4 ms·

If a target is moving slow enough it can be difficult to track. Similar to how you can defend against radar missiles by 'notching' aka flying perpendicular so

If a target is moving slow enough it can be difficult to track. Similar to how you can defend against radar missiles by 'notching' aka flying perpendicular so the relative velocity of the target is near zero. Radar typically relies on the dopplar shift caused by the target moving to eliminate clutter.

WalterBright 3y ago
The solution then would be to have two radars a distance apart, so they can triangulate.
- jcrawfordor 3y ago
  Locating the target isn't the problem, you don't need a Doppler shift to calculate range by time of flight. The problem is detecting the target at all. Radar in these sorts of defense environments will pick up an enormous number of returns off of the carrying vessel and sea surf, which is actually a rather difficult problem for radar because it reflects in myriad directions, it moves, etc. By far the easiest way to select an "interesting" radar return is to use Doppler shift to find something that is moving very quickly. That can't be just a wave, it has to be a missile. The problem is that rotary wing drones are very slow (compared to missiles) and so they don't present an obviously different shift from the background. A lot of R&D is going on right now into better ways to select slow-moving, low-cross-section objects like drones from the background. This sort of thing is much more difficult for missile defense than the more conventional radar application of airspace surveillance, because for several reasons (including the fact that this makes radar detection hard) missiles tend to come at you from close to or below the horizon. This means you're getting a huge amount of clutter (radar returns from the environment) around them.
  - deleted 3y ago
    [deleted]
  - icegreentea2 3y ago
    Not to minimize the challenges, but I think it's worth pointing out that a lot of the drones of topical interest are -not- quadcopters. The Houthis (for example) have been using UAVs (Samad and Qasef) are prop driven fixed wing drones with total mass in the 50kg+ class (and warheads in the ~20kg class). They have max speeds of 200+ kph, wingspans in the 2-5m range. The Samad has ranges in the 1000km+ range. Obviously, they could slow down in terminal stages of attack, and I have no idea what their stall speed would be like. These are more akin to the Shahed class drones that Russia has been deploying in Ukraine (though still much smaller), than the FPV drones we see attacking tanks/trenches.
    - WalterBright 3y ago
      The British used radar guided artillery to knock down wave after wave of V1s, which flew at around 400mph. Surely we could do better today.
      - icegreentea2 3y ago
        Totally. I just guess the US didn't procure/deploy/use/turn-on the appropriate systems. Plenty of other posts in the comments identifying potential modern (and modern-ish) solutions that match your parameters.
      - robbiep 3y ago
        Really? I had heard that sometimes pilots would nudge them off course or shoot them down but nothing about artillery, I thought radar came along a bit too late to use it for targeting with regard to the V1
        actionfromafar 3y ago
        I thought so too, but lately I have heard and read accounts akin to a lot of what happened in late WW2 with regards to radar technology was highly classified and much didn't enter the history books. Pilots shooting and nudging definitely happened but likely other, more advanced stuff happened too. The germans had fully automatic radar controlled flak guns.
  - WalterBright 3y ago
    I'm talking about a land based system to defend military bases from drone attack, not sea borne vessels.
wolverine876 3y ago
If they can't see the target, how do they shoot missiles at it? I've wondered the same as the GP: Why not just send a wall of metal at the drone from one of these things? If not that, why not traditional anti-aircraft fire, with projectiles that explode in shrapnel clouds?
- ethbr1 3y ago
  > Why not just send a wall of metal at the drone from one of these things? If not that, why not traditional anti-aircraft fire, with projectiles that explode in shrapnel clouds? If this had been the 1950s or early 60s, every advanced military on the planet would have been able to do exactly that. However, both aircraft (MiG-19+) and missiles were speeding up. At some speed, it becomes impractical to solve a high-speed aircraft or missile problem with a gun. [0] Consequently, development from the 70s on turned to missiles capable of dealing with these threats. Which left the only remaining systems mostly consequences of failure to upgrade (e.g. the German Gepard). As the saying goes, history doesn't repeat itself, but it rhymes... [0] See: M19 (1945) > M42 (1953) > MIM-46 (1960-63, cancelled) > M-163 (1965) > MIM-72 (1967) https://en.m.wikipedia.org/wiki/M19_Multiple_Gun_Motor_Carriage https://en.m.wikipedia.org/wiki/M19_Multiple_Gun_Motor_Carri... https://en.m.wikipedia.org/wiki/M42_Duster https://en.m.wikipedia.org/wiki/M42_Duster https://en.m.wikipedia.org/wiki/MIM-46_Mauler https://en.m.wikipedia.org/wiki/MIM-46_Mauler https://en.m.wikipedia.org/wiki/M163_VADS https://en.m.wikipedia.org/wiki/M163_VADS https://en.m.wikipedia.org/wiki/MIM-72_Chaparral https://en.m.wikipedia.org/wiki/MIM-72_Chaparral
  - WalterBright 3y ago
    The drones used by terrorists are homemade and slow moving.
    - ethbr1 3y ago
      But those weren't the primary threat military defense of ~1965-2020 was designed against. (Higher then) Lower, faster, and/or stealthier were the worries. And aside from the economically-mobilized war that Ukraine is fighting (and Russia is gradually shifting to), it's unclear if capability or cost need to be optimized. For every conflict economically less than that, capability wins. I expect the FPV quadcopter grenade-on-a-drone solution will be looked back on like the Toyota Hilux tactical -- effective when introduced, but superceded and dominated by specialized systems produced by military industry.

