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During Jettisonable Emergency Escape Head Section abort mode, the head section of the rocket is separated and pulled away by OGB SAS (the escape tower) to safety away from the malfunctioning lower stages.

I didn't find at which point the separation occurs. In the video the flames of SAS completely obscure the craft. Neither the schematics nor the article on Wikipedia make it clear. Does the abort mode separate the Stage 3 (3-module Soyuz spacecraft) from Stage 2, or does the separation occur between the Reentry Module and the Service Module of the Soyuz spacecraft?

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  • $\begingroup$ The importance of this question lies in several cases where the service module refused to separate from the reentry module until torn away by aerodynamic forces, and resulting in ballistic reentry and injuries (much more violent deceleration). Had this sort of failure happened during the abort, that would be very bad news. Although the sheer force of thrust of SAS might be able to forcefully break the connection. $\endgroup$ – SF. Jun 25 '18 at 11:42
  • $\begingroup$ I thought those failures were OM-RM hangups, not RM-SM. $\endgroup$ – Russell Borogove Jun 25 '18 at 13:50
  • $\begingroup$ @RussellBorogove: I might have mis-remembered. I'd have to review all the ballistic reentries. BTW, OM-RM separation failure would be similarly bad news. $\endgroup$ – SF. Jun 25 '18 at 13:55
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The Soyuz LES takes only the orbital module and reentry module with it, in order to maximize acceleration away from the launch vehicle. The diagram you link to in the question implicitly confirms this; the proportions of the separated section are such that the OM and RM fit neatly, and there’s no room for the SM.

Per russianspaceweb:

In 1965, developers of the escape system stumbled upon a new serious problem. As it turned out, collision-free separation of the entire payload fairing from the service module of the Soyuz (which remained on the rocket) was practically impossible. After a series of brainstorming sessions, engineers split the payload fairing into top and bottom sections. In the emergency, the top section would fly away with the escape rocket and the crew compartments, while bottom section, surrounding the service module, would remain on the rocket.

enter image description here

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  • $\begingroup$ There's a fairly good diagram here $\endgroup$ – Jack Jun 25 '18 at 13:21

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