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How do they stop a space shuttle in space??

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posted on Aug, 14 2008 @ 04:16 PM
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If there is no air in space, how do they use rockets to position the space shuttle?

I was reading the post "If there is no air in space, how do they use rockets to position the space shuttle?" and this question struck me.

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.

So how do they stop the space shuttle???

Ive never saw any opposing thrusters on a shuttle and even if there are then what do they oppose as they are not pushing on anything other than a vacuum?

I dont know if im just being stupid here but i could'nt find an answer from search engines.





posted on Aug, 14 2008 @ 04:19 PM
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Good question, don't know the answer


[edit on 14-8-2008 by milkyway]



posted on Aug, 14 2008 @ 04:24 PM
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reply to post by milkyway
 


when do they stop? Reverse thrusters come to mind, but im not the rocket scientist, just the tax payer.



posted on Aug, 14 2008 @ 04:36 PM
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reply to post by XXXN3O
 


The shuttle doesn't stop while it's in orbit. What makes you think it does?

And yes, it does have thrusters for orbital maneuvering. It uses those thrusters to dock with the ISS which is also in orbit and also not stopped.
In order to leave orbit and return to earth it uses the Orbital Maneuvering System (thrusters) to slow down but it never stops.

I'm not going to get involved the the "nothing to push against" discussion. You couldn't find the answer with search engines? You must be a real whiz.
www.google.com...

Why do I feel like a fat trout?



posted on Aug, 14 2008 @ 04:42 PM
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reply to post by XXXN3O
 


Here ya go!!! You ask, answers will flood in!!!

I've already exlained the LAUNCH system....uses liquid Oxygen and liquid Hydrogen, plus two SRBs....to get off the ground, and achieve orbit.

Onboard, are hypergolic liquids, that when combined, react...and when directed to the exhaust, provide thrust.

The RCS can orient the Shuttle, while on orbit....the OMS engines then burn, slowing her orbital velocity....then, re-orient belly down, for re-entry....gravity and friction do the rest.

I tried to keep it simple....but, Wiki might explain in more detail....or NASA....

edit for spelling

[edit on 8/14/0808 by weedwhacker]



posted on Aug, 14 2008 @ 04:52 PM
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When it gets too far away due to a mix-up of U.S. to metric conversions, the plug comes out of the wall and somebody gets fired.
Kidding

Reference the above posts for your answer.
An obect in motion tends to remain in motion until it is met by an opposing force.(retro rockets)



posted on Aug, 14 2008 @ 04:54 PM
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First - Proceed with caution. Some info was never used from previous century and its reliability is not to be taken blindly.
Now about vacuum (or almost vacuum) and ability to move:
Newton stated that if you apply force on something it will apply the same force on you. If i hit the wall, the wall will act on me with the same force - aka fist is going to hurt.
So if i am in space, in vacuum, with pocket full of rocks and i start to throw rocks - i will start moving in the opposite direction, accelerating slowly because my mass is much bigger then one of the rock. The same with rocket engine in space - hot gases (and other stuff? not sure) accelerate in one direction and shuttle starts to accelerate in the opposite one.
As for thrusters on the space shuttle -

Upon completion of the OMS-1 thrusting period, the reaction control system can be used to null any residual velocities, if required


science.ksc.nasa.gov...-rcs
I do not pretend to understand tenth of what is written there, but "null" and "velocity" luckily i do.
Also check the picture at
en.wikipedia.org...
You will see this RCS at the front of the shuttle.
By the way, thank you for asking that, never thought about it myself.



posted on Aug, 14 2008 @ 05:07 PM
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Originally posted by XXXN3O
If there is no air in space, how do they use rockets to position the space shuttle?

I was reading the post "If there is no air in space, how do they use rockets to position the space shuttle?" and this question struck me.

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.


You don't think the rocket exhaust is an opposing force?

I thought we just closed a thread on this topic. Several people explained it very well. Why do people think Newtons Laws don't apply in space? In fact they are easier in space to make sense of since there is no aerodynamic drag or surface friction.

What happens if you are floating in space next to a big block half your weight and you push on it? I think most people inuitively know that the block will move one way and you the other. Now imagine something smaller, like say you have a backpack full of hockey pucks. When you throw one, it will move off but the conservation of momentum tells us that we'll also move in the reverse direction, but at a slower speed. Each puck you throw adds slowly to your speed. Or imagine you have a gun and fire it. You'll still have a recoil in space which will give you a push. A rocket engine works in the same way, except that it is expelling gas molecules at a very high velocity in effect producing a recoil effect against you. I don't get why people think the rocket exhaust has to push on air. Air is not needed. It's pushing against the rocket which is what is making the rocket move.

Also look at the formulas for the conservation of momentum. It basically says that your center of mass stays constant relative to your current reference. This is one version of the formula:

m1 X v1 + m2 X v2 = P

Where m is mass and v is velocity and P is momentum.

In the case of a rocket, we'll say that the initial P value is zero, ie no momentum. It can be anything though. The mass of the empty rocket is m1 and the weight of the propellant is m2. The combined mass of the rocket plus propellant is m1 + m2.

P can be anything but the conservation of momentum law tells us that P will not change.

Looking at the formula you can see that if P doesn't change, and v1 does, than v2 has to change as well for P to remain constant. Plugging in some number, lets say

mass of rocket (m1) = 500 KG
mass of fuel (m2) = 300 KG

v1 and v2 are both zero since the mass of the rocket and the mass of the fuel are both together in the rocket. Using the formula, you get

500 X 0 + 300 X 0 = 0

Now ignite the propellant and blast it into space until the fuel as all been expended. Say it left at an average speed of 1000 meters/sec (this is v2), using the formula again:

500 X v1 + 300 X 1000 = 0

P is still is zero since according to the law it remains unchanged.

