In the 1960s, the B-52 bomber could navigate by the stars.
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Inside the Angle Computer, a star pointer corresponds to the position of the star on the celestial sphere. Gears move the pointer to match the star's coordinates (called the declination and Local Hour Angle).
The back of the Angle Computer has devices called synchros that read out the star's position relative to the aircraft. At the bottom, motors drive the mechanism.
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The back of the Angle Computer has devices called synchros that read out the star's position relative to the aircraft. At the bottom, motors drive the mechanism.
This close-up of the Angle Computer shows the complexity of the gears inside. The thicker brass-colored cylinders are differential gears that add two signals using rotations.
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This close-up of the Angle Computer shows the complexity of the gears inside. The thicker brass-colored cylinders are differential gears that add two signals using rotations.
For more on the electromechanical Angle Computer, see my article: https://www.righto.com/2026/04/B-52-star-tracker-angle-computer.html
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff Fantastic!
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R relay@relay.mycrowd.ca shared this topic
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
Amazing but where did they keep they pigeons?
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For more on the electromechanical Angle Computer, see my article: https://www.righto.com/2026/04/B-52-star-tracker-angle-computer.html
@kenshirriff Do you know what accuracy it could achieve?
I saw an interview with WW2 navigator who said he could only determine the location of the airfield to within 5 miles (with a sextant) .. in a bomber over Germany, he was lucky to even find the right town!
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff stuff like this reminds me of 2 things:
1 The Antikytheria mechanism.
2 A short story (by Heinlein I think) I read many years ago, about the problems of building a spacecraft in a civilisation that has not discovered electricity. -
@kenshirriff Do you know what accuracy it could achieve?
I saw an interview with WW2 navigator who said he could only determine the location of the airfield to within 5 miles (with a sextant) .. in a bomber over Germany, he was lucky to even find the right town!
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff very cool
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The "Astro Tracker" was the heart of the celestial navigation system. The 4-inch clear bubble stuck out from the top of the aircraft to view the stars. Inside, a telescope and photomultiplier tube tracked a star, steered by motors and prisms.
@kenshirriff Wait is this the inspiration for the R2 units plonked in the back of the Tie Fighters in Star Wars?
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff Welcome to the root physics of gyroscopic measures; brought to you by Spin Physics.
Milankovitch would be proud.
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@kenshirriff Welcome to the root physics of gyroscopic measures; brought to you by Spin Physics.
Milankovitch would be proud.
@numodular Although this unit looks like a gyroscope, it is not at all a gyroscope. There is nothing spinning.
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@kenshirriff Do you know what accuracy it could achieve?
I saw an interview with WW2 navigator who said he could only determine the location of the airfield to within 5 miles (with a sextant) .. in a bomber over Germany, he was lucky to even find the right town!
@vk2bea They say that the accuracy was within 0.1 degree.
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@vk2bea They say that the accuracy was within 0.1 degree.
@kenshirriff .. so about 11 km at 34 degrees north.
I guess with a 10 megaton bomb, it's good enough. If Dr Strangelove is anything to go by, the final bombing run used radar
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@numodular Although this unit looks like a gyroscope, it is not at all a gyroscope. There is nothing spinning.
@kenshirriff I shall update the media to stop the spin, and send the astronauts back to the moon
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff @siracusa wasn’t there an SR-71 story about it this not working in the southern hemisphere? Or they couldn’t fit both halves in memory or some such?
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
@kenshirriff is this the same one that was in the SR-71?
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In the 1960s, the B-52 bomber could navigate by the stars. Celestial navigation requires spherical trigonometry, so an analog Angle Computer solved these equations electromechanically. Let's look inside...
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@kenshirriff is this the same one that was in the SR-71?
@dnaunton The SR-71 used a different system, the NAS-14V2 astroinertial navigation system. Nortronics built the SR-71 system and Kollsman built the B-52 system. The B-52 system is said to have also been used in the Hound Dog cruise missile. A very detailed document on the SR-71 star tracker is here: https://audiopub.co.kr/wp-content/uploads/2021/10/NAS-14V2-ANS-System.pdf
