
SpaceX crushes rocket engine world record during Raptor test - gnarbarian
https://www.teslarati.com/spacex-raptor-engine-crushes-russian-record/
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avmich
Pretty serious achievements. Wonder what is the demonstrated Isp and the
exhaust pressure?

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woodandsteel
Does anyone know what SpaceX did special in designing and building the Raptor
that allows it to reach such a high pressure?

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avmich
There is no problem to reach a big pressure by itself.

There is problem to reach it for this amount of fuel using the same amount of
fuel as energy source. The flow is fixed, so pressure is proportional to pump
power, which is a part of turbine power, which takes energy from that fixed
flow. To get more energy, bigger temperatures are needed - on both fuel-rich
and oxidizer-rich turbines, and that's limited by existing materials.

Of course, there are many complexities with efficiencies, balances (spinning,
two turbopumps), thermal expansions and contractions (LOX is about 90K),
cooling of turbine blades, if any, control of pressure feedbacks (e.g. the
bigger power on turbine - the bigger pressure on pumps, which supplies fuel to
gas generator and then to turbine, so we have a positive reinforcement loop
here)... No, the problem isn't the pressure - it's the pressure given all the
constraints of the leading edge rocket engine.

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woodandsteel
Ok, but that still doesn't answer my question of what specifically SpaceX did
differently. For instance, you said bigger temperatures are needed and that is
limited by existing materials. So did SpaceX invent materials that could stand
a higher temperature?

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gnarbarian
[https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...](https://www.google.com/url?sa=t&source=web&rct=j&url=https://twitter.com/erdayastronaut/status/1130884644717699073%3Flang%3Den&ved=2ahUKEwjp6Zrx3rrrAhW9IjQIHbhADA8Qt9IBMAp6BAgQEAc&usg=AOvVaw0TPftFdEOvYLn-H66PNwOM)

SpaceX has the first flight tested, full flow dual turbopump engine.

As in there are turbopumps for both the lox and methane tanks powered by
burning extra rich mixtures for each pump leaving enough unburnt lox and
methane in the perfect ratio to generate the record primary thrust.

