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How do they stop a space shuttle in space??

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posted on Aug, 15 2008 @ 05:56 AM
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Originally posted by weedwhacker
reply to post by Valhall
 


Thanks, Valhall....one point

About the 'constantly falling' bit....that may confuse some folk.

Maybe your wording will invite a misconception?

ANYTHING in orbit, is constantly 'falling'....as I've mentioned.



Good point! Yes, anything in orbit is constantly pseudo-falling, but not really falling. It's the equivalent of "topping the hill". An object in orbit is constantly "topping the hill". If the Earth's surface was perfect - like a big cueball - and you drove in a straight-line at the equator you would be constantly "topping the hill" of the sphere, but not falling...same thing happens in a given orbit. It's angular motion.

My comment on constantly falling was referring to true vertical falling relative to the center of the Earth due to a decrease in orbital speed caused by drag. So, to maintain a given orbit you must maintain the orbital velocity. Drag causes decelaration, which results in a slower orbital velocity, which causes the orbiting object to sink to a lower orbit that has that orbital velocity, and so on and so forth.

That is what I was referring to.




posted on Aug, 15 2008 @ 07:09 AM
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reply to post by weedwhacker
 


Jeah, don't talk down to me, I'm not stupid you know! It's just that I never really studied exact sciences and physics.

But thanks for your responses anyways.



posted on Aug, 15 2008 @ 07:26 AM
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reply to post by enigmania
 


True , I mean if the rocket is blowing out the gases then the rocket is exerting some force to the gases (ACTION) and then the rockect experiments by the gases blowed away by itself a force in the other way (REACTION), moving it . Then it will make some sense to me , but...

But the thing is that seems that the rocket is not blowing out the gases but they are moving alone by the effect of their own combustion , so if the rockect itself is not causing any acction , how could it experiment a reacction?

Morelike seems to me like the action is made by the gases , by their combustion and controled defraglation inside the rocket, pushing the up of the nozzle and the fact that at the bottom of the nozzle is open it origins a net force that is the ACTION and the cause of movement at the same time , the REACTION will be the up of the nozzle pushing against the gases that had pushed it , making the gases to move out of the nozzle apart from the part of the gases that go outside the rokect by their own explotion.

If i am true , i think we was viewing it in the wrong point of view , thinking that what it starts all is the rocket , when maybe it is not , maybe it is the gases .

Sorry for my english , i'm 17 years all and i started english lessons 3 years ago only , i understand people get tired explaining the same time by time , and i don´t want be a troll , it is just that i really find it interesting and none of the explanations fit in my mind at all , pls post your thoughs . Thx in advance .

Milo



posted on Aug, 15 2008 @ 07:44 AM
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Originally posted by XXXN3O
So if they can get the rocket to move which hasnt fully been explained yet. The laws of physics in space dictate that an object will continue forever as there is no opposing force to balance it out and stop it.


It was explained rather fully in the other thread, just go and read about newtonian physics and try to imagine it in a vacuum. It's about direction of force not air pressure.



posted on Aug, 15 2008 @ 07:48 AM
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Is it sunday?

3 pages.. it takes 1 reply. Damn guys..

Maybe its just me, but, an abvvious carry on from the closed thread is really sad.




posted on Aug, 15 2008 @ 09:02 AM
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Originally posted by Anonymous ATS

Sorry for my english , i'm 17 years all and i started english lessons 3 years ago only , i understand people get tired explaining the same time by time , and i don´t want be a troll , it is just that i really find it interesting and none of the explanations fit in my mind at all , pls post your thoughs . Thx in advance .

Milo



Hi Milo! I think you're doing great. Let's discuss what happens in the thruster when it fires. We mix two volatile chemicals (oxidizer and fuel) and when they meet each other they cause an explosion. The thruster is nothing but a controlled explosion chamber. So the explosion takes place and there is this huge pressure wave that only has one exit - the thruster nozzle - to escape from. Now, picture if you will that opposite the escape nozzle is the body of the chamber (or you could think of it as "the rest of the shuttle"). On this side of the thruster combustion chamber there will be a force as the pressure wave attempts to expand but hits the chamber wall.

Does that make sense for you? If not, please don't hesitate to say so because I'm not tired of talking about it. And I would suggest if there are folks on this thread who are tired of talking about it they are cordially invited to find another thread on another topic.



posted on Aug, 15 2008 @ 09:37 AM
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Originally posted by Deaf Alien

The question is:

If you suddenly find yourself on a frictionless ice lake, how will you get yourself off?


