How SpaceX’s New Raptor Vacuum Engine Is Different From Previous Raptors (and Other Stuff)

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It’s been a while since I talked about SpaceX’s work on Starship, but in the last month I’ve been most excited by the reveal of the prototype for the Vacuum optimized version of the Raptor engine which is intended for the Starship upper stage.

How Not To Land A Starship:

  1. Spartan J

    another one of Scott’s MANLY videos

  2. Tinkering in Thailand

    interesting and informative post, cheers Scott.

  3. Mike Richards

    Thanks for explaining this so clearly – any chance of a video about these vacuum engine test facilities? I’d love to know how they work and I’m sure there are some big numbers involved!

  4. Julian S

    God I need more of this content right now.

  5. Whole Nuts And Donuts

    Maybe dumb question but for 1st stage engines could you have a sleeve on the outside that slowly dropped down as it got higher, so the bell would effectively grow as it ascended? Would that be too heavy? Or too hard to keep cool?

  6. Joel Hageman

    Engineering. Heating up the skirt. Always something. Like a Rube Goldberg. No wonder rockets are difficult. Pretty cool stuff.

  7. iamzid

    nah man. straight for the big hop.

  8. Mr. Quindazzi

    Love this channel. Great content

  9. 1_2_Die

    The Right Stuff
    … for my morning coffee. Good explanation of not so daily tech.

  10. ALiiENactivity

    Pretty sure Elon also wants a Booster done for the presentation.

  11. bigpod

    remember how musk said that the big hop will be exciting no matter what happens if we dont get to see it land we will see a giant explosion

  12. M HR

    For 4 Years you have been my Nasa. Love you Scott!! Thanks fore explaning /expanding – on all the “in between” parts! <3 :D

  13. burper2000000

    Who else kinda just chills at the end to the music

  14. phorzer32

    10:04 Is this Asbestos on the ceiling?

  15. John Schlick

    Elon has said that SN8 will get a nose cone and forward canards (so no mass simulator). The videos of nose cones show a separate tank in the nose cone as well.

  16. Luke Dogwalker

    Very good, informative video. I appreciate how no prior knowledge of rocketry is taken for granted, which made it very accessible and provided some clear explanations of topics I’ve been wondering about for a while. Good stuff 👍

  17. Esme n'haMaire

    Scott, please could you explain what “out of family ground sensor reading” means? What is being sensed? and why report the reading in such an odd way?

  18. Seal Piercing

    Maybe they’ll try to improve performance by cranking up the chamber pressure even more. Still able to test it at sea level, and has benefits for both engines rather than just vacuum.

  19. Ben Antilles

    Could you do a video about the MOOSE system, to get astronauts with the bare minimum of Equipment savely out of space ?
    You mentioned it in the past that it was thought about in the beginnings of human spaceflight, but never realised.
    Could it be more feasible with todays engineering ?

  20. Lazurkri

    I laughed my ass off at the SpaceX test; due to the engine being shrouded, it looks like the engine thrust is way too small to lift it.

  21. Gabriel Stevens

    Not first. 😭

  22. Allan Peda

    Damn, watching a rocket hover – it looks unreal.

  23. Nnotm

    “It’s safer to get the turbines up to speed very quickly using a separate, high pressure gas supply” – So what gas do they use for this? The image you showed suggests helium, but that seems like a bad idea since you can’t get it on Mars? Unless you can bring enough from Earth to cover the flight back as well

  24. subliminalvibes

    Nice. I can’t wait for SN-8!

  25. Ron Benton

    SN8 already on test stand; don’t think they’ll bring it back to factory until it flies. If that is before Elon’s presentation and it survives, then it might be there for show. Otherwise, would probably be SN9.

