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

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



  • So what are the benefits of using burst discs instead of check valves?

    Dr. TranDr. Tran13 วันที่ผ่านมา
  • It would seem having a valve that opens rapidly instead of modulating was the main culprit but not even mentioned. Maybe the engineers there should have asked their local plumber about rapidly opening/closing shutoff valves and the pitfalls of check valves!

    Pete FPete F14 วันที่ผ่านมา
    • @Scott Manley G'day @Scott Manley Yes that's a good point, but we're not talking about the Janitor finishing his hamburger and then wandering out with a Stillson wrench to turn the valve on. A valve that "gradually" opens means milliseconds in order to control the pressure wave front. From your report, the NASA recommendation was for burst valves to be used, and at least that indicated they were considering the shock wave (indeed used that property to perform a function). It seemed by their design, the implications of the pressure wave weren't even considered by the designers, and the proof was in the pudding. ... In this case the pudding exploded. Not exactly a handy design feature for something intended to save the crew! How fast do you want your crew fried as both the "rescue system" and the rocket are exploding? After any accident there are always people like me who will come out with "Coulda ... Woulda .... Shoulda"; those of us in the aviation industry deal with it constantly. That may grate the current generation where everything is always "awesome", but I feel that's the price to pay when dealing with other people's lives/money. I sometimes get the impression the team there are making it up as they're going along. That's fine when building video game; how many there are putting their hand up to sit on top of the candle when they light it? Would you? Obviously all just my personal opinion.

      Pete FPete F13 วันที่ผ่านมา
    • @Pete F OK, so how slowly do you want an emergency escape system to operate when your rocket is exploding?

      Scott ManleyScott Manley14 วันที่ผ่านมา
    • @Scott Manley Scott thanks for replying, but from what you mentioned it was the OPENING of the valve in the pressurising gas that caused the "obstruction" to be propelled along the fuel line, causing the damage. This is a very basic and known problem and a first year apprentice plumber would be aware of that issue (as would any home owner dealing with "water hammer"). Obviously I know nothing more about the system than what you described (very well incidentally), but it appeared there was no good reason to have the pressurising system's valve operate so quickly. Pressure shock waves in hydraulic systems is nothing new, neither is the fact that check valves leak. Fluid Dynamics is a first year engineering subject, at least down here in Oz. I thought this failure was a face-palm moment and I'm literally embarrassed for the engineers involved.

      Pete FPete F14 วันที่ผ่านมา
    • Do you have time for a slow opening valve if your rocket is exploding?

      Scott ManleyScott Manley14 วันที่ผ่านมา
  • psi really? Use real units man.

    Ensign RageQuitEnsign RageQuit21 วันที่ผ่านมา
  • 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.

    MatteoMatteo23 วันที่ผ่านมา
  • Its Tony Bruno

    uwuuwu24 วันที่ผ่านมา
  • corporations can only afford to deliver profit..

    Mark PhelanMark Phelan24 วันที่ผ่านมา
  • I believe they haven't killed anyone on their tests yet. but some have

    MoebiusMoebius24 วันที่ผ่านมา
  • I would love to see a video what would happen if a rocket just ascended vertically. Straight up no trajectory

    Michael TuckermanMichael Tuckerman25 วันที่ผ่านมา
  • Can the pressure system not be brought up to operational pressure slowly so the N2O4 in the lines doesn’t arrive like a bullet?

    Steven SmithSteven Smith25 วันที่ผ่านมา
    • Scott Manley ah, yes well there’s that point. I’d forgotten this was for an escape system. Can the plumbing not be prefilled with an inert buffer? Wouldn’t that prevent the bullet effect of leaked oxidizer without having the untestable burst disk be a part of the mechanism?

      Steven SmithSteven Smith24 วันที่ผ่านมา
    • How long do you want to wait in an emergency abort?

      Scott ManleyScott Manley25 วันที่ผ่านมา
  • 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)

    C SMITHC SMITH26 วันที่ผ่านมา
  • exploded because of lack of foresight. Blame it on a valve like an oil rig? No purge valve, no trap in piping, no sensors behind or after valve to test pressures, detect oxidizers in helium? Plz Even a hobbiest at the drag strip installs a purge valve on their NOS system for safety.

    Prove Me WrongProve Me Wrong26 วันที่ผ่านมา
  • What about doubling up the check values? Having 1 Check value, then another right after it? You could even add a sensor of some kind in-between the check values and before it. A sensor type that can emit a scanning signal of some kind that is non-reactive to the materials used. If a leak is occurring in one check value, hopefully the second check value can ensure that it wont get very far and the sensors can detect the problem long before device activation.

    Double M.M. BunnyDouble M.M. Bunny26 วันที่ผ่านมา
  • Thank you Scott Manley!!

    John O'DriscollJohn O'Driscoll26 วันที่ผ่านมา
  • So, Scott, why are the valves replaced by the burst disks, and not supplemented by them by, for example, placing the burst disks between the LF/O tanks and the check valves? These are both relatively low-cost parts, in the context of a rocket engine, but each protects from different kinds of failures, and importantly, these different kinds of failures occur at different times.

