Faxes From the Far Side (2015) | Hacker News Reader

Faxes From the Far Side (2015)

damninteresting.com

104 pointsnot_a_boat13 comments

> this might have worked were it not for the fact that one of the steel rods in the balloon rigging was 91 centimeters long. US Air Force engineers didn’t realize it at the time, but 91 centimeters happened to correspond to one of the frequencies used by Soviet early-warning radar. This caused the otherwise inconsequential rod to resonate and glint like a mirror on Soviet radar screens.

This is fascinating. I wonder how unlucky they got - what the tolerance on something like this is, presumably 91.1 cm would still resonate but 96 cm would not?

Also, if a possible failure mode is "if any of the rods in the construction of this stealth device exactly matches the enemy's secret number, the mission will be detected" that seems like it would lead to some very fun design constraints. Are there any examples of designers taking this into account and building a device with every component the same size?

> what the tolerance on something like this is?

They are pretty wide. You can find the answer by looking at some online antenna calculators. Bear in mind that it also depends on the orientation of the rod relative to the incoming wave, and to the polarization of the wave.

Modern stealth aircraft tend to reflect the signal away from the transmitting radar or absorb it. The windows tend to have thin conductive gold layers on them to stop radio waves getting into the cockpit and finding a resonator. Similarly joints on the fuselage are sealed.

However, the design of stealth is limited to a frequency band, normally X-Band (8 to 12GHz, a few inches in wavelength). At a lower frequency, like 1GHz they are not stealthy, which was one reason why an F-117 Stealth fighter was shot down in the late 1990's.

That is 0.995 yards which might be relevant.

Reusing the surveillance film and fax technology for a lunar mission makes this story feel like something out of an episode of James Burke's Connections.

For a moment I thought this was about https://thefarside.com/

And to be fair, Far Side comics would probably fax well.

Damn Interesting feels like the last vestige of the golden age of the Internet. While simultaneously being the best podcast still going today.

Scott Manley has a great video explaining much of this same story: https://youtube.com/watch?v=YDs8rz7pRLQ

A previous thread from 2015: https://news.ycombinator.com/item?id=10463922

Thanks! Macroexpanded:

Faxes from the far side of the moon - https://news.ycombinator.com/item?id=10463922 - Oct 2015 (35 comments)

It's worth remembering that in the phrase "dark side of the moon", "dark" means "hidden" not "unlit". The dark side gets the same amount of light as the near-facing side. See dark OED definition II.11.a. (1532–): "Hidden from view or knowledge; concealed; kept secret." https://www.oed.com/dictionary/dark_adj

You might want to remind Bill Nelson of that next time he talks to Congress

I suspect he's heard by now. :-)

But I think it's worth clarifying why certain phrases are used. Saying "there is no dark side of the moon" is also wrong.. once you realize that "dark" has multiple meanings. And since the moon has been around for a while, there are some very old phrases relating to it.

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