[IcePenguin]

Yep! It's called TEB (Triethylborane). More info here: https://en.wikipedia.org/wiki/Triethylborane

JP-7 has a very high ignition temperature (it was actually used as a coolant/heat sink for the rest of the aircraft), so TEB combusting once it hit the air is used to light the engines.

SR-71s only had a limited amount of TEB to use each flight. I believe it was 13 shots per engine. TEB was used each time the engines were lit and also when afterburners were lit. While the SR-71's routes were built around refueling, the number of TEB shots remaining were the true limiting factor of the SR-71's flight time.

[jazzyjackson]

I don’t know anything about afterburners, if it’s the same fuel as the usual engine, what about it needs to be lit with a lower temperature fuel?

I always assumed afterburners just meant opening the throttle up but there must be more to it

[jabl]

> I always assumed afterburners just meant opening the throttle up but there must be more to it

No, as the name implies it's literally pouring in fuel after the turbine, in the exhaust. The exhaust is hot, yes, but cooler than the combustion chambers (which reside in between the turbine and compressor). So if you have some special fuel that's very hard to ignite then maybe you need some help to get the afterburning started.