Autonomous car

The New BMW X6 Has Almost Completely Light-Absorbing ‘Vantablack’ Paint

A good — no, great — show car is one that is beyond impractical and approaches the impossible (to execute). Think of a car with a 375/20R21 tire with a 20-aspect ratio, the sidewall one-fifth as high as the tire is wide: Pebbles, not just potholes, would break the rim. BMW just raised the bar for amazing concept vehicles with the BMW X6 Vantablack. It absorbs 99-plus percent of light. There are virtually no reflections. Seen against a black background, the car appears two-dimensional.

The “paint” is actually a material made from carbon nanotubes and, BMW says, “it is considered the blackest black in existence.” Vanta is an acronym for “vertically aligned carbon nanotube arrays.” It was created by Surrey NanoSystems of the UK for space and metrology (science of measurements, not meteorology) applications and is, Surrey says, “the darkest material ever measured … reflecting only 0.036 percent of the light that strikes it.” There are versions of Vantablack and the BMW paint job was not quite that absorbent.

What is this thing, Vantablack? Says BMW, which displayed the one-off conceptual car at this months Frankfurt motor show:

Vantablack is not actually a color pigment or a paint, but a coating of carbon nanotubes. These have the property of absorbing incident light almost completely. Against a deep black background, objects coated in Vantablack material seem to disappear, as the perception of spatial depth is lost. This is because the human eye perceives shapes coated in Vantablack to be two-dimensional. …

This show car is destined to remain a one-off because of the enormous difficulty involved in making Vantablack paint suitably durable for everyday automotive use. The car paint needed for the world’s blackest black would also be extremely expensive, not to mention questionable in terms of road safety due to its level on the absorption spectrum. However, the technology is set to be used in laser-based sensor arrangements for driver assistance systems and thus in autonomous driving [including head-up displays – Ed].

Why is it so dark and what does Vantablack look like? According to Surrey Systems:

Light energy striking the Vantablack surface enters the space between the nanotubes and is rapidly absorbed as it ‘bounces’ from tube to tube and simply cannot escape as the tubes are so long in relation to their diameter and the space between them. The near total lack of reflectance creates an almost perfect black surface. To understand this effect, try to visualise [it’s UK spelling] walking through a forest in which the trees are around 3km tall instead of the usual 10 to 20 metres. It’s easy to imagine just how little light, if any, would reach you. …

In truth, it could be said that it is almost impossible to “see” Vantablack as so little light is reflected from the surface. However, the observer’s brain of course tries to make sense of what it is seeing, with the result that some people describe it like looking into a hole! …  The almost total lack of light reflected from the Vantablack surface prevents the eye detecting any surface detail.

The Vantablack coating is used inside telescopes to minimize light reflections. (Maybe that’s how Sarah Palin’s telescope was able to see Russia from her backyard?) It could also have application for high-end camera lenses.

Since so many people are so sure Vantablack is right for some personal pet project, the company issues multiple warnings online: “Vantablack coatings cannot be used by private individuals. If you are interested in Vantablack for a personal project please read our FAQs … we are unable to respond to private email addresses for the following requests: coating a car, motorbike or bicycle; use of the coating in personal art; coating household objects or musical instruments.”

Our take is this may still provide opportunities for ministers, priests, and rabbis to vie for the darkest of vestments if they don’t mind a metallic substrate that crinkles as you walk.

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