Has the wrong knot been tied on a spacecraft? For example, a clove hitch instead of two half-hitches?


  • $\begingroup$ Under what context? I'm not aware of knots being used for anything more complicated than maybe attaching labels to softgoods items. Tying a knot in a rope or cord reduces its load carrying capacity by roughly half, so I don't see it being used much over using cleats or crimps. $\endgroup$ – Tristan Sep 20 '19 at 14:24
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    $\begingroup$ What was the first piece of wood to reach the far side of the Moon? Or the first spacecraft? received several down votes and didn't turn around until I posted the answer myself. If you know the answer, might as well share it. $\endgroup$ – uhoh Sep 20 '19 at 15:09
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    $\begingroup$ Woah, what is the downvote spam here? This is a legitimate question. $\endgroup$ – Magic Octopus Urn Sep 20 '19 at 17:10
  • $\begingroup$ @MagicOctopusUrn Maybe because this is (again) a list type question of the type Has incident X ever occurred?. The number of possible questions of this type is essentially endless and at a certain point no longer interesting. $\endgroup$ – Jan Doggen Sep 20 '19 at 17:37
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    $\begingroup$ @JanDoggen I disagree. The answer is yes or no. A single instance of it makes it yes as he has already shown us. Yes, the interest stops there, but it is fully answered now and doesn't need any other answers as it is "Yes it has happened". OP never asks for a list of times it has happened, just if it has. Also, it seems like it was derived from a specific diagram. $\endgroup$ – Magic Octopus Urn Sep 20 '19 at 19:11

Yes. Apollo command modules had a forward heat shield, which was ejected before landing to expose the parachutes. The forward heat shield itself had its own small parachute, which would help carry the shield away from the command module. Improperly-tied knots on at least 4 command modules could have prevented the small heat shield parachute from being deployed, which in turn could cause the forward heat shield to strike the command module or its parachutes.

An apparent installation error on the forward heat shield mortar umbilical lanyard was found during postflight examination of Apollo 11 in that all but one of the tie-wrap knots were untied. This series of knots secures the tie-wraps around the electrical bundle and functions to break the wraps during heat shield jettison.

The knots should be two closely tied half-hitches which secure the tie-wrap to the lanyard (fig. 16-6). Examination of the Apollo 10 lanyard indicates that these knots were not two half-hitches but a clove hitch (see figure). After the lanyard breaks the tie-wraps , if the fragment of tie wrap pulls out of the knot, the clove hitch knot can untie, thus lengthening the lanyard. Lengthening this lanyard as the umbilical cable pays out can allow transfer of some loading into the umbilical disconnects. Should a sufficient load be transferred to the disconnect fitting to cause shear pins to fail, a disconnect of the forward heat shield mortar umbilical could result prior to the mortar firing. This would prevent deployment of the forward heat shield separation augmentation parachute, and there would be a possibility of forward heat shield recontact with the command module.

Apollo 11 Mission Report, section 16.1.9


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