> they are using Russian designs Not at all. An important and telling detail: pintle injector is almost never used in Russia, but standard for Merlins. Or you

> they are using Russian designs Not at all. An important and telling detail: pintle injector is almost never used in Russia, but standard for Merlins. Or you can look into gas generator cycle, which isn't used for today's Russian kerosene engines except RD-107 family, which have separate components for turbopumps and pressurization.