Nice to see United Kingdom using a predictable trajectory. Dismayed by so many other nations just crapping all over the planet without consideration though. The lack of foresight is frustrating.
Actually the Kesler syndrome, a space debriss cascade is a very real threat and a real concern. I suggest an interview with the commander of the space control quadron in a radiolab episode "Little Big Questions"
Yep, it looks much more dramatic than that is. A realistic scale would make objects invisible, unfortunately. So I can see why they make things bigger than they are.
The reason why there are so few incidents is that low earth orbit is simply a very large volume of space. It would be a mistake to think of it in 2D terms, it's a few hundred km in height and it has an area even at the lowest orbit that is larger than the surface of the earth. The total volume is orders of magnitudes larger than all our oceans combined.
So what's the chance of 2 out of a few hundred thousand things floating around in random orbits crashing into each other? It's not zero. But it's close enough to zero that it's very rare. But high enough that people worry about it somewhat. Obviously some orbits are quite congested and having a lot of debris scattering all over the place after a collision makes things worse. And the speeds at which things are moving around would cause some high energy collisions even for small objects.
Objects are not to scale for unavoidable reasons, but time is also not to scale. These two effects tend to cancel out.
People look at this visualization for what, 60 seconds? But the issue is that objects are zooming around up there for years-to-centuries.[0] The total volume of space swept out is massive.
Invariably the "not to scale" comments always get pointed out every time this is posted, but the temporal distortion (which makes people underestimate collisions) is never mentioned. Unless I mention it[1] of course... ;)
There's a much much better educational ESA video[2] which addresses some of the misconceptions in this thread, found via (of all places) Don Kessler's personal website.
---
If you want an expert perspective on orbital debris (vs..... whatever these HN threads always turn into :D ) I highly recommend you check out NASA Johnson's Orbital Debris Quarterly.[3]
[2] As this video points out, collisions scale as density squared, which is why all major collisions have happened near 80 degrees latitude: http://www.youtube.com/watch?v=RvZ3Lr-Tj6A
If anyone is curious, as I was, about the large red shapes on the map, those are the beams of the object tracking/measurement sites. They correlate with the maps at [0]. I was actually pretty blown away when I started reading that page. Apparently those stations can measure <10cm-sized debrisin orbit. What?! Amazing.
The instrument is the particular radar. They usually have two at each location. Each radar is essentially a linear phased array that creates multiple possible beam locations in the radar plane. They light up a beam as a satellite passes through in order to collect measurements. TLDR an instrument has multiple beams.
For those who don't know, Leo Labs operates a commercial version of NORAD radar sites that track satellites and debris.
If you're a satellite operator looking to avoid conjunctions, then buying additional measurements helps reduce uncertainty (which is often needed in order to decide if you should conduct a maneuver).
This is the opposite of depressing. Look what we've been able to do! Each of those have/had a purpose and reason for being there and we've gotten tremendous benefit from satellites in space.
If you zoom in, about one in 20 is tumbling around path randomly, and its description is “Rocket body”. But it’s not on “Debris” layer.
I wonder why it doesn’t qualify for debris if it looks likely uncontrollable.
Just a reminder to everybody that we are competitively sprinting towards the brick wall of Kessler Syndrome by building out mega-constellations between about 600km and 1600km, sacrificing humanity's future in order to save a small amount of money right now using lower altitude orbits.
Even Starlink is arguably flying too high, but the attempt to compete with them at 1000km where satellites will be causing secondary and tertiary debris events for literally millennia, makes that look sensible.
Starlink is just under 600km in order to target a specific voluntary threshold of 25 year decay. Most of their finished birds are going to make around 5 years without propulsion or impacts.
Three things about that -
Profitability generates competition, which may or may not respect precedent. Right now Starlink is only really worried about collisions with other parts of Starlink. We cannot afford a Starlink-inspired future to happen at 600km.
Debris generating events can spin out an object with much higher cross sectional mass than an intact satellite. Think of it in terms of what we use drag for on Earth, like a kid building kites. A heavy metal bolt works worse as a kite than a long thin panel.
These calendar decay timelines are blind to density. If there are a billion satellites with a natural lifespan of 5 years flying at 551km then they are going to go into an exponential cascade in a matter of weeks. If you plan to launch very large constellations, you need very fast decay timelines to keep that safe. It is much safer at very low altitude. There is decay 'room' for >10x as many satellites at 300km as at 400km, and >10x as many at 400km as at 500km, and >10x as many at 500km as 600km.
