Decluttering low-Earth orbit: It's time to tidy up space
economist.com
economist.com
https://en.wikipedia.org/wiki/Australis-OSCAR_5
http://centralblue.williamsfoundation.org.au/oscar-5-the-fir...
http://stuffin.space/?intldes=1998-067NT
I'd never heard of the West Ford Needles:
https://space.skyrocket.de/doc_sdat/westford.htm
I wonder how the Lemur 2 satellites are named:
CO2 / plastic.
When the society is mature enough to clean the mess created ?
P.S. Sorry for offtopic rant
It is worthy of note from https://spacenews.com/upper-stages-top-list-of-most-dangerou... that in a list of the 50 most concerning objects in orbit, 78% are rocket bodies, and 80% were launched before 2000 when various mitigation strategies for space junk began to be improved.
There is therefore a Pareto principle at work here. We are tracking over 25,000 objects, but only a few of them contribute most of the risk, and we aren't adding as much to the risk as the number of launches would make you think.
It's only about 50% larger (1+1400/6371)^2 = 1.49
Edit: I just looked up the formula for orbital period and it turns out period is proportional to radius^(3/2) (See: https://en.m.wikipedia.org/wiki/Orbital_period)
Almost everything we do carries a small but non-zero risk of something which, if you stretched it over a hundred thousand years, would almost certainly be realized.
On the other hand, the average damage from a collision in space within 100,000 years is also pretty small.
Of course, I am assuming a few things, like their orbits don't decay, they aren't exactly synchronized (i.e. they drift, and will eventually cross every point on the other's), but also that the uneven gravity of Earth doesn't corral them into narrower orbital paths (which it absolutely will, increasing the chances of collision).
That's for only two satellites. There are literally thousands. And when they smash apart, they can each generate hundreds more killer-sized fragments.
Kessler syndrome is a very real possibility on a long timescale.
We should be more careful the junk we put in space.
Phew, 23 days earlier your father would have had to code all timestamps in negative.
Joke apart, which OS did such satellites run? Unix? Probably not, since timestamps only started in 1970. Just "C"? Even today, how do you register time on satellites? With Unix timestamps (a long since 1970-01-01)? Can they synchronize based on objective points (stars or Earth position to the sun) or are satellites always resynchronized from Earth signals?
> In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000 (equivalent to $165,000 in 2019), with an input-output device such as a teleprinter and at least four thousand words of memory, that is capable of running programs in a higher level language, such as Fortran or BASIC.
I think it’s safe to say that the biggest issue with launching computers running UNIX into space in 1970 probably was not the lack of a standardized time stamp :-)
Star trackers give you location in orbit and orientation of your satellite. I don't believe you can get absolute time from them, especially given that Earth time is somewhat decoupled from Earth's orbital dynamics.
What you can do is get time using GPS, like you would on the ground. Not sure if that's possible for higher orbits, but definitely for low orbits. There have also been some experiments with laser-based synchronization (a PPS-style signal, I believe?) and you could get a coarse sync with a regular old radio uplink.
IIRC there have been some proposals to use Pulsar signals on satellites/probes not just for time synchronization but more importantly navigation. Not sure if it's actually in production use yet.
Wow! I heard of this technique recently but I didn't realize it had already been deployed so long ago.
https://astronomy.com/magazine/ask-astro/2014/07/space-debri...
The real problem isn't that space is getting full of our junk, but that our junk is in a very narrow band of orbits that we use for very specific missions: Sun synchronous polar orbits used by imaging satellites. Look at how these orbits all cross paths at the poles. That's the danger zone. While the military cares deeply about these orbits, civilian infrastructure in space (geosynchronous communications sats, GPS etc) are well beyond any real danger. Or, at least they are in orbits where danger from natural debris is vastly greater than from space junk.
> Or, at least they are in orbits where danger from natural debris is vastly greater than from space junk.
Are you sure? A quick online search reveals only two satellites appear to have been destroyed -- an Iridium satellite was destroyed in 2009 when it was hit by a junked Russian satellite, while in 1993 the European satellite Olympus was destroyed by a meteor.
So it would seem that so far, natural debris and space junk are tied 1-1. Why do you think natural debris is that much more of a risk?
