Rocket Fuel Injectors – Things Kerbal Space Program Doesn’t Teach

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Rocket Propellent Injectors are critical parts of the engine design, they take the propellents and mix them so that they can quickly burn in the combustion chamber. Injectors can make or (literally) break a rocket design, and over the years we’ve seen rocket engines move from injector plate designs to more efficient options as engineers have come to understand what works well.

Thanks to Copenhagen Suborbitals for sharing some video of their injectors being tested, I hope get get to see some more flights with these:

  1. JackSpeed 439

    Thanks for that. I think my garden hose is like a pintal injector.

  2. Paul Cooper

    So Scott – wow – soooo would using additive manufacturing simplify things eg ability to put a swirl groove inside injector holes without needing to drill them all?

  3. Dappdude

    I thought I knew a lot about rockets, but I learned so much from this! Great video!

  4. Stephen Foster

    Hands up who knows enough about rocket engineering to explain what Scott left out and got wrong.
    *keeps hands down*

  5. John Cashwell

    I love this stuff Scott, more more, please!

  6. Stellie Ford

    i’ve never seen something that operates at 643 bar before, you know, because its a bomb.

  7. fotmheki

    I didn’t know anything about fuel injectors so I love it!
    Hopes there are more to come.

  8. KayleeBrowncoat

    I’ll never take a shower in quite the same way again ☺️

  9. George Stockbridge

    The 3D animations are mazing for my understanding, thanks for including them.

  10. aplacefaraway

    2:21 that looks safe……

  11. sPACEr Official

    are you that guy in “prison break” as secret service man?

  12. Out OfTurn

    someone ask the question, how much power would it take to correct the earth orbit to be a more convenient length of time like 365 days.

  13. Sam Ferguson

    I missed this series (just like everyone else, apparently).

  14. Julien Ston

    I’ve been waiting sooo long for this episode!

  15. tolga1cool

    5:38 funnily enough positioning of the baffles was completely down to trial and error since simulations of the combustion chamber where completely impossible back then

  16. I Collect Stories

    I look up pintel, and it says it’s a pin usually inserted into a gudgeon. I look up gudgeon, and it says it’s a small fish or gullible person.😣 Poisson!
    Yeah, there’s something there about pivots or hinges, too.

  17. Simon Coles

    would be interested to see what kind of injectors are used in linear aerospikes…

  18. MalfunctionM1Ke

    That was a very informative and interesting video. I would like to see more of these, eapecially on the concepts of staging.

  19. Josh DeHaan

    THANK YOU! This is one part of the design I always wanted to know more about.

  20. Alex Distler

    never seen scott talk with his hands so much haha. great content as always! my #1 YT channel. hands down

  21. Jam the Ooze

    Cheers Scott. That shirt be tops.
    Stay classy friend.

  22. ste kra

    Next Turbopumps

  23. Roesti

    Hello, its Patrick from switzerland here :D today i just want to thank you for your work! its nice to see how the people are exited about space again. and its because human like you! thanks a lot!

  24. The Darth Knight

    I’d love to be a fly on the wall for dinner at the Manley house. This is one of the best informational vids I’ve ever seen, Scott you’re the best! 🤘🏻

  25. Casey K. - [ Piano and Music ]

    Hey, this is back! Exactly when I need it lol

  26. NomadSoul76

    “according to Elon Musk”… Who has never stretched the truth before…

  27. Mike Cowen

    Has anyone noticed how the Death Star weapon is an impinging jet injector?

  28. Miro Bucko

    I wonder, could I buy one of those coaxial swirl injectors and use it for my shower head?

  29. Larry Scott

    DSCOVR EPIC is back!
    That’s worth a shout out

  30. CheshireTomcat68

    0:59 Anomalous Plume, my new 70s inspired progressive rock band.

  31. Super Gamer Fail

    It’s been a while since I’ve had a project to work on in the machine shop. You’re tempting me.

