Wikipedia has a stub article on the loss of the Soyuz 7K-OK No.1 test flight in 1966-12-14, but this part doesn't make sense to me:

However, once the Soyuz rocket's engines ignited, they did not operate at full power and didn't produce enough force to lift the rocket up, causing it to stay on the launch pad.

30 minutes later:

There were only thought to be three ways to trigger the LES [Launch Escape System], but there was in fact a fourth, which was triggered by disconnecting the rocket from external power and receiving a launch signal (which the system interpreted as the start of a vertical launch without any other signals by the inertial system), but the rotation of the earth causing a deviance of more than eight degrees from the initial starting orientation, which was an abort criterion.

How was the orientation measured, if not relative to the Earth's gravity, which does not change with Earth's rotation? I find no more information about this accident, which is said to have killed "all" ground staff since the unexpected LES activation put the whole rocket on fire (the Wiki list below says only one fatality).

I've only found this paper source "Siddiq (2000), p. 874."

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    $\begingroup$ That's one lip-smacking, eye-boggling reference. Made me salivate when I followed it to the source, and the Appendix at the end listing NASA SP history reports. Much rich material to read :-). $\endgroup$ Dec 4, 2016 at 14:04

1 Answer 1


Rocket guidance systems generally use a fixed inertial platform based on gyroscopes to determine their orientation in space; an accelerometer solution would be useless to determine orientation (though helpful for position determination) as soon as the rocket was in motion.


Once operating, the platform's orientation would be fixed in space, while the rocket, clamped to a rotating planet, turned beneath it.

The "guidance is internal" call heard shortly before liftoff in American rocket launches marks the time at which the platform calibration is stopped and it becomes free to rotate.

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    $\begingroup$ Aah, of course! They do measure the rotation of the Earth, like Foucault's pendulum. When launch was attempted, the power that normalized the gyroscopes was cut. And literally Soyuz' internal sundial started its own countdown to failure. And this was how the Soyuz rocket generation started out. $\endgroup$
    – LocalFluff
    Sep 13, 2016 at 16:10
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    $\begingroup$ It wasn't that they were unpowered -- they would have been on battery power -- but that switchover to internal power plus the launch signal triggered the release into "free mode". The logic is brilliant; at altitude zero, being 8 degrees off the vertical is excellent grounds for a hasty abort. $\endgroup$ Sep 13, 2016 at 16:44
  • $\begingroup$ A rocket attached to the ground for 30 minutes at the equator would only show 7.5 degrees deviation from vertical if its inertial measurement platform were functioning properly. At higher latitudes, it would show less, commensurate with the cosine of the latitude. $\endgroup$
    – Tristan
    Feb 27, 2017 at 20:41
  • $\begingroup$ @Tristan: How did you come up with that? At equator, it does 360 degrees in 24h, that's 30 degrees per hour, 15 per 30 minutes. At intermediate latitudes like Baikonur 8 degrees per 30 minutes seem about right. $\endgroup$
    – SF.
    Feb 27, 2017 at 21:22
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    $\begingroup$ "About 30 minutes after the aborted launch, the launch escape system suddenly activated." $\endgroup$ Feb 27, 2017 at 22:48

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