This source does not claim, that a rocket is a closed system.
Yes, it does.
A rocket is all a rocket is.
Please excuse for asking so bluntly, but are you trying to be dense on purpose?
The source says, as you quoted: "If we define our system to be the
rocket + fuel, then
this is a closed system."
The system is explicitly defined as "rocket + fuel" and "this" system is then considered closed for the purpose of calculating momentum/acceleration.
It does not say, that the rocket itself is a closed system.
It also doesn't say, that the defined system "rocket + fuel" can be considered closed under any circumstance - that is only true for the assumptions made.
Would you also say, that fuel or passengers are part of a car?
So when you're running on empty or someone gets out, your car is missing parts?
There are different valid definitions for systems in a given setting; however, some are more useful (or expedient) than others.
In that sense a car is not necessarily a car and a rocket is not a rocket. It depends what has been defined and once defined, you have to stick with that definition for the time being.
So what is your definition of "rocket"? Which parts a part of it (pun intended) and which aren't?
Does that mean, you now agree, that rockets will work in a vacuum?
I am not the one left to explain videos, clearly proving a rocket will not work in a vacuum, somehow do prove a rocket will work in a vacuum.
Did I reference videos? I don't think so.
I was referring to the explanations, how conservation of energy and momentum would require rockets to work in a vacuum.
Are you bringing up videos again to deflect from your inability to construct a fault in the open/closed system discussion?
Changing the scope of the system doesn't change the fact, that rockets work in a vacuum, it simply changes your view of the problem.
Perhaps explain to thor's evil twin, because it is apparent he doesn't.
Actually it's quite apparent, that you do not understand how systems can be defined, what the theory behind different types of systems is and how that can be applied in science.
Where do you get the idea, that thors_evil_twin doesn't understand?
He appears to have a much better grasp of the issue than you do.
Please point to where you think he's wrong?
Well, it is apparent you do not even know how how to define the word," exchange."
Obviously appearances are deceiving ... what do you think is my definition of the word "exchange" and why would it be wrong?
A rocket is a closed system.
Kind of depends on your definition of "rocket". As defined by the source you quoted, it is only a closed system, when you include the fuel (inside the rocket and after being expelled) and only under the circumstances given.
In any case, this does not affect if a rocket works in a vacuum or not.
So what is your point, except being contradictory without providing substantiating facts or reason?
iC