STS-75 Tether Incident - Mystery solved! Breaking News!

Okay, I found some cool clips that I felt I should introduce to the thread. They are mostly to illustrate objects moving in space, and how these objects change vectors when acted upon by an external force.

I just thought it would be good to have a point of reference, so that we can all cite timestamps when we're talking about how an object moves...

Clip 1, Astronauts goofing around:


Clip 2, Water Boiling in Space:


Clip 3, For levity as well as clarity, check out :13 where the guy flicks the pack of cigarettes. That is a measurable force that we can duplicate.
Also check out the food tossing at the end. There are a lot of experiments we can use hidden in this cheesy video:

Might want to turn your speakers down for this last one...

-WFA

LOL Experiments? So tell me again how we will do these experiments in Space?

Or at the very least a chamber with LEO gravity simulated and no air?

And you have yet to explain what forces are involved in accelerating these 'dust' particles and causing them to change orbit?

Hmmmm

Originally posted by ArMaP
This is a more correct representation of the second drawing.

Maybe this will show better what I am trying to explain. The black arrows show the two velocities affecting the blue ball, one that the ball "inherited" from the shuttle and the other the result of the acceleration created by the applying of a force to the ball to make move away.

Nice pic, i'm really glad that you take the time to do these!
Star as Usual!

In that case the ball would have a slightly smaller velocity than the shuttle, because it would have a negative velocity (in direction, not in value) combined with the positive velocity of the shuttle.

Well that depends on how you wish to see it, will you see momentum as a force?
Or will you see momentum as the result of a force?
It is still the force that gives momentum.

If you do the same with the ball in a direction that is on the same trajectory as the shuttle the result will be that you are adding mometum, but at the same time, since the first force that was used to give the momentum to this ball is nullified, you are only changing the momentum given by the new force.
However, in my example as putting the force from the opposite trajectory as the shuttle to cause momentum in the other direction.
You are nullifying both, force and momentum.

Much of this though has to do with mass of the object, if you equal the force of the mass and apply it from the right direction, the momentum will stop.
If you however have more force put onto the object than mass, the object will continue going the opposite direction.

Now if we go after the water spray from the side of the shuttle angled 90 degrees off the trajectory of the shuttle.
Here some math is in order....
V for velocity, M for mass, F for force.
It will look like something like this v+m/f = ? (i think that is the right way, dont remember) but since we only have one number.....

Then you will have the velocity/momentum the particles will be leaving the shuttle with.
Now, if the force is greater than the speed and mass already on these particles they will only be going 90 degrees out from the shuttle without the effect from the shuttles already imposed momentum on the particles.

Now, dont come and tell me i am wrong about this, then i have to get my physcis books out... And you know what, they are nothing but headache to me

Thank you Armap. Very nice, and both diagrams are right. Of course momentum is not magically lost by the ball as soon as it leaves the shuttle as Balez believes.

Originally posted by Balez
Well that depends on how you wish to see it, will you see momentum as a force?

There is only one way to see it. Change in momentum is the result of a force. It's all you need to know. What you wrote doesn't make sense.

reply to post by nablator

Thank you Armap. Very nice, and both diagrams are right. Of course momentum is not magically lost by the ball as soon as it leaves the shuttle as Balez believes.

Now....
I never claimed that the ball will lose it's momentum did I? I would apreciate it if you did not put words in my 'mouth' so to speak.

Originally posted by Balez
Well that depends on how you wish to see it, will you see momentum as a force?

Since you totally took that out of context, and apparantly did not understand it...
If ArMap's two last illustrations is going to be correct, then momentum means force.
Unless you are stating that the object is travelling with two different momentums and two different trajectories just without any reason what so ever?

There is only one way to see it. Change in momentum is the result of a force. It's all you need to know. What you wrote doesn't make sense.

That makes me happy that you, atleast are not refuting the basics of physics!
I never claimed any thing else.... But if you can find where i claimed that....

What i have claimed is this:
When a object have momentum, and another force affects this object the original momentum will change or completely stop it's original momentum.
But that does not mean there will be no momentum.

[edit on 3-4-2008 by Balez]

reply to post by zorgon

And you have yet to explain what forces are involved in accelerating these 'dust' particles and causing them to change orbit?

If these particles are close to the shuttle, it could be the thrusters that affect the particles.
If they are not close the camera, they could be almost anything, but still i do believe they would be other debris released from the tether.

reply to post by zorgon

And you have yet to explain what forces are involved in accelerating these 'dust' particles and causing them to change orbit?

