Elon Musk

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May 13
@elonmusk
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Replying to @elonmusk @NASASpaceflight and @SpaceX
Raptor chamber wall might have the highest heat flux of anything ever made
Chris Bergin - NSF
@NASASpaceflight
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Can Raptor 3 can be a drop-in replacement for Raptor 2, or will the vehicles require changes to cater for Raptor 3 engines?

Here's the full firing from the raw pull out of http://nsf.live/mcgregor
1:14 / 1:14
7:29 AM · May 13, 2023 //

Also, Super Heavy is getting very very close to a SRB in terms of thrust density (~1388 vs ~1367kN/m²). Fascinating.

With ~30% higher ISP… meaning ~69% higher power density.

There really is no one close to SX now at making rocket engines. //

I don't want to knock down the SpX engineers working on this thing, if anything, it reminds me of the SSME development. That engine program had its fair share of failures, but, in the end they produced (in my humble opinion) the finest and most reliable rocket engine ever developed (and LH2 powered at that, no small feat), a true pinnacle of U.S. aerospace engineering. Hopefully SpX can rise to that level, because their architecture really needs it. //

Merlin has now exceeded RS-25 in reliability in terms of consecutive successful engines on orbital launch (by about half an order of magnitude). RS-25 had an engine-out on STS-51F on the 19th Shuttle launch, and SpaceX has had more Falcon launches since then without any engines out than the rest of the Shuttle program combined plus had at least 3 times as many engines. (Rs-25 had other hiccups, but I think that’s the only full engine-out? Can’t remember.)

A lot of that Merlin reliability is just the sheer number of engines and number of launches, making more of a difference than any particular feature of the engine, allowing tweaking to improve engine reliability and large manufacturing and test volume that allows quickly achieving really good engine statistics. RS-25 had both clustering and a fairly decent flightrate in its favor, but not as much as Merlin.