  26. Keaton Campbell

    The design of those landing legs show 3 cool things:
    1) Optimization of build time, by using readily available parts and performing minimal operations, without switching tooling. Grab a channel section, drill a bunch of holes in it, mount to actuator.
    2) cost Optimization duh
    3) MVP! Minimum viable product, it is fast and cheap to make, performs job well and dependably, which facilitates rapid prototyping!
    Very cool indeed! The welds were amazing but also all hand done, likely TIG. I could go on for hours about how much I want to be a SpaceX welder. The beads they do on the starships high alloy stainless is reminiscent of the massive Saturn V thrusters, their bells which had to be manufactured layer by layer, each welded together.

  27. PhiliChez

    I don’t know how recent that opening animation is my I super approve

  28. Vicente Coentro

    Good explanation of the way vacuum raptor engine works, thanks

  29. Nolsp

    Mass simulator is way too different from the nose cone in terms of aerodynamics so for the actual hop I’m betting they use the nose cone.

  30. Eor Equis

    “Getting ahead of themselves, building prototypes faster than they can blow them up.” I LOLed

  31. TheAtom

    They run lots of simulations so I’m sure they’ll figure things out & hopefully get it right the first time. But if they do crash SN8 oh well at least they can learn from a crash & improve the design.

  32. Joe Loedeman

    Scott, any information on the dragon tension ties causing erosion of the heat shield? Particularly how the trunk attaches and how that resulted in the erosion.

  33. Daniel Johns

    I was procrastinating from cal 3 and thinking how cool this stuff was. Then it hit me that I will never be able to work on stuff like this if I don’t go study haha

  34. Thomas Chow

    please walk us through the ‘rough math’ relationship between expansion ratio, chamber pressure and Isp!!!

  35. Trollyulian

    Hey Scott have you seen the Russian Nuclear Space Tug yet? Hope you’ll make a video about it.

  36. Cubinator73

    7:23 I have never thought about this, but how do you actually test engines specifically built for the vacuum? If you start up the engine in a vacuum chamber, doesn’t the engine pump gases right into chamber?

  37. Winston Smith

    “That would probably set them back.” There’s an understatement.

  38. Markius Fox

    I’d bet that the flash of a flame is the methane with the cryo puff being the LOX before ignition. I’m no rocket surgeon, but that makes sense to me with the engine layout and the cooling method. You’d want to get the cooling started which would dump some of the fuel into the bell, the igniters would cause the fuel to combust, then the oxidizer would push that out rapidly as the oxidizer pump spooled up.

  39. Jonas Bradley

    For the annual starship conference they should have a full stack of starship and super heavy

  40. Wallace

    Just a thought for a video – how about one on the chief engineers at Space X ?!

    I’d he interested to know if there’s a ‘von Braun’ or a ‘Korolev’ behind the rocket and engine designs – or perhaps it doesn’t work that way these days !

  41. rybářská vrána

    Another great presentation. Appreciate your thoroughness. On a related track I finished the series AWAY. Pretty much junk, but they did use ideas from starship. re-usability, belly flop entry into the martian. atmosphere and the tilt back to a vertical landing. wasn’t impressed by the hardware. lots of dials and switches. thanks for these excellent presentations

  42. Bruce Lee

    I suspect the chamber coating to be Zirconium Oxide. The color is correct from what I can see in the video. This coating has been used in AB assemblies for many years and provides good thermal protection in a similar type environment.

  43. Not 2 busy

    Why go with a mass-simulator when you need to test and get the readings during the rocket’s descent?
    They have several cones ready to go. Fit one on, add the flaps, and do a proper test.

  44. Super Fly

    Lul how do you actually test a HOLY THRUSTED BIG ENGINE on a vaccum test facility 😂😂😂😂

  45. Fred Derf

    Watchin’ Scott Manley while watching the Antares-Cygnus launch. Life is good.

    P.S. Launch abort — Boo!

  46. Valentine

    I went to check the description for the starship landing video and I’m happy to see it there :D

  47. Mikicat

    Maybe they left gimbal beacuse Elon wanted his own SSME? It really got close in terms of visuals

  48. Pleb Plays

    I will literally scream if spacex accidentally made an ssto when testing the Vacuum Optimized engine

  49. JeepinBoon

    I still want to know why the Merlin Vacuum engine appears to have a pulse with the bag wrapped around it… the bag pulses, why?