There are plenty of sats that have just stopped working, even broken apart, for unknown reasons. Telling the difference between a defect and a meteor impact is mostly impossible. Lots of spacecraft have just stopped working for unknown reasons. Until we start inspecting every failed satellite, as we do aircraft, we won't really know.
And note where the 2009 collision happened: over the arctic. This was one polar orbit colliding with a near-polar orbit, right in the danger zone I mentioned above.
In terms of probability with debris impacts on satellites the common effect is a slight drop in power output from the solar panels [0].
Keep in mind stuff in orbit is pummeled by micrometeoroids pretty regularly. These are literally dust size grains of material in orbit. They face pretty constant abrasion yet remain fully functional.
[0] https://www.space.com/20925-space-station-bullet-hole-photo....
Cosmic dust, on the other hand, is just dust. It can be abrasive but satellites are designed to handle it, as is the ISS. It may have high velocity but the fact that its mass is miniscule means it can be shielded against.
What's the significance of these orbits?
> This means that, for most of the year, PROBA2 will have a full-time view of the sun, and will not experience eclipses of the sun behind the earth. However, because the orbit does not follow the terminator exactly, PROBA2 will experience brief periods of several weeks when eclipses of the sun by the earth do occur, specifically around December each year. During approximately 80 days (from November until January), visible eclipses occur every orbit with a duration ranging from a few minutes in November up to a maximum of 18 minutes and back to 0.
Thanks for sharing this use use case too though, pretty neat.
Your comment epitomises the golden rule of Hacker News, that you should post "anything that gratifies one's intellectual curiosity".
Nonetheless, it is very dated. Fusion power looks a lot worse today than it did back in 2003. The fusion-powered space Jovian exploration ship would be right at home in today's sci-fi (just as much the future today as then), but He-3 as a reason to go into space as been eviscerated. People who still (unrealistically) hope for a fusion game-changer are more often touting proton-Boron, and He-3 doesn't even fundamentally change problems of ignition conditions and radiation, it just mitigates it.
They also didn't do much to predict radical reduction in launch costs. In the PlanetES world, it still felt very expensive to get into space. They didn't go unless they had a corporate sponsor or were filthy rich. I don't even remember anything that hinted at booster re-usability, which is now (astonishingly) reality.
There's also the obvious fact that sending people to do trash pickup was always more Hollywood than reality. They knew that then.
They also have regular transcontinental flights going through space, even though its IIRC not clear if its sub orbital ballistic trajectories or FOBS like partial orbit ones.
Still, many would-be hard SF films get this completely wrong - huge space stations and/or interplanetary spaceships yet they launch it all on rather dated looking expandable boosters!
Already The Martian it's pushing is pushing it with using basically improved EELVs (launched by ULA, none the less!) yet having hundreds if not thousands of tons of equipment and propelant in place.
Interstellar or Ad Astra is bad shit insane - dinky ELVs and multiple interplanetary colonization attempts and humongous space ship in the former and KFC & artillery fireballs on the Moon in the former. And Ad Astra even has booster stages being dropped when launching from Mars because hey, why not waste even more resources!
https://en.m.wikipedia.org/wiki/Rocket_Girls - basically space flight marketing for highschoolers created in cooperation with JAXA - has a pretty good description of using a biosuit
https://en.m.wikipedia.org/wiki/Space_Brothers_(manga) - a near future "so you want to be an astronaut, eh? " story - very realistic description of what you need to do before actually going to space (38 volumes/99 anime episodes)
https://en.m.wikipedia.org/wiki/Starship_Operators - a space opera that has quite minimal super science and a lot of hard physics - lasers vs overheating, detection/stealth in space (and the lack thereof), signal propagation issues, how to turn big ships quickly enough to use thrusters/fire axial weapons, using neutrino detectors to spot enemy warships based on neutrinos from their nuclear reactors
Various UC Gundam series - pretty accurate description of O'Neil Island 3 space colonies, mass drivers, orbital infrastructure in general - zero g only ships & stations
(You can skip the first 30 seconds of intro)
https://www.predictions-podcast.com/2020/03/14/space-debris-...
btw: The article is behind a paywall :(
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv...
https://www.businessinsider.in/us-russia-china-and-india-sta...
