5 ms·

"Move Fast and Break Things"?

by lozf 4y ago

oldgradstudent 4y ago
> "Move Fast and Break Things"? When satellites are cheap and launching then is cheap, this might be a reasonable approach.
- hinkley 4y ago
  ... as long as their Kessler Syndrome half-life is low enough. And, you know, you haven't launched thousands of them. Oh. Oops.
  - bpodgursky 4y ago
    They launch into a LEO explicitly so this can happen and it won't be a problem.
    - hinkley 4y ago
      The complaints I’ve heard is that LEO is great but there’s a carrying capacity for any orbit and people are worried that starlink is over that limit even for LEO. I’m not orbital mechanics expert but when we discussed it at the time I believe it was agreed that a collision can launch debris into higher orbits but on a parabolic path, so if it doesn’t encounter anything else in a couple orbits it probably never will. Also some of the LEO SpaceX has been approved for are higher than the ISS, not just lower. Kessler is mostly worried about long term debris patterns, but one that cleans itself up in a few months could still cause a many billions in damage and loss of life. Also starlink enables some terrestrial activities that might not be wise without it. A cascade could leave some earthbound people fucked as well. That’s partially on them of course, but the optics are not great.
    - walrus01 4y ago
      All starlink satellites are LEO, just varying degrees of it. They release the satellites from the second stage deliberately quite low, because it's more efficient in total weight carried by second stage, and more efficient in specific impulse to spend weight in kilograms of propellant tankage on the satellite for ion/hall effect type thrusters (specific impulses of 2000 ISP and greater) than to place N additional kg of fuel on the second stage to release them all in a higher orbit. At the release altitude they're above the vast majority of the earth's atmosphere and solar panels + ion thruster burning prograde are sufficient to raise their altitudes to the intended operational orbit.
  - 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.
  - brandonagr2 4y ago
    Good news, they only launched 21 of these (v2 mini), and if OP is correct they will decay and deorbit quickly.
    - hinkley 4y ago
      That is good news. It remains to be seen if there will be other problems that take longer to discover.
      - grecy 4y ago
        You mean , like, the same as for anything that has ever been built in all of history?
        hinkley 4y ago
        Mission ending problems? James Webb has something like 300 things that had to go right for it to work. I thought, “that’s nuts” but apparently they thought it could be done and here we are. But that may also explain why it went way over the time estimates.
        grecy 4y ago
        I was replying to: > It remains to be seen if there will be other problems that take longer to discover Which is a comment that applies to literally everything that humans have ever done in all of history.
  - Dylan16807 4y ago
    > as long as their Kessler Syndrome half-life is low enough. Not only is this a safe area, they appear to be deorbiting and they'll be gone very soon. > And, you know, you haven't launched thousands of them. They have only launched a handful of the ones having trouble. > Oh. Oops. ?
  - deleted 4y ago
    [deleted]

"Move Fast and Break Things"?

by lozf 4y ago

"Move Fast and Break Things"?

> "Move Fast and Break Things"? When satellites are cheap and launching then is cheap, this might be a reasonable approach.

hinkley 4y ago
... as long as their Kessler Syndrome half-life is low enough. And, you know, you haven't launched thousands of them. Oh. Oops.
- bpodgursky 4y ago
  They launch into a LEO explicitly so this can happen and it won't be a problem.
  - hinkley 4y ago
    The complaints I’ve heard is that LEO is great but there’s a carrying capacity for any orbit and people are worried that starlink is over that limit even for LEO. I’m not orbital mechanics expert but when we discussed it at the time I believe it was agreed that a collision can launch debris into higher orbits but on a parabolic path, so if it doesn’t encounter anything else in a couple orbits it probably never will. Also some of the LEO SpaceX has been approved for are higher than the ISS, not just lower. Kessler is mostly worried about long term debris patterns, but one that cleans itself up in a few months could still cause a many billions in damage and loss of life. Also starlink enables some terrestrial activities that might not be wise without it. A cascade could leave some earthbound people fucked as well. That’s partially on them of course, but the optics are not great.
  - walrus01 4y ago
    All starlink satellites are LEO, just varying degrees of it. They release the satellites from the second stage deliberately quite low, because it's more efficient in total weight carried by second stage, and more efficient in specific impulse to spend weight in kilograms of propellant tankage on the satellite for ion/hall effect type thrusters (specific impulses of 2000 ISP and greater) than to place N additional kg of fuel on the second stage to release them all in a higher orbit. At the release altitude they're above the vast majority of the earth's atmosphere and solar panels + ion thruster burning prograde are sufficient to raise their altitudes to the intended operational orbit.
- 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.
- brandonagr2 4y ago
  Good news, they only launched 21 of these (v2 mini), and if OP is correct they will decay and deorbit quickly.
  - hinkley 4y ago
    That is good news. It remains to be seen if there will be other problems that take longer to discover.
    - grecy 4y ago
      You mean , like, the same as for anything that has ever been built in all of history?
      - hinkley 4y ago
        Mission ending problems? James Webb has something like 300 things that had to go right for it to work. I thought, “that’s nuts” but apparently they thought it could be done and here we are. But that may also explain why it went way over the time estimates.
        grecy 4y ago
        I was replying to: > It remains to be seen if there will be other problems that take longer to discover Which is a comment that applies to literally everything that humans have ever done in all of history.
- Dylan16807 4y ago
  > as long as their Kessler Syndrome half-life is low enough. Not only is this a safe area, they appear to be deorbiting and they'll be gone very soon. > And, you know, you haven't launched thousands of them. They have only launched a handful of the ones having trouble. > Oh. Oops. ?
- deleted 4y ago
  [deleted]