  32. Replicant Monk

    0:04 I love that model of the MC75 Profundity you have there, sir!

  33. Urban

    I have been waiting for this video so long

  34. OnceIWasYou

    This is phenomenal- I love hearing the minutiae, 0.1% improvement style elements in engineering (as a comlete NON engineer!) and this is fantastically made. Though I imagine the % increases of yield, SI etc. could be more than .1%!

  35. Matias Gomez Janzen

    10:19 bruh those welds *inside the chamber

  36. Paul Paulson

    This offers a great background for rewatching some of copsubs videos!

  37. Cory J. Honer

    Been excited for this video! Had a feeling it was coming. :)

  38. DarkWereWolf6969

    3:27 look at delta’s h20kinetic shower head

  39. Antoine Roquentin

    11:57 “quite easy to manufacture” *wipes machinist tears*

  40. Captian Morgan

    And yet, apparently, we never went to the Moon….

  41. Cavegoblin EXTREME

    You where so cheerful at the beginning! It put a smile on my face.

  42. Alex G

    Finally! Copenhagen Suborbitals gets a well-deserved shoutout! All space-lovers should stick together.

  43. Timo Hendrickx

    I love your Intro: “Hellow its Scott Manley here!”…. My wife is eye rolling everytime.

  44. Dysputant

    just place spoon inside bell.
    I know water hitting spoon spreads into fine particles accelerates to near light speeds and covers all available area.

  45. Andy Wells

    Hello there the series is back yaaay

  46. NukeCat

    “I’m Scott Manly Fly Safe “

  47. NavidIsANoob

    This series is actually insane and I hope you realize how good this video is, Scott.

  48. Mike Hoogstraaten

    That’s been some time, glad to see you going back to the roots :-) Thanx !

  49. galfisk

    What are the considerations for injectors in hybrid rocket engines? I imagine not having the oxidizer gouging divots in the fuel might be important, but how critical is the design?

  50. Bagana

    I need a new shower head.

  51. ClippedWing - Ben Smith

    Scott: This is something you might of heard of.
    Me: It’s confirmed, I’m thick as s**t…

  52. I Collect Stories

    0:23 Whenever I’m leaning over an engine, there’s a guy telling me “the disconvolvulator is confribulated; we’re gonna replace the precursogrieve, which is a $10 part, but the labor is $800, okay?” and I nod.

  53. Yuushiro Kimiyazuwa

    Yes!. nother “Why Kraken isn’t real” Episode

  54. Cindy Corbel

    This was posted 2 minutes ago, and the series is back!

  55. Horizon Brave

    “your spray tends to go off in one direction” yea….getting old sucks..xD

  56. Brian Streufert

    Unlike split triplets is the way to go; we’ve been using them for over 20 years. Its a simple design which places the manifolds in relatively easy machine and design locations and gives outstanding performance. Added advantage is its easier to balance out the resultant momentum of the impingement sheets as well as making the injection orifices relatively the same size for the more common LOX/hydrocarbon propellant combinations. This helps with hydraulic losses and makes your pressure drop across the fuel and oxidizer similar if not equal. Really smooths out the injection stream pattern.
    Edit….although there are some interesting versions of the pintle injector as well…..currently designing one now; err for the past year that is. lol
    Interesting meaning specialized variations.

  57. Debapratim Dutta

    I missed this series sooo much!

  58. David Kearns

    rocket fuel injection sounds a bit like cars, An endless fight to get the optimal mix of fuel and the “air”(in the case of rockets oxidizer)

  59. Aaron B

    This is the kind of thing I love learning.

  60. A. Elisabeth Majere

    Love these videos, and I definitely miss your Kerbal series. Hope you do some more when KSP2 gets released :)

  61. hobbified

    3:22 I found your problem — you’re trying to run the rocket on ketchup and mustard instead of RP1 and LOX.

  62. hboy007

    every time:
    Hello it’s God Manley here

  63. mjproebstle

    i like how you engage us you tubers in your deliveries, as if we were actually out here trying to build our own rockets! its a very personable and intimate approach that definitely captivates the listener. cheers!