WalterBright 3y ago

The solution then would be to have two radars a distance apart, so they can triangulate.

jcrawfordor 3y ago
Locating the target isn't the problem, you don't need a Doppler shift to calculate range by time of flight. The problem is detecting the target at all. Radar in these sorts of defense environments will pick up an enormous number of returns off of the carrying vessel and sea surf, which is actually a rather difficult problem for radar because it reflects in myriad directions, it moves, etc. By far the easiest way to select an "interesting" radar return is to use Doppler shift to find something that is moving very quickly. That can't be just a wave, it has to be a missile. The problem is that rotary wing drones are very slow (compared to missiles) and so they don't present an obviously different shift from the background. A lot of R&D is going on right now into better ways to select slow-moving, low-cross-section objects like drones from the background. This sort of thing is much more difficult for missile defense than the more conventional radar application of airspace surveillance, because for several reasons (including the fact that this makes radar detection hard) missiles tend to come at you from close to or below the horizon. This means you're getting a huge amount of clutter (radar returns from the environment) around them.
- deleted 3y ago
  [deleted]
- icegreentea2 3y ago
  Not to minimize the challenges, but I think it's worth pointing out that a lot of the drones of topical interest are -not- quadcopters. The Houthis (for example) have been using UAVs (Samad and Qasef) are prop driven fixed wing drones with total mass in the 50kg+ class (and warheads in the ~20kg class). They have max speeds of 200+ kph, wingspans in the 2-5m range. The Samad has ranges in the 1000km+ range. Obviously, they could slow down in terminal stages of attack, and I have no idea what their stall speed would be like. These are more akin to the Shahed class drones that Russia has been deploying in Ukraine (though still much smaller), than the FPV drones we see attacking tanks/trenches.
  - WalterBright 3y ago
    The British used radar guided artillery to knock down wave after wave of V1s, which flew at around 400mph. Surely we could do better today.
    - icegreentea2 3y ago
      Totally. I just guess the US didn't procure/deploy/use/turn-on the appropriate systems. Plenty of other posts in the comments identifying potential modern (and modern-ish) solutions that match your parameters.
    - robbiep 3y ago
      Really? I had heard that sometimes pilots would nudge them off course or shoot them down but nothing about artillery, I thought radar came along a bit too late to use it for targeting with regard to the V1
      - actionfromafar 3y ago
        I thought so too, but lately I have heard and read accounts akin to a lot of what happened in late WW2 with regards to radar technology was highly classified and much didn't enter the history books. Pilots shooting and nudging definitely happened but likely other, more advanced stuff happened too. The germans had fully automatic radar controlled flak guns.
- WalterBright 3y ago
  I'm talking about a land based system to defend military bases from drone attack, not sea borne vessels.

wolverine876 3y ago

If they can't see the target, how do they shoot missiles at it? I've wondered the same as the GP: Why not just send a wall of metal at the drone from one of these things? If not that, why not traditional anti-aircraft fire, with projectiles that explode in shrapnel clouds?

ethbr1 3y ago
> Why not just send a wall of metal at the drone from one of these things? If not that, why not traditional anti-aircraft fire, with projectiles that explode in shrapnel clouds? If this had been the 1950s or early 60s, every advanced military on the planet would have been able to do exactly that. However, both aircraft (MiG-19+) and missiles were speeding up. At some speed, it becomes impractical to solve a high-speed aircraft or missile problem with a gun. [0] Consequently, development from the 70s on turned to missiles capable of dealing with these threats. Which left the only remaining systems mostly consequences of failure to upgrade (e.g. the German Gepard). As the saying goes, history doesn't repeat itself, but it rhymes... [0] See: M19 (1945) > M42 (1953) > MIM-46 (1960-63, cancelled) > M-163 (1965) > MIM-72 (1967) https://en.m.wikipedia.org/wiki/M19_Multiple_Gun_Motor_Carriage https://en.m.wikipedia.org/wiki/M19_Multiple_Gun_Motor_Carri... https://en.m.wikipedia.org/wiki/M42_Duster https://en.m.wikipedia.org/wiki/M42_Duster https://en.m.wikipedia.org/wiki/MIM-46_Mauler https://en.m.wikipedia.org/wiki/MIM-46_Mauler https://en.m.wikipedia.org/wiki/M163_VADS https://en.m.wikipedia.org/wiki/M163_VADS https://en.m.wikipedia.org/wiki/MIM-72_Chaparral https://en.m.wikipedia.org/wiki/MIM-72_Chaparral
- WalterBright 3y ago
  The drones used by terrorists are homemade and slow moving.
  - ethbr1 3y ago
    But those weren't the primary threat military defense of ~1965-2020 was designed against. (Higher then) Lower, faster, and/or stealthier were the worries. And aside from the economically-mobilized war that Ukraine is fighting (and Russia is gradually shifting to), it's unclear if capability or cost need to be optimized. For every conflict economically less than that, capability wins. I expect the FPV quadcopter grenade-on-a-drone solution will be looked back on like the Toyota Hilux tactical -- effective when introduced, but superceded and dominated by specialized systems produced by military industry.