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Everyday Astronaut 18 Apr 19
Why did the RS-25 go dual shaft / dual preburner design? It seems like having your fuel-rich preburner next to a LOX pump caused a heck of a head ache in making a crazy seal... so why didn't they go with a common shaft like most other engines?
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Elon Musk 18 Apr 19
Common shaft only works if optimal rpm is similar for fuel & oxidizer
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Elon Musk 18 Apr 19
🚀 propellant grade kerosene (basically, jet fuel) & liquid oxygen are close, but H2 & O2 are not
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Everyday Astronaut 18 Apr 19
Replying to @elonmusk @DJSnM and 2 others
So how does the RL-10 get away with just a single preburner? Is that what the gearbox is for, to step up the pump speed? I think I'm FINALLY grasping this stuff, and the more I learn, the more I appreciate the crazyyyy engineering behind rocket engines 🤯 I 🖤 Rocket scientists
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Ernesto Arigita 18 Apr 19
Don't forget RL-10 has a different engine cycle! It may have to pump both fuel and oxi like any other engine, but it hasn't got a single preburner anywhere and gets the pumping power from the heat taken off the engine with the H2 cooling loop. Neat trick, but limited in thrust.
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Everyday Astronaut 18 Apr 19
Replying to @rune_ea @elonmusk and 3 others
Oh crap. I forgot. It’s the expander cycle isn’t it 🤦‍♂️ I wonder how the RS-27 does it. Time to look that thing up
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Scott Manley 19 Apr 19
I think you mean RS-68, the RS-27 was the Jerold’s engine used in delta II and delta III, the RS-68 powers the Delta IV. It has separate turbopumps for LH2 and LOX, it’s not a closed cycle engine, the exhaust from the gas generator is used to provide thrust for roll control.
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Mike Marriage 19 Apr 19
There must be a family tree of rocket engjnes. Or perhaps the ubiquitous london underground map.
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Scott Manley 19 Apr 19
There's links that can be drawn, it's more like venn diagrams. I know the physics better than a lot of the history.
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Scott Manley 19 Apr 19
It’s a nice diagram, but it’s missing the Thor-Delta evolution
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Tory Bruno 19 Apr 19
Replying to @DJSnM @MikeM_UK_ and 4 others
My paper was only so big. ;)
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Everyday Astronaut 19 Apr 19
Replying to @torybruno @DJSnM and 4 others
Woah this is super cool!!! That sure does have a lot on there, but I'll bet that gets wild if you try and track ALL OF THE ENGINES through out history. That'd be a mess 😄
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Mike Marriage 19 Apr 19
Hmmm. London underground is tricky but ghd map is pretty. How many engines have put things in orbit. What is their lineage. ..... I have seen similarly contrived lineages for pop groups but the key things can be communicated.
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Joe McKirdy 19 Apr 19
Replying to @torybruno @DJSnM and 6 others
Where is the Delta II workhorse.
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Everyday Astronaut 19 Apr 19
Immaculate conception.
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Delay 20 Apr 19
Replying to @torybruno @DJSnM and 5 others
What I'm missing in the diagram is the Merlin 1D. How old is the diagram? Otherwise this is a nice diagram!
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Tory Bruno 20 Apr 19
Replying to @Delay248 @DJSnM and 5 others
A couple of years.
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Tom Benedikt Vorat 20 Apr 19
Replying to @torybruno @DJSnM and 5 others
What does the LM have to do with Falcon 9? I don't get it...
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Tory Bruno 20 Apr 19
Replying to @tom_vorat @DJSnM and 5 others
Very, very expensive to develop a rocket engine from scratch (like BE4). So most engines are derived/evolved from one that already exists.
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