  50. David Kearns

    Turbopumps will always remind me of a turbocharger like what goes in a car.

  51. dr.rockzo

    Very cool stuff…i always assumed the space shuttle engines shook because of shear power involved making thier mounts oscillate.

  52. Brian Sinclair

    I see you’re a James Corey fan as well!!

  53. ThePixel1983

    They have s test facility: put 2 or 3 regular engines and one vacuum optimized one on a test starship and test it in orbit.

  54. HiddenGem

    Great topic choice, haven’t seen this discussed

  55. Kahan Vora


  56. Anarchy Antz

    8:36 Flat Earthers be like……. See!!! This is the proof the “tests” of this “Starship” are faked using CGI as we have proved you cannot get a “rocket” past a few feet like we have done.

  57. Alex Rossouw

    Space X gives me hope: I can build crazy things and have them still work masterfully!

  58. Astronomy Live

    What do you think the range safety system is like for SN 8? Could they get away with just an engine cutoff system if the IIP gets close to the limit, or would the FAA mandate a more active destruct capability?

  59. Nicholas Maude

    The Vacuum Raptor looks like a Rocketdyne F-1-lite.

  60. Jörg Altheimer

    Hi, have you seen how the nozzle of the Vulcain is produced? The nozzle is also produced from a copper core with channels milled into it. But then the channels are filled with wax and a nickel jacket is galvanized onto the core. Don’t know if other engines use a similar technique, but it is certainly interesting.

  61. Tyler Walter

    Thank you Scott not much about the Raptor and it’s iterations out there yet! Can’t wait to see the gases as they expand until orbit 🚀

  62. Rastersoft

    The channel-wall technique for regenerative nozzles was a soviet invention: it is heavier than the brazed tubes used in the US engines, but much cheaper.

  63. jonathan hart

    Scott: “Vac Rap”
    Me: “Is it hot?”

    Scott: “Very hot.”

    Me: “Fap Rap”

  64. Timothy Whitehead

    Re: radiative cooling. You mentioned being inside a skirt, but another issue is there will, I believe, be three of them near each other and they can’t radiatively cool towards each other.

  65. artyom g

    That just looks like a flying grain silo. It’s cool, but silly.

  66. Karl West

    I find myself strangely drawn towards Scott’s lego launch tower…

  67. Stephen Burrows

    Awesome, thanks Scott! Re: flight build…, surely they have to have a nosecone for aerodynamics and obviously the front flaps – smaller mass simulator though? Cheers… 🍻

  68. ravener

    gotta love exposing things to the surface of space

  69. Morgan Goins

    Thanks Scott. You’re the man.

  70. KX36

    that landing simulation at the end seems like it would be very high G.

  71. Caleb Brandalise

    Ive been waiting for someone to talk about the variance in these engines!

  72. SC Privat

    “And I am Igor” – Scott Manley revealing his actual name, 2020
    (10:09) Sorry

  73. Tuxfanturnip

    Thank you for making these videos with thorough, compiled information rather than jumping at every chance to make daily videos about what piece of sheet metal got trucked where at boca chica. You make some of the best videos on space news out there.

  74. zapfanzapfan

    Was expecting an analysis of the Delta IV scrub but this is better :-)

  75. dustin fisher

    Been waiting for this topic

  76. nagualdesign

    A wealth of information as always.

  77. David Kutzler

    They already have the stacking alignment stringers mounted around the top of SN8, so it’s “nosecone-ready.” Speculation is that they will do cryo and pressure testing first, then stack and weld on a nosecone while still on the launch pad before the 15 Km hop.

  78. Firetale

    When we called the old space capsules a tin-can, I didn’t expect that one day the rockets would like literal tin-cans…^^

  79. mjncad

    I like SpaceX’s get it done mentality.

