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> The satellite part of the Starlink system is practically invulnerable to physical attack because there are so many satellites in different orbits. Hitting the

> The satellite part of the Starlink system is practically invulnerable to physical attack because there are so many satellites in different orbits. Hitting them all would require a prohibitively large number of rocket launches. What about lasers? Since even if it just heated up the satellite it could cause damage since they have no way of cooling.

rocqua 5y ago
Lasers have rather short range because of dispersion. The 'beam' widens over time. This is not a limitation of the laser or the lens, its a feature of physics and the wave-like nature of light. This is before considering the effects of atmosphere between a ground based laser and the satellite. This will make dispersion much worse.
- qsdf38100 5y ago
  Hmmm, isn’t it very small though ? It’s able to reflect on a mirror on the moon and come back to earth, still as a focused beam, right ?
  - wiredfool 5y ago
    Lasers that bounce off the moon come back to earth as a few detectable photons, not as a beam of light that you’d recognize without very specialized equipment.
    - wiredfool 5y ago
      Well, to rephrase a bit, laser beams that bounce off the moon. Lasers that bounce off the moon are an expensive way to make a small crater.
- EarthLaunch 5y ago
  So the question of effectiveness depends on how easy it is to pump kilowatts of laser energy at a satellite, and how much of that energy reaches the satellite based on dispersion from distance and atmosphere. Needs to be calculated. My guess is that since countries have tried creating laser defenses, someone knows.
  - jerf 5y ago
    Also bear in mind that satellites must be radiation hardened to function at all, because they're already in a high-radiation environment. I have no doubt a military could build a weapon that could use some form of EMP pulse to completely destroy my cell phone if it were an equivalent distance from a ground-based attack site, in an environment where it wouldn't be simply destroyed. Heck, I wouldn't be surprised there's some researchers who could put something together from their test bench and bits lying around in the lab in a day or two. Doing it to a hardened target is going to be much harder.
  - rocqua 5y ago
    See other comment by me for some basic calculation: https://news.ycombinator.com/item?id=30575702 https://news.ycombinator.com/item?id=30575702 It seems not totally out of the question. My calculation yielded an aperture requirement of 1cm for a blue-ish laser. Which yields a 50m beam at the height of a starlink satelite
- Diesel555 5y ago
  Do you think these findings from the Defense Intelligence Agency are overstating capability? > Directed Energy Weapons. China likely is pursuing laser weapons to disrupt, degrade, or damage sat- ellites and their sensors and possibly already has a limited capability to employ laser systems against satellite sensors. China likely will field a ground-based laser weapon that can counter low-orbit space-based sensors by 2020, and by the mid-to-late 2020s, it may field higher power systems that extend the threat to the structures of non-optical satellites. https://aerospace.csis.org/wp-content/uploads/2019/03/20190101_ChallengestoSecurityinSpace_DIA.pdf https://aerospace.csis.org/wp-content/uploads/2019/03/201901... Here is a more academic article discussing the risk from ground based Satellite Laser Ranging systems to optical sensors, specifically when they are imaging the area near the SLR. I'm guessing the power required to damage structure vs optical sensors are probably orders of magnitude different. > This density is 100 times the damage threshold of 106 J/m2, and will damage the pixel unless the laser light is filtered. In this case both the pixels and the filter may be damaged. (There is a caveat to the above statement based on timing probability being very low) https://scienceandglobalsecurity.org/archive/sgs17butt.pdf https://scienceandglobalsecurity.org/archive/sgs17butt.pdf
  - rocqua 5y ago
    I think these are trying to overload/damage the sensors on a satellite. Rather than damaging the body of the satellite. Makes sense, given that the sensors are made to be more sensitive.
    - Diesel555 5y ago
      For the first quote DIA stated > ...it may field higher power systems that extend the threat to the structures of non-optical satellites Just conjecture?
      - rocqua 5y ago
        The math here is doable. Approximately the inner angle of the cone of light comming from a laser beam is 1.22 2lamda/d (source: airy disk wikipedia). Where lamda is wavelength and d is the aperture. Lets pick lamda so 1.222lamda is 1000nm (blueish light). Then by smal angle approximation, the size of a beam at 500km (starlink height) is 500km * 1000nm / d Say we want our beam to be 50m wide. That gives an aperture requirement of 1cm. Huh, that seems reasonable. So in a vacuum, it could perhaps be done. Atmospheric effects would make this worse ofcourse. And a 50m beam is not going to dump much heat, but it seems somewhat plausible in the near future.
bell-cot 5y ago
That's far easier to do (lower power needed to cause major damage) against satellites which have optically sensitive parts pointed toward the Earth. Starlink satellites probably don't. And whether with lasers, missiles, or whatever - targeting a US-based satellite network that is near & dear to the Pentagon would be an extreme escalation. Especially after the Russians warned that any hacking of their satellites would be seen as justification for war.

