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The waste, waste majority of sats never turn into space debris. Every single sat that launches today in the West has a deorbit planned. The only sat that turn i
by panick21_ 3y ago
The waste, waste majority of sats never turn into space debris. Every single sat that launches today in the West has a deorbit planned. The only sat that turn into space debris will be those that brake unexpectitly and totally unrecoverable.
And the Starlink sats are so low that they dont really turn very meaningful debris ever.
And in general, yes LEO can handle millions of sats.
We have like 150k cars in a single tiny country on earth right now.
- wyldfire 3y agoFreudian slip.
- 3cats-in-a-coat 3y agoCars don’t constantly move thousands miles an hour uncontrollably
- simple-thoughts 3y agoCars also don’t move in easily predicted patterns for decades without turning from their predetermined path.
- mabbo 3y agoThey sort of do though. Cars, for the most part, follow the road and the direction they're already going. They (usually) signal if they're about to make changes. And to be safe, we've built an arrangement that they only travel on these specific paths at specific speeds, modifying their speed to match the other cars they might hit. The challenge with satellites is that steering is hard and very limited. And they don't have brakes they can slam to come to a stop if they need to suddenly avoid a collision.
- panick21_ 3y agoIt is well known that potential points of conflict are a huge issue. That's why a round about is safer then intersection. > And to be safe Tell that to the 40k people killed and the millions hurt by cars in the US alone. Cars constantly turn and intersect routes with other cars without any planning, even if perfectly handled and most of time they are not. > The challenge with satellites is that steering is hard and very limited. And they don't have brakes they can slam to come to a stop if they need to suddenly avoid a collision. They don't need to break, they just need to know the position of speed of other objects and correct position ahead of time. The only reason why this is even a program at all is because only the US has even minimally invested in monitoring. If each nation just did the same our accuracy would be far, far higher and things would be way better. So, as of now, we have minimally invested in solving this problem and it isn't a big issue. Slightly more investment (that is justified if we 10-100-1000x the amount of sats) is required eventually. But compared to what it takes to make cars not crash into each other its nothing. (Unless its like US infrastructure design that seems to want to make cars crash into things, but I hope in Space we can avoid that)
- starbase 3y agoCool thing about satellites is if you're on the same path, you must also be going the same speed. Collision avoidance in LEO is quite elegant. When two satellites are predicted to pass uncomfortably close to one another, one satellite will fire its station keeping thrusters to raise its orbit above the other. No brakes or swerving needed, just a slight push well ahead of time. Starlink sats do this over 1000 times per week. Even better, energy used for avoidance reduces energy needed for station keeping on a 1:1 basis. Avoidance maneuvers are effectively free.
- j4ah4n 3y agoWhat powers those thrusters? Never really thought about it.
- panick21_ 3y agoThey are powered by solar electricity that is saved in batteries. But to actually move you need something to throw out. That can be many things, anything from normal water, metal or noble gases. Starlink initially used Krypton for its thrusters. But they have now switched to Argon since its incredibly cheap and available. Xenon for a long time was the standard, but its to expensive and rare. Some sats also have chemical power, often a Hypergolic propellant, like dinitrogen tetroxide plus hydrazine. Specially for larger sats this is the case. - https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster -
- 3cats-in-a-coat 3y agoThey do. We call those paths roads.
- lmm 3y agoAnd cars never take a sudden unpredictable turn off the road?
- 3cats-in-a-coat 3y agoThey do. Now make them move ten times faster than an airplane. What happens? Mind you I'm not the one who came up with the TERRIBLE analogy with cars. Millions of people a year die in car accidents, and this was somehow the example that's supposed to convince us that if "cars are safe" then satellites travelling 100x faster than a car over our heads (and 10x faster than an airplane) are also safe. The whole construct betrays extremely sketchy thought process.
- deleted 3y ago[deleted]
- yreg 3y agoCars move much more uncontrollably / unpredictably than sats.
- Jeff_Brown 3y ago> the Starlink sats are so low that they dont really turn very meaningful debris ever. Is that right? Scientific American seemed to think it could be a problem in 2019[1]. Space.com says Starlink satellites orbit at an altitude of about 342 miles (550 kilometers)[2]. And the Wikipedia article on Kessler Syndrome[3] (which is a chain reaction of satellite debris) mentions an incident at 555km that was problematic: "In 1985, the first anti-satellite (ASAT) missile was used in the destruction of a satellite. The American 1985 ASM-135 ASAT test was carried out, in which the Solwind P78-1 satellite flying at an altitude of 555 kilometres was struck by the 14-kilogram payload at a velocity of 24,000 kilometres per hour (15,000 mph; 6.7 km/s). When NASA learned of U.S. Air Force plans for the Solwind ASAT test, they modeled the effects of the test and determined that debris produced by the collision would still be in orbit late into the 1990s. It would force NASA to enhance debris shielding for its planned space station." [1] https://www.scientificamerican.com/article/spacexs-starlink-could-cause-cascades-of-space-junk/ https://www.scientificamerican.com/article/spacexs-starlink-... [2] https://www.space.com/spacex-starlink-satellites.html https://www.space.com/spacex-starlink-satellites.html [3] https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome
- nordsieck 3y agoSpace junk at that altitude does turn into debris, but it tends to deorbit on its own in around 5-10 years. The real danger is space junk that's at much higher altitudes. OneWeb and Telesat Lightspeed (in planning) operate at 1000+ km, where space junk will take 1000+ years to deorbit on its own. And OneWeb has already had a satellite failure where it can't deorbit the satellite.
- montagg 3y agoI don’t have references for this, but my understanding is that you have more to worry about space debris that is higher/faster than lower/slower. The atmospheric drag is such that any out of control craft at [some threshold] or under will deorbit themselves fairly quickly, and the debris will burn up entirely. I believe that threshold is around 450-500km, but it’s also probably not a literal height, more of a gradient of risk. Higher/faster, they will be up there for longer (years? decades?) and it’s harder to predict where any broken pieces will go over time.
- idlewords 3y agoExcept that all distinct orbits at the same altitude eventually collide.
- deleted 3y ago[deleted]
- rdlw 3y agoWhat do you mean? If they're both circular orbits, they'll have the same period, so they'll never collide—they'll always be on opposite sides of the Earth. In fact, this goes for any two orbits with identical periods.
- InspiredIdiot 3y agoOnce anything collides with anything in orbit it has a slightly different trajectory. Any movement up or down will make its orbit more ellipsoidal than the original orbit. Also the atmosphere moves up and down in response to solar wind and therefore varies in both time and space. Atmospheric drag is apparently still a factor up to 600km https://www.swpc.noaa.gov/impacts/satellite-drag https://www.swpc.noaa.gov/impacts/satellite-drag Debris in a crowded orbit will eventually collide, no matter how synchronized it all was initially.
- aledalgrande 3y agoFrom the article you linked: > Debris between 1 cm and 10 cm (approximately 500,000), referred to as the “lethal” population, are the most concerning as they cannot be tracked or cataloged and can cause catastrophic damage when colliding with a satellite. Objects smaller than 1 cm (approximately 135 million measuring from 1mm to 1cm, and many more smaller than 1 mm) that could disable a satellite upon impact are termed the “risk” population
- jacquesm 3y agoThere is no such thing as an identical period. It may seem identical when you compare them casually but over time the little differences add up and sooner or later the two will intersect, unless either one of the two moves to a different orbit or de-orbits. Satellite orbits are not locked together by magic, they are all independent of each other.
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- youngtaff 3y agoYeh, but what happens when they all burn up? It’s pollution of the upper atmosphere on a huge scale and we don’t know what side effects that will produce