  80. Brian Streufert

    7:10 Hi Scott. The bright bands seen inside the divergence section I believe is “ghosting” of the cooling jacket structure in the walls, not flow separation. Also, if you reduce the throat in order to get your expansion ratio but you keep Pc the same, then thrust will decrease proportionately to the reduction in cross-sectional area of the throat due to the required reduction in propellant mass flux which drives chamber pressure. The only way to reduce the throats area and keep thrust the same would be to increase chamber pressure. This will have an affect on the propellant mass flux as well as thrust coefficient driving it up.

    Great video as always!!!

  81. Arjun Amin

    Testing a vacuum engine at sea level. Big brain move.

  82. Clanner Jake

    “and hopefully…” scott, we’re all fans here… just admit we all want to see it belly flop hard, in high definition, 4k, 120fps, with 4k high speed replays. it would be glorious. landing would be nice, but what would be better is a massive explosion. in fact, the first 8k high speed footage we should have is slow motion of that thing greeting the earth a whale out of hitchhikers guide to the galaxy.

  83. Doug Golde

    Scott, please explain the various colors in the exhaust.

  84. elephantwalker smith

    euuh! Vacuum test facilities .., I worked on the J6 test facility in Tennessee. The AF SRB vacuum test plant. I designed the test cell, the supersonic eductor, and the 20 toroidal vacuum steam jets. We ran a large boiler set for 3-4 day’s just to get enough hp steam for a 90 second run…those were the days!

  85. Radio Active

    Damn I LOVE ‘rocket science’…I only understand a small percentage of it, but I still LOVE it!!!!!

  86. dosmastrify

    Remember that there have there been various sci-fi shows where you have something that clones itself and it turns out badly?
    Yeah. Look at his shelves

  87. DenseAlloy

    11:30 full scale test, to iron out bugs..very USSR

  88. Jurjen Bos

    8:07 “The raptor is a more complicated engine”. As if the RS-25 itself wasn’t complicated enough.

  89. Aditya Suri

    Once again, I can’t wait until SN8’s 18 km hop!!

  90. Tyler Walter

    The Vacuum start up sounded like one of those ceiling mounted heaters with the big fan on them 😂 A hell of a lot warmer I’m sure 🤣

  91. Vekh Gaming

    Wait, so they’re literally using crumple-zones as shocks?

    Guess this makes takes Lithobraking even more accurate as a descriptor.

  92. Dr_b_

    look at those shuttle engines warping, amazing

  93. Helium Road

    I like the little 3D man with his hands on his head in that disaster sim.

  94. Umi

    “Building prototypes faster than blow them up”
    Woo, that sounds very promising!

  95. Jerry Jiang

    They’re going straight to 15km, and not doing a 150m before it

  96. Chris Hayes

    The flow separation on the shuttle clip was pretty neat, those are some scary forces.

  97. Sambo Hambo

    Released just in time to sit down for dinner with this! This is the earliest I’ve ever been to a Scott Manley video, let alone one about SpaceX! :D

  98. Sean O'Brien

    In addition to the packed-in nature of the Rap-vacs making radiative cooling unworkable, is the regenerative cooling needed to make the engine reusable with no overhaul between most flights? The space Merlin is disposable, after all.

  99. Anonymous Freak

    5:10 – Another big difference between M.Vac and RapVac (regarding need for regenerative cooling) is that M.Vac are expended – RapVan will be reused. Even if RapVac were exposed, I’d wager they’d use cooling to make sure they don’t get damaged – not to mention planned “many reuse” within even a single flight before possible refurbishment. (Lunar landing, Mars trip, anything with multiple long relights between landings.)

  100. Jonathan Sureau

    I just adore these short little explainers that Scott does. I wondered about the relationship of the bell nozzle and atmosphere/no atmosphere, first time I’ve heard it explained clearly and simply. I also learned about the reasons for the exhaust shape in the test footage. This is what people initially hoped the internet would enable. Instead we got FB. goddammit

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