Right now the economics for this don't add up. The risk of collision is quite low compared to launching "extra" satellites with the sole purpose of finding and tracking another satellite. It is also much more difficult to target an arbitrary piece of debris. If the incoming debris is in a similar orbit (both altitude and inclination) then it requires less fuel to be able track and find it. If the incoming debris/satellite is in a different orbital plane it requires a huge amount of fuel in order to change orbital inclination [0]
Sorry, not practical. Intercepting debris requires FAR more delta-v than you may expect. Changing the plane of your orbit is so expensive you just don't do it. Its cheaper to just launch a new satellite in a different plane. For example, to intercept hubble from the ISS (or vice-versa) you are looking at a velocity change of a bit over 3000m/sec. Compare that to delta-v of just over 9000 m/sec to reach the ISS from the surface of earth.
Lets say you are in a really, really close orbit to your target and you only need to spend delta-v of 100m/sec to intercept . If you only use 90% of the fuel you'd need to perfectly match orbits then you are still going to impact your target at 10m/sec. Thats 36 km/h, which is a very violent collision. You aren't going to just grab your target on the way past.
How would that work? A rocket launches into orbit an unmanned satellite capable of autonomously intercepting the orbit of debris in order to collect it and then deorbit itself? Seems extremely expensive for little benefit.
It's my understanding that atmospheric drag and orbital perturbations due to the gravity of other celestial bodies cause satellites to need station keeping maneuvers just to avoid crashing into the Earth. So it seems to me that this debris problem will eventually take care of itself.
An interesting idea, but it would be prohibitively expensive; in terms of Delta-V and cost.
You are already launching a satellite into an orbit where it will try avoid existing space debris. So, anything added to the payload to de-orbit space debris would have to spend delta-v adjusting it's orbit to match that of the space junk. Then it would need enough fuel left over to de-orbit the target.
I think it would be better if a certain amount of the launch cost would go towards a fund meant to de-orbit space junk.
I don't think debris 'going higher' isn't much of a problem. Whenever this happens the orbit is going to be more eccentric - meaning a lower periapsis, and consequentially lots of drag that will cause a rapid deorbit.
On the second point about parabolic orbits I also find that probably relatively low risk because we are only talking about a fraction of an orbit for a collision to occur so unless the debris field was massive the chance of another collision is probably still low. Remember when we are modelling orbit collisions normally we are often talking over 25+ years - 100,000 + orbits.
I think the main problem is busy orbits (e.g. sun-synchronous polar orbits at popular altitudes) where most of the debris remains roughly in the same orbit following an acute collision but has a lot of other potential collision targets. Also as satellites are disabled by a collision they lose the ability to avoid other objects already in the same crowded orbit - i.e. the fraction of objects able to take avoidance decreases increasing the chance that future collisions are from 2 incapacitated satellites, removing the possibility of avoidance.
Yeah it's difficult to envision a truly cost effective ASAT measure, "shooting" bullets is deceptive in that it'd still require carrying the large amount of fuel needed to effectively change orbit (especially for changing inclination) and would be a bit too messy in terms of spread of the resulting debris.
Another interesting and clean approach might be jamming the satellites from orbit. You can't go after all the satellites, but since you can predict which ones will be over when you're doing something important, you can launch vehicles to approach specifically those and jam them at close range.
> You could do this hundreds of thousands of times in LEO and thousands in MEO and still barely change a single satellite’s collision odds.
I have to think that multiplying the number of debris objects by 300,000 for a few months *, and preferentially targeting that debris at a specific satellite would change its odds a bit. So, you're way off in hyperbole-land at this point.
Of course, it all depends on what we mean by "targeting". Still, one launch gets you approximately 3x the total amount of debris in orbit, and the opportunity to choose how it's distributed.
* Objects with a mass/surface area ratio of ~15 kg/m^2 decay in about a year in LEO, depending upon space weather and other factors. The tungsten balls have a ratio of 32 kg/m^2, so can be expected to last a fair bit longer.
A few problems holding a solution like that back right now:
1) It takes a ton of fuel to change your orbit once you're in space, and space is _really_ big (even just the orbital ranges we're talking about). It's just not currently feasible for a ship like that to capture debris and then use _more_ fuel to bring it back down.
2) Relative velocities of some debris are so large (and they are so spread out) that it's not yet feasible to capture it and bring it back with any current approach.
Dead satellites are mostly dangerous for the scattered debris they _might_ become if something hits them/they bread up. So while bringing them back is important, it's not as immediate a danger as things that have already broken up.
Basically, we don't have any approach that would make a major difference, even if money was no object (which it is).
The cheaper it is to launch, the easier it is to clean up orbital debris. The risk from debris in orbit isn't from too many satellites, space is pretty damned empty, the risk comes from thousands upon thousands of fragments, some of them created intentionally. Moreover, as it gets cheaper to launch satellites it also becomes more and more possible to add extra weight to them, to put in backup systems which deorbit the satellites if they become inoperable.
