SpaceX’s Crew Dragon Spacecraft Exploded Because of ‘Corrosive Bullets’ and Leaky Valves

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Yesterday SpaceX released a report on their analysis of the ‘4/20’ Anomaly that destroyed their Crew Dragon spacecraft during a ground tests. It was the result of oxidizer leaking into the wrong part of the plumbing and then being propelled through the system as fast as a bullet.

Raptor Engine images by Jack Beyer

  1. Michael Byléhn

    0:08 “unfortunate anomaly” I would say fortunate as you WANT to find the flaws during testing.

  2. Martin Verrisin

    I agree that the abort module really does not need to be reusable XD
    //obviously, it’s still useful for testing ,but still

  3. Miki Cerise

    So NASA had good reason to be sceptical of the powered landing idea. :p

  4. Doug Bader

    Love what they are doing but isn’t helium a non-renewable resource?

  5. Pintuxo

    Thank you for the news, dear Scott. It is taking so long but with your help the time will pass better while we’re waiting for that new Crew Dragon to be finally brought to light.

  6. avtvforming

    Thank you for all the uppdates, Scott 😁

  7. Rifqi Taqiuddin

    Somehow i kinda expect a Simple yet Creative intro using Figures of some other planes and stuff. But glad you came back OK :)

  8. Stand4Liberty

    Could the mechanical check value have been adversely affected by saltwater?

  9. philosoaper

    No way did you make that full 1080p glorious graphics in fckin Paint…

  10. mpetersen6

    Why couldn’t the fuel and oxidizer be held inside bladders inside the tank the same way hydraulic accumaltors hold fluid under pressure

  11. mycroft16

    As stressful a job as it would be to try and figure this out, it’s gotta be incredibly rewarding to piece it together and find the answer. Never doubted the SuperDracos for a moment.

  12. Otpyrc Ralph Pierre

    Can the check valves on the input side of the fuel tank and the oxidizer tank be replaced with the same type of valve as the ones on the output side of the tanks?

  13. Péter Szabados

    “I’m Scott Manley, fly soon!”

  14. Jason Lee

    GREAT explanation, Scott. Thank you.

  15. Matteo

    There is a mystery on the 600 psi disappeared from the He tank. It has been tremendously compensated by the perfect quality of the graphics.

  16. Loyd Gravitt

    wow. Never would have seen that one coming. Good detective work. I feel much better about Crew Dragon now. Their proposed fix sounds effective and elegant.
    Who would have ever thought that they basically set titanium on fire. Nitrogen tetroxide continues to surprise!

  17. Martin P

    The video we have all been waiting for.
    Thanks Scott

  18. Saša Šimunović

    You Painted that diagram like a pro.

  19. Robert Evans

    Explained very well…thanks

  20. Jett Jo johnson

    It’s a good thing that this happened at this stage.
    Fluid dynamics under loads and interactions of different types, gets very complicated.

  21. Frik Na luzie

    Thank you Scott for dumbing it down for us, laymen. It really helped.

  22. Saumya Cow

    I’ll ask the bleeding obvious questions. Why, if the valve separates helium from a powerful oxidiser, is the valve made out of titanium in the first place? For that matter, why isn’t the plumbing all the way back to the helium tank also made of stainless or suitably coated? Also, didn’t anyone ask the obvious question “what if this valve leaks?” as you might expect them to ask about every valve.

  23. Paul Nel

    So glad the intro/outro is back!

  24. Rob Ostry

    “…A lot more slowly.” Wow, we need to cleanup some of our colloquial measures for clarity sake. That is nit-picking though, another great video and explanation. Thanks for the consistently good content.

  25. Dangermouse

    Love the reverse engineering of ‘anomalies’ like this.
    Finding the fault from a pile of burned scrap would be no easy task.
    Thanks for the video. 👍

  26. MNCpoops

    Doing anything for the 50th anniversary of the Apollo 11 Moon landing Scott?

  27. Chris Norman

    PSi on helium tank went from 3000 to 2400* just a mistake Scott aka a correction mid MS paint graphics? :D

  28. Metaldetection tube world wide

    In process engineering…its called “Hammering”
    A bleed valve in the pocket , is the best solution 😉

  29. rgmotnal

    Thank you for that explanation. That was super-fantastically clear.

  30. PatonB

    Odd, don’t know how you replace a check valve with a burst disk. Disks don’t allow fluids past where as check valves do in the 1 direction…
    Ah, nvm, figured it out. He pressure would rupture the disk for when the engine was needed.

  31. Dan W

    Thank you! I can breathe again, now. I wonder why these valves and things are not gold- or iridium-plated, so they won’t oxidize.

  32. Queen Nidus

    Corrosive bullets.
    **sweats in Elite Dangerous experimental effects**

  33. Little Cay

    Very good job with this explanation. Technically correct and well done visuals and contextual reference to the Mars mission that failed for very similar reasons. Excellent work.

  34. Wayne Shirey

    Thanks for the update. And welcome home.

  35. James Harmer

    Needs more equations. How can you baffle the masses with Rocket Science without some calculus ?