...
It would also be nice to set aside something for manned spaceflight. Unlike with a satellite collision, if a pressure vessel gets penetrated everybody dies and nobody wants to go back. The ISS and Tianhe are going to have to deal with debris risk slowly raining down from a collision at 971km.
This reminds me - I've been looking for an app, website or tool that can predict or visualize the location of any satellite up to a week out. Most softwares show only the intersection times of predicted orbits with fixed locations on earth, i.e. for telescope visibility.
The visualisation is cool. I've never seen the debris fields visualized before. They look like scars. Might be neat to see a viz including the geo synchronous and sun synchronous orbits. Should show up as seemingly dense, but far away.
28 comments
[ 2.8 ms ] story [ 58.4 ms ] threadGraphing scale honestly is extremely important. A lot of people are convinced our sky is full of satellites because of visualizations like this.
The reason why there are so few incidents is that low earth orbit is simply a very large volume of space. It would be a mistake to think of it in 2D terms, it's a few hundred km in height and it has an area even at the lowest orbit that is larger than the surface of the earth. The total volume is orders of magnitudes larger than all our oceans combined.
So what's the chance of 2 out of a few hundred thousand things floating around in random orbits crashing into each other? It's not zero. But it's close enough to zero that it's very rare. But high enough that people worry about it somewhat. Obviously some orbits are quite congested and having a lot of debris scattering all over the place after a collision makes things worse. And the speeds at which things are moving around would cause some high energy collisions even for small objects.
People look at this visualization for what, 60 seconds? But the issue is that objects are zooming around up there for years-to-centuries.[0] The total volume of space swept out is massive.
Invariably the "not to scale" comments always get pointed out every time this is posted, but the temporal distortion (which makes people underestimate collisions) is never mentioned. Unless I mention it[1] of course... ;)
There's a much much better educational ESA video[2] which addresses some of the misconceptions in this thread, found via (of all places) Don Kessler's personal website.
---
If you want an expert perspective on orbital debris (vs..... whatever these HN threads always turn into :D ) I highly recommend you check out NASA Johnson's Orbital Debris Quarterly.[3]
Sources:
[0] What really matters is altitude as this graph shows: https://commons.wikimedia.org/wiki/File:Orbital_Debris_Lifet...
[1] https://news.ycombinator.com/item?id=33210261
[2] As this video points out, collisions scale as density squared, which is why all major collisions have happened near 80 degrees latitude: http://www.youtube.com/watch?v=RvZ3Lr-Tj6A
[3] https://www.orbitaldebris.jsc.nasa.gov/quarterly-news/
[0] https://leolabs.space/radars/
If you're a satellite operator looking to avoid conjunctions, then buying additional measurements helps reduce uncertainty (which is often needed in order to decide if you should conduct a maneuver).
And all those were launched on Falcon 9 rockets, with I think only two launch failures ever.
In reality theyre so small that it makes this look 100x worse than it actually is
Even Starlink is arguably flying too high, but the attempt to compete with them at 1000km where satellites will be causing secondary and tertiary debris events for literally millennia, makes that look sensible.
Three things about that -
Profitability generates competition, which may or may not respect precedent. Right now Starlink is only really worried about collisions with other parts of Starlink. We cannot afford a Starlink-inspired future to happen at 600km.
Debris generating events can spin out an object with much higher cross sectional mass than an intact satellite. Think of it in terms of what we use drag for on Earth, like a kid building kites. A heavy metal bolt works worse as a kite than a long thin panel.
These calendar decay timelines are blind to density. If there are a billion satellites with a natural lifespan of 5 years flying at 551km then they are going to go into an exponential cascade in a matter of weeks. If you plan to launch very large constellations, you need very fast decay timelines to keep that safe. It is much safer at very low altitude. There is decay 'room' for >10x as many satellites at 300km as at 400km, and >10x as many at 400km as at 500km, and >10x as many at 500km as 600km.
...
It would also be nice to set aside something for manned spaceflight. Unlike with a satellite collision, if a pressure vessel gets penetrated everybody dies and nobody wants to go back. The ISS and Tianhe are going to have to deal with debris risk slowly raining down from a collision at 971km.