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from the step-aside-please-coming-through dept.
Arthur T Knackerbracket has found the following story:
LeoLabs estimated that the satellites could pass within 15-30m of one another. Neither satellite could be controlled or moved. All we could do was watch whatever unfolded above us.
Collisions in space can be disastrous and can send high-speed debris in all directions. This endangers other satellites, future launches, and especially crewed space missions.
As a point of reference, NASA often moves the International Space Station when the risk of collision is just one in 100,000. Last year the European Space Agency moved one of its satellites when the likelihood of collision with a SpaceX satellite was estimated at one in 50,000. However, this increased to one in 1,000 when the US Air Force, which maintains perhaps the most comprehensive catalog of satellites, provided more detailed information.
Following LeoLabs' warning, other organizations such as the Aerospace Corporation began to provide similarly worrying predictions. In contrast, calculations based on publicly available data were far more optimistic. Neither the US Air Force nor NASA issued any warning.
This was notable, as the United States had a role in the launch of both satellites involved in the near-miss. The first is the Infrared Astronomical Satellite (IRAS), a large space telescope weighing around a tonne and launched in 1983. It successfully completed its mission later that year and has floated dormant ever since.
The second satellite has a slightly more intriguing story. Known as GGSE-4, it is a formerly secret government satellite launched in 1967. It was part of a much larger project to capture radar emissions from the Soviet Union. This particular satellite also contained an experiment to explore ways to stabilize satellites using gravity.
Weighing in at 83kg, it is much smaller than IRAS, but it has a very unusual and unfortunate shape. It has an 18m protruding arm with a weight on the end, thus making it a much larger target.
Almost 24 hours later, LeoLabs tweeted again. It downgraded the chance of a collision to one in 1,000, and revised the predicted passing distance between the satellites to 13-87m. Although still closer than usual, this was a decidedly smaller risk. But less than 15 hours after that, the company tweeted yet again, raising the probability of collision back to one in 100, and then to a very alarming one in 20 after learning about the shape of GGSE-4.
The good news is that the two satellites appear to have missed one another. Although there were a handful of eyewitness accounts of the IRAS satellite appearing to pass unharmed through the predicted point of impact, it can still take a few hours for scientists to confirm that a collision did not take place. LeoLabs has since confirmed it has not detected any new space debris.
-- submitted from IRC
(Score: 2) by ikanreed on Friday January 31 2020, @09:35PM (13 children)
Relatively minor. I haven't looked at the actual papers on it, nor done the math myself, but I don't think you lose that much energy from the atmosphere if your lasers are in the right frequency, and though it's counter-intuitive, other than that, the actual quantity of energy to de-orbit is precisely equal to the change in kinetic energy of the satellite in question from its current orbit to one that intersects the atmosphere.
Which is doable with regular ass grid energy. You don't need super lasers like you do with a laser thermal rocket.
(Score: 2) by JoeMerchant on Friday January 31 2020, @09:40PM (12 children)
How well does this work on tumblers? A lot of the big nasty debris isn't exactly holding steady attitude.
Also, the perception of building a "space laser facility" is going to be hard to get around...
🌻🌻 [google.com]
(Score: 4, Interesting) by ikanreed on Friday January 31 2020, @09:50PM (11 children)
1. In space, objects in motion remain in motion, on exactly the same course unless acted on by another force. It's exactly like those "imagine this is a frictionless vacuum" problems they teach in physics 101, except it's actually a frictionless vacuum. There's not an inch of wobble to the center of mass. If there was enough atmosphere for that to be a problem, it would already be deorbited. No extra work necessary.
2. You know we've built literally dozens of facilities that do nothing but launch wads of radioactive metal into space, only for them to fall back down on inhabited areas, and explode in such a way as to cause a runaway nuclear chain reaction that kills millions and drops radioactive debris across hundreds of square miles, right?
And that being able to do that was, in fact, half the motivation of developing space technology in the first place?
Seems like we can eat the negative PR of a few thousand slightly overpowered laser pointers.
(Score: 2) by JoeMerchant on Friday January 31 2020, @10:29PM (10 children)
My point is: if this is the same propulsion theory as painting half an asteroid white and the other half black, that only gives a net push if the asteroid isn't tumbling such that the white and black alternate along the direction of travel...
Your ground based laser array is already limited to illuminating the underside of the objects, up to a sideways shot through a lot of atmosphere to hit them along their direction of travel... and thanks for sticking with me this long, if the laser heating doesn't cause instant delta-v, but rather heats up what it illuminates and then that re-radiation of heat energy is the primary source of delta-v, then that re-radiation surface will tumble with the object, smearing the delta-v all over the place and mostly self-cancelling. As you say, we're going to be restricted in our choice of wavelengths to efficiently pass laser energy through the atmosphere...
Yes, but that's "military necessity" and keeps little Johnny from being drafted into the front lines. NASA geeks playing with powerful space lasers are liable to go rogue and have fun with them, or turn evil and take the world hostage or something. Remember: the voting public is made up of ALL kinds of people.