Meanwhile, India created about as much space junk in a day as the US creates in 1-2 years. That's despite claiming that the the test was in an orbit that wouldn't leave any longterm debris.
I do find it annoying that space is usually jingoistic bullshit involving flags and rousing speeches instead of actual science. I'm glad ESA never went that way.
https://www.gapminder.org/tools/#$state$entities$show$countr...
I also agree with your point that sometimes space achievements are used for jingoistic purposes. But if you see the bigger picture (which most people don't sadly) you realize that it is a net positive overall for science and humanity. The jingoistic aspect is just a consequence of political reality.
I read about it, and it seems a little counter-intuitive for me. I would expect that in a collision in space, some of the kinetic energy would be used in internal structural changes, and not all converted to the resulting motion.
Am I wrong here? If not, does it still preserve enough kinetic energy after collision to promote this chain reaction? And how long until lower space ring is actually unusable?
Edit: Not only that, but even if 90% of momentum was lost - it only takes another satellite going in the opposite direction to supply all the energy. Here's what 2 ounces of plastic does at 15,000mph to a block of aluminium. https://imgur.com/gallery/8NwAhgK
> it only takes another satellite going in the opposite direction to supply all the energy
I see, indeed the next collision will supply a lot of external momentum.
At those speeds, everything is "flexible" in the sense that even metal just flows in a fluid-like manner (see picture linked in the comment).
Also, the material would have to somehow convert the energy of an entire car crashing into it at full speed. Except the car is only an inch wide.
However, the Kessler syndrome is not about the total mass of debris in orbit, but the number of individual debris. So while before the collision we had 2 nicely aggregated debris, after the collision you will have thousands of small ones.
The small ones will tend to deorbit faster on average, because of the loss of energy mentioned above and also because their aggregated surface area increases, but you still have more debris. And when we are talking about multiple decades/centuries of lifetime, these debris will collide with other satellites, creating a positive feedback loop, increasing the numbers of debris exponentially, at least initially.
Obviously this is just the beginning of the process, which will end up with a maximum number of debris and then a decrease towards zero, but that timeline is extremely long and therefore not really relevant to us.
The ISS has regular enough operations required to dodge debris detected approaching for a near miss in space that I think it's definitely a concern for future operations.
Consider as well that stuff in orbit is going ~25,000km/h or more and at that speed even a small bolt would decimate a spacecraft on impact.
Are the orbits in opposing directions? If not, then the 25k number isn’t meaningful right? Their relative velocity is what matters
That’s interesting about the ISS I hadn’t heard of that as a regular thing.
So it is a thing, but I wouldn’t call < 1 per year regular
The problem is not just about satellites, but random debris flying unpredictably on orbit. When there starts to be a critical number, the odds to hit something start to raise in the "very possible" territory.
The Wikipedia page for Kessler Syndrome even state that, currently, one satellite is destroyed every year by junk. That's only going to increase if nothing is done.
The problem is if you want to stay in an orbit alongside the junk.
The dynamics of orbital mechanics are interesting, to say the least, but it in no way maps to the surface of some sphere.
A somewhat useful analogy is to imagine two circular racetracks, that intersect with each other in two spots. Each racetrack is like an 'orbit', and racecars going around them are satellites.
Make the racetracks really big, and put a car on each track. Have the cars drive around non-stop forever. The chance of them hitting each other on any lap is extremely small. However, if you let the cars go for a long time, and one of them completes a lap a little bit faster than the other, the times that they both cross the intersection will slowly get closer and closer together. Eventually, they will crash. If you put more cars on the track, the chance of two of them colliding increases. If everyone time they crash they create lots of baby cars, well you get Kessler Syndrome.
This is only a problem for these racetracks because they touch. We protect against this in the orbital world by keeping satellites in different orbits, that don't cross. The problem is that the orbits can shift over time due to gravitaional inconsitencies, and solar flares causing the atmosphere to bleed off into space, and the moon, etc. With lots of long lived satellites in low earth orbit, the chance for a crash increases. But even if we do get lots of baby satellites the other orbits farther out will remain useable (like geostationary orbits), you just have to be a little careful when crossing the low earth orbits on the way out.
