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> (context: I used to be involved in the design of military radar systems for the Dutch navy) […] Most "stealth" aircraft are actually fairly visible from other

> (context: I used to be involved in the design of military radar systems for the Dutch navy) […] Most "stealth" aircraft are actually fairly visible from other directions. Is that different than ships, which in recent years/decades have tended to look a certain way (a 'finite' number of fixed angles): * https://en.wikipedia.org/wiki/Knud_Rasmussen-class_patrol_vessel https://en.wikipedia.org/wiki/Knud_Rasmussen-class_patrol_ve... * https://en.wikipedia.org/wiki/Absalon-class_frigate https://en.wikipedia.org/wiki/Absalon-class_frigate Do ships have to have a low return (?) at more angles?

WJW 1y ago
Ships like that are typically optimized to look small from "low" angles, ie from the perspective of other surface combatants and sea skimming anti ship missiles. The large flat surfaces are not so much used to reduce RCS by themselves, but mostly to reduce instances of "corner reflectors" like hatches and exposed cranes the like, which can have a RCS many times larger than their physical size due to their shape. See also the "Reduction" section on Wikipedia in the article about Radar Cross Section: (https://en.wikipedia.org/wiki/Radar_cross_section#Purpose_shaping https://en.wikipedia.org/wiki/Radar_cross_section#Purpose_sh...).
- throw0101b 1y ago
  Would airborne radar be better able to find ships with these designs (at least relatively speaking)?
saltcured 1y ago
As I recall, the faceted look of the early stealth aircraft was said to be a practical matter. It reduced the complexity of modeling the reflections during the design process. So with additional computational complexity, they could go back to smooth surfaces in later designs. I imagine there are similar issues with ship design. Since these things are wavelength specific, you probably have a bigger computational problem for a bigger vessel. You can't just solve for the design on a miniature and scale it up to build it.
- Animats 1y ago
  > I imagine there are similar issues with ship design. The U.S. Navy built some stealthy ships.[1][2] But they were very expensive. It seems to have been a dead end not worth the trouble. There are so many sensors, shipborne, airborne, spaceborne, and onshore, that trying to hide a slow moving warship isn't likely to work against a peer opponent. [1] https://en.wikipedia.org/wiki/Sea_Shadow_(IX-529) https://en.wikipedia.org/wiki/Sea_Shadow_(IX-529) [2] https://en.wikipedia.org/wiki/USS_Zumwalt https://en.wikipedia.org/wiki/USS_Zumwalt
  - saltcured 1y ago
    Yes, imagine if air search radar was good enough to see the "wake" of the aircraft so that even if the plane was invisible you could just locate and track its effect on the atmosphere...

WJW 1y ago

Ships like that are typically optimized to look small from "low" angles, ie from the perspective of other surface combatants and sea skimming anti ship missiles. The large flat surfaces are not so much used to reduce RCS by themselves, but mostly to reduce instances of "corner reflectors" like hatches and exposed cranes the like, which can have a RCS many times larger than their physical size due to their shape. See also the "Reduction" section on Wikipedia in the article about Radar Cross Section: (https://en.wikipedia.org/wiki/Radar_cross_section#Purpose_shaping https://en.wikipedia.org/wiki/Radar_cross_section#Purpose_sh...).

throw0101b 1y ago
Would airborne radar be better able to find ships with these designs (at least relatively speaking)?

saltcured 1y ago

As I recall, the faceted look of the early stealth aircraft was said to be a practical matter. It reduced the complexity of modeling the reflections during the design process. So with additional computational complexity, they could go back to smooth surfaces in later designs. I imagine there are similar issues with ship design. Since these things are wavelength specific, you probably have a bigger computational problem for a bigger vessel. You can't just solve for the design on a miniature and scale it up to build it.

Animats 1y ago
> I imagine there are similar issues with ship design. The U.S. Navy built some stealthy ships.[1][2] But they were very expensive. It seems to have been a dead end not worth the trouble. There are so many sensors, shipborne, airborne, spaceborne, and onshore, that trying to hide a slow moving warship isn't likely to work against a peer opponent. [1] https://en.wikipedia.org/wiki/Sea_Shadow_(IX-529) https://en.wikipedia.org/wiki/Sea_Shadow_(IX-529) [2] https://en.wikipedia.org/wiki/USS_Zumwalt https://en.wikipedia.org/wiki/USS_Zumwalt
- saltcured 1y ago
  Yes, imagine if air search radar was good enough to see the "wake" of the aircraft so that even if the plane was invisible you could just locate and track its effect on the atmosphere...