3 ms·

>... as long as their Kessler Syndrome half-life is low enough. And, you know, you haven't launched thousands of them. It's hard not to sigh at the persistence

by xoa 4y ago

>... as long as their Kessler Syndrome half-life is low enough. And, you know, you haven't launched thousands of them. It's hard not to sigh at the persistence of this getting applied mindlessly. The quantity isn't particularly important here, altitude is. There is still atmosphere at hundreds of kilometers, and thus there is still drag and in turn orbital decay. It falls off non-linearly with increasing altitude, but for low LEO and VLEO is very significant. You can see from the graph shown in the linked tweets that these only got to around 380km. At those altitudes lifetimes are measured in months [0]. You may also find it handy for visualizing to look at it in animated form with a Gabbard diagram [1], same result. Debris aren't an issue at low orbits because of how fast they decay, regardless of numbers. Indeed making use of that is directly part of the reason why SpaceX does Starlink launches the way it does, inserting low and then raising gradually via sat thrusters rather then just aiming directly for final orbit. Yes there are some reuse energy advantages and such, but it's also so that if there is a major problem (like this, or the batch they lost from unexpected solar atmospheric heating increasing drag) they fail safe, naturally decaying rapidly and burning back up even in the case of total control loss. ---- 0: https://www.spaceacademy.net.au/watch/debris/orblife.htm https://www.spaceacademy.net.au/watch/debris/orblife.htm 1: https://old.reddit.com/r/space/comments/ld4vlq/gabbard_diagram_animation_of_space_debris_since/ https://old.reddit.com/r/space/comments/ld4vlq/gabbard_diagr...

hinkley 4y ago
I'm curious what you two thought I meant when I said "Kessler half-life". Did you not think I was talking about decay? There's also two ways to think about it. What's the chance that we make a permanent wall of debris, and what's the odds that we take out everything in LEO and then have to wait months to get back to or from ISS.
- xoa 4y ago
  >I'm curious what you two thought I meant when I said "Kessler half-life". Since that's not really a term and you don't really seem to demonstrate any understanding here I don't know. You now claim to be talking about decay, except then you still say stuff that makes no sense if you understood decay, orbital inclinations, the kinds of distances involved here, or even where the constellation under discussion actually exists at all. >What's the chance that we make a permanent wall of debris At 380km with a few dozen sats? Zero. and what's the odds that we take out everything in LEO and then have to wait months to get back to or from ISS. Also zero, though this is nonsensical all over since ISS is at ~415km. What "Kessler" mechanism are you proposing to "take out everything" from 400-2000km (LEO) across all orbits, and somehow this doesn't hurt ISS at all (since your statement necessarily implies ISS still exists to go to/from)? And also prevents us from getting to/from 415km, which could only be done by incredibly dense debris below that. Space is big, this is stuff spread out over a greater area then the surface area of the Earth, massive debris could be an issue for something that wanted to stay in an orbit but odds of anything hitting a spacecraft merely moving through a single altitude in a matter of minutes/hours is minuscule even before ground based tracking. How is this big field of debris forming at <400km and not immediately starting to drop out? How does it even get self-sustaining in the first place given speed of decay there? In fact how many satellites do you think exist in all the orbits <400km, let alone in ISS' specific orbit? You talked about "thousands" with extra emphasis, so does that mean you think that Starlink maybe is at 380km as its permanent deployed orbit rather then the 550-570km that is its actual deployed orbit? Do you think that just maybe ISS has in fact been considered by nations worldwide and perhaps there are rules and extra caution around its orbit? Some things to contemplate upon, or even research.
  - hinkley 4y ago
    Have a good night. You seem to be going out of your way to misunderstand and I'm not interested.

by xoa 4y ago

hinkley 4y ago

I'm curious what you two thought I meant when I said "Kessler half-life". Did you not think I was talking about decay? There's also two ways to think about it. What's the chance that we make a permanent wall of debris, and what's the odds that we take out everything in LEO and then have to wait months to get back to or from ISS.

xoa 4y ago
>I'm curious what you two thought I meant when I said "Kessler half-life". Since that's not really a term and you don't really seem to demonstrate any understanding here I don't know. You now claim to be talking about decay, except then you still say stuff that makes no sense if you understood decay, orbital inclinations, the kinds of distances involved here, or even where the constellation under discussion actually exists at all. >What's the chance that we make a permanent wall of debris At 380km with a few dozen sats? Zero. and what's the odds that we take out everything in LEO and then have to wait months to get back to or from ISS. Also zero, though this is nonsensical all over since ISS is at ~415km. What "Kessler" mechanism are you proposing to "take out everything" from 400-2000km (LEO) across all orbits, and somehow this doesn't hurt ISS at all (since your statement necessarily implies ISS still exists to go to/from)? And also prevents us from getting to/from 415km, which could only be done by incredibly dense debris below that. Space is big, this is stuff spread out over a greater area then the surface area of the Earth, massive debris could be an issue for something that wanted to stay in an orbit but odds of anything hitting a spacecraft merely moving through a single altitude in a matter of minutes/hours is minuscule even before ground based tracking. How is this big field of debris forming at <400km and not immediately starting to drop out? How does it even get self-sustaining in the first place given speed of decay there? In fact how many satellites do you think exist in all the orbits <400km, let alone in ISS' specific orbit? You talked about "thousands" with extra emphasis, so does that mean you think that Starlink maybe is at 380km as its permanent deployed orbit rather then the 550-570km that is its actual deployed orbit? Do you think that just maybe ISS has in fact been considered by nations worldwide and perhaps there are rules and extra caution around its orbit? Some things to contemplate upon, or even research.
- hinkley 4y ago
  Have a good night. You seem to be going out of your way to misunderstand and I'm not interested.