PURE rocket SSTO

[Kryten]

Oxidiser-rich is not pure. And further, quickly doing research on Encyclopaedia Astronautica, I found only one Russian engine that exceeded the shuttle's LOx ratio, achieving 6.2. The majority matched, at 6, and maybe a third were lower, most around 5.8, some as low as 4.2. Running pure for hydrogen would require a ratio of 8, which would have to be exceeded to run oxygen-rich, meaning no Russian engines did run lean as you suggest.

The high oxidiser-ratio engines he's talking about are all kerolox, not LOX/LH2. Cryogenic engine tech is basically in it's infancy in Russia, they've only flown six times with two engine types.