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With reference to the presentation pp 76, where SSME's Augmented Spark Igniter is said to have their flame "On" even after the main combustion chamber ignition, is to prevent the blowback from the combustion chamber

The igniters turn off after 4.4 seconds while the ignition flame continues in order to prevent intermittent and possibly damaging blowback from the main combustion area. This also keeps the system simple and reliable.

Reference to this video, time stamp 1:08, one can find the following plot Launcher space engine test

Its clear that the igniter chamber pressure touches 200 psi. Then main chamber ignition happens at around T+1s. It appears like they are shutting down their torch igniter and the subsequent pressure rise at the igniter chamber is basically the blowback from the combustor itself

How are they [Launcher] managing to avoid/withstand the blowback from the combustor as mentioned in the SSME presentation?

Launcher space is having a separate supply of propellants for the igniter. The plumbing diagram for the launcher space is added here.Plumbing schematic

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  • $\begingroup$ As we can see from the curve, the pressure in the igniter is different than that of chamber, but with time it is coming to equilibrium with the chamber itself. So, in my opinion, the igniter design will be done considering all this stuff. $\endgroup$ – Amar Nov 20 '18 at 16:38
  • $\begingroup$ @OrganicMarble about the propellant supply to the turbopump's ASI that starts the turbine? They sure are not pump fed! $\endgroup$ – karthikeyan Nov 21 '18 at 5:16
  • $\begingroup$ @OrganicMarble,"How are they [Launcher] managing to avoid/withstand the blowback from the combustor as mentioned in the SSME presentation?" I guess, this was there even before the edit. $\endgroup$ – Vasanth C Nov 21 '18 at 13:33
  • $\begingroup$ Is Launcher a company? I thought it was a noun. OK, retracting close vote if not asking about SSME and deleting all SSME related comments. $\endgroup$ – Organic Marble Nov 21 '18 at 13:36
  • $\begingroup$ @OrganicMarble, Oh, sorry for the incomplete description. And, yeah, Launcher space is a company. $\endgroup$ – Vasanth C Nov 21 '18 at 13:40

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