Scale distortion is very practical when differences are either miniscule or astronomical. A poster of our solar system where the sun and planets are at scale would look like a black piece of paper with a tiny white dot in the center.
> that there are city sized satellites flying above them
I don't think this is so much the issue, as much as that I didn't think about it.
I opened it and my first thought was wow, it's packed up there. Didn't consider the size of the things it's displaying relative to things on the surface.
There is certainly some merit in ensuring that first impression is accurate.
Yes. I once overheard a flat earther argue that spare reporting is fake because there are supposed to be tens of thousands of satellites, yet photos from the ISS don't show any of them.
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.
“any accurate depiction of elevation would be indistinguishable from a flat map at that scale. The coast-to-coast measure of the US is a bit under 3000 miles, while the highest elevation in the continental US is a bit under 4½ miles above sea level, so in a 1000-pixel map, that would translate to a 1–2 pixel height for Mt Whitney which is the highest point in the contiguous United States.”
and also
“the difference in elevation between Everest and the Marianas Trench is less than the bulging of the earth from its rotation. And that amount is less than you might guess. If we scale the earth down to a diameter of one foot (which would be bigger than my childhood globe), the bulge would be 0.04in or roughly 1mm. Good luck distinguishing your oblate spheroid from a sphere with those numbers.”
Yes and to be clear on what "practical" means here. If there's a mountain between origin-destination for a road trip it's relevant to highlight it. In the case of orbits the objects may be small but they're very fast and very dangerous.
An honest visualization to scale would just have the satellites being faint dust smaller than your pixels? Wouldn't be useful. But agreed that if you could zoom in and visualize the actual scale that'd be interesting and informative. Would be cool seeing the difference in satellite size. But would be less useful as a broader visualization of LEO.
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
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"
> the Kesler syndrome, a space debriss cascade is a very real threat and a real concern
It’s also widely misunderstood.
The risk is in trashing specific orbits. Below 600 km, that would mean certain orbits are too polluted to use for a few months to years. (A dense, compact object above 600 km could stay lofted for decades to over a century. But again, only within a predictable volume.)
Some kind of a relative velocity at the closest approach or a collision probability overlay would be way more useful to have than proper scale. That would make it immediately clear that lazy well-kept orbits like GEO are much safer than e.g. 567km SSO at the poles. Or some color coding for the apparent magnitude.
While I totally agree with the logic, this particular visualization might mislead unsuspecting viewers into believing that our LEO is almost fully saturated. In reality, the satellites are so small that they would miss each other even if placed on the same orbit.
well... Out sky is full of satellites.
Granted, there's a lot of empty space in between. But ask any (hobby) astronomer and they'll start a rant about starlink :-P
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).
Three now, Starlink Group 9-3 launch failed in July last year. After the failure, the launch hold was cleared in 13 days, which has to be a record of some sort.
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.
Specific orbits (732km with a 28 degree inclination and 130 degree longitude of the ascending node), but impacts also instantaneously spread debris out over anything close to any of those numbers (700-760, 27-29, 125-135); most debris get spread not in a normal distribution but in a bimodal distribution between the orbital elements of the two impactors, with an additional perimeter of debris kicked out with some random modest dV in every direction from the explosion according to how much impact energy they absorbed. To start with.
But then, debris start to decay, and they decay unevenly, polluting all orbits lower than that. As this debris spreads to a crowded lower orbit it generates additional collisions.
Orbits are cleared to lower orbits according to mass cross section at roughly 10x the rate for every 100km altitude drop. So everything that decays from an accumulation of higher orbits has to eventually pass through a 300km circular orbit, but it's relatively safe because it spends so little time there.
Going full exponential cascade at 1000km might increase the number of impactors by a millionfold, though, which then proceed to rain down over the years on lower orbits.
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.
Those large red blobs are not visualizations of debris fields. You can toggle them off as "instruments", and debris is actually toggled off by default.
Readit News
Graphing scale honestly is extremely important. A lot of people are convinced our sky is full of satellites because of visualizations like this.
Yes. And therefore a very valuable visualisation of reality.
Visualisations at scale are nice and useful, too, but they are misleading if the actual sizes are never shown to the target audience.
I don't think this is so much the issue, as much as that I didn't think about it.
I opened it and my first thought was wow, it's packed up there. Didn't consider the size of the things it's displaying relative to things on the surface.
There is certainly some merit in ensuring that first impression is accurate.
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.
The fact that debris objects swee through an enormous volume of space per year (and are up there for years to centuries) makes it much worse.
https://commons.wikimedia.org/wiki/File:Orbital_Debris_Lifet...
http://www.youtube.com/watch?v=RvZ3Lr-Tj6A
“any accurate depiction of elevation would be indistinguishable from a flat map at that scale. The coast-to-coast measure of the US is a bit under 3000 miles, while the highest elevation in the continental US is a bit under 4½ miles above sea level, so in a 1000-pixel map, that would translate to a 1–2 pixel height for Mt Whitney which is the highest point in the contiguous United States.”
and also
“the difference in elevation between Everest and the Marianas Trench is less than the bulging of the earth from its rotation. And that amount is less than you might guess. If we scale the earth down to a diameter of one foot (which would be bigger than my childhood globe), the bulge would be 0.04in or roughly 1mm. Good luck distinguishing your oblate spheroid from a sphere with those numbers.”
So lie?
You can see from the comments most Hacker News users can't handle the abstraction.
Your blog post is great, but most people don't know the Earth is a perfect sphere or simple things like the sun is white, the real "Don't Look Up"
Universities have become pop culture, they are Gravity (2013), not 'science', whatever that word means now.
We cross mountains so that abstraction has a use, here it is for the nihilist crowd.
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/
It’s also widely misunderstood.
The risk is in trashing specific orbits. Below 600 km, that would mean certain orbits are too polluted to use for a few months to years. (A dense, compact object above 600 km could stay lofted for decades to over a century. But again, only within a predictable volume.)
We risk solving the wrong problem due to bad visualisations of the situation.
Deleted Comment
[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.
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.
Kessler is more analogous to pollution than a brick wall. Specific orbits get trashed by a cascade, not the entire sky.
But then, debris start to decay, and they decay unevenly, polluting all orbits lower than that. As this debris spreads to a crowded lower orbit it generates additional collisions.
Orbits are cleared to lower orbits according to mass cross section at roughly 10x the rate for every 100km altitude drop. So everything that decays from an accumulation of higher orbits has to eventually pass through a 300km circular orbit, but it's relatively safe because it spends so little time there.
Going full exponential cascade at 1000km might increase the number of impactors by a millionfold, though, which then proceed to rain down over the years on lower orbits.