🌻🌻 [google.com]
(Score: 3, Touché) by ikanreed on Friday January 31 2020, @10:50PM
It's not the same as that theory, because you're always shooting from the ground towards the object when it's approaching you. There's no way that doesn't slow it down.
(Score: 2) by deimtee on Saturday February 01 2020, @02:17AM (5 children)
The most efficient ones I've read about use pulsed lasers and the thrust is caused by ablating some of the surface. Tumbling shouldn't make much difference. I do wonder about blasting particles off the front though. It seems like you could be trading a big lump for a lot of little ones. Action-reaction means that the big lump de-orbits, but the ablated stuff goes into a higher orbit.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by JoeMerchant on Saturday February 01 2020, @03:25AM (4 children)
O.K. - that makes better sense, but, yikes! Trading a big lump that you can track with radar for thousands of micrometeorites that you can't? Talk about intentional holes in the living quarters!
🌻🌻 [google.com]
(Score: 2) by deimtee on Saturday February 01 2020, @04:11AM (3 children)
I think the theory is you ablate it all the way to a gas. At that small and hot the particles are likely to be charged too, which means they'll interact with the magnetic field. Stuff that small will either hit the atmosphere or blow away into deep space, it won't be in stable orbits for long. Even pressure from sunlight is going to move it.
Detractors say that you will also cause spalling, and those chips will be dangerous.
The Saturn 5 stage 1 masses about 2500 tonnes and has enough thrust to just lift 3500 tonnes. I think we should build some more, strap a 1000 tonne tank of argon gas on top, loft it straight up (no orbital motion) to about 1000km and let the gas out. It will expand into a huge low pressure cloud and fall slowly back to earth. Anything that passes through it will be slowed slightly and drop into a lower orbit. Big stuff won't move much, and you would time it to avoid delicate stuff, but all the little shit will lose some speed, and drop into a lower orbit to burn up much sooner.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by JoeMerchant on Saturday February 01 2020, @04:28AM (2 children)
I'm with the detractors on this one, no matter how energetic the beam is those high energy pulses are going to make some larger things break up and fly off. My first thought was a lot more comforting: warm it up and let it re-radiate the energy off the surface - much less explodey stuff that way.
Building a new Saturn 5 would be like building a new Bugatti Royale - sure, we can do it, but it will be fabulously expensive and at the end of the project you'll have a brand new horribly outdated thing. Still a BFR or whatever is in the current heavy lift production pipe should be good. Straight up is easy to explain, but I'm sure there are all kinds of rocket scientists just itching to prove how clever they are and how much more efficient a particular trajectory of release would be at aerobrake de-orbiting the most junk for the least money.
I still like the idea of a video game kind of solution with low cost orbital robots that go forth, match orbits with junk, latch on and do kamakazi deorbit burns - it speaks to the control freak in me.
The first satellite I ever spotted by chance turned out to be a tumbling mid-stage of a big Russian thing from the 60's - there are so many things like that up there.
🌻🌻 [google.com]
(Score: 2) by deimtee on Saturday February 01 2020, @04:55AM (1 child)
Not the whole thing, just stage 1, but yeah. You could still do it with whatever the current rockets are. Calculating the best bang for the buck is not something I'm going to bother with unless Elon puts me in charge of it. :)
The problem with this is it's great for de-orbiting the big stuff, but the big stuff isn't the problem. It's tracked and there aren't really that many of them. It's all the little stuff - a 10mm nut travelling at 14 km/s is going to ruin your day just as much as a 100kg satellite.
The earliest satellite I remember seeing was in the 70's. It was bright enough to see in daylight, and took about 10 minutes to go from straight up to beyond the horizon. Don't know what it was, might have been skylab.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 2) by JoeMerchant on Saturday February 01 2020, @05:17PM
My wife is sort of into Spot The Station [nasa.gov] - it usually works for us as advertised, unless there's too much cloud cover.
🌻🌻 [google.com]
(Score: 2) by edIII on Saturday February 01 2020, @09:21AM (2 children)
What about not making this a ground based solution? Isn't there enough energy in solar to power lasers? It seems that low power lasers would work just as well over time, and out in space we don't have the atmosphere restricting our choices of wavelengths. Thinking about it, would it not be possible to create a large enough array of mirrors to then focus the sunlight onto the debris?
Then of course, we could put a much more powerful array of lasers on the moon instead :)
Technically, lunchtime is at any moment. It's just a wave function.
(Score: 3, Funny) by JoeMerchant on Saturday February 01 2020, @05:20PM (1 child)
Now you're talkin! [youtu.be]
🌻🌻 [google.com]
(Score: 1) by RandomFactor on Saturday February 01 2020, @07:46PM
That's.... https://www.youtube.com/watch?v=8Nho44lGVV8 [youtube.com]
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