David Rosenthal: uncertainty

Transcript context

…It's totally wild. This whole thing was built with slide rules. I had a very controversial tweet geta community noted, where I said that it was before the invention of the desktop calculator. It's mostly true. There are technicalities to it, but Kelly and team basically did this thing independently of computers and calculators, and figured out all the unbelievable aero dynamism stuff about it. Of course, there's also the first stealth airplane. That's the other thing that we didn't talk about. The reason this thing wasn't detected on radar for four years is because they figured out how to fly and start to evade radar. Yup. I don't know the details of stealth with the Blackbird. I imagine a big part of that was the height, the altitude, and the speed of it. It's not that, I don't think. It's more around the shape because radar will just go unimpeded out into space. There are famous stories about detecting where people's radar transmitters are by bouncing them off the moon, and figuring out the patterns of bouncing off the moon. It's more, I think, that the SR-71's bottom was one of the first airplanes with a flat bottom rather than a rounded fuselage. Imagine I'm shooting a set of waves at a round sphere in front of me. Some of those waves are going to bounce back because some of that sphere is exactly perpendicular to me broadcasting it. There's one particular point that's exactly perpendicular, and I can tell the radius of the thing by how I'm detecting waves that are bouncing back at me. If it's all flat, there's only one very specific angle for which I can shoot waves at it, where I'm perfectly perpendicular, and every other angle that I shoot radar at it, it's going to bounce off and not come back to me as a transmitter. You'd need transmitters coding all over the earth to figure out where all those waves are bouncing. By making the bottom flat, they made it so that if it was truly flat, then there's only one exact moment in time that a given radar transmitter is useful. They also did a whole bunch of work around making the rivets exactly flush with the skin. It basically didn't have a whole bunch of rounded parts that could risk bouncing radar waves back at the transmitter or receiver.…

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