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I learned not too long ago that the reason the F-117 looks so much like a low-poly model is because the computers available at the time that they used to design

I learned not too long ago that the reason the F-117 looks so much like a low-poly model is because the computers available at the time that they used to design it could only handle radar profile calculations for low-poly models.

praetor13 4y ago
There's a great book called "Skunk Works" by Ben Rich (head of the F-117 project) that goes into the development. It's amazing what they were able to accomplish with so little computing power.
- FredPret 4y ago
  I loved that book. They started off with nothing but slide rules and large brains. Incredible.
- SkyMarshal 4y ago
  /second that book, one of the best on advanced aviation and aerospace engineering.
mysterydip 4y ago
I thought it was because the stealth tech was based on faceting. This deflects the majority of radar energy directed at it so it doesn't return to the source to be detected.
- kataklasm 4y ago
  You've got cause and effect flipped. The method of faceting or scattering from even, panelled surfaces is an effect of the root cause, namely the computer's inability to compute more complex radar profiles. You can read more about this in Ben Rich's book 'Skunk Works', the story about his time as the director of Lockheed Martin's Advanced Development Projects, informally called Skunk Works. Great read!
  - perliouhs 4y ago
    > You've got cause and effect flipped. That's simply not true. Round surfaces scatter in all directions, flat surface scatter only in 1 direction of your choosing. For low RCS (Radar Cross Section) paneled surfaces are infinitely better, regardless of computer simulation capabilities.
    - iancmceachern 4y ago
      Maybe better, but not infinity better. If it were infinity better then the B2 wouldn't be stealth (it has not a single flat panel)
    - SlickNixon 4y ago
      > It's simply not true Of course it's true. Modern stealth aircraft have curves a plenty. This is an extremely confident reply given that's it's to somebody who's referencing the book by the guy who built the thing.
    - littlestymaar 4y ago
      > Round surfaces scatter in all directions, flat surface scatter only in 1 direction of your choosing. But with the low-poly approach you end up with sharp edges which diffract the waves in all direction… The fact that no more recent stealth plane have the same shape should be a good indication that this was in fact due to the technical limitation of the time (And btw, who are you to contradict the actual designer of the plane on that topic ?!)
  - HPsquared 4y ago
    A flat surface is less likely to reflect to the source. Think of shining a flashlight at a polished metal object. If the object is smoothly curved and convex, there will always be some point on the surface at just the right angle to reflect the light beam into your eyes. On the other hand consider a flat mirror (at a long distance) or a faceted object with a small number of facets and sharp edges: it's unlikely that any of the facets is correctly aligned to reflect the light to your eyes. A shape with fewer angles ("low-poly") has a lower probability of giving a visible reflection. Modern stealth appears to work the same way: surfaces and edges are aligned along a minimal number of angles to reduce the effective number of "facets". See the shape of the B-2 for example, the leading and trailing edges are at the same angles.
- barkingcat 4y ago
  It was based on faceting because that's all the computers at the time could handle. It's like saying that 3d graphics lighting can only be done by rasterized rendering. Of course, now that we have enough GPU processing power, we can also use ray tracing. In time, all light calculations/shadow calculations will be done with ray tracing, but for now, that's unimaginable because ray tracing runs slowly on current hardware.
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dboshardy 4y ago
Not quite. From the incredible Skunk Works: "Ufimtsev has shown us how to create computer software to accurately calculate the radar cross section of a given configuration, as long as it's in two dimensions," Denys told me. "We can break down an airplane into thousands of flat triangular shapes, add up their individual radar signatures, and get a precise total of the radar cross section." Why only two dimensions and why only flat plates? Simply because, as Denys later noted, it was 1975 and computers weren't yet sufficiently powerful in storage and memory capacity to allow for three-dimensional designs, or rounded shapes, which demanded enormous numbers of additional calculations. The new gneeration of supercomputers, which can compute a billion bits of information in a second is the reason why the B-2 bomber, with it's rounded surfaces, was designed entirely by computer computations. Denys's idea was to compute the radar cross section of an airplane by dividiing it into a series of flat triangles. Each triangle had three separate points and required individual calculations for each point by utilizing Ufimtsev's calculations. The result was called "faceting"--creating a three-dimensional airplane design out of a collection of flat sheets or panels, similar to cutting a diamond into sharp-edged slices.
- moralestapia 4y ago
  ??? Yes quite? Your text completely supports GP's statement.
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praetor13 4y ago

There's a great book called "Skunk Works" by Ben Rich (head of the F-117 project) that goes into the development. It's amazing what they were able to accomplish with so little computing power.

