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Vantablack is very dark, absorbing 99.965% of light. I've also heard it absorbs waves beyond the visible spectrum.

Does this mean planes painted with Vantablack would be invisible to radar?

If yes, would stars or clouds affect the plane's stealth? Or will it be completely hidden no matter what?

I'm looking for real-world science—only handwaving the difficulty of getting a plane painted in Vantablack.

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Radar operates at about 50 cm wavelength.

Vantablack reflectivity spectrum shows 2% reflectivity at 25 micron, and rising.

So my answer would be no.

There are special paintings developed to minimize radar reflection, and they are used on stealth planes. For obvious reasons they are not advertised in the hardware shops, so it's hard to find more info on them.

enter image description here

Clouds and stars would reveal its presence, because the plane (regardless of its surface layer) would cover them, therefore from any given point one would see a moving black spot on the background of clouds/stars (unless the plane is flying behyond the clouds)

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  • $\begingroup$ Almost word for word what I had $\endgroup$ Apr 5, 2017 at 4:38
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    $\begingroup$ 2% sounds good (but presumably isn't?). Do you have any information on what reflectivity would be sufficient? $\endgroup$ Apr 5, 2017 at 14:20
  • $\begingroup$ @RichardTingle, it's not just the painting reflectivity, but also the geometry of the surface to play a role. What I find online states that radar absorbing paintings and materials are based on a dispersion of ferritic particles, which convert the radar energy into heat (like any pizza dish for microwave) $\endgroup$
    – L.Dutch
    Apr 5, 2017 at 16:06
  • $\begingroup$ When you say "special paintings" do you mean paints, patterns, or something else? $\endgroup$
    – mattliu
    Apr 6, 2017 at 7:18
  • $\begingroup$ @mattliu, I mean specially developed paints $\endgroup$
    – L.Dutch
    Apr 6, 2017 at 7:46
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No. Radar uses microwaves, which are orders of magnitude longer in wavelength. Short fibers (like the nanovelvet you mentioned) will be invisible to the radar. Perhaps some engineered nanotube or graphene solution would work, but it will be designed as an antenna for that sized wave.

It would not be velvet-like, as the shag would be several inches long. A shaggy plane is not good!

Instead, the nanotubes would be threads parallel to the skin of the plane. To handwave, explain how the conductive fibers act as antennas and that dumps the energy into a graphene substrate whose resonance is monitored in real-time and actively dampened. That way incoming energy is absorbed and not re-radiated.

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    $\begingroup$ "A shaggy plane is not good!" <- Laughing. Out. Loud. $\endgroup$
    – AndreiROM
    Apr 5, 2017 at 12:58
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    $\begingroup$ Relatedly, a good plane is not shaggy. $\endgroup$ Apr 5, 2017 at 13:56
  • $\begingroup$ Hmm, bats and bumblebees seem to fly just fine. Of course, that's on a very different scale, and in any case neither of those actually have hair on their wings, just on their body. But I do wonder... (That said, if you did manage to get a hairy plane to fly, presumably the airflow would make most of the hair lie pretty flat along the surface, anyway.) $\endgroup$ Apr 5, 2017 at 17:54
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    $\begingroup$ Bumblebees play a different game than planes do. They're not invested in moving through the air quickly, and so air friction isn't nearly as big a deal for them. Bats have hair, but the hair is aligned to lie flat when flying, and thus doesn't increase friction all that much. Additionally, checking out the shaggier species of bats, it appears that they tend to be slow fliers. $\endgroup$
    – Ben Barden
    Apr 5, 2017 at 21:03

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