So, the headlines probably sounds a bit alarming this week:
The Pentagon has said it is tracking a large Chinese rocket that is out of control and set to reenter Earth’s atmosphere this weekend, raising concerns about where its debris may make impact.
The Chinese Long March 5B rocket is expected to enter Earth’s atmosphere “around May 8,” according to a statement from Defense Department spokesperson Mike Howard, who said the US Space Command is tracking the rocket’s trajectory.
The rocket’s “exact entry point into the Earth’s atmosphere” can’t be pinpointed until within hours of reentry, Howard said, but the 18th Space Control Squadron will provide daily updates on the rocket’s location through the Space Track website. The Chinese rocket was used to launch part of their space station last week. While most space debris objects burn up in the atmosphere, the rocket’s size — 22 tons — has prompted concern that large parts could reenter and cause damage if they hit inhabited areas.
Let’s get this out of the way first: the danger posed by this event is small and the danger to you personally is basically zero. Most of the rocket body is going to burn up in the atmosphere. Some debris might reach Earth but the most likely place it will hit will be the ocean, simply because most of the Earth’s surface is ocean. Even if it doesn’t hit the ocean, there are large uninhabited areas where it could come down. When Skylab, which was much larger than the rocket stage, came down in a semi-controlled fashion, it scattered debris over Western Australia. No one was hurt although some of the pieces were quite large.
Last year, a similar Long March stage fell into the ocean, shortly after passing over New York and may have had some debris hit the Ivory Coast, damaging some buildings. So, it’s certainly possible that there could be some property damage done. And if we’re very unlucky, someone could get injured. Even a small piece moving at high speed could ruin someone’s day. But the odds are against it. And the idea that this could cause some kind of mass devastation is hysteria.
So why don’t we know when and where it will hit? Because projecting this kind of thing is tricky. While we can track the stage pretty accurately, we have no control over it. It is moving extremely fast and its interaction with the atmosphere depends on the rather unpredictable behavior of the atmosphere in fine grain and rather unpredictable orientation of the spacecraft when it hits. Re-entry patterns tend to be very dramatically shaped. Things fall to Earth very slowly until suddenly they fall very rapidly. The atmospheric drag grows exponentially, bringing them down suddenly and spectacularly. When projections are made for spacecraft re-entries in advance, the error bars tend to be years long. But even when you’re close to re-entry, it’s difficult to pin down the exact moment and thus the exact location. The spacecraft is moving five miles every second. Even if you could narrow the re-entry time down to ten minutes — and know how it’s going to plunge through the atmosphere as it disintegrates — that would only tell you what continent it might hit.
I have talked about the problem of space debris before. And rocket bodies are the object of biggest concern when it comes to space debris. There are, in fact, over 2000 spent rocket bodies in orbit around the Earth, about half from Russia and quarter from the US. But that isn’t quite what we’re talking about here. The Long March stage of the Chinese rocket isn’t going to be up there long, so it’s not really a space debris concern. And, in fact, most countries are not trying to mitigate the amount of space debris they put up on rocket launches.
No, what is getting the attention here is size. The Long March stage will be one of the largest objects to ever make an uncontrolled re-entry. Most heavy lifters drop their stages into the ocean soon after launch. The Long March leaves its core stage in low orbit, rather than a sub orbit, which means it will drop…somewhere. Hopefully not on someone but, you know, somewhere. And while we’re in a bit of glass house on this sort of thing, it’s still not acceptable. It would not be hard to modify the Long March series to not drop these things on us every year or so and hope everything works out OK.
So, while this is not something to panic about, it is something that we should be talking about. Because if you allow enough 20-ton Chinese rocket stages fall to Earth in an uncontrolled fashion, it is inevitable that something bad will happen. Not “destroy a city” bad but maybe “kill somebody” bad. And it seems very avoidable.
In the meantime, I would suggest you follow astronomer Jonathan McDowell who’s been doing some great commentary on the subject with graphs and videos.
