Changing a spaceship's direction via ejecting mass

[CyborgTriceratops]

 

You would have serious difficulty using kids as mass ejection to alter the speed and direction of said spaceship. Heck they eat a lot , their mass thus, changes from moment to moment, the also excrete mass, chew mass, drink mass and come in different sizes and shapes?. How do you eject these odd shaped objects at the exact correct angle, at the exact correct velocity, do you have different ejection ports for different size kids?. Only after you have resolved those issues to exactitude, can you think of coming up with the correct mathematical equation.

In a normal spaceship, I would fully agree with you. The one in my equation lasts a combined total of maybe 2 minutes, so there is no additional mass change save for any unwanted gas breaking, and the entirety of the spaceship is kids, nothing else.

 

 

 

a) You write the equation first and then determine the mass(es) to use.

 

b) "Round cows": for the purposes of the OP it is almost certainly accurate enough to approximate an average mass per kid (and the effects of a meal, excretion, etc. are going to be very small, anyway).

That is what I am doing. Swansont is deffinitly helping out a lot, but now I seem to be stuck until I can determine the actual masses and speeds that I need.

[Alan McDougall]

a) You write the equation first and then determine the mass(es) to use.

 

b) "Round cows": for the purposes of the OP it is almost certainly accurate enough to approximate an average mass per kid (and the effects of a meal, excretion, etc. are going to be very small, anyway).

 

Nevertheless you need to know the mass of the kids before, or after the equation, a small difference in mass could result in a huge accumulating error over enormous distances of outer space.

You write out the equations the way a physicist does, i.e. symbolically. You can come up with an equation that is a solution without knowing any of the numbers. In this case you will have an infinite number of solutions for any desired result, because mass, speed and angle are all variable. Or, you can restrict the values of the variables and come up with a range of possible solutions.

 

A mistake that many physics students make is substituting numbers in for symbols way too early in solving a problem. Plugging numbers in (and calculating) is often the last step in a problem.

 

Nevertheless, you must at some stage plug in the numbers and they must be as accurate as possible.

[swansont]

 

Nevertheless you need to know the mass of the kids before, or after the equation, a small difference in mass could result in a huge accumulating error over enormous distances of outer space.

 

Nevertheless, you must at some stage plug in the numbers and they must be as accurate as possible.

 

This this thread is just an intellectual exercise. Yes, you need accurate numbers if you were actually going to build something like this, but nobody has suggested doing that.

[Alan McDougall]

 

This this thread is just an intellectual exercise. Yes, you need accurate numbers if you were actually going to build something like this, but nobody has suggested doing that.

 

Shooting kids out of a spaceship is an intellectual exercise ?

[Strange]

 

Shooting kids out of a spaceship is an intellectual exercise ?

 

I hope it is (and not a real exercise).

 

Also, note that in the book/film/question, kids are not being thrown from a spaceship, but from a larger group.

Edited January 9, 2014 by Strange

[swansont]

 

Shooting kids out of a spaceship is an intellectual exercise ?

 

Until you can show me an actual example of somebody doing this (for reals), yes, it's an intellectual exercise.

[Alan McDougall]

 

Until you can show me an actual example of somebody doing this (for reals), yes, it's an intellectual exercise.

 

But why use kids?

[Strange]

 

But why use kids?

 

Because that is the scenario in the movie/book. Note that they are not thrown out of a spaceship: "no kids were harmed in the creation of this scenario".

[Alan McDougall]

 

Because that is the scenario in the movie/book. Note that they are not thrown out of a spaceship: "no kids were harmed in the creation of this scenario".

 

 

They were not kids but the figment of someones imagination, he should have imagined a better way of changing the spaceships direction, surly there were other objects in the spaceship that could have been used for the same purpose?

[Strange]

It WASN'T a spaceship. Read the OP again.

 

The specific scene I am refering to is the scene in the battle dome where Ender has his army form a 'wedge' of sorts around a main player and then floats their way through the battlefield, ejecting kids at certain angles to make his needed course adjustments.

 

It was a bunch of kids. The only thing the bunch of kids could use as mass to change their velocity was some of the kids. Because that is all they had: a bunch of kids. (OK, they could have tried throwing their underwear, but I doubt that would have been very effective.)

[Alan McDougall]

It WASN'T a spaceship. Read the OP again.

 

 

It was a bunch of kids. The only thing the bunch of kids could use as mass to change their velocity was some of the kids. Because that is all they had: a bunch of kids. (OK, they could have tried throwing their underwear, but I doubt that would have been very effective.)

 

I have been silly nit picking about totally irrelevant things, sorry it will stop pronto