  36. tampafloridabeachbum

    Fantastic explanation! Thank you. 🖖

  37. Paul Rosebrock

    You’ve made me a bonifide space freak, vacuuming up all that is SpaceX related and annoying my friends every chance I get. Damn you for your insight and entertaining content…

  38. Scriptminer

    This was really interesting! Thanks for your explanation. The 1080p Microsoft paint diagram was brilliant

  39. mason saunders

    Thank you Scott as usual informative simple as possible and interesting appreciate it!

  40. Gustav Lessing

    Excellent explanation. I come here for good info, and am never disappointed. Thank you!

  41. Ludwig Behm

    That moment, when you hit that AZ-5 switch to get your ass to safety… VERY FAST….
    also… lots of pressure… again…

  42. Dan Haiduc

    So this is why steel walls are flammable in RimWorld.

  43. Rich Waight

    Brilliant video! Thanks so much for posting :)

  44. Riley Fenley

    Come on it was 4/20 they were all smoking that maryjane. This is just a coverup.
    But great breakdown, it really helps when everything is simplified down like this.

  45. Raymond Mucklow

    Even I understood that and I’m not rocket surgeon😁

  46. demizer1968

    Most of your high end air rifles are pressurized to 3500psi and up. It’s amazing how little blockage screw things up

  47. Yeti

    WOW. Thanks Scott That did really clarify the issues involved. FLY SAFE!

  48. The Mr. Pete Channel needs 700 subs!

    The Starhopper just blew up! SPACEX IS DANGEROUS!

  49. Don Jones

    Most impressive part: how did you remember/think to dig up/manage to find the part about the 1993 explosion in space?
    So glad the problem is known, fix going forward, flights going forward.

  50. Grigory Krylov

    Thanks for the clear explanation! BTW great MS Paint work!

  51. Whiskered Wizarrd

    “What we saw in that leaked video..”
    -Too soon Scott!!

  52. harbl99

    Capsule: BOOM! * fragments rain down across a broad area *
    Rocket scientists: “Hmmm, yes. Very interesting.”
    4:30 — TIL that everything is explodium in the right circumstances.

  53. Techlinious

    1:00 wait, isn’t that whats supposed to happen
    in ksp at least?

  54. arch the archvile

    corrosion i remember that one… come on what is left?

  55. Fenrirboulder

    Half Life 3 beiang made confirmed !!

    (it’s called Project Borealis)

  56. C and K Early Warning Systems

    Very similar to the Lunar Module ascent stage…

  57. Tom Hauer

    If this had been a NASA incident, we would be knee deep in congressional hearings by now with NASA being berated as mismanaged, short sighted and wasting taxpayer’s money. But since it’s a private company we get months of silence, a brief explanation of an anomaly and a near immediate approval to continue with crewed fight by the end of the year. Interesting.

  58. Bill Treusch

    So glad they released the results

  59. Branden Williams

    im impressed with the super draco bell you managed to make in paint. lol

  60. Kanithozl

    sounds reasonable to me.
    back in the day when I was a scientist we had an accident in our lab. a sample nano-scaled titanium particles was accidently exposed to air and instantly self-incinerated. luckily noone got injured, but the blast caused a lot of damage.

  61. Murray Ball

    As usual, a quality video (even with MS Paint) full of great info, and explained in a way that everyone can understand. Thank you Scott.

  62. Harrison Wheeler

    I watch several space related chans, but you always seem to jump out ahead of everyone with brilliant insight!

  63. Jone Army

    Do not worry, Werhern Von Braun had same problems in 40`s. You get it… or contact me, I can send you to Mars and back.

  64. DH Yukon

    A Burned marshmallow on a metal stick getting fired…what do you expect, it’s supossed to burst into flames

  65. Pavlo Perevoznyk

    1080p, full HD resolution in MS Paint…lol, you killed it Scott! The best!

  66. Iain Dowling

    In my experience as a mechanic I have found that check valves are very unreliable and the one of the first components to be examined.
    Lucky for me Diesel was usually my most flammable substance I felt with.

  67. Andrew

    I feel like just using a second check valve and putting them on the ox and fuel lines from the HE tank in the first place could have avoided this?
    Edit: a fellow engineer friend of mine pointed out the words that said “one way check valves”. They don’t teach plumbing to the undergrads at my university ¯\_(ツ)_/¯

  68. Derek Hansen

    Finally and update to this murder mystery.

  69. m.blacktree

    So basically, it’s like a “water hammer” on steroids…

  70. The Sphinx

    The sooner Spacex gets rid of the helium pressurization systems with Starship the better. It has caused so many headaches.

  71. Michael Vernon

    I’ll be honest, I was way off from the real reason the anomaly occurred. Sorry for blaming you salt water

  72. Larry Bush

    Was a reasonably quick FA too! Before I retired I worked at SLC-4E/W for 23 years. As a Corrective Action Engineer I was on distribution for all of Martin Marietta/Lockheed Martin FA reports. Was always very interesting reads!

  73. Juan Martinez Rossi

    Great explanation Scott, thank you 👏👏 Greetings from Argentina 👋

  74. C SMITH

    I would think the psi in the Helium tank would be higher.
    ie: my air tank (scuba) holds 3k psi. (not to compare per use)

  75. wwttffkares

    Darnit Scott, I love these videos. Make me feel like I actually know what’s going on lol. Thanks as always!

