4 ms·

> 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 reali

> 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?

RachelF 2y ago
> 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.
unwind 2y ago
That is 0.995 yards which might be relevant.

4 ms·

> 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 reali

by dmurray 2y ago

RachelF 2y ago
> 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.
unwind 2y ago
That is 0.995 yards which might be relevant.