Warm mittens & astroglide....

Sorry couldn't resist



posted on Aug, 15 2008 @ 10:27 AM
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The thrusters can be used to invert the shuttle then it can engage its main engines to fire in the opposite direction of motion i.e. it flips round while still travelling and fires pushing in the opposite direction.


Thebudweiserstuntman



posted on Aug, 15 2008 @ 12:26 PM
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Originally posted by bloodcircle
Is it sunday?

3 pages.. it takes 1 reply. Damn guys..

Maybe its just me, but, an abvvious carry on from the closed thread is really sad.



Jeah, jeah and that one reply is: Newton's Third Law; "Every action has an equal and opposite reaction.", I know!

Just because it is given a name and description, doesn't make me understand it more.

Maybe you could help and explain to me in detail why "Every action has an equal and opposite reaction."

If you think it is sad for people to be inquisitive about things they admit they don't understand, well, you are one sad cat yourself.



posted on Aug, 15 2008 @ 12:31 PM
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reply to post by Anonymous ATS
 


Hi Milo, I know what you mean, I just can't seem to grasp how this works, I understand the explanations, but somehow it doesn't make sense to me.

I think your English is pretty good and I know it can be kindoff hard to find the right words sometimes, I'm not typing in my native language either.

You'll see that the more you do it, the easier it get's.



posted on Aug, 15 2008 @ 12:44 PM
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reply to post by Valhall
 





On this side of the thruster combustion chamber there will be a force as the pressure wave attempts to expand but hits the chamber wall.


You are talking about a rocket engine, my main point are the gas thrusters on a space shuttle.

There is no explosion there, just the release of a gas into a vacuum. You could say the gas is sucked out.

There is no pressure wave from an explosion pushing against a chamber wall.

Also, if you release pressurised gas from a container into a vacuum, doesn't all the gas inside get sucked towards the opening?

Wouldn't it actually push against the bottom of the container, where the opening is?

I'm just asking these questions to help my thought process, I'm not trying discard the Laws of Physics here.



posted on Aug, 15 2008 @ 01:32 PM
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Oh no, another "no air in space thread"


There is air in space, it's called rocket exhaust!


please no more of these!



posted on Aug, 15 2008 @ 03:24 PM
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This has been explained fully, but here you go in detail.

The fuel carried on space shuttles is a mix of an oxidizer (so there is no need for oxygen for ignition) and a fuel. The mixture is lit right behind the nozzle of the engine and the ignition pushes the exhaust backwards and the ship forwards. That's how it happens, with no question of doubt, absolutely.

Now how does it stop? The space shuttles have nozzles pointing in all directions, so to steer left, they fire a nozzle on the left side of the ship, to stop, they fire a nozzle on the nose of the ship.

There you go.



posted on Aug, 15 2008 @ 03:42 PM
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Sigh. This again. This is mostly fourth grade stuff, people.

First: nothing gets "sucked" into a vacuum. A vacuum is (ideally) simply a space void of gas, etc. Since the pressure in a vacuum is lower than the pressure in anything with gas in it, gas is PUSHED out into the vacuum. no pulling or sucking occurs.

The gas pushes off of other gas molecules, which push against the walls of their container. That's how pressure works. If there's a pressure difference, gas is pushed in the direction of lower pressure.

Rockets work by conservation of momentum. Imagine if you will, being in space, floating next to another person of the same mass as yourself. If either of you pushes the other away, you'll both move away from the starting point at the same rate. Applying a force to anything applies a force to yourself. Accelerating anything, be it a person, block, or gas, will accelerate you. in space, the only way of changing velocity is to change the velocity of something else (even if it's just particles of the solar wind, or even photons). This is typically done by accelerating some propellant, usually combusted rocket fuel (but propellant doesn't have to be fuel, like in an ion drive craft.)

Rockets don't push off of the air behind them, neither do jets or propellers. Jets and propellers work by pushing the air in front of them behind them faster than it was going when it was in front of the propeller or jet. Rockets use their own propellant supply and accelerate that behind them.

Now somebody argued that if that were true, that someone could move around by flapping their limbs. I weep for mankind. You can move about a little bit by doing this, but you won't get anywhere, because, since your arms don't come off, you'll have to slow them back down when they reach the limits of their flexibility. which will mean you'll stop moving. then, if you decide to pull your arms back to their starting position, you'll move right back to where you started. you'll never go anywhere by positioning your limbs.