  76. Anthony Domanico

    Also, wouldn’t the burst disks make it impossible for the Super Draco’s to have relight capability? That would have been required in order for SpaceX to facilitate their land landings using retropropulsion because they planned to do a test burn at a high enough altitude to allow parachute backup if the Super Draco’s had an anomaly.
    Edit: I wonder if they could get around this issue if they slowly ramped up the valve opening. Rather than milliseconds it would take about a second. This would only be implemented when relighting the engine as the check valve’s seal integrity may not be compromised until its opened at least once. That way you could still maintain a quick reaction time for an abort operation.

  77. Narcissistectomy

    This has been documented for decades. It’s known as the “Taco Bell Effect.” When high pressure gas accelerates a soft blob of material directly through a one-way check-valve apparatus, causing an unexpected blowout.
    Every taco tuesday, someone experiences this effect.

  78. Jon Watkins

    Hydrogen hammer – even worse for plumbing than Water Hammer!

  79. NebuLex

    I bet they’ll find better engines in Area 51 on September 20th

  80. Buck Starchaser

    Acid reflux, in a nutshell.

  81. jonkersvideos

    Wow respect for the engineers who found that fault!

  82. Feeds Ravens

    My thesis was about leak detection in gas distribution networks (over distances), and when we were talking about what would happen if an oxygen carrying tube ruptured, and I said “that should be harmless”, my tutor said “Nope. when a tube carrying high pressure oxygen bursts, you have pure, unoxidized metal in a pure oxygen atmosphere. That gives a violent oxidization. Oxidizing produces heat. The tube starts to BURN”.
    Like here.

  83. Anarchy Antz

    Corrosive bullets and leaky valves. Remember folks, a strong chilli is NOT a good substitute as rocket fuel.

  84. Hernandez JR

    Everything went well, until it exploded.

  85. john pepin

    Check valves give the quirkiest troubles to chase. They usually don’t catastrophically fail, but leak a little, causing all sorts of idiosyncrasies.
    Been there done that, got the Tee shirt… lost it in the divorce.

  86. MrGoesBoom

    Nothing wrong with your real intro, but I actually kinda miss the improvised one you made with the X-wing toy. Can’t top those super high-res Microsoft Paint diagrams though…as always, thanks for your effort and dedication!

  87. dougpowers

    So, in essence, a leaky check valve built a gun armed with a nitrogen tetroxide bullet set to fire right when the controllers pressed the button labeled, “Make the spacecraft safe really quickly”? That’s some proper tragic irony!

  88. Tablet One

    If you can’t explain it simply you don’t understand it well enough. Thanks Scott! Well explained.

  89. Admiral Quality

    SpaceX sure have been finding some exotic ways to burn stuff that isn’t supposed to be able to burn. Last time it was carbon fiber in liquid oxygen. These discoveries will not only save their own vehicles but everyone else’s too. Take that, Murphy!

  90. WHColours999

    Ah, good ol’ MS Paint. Best invention to make inventions.

  91. bazoo513

    Back home, I see…
    One of the reasons to use check valves instead of burst disks might be a remnant of the days when they hoped for propulsive landing when Superdracos were more than just emergency escape engines.

  92. Jonny Oates

    Excellent video and well dumbed down for those of us who aren’t rocket scientists but are still interested. Thsnks for this, and all the other, great videos Scott!

  93. jocax188723



  94. P m W

    Similar phenomenon to steam hammer where you get a slug of condensed steam (water) in a low spot that gets accelerated by steam being turned on.

  95. David Hall

    I worked in the oil field as a mechanic for years. Usually check valves are set it and forget it until the seal goes bad and all hell break loose.

  96. teefkay2

    This is a significant paragraph from the SpaceX report:
    _”It is worth noting that the reaction between titanium and NTO at high pressure was not expected. Titanium has been used safely over many decades and on many spacecraft from all around the world. Even so, the static fire test and anomaly provided a wealth of data. Lessons learned from the test – and others in our comprehensive test campaign – will lead to further improvements in the safety and reliability of SpaceX’s flight vehicles.”_
    It is sad, but unavoidable, fact of engineering that we learn 1000x more every time some component fails (a structure collapses, a plane crashes, etc.) than we do when the structure or machine performs as expected.
    When they perform “as expected“, we learn nothing new.
    The phrase, _“… the reaction between titanium and NTO at high pressure was not expected …“_ suggests that this interaction has not been previously reported in the literature. It will be included now, to the benefit of all future spacecraft designs.
    This lesson was, gratefully, relatively painless to learn.
    Many other lessons have been far, far more painful experiences.

  97. walkergarya

    My engineering prof had a phrase. “Then bad things happen in rapid succession…”

  98. Hey Siri

    Wow, this video helped me understand the anomaly incredibly well! Thank you so much!

  99. CrimsonGamer99

    “Corrosive bullets”
    ULA sniper confirmed.

  100. Elopeous

    I like that Minecraft Fire Fx.
    Very realistic.

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