[rzimmerman]

Active debris removal (harpoon satellites, magnet arms, whatever) are not a solution to this problem and are a huge waste of money. These missions answer the question "could one dock with debris and deorbit it?" To which the answer is "obviously yes, but at enormous cost" and you don't need to spend 50M euros to prove it.

The answer is exactly what governments and industry have been doing for at least two decades now. Tracking of in-orbit objects, coordinated conjunction response, and rules that require either manual or drag-induced reentry cleanup at the end of a mission. Active maneuverable satellites in orbit (like Starlink) aren't a fundamental problem. The number of objects has gone up significantly, but the big actors are coordinating and following good practices.

[spartanatreyu]

> Active debris removal (harpoon satellites, magnet arms, whatever) are not a solution to this problem and are a huge waste of money.

This is wrong because it's based on a flawed assumption.

That assumption being: Propellant is required to deorbit debris, and the rocket equation makes launching all that propellant prohibitively expensive.

And while we can't do anything about the rocket equation, we don't actually need to have propellant in space to deorbit things.

Ways to deorbit without propellant in space:

1. The ground based methods. Although these would likely be seen by superpowers as military escalation of the status-quo.

2. Propulsion-less drone satellites. All propulsion-less designs use some form of sail which can be used to change the drone's orbit to match the debris before latching on and towing it to a new orbit. Once the debris is now in a decaying or graveyard orbit, the drone can detach and go after it's next target. All that is needed is time, power (readily accessible via solar power this close to the sun), and reaction wheels (which now we know what caused previous designs to fail like in the Kepler mission, can be built to last).

The most common form of sails would be solar sails, but there's also EDTs and magnetic sails.

[dredmorbius]

What about ablation and/or ablative thrust using lasers?

You'd need to fuel a laser platform, but it could target debris over a huge region. The goal would be to both reduce size and to gently nudge smaller debris to lower (and atmosphere-intersecting) orbits.

(As mentioned in another comment, linking: <https://en.wikipedia.org/wiki/Laser_broom>, here: <https://news.ycombinator.com/item?id=41051533>.)

[XorNot]

You don't need to put a laser in space to do this.

You build a ground based laser, and fire it at objects when they're approximately directly overhead. Pushing upwards on the object basically rotates it's orbit so one side of it will not be lower into the atmosphere.

[dredmorbius]

Which should simplify the problem several ways. Thanks.

[rzimmerman]

I'd argue that even propellent-less deorbit devices are a waste of time. The best answer is what we're doing now: rules about deorbit capability and orbit lifetime, as well as debris production. Even when there are failures, as long as they are a small enough percentage of the pie, debris won't accumulate faster than it clears.

Additionally, all the propellant-less solutions are low-thrust (or ground-based, which is another thing entirely). It's absolutely possible to orbit match, dock, and deorbit an object, but whatever low-thrust device you're using is going to deorbit as well. Maybe it's possible to launch a bunch of small devices like this to do cleanup, but it's not necessary or worthwhile.

This is a great example of a solution that sounds fun and interesting to a problem that's easy to understand at a surface-level. It gets attention and funding, but the real unsexy stuff (tracking, monitoring, collision avoidance) is where the money should go.

[panick21_]

The actual solution is reducing cost to orbit. That reduces propellant cost.

And more importantly, just having laws that require people to deorbit sats and force them to pay for deorbit if they fail to make something deorbit.

> 2. Propulsion-less drone satellites.

Nowhere near enough thrust for this.

[dredmorbius]

Absent regulation, decreasing cost-to-orbit has the more likely consequence of increasing overall launches, satellites, and hence, orbital flotsam.

The Jevons Paradox strikes again.

[panick21_]

There already is some regulation. But I agree that companies that launch should be responsable for deorbit.

[dredmorbius]

Depending on how far costs fall, one potential problem would be an equivalent of "flags of convenience" in sea-based shipping. Small countries with little or "favourable" (e.g., short-term profits) regulatory regimes could sustain at least some launch capability. Unless there's some way of reining in that activity, I see the problem manifesting to at least some degree.

Even now, getting launch-capable countries on board with restrictions is a likely problem. The US, EU, and Japan perhaps not so much, but of Russia, China, India, Pakistan (potentially), and North Korea, rather more plausibly.

[panick21_]

True but the solution for that is to punish those companies in the domestic market of the people who signed up.

There was US company that tried to launch on an Indian vehicle not following all the regulation and they got fucked hard.

Of course countries like Russia are simply not gone follow these rules anyway.

[spartanatreyu]

> > 2. Propulsion-less drone satellites.

> Nowhere near enough thrust for this.

Of course there is.