The debris would be harmful to other satellites in orbit. Since it introduces significant risk, they cannot just shoot them down without a good reason.
IMO we need to stop putting satellites in orbits above ~800km altogether. No matter how careful you are there will always be accidents, and once a collision or explosion occurs in high orbit the debris is essentially a permanent fixture of the solar system, lasting far longer than a human lifetime. There is no feasible method to clean up such collision debris for the foreseeable future. Even assuming SpaceX Starship is wildly successful and launching a thousand times more mass to orbit for dirt cheap, collision debris cleanup is still infeasible. The only realistic way of cleaning collision debris is the natural way, the atmosphere. But it only works on reasonable timeframes when you're below a certain altitude.
Luckily the reasons why we used to launch satellites into high orbit are mostly obsolete now. We did it for three reasons: firstly so the satellites would last longer because they are expensive, secondly to get higher land area coverage from fewer satellites again because satellites are expensive, and thirdly to make it possible to use stationary or slow-moving satellite dishes. Now that launching satellites is much cheaper and likely to get even more so, the first two reasons are obsolete. The third reason is made obsolete by modern phased array antennas that can be pointed without moving. So we don't need to take on the debris risk from high orbiting satellites anymore.
AIUI there are already regulations requiring that satellites be able to de-orbit themselves at EOL, and have some maneuvering capability in order to actively avoid collisions. This is directly paid for by the owners of these satellites as part of the development cost. Most of the objects at high risk of collision are either very old satellites, or debris from collisions of old satellites, from before these requirements existed.
Tracking space debris and other objects in orbit of the earth is something we'd probably want to do anyway, and it makes no sense to duplicate that effort, so of course that burden will be distributed. If that burden becomes too high I'm sure some tax or licensing fee will be introduced to pay for it (assuming such a thing doesn't already exist) but in the grand scheme of things those costs are irrelevant compared to the cost of launching something into space to begin with... Especially when the satellite is still functioning, and generally aware of its own position anyway.
You don't need to find a bunker, but there's a risk that we'll soon have a lot more 'space debris' in orbit. If a collision happens, it'll basically turn the colliding satellites into scattershot, leading to a higher likelyhood of other smaller collisions with other satellites (less spectacular but could still disable even more satellite). Not sure how likely the latter scenario is, but it could get very costly if it did happen.
This is very pessimistic - basically every space-faring nation now has pretty strict licensing requirements for new spacecraft, a portion of which is a plan to deorbit / move to a 'junkyard orbit.' In the US, this is actually handled by the FCC, because a satellite you can't talk to might as well be debris. [0]
In general, the economics of debris removal are also really unclear, because the actual risk of collisions is still pretty slim and the potential legal risk of touching another nation's spacecraft are high. Many objects are also too small to be tracked. The community is largely shifting towards debris avoidance, rather than mitigation - i.e., tracking and maintaining custody of debris, and maneuvering out of the way when necessary. This is pretty straightforward, since we already do a lot of space object tracking and maneuvering anyways. A variety of commercial companies have already moved into this space, including giants like AGI [1].
There have already been six "Unintentional high-speed collisions between active satellites and orbital debris" [0], the most recent of which was in 2021.
There is more to worry about than just tracking satellites following "extremely well known paths". You could have a situation like Intelsat 29e [1] where a satellite is torn to pieces, creating a debris field with parts too small to track. You can't avoid what you can't see.
There are other attempts at disposal of dead satellites that don’t rely on a long-shot like the BFR [1]. Besides, maneuvering a big heavy spacecraft like that to match orbits with a bunch of little satellites would be tremendously wasteful in terms of fuel. A much better use would be to remove larger satellites like defunct communications satellites. These are actually a much bigger danger to orbital space as well. See this event for example [2], which generated over 2000 pieces of debris large enough to track and many more of a smaller size. Small satellites are not nearly as dangerous because when they are defunct their low mass causes them to renter faster.
(FYI I’m a PhD student in the lab that built the satellite in the article.)
Energy is the bottleneck. Lasers don't provide that much kinetic energy... so you're either briefly firing a powerful laser or continuously firing a small laser. The other energy cost is movement, I don't know how often the satellite would have to move to find debris but the larger satellite has more mass while the smaller one has to expend energy to match debris orbits.
There are small debris clouds, but also large uncontrolled spacecraft, like boosters. De-orbiting those could be a huge help, since a collision with a stray booster would create gobs of debris so those orbits may be completely avoided.
Why would private companies do this? Who is paying them and how would the cost structure work?
Debris in orbit is not like trash on a field. It is moving at several km/s and is thousands of miles away. Good luck finding, intercepting, and then spending enough energy to de-orbit anything large, let alone tiny objects you can't see. I can't even imagine doing this millions of times.
[0] https://en.wikipedia.org/wiki/Orbital_inclination_change
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