rocqua 5y ago

Lasers have rather short range because of dispersion. The 'beam' widens over time. This is not a limitation of the laser or the lens, its a feature of physics and the wave-like nature of light. This is before considering the effects of atmosphere between a ground based laser and the satellite. This will make dispersion much worse.

qsdf38100 5y ago
Hmmm, isn’t it very small though ? It’s able to reflect on a mirror on the moon and come back to earth, still as a focused beam, right ?
- wiredfool 5y ago
  Lasers that bounce off the moon come back to earth as a few detectable photons, not as a beam of light that you’d recognize without very specialized equipment.
  - wiredfool 5y ago
    Well, to rephrase a bit, laser beams that bounce off the moon. Lasers that bounce off the moon are an expensive way to make a small crater.
EarthLaunch 5y ago
So the question of effectiveness depends on how easy it is to pump kilowatts of laser energy at a satellite, and how much of that energy reaches the satellite based on dispersion from distance and atmosphere. Needs to be calculated. My guess is that since countries have tried creating laser defenses, someone knows.
- jerf 5y ago
  Also bear in mind that satellites must be radiation hardened to function at all, because they're already in a high-radiation environment. I have no doubt a military could build a weapon that could use some form of EMP pulse to completely destroy my cell phone if it were an equivalent distance from a ground-based attack site, in an environment where it wouldn't be simply destroyed. Heck, I wouldn't be surprised there's some researchers who could put something together from their test bench and bits lying around in the lab in a day or two. Doing it to a hardened target is going to be much harder.
- rocqua 5y ago
  See other comment by me for some basic calculation: https://news.ycombinator.com/item?id=30575702 https://news.ycombinator.com/item?id=30575702 It seems not totally out of the question. My calculation yielded an aperture requirement of 1cm for a blue-ish laser. Which yields a 50m beam at the height of a starlink satelite
Diesel555 5y ago
Do you think these findings from the Defense Intelligence Agency are overstating capability? > Directed Energy Weapons. China likely is pursuing laser weapons to disrupt, degrade, or damage sat- ellites and their sensors and possibly already has a limited capability to employ laser systems against satellite sensors. China likely will field a ground-based laser weapon that can counter low-orbit space-based sensors by 2020, and by the mid-to-late 2020s, it may field higher power systems that extend the threat to the structures of non-optical satellites. https://aerospace.csis.org/wp-content/uploads/2019/03/20190101_ChallengestoSecurityinSpace_DIA.pdf https://aerospace.csis.org/wp-content/uploads/2019/03/201901... Here is a more academic article discussing the risk from ground based Satellite Laser Ranging systems to optical sensors, specifically when they are imaging the area near the SLR. I'm guessing the power required to damage structure vs optical sensors are probably orders of magnitude different. > This density is 100 times the damage threshold of 106 J/m2, and will damage the pixel unless the laser light is filtered. In this case both the pixels and the filter may be damaged. (There is a caveat to the above statement based on timing probability being very low) https://scienceandglobalsecurity.org/archive/sgs17butt.pdf https://scienceandglobalsecurity.org/archive/sgs17butt.pdf
- rocqua 5y ago
  I think these are trying to overload/damage the sensors on a satellite. Rather than damaging the body of the satellite. Makes sense, given that the sensors are made to be more sensitive.
  - Diesel555 5y ago
    For the first quote DIA stated > ...it may field higher power systems that extend the threat to the structures of non-optical satellites Just conjecture?
    - rocqua 5y ago
      The math here is doable. Approximately the inner angle of the cone of light comming from a laser beam is 1.22 2lamda/d (source: airy disk wikipedia). Where lamda is wavelength and d is the aperture. Lets pick lamda so 1.222lamda is 1000nm (blueish light). Then by smal angle approximation, the size of a beam at 500km (starlink height) is 500km * 1000nm / d Say we want our beam to be 50m wide. That gives an aperture requirement of 1cm. Huh, that seems reasonable. So in a vacuum, it could perhaps be done. Atmospheric effects would make this worse ofcourse. And a 50m beam is not going to dump much heat, but it seems somewhat plausible in the near future.

bell-cot 5y ago

That's far easier to do (lower power needed to cause major damage) against satellites which have optically sensitive parts pointed toward the Earth. Starlink satellites probably don't. And whether with lasers, missiles, or whatever - targeting a US-based satellite network that is near & dear to the Pentagon would be an extreme escalation. Especially after the Russians warned that any hacking of their satellites would be seen as justification for war.