Solving for v1, we get v1 = -600 meters/sec

This is of couse a bit simplified since not all of the propellant is burned instantly but you get the idea. I'm not sure what else one can say about this.



[edit on 14-8-2008 by ghofer]

[edit on 14-8-2008 by ghofer]



posted on Aug, 14 2008 @ 05:15 PM
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The space shuttle stops in Orbit when it lands on the secret space station. hehehe.



posted on Aug, 14 2008 @ 06:30 PM
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I've seen a lot of people using Newton's Third Law to explain how this works.

I can't see the logic.

Newton's Third Law of motion: For every action there is an equal and opposite reaction.

So according to Newton's Third Law, an astronaut taking a space walk in his suit could move through space by flapping his arms, especially if he kicks his legs at the same time.

Maybe if he farts he goes a bit faster, because of the opposite forces pushing on his anus?

This is correct, according to Newton's Third Law, is it not?

Maybe this is all very logical to most of you, but I just can't get my head around it.



posted on Aug, 14 2008 @ 06:44 PM
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Originally posted by enigmania
I've seen a lot of people using Newton's Third Law to explain how this works.

I can't see the logic.

Newton's Third Law of motion: For every action there is an equal and opposite reaction.

So according to Newton's Third Law, an astronaut taking a space walk in his suit could move through space by flapping his arms, especially if he kicks his legs at the same time.

This is correct, according to Newton's Third Law, is it not?


No, that's not correct. In your example, there is no mass being pushed away from you. The mass of the astronaut and therefore is velocity won't change, unless he rips his arms off and throws those away from him. Read my previous explanation again. You need to send mass in the opposite direction you want to travel. You could carry a big block and push that away from you. You'll go one way and the block will go another. With a rocket motor, you are sending gas molecules (which have mass) at a very high velocity away from you, pushing you in the opposite direction.

I think people maybe are thinking about helicopters where they push air away from you. The mass of air is all around you on the earth so you can push against it for propulsion. In space you need to provide your own mass to push out a rocket nozzle.

[edit on 14-8-2008 by ghofer]



posted on Aug, 14 2008 @ 06:44 PM
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Originally posted by enigmania
I've seen a lot of people using Newton's Third Law to explain how this works.

I can't see the logic.

Newton's Third Law of motion: For every action there is an equal and opposite reaction.

So according to Newton's Third Law, an astronaut taking a space walk in his suit could move through space by flapping his arms, especially if he kicks his legs at the same time.

Maybe if he farts he goes a bit faster, because of the opposite forces pushing on his anus?

This is correct, according to Newton's Third Law, is it not?

Maybe this is all very logical to most of you, but I just can't get my head around it.







Okay, the fart part is correct.

Anyway, flapping your arms won't work because there got to be a separation of masses.

This reminds me of a bonus question on a state competition math test I took in high school.

The question is:

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



posted on Aug, 14 2008 @ 06:59 PM
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From WIKIPEDIA:

Third law
Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence "Every action has an equal and opposite reaction."


So, if the gas from the thruster represents particle A, what represents particle B?



posted on Aug, 14 2008 @ 07:01 PM
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Originally posted by enigmania
From WIKIPEDIA:

Third law
Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence "Every action has an equal and opposite reaction."


So, if the gas from the thruster represents particle A, what represents particle B?



That's easy. B is space shuttle. A and B separate so both move in opposite direction.



posted on Aug, 14 2008 @ 07:13 PM
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Jeah but how does gas exert a force to the shuttle if it is essentially sucked out into a vacuum.

I just can't understand how this force is transferred to movement, since it doesn't take any force to push out gas into a vacuum.



posted on Aug, 14 2008 @ 07:14 PM
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Oh geebus, can't we just leave some things to be magic?


The thing doesn't 'stop', it flies around earth at 20, 000Km and hour or whatever around the planet, doing a full orbit every 90 or so minutes (I think).

They use a 'de-orbit' burn to get it down - they flip the shuttle upside-down, fire its rockets, and the earth's atmosphere and gravity in fact does the rest.

The shuttle doesn't 'stop' until it's on the runway. Simple.



You might have to click on the image to get the full thing.

Despite the rumors, god doesn't use his gentle mighty arm to slow the shuttle.

Rockets work in a vacuum because of the velocity of its own propellant leaving the nozzle, pushing against itself.

www.straightdope.com...

[edit on 14-8-2008 by mattguy404]



posted on Aug, 14 2008 @ 07:16 PM
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reply to post by enigmania
 


Okay try this experiment: Get two chairs with wheels. Get your friend to sit with you. Then push each other.

What happens?



posted on Aug, 14 2008 @ 07:25 PM
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Yes, but that is under atmospheric and 1G conditions. It's not the same conditions.

So does this Third Law operate outside of gravity and pressure?

Isn't the movement created in your example the result of the force of two bodies of mass exposed to Earth's gravity?

What about weightlesness in space?



posted on Aug, 14 2008 @ 07:37 PM
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REPLY TO Mattguy.

Jeah but let's say they have to rotate the shuttle around it's axis, to dock, for instance, during orbit.

They would fire the thrusters for that. But since space is a vacuum without friction, how do they make it stop spinning, without constantly adjusting thrusters?

Wouldn't it keep spinning in the opposite direction of the last fired thruster?

[edit on 14/8/08 by enigmania]



posted on Aug, 14 2008 @ 07:42 PM
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Space breaks?

Seriously, you don't want to stop the space shuttle, it will fall back to earth rather quickly.




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