    Dashiell BarlowDashiell Barlow26 วันที่ผ่านมา
  • Great news! The silence was worrying me.

    Admiral BobAdmiral Bob27 วันที่ผ่านมา
  • 1080p, full HD resolution in MS, you killed it Scott! The best!

    Pavlo PerevoznykPavlo Perevoznyk27 วันที่ผ่านมา
  • im impressed with the super draco bell you managed to make in paint. lol

    Branden WilliamsBranden Williams27 วันที่ผ่านมา
  • Hmmm... So titanium under the right circumstances can act as catalyst? Actually this accident can open new avenues.

    MinonianMinonian27 วันที่ผ่านมา
    • Not a catalyst; a fuel.

      jimW133jimW13326 วันที่ผ่านมา
  • The one way valves go back to default closed position to stop fluids going back down the pipe, they are usually spring loaded to auto shut when the pressure drops to below spring force etc, but of course can be motorised

    Nick HardyNick Hardy27 วันที่ผ่านมา
  • 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.

    Riley FenleyRiley Fenley27 วันที่ผ่านมา
  • You Painted that diagram like a pro.

    Saša ŠimunovićSaša Šimunović27 วันที่ผ่านมา
  • The sooner Spacex gets rid of the helium pressurization systems with Starship the better. It has caused so many headaches.

    The SphinxThe Sphinx27 วันที่ผ่านมา
  • 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.

    Murray BallMurray Ball27 วันที่ผ่านมา
  • Why not keep a bit of helium pressure in the lines at all times?

    Benjamin BrooksBenjamin Brooks27 วันที่ผ่านมา
  • Lucid Explanation. Thank You.

    bruce bagnolibruce bagnoli28 วันที่ผ่านมา
  • by adding bust disk spacex will be making the thrusters a one time use right? one time per flight till the disk can be replaced?

    Ben NaylorBen Naylor28 วันที่ผ่านมา
    • No but it was originally designed to propulsive landing and what not just a escape system the system can leave orbit and reenter the atmosphere if the second staged malfunctioned in orbit the draco thruster can do alot more just be used for escape system

      Ben NaylorBen Naylor7 วันที่ผ่านมา
    • because you're planning to use the escape system multiple times in the same mission?

      Phoe PhoePhoe Phoe7 วันที่ผ่านมา
  • Most importantly, we now know that there is a spy inside spaceX

    Dakilang MaginooDakilang Maginoo28 วันที่ผ่านมา
  • Well, seems like The old school engineering firms such as Boeing , Lockheed and Northrop know something after all.

    kenya catholickenya catholic28 วันที่ผ่านมา
  • 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.

    mycroft16mycroft1628 วันที่ผ่านมา
  • Of course they need this loss, to try to make the space agencies seem real and credible, but are not.

    MrAuberyMrAubery28 วันที่ผ่านมา
  • Wait a minute? Aren't the superdracos supposed to be in-flight restartable?

    Joshua HudsonJoshua Hudson28 วันที่ผ่านมา
    • nope, abort only

      TheBackyardChemistTheBackyardChemist28 วันที่ผ่านมา
  • 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.

    NarcissistectomyNarcissistectomy28 วันที่ผ่านมา
  • 02:34 ,,something werent quite right'' you told at the start on the video they know exactly what went wrong... seems to me they actually dont now anything^^ in my opinion this ,,something werent quite right'' should be the main thing to look after or am i wrong??

    marvin luthermarvin luther28 วันที่ผ่านมา
  • so it is Space X causing the helium shortages in the US.

    james corvettjames corvett29 วันที่ผ่านมา
    • Nah, it’s economics. In the 90’s politicians started selling off the strategic helium reserve, that meant it wasn’t profitable to harvest helium. Now supply can’t match demand.

      Scott ManleyScott Manley28 วันที่ผ่านมา
  • 3:55 I think you meant to say "Minecraft Fire" 😂

    MinecraftPhenom08MinecraftPhenom0829 วันที่ผ่านมา
  • Ok my assessment of blame on the engines may have been wrong, but I'd like to know if this check valve was 3D printed. If it was I'd feel completely vindicated. Either way I'm still skeptical of 3D printing as a practical way to manufacture strong parts, but I do hope nothing explodes in the next launch abort test.

    Andrew LueckingAndrew Luecking29 วันที่ผ่านมา
    • Check valves will not be 3d printed. 3d printing is used for short run items with complex geometry, check valves are used everywhere and have simple geometry compared to a rocket combustion chamber.

      Scott ManleyScott Manley29 วันที่ผ่านมา
  • Wouldn't another method of preventing this problem be to use an automated gradual opening of the pressurant valve? Burst disks can't be a final solution if they want to have multiple restart capability... Furthermore, what if part of the burst disk breaks off and blocks a passage downstream? I know they aren't supposed to, but then check valves aren't supposed to leak either.

    travis dunntravis dunn29 วันที่ผ่านมา
    • @Scott Manley Good point. I'm beginning to understand why my spaceX application was turned down xD

      travis dunntravis dunn29 วันที่ผ่านมา
    • There’s no such thing as a gradual opening when your booster is already exploding

      Scott ManleyScott Manley29 วันที่ผ่านมา
  • It's a good thing that this happened at this stage. Fluid dynamics under loads and interactions of different types, gets very complicated.

