Space debris is a massive problem that is only getting worse. [1]
These objects aren't just floating up there, they're travelling at tens of thousands of miles per hour. If they can't be tracked, they can't be avoided.
These objects aren't just floating up there, they're travelling at tens of thousands of miles per hour. If they can't be tracked, they can't be avoided.
Starting with the weakest reason first, but one that's also very important. Space is really big. There are some 6 figures of tiny things in space and thousands of larger things. This sounds pretty scary. But now imagine that we put 6 figures of tiny things, and some thousands of large things in random places in the US and set them on a random path. You can intuit that the odds of any collision are going to be extremely low. And now imagine the entirety of LEO. It is magnitudes larger than the USA of course.
The next is that objects tend to be going in the same direction. Rockets take advantage of Earth's rotation to get a 'head start' on their launch which means that most things end up going in the same orbital direction. Two things going the same speed with the same orbital characteristics will never collide. With different orbital characteristics, they will get two chances for collision per orbit with an extremely low chance of it occurring by chance.
And maybe the biggest point is another really cool and counter intuitive part of space. When we think of the USA we obviously just think of the ground. But of course there is a vertical axis in space. And the awesome thing here is what determines your altitude in space. It's entirely based on your velocity (well and the mass of whatever you're orbiting). In other words, objects cannot collide unless they're traveling at the same rate of speed. Pretty neat!
Another issue is that even at LEO, objects do experience some atmospheric drag. Any object in LEO that is not occasionally correcting its orbit (accelerating) will eventually come back down to Earth. This includes all of that tiny debris.
So now make the US absurdly vastly larger. And create multiple layers of the USA where any given car traveling at any given speed goes on a specific layer. And set them [almost] all in the same direction. And finally remove small stuff (or 'decommissioned' cars) over time. So sure, space debris is something to definitely keep in mind - but I think people don't really realize how relatively irrelevant this is. Another thing is that even if we did experience some catastrophic kessler syndrome level event it would mostly have no impact on things going through LEO (and not orbiting within it) simply because the massiveness of space just means the odds of an impact are so very low. So it would not kill space travel as the video states.
And lastly, necessity is the mother of all invention. There are an enormous number of viable ideas for removing debris from space. But there hasn't been that much of a push for them simply because it's not really necessary yet. If we reach a point when it becomes necessary, there are solutions.
So issue? Sure. "Massive" issue. Nah.
Not true. Satellite orbits have all kinds of inclinations, including polar and retrograde. Just because you watched the Space Shuttle on TV getting launched into a typical prograde orbit doesn't mean all orbiting objects do that.
> what determines your altitude in space. It's entirely based on your velocity (well and the mass of whatever you're orbiting).
You are greatly oversimplifying orbital mechanics. Satellite orbits are not perfectly circular, and they have more than one degree of freedom.
No, even that's not the case. If it were, the delta v of anticipated collisions would be low enough that they wouldn't pose a serious problem.
The Wikipedia article on the Kessler syndrome, linked to upthread, gives some useful references. One of them is an article on how a cupola window on the ISS was pitted by a microscopic piece of space debris. The pit is 7 mm across, about the size of what a small rock would put in a car windshield at highway speed. How fast would an object about 1000 times smaller (and therefore about a billion times less massive) have to be traveling to have the same impact energy? (Hint: it's about the same as LEO orbital speed--but that's orbital speed relative to the ground, not relative to objects on nearby orbits in the same direction.)
Geostationary orbit is approximately 22,200 miles above the surface. At that height, the usable sphere for a satellite is 8,630,000,000 square miles. Certainly a huge deal of that isn't overly usable (polar, etc.), but nonetheless.
That's my trivia for the day.
At the time of writing, SOCRATES shows seven approaches closer than 100 metres in the next few days:
https://www.celestrak.com/cgi-bin/searchSOCRATES.pl?IDENT=NA...
But here's the thing. Momentum. If you've tracked it once, you know its location for many months to come.
Not in low-earth orbit. Look at this graph of the ISS's altitude over time [1]. Atmospheric drag makes orbital dynamics too complicated for long-term predictions. Add in station-keeping [2] jitter, and one has a necessity for reliable tracking.
[1] http://images.huffingtonpost.com/2014-05-17-ISSaltitude.png
https://en.m.wikipedia.org/wiki/Space_debris
"Below 2,000 km (1,200 mi) Earth-altitude, debris are denser than meteoroids; most are dust from solid rocket motors, surface erosion debris like paint flakes, and frozen coolant from RORSAT nuclear-powered satellites."
And the journal Orbital Debris Quarterly
https://orbitaldebris.jsc.nasa.gov/quarterly-news/newsletter...
This is not accurate. Even if you ignore the big vertical jumps at each burn, the downward trend is very obviously irregular. Satellites in LEO experience a slight drag force from the Earth's outer atmosphere, and the magnitude of this force can vary unpredictably by orders of magnitude depending on space weather conditions.
Satellites in orbit are moving very quickly, so a slight change in altitude (i.e. orbital period) results in a very large change in position at any given future time. More importantly, the inaccuracies are compounded with each subsequent orbit. As a rough estimate, an uncertainty of 1m in the height of a satellite in LEO translates to a positional error of more than 100m/day. It is not possible to accurately predict the position of a satellite without ongoing observations.