  64. Heinrich Wonders

    Once again I realize: Space is hard.

  65. George Kanulas

    I never knew that rocket fuel injectors might be that interesting!
    Thank you for another excellent video.
    Waiting for the one about the meteor rocket 😉😉👉👉

  66. Jamie Li

    As an engineering student looking to build a liquid fuelled engine for a capstone project, this was amazing

  67. Fryguy101

    Combustion instability is a recurring issue with big rocket engines, so I’m curious your thoughts on the Sea Dragon and its proposed single massive first stage engine (Calculated to be 350MN, compared with the Rocketdyne F1’s piddly 6.7MN).
    I think combustion instability would’ve killed it even if they had decided to take the Sea Dragon seriously, but do you think such a large single combustion chambered engine is even possible?

  68. Gandalf Wilson

    “Good propellant injectors can make all the difference between your engine performing excellently, and it exploding due to combustion instability”
    So one part goes wrong and the whole thing blows up. Isn’t that just normal rocket science?

  69. Joel Swanson

    When I saw the video title, I thought it was an old video because he hasn’t done a video in this series for a long time!

  70. HellishGrin460

    Damn… I was just thinking to myself “you know what would be a good idea” and 10 seconds later, pintle injector… Guess i’ll never have my million dollar idea if I go into the rocketry business, too many people smarter than I.

  71. Max K

    3:55 That’s actually a best case scenario of impinging jet misalignment. Depending on the impinging pattern used, if one of them misses it’s mark you could be shooting a jet of pure oxidizer straight at the blazing hot wall, which regardless of the material used likely wouldn’t be long for this world.

  72. profwaldone

    Me at 0:00: probebly looks like a snow machine.
    Me at 17:51: a very, very fancy snow machine.

  73. Orion Aerospace

    YESSS keep this series alive we love it so much!!!

  74. roidroid

    Why do we even have the word “bedroom”, when we already had the perfectly servicable phrase *”thrust chamber”*

  75. Daniel

    I’m a PhD candidate working on rocket propellant atomization and I have to thank you so much for fueling my impostor syndrome with every sigle video.. It’s just great! Seriously, this is great stuff!
    Of course, I have to say though… That the conditions at which liquid behaves like a normal liquid don’t really exist in a rocket. If the engine is already running at high temp and pressure, then it’s transcritical injection. It’s kinda hard to tell the difference between liquid and gas, no one’s sure how much surface tension actually exists to form any droplets. Before ignition conditions are way cooler (ahah). Because in a vacuum everything boils, the propellants flash-atomize, like your garden variety aerosol can. If pressure is below triple point it even freezes (constellation Urion in Apollo 13). We are researching this to improve ignition reliability using cryo without igniter fluids. But I know little about the engineering side. Btw when is a video about future RCS coming? I hope someone comes up with Metha/Hydro-LOx RCS at some point to justify the computational hours I’m wasting.

  76. jesse wilson

    I would like to see colored water used during the tests like yellow and blue, The visibility would be nice

  77. Air Command Rockets

    Rocket science is easy, Rocket engineering is hard.

  78. Chef_PC

    I really miss your KSP plays.

  79. Carl Groover

    “Rocket science has to work within rocket engineering”. My favorite part of this video.. haha. So true

  80. Povl Besser

    I’m so happy you included footage from Copenhagen Suborbitals’ tests!

  81. Emanuele Di Matteo

    Missed this series

  82. Frequent Flyer

    That saturn-V slo mo launch never gets old. What a beast!