    Jett Jo johnsonJett Jo johnson29 วันที่ผ่านมา
  • I hope NASA won't Need Another Seven Astronauts.

    John NyJohn Ny29 วันที่ผ่านมา
  • So they intend to blow up the space station next , spacex extreme fireworks company .

    guy foxguy fox29 วันที่ผ่านมา
  • Excellent explanation. I come here for good info, and am never disappointed. Thank you!

    Gustav LessingGustav Lessing29 วันที่ผ่านมา
  • this theory doesnt add up-

    Jack SmithJack Smith29 วันที่ผ่านมา
    • I agree.

      guy foxguy fox29 วันที่ผ่านมา
  • Didn't that really clever guy invent a testable check valve, ya know the one Elon Musk named his car company after...

    Michael McAdamsMichael McAdams29 วันที่ผ่านมา
  • " don't want your liquids flowing back into your gas section. At least it might cause burping..." If they flow all the way back to the Y-joint you're going to get a hell of a burp. They're hypergolic! Yikes!

    jfan4revajfan4reva29 วันที่ผ่านมา
  • This is so ironic, as Tesla invented a one way vale that cannot fail. Someone tell Elon!

    The EnglishmanThe Englishman29 วันที่ผ่านมา
    • "this cannot fail" is usually a phrase found in the category "famous last words"

      Jim PanseJim Panse29 วันที่ผ่านมา
  • Very simply explained and diagramed. Nicely done

    givingus5givingus529 วันที่ผ่านมา
  • Corrosive bullets. **sweats in Elite Dangerous experimental effects**

    Queen NidusQueen Nidus29 วันที่ผ่านมา
  • Would have to agree that Rupture Disks are way more reliable than Check Valves. Not reusable but could be easily replaced between tests. Failure for the win.

    Likely candidateLikely candidate29 วันที่ผ่านมา
  • This happens when I eat Taco Bell.

    jw33jw3329 วันที่ผ่านมา
  • Thanks for explanation. BTW Dragon2 doesn't have to worry about busy parking at station because it uses the old Shuttle PMA2 docking port which nobody uses. (but still has to take appointements to make sure they schedule crew rotations etc).

    Jean-Francois MezeiJean-Francois Mezei29 วันที่ผ่านมา
  • Scott, your quick and simple responses and explanations are amazing and still manage to be great quality. It’s a bliss to have them.

    sunkid86sunkid8629 วันที่ผ่านมา
  • This was really interesting! Thanks for your explanation. The 1080p Microsoft paint diagram was brilliant

    ScriptminerScriptminer29 วันที่ผ่านมา
  • Man you do a great job Manley!

    Scott DorflerScott Dorfler29 วันที่ผ่านมา
  • What is burst disc and how does it work.

  • I would guess frame shift drives are immune to this problems?

    martin masangamartin masangaหลายเดือนก่อน
  • Great video man was able to comprehend all of it :D

    Jonathan MartinJonathan Martinหลายเดือนก่อน
  • No isolation valves behind the check valves? Odd....

    A. I.A. I.หลายเดือนก่อน
  • When your blood flows backwards through the venal valves, trouble.

    Cby 0530Cby 0530หลายเดือนก่อน
  • Nice job explaining this.

  • Nice ms Paint skills, lol. Thumbs up!

  • No one was hurt. This is why we test.

  • No one ever said reinventing the wheel would necessarily be easy.

    Dale ComerDale Comerหลายเดือนก่อน
  • Thats a rough couple months for Mr. Musk

    jason archerjason archerหลายเดือนก่อน
  • Ok, so the Mars Observer Failure Investigation Board concludes that Nitrogen Tetroxide had leaked past the check valve and either reacted with the titanium or caused some other problem. Yet, Spacex writes ”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..." . Someone help me out with this contradiction...

    Saumya CowSaumya Cowหลายเดือนก่อน
  • 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.

    Jone ArmyJone Armyหลายเดือนก่อน
  • Only in aerospace could moving vehicles between parking spaces once every 3 months be called "very busy"!

    Jonathan LeeJonathan Leeหลายเดือนก่อน
  • A question to Scott Manley: Did this video get demonetised by any chance?

    Noxem VulpenhaireNoxem Vulpenhaireหลายเดือนก่อน
    • No

      Scott ManleyScott Manleyหลายเดือนก่อน
  • you see what happen to star hopper big fire today

    Jason OuglitchininJason Ouglitchininหลายเดือนก่อน
  • You could say that fuel block accelerated *applies sunglasses* Like a rocket!

    Christiaan VenterChristiaan Venterหลายเดือนก่อน
    • Christiaan Venter YEEEEAAAAAAAHHHH!!!!

      NarcissistectomyNarcissistectomy28 วันที่ผ่านมา
  • Good to know, thank you.

    Ulen MarzjevUlen Marzjevหลายเดือนก่อน
SpaceX's Crew Dragon Spacecraft Exploded Because of 'Corrosive Bullets' and Leaky Valves