Insurance is a fascinating industry ripe for digital innovation. However, sadly, the deals are primarily written based on the quality of your relationships.
For the purposes of deorbiting junk it may be sufficient to just impart some delta-v, but you neither want that to be uncontrolled collisions sending stuff into even more erratic orbits, nor would you want to risk generating even more tiny pieces.
There is almost certainly a better material to use as well, but I don't think either of these practical concerns invalidates the idea.
Of course, big enough Space Sponges to make a practical difference would be very visible to the naked eye.
The problem in the end is launch costs. Yes, we're getting better, but that doesn't mean we can shoot up a "visible to the naked eye"-sized impactor. Not to mention what difficulties an object of that size would bring for non-garbage that also occupies those orbits.
Lastly, I have no idea how much research there has been in containing the fragmentation of hypervelocity impacts. But presumably it would be an important part of the mission to not generate more garbage.
Even if launching costs ever makes this feasible, any Space Sponge big enough to be efficient would be a big collision problem in itself.
But passive objects are only as likely to provide value as the ratio of the number of the total volume of the sacrificial objects to the total volume of assets, so you'd want a bunch of them.
Since the debris of interest is really just the material traveling in orbit, a cylinder might be more efficient, if some primitive attitude control could be included efficiently.
The exception to this would be if the object were in an elliptical orbit, which would allow for contact to be made with the scaffold at its perigee, which be impossibly rare.
Useful in both communication and in denying the space to other classes of satellites.
Is this actually an issue? The earth has a surface area of 500M km^2 so if want 0.5km between each satellite you can fit 500M satellites at one orbit level. A few thousand spacex satellites is a drop in the bucket.
All great circles on a sphere will intersect in two places, which assures a collision if you have satellites in them both (without active avoidance). So you have to separate the great circles on to different sized spheres, or add a little eccentricity to make sure the rings don't touch.
There is still a lot of space, but comparing to the size of the surface of the earth is not very informative when dealing with orbital dynamics.
It's not useful to make a simplifying assumption, if the solution to the problem is to reverse the resulting simplifications.
What I was trying to do was show how we move from the mental model of dots on a balloon (there is so much space on the balloon! the dots are tiny!) to rings around a ball. In order to make sure the dots don't intersect with each other simply spread them out appropriately. In order to make sure the rings don't intersect each other make some of them slightly bigger, or stretch them a bit.
The resulting orbits are still, approximately, great circles on the same sphere - just perturbed a bit.
https://medium.com/@leolabs_space/the-iras-ggse-4-close-appr...
https://spacenews.com/esa-spacecraft-dodges-potential-collis...
Add in thousands of new satellites from various race-to-the-bottom move-fast-and-break-things companies and Kessler syndrome seems less hypothetical and more inevitable.
"a bug in our on-call paging system prevented the Starlink operator from seeing the follow on correspondence on this probability increase"
Imagine if the other satellite operator had been similarly negligent, or if the satellite had been defunct. It will be somewhat ironic if a Musk-led operation grounds humanity on Earth for a decade or more.
A nice newsletter about space stuff (I have no affiliation, just a fan)
Garrett Hardin's article which created and promoted the "tragedy of the commons" doesn't describe historical "commons" at all, which were all managed over extended periods of time by complex rules and social norms. The "tragedies" happened primarily when capitalism emerged and demanded an end to the historical management of commons, allowing the interests of capital to destroy them.
Space might actually be the first really good example of "the tragedy of the commons" inasmuch as it was a new, globally accessible (i.e. not geographically determined) resource which began to be used without any establishment of the usual norms and rules that accompanied historical commons. Something similar presumably happened with the oceans, but their physical nature (i.e. stuff sinks, and stuff moves) hasn't created an issue in the same way that is now happening in orbit.
> It's ok to post stories from sites with paywalls that have workarounds.
> In comments, it's ok to ask how to read an article and to help other users do so. But please don't post complaints about paywalls. Those are off topic.
I can read the article fine, so I presume there's some level of free access before you trigger the paywall.