I remember asking once, we don't we just shoot our surplus trash off into the sun and was told that by the cost of launching it outweighs the benefits. Fair!
But what about all of the old satellites and space stations? Why don't we just send a giant magnet around the earth once or twice and then slingshot all that space junk into the sun and thus giving all science fiction writers (when they return from their strike) a plot point they can no longer use in their film scripts?
Seriously though, without the cost of breaching the atmosphere, this seems really cheap to pull, why don't we do this? Why isn't this a standard thing?
Getting to the sun is EXTREMELY energy intensive. It's a lot easier to get to the outer planets. Also a cloud of space junk is really big and really spread out. It's equivalent to raking a magnet across the surface of the entire earth to look for your house keys
But the speed doesn’t really matter, so it shouldn’t be very energy intensive at all. Just gather up some junk, launch it at the sun with an expendable thruster, and be done with it. If it travels at a couple hundred kph, or even less is completely irrelevant. Let it take a couple hundred years to get there, it is supposed to burn up anyway no? And if it collides or is otherwise destroyed en route during that time won’t matter much either.
That's not how orbits work. You can't just point at the sun, accelerate slowly for 10 seconds and then you will arrive in a few hundred years. If you did that, you would still orbit the sun, just in a slightly different orbit than before. To actually reach it or get near enough to it that the junk burns off, you have to expend a lot of energy.
But if it could get into the orbit of the sun wouldn't it still burn up?
Well this is easily answerable given our planet orbits the sun and doesn’t burn up. Even Pluto which is very far away orbits the sun.
How close would we need to get? I mean we sent something to Mercury after all
It already is in orbit of the sun. Getting it to a new orbit of the sun will no more get it to the sun than keeping it on Earth unless you use a lot of energy.
It would still take a lot of energy to get it close enough for it be effected by the sun. It would probably be easier to go further out and get a gravity assist from another planet or one of their moons.
It’s not about speed, but energy. Virtually all satellites are gravitationally bound to Earth. Think of Earth’s gravitational potential as a funnel. The satellites sit somewhere on the walls of the funnel. Now, next to the Earth’s funnel, there’s. much deeper funnel: The Sun’s gravitational potential. But between where the satellites are and the point where the Sun’s potential starts attracting them is still a big "hill" or wall separating the two funnels from each other (the top of that hill is the Lagrange Point L1). So to get a satellite out of Earth’s potential to a point from where it could “fall” towards the Sun still requires a large amount of energy.
To get to the sun you have to decrease your speed. Speed absolutely matters here. If it were possible to round up all the space junk (which it currently isn't) we might as well just set it adrift outside the gravitational influence of Earth
Isn't that just polluting?
But look at all the Space X satellites that have to be replaced every so often, the fact we can't send a giant magnet up to capture the old ones just seems irresponsible. In fact everything we do with space and not considering how to dispose of it is trash.
From what I understand is that the space x satellites when worn out, will slowly drop from orbit (because they already have a really low orbit) and burn up in the atmosphere. So there's that.
Spacex satellites (and all other satellites) have thrusters to drop their orbits. The problem is the old ones that either broke or never had thrusters.
That's just plain not how orbital mechanics works. The difficultly with falling into the sun is that we're starting from a high energy state (orbit) and so in order to fall into the sun we have to scrub all our extra energy to get back to zero.
Think of it in reverse. If you were standing on the sun, it would take an absurd amount of energy to launch into an orbit, and only some of that energy actually goes into lifting your payload. Once your at your orbital height you have to keep adding energy in order to go sideways fast enough to maintain orbit.
It's all the sideways momentum that you have to oppose in order to be able to actually hit the sun.
Edit: Orbital mechanics don't follow your intuition, given that you didn't evolve in an ecosystem where they impact your life. It's actually less energy intensive to climb to a higher orbit first, then scrub your remaining horizonal velocity in order to fall into that sun.
So can't you have a tiny rocket and a computer to do the calculations and angle adjustments? Isn't that how they landed on Mercury?
You generally do something like multiple gravity-assists perhaps coupled with going to a higher orbit first before coming back in. You have to remember that each individual space mission is centered around moving an object roughly the size of a minivan. It's just completely not worth it to try and send our garbage or even just our space garbage anywhere far from where it is right now.
For a while they did nothing with space junk. These days low-earth orbit is actually getting kind of crowded and people realized we have to be a little more responsible. Each mission has plans for how every piece of debris will be handled. For some, that means sending back down to earth, for others, that means crashing it into whatever planetary body is nearby, and for others that means putting the object into a graveyard orbit. A graveyard orbit is just an orbit where we've decided to leave the junk in an "out of the way" place where it's unlikely to change orbit or collide with anything.
These might help get you an intuitive understanding of how orbital mechanics works.
https://youtube.com/playlist?list=PLSL-UN9SB11jK2pNTDffUS7vU-hJn7-Zf&feature=share9
Thank you very much