(H/T: Em and fillyjonk who asked about this and gave me notion I should write about it).
I am old enough to remember Skylab and being worried about it as a kid.
I guess the bigger worry about ‘space junk’ is if you’re an astronaut – lots of stuff floating around out there now. But still, it seems like better planning could prevent even the VERY remote possibility that someone might have their car flattened by a chunk of this thingReport
Remember this story? Back in 2007, China blew up a satellite.
It was one of their own satellites so it wasn’t an act of war or anything.
I figured that it was just a display of “HEY LOOK AT WHAT WE CAN DO!” as a way of saying “knock it off” to all of the countries flying satellites over China and taking pictures.
But look at that last sentence of the story:
But this single event probably doubled the number of pieces of space junk at its altitude range.
I’m told that it’s possible to destroy a satellite in a less junky manner. Like, if the missile hit it from the other side, all of the debris would have been nudged to fall (however slowly) towards the earth. The way it was done just doubled the pieces of space junk.
All that to say: China has long treated debris as a tomorrow problem instead of a today one.Report
I actually mentioned that in the first draft of the post but decided to focus more narrowly on rocket stages. But yeah that was kinda evil of them.Report
I imagine that some future tech would be able to whizz up to space junk, capture it, then whizz up to the next piece until its belly is full and then hurl itself off to the sun (or, I suppose, to one of the convenient oceans if we want to do stuff with the pieces)… but, dang. Even optimistically, we’re a fur piece away from that.Report
Have you watched Space Sweepers on Netflix?
You should watch Space Sweepers on Netflix.Report
Movie plug aside, I’ve talked before, plenty of time, about tech designs and prototypes for de-orbiting junk.Report
We need a magnet. About the size of Texas. Just send it up there for some orbits at different altitudes and then bring it back down.
Easy-peasy.Report
Not actually a lot of magnetic materials up there…Report
We need a material magnetizer, then. Send it up there first.Report
You figure out how to magnetize Aluminum, Titanium, Carbon Fiber, and Gold, and we’ll be in business.
Failing that, figure out how to use the Lenz Effect.Report
so basically a cow magnet*, but for space?
(*for those unfamiliar: cow magnets)Report
Exactly.Report
Obligatory kurzgesagt video:
https://www.youtube.com/watch?v=yS1ibDImAYUReport
I want to take out that satellite, but I don’t want to be seen as doing so deliberately, so instead, I will take out this satellite, which is junk, or something I own, and I will do so such that the resulting debris cloud intercepts that satellite.
Obviously, such a tactic is no guarantee (orbital mechanics are both deceptively simple and devilishly tricky), but I wouldn’t be surprised to see someone try that.Report
The Air Force had a commercial about this!
I think that the plausible deniability would be attainable but I don’t know that it’d work against a fairly robust system that does stuff like keep track of space junk.
Like, you could do this against a barely first-world country that only barely got a satellite up there, but I can’t imagine this working against, say, a Comcast satellite.Report
Unless the satellite can alter it’s orbit, it’ll take out the Comcast satellite (assuming the debris field was on track). Comcast may find a way to sue you for the cost…Report
Now I’m googling types of orbits.
I’m pretty sure the geostationary ones can alter their orbits (they aren’t stationary as much as doing a figure 8 all day, every day) and it’s the ones in LEO or MEO that just orbit around over and over and over again.
And LEO/MEO orbits strike me as being a lot more likely to be poorly modeled in the computer than modeled well enough to set up that chain reaction.
But, hey. China did figure out how to hit something the size of a refrigerator with a missile. Maybe they’d be able to line up one hell of a billiards shot.Report
Geostationary is far enough out no is going to ‘accidentally’ plug one.