  83. Dietrich Struble

    Some people have a shower head as a fuel injector
    Scott Manley is the kind of guy to have a fuel injector as a shower head

  84. Hueson Wong

    Literally my dissertation that I’m working on right here (on swirl coaxial injectors):
    While I can’t be 100% certain, the Raptor engines’ ones would probably be similar to the Copenhagen Suborbital’s ones in that the fuel is swirled by entering the injector tangentially (consider the location of the fuel rich preburner and turbine with respect to the injector face plate), given the location of the oxidiser rich preburner and turbine, the oxidiser should flow more or less in a vertical straight line towards the injector.
    As the oxidiser is entering the injector coaxially, it cannot be swirled like the fuel, although that does not mean it cannot be swirled (here’s the guessing bit) – I reckon the raptors probably pass the oxidiser through swirl vanes to increase or create swirl. The reasons for this are:
    increased shear between fuel and oxidiser creates more intense Kelvin Helmholtz instability which kind of results in folding of the fluid layers more efficient combustion;
    a vortex breakdown can act as a bluff body for the fuel to impinge against;
    the vortex breakdown acts as a recirculation area for more thorough, and complete combustion;
    the recirculation area serves to stabilise combustion;
    the swirl vanes themselves produce a pressure drop, meaning that the injector can be shorter for the same amount of pressure drop;
    shorter injectors mean lighter engines;
    shorter ones are stiffer and are less prone to fatigue and cracking which is key to reusability.
    the only drawback I can come up with is that they’re a bit awkward to make.

  85. Copenhagen Suborbitals

    Thanks for the feature, Scott! Glad to contribute to your video, great work! 🚀

  86. Jim Meeker

    Mach diamonds make me smile.

  87. Ultrawup

    Imagine the level of nerd swag one can achieve by having a rocket fuel injector as a showerhead…
    “Hey babe, my shower has coaxial swirl injectors, wanna come over and try them out?”

  88. Gustav Gnöttgen

    3:22 Scott: “Blah blah blah”
    Me: “combined mustard and ketchup dispenser for hotdogs”

  89. StYxXx

    USA: “Stop! Don’t show our engines, they’re protected by ITAR! Delete that photo!”

  90. Cody'sLab

    Yes! I’ve been awaiting this one!

  91. Maarku

    *Destin enters the chat*
    Me: “Sorry Destin, no laminar flow here”
    *Destin leaves the chat*

  92. Benjamin Heasly

    The Death Star used an impinging 8-tuplet (later 9-tuplet) like super-laser injector.

  93. api9mm

    The 18 injector pot system in the German V2 (A4) combustion chamber was based on the successes they had with the smaller A3, which used a single pot at the head of the chamber. Due to the speed in which they needed to produce the much larger engine as a functional prototype for the war effort, they simply multiplied a system that previously worked,18X. It should be noted that during the development of the A4 starting in 1940, Deputy Director of the Peenemünde Army Research Center, Dr. Walter Thiel, had simultaneously developed a conventional flat injector plate variant of the A4 combustion chamber. Due to instability issues, it was not entirely ready for production. Regardless, in late Dec 1942, Hitler ordered full-scale production, which resulted in the V2 (A4) as we see it today with it’s luminous LOX plumbing to the 18 pot system, with over 5000 having been produced that way. Much to the protest of Dr. Thiel, it was really a production prototype. Thiel’s single LOX feed, to flat plate design, would have looked more like the A6 Redstone engine developed a decade later through the influence of von Braun’s team in the US. Why so long? Thiel and his entire family were incinerated by an RAF bomb in a slit trench in front of his home in Aug 43. Incidentally, a moon crater is named after him on the dark side of the moon.

  94. Rowdy Yates

    I’ve got pintle injectors on all my garden hoses. I use them to throttle the water and even shut it off.

  95. pentagramprime

    Today I learned the difference between “Rocket Science” and “Rocket Engineering.”

  96. Eric Cosner

    I’ll never look at shower heads 🚿 the same way again.

  97. Plasminium


  98. Ali s

    North Korean rocket scientists: “Write That Down, Write That Down!”

  99. EkulSolo

    Now I want to buy a fuel injector and use it as my showerhead

  100. flippynl

    this all sounded a lot like rocket science.

Comments are closed.