Several well known forces were mentioned in this thread to explain why some particles' path is visibly deflected: RCS thrusters, radiation pressure, electrostatic force, maybe I'm leaving some other possibilities out. It doesn't matter, these three are more than enough to explain the observed accelerations.

Originally posted by WitnessFromAfar
I would add one more factor in, however. Now we need to know the angle of the ejection point in relation to the shuttle. If we're firing 'into the wake' or 'out the rear'. This would determine how much of each force would be distributed on any particles coming out of the ejection stream.

As a first approximation, anything ejected from the shuttle will move in an almost straight line relative to the shuttle, regardless of the orientation of the shuttle. If you wait long enough, they will follow a slightly different orbit than the shuttle, that's why I say "almost" straight line, meaning close enough to the naked eye.

Only very small particles will behave differently, being visibly affected by forces such as radiation pressure, aerodynamic breaking, thrusters, and maybe some electrostatic force. So yes it would be useful to know.

[edit on 2008-4-3 by nablator]

Originally posted by zorgon
LOL Experiments? So tell me again how we will do these experiments in Space?

I'm sorry Zorgon, I wasn't very clear. I just re-read my posts and I'm not surprised that was confusing. What I meant was that these clips are (completely by accident) experiments, in and of themselves, that we can use for comparison purposes. I say this because there are objects in 'free fall' in the clips, that are moving at a velocity relative to the shuttle (or in this case the ISS, which is also moving) and these objects are then affected by another force (the person touching them, that force is measurable).

I'm sorry I didn't explain that very well the first time. That's all I meant, was that we can tell things by watching the behavior of objects in those clips.

Originally posted by zorgon
Or at the very least a chamber with LEO gravity simulated and no air?

You are completely correct, there is a simulated atmosphere in play in the two clips (#1 & #3) taken onboard the ISS. There is air in the mix there. That is a factor. I was simply looking for a good comparison on the way objects moved in zero g. I couldn't find a good reference clip of an object external to the ISS or Shuttle.

Originally posted by zorgon
And you have yet to explain what forces are involved in accelerating these 'dust' particles and causing them to change orbit?
Hmmmm

Well, for the record, I'm not sure that they are dust particles. However, I'm willing to go through the minutae of the underlying physics involved in order to find out if their behavior is characteristic of what we should expect from dust particles. Most of the last few pages has been discussion pertaining to ice particles from a waste dump that might be 'flying with the shuttle' (I'm still having a hard time understanding how that's possible, and why we don't see such waste in other Shuttle missions, if this is 'normal').

I'm not really sure what these things are. There is still a lot of anamolous movement to my eye, that I've yet to solve for. Anyway, I just wanted to put that on the record I hope my explanation was better this time Zorgon, sorry for the confusion!

-WFA

reply to post by Balez

Unless you are stating that the object is travelling with two different momentums and two different trajectories just without any reason what so ever?

Armap's two arrows are two components of the momentum vector. You add them up.

I'm glad someone's finally mentioned the word 'relative'. The way everything moves in space is relative to something else. Until you get your heads around relativity, you'll never really understand how it all works. Maybe a read of a simple introduction to relativity will help people understand the strange motions of some of the stuff out there. Like Einstein said, 'does London Kings Cross stop at this train?'

WG3

reply to post by nablator

Armap's two arrows are two components of the momentum vector. You add them up.

I did....
I explained it like this, the force is the main thing, but there are other factors that also have to be counted in, as the mass of the objects, their relative speed (momentum) and the force that is put on these particles (the spray of the water).
Now, if the force that affects these particles are greater than their mass and relative momentum, the original momentum will not have much affect on the particles trajectory.

Then you think, but there was alot of force to move the shuttle, due to it's mass, however that force is no longer affecting the water that is about to be released as it is a constant with the shuttle.
These particles that have now been sprayed out into space, have been affected by a force that is much greater than their mass and original momentum.

Remember, there is only one force affecting this ball.
Or if we are going back to the water spray, there is only one force affecting the outcome of their trajectory

Are they relative to the speed of the shuttle? No.
Are they on a relative trajectory as the shuttle? No.
Are these the particles that we see in the STS-75 mission? No.

But i am not denying the possibility of other particles that have been constant with the shuttle, and that has not been affected by any other force than the shuttle put on them.

reply to post by WitnessFromAfar


LOL No problem...