Altering an orbit requires reaction mass. Most satellites have some. They use up some doing final positioning, and keep a bit in reserve for emergencies and station keeping, but it’s not a lot. A lot of satellites ‘die’ not because of failure, but because they ran out of reaction mass and can no longer perform station keeping (orientation is often done with flywheels that are spun up or down to turn a satellite, and if a flywheel spins too far down, reaction mass can be spent to spin it back up).
Dodging a debris cloud could force a satellite to expend too much reaction mass, and it either can no longer return to station, thus killing it by making it useless, or it so drastically shortens is useful life that it is effectively dead, unless it can be refueled.
I’m not up on the latest satellite designs, but as it gets cheaper to send mass to orbit, I would not be surprised to see satellites designed with a refueling capability.Report
I believe current end-of-life planning for satellites in geostationary orbit is to carry enough propellant that they can reposition into a higher orbit, opening up their slot. Geostationary orbit slots are a relatively scarce commodity.Report
I’ve done work on 2-stage designs, that necessarily have very large stages, and you can design things such that the stage breaks up when discarded, or you have the stage end lower down in the atmosphere. But such decisions involves costs and trade-offs and clearly China just don’t care.
If Karma has any say, and debris large enough should land in China.Report
Yeah, this is more your area of expertise so glad you weighed in. Feel free to write a post if you have additional insights!Report
Nothing worth writing a post about. China can’t copy the Falcon 9 yet, so they can’t recover the 1st stage like SpaceX does. Putting self-destruct devices on rockets is a great way to get rockets that perform unscheduled self-destruction, and rockets are prone to that already.
Stages separate according to the launch trajectory, so you can’t just ask them to separate lower in the atmosphere, since that involves re-working the trajectory, and possibly re-designing the rocket itself.
What you can do it ask that stages over a certain size have separation links so the stage breaks into smaller pieces. It adds additional structure (& thus weight, and cost, and forces one to re-work the rocket equation), but we know how to do it quite well.
China just didn’t want to, and felt that rolling the dice on re-entry debris was acceptable.
And honestly, the odds are in their favor.Report
If karma has any say the debris will land somewhere outside of China that is both fragile and belongs to someone influential, big and noisy. If it lands in China then it will “not have landed in China” or “Landed harmlessly just as was intended *Chinese national anthem plays*” regardless of what damage it actually did.
No. What China would hate is if it, say, landed on a major Saudi oil refinery or depot and wrecked it, or if it blew through a sensitive American piece of infrastructure or flattened the EU parliament building (mmm actually that might help China’s image in the EU). Obviously it would be even worse, geopolitically if people died from it landing but I wouldn’t wish that on anyone.Report
Off topic, I saw this yesterday. It’s a floating wind turbine. It sits on 3 buoys, so it’s mounted on a tripod, in a leaning configuration, so the turbine blades hang off one side.
Advantages: More stable than a single pillar. The supports can be smaller, and more aerodynamic, which allows for the blades to be a follower orientation (the nacelle points upwind of the blades), so when the blades bend from the force of the wind, you don’t have to worry about blade tips striking the supports. That, coupled with the tripod design, means you can anchor it at the upwind point of the tripod and just let the whole thing weathervane with the wind, saving costs on expensive wind-following technology. And anchors are cheaper than sea floor foundations.
Cons: You gotta keep an eye on the anchor and power cable, make sure excessive weathervaning doesn’t twist them beyond what they can take. Heavy seas are also a concern.
It’s an interesting approach to the problems of offshore wind power.Report
Something like 2/3 of the Earth is ocean, right? Plus some other percentage which is non-ocean water. Then you have uninhabited areas. Taken together, what percentage of Earth could be considered uninhabitated? Not just like, there’s no houses there but like, there ain’t even a real chance of people there. I’d call parks and farmland inhabitated.Report
http://www.curiousmeerkat.co.uk/questions/much-land-earth-inhabited/Report
Speaking of rockets, I can haz jetpack pleez?
https://www.youtube.com/watch?v=suHOLFhbwsMReport
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