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Comment by js2 | Hacker News Reader

It apparently ran out of TEA-TEB ignition fluid, not fuel:

https://space.stackexchange.com/questions/15403/why-is-tea-t...

I can't find any info on how much TEA-TEB is carried on-board, only that it's ground supplied for initial launch with the on-board TEA-TEB being used only for restarts.

(I'm not even an amateur rocket scientist: I just googled all this.)

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If I'm not mistaken, the SR-71 and A12 had enough TEB for 15 restarts. After doing an aerial refueling, they had to use TEB to get back to afterburner.

They also had to use TEB to re-light after an unstart [1]. I think 15 is abount right but it seems like a very small margin to deal with considering how common unstarts were.

[1]: https://en.wikipedia.org/wiki/Unstart

I've read about unstarts before and never got the impression that the engine in question stopped. It was the shockwave configuration at the inlet that had to be "restarted"?

Yes I believe that is correct but one consequence of an intake unstart in a J58 is that the afterburner will also stop functioning. I'm not sure what the proper term is when an afterburner stops producing thrust. Maybe flame out?

Regardless, this was the cause of the violent yaw/roll action associated with an unstart (loss of thrust). When the intake was reconfigured the afterburner had to be re-lit and in a J58 this requires TEB. So while TEB was not used to correct the unstart it still had to be used after an unstart.

Once they learned about that they worked around unstarts with software to control the engine spikes to keep the shockwave inside.

Yes, unstarts became less common but they still happened.

Which was like a pint and a half. Pretty powerful stuff.

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