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Flat Earth Media / Misconception: Earth's rotation cannot be detected (accidentally this time)
« on: June 24, 2019, 08:07:32 PM »
On December 14 1966, during the Space Race portion of the Cold War, an unmanned Soviet rocket failed to launch when one of the engines didn't light. Automatic systems reacted, stopping the launch and achieving a safe shutdown of the running engines. 27 minutes later, while ground crews were preparing to replace the igniters on the failed engine, the capsule's emergency escape system activated, launching the capsule off the top of the rocket. This unfortunately set fire to the rocket stack, which unsurprisingly resulted in an explosion, total loss of the rocket, and months of repair to the launch complex.
What does this have to do with the earth's rotation? Well, the capsule has gyros which measure the orientation of the capsule, and one of the things that triggers the escape system is if the capsule's orientation deviates from the expected orientation at any point in the ascent portion of launch. Since the system knew that the rocket was still on the pad, it expected it to remain vertical. However, the gyros were detecting the rocket slowly pitching away from the vertical position recorded at T minus zero vertical due to the earth rotating the rocket eastward. Once it got close to 7° from "vertical" the system became vulnerable to small vibrations pushing it past the trigger point, which seems to have happened when crews returned the service gantries to the service position. The escape system was not shut down when the launch aborted, and that is by design: in a manned mission launch abort, you still want that system live in case the rocket starts to actually fall over.
What does this have to do with the earth's rotation? Well, the capsule has gyros which measure the orientation of the capsule, and one of the things that triggers the escape system is if the capsule's orientation deviates from the expected orientation at any point in the ascent portion of launch. Since the system knew that the rocket was still on the pad, it expected it to remain vertical. However, the gyros were detecting the rocket slowly pitching away from the vertical position recorded at T minus zero vertical due to the earth rotating the rocket eastward. Once it got close to 7° from "vertical" the system became vulnerable to small vibrations pushing it past the trigger point, which seems to have happened when crews returned the service gantries to the service position. The escape system was not shut down when the launch aborted, and that is by design: in a manned mission launch abort, you still want that system live in case the rocket starts to actually fall over.