As to waste dumps being normal...

Humans do seem to be the galactic scourge when it comes to dumping crap in space.. on the moon on mars LOL

What a reputation we must have in the "Federation" Cosmic Litterbugs"

And then we sit around the campfire and discuss the physics of dust and debris..

Woah is us...

reply to post by Balez

I think some of the problems about momentum, force and velocity we are having here are the result of different definitions from different people, so it may be a good thing if we agree about these definitions before discussing any more, we may be all saying the same thing but using different words.

To me, momentum has the definition that I learnt at school, the product of the mass and the velocity of an object.

From Wikipedia:

If an object is moving in any reference frame, then it has momentum in that frame. It is important to note that momentum is frame dependent. That is, the same object may have a certain momentum in one frame of reference, but a different amount in another frame. For example, a moving object has momentum in a reference frame fixed to a spot on the ground, while at the same time having 0 momentum in a reference frame attached to the object's center of mass.

The amount of momentum that an object has depends on two physical quantities: the mass and the velocity of the moving object in the frame of reference.

So, and as waveguide3 said, the relative velocities make a difference, that is why I made two different arrows to show the two different forces responsible for the movement when seen from someone not on the shuttle.

For those on the shuttle only the arrow that points to the top of the image is relevant, that is why the ball, when seen from the shuttle, will only look like it is going away in the direction that it had when it was sent out of the shuttle.

In the same way, water expelled from the shuttle will keep on moving in the direction that was given to it when it exited the shuttle, although not all drops of water have the same direction and velocity when they come out of the shuttle, as nablator said.

reply to post by ArMaP

I think some of the problems about momentum, force and velocity we are having here are the result of different definitions from different people, so it may be a good thing if we agree about these definitions before discussing any more, we may be all saying the same thing but using different words.

I think that is an exellent idea!

If an object is moving in any reference frame, then it has momentum in that frame. It is important to note that momentum is frame dependent. That is, the same object may have a certain momentum in one frame of reference, but a different amount in another frame. For example, a moving object has momentum in a reference frame fixed to a spot on the ground, while at the same time having 0 momentum in a reference frame attached to the object's center of mass.

Yes that is right, and a good example on that is angular velocity.
Where an object is stationary, but still has velocity and mass.

The amount of momentum that an object has depends on two physical quantities: the mass and the velocity of the moving object in the frame of reference.

Actually there is only one physical quantity on that, and that is, still force.
Unless that is after the force is already used on the object.
Depending on the mass and the force exacted onto that mass, you will have momentum.
Force is still the factor, without it no action.

So, and as waveguide3 said, the relative velocities make a difference, that is why I made two different arrows to show the two different forces responsible for the movement when seen from someone not on the shuttle.

You are still wrong about the force, there were no force active on that ball only momentum, there were one force though, and that force is the force that ejected the ball from the shuttle, on it's already gained momentum from the shuttle.
Remember this:

"If an object is moving in any reference frame, then it has momentum in that frame. It is important to note that momentum is frame dependent."

When the ejection occurs on that mass (water spray) you change the frame of the momentum.
And at the same time you get the classical "Force equals mass times acceleration" or "F=ma" for short.
And at the last point you get this "For every action, there is an equal and opposite reaction."

And then the mometum that the water had gained from the shuttles force is turned on the shuttle as an opposite reaction to the force exacted on the mass.




[edit on 3-4-2008 by Balez]

Originally posted by Balez
You are still wrong about the force, there were no force active on that ball only momentum, there were one force though, and that force is the force that ejected the ball from the shuttle, on it's already gained momentum from the shuttle.

That is why I said "when seen from someone not on the shuttle". For someone not on the shuttle we have to include the force that gave the shuttle its momentum (and the shuttle gave it to all the things attached to or inside it).

The presence of both arrows pointing to the left (the one on the shuttle and the one on the ball) show that this is common to both objects, making it "invisible" when considered only by those on the shuttle and/or the ball.

My idea was not to show the forces present at the moment (if it had been then I wouldn't have put the arrows on the second and third parts of the sequences), it was to show the forces that gave those objects (the shuttle and the ball) the energy to keep them with their constant velocities (I also ignored that any force would create an acceleration and not a constant velocity).

I think that ArMaP is certainly right that we were all using different terminology to describe the same things. Establishing a base of reference is always helpful.

