9
$\begingroup$

Space junk is a real threat to working satellites in the Earth's orbit. Is it theoretically possible to make this space junk escape from the Earth's gravity (by giving them some kinetic energy to overcome the Earth's gravity), make it travel towards the Sun, and let it burn in the intense heat environment of the Sun's coronasphere? The space junk may orbit the Earth at any altitude.

Are there any practical problems in doing this?

$\endgroup$
  • $\begingroup$ I don't want to leave this as an answer since it's not scientific but what if we built a deflector with an understanding of each 'junk' out there to shoot to the sun. it would understand the shape, speed, etc of the space junk and would turn its panels so that when the SJ hit the deflectors, the bounce would send it off to the sun. $\endgroup$ – John Riselvato Aug 10 '13 at 13:55
  • 1
    $\begingroup$ @JohnRiselvato - What would be "holding the deflector in place" to enable the space debris' own kinetic energy to transfer as much as possible to a new vector? You would need same amount of energy to do that (possibly more due to momentum transfer inefficiencies, i.e. some of the kinetic force converted to heat, e.t.c.), than if you applied vector changing force on the debris in a more direct manner, like e.g. attaching a thruster to it and let it burn when in suitable position targeting the Sun while in orbit around the Earth. $\endgroup$ – TildalWave Aug 10 '13 at 15:03
9
$\begingroup$

It is possible to remove any and all space junk and put it into a solar orbit.

It is highly impractical, though. The ∆V (Delta-Vee = total change in vector)

Attaining escape velocity requires (very roughly) about 3x the energy as attaining LEO. Plus you have to capture, and that eats ∆V. Further, launches are expensive in and of themselves, and generate micro-debris in orbit.

Further still, there is little reason to send it solarward; for the same ∆V, one could return the junk to Earth for reuse. Or, eventually, potentially take it to an orbital manufacturing facility for reuse in orbit.

The larger stuff isn't much of a concern, anyway. It's easily tracked, its orbits are known and predicted months in advance. (Note that LEO is still experiencing atmospheric drag, minimal as it is, and that such orbits can't be accurately predicted on the scope of years due to variations in drag. This is part of why Skylab came down earlier than originally predicted.) Small stuff is the problem. Orbital tracking can track objects of several centimeters; most of the damage to spacecraft in orbit has been from debris estimated at a handful of millimeters across.

$\endgroup$
  • $\begingroup$ For that matter, ejecting it from the solar system entirely would still take less delta-V than dropping it into the sun. $\endgroup$ – Sean May 10 at 3:35
4
$\begingroup$

It is completely theoretically possible to dump things in to the sun, given enough energy. How much energy would it require? Well, there isn't a table I've seen that shows how much delta V is required to shoot to the Sun, but there is a convenient one for Mercury, which we can safely assume is less than would be required to get to the Sun. The Delta V requirements to directly get to Mercury from Earth are 48 km/s. That includes landing and returning to Earth, but even that would only add a factor of 2 or so. Given about 10 km/s to orbit, that's a huge rocket, just to get to Mercury. Real missions save some of this by doing flybys, but they require active course corrections for some time to get things just right. That's a huge amount, far more than any ship is likely to have!

So, what are some alternatives? There are basically 2 main goals for space junk removal, depending on where the item is. The first is to make it crash in to Earth (Or another suitable object). The second is to get it outside of a usable orbit.

Okay, so how are these accomplished? The first can be done by simply slowing the object down to the point where it lightly touches Earth's atmosphere at it's minimum point. Given enough time, that will cause the object to re-enter Earth. Assuming it's not that large, this shouldn't pose any danger at all.

The second possibility is to have it enter a useless orbit. GEO would require substantial fuel to re-enter Earth. Instead, what they do is raise the orbit by a bit such that it will never intersect the GEO orbit, at least, not for a very long time. This basically eliminates the possibility of impacts.

