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The excellent answers to What are these circular spots on these Ariane V SRB nozzles? tend to indicate that unlike the IV, the Ariane V simply rests on two flat surfaces under the SRBs at launch time, and does not have a lock down mechanism to hold it in place until proper ignition and full thrust can be confirmed.

Those answers contain a lot of information and are worth reading.

Assuming this is the case, what would happen if for some reason one of the SRBs did not ignite at all, or started burning with substantially lower power, say less than 50%, or the nozzle failed promptly? (like this one did at the end of a test)

Question: Would the rocket fail to leave the ground and just sit there and burn, or would the resulting torque tip it over? Or would the auto destruct mechanism blow it up on the pad?

Space Shuttle Almanac tweet Ariane V

above: from this Space Shuttle Almanac tweet linked here. below: cropped from Capcom Espace's ARIANE 5 linked here.

cropped from Capcom Espace's ARIANE 5

uhoh
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  • Related but different: What would have happened if only one Space Shuttle SRB ignited? to which the answer seems to be "everybody dies" in an intentional flight termination explosion. The Ariane V scenario may be substantially different than the Shuttle. – uhoh Aug 09 '19 at 01:54
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    I suspect the only significant difference is that nobody dies. – Russell Borogove Aug 09 '19 at 02:30
  • @RussellBorogove so you think it will tip over (pivot) around a dead SRB, or would it completely leave the pad (assuming it wasn't terminated)? There's no chance that if they shut down the central engine it would just sit there and the one SRB would just burn out? – uhoh Aug 09 '19 at 02:34
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    I really don't know. If one EAP fails to ignite, then either (A) tip over and explode, (B) sit there until one side of the pad melts, then tip over and explode, (C) get unzipped by the range safety system and explode. If one of the EAPs ignites but the nozzle fails promptly, I'd expect significantly asymmetrical thrust, so it goes up off the pad, immediately U-turns, (D) crashes and explodes or (E) gets range-safetied and explodes. I would be astonished if the pad could take the heat of an EAP firing for two minutes. – Russell Borogove Aug 09 '19 at 02:39
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    The best source I can find about the launch table is also from Capcom Espace but it's unfortunately completely French. – GittingGud Aug 09 '19 at 05:38
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    This is something KSP can simulate with great accuracy. – user721108 Aug 13 '19 at 09:37
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    @qqjkztd that's a really great idea! The physics engine would be a much better simulator than the back of an envelope covered in drawings of spherical cows. – uhoh Aug 13 '19 at 09:40

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