If solar sail probes can change their orbits over time (which they can), then they already have enough thrust. There's no static friction to overcome, so there isn't a minimum thrust that you need to reach.

As long as you can continue to apply thrust over time, then you have a solution. It doesn't matter if it takes 6 hours, 6 weeks or 6 months. Even a single probe moving the right piece of debris prevents tens of thousands of more pieces being generated. Imagine what three of them could do, or twenty...

[etrautmann]

Like a space superfund cleanup?

[naikrovek]

I would think that solar sails in such an environment would be as bad of an idea as walking through a thick hedgerow in a silk dress.

The dress would not survive unscathed, and neither would the solar sail.

[dredmorbius]

A solar sail isn't a pressure vessel, fuel tank, electronics bay, or other sensitive instrument. It can take considerable abuse before being substantially degraded, let alone failing.

Space debris impacting on a solar sail would all but certainly simply punch neat holes through it. Much as accumulating dust slowly degrades the light-gathering capability of a large reflector telescope, a modestly-perforated solar sail would lose a very small fraction of its effectiveness. But you could probably lose a heck of a lot of surface area before those effects became significant. Strength of the sail itself is probably a minimal concern, though a design with periodic reinforcing threads (themselves having a cost of increased mass) might be more than sufficient to address any strength compromise.

[naikrovek]

the solar sail would need to be incredibly large for a craft that can move to arbitrary locations in orbit for the purposes of de-orbiting satellites, which means it must have large sails so that both the de-orbiter and the de-orbitee can both be moved via sunlight alone, and achieve the required thrust vector in a reasonable amount of time (this de-orbiter must de-orbit many satellites, remember?)

the larger the sail is, the more likely it is to be affected by space debris at any given moment.

debris passing through a taught mylar solar shield will tear holes in the mylar which are the shape of the debris passing through. any sharp corners in the debris will leave a sharp corner in the hole, and those corners are going to become tears the next time something passes through nearby. the tiny holes become large holes pretty quickly.

other materials will behave differently of course, but i don't know of any solar sails at all, never mind ones made out of not-mylar.

[zamalek]

> The answer is exactly what governments and industry have been doing for at least two decades now.

To a degree. It helps to not blow shit up, in weapons tests or otherwise. These tests arise due to the weaponization of orbit (specifically), so the goal is really to not weaponize orbit - which governments have been doing the exact opposite of. All nations are deciding to tear Solomon's baby to shreds, instead of having shared custody.

If people want to weaponize space then, sure, go right ahead.

Unless the status quo drastically changes, i.e. bickering old fools being voted out (or removed via other means where voting is not possible/fair) throughout the world, Kessler syndrome is inevitable. I'd wager it happens sooner than runaway global warming.

[robotomir]

You can deorbit debris without physical contact, but you could argue the method results in a weapon: https://en.wikipedia.org/wiki/Laser_broom

[aeternum]

Anything that can deorbit debris can be used as an anti-satellite weapon almost by definition.

[jjk166]

It would be an incredibly ineffective weapon.

The way a laser broom works is imparting an extremely miniscule bit of momentum every time the object is in line of sight of the laser. Over time you lower its orbit enough for atmospheric drag to take over. For small debris, like baseball sized chunks of insulation, it takes months to deorbit the objects. For something the size of a satellite it would take an order of magnitude longer than the life expectancy of the satellite, and that's assuming it does no station-keeping.

Laser brooms are great because they can deorbit a lot of debris in parallel, which is great if your goal is to slowly clean up an orbit. They are pretty much the worst option for deorbiting a specific object quickly which is a hard requirement for any anti-satellite weapon.

[aeternum]

Makes sense but are there actually limits that prevent the scaling? IE instead of a single laser broom I build 50 near a solar/nuclear plant and use the surplus energy. Usually they all deorbit different objects but I could choose to aim them all at the same object.

I don't see much of a limit to scale. Satellites can only dissipate so much heat so you don't even have to deorbit it to be successful, you just need impart enough energy to overheat the satellite or disable key parts.

[jjk166]

A single broom for debris clearing is an immense project - likely $500 million to $1 billion to construct. It is basically a big observatory telescope with a gigantic high power laser - it is large, fragile, and completely immobile. That's for slowly cleaning up an orbit, to scale up to a weapons system you'd need a system equivalent to building tens of thousands of them.

You're not building a weapon system with surplus energy. Energy costs are actually pretty negligible - with 0.01% electric to kinetic efficiency it's only about 7 million dollars worth to bring down a 1000 kg satellite. The issue is the equipment. To deorbit that satellite in a year, you would need to on average be pumping 7.8 gigawatts of electricity into the system. If you put literally all of the US's electricity production into it, you could deorbit that single satellite in 2.4 days. And note that is if you could constantly keep the satellite in field of view, realistically only a small percentage of a satellite's orbit will be even under the best of circumstances, and many orbits won't be in view at all.