FredPret 4y ago
I loved that book. They started off with nothing but slide rules and large brains. Incredible.
SkyMarshal 4y ago
/second that book, one of the best on advanced aviation and aerospace engineering.

mysterydip 4y ago

I thought it was because the stealth tech was based on faceting. This deflects the majority of radar energy directed at it so it doesn't return to the source to be detected.

kataklasm 4y ago
You've got cause and effect flipped. The method of faceting or scattering from even, panelled surfaces is an effect of the root cause, namely the computer's inability to compute more complex radar profiles. You can read more about this in Ben Rich's book 'Skunk Works', the story about his time as the director of Lockheed Martin's Advanced Development Projects, informally called Skunk Works. Great read!
- perliouhs 4y ago
  > You've got cause and effect flipped. That's simply not true. Round surfaces scatter in all directions, flat surface scatter only in 1 direction of your choosing. For low RCS (Radar Cross Section) paneled surfaces are infinitely better, regardless of computer simulation capabilities.
  - iancmceachern 4y ago
    Maybe better, but not infinity better. If it were infinity better then the B2 wouldn't be stealth (it has not a single flat panel)
  - SlickNixon 4y ago
    > It's simply not true Of course it's true. Modern stealth aircraft have curves a plenty. This is an extremely confident reply given that's it's to somebody who's referencing the book by the guy who built the thing.
  - littlestymaar 4y ago
    > Round surfaces scatter in all directions, flat surface scatter only in 1 direction of your choosing. But with the low-poly approach you end up with sharp edges which diffract the waves in all direction… The fact that no more recent stealth plane have the same shape should be a good indication that this was in fact due to the technical limitation of the time (And btw, who are you to contradict the actual designer of the plane on that topic ?!)
- HPsquared 4y ago
  A flat surface is less likely to reflect to the source. Think of shining a flashlight at a polished metal object. If the object is smoothly curved and convex, there will always be some point on the surface at just the right angle to reflect the light beam into your eyes. On the other hand consider a flat mirror (at a long distance) or a faceted object with a small number of facets and sharp edges: it's unlikely that any of the facets is correctly aligned to reflect the light to your eyes. A shape with fewer angles ("low-poly") has a lower probability of giving a visible reflection. Modern stealth appears to work the same way: surfaces and edges are aligned along a minimal number of angles to reduce the effective number of "facets". See the shape of the B-2 for example, the leading and trailing edges are at the same angles.
barkingcat 4y ago
It was based on faceting because that's all the computers at the time could handle. It's like saying that 3d graphics lighting can only be done by rasterized rendering. Of course, now that we have enough GPU processing power, we can also use ray tracing. In time, all light calculations/shadow calculations will be done with ray tracing, but for now, that's unimaginable because ray tracing runs slowly on current hardware.

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dboshardy 4y ago

Not quite. From the incredible Skunk Works: "Ufimtsev has shown us how to create computer software to accurately calculate the radar cross section of a given configuration, as long as it's in two dimensions," Denys told me. "We can break down an airplane into thousands of flat triangular shapes, add up their individual radar signatures, and get a precise total of the radar cross section." Why only two dimensions and why only flat plates? Simply because, as Denys later noted, it was 1975 and computers weren't yet sufficiently powerful in storage and memory capacity to allow for three-dimensional designs, or rounded shapes, which demanded enormous numbers of additional calculations. The new gneeration of supercomputers, which can compute a billion bits of information in a second is the reason why the B-2 bomber, with it's rounded surfaces, was designed entirely by computer computations. Denys's idea was to compute the radar cross section of an airplane by dividiing it into a series of flat triangles. Each triangle had three separate points and required individual calculations for each point by utilizing Ufimtsev's calculations. The result was called "faceting"--creating a three-dimensional airplane design out of a collection of flat sheets or panels, similar to cutting a diamond into sharp-edged slices.

moralestapia 4y ago
??? Yes quite? Your text completely supports GP's statement.
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