Remember when David Spain bragged outrageously? That was Thursday:
On 2020-05-19 8:34 AM, Jeff Findley wrote:
I'm not 100% sure of the details, that's why I said they're "sources of
hot, gaseous, oxygen and hot, gaseous, methane". They may use the
respective exhaust coming out of the turbines of the turbopumps. One
side would be mostly hot oxygen and the other hot methane. But,
obviously, there would be some combustion products mixed in if they go
that route.

The other route would be to have some sort of heat exchanger and just
gasify the LOX into gaseous oxygen and liquid methane into gaseous
methane.

Honestly, I don't know which way they've chosen.

Jeff


I did a little digging and found this "unofficial" block diagram of a Raptor
with tank pressurant feed-lines shown.

https://upload.wikimedia.org/wikiped...Scheme.svg.png

Nifty; black type on a dark grey background. WiPi's picture of the
Merlin engine didn't have that feature.

If this is correct, it is as I believed, they are bleeding off a small amount
of *uncombusted* pressurized *gaseous* methane and oxygen to pressurize the
tanks. Thus there should be no combustion product involved here.

This diagram doesn't show any heat exchangers unless they are positioned on
the tanks themselves, but I suspect this drawing may be fairly accurate,
because they are feeding pressurized gaseous material. I suspect directly
back into the tanks. They'd get some temperature drop when transitioning to
the gaseous phase. But the key is pressure and just enough to keep the tanks
pressurized during operation.

HTH.

Thanks. That's well worth studying despite the color problems.

/dps

--
"I am not given to exaggeration, and when I say a thing I mean it"
_Roughing It_, Mark Twain