sokarul on June 30, 2013, 07:38:13 AM

Scepti can you finish this equation for me? It relate to the nitrogen gas cylinders at my work.

3000 PSI nitrogen gas = ?

Go back to your works and ask them about this.

I thought you understood what you were saying. My mistake.

I know exactly what I am saying. You don't.

Then finish the equation.

What with the equation crap. This won't explain space flight.

Are you talking about standard cubic feet here or what?
250 standard cubic feet.
Come back with any more equations and you will be blanked.

Give up on your stupid ideas. You can't even explain them. You will save us the time of having to call you dumb every 5 minutes.

"oh my boss has a big nitrogen tank with 3000 psi in it, what is it scepti, what is it?"
Go away boy.

Why would my boss have a gas cylinder in his office? It seems to me you forgot I was a chemist.
It as a simple equation. I wanted you to answer what was equal to the pressure in the cylinder. Not hard.

It needs maximum thrust, to be propelled vertically, there is no other way it can take off.
If there isn't maximum thrust, then it would take off and hover and boom, crash back to the ground.

No.  A rocket burns fuel, thereby making itself lighter as time goes by.  This is why many rockets actually reduce thrust while in flight.

Once a rocket is in flight, it's in flight. There is no reducing thrust, it's thrust all the way until it runs out.

Liquid fuel rockets have there fuel pumped in, they could just pump less.
Solid fuel rockets could just make the chamber of fuel narrower.
You are not a rocket scientist. 

It's maximum thrust to take off and spring boarded into the air where it expends its fuel against it's mass/weight.

Maximum thrust would be required. Once the rocket starts moving by default less thrust is needed.

It doesn't get faster, the higher it goes...not vertically.

The rocket already accelerated to move from zero velocity. At what point does it stop accelerating? Rockets usually make thrust in excess so they can accelerate. The space shuttle has to make it to escape velocity.
Going vertical is the same thing as going higher.

A plane can do it but a rocket cannot, unless it arced over, in which case it's weight is not being pushed up, it's pushed down, so it would speed up , only then.

lol
You are still not a rocket scientist.

Quote from: neimoka on June 30, 2013, 07:58:55 AM

Quote from: sceptimatic on June 30, 2013, 07:53:04 AM

Quote from: Puttah on June 30, 2013, 07:34:39 AM

Quote from: sceptimatic on June 30, 2013, 06:19:48 AM

It needs maximum thrust, to be propelled vertically, there is no other way it can take off.
If there isn't maximum thrust, then it would take off and hover and boom, crash back to the ground.

Have a look at when a plane is at maximum thrust.

Ok... so some space ship has a certain maximum thrust that lifts it off the ground. The next gen design is the exact same space ship EXCEPT that it has some form of turbo boost switch that gives it extra oomph. So now this space craft's maximum thrust is beyond that of its predecessor. What happens if the thrust of this new design turns off its turbo? Does it crash back down?

It either starts off on "maximum" thrust to springboard it into the air, or it crashes, it's as simple as that.
Mass to weight ratio has to be equal. If you add a person, you have to add that persons mass of fuel and so on.
There is no way around it with vertical take off.

Scepti,

This is easy to experiment on, I have done it as a child and you can too, and the experiments immediately prove you to be mistaken here. Practically all rocket engines are designed to have more thrust than necessary for liftoff because quick acceleration right off the launch is important for fuel economy. Get yourself a rocket, a 2$ fireworks rocket will do, you certainly can attach a small amount of additional weight to it and it will still lift off the ground, thus, the rocket provided more thrust than necessary for getting off the ground, thus, it would have lifted off with less power, thus you've mistaken about this.

Of course it will lift off of the ground.
I don't think you grasp what I'm saying.
If you attach additional weight, yes it will take off but it wouldn't get very far and would be unstable and crash back to earth.
Until you understand how a rocket really works, you will never contemplate what I'm saying and I'm being serious.

It gets unstable and crashes if the load is poorly balanced. With balanced load, why would it crash? If it has enough fuel to reach target height why wouldn't it get far enough? Earlier you made an explicit blanket statement that rockets can not lift off the ground unless they are running at 100% percent thrust, did you just change your mind about this? You also claim that rockets can not do anything but run at 100% percent thrust untill they run out of fuel, perhaps you aren't aware that liquid fuel rockets capable of exactly that have existed for well over half a century?

You keep making "100% true" statements that contradict both common knowledge and direct observation with absolutely nothing to back them up with. How about answering some of the questions about air pressure outside a pressurized container?

It doesn't get faster, the higher it goes...not vertically.

*facepalm*

So now you don't even understand acceleration, and you're trying to explain rockets to us?

No wonder such a simple equation as F=ma has eluded you for so long.

Mass to weight ratio has to be equal. If you add a person, you have to add that persons mass of fuel and so on.

It would've been awesome if you learnt some basic physics first. The mass to weight ratio? What the fuck?

It would've been awesome if you learnt some basic physics first. The mass to weight ratio? What the fuck?

Also, if the thrust is insufficient for liftoff, adding fuel is supposed to help? :p

Quote from: Puttah on June 30, 2013, 01:16:18 PM

It would've been awesome if you learnt some basic physics first. The mass to weight ratio? What the fuck?

Also, if the thrust is insufficient for liftoff, adding fuel is supposed to help? :p

Apparently, but I don't know if in your example the mass to weight ratio goes up or down

Can you please give your estimation of the maximum velocity reached by a rocket, and the corresponding height ?
For example Saturn V

Not surprised by the answer. 
Please pick another, Semyorka, Ariane,...

Pick a rocket that has existence for you, and go on

Nice turnaroud.
No need for a space one. A firework rocket may be also fine.

Still avoiding the answer.
You have some personal views of how rocket work. Fine enough. Please give some estimate of the reached maximum speed, and the corresponding altitude. Or if you want, give somme idea of the speed increase, if any, when climbing.

Why are you avoding this simple question ?