You can, however, change your orientation. This is easier done with a set of reaction gyroscopes, like on the ISS. The gyroscopes have the advantage that they don't have to stop at the limits of their travel, they can spin around forever. Spinning up the gyroscope accelerates the vehicle in the opposite angular direction. then, as long as the gyroscope is spinning relative to the station/vehicle, said contrivance is spinning relative to it's rest position. stopping the gyroscope also stops the rotation of the station, by conservation of angular momentum. This all lets you change your orientation without using any fuel. It's usually pretty slow though, because of engineering limits on how fast you can spin your gyroscopes, and how big they can be made before they're unnecessarily heavy.

The space shuttle doesn't stop. it's constantly falling towards the earth. When it goes to dock with something, it matches it's trajectory around the earth. when it's time to go back down, it fires it's rockets against it's orbital velocity, and falls out of space.

The ISS needs to be periodically boosted because it's in a rather low orbit. there's still enough atmosphere to slow it down over a long period of time. It's still damn near a perfect vacuum, but there's no such animal.



posted on Aug, 15 2008 @ 04:08 PM
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posted on Aug, 15 2008 @ 04:13 PM
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Originally posted by enigmania
reply to post by Valhall
 





On this side of the thruster combustion chamber there will be a force as the pressure wave attempts to expand but hits the chamber wall.


You are talking about a rocket engine, my main point are the gas thrusters on a space shuttle.

There is no explosion there, just the release of a gas into a vacuum. You could say the gas is sucked out.

There is no pressure wave from an explosion pushing against a chamber wall.

Also, if you release pressurised gas from a container into a vacuum, doesn't all the gas inside get sucked towards the opening?

Wouldn't it actually push against the bottom of the container, where the opening is?

I'm just asking these questions to help my thought process, I'm not trying discard the Laws of Physics here.


The expansion of gas in a fuel/oxidizer mix is just like an explosion only the pressure generated is of a different magnitude and velocity. There is, indeed, a pressure wave from the resultant reaction and it will generate omnidirectional. The only place it will have an outlet is at the thruster vent.

The velocity any given jetted flow has is the result of the pressure gradient across the orifice. So there necessarily must be a pressure differential in order for something to "flow" or "jet". That's basically exactly what I said before I stated that if you have two chemicals mix and create a pressure wave (due to explosion/expansion/etc) it will react omnidirectionally and flow/jet in the direction of least resistance (i.e. greatest negative pressure gradient).

If you cannot understand why a balloon will fly around the room if you blow it up without tying it closed and then let go of it, you're probably not ever going to be able to get this concept down. The pressure is acting omnidirectional in the balloon. There is only one path out and this causes a force acting opposite the eflux to push the balloon around the room.



posted on Aug, 15 2008 @ 06:22 PM
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reply to post by Valhall
 


Hi , I am Milo .

First of all , give thank you Valhall and Enigmania for being so nice with me
.

Valhall , i must say that your explanation of the expanding wave of gases pushing (ACTION , not REACTION ) the shuttle/rocket "forward" is the only one that has sense to me and i can see clearer, i believe that it's what actually makes the shuttle/rocket movement , of course maybe we could be wrong ...

But if we are right , then is when i start asking me what the 3rd Newton`s law has to do with the issue :

Let`s analyze it:

1. Combustion of the mix .

2. High presure wave expanding volume all directions inside shuttle/rocket.

3.The rocket is not pushing gases out , the gases itself is running out by finding their path to go out .

4. The wave hits all points of internal walls of shuttle /rocket and exerts pression all direcctions , like a globe .

5.For each point of the internal walls of the shuttle suffering pressure by the wave is other point ( diametral opposite direction ) suffering the same pression , this makes both cancel eachothers making no movement at all .
This applies to all points of the internal wall but the ones opposite direction of the hole of the nozzle where there is not pressure and in the opposite direction there is pressure , making a force result , making pushing the shuttle forwards .

6.The movement is already made , the continous process of combustion-explosion keeps it moving.

-So , i mean of course there is a reacction after the wave hits top internal wall of shuttle , but as far as i think it has nothing to do with the cause of movement , so we just can explain why it moves in the vaccum without using 3rd newton's law , since i think only the ACTION is what makes its movement , the REACTION does not matters , right?

So all people that was saying that it moves because rocket is blowing gases out (afterall if i am right blowing gases out neither is the action or the reaction )and then there is a reaction that moves rocket in opposite direction , are they wrong? , at least i think they are not tehnically right ...

