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Sep 26, 2016, 10:38 PM
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Raptor engine analysis


Predictions for Musk night 2016: The BFR will be a single core equivalent of the Falcon heavy, with 9 Raptors. It'll be the same size as New Bezos, but have a reusable 2nd stage. It'll have a 3 core version outputting 15 million lbs of thrust. The raptor engine will produce 600,000lbs of thrust in the same size as the Merlin & a fraction of the size of the RS-25 which made 400,000lbs of thrust.


It'll put an object 75% as large as the shuttle in LEO. It'll use multiple launches for the MCT, fuel, & the permanently space based component.


The rest of the architecture will be equivalent to Andy Weir's vision. The mane focus will be the unveiling of the big rocket, since Andy Weir's vision is familiar to everyone.


It's the largest methane engine ever tested. That alone should have made more headlines than year 50 of race riots. As usual, the engine was heavily obscured in the test photos. It looked much smaller than past 600,000lb thrust engines, but Musk has a history of getting more thrust from the least weight than anyone else.


There's no obvious gas generator exhaust like there was on the Merlin, confirming it's the staged combustion cycle promised earlier.


Musk said it's the same size as the Merlin, but making 3x more thrust from a tripled chamber pressure. Based on photos of the Merlin next to construction workers, the engine under test is indeed the full size version. They're both slightly smaller in diameter than a handrail. The nozzle diameter is clearly visible in the flame.


It's quite unusual for such a powerful engine to be tested horizontally, but they might have figured out a way to do it. The test stand can be a lot smaller. It only took a year to go from an initial test of the Raptor preburner to running a complete engine with nozzle at an undisclosed thrust. It would have taken NASA 10 years to do the same thing. NASA would have done many tests without the nozzle. SpaceX obviously stepped up their simulation game.


By all accounts, the Raptor has but 1 purpose: to send humans to Mars. It has a secondary purpose as a replacement for the RD-180, if the BE-4 doesn't come through. It's the largest investment singularly focused on human colonization of another planet.
Last edited by Jack Crossfire; Sep 26, 2016 at 11:36 PM.
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Oct 01, 2016, 01:32 PM
Master Prop Breaker
Wow! Amazing power from such a small engine, methane/oxygen beating hydrogen/oxygen! The development process seemed short in comparison to the "big boys" as well. Something to be said about the private space companies vs the public/private contract cost plus model.

What blows my mind is that NASA's SLS will still be using the RS-25 instead of something like this. The RS-25's will then just fall in the sea! Basically, the SLS is obsolete before it's been built/launched! Granted, these new developments came after the SLS was designed but still the SLS design seems wasteful from the start. IMO they should have just used a modified existing EELV to get quick access instead of relying on Russia for access to space. While using the EELV as a stopgap, NASA could design something reusable. Maybe I'm missing something.

You're right, this should get more attention. Unfortunately, most in this country are more interested in things like the kardashians or the latest rap song.


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