$\endgroup$
  • $\begingroup$ Mission dV tables at Project Rho: projectrho.com/public_html/rocket/appmissiontable.php $\endgroup$ – Deer Hunter Aug 10 '13 at 16:15
  • $\begingroup$ No, the ΔV to reach Mercury has little to do with what it would take to drop something into the sun. If you're going to hit there's no reason to circularize your orbit. $\endgroup$ – Loren Pechtel Aug 10 '13 at 16:56
  • 1
    $\begingroup$ ∆V to hit the sun should be lower than to orbit Mercury. You neither need to brake to orbit, nor fight solar gravity. You just need to escape earth orbit in the correct direction. $\endgroup$ – aramis Aug 10 '13 at 17:28
  • 1
    $\begingroup$ That's what I get for not paying enough attention... Sigh. Still, the delta V is high, just not quite that high... $\endgroup$ – PearsonArtPhoto Aug 10 '13 at 19:49
3
$\begingroup$

There is a small issue.

A lot of space junk that we have created are really tiny, like dust or other small things, but they are also travelling and stupendous speeds.

So you will either need to travel to it which requires fuel and energy, and then force it towards another orbiting body or indeed the sun.

Or, you can have a net or surface to either capture or bounce the junk to it's destination, which would have to be pretty strong, because some space junk can be moving at 20,000 mph and faster.

Countries have been coming up with solutions of space junk, however it will be horrifically expensive until we create the "space elevator".

$\endgroup$
  • $\begingroup$ Maybe I do not understand your answer correctly, but how can a space elevator help to reduce the amount of space debris? You avoid adding new debris, ok, but it does not make sense for removing pre-existing debris, does it? $\endgroup$ – s-m-e Aug 19 '13 at 18:01
  • $\begingroup$ Well because space elevators give the ability to move things into space for a 220 dollars per KG, compared to the 4.3k-40k dollars per KG. So obviously less expensive and waaaahahahaaay less environmentally harming. Just saying. (en.wikipedia.org/wiki/Space_elevator_economics) $\endgroup$ – SevenZero Aug 19 '13 at 20:09
  • $\begingroup$ Ok, estimated price tags. It still does not explain, how this could interact with pre-existing junk in space ... ? $\endgroup$ – s-m-e Aug 19 '13 at 20:13
  • $\begingroup$ Obviously not the elevator itself, but you can get the elevator to carry some sort of robot with a rocket into space so it can move around and either force the debris into a collision course with Earth, or out of Earths effective pull. $\endgroup$ – SevenZero Aug 19 '13 at 20:46
1
$\begingroup$

The point at which the force of gravity from the sun & earth balance out is L1 -- which is roughly one million miles from Earth. (92 million miles from the sun).

So to get space junk to the sun, you'd need sufficient energy to get it out of earth's orbit with enough momentum to get past L1. For spacecraft, they use gravity assist from the earth & moon.

For earth orbiting space debris, it's much more cost effective to just slow it down so that it comes down to earth ... even with attempting to stear it so that it burns up in the atmosphere or comes down in a safe location it's going to be easier than getting it to the sun.

$\endgroup$
1
$\begingroup$

You can theoretically dispose into a solar orbit by injecting the spacecraft into an Earth Escape Orbit. For example, from a GEO orbit it would only require 30% more Delta V than the one required to de-orbit.

Its just much more expensive, but could be much more cost effective with the use of solar sails and low thrust propulsion for example.

$\endgroup$
-1
$\begingroup$

Theoretically, yes. Practically, I think it would depend on the object's orbit.

Some satellites are de-orbited when they reach the end of their useful life, causing them to descend into the atmosphere and burn up. I believe some satellites are actually boosted out of Earth orbit at end-of-life, presumably because they are in a relatively high orbit and the delta-V to escape Earth is less than the delta-V to bring them down.

The space junk in low orbit will eventually de-orbit all by itself, just from the cumulative effect of atmospheric drag. It's just a matter of time.

$\endgroup$
  • $\begingroup$ "boosted out of Earth orbit" - I have never heard of that, but I could be wrong. Are there examples? I think the usual procedure is that stuff in 'high' altitudes (GEO) is to move beyond GEO. This is then called a graveyard orbit. $\endgroup$ – s-m-e Aug 19 '13 at 18:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.