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?
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Kerbal Space Program certified astrophysicist here.
Getting into earth orbit is hard enough. Hitting the sun is also surprisingly hard. Well, hitting it is in itself not that hard, but carrying the amount of fuel needed is.
To hit the sun you need to hit an escape trajectory from earth. One you’re in low earth orbit, thos isn’t THAT hard, but it requires a lot more fuel than one would normally pack into a normal satellite.
And once you’ve escaped earth, that’s where the real fuel expenditure has to happen: do nothing, and you’ll remain roughly coplanar with earth (and in all likelihood eventually be recaptured by earth gravity). What you need to do is to burn retrograde, as in slow down your orbit, so you start falling straight towards the sun instead.
Wait, I’ve just met my first celebrity on Lemmy. I need to keep this moment stored in my memory banks.
Okay, my first question isn’t the space debris all in earth’s low orbit already?
Second question, can’t you ride the orbit and then use a tiny thruster to leave the atmosphere and follow that trajectory straight towards the sun. I imagine the calculations needs to miss every planet between us and the sun wouldn’t be simple, but thirdly, technically this should be possible right?
Lol space is so big that even if you try, it’s hard to hit a planet. Also “ksp certified astrophysicist” is a joke, ksp is a video game which teaches you a lot about orbital physics. It’s a common joke in the Spaceflight community that ksp teaches you more about astrophysics than an actual job.
Correct. I’m an IT dude by trade.
I’m a physicist and I love KSP. You can learn a lot of things about orbital mechanics from textbooks, but KSP offers a great way to see how everything works. One of my TAs actually used it for teaching, to illustrate homework problems.
The problem with picking up space trash is that it’s spread all over in all sorts of orbit. To pick up said trash, the spacecraft will have to alter its own orbit to intercept trash.
The issue isn’t so much the size of the thrusters, but the amount of fuel needed. In space, everything coasts along its current orbit, and to go elsewhere you need to expend propellant to alter your orbit. Either by burning loads of fuel in a short amount of time, or with the thrust spread out over a longer burn time.
And when you’re finally ready to head into the sun you need to escape earths gravity well, which takes abbunch.
And to hit the sun you will in effect have to burn enough fuel to cancel out the orbit that you inherited from earth to begin with. I don’t have the DeltaV numbers in my head, but the fuel cost is immense.
Think of it as a representation of how much energy is needed for orbits. To get to the moon you need about 1.7 km/s of delta v. To get to sun you need 30 km/s of delta v. To escape our solar system you only need 18 km/s of delta v.
Think of it this way. The earth is moving horizontally to the sun at 29.78 km/s (107,200 km/hr). In order to hit the sun you have to cancel all of that movement otherwise You’ll miss the sun and enter a new elliptical orbit.
Hmmm, I was thinking we could slingshot our own orbit. Use the centrifugal fly South and use a couple thrusts to point towards the sun. I was clearly over simplifying it.
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
After a good chunk of asking and following up AI gave me a nice sounding answer: “That’s a good question. According to an article on NASA, it takes 55 times more energy to go to the Sun than it does to go to Mars. The reason is that Earth is traveling very fast — about 67,000 miles per hour — almost entirely sideways relative to the Sun. The only way to get to the Sun is to cancel that sideways motion. It takes a lot of energy to do that.”
But sling shots? I saw something that mentioned NASA used sling shots and centrifugal force to get something somewhere and in fact, haven’t they sent a bunch of stuff to Venus lately? We just need so keep sling shotting around planets until boom, we’re in orbit of the sun circling until we get low enough to get melted!
It’s called a gravity assist and can save a lot of fuel at the cost of travel time. (no centrifugal force involved) It also takes a lot of planning effort. It still takes a fair amount of fuel to reach the moon, and to set up more gravity assists. It’s much easier to slow things down just enough that they will fall and burn in the atmosphere.
The idea of a “giant magnet” wouldn’t work. Magnets have a sharp falloff and making them bigger doesn’t change their maximum range by that much. Even the core of the earth, a massively strong magnet, is barely perceptible to us on the surface. Attempts to deal with space debris rely on sending a spacecraft to dock with it because that is really the only way.
On a separate note, dropping them into the sun is pointless because it would use a large amount of fuel and it’s much easier to have them burn up in the earth’s atmosphere. This generates some greenhouse gasses but there are too few satellites in orbit for this to really matter.
If you want to learn more about orbital mechanics, I would recommend checking out Spaceflight simulator (a free mobile game) or Kerbal Space Program (a desktop game available on Steam for windows, Mac, or Linux, there is also a console version but I have heard bad things about it). Both are fun games where you build rockets and find out about orbital mechanics along the way.
Thank you for taking the time to enlighten me
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We should recycle and decompose everything on Earth and anything that can’t be recycled or decomposed, shouldn’t be made, that goes without saying… But this is about the space debris, the satellites, the nuts and bolts, the broken parts of space stations, the old space stations and I’m not suggesting we fly them, hence talking about sling shots, I’m talking about pushing them and letting the applied force carry it all to the sun.
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Well since it’s so easy then just go do it! I take it you’ve never taken a physics class before
Please consider me stupid on this whole subject. I’m here to learn
To hit the sun, you’d need an object to cancel out all of the speed it has as part of orbiting with the earth around the sun, so that it could fall in. That 29.78km/s requires a lot of fuel to achieve, getting into orbit of earth only requires around 8km/s of delta-v.
So to go from an earth orbit to fall into the sun would require more than twice as much fuel as it took to get from the ground into that orbit in the first place.
If you want a more in depth dive, with more a focus on why shooting nuclear waste into space is a very bad idea: https://youtu.be/Us2Z-WC9rao
The sun is hella far away, like 8 light-minutes. Even easier to just fling it any old direction that’s not “at the moon” or along our orbit path… we’d still never see it again.
But it is definite not that big a deal to leave it up there, especially compared to the cost of slingshotting it away.