I don´t want seem rude , but saying it moves because newton's 3rd law is as right as saying that if you don´t breath you die , that´s right but that is not explainig it at all .

As always i will appreciate your opinions .

Milo



posted on Aug, 15 2008 @ 08:02 PM
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Dear Milo,

I am glad you signed up. Thank you for your kind words.

You have just talked your way through understanding the 3rd law. It is always this way. If I push against the wall of the swimming pool the normal force that is created on my hand that is equal and opposite to the pushing force my hand creates on the pool wall will propell me backwards. Since the pool is attached to the Earth and the massive inertial forces prevent it from moving, virtually the entire force I exert on the pool wall sends me backward (diminished only by the drag of the water flow over my body).

The same thing happens when the thruster fires only this time the "pool wall" is the shuttle-side surface of the thruster jet orifice/nozzle. As the pressure is exerted on the thruster the shuttle moves because it can't resist the force (like the pool did). Hence movement...and the 3rd law.

For every force there is an equal and opposite force - in this case our shuttle is not anchored to Mother Earth, so it moves.



posted on Aug, 17 2008 @ 03:16 AM
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reply to post by MILO17
 


You're all kinds of confused here in this thread.

Firstly, nothing is "sucked" when it comes to pressure. ever. Vacuums do not suck, the air around them pushes into them. In space, gas is not sucked out of containers that are breeched; the gas pushes out, because of the pressure difference. Language and popular culture have done us a disservice; a tiny brainwashing of sorts. Most people, like you, have it backwards.

If you were to bring a cylinder of air into space, and poke a hole into it, it would thrust opposite the direction of the hole. The gas is forced out of the hole by the rest of the gas, because there's nothing holding it in. This doesn't happen in atmosphere, because there's usually other air holding it in. But if you pressurize a container above ambient pressure, releasing that works just the same. Such as you might do by blowing up a balloon and releasing it.

Your steps are foolish. it goes like this.

1. Rocket changes momentum of some of it's propellant, by accelerating it backwards somehow.

2. Rocket, in turn, is propelled forwards, at a rate determined by the momentum change of that propellant, and the mass of the rocket.

That's it.

Now there's all kinds of ways of doing the first step. In a chemical rocket it goes like this:

a. oxidizer and fuel are pumped into a combustion chamber
b. They are combusted and consequently increase in temperature and pressure
c. that pressure (which, if you didn't know, means the average force with which the molecules in the gas push against each other and the walls of their container) pushes gas molecules out the nozzle.

Rockets actually work better in space, because there's no air behind them to screw things up.




There's nothing magical about a vacuum. it's just got 14.7 psi less than we're used to. That's the difference between here and about 30 feet underwater. It's inhospitable to life, and makes many other things more difficult than we're used to, but everything works just the same in it.


reply to post by rgs55
 


Rockets don't push off against their exhaust the way you think they do. It wouldn't matter if there was no exhaust behind the rocket, it would still thrust just fine. Imagine this if you will. Instead of the rocket firing a constant stream of gas particles, the rocket fires single, discrete particles, like bullets. Much like a gun. The recoil from firing would push it along. Recoil in guns is a direct and simple application of newton's third law. The recoil of a gun is determined by the momentum imparted on the projectile. the momentum imparted on the shooter is exactly the same as that imparted on the projectile. The projectile, naturally, moves much faster, because it is much lighter. but it's change in momentum is the same.

Momentum is defined as mass times velocity, if it needs to be defined here.

Rockets fire innumerable molecules of propellant in a stream, instead of discrete shots, but the principle is the same. By changing the momentum of it's propellant, it achieves thrust in the opposite direction.








Now to the next point: the space shuttle doesn't stop. it orbits the earth. It's moving pretty damn fast until it lands. If it docks with the space station, it's simply matched the orbit of that. it's going fast in the same direction. It does some fine tuning with it's weak little positioning rockets, and lines itself up. It's like one of those movies where a guy on a motorcycle jumps onto a moving car. They're both moving fast, but they're going at a close enough trajectory that they can interact more or less like they're stationary.


If by stop you mean deorbit, the shuttle just burns it's rockets against it's direction of orbit, and is consequently pulled back down towards the planet. It usually operates at a pretty low orbit, so it doesn't take much to get it low enough that atmospheric drag from the top of the atmosphere slows it down more and more until it's back to reasonable speeds, and not on any orbital trajectory.



posted on Aug, 17 2008 @ 11:32 AM
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reply to post by XXXN3O
 

There ARE thrusters pionted at angles to stop the shuttle yes.



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