Yeah, there's nothing physically stopping someone from building such a system, but you're talking about putting basically all of a large nation state's GDP for decades into one weapon system that, in the best case scenario, is going to do an extremely minute amount of damage and realistically would be destroyed long before it could accomplish anything.

Disabling a satellite poses different technical challenges. For momentum transfer, so long as you're hitting the object you're good, to target critical systems would require far greater precision, and dumping heat faster than the satellite can dissipate it would require even higher instantaneous power. Remember the satellite is only very briefly in view. While this is almost certainly more feasible than a weapon that works by deorbiting, it is still very difficult. Laser weapons for disabling and destroying aircraft and airborne munitions, which is an inherently easier task, is an active field of research that many billions of dollars have been dumped into over the years, with no system yet being demonstrated as effective. Satellites are just faster moving, more distant targets for such systems.

ASAT missiles might be too mundane for the megalomaniac Bond villain, but they are an immensely more practical solution to the problem.

[alfiedotwtf]

At least talking about it will start the slow expansion of the Overton Window

[cuSetanta]

In-space contactless theories also exist: https://en.wikipedia.org/wiki/Ion-beam_shepherd

[mschuster91]

> These missions answer the question "could one dock with debris and deorbit it?" To which the answer is "obviously yes, but at enormous cost" and you don't need to spend 50M euros to prove it.

Well, it's not about debris, it's about the capability to sneak up to an enemy satellite and disrupt it without outright destroying it or making it look like a failure.

Shooting a satellite with a rocket ("ASAT") is easy enough - the US, China, Russia and India have proven that capability, and Israel likely has it as well. EMPs from nuclear blasts are another option. But either of that leaves undeniable traces (an EMP blast would likely fry a lot of stuff on the ground!) and the debris can endanger your own satellites as well, so you need something that acts in-space, preferably very difficult to observe from Earth. And something that can grab a dead satellite and drag it out of orbit can also just go and deposit a small explosive charge.

And at that point, 50 million euros are chump change to test that capability - if needed, replace the magnet/hook/whatever with a bomb and that's it.

[mgiampapa]

What's the X-37 cost again? $200M over 4 years of development?

[mandevil]

And make sure that even in the most unhappy cases, you vent your tanks! Vent vent vent vent! Tank explosions are where the really nasty debris numbers come from.

[rx_tx]

What do you do with the added deltaV from the venting? (not sure if significant) It could send the already-out of control rocket stage/object to a weirder or worse orbit, increasing the changes of collision.

[mandevil]

Ideally you have several vents perpendicular to the orbital path and open them at the same time, so the vectors cancel out. That's the happy case. If, because we are in the sad case, we can't get that, it's still better to have one piece of debris versus thousands.

[gpm]

Shouldn't the happy case be "we know the orientation of the stage so we can vent in the direction we are travelling to accelerate deorbiting"?

[Filligree]

The deltaV will out, one way or the other. Venting is better than having it completely uncontrolled.

[Evidlo]

Vent for a while, then use the reaction wheels to flip and vent in the opposite direction.

[naikrovek]

I’ll make sure I remind all of my satellite control room employee relatives. We all will, right?

[RecycledEle]

Active debris removal is almost at the level if being an experimental technology.

If it works, and if it gets cheaper as the technology matures, it might let use remove derelict satellites before they break up into smaller pieces.

It is usually easier to remove a few thousand big pieces of trash than to remove millions of small pieces of trash.

[Aeolun]

You just need a very big net.

[shakna]

Starlink have a number of debris problems, including pieces hitting the ground, so I wouldn't say that they're actually following through with their good practices.

[oskarkk]

I think that there were no reported cases of Starlink debris hitting the ground (they're designed to burn up in atmosphere). There was a case of SpaceX's Dragon parts hitting the ground lately, but that's a different thing. Also debris hitting the ground is a different issue than debris in orbit, with different problems to solve - you can have a satellite that has 0 chance to hit the ground, while being a serious hazard in space. It's in SpaceX best interest to not leave debris in orbit, because any debris from Starlink would be a threat to Starlink itself.

[wmf]

I thought the pieces hitting the ground are not from Starlink.

[try_the_bass]

Yeah, none of that is true.

Starlink doesn't have a debris problem thanks to the low orbit. Any debris generated deorbit on time-frames of a few months to a free years. Starlink also has 0 reported Earth debris strikes that I can find.

Where do you get this misinformation from?

[Log_out_]

Ground based laser evaporation to slow debree down?