The same effects are seen in the youtube video I posted earlier when the guy on the ISS flicks what I jokingly called a pack of cigarettes (still wondering what it is though Surely they don't smoke up there?).

So we've established now how any particle waste matter, ejected from the shuttle should behave. At least, we've established parameters.

Has anyone had any luck finding out where the camera is located and oriented on the shuttle? Also we should really try to determine where the shuttle's 'waste dump' points are, if any exist at all. It's possible I suppose that they store waste since shuttle missions are usually of fairly short duration.

Anyone have any knowledge or data on this?

-WFA

reply to post by ArMaP

That is why I said "when seen from someone not on the shuttle". For someone not on the shuttle we have to include the force that gave the shuttle its momentum (and the shuttle gave it to all the things attached to or inside it).

Ofcourse it was the source of the force, but that only works to the point where everything on it has the same momentum, remember this is space.
Then there is no more force involved, only momentum "cause and effect".
Your first illustration explains that very well i think.
The point of perception is not valid in this in this argument.
We can discuss this to the point of it getting boring even, but before we do that i'll give you an text based explanation that makes the point of view not matter.

We have something that is called angular momentum.
A gyroscope, has both velocity and momentum to the degree where it is at the same point not moving in any direction at all.
If you stand close to it, you will notice that it does have momentum, with force exacted on it, after when the force has played out to the point where there is no more force the gyroscope will continue to spin and rely on it's mass and momentum.

However if you stand 10 meters from it you will probably not see this and you will probably only see that it is something that is standing up.
But by your claims, there should not be any momentum involved to explain it.
Your point of perception of this is faulty.

The crew are within the mass that has momentum, there by not noticing it.
Now, this does not exclude momentum.

My idea was not to show the forces present at the moment (if it had been then I wouldn't have put the arrows on the second and third parts of the sequences), it was to show the forces that gave those objects (the shuttle and the ball) the energy to keep them with their constant velocities (I also ignored that any force would create an acceleration and not a constant velocity).

The forces that was put on the shuttle to give it's momentum, is irrelevant after that.
What those arrows are showing are the momentum of the shuttle and the ejection force and momentum of the ball.
What is relevant however is the force exacted on the ball on the point of ejection.
I dont want you to contradict yourself "To me, momentum has the definition that I learnt at school, the product of the mass and the velocity of an object."

reply to post by Balez

Let me see if I can make myself clear about this momentous problem.

If momentum is the product of the mass of the object and its velocity, from where came the velocity? From an acceleration.

From where came this acceleration? From a force.

The force applied to the shuttle to make it accelerate had the same direction of the resulting acceleration. The final velocity, after the shuttle had stopped accelerating, has the same direction as the acceleration and the force that created it. The momentum, being a direct result of the velocity, has the same direction as the force that started all this.

So, the arrows show the directions of the force that started the acceleration, the acceleration, the velocity and/or the momentum, they all have the same direction.

In the second drawing I included the two components because I wanted to show the reason for the ball keeping its movement along with the shuttle while moving away from it. If the ball is ejected at 10km/h from the shuttle it will move in a direction that is perpendicular to that of the shuttle but it will not move only on that direction, it will keep the direction of its previous movement while inside the shuttle and so it will keep on orbit, it will not be a ball orbiting at 10km/h, it will be a ball orbiting at a slightly higher velocity than that of the shuttle and with a slightly different direction.

In conclusion, and returning to what started all this, I think that it is possible for some drops of the water ejected from the shuttle to exit the shuttle at a very low velocity (when compared to the shuttle) and so they could appear on the videos and photos taken from the shuttle.

But that does not explain the change in direction from the objects we see, it may only explain the presence of water drops (and from those, ice particles) near the shuttle.

Anyways, we can exclude a water dump.
I have been checking the mission logs for that time, and they did not do any water dump.

The tether experiement started on mission day four, the sequence we are seeing with the debris are filmed on mission day seven.

However they did a water test dump on day four, the same day as the tether experiement.
2 pages for nothing (i got a headache though)
Source: STS-75 Mission Log

Another investigation of Columbia's surroundings made use of the orbiter's Flash Evaporator System (FES). To accomplish this experiment, the crew participated in activating and deactivating the orbiter's water release systems and manually operating the Shuttle's attitude control system jets. This provided a controlled means of studying the distribution of neutral and charged particles in the vicinity of the payload bay during Shuttle water dumps.

Source: STS-75 Mission Day Four