Why did the Falcon 9 Explode?

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so this SpaceX rocket was fueling then this happens boom 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 bring the Thunder 10,000 speed of sound about 300 meters per second so travels by a kilometer every 3 seconds 10 seconds about 3 kilometers to miles away give or take and that rocket cost about 60 million dollars and the satellite which you can see here falling the ground sometime after the explosion cost about 200 million dollars so that's about a quarter of a billion dollars that just went up in flames there so why did it actually explode let's start with the obvious most rockets explode from the business end that's where the engines are because once they lit what you've got is the fuel and the oxidizer communed contact and that releases a crazy amount of energy and if that goes wrong that can easily destroy the rocket actually let me step back a bit further what a rocket does is essentially mix a fuel and an oxidizer which is usually oxygen and it burns and gets hot and it expands and it's that expanding gas which pushes the rocket forwards the combustion process is actually very similar to what happens in your car apartment there you have a fuel air mixture much more dilute version and it's those burning hot gases expanding which powers your engine now in your car of course you just get the oxygen to run the engine from the air but you can't do that with a rocket because you just can't get enough oxygen into your engines so you have to carry it your own concentrated oxygen supply which usually comes in the form of liquid oxygen and ballpark numbers a cubic meter of air contains about the same oxygen as 200 milliliters of liquid oxygen so you can carry an awful lot of oxygen in liquid form now the problem there of course is that liquid shiny's bloody cold not far off the temperatures but which nitrogen liquefies the practical up shopping these that you really kind of a greatly pressurized main tank for the oxygen of the rocket because it was just way too much and your rocket needs to be light so you have liquid oxygen in essentially an unpressurized time there is a slight overpressure in there but it's not far off what you could blow with your lungs now take pure oxygen gas on its own and it's not too bad but mix it with anything that will burn say for instance like chicken flesh or cloth and just give it an ignition source and it will burn like crazy and so what I'm going to do first is anything like this then I'm going to put it out and then a dunk it into the oxygen atmosphere just to see what happens so you'll see when I set it on fire here that it's just a sort of regular cloth so but it's okay yeah I blow it out and then when I put into the oxygen atmosphere the whole thing burns up in seconds and just for that it's all gone so that's what your clothes would burn like in a pure oxygen atmosphere now what I'm going to do is going to try the same thing again but something that would sort of equate to human skin and what I'm going to use her first proxy is chicken skin okay so it's more or less the same deal I've just got a a piece of chicken on the end of a piece of wire so what I'm going to do is I'm going to emulate what my burning clothes would look like from just a I'm going to put a burning splint in there just under the under the chicken for just a one or two seconds okay so we'll see what happens blow that out and here we go so as you can see people would burn really quite amazingly well and it's the oxygens basically gone at that point so as you can see it's a very good thing that her atmosphere is only 20% oxygen because if it was 100% oxygen smoking wouldn't just be bad for your health it would be suicidal and liquid oxygen is a brutally powerful oxidizing age and this is the cheese puffs let me get the oxygen in there go ahead and get up hold it there for a second okay pull back oh wow okay see see that's why I brought the fire extinguisher as well sure similarly with petrol you know gas the stuff that runs your car on its own it's not too bad but in air a dilute oxygen atmosphere it's a horrific fire hazard it's no coincidence that mixing liquid oxygen and gas kerosene gives you rocket fuel and it's an incredibly energy dense system kerosene and liquid oxygen was what powered the first stage of the Saturn 5 and it's also what powers the SpaceX Falcon 9 rocket however in a rocket it's just stored in two big tanks there is no immediate fire hazard until you mix those two together which is usually done in the rocket motor that being said once fueling has happened the rocket is essentially a giant potential bomb sitting on the launch pad which is why fueling is typically the last thing you do before launch and of course you evacuate the pad while you're doing it because it's so dangerous if your Rockets are just a massive hazard indeed a fully fueled Saturn 5 contained an equivalent amount of energy to all the bombs the Allies would typically use to destroy a city in World War 2 now fueling a big-ass rocket takes a lot of time so for instance to fuel the space shuttle you had to pump about 700 tons a fuel into that external tank and that took hours I mean that's the weight of about 35 bigger tanker trucks that had to be emptied into this rocket and if you watch fueling of a rocky in time-lapse you can actually see where the liquid oxygen level is climbing and chilling the rocket causing water condensation on the outside of the rocket okay so the rocket on the pad is basically a giant bomb and clearly while fueling it goes boom but how could it actually go boom you see all you've got at the moment is two giant tanks one of carotene and one liquid oxygen well clearly the proponent must have mixed to give this explosion and when kerosene and oxygen are mix they give this really red sooty flame which is quite different from the clear flame that you get from burning hydrogen and oxygen that's basically the difference between the exhaust of the shuttle and the Saturn 5 now like I was saying earlier all a rocket is is pushing an oxidant and a fuel into a combustion chamber now there are two key and non-trivial problems with that the first is how do you stop the combustion chamber from melting because the flame temperature is typically higher than any metal you can make it from and the second problem is you've got a very high pressure in that combustion chamber so how do you actually keep pumping liquid into it now the malting problem is typically overcome by pumping the cryogenic fuels through tubes in the engine bell there by using your fuel to actually call the rocket motor and the pumping problem is basically what makes rocket science rocket science eat our big-ass turbo pump that requires vast amounts of energy to run I mean it has to pump all that fuel that took a couple of hours to pump into the launch vehicle into the engine belt a high-pressure something that is typically running it liquid oxygen type temperatures in a couple of minutes typically two to three minutes is the burn time of most rockets basically it's the engines job to release all of this energy in a controlled fashion in a full of minutes and that's what makes rocket an engineering nightmare the extreme conditions under which these engines one means that if anything goes wrong with those pumps this sort of thing can quite easily happen and a failure occurred involving one engine and shortly thereafter another engine also lost power it was therefore necessary for the Range Safety Officer to destroy the missiles by remote control and the rest is just structural failure of the rocket which is basically two giant fuel tanks so back to our SpaceX explosion well clearly the explosion doesn't come from the business end well actually not entirely there is a second stage on this rocket and now it looks like that's where the explosion comes from so a little chemistry you actually quite a lot of oxygen to burn kerosene which is why you need a bigger tank for the liquid oxygen than for the fuel so ballpark numbers there's a factor of about a thousand expansion from turning liquid oxygen into gas which is basically true for most gases and when you burn that with the fuel you get a further factor of 10 expansion because of the heat so basically a liter of rocket fuel gives you a factor of about 10,000 expansion in gas ballpark numbers what we know the size of the rocket it's about three and a half meters in diameter so we know that the initial fireball size is about 20 meters about 20 yards in diameter well if you know the diameter then you can calculate the volume so about 3,000 cubic meters is the volume and that fireball was after a factor of about 10,000 in expansion so that would have required about a third of a cubic meter of liquid fuels to be mixed for this explosion keeping me to reserve these sorts of liquids weighs about a ton so it's about a third of a ton explosion it's 300 kilos about the weight of three people of rocket fuel now that might sound like a lot but it's actually not that much when you consider a rocket like this weighs about 500 tons 400 tons of which is propellant then of that generously maybe one percent of the fuel mixing caused this initial explosion however those propellants shouldn't be able to mix until they get into the combustion chamber so what sort of things can go wrong that would allow a problem like this to occur well typically with these things you're looking for a single failure and the most obvious place waiting at a single failure that'll mix the two fuels is where the two fuels are in close proximity separated by a single wall now two obvious thoughts spring to mind the first is the rocket designs like this the oxygen pipes typically have to go through the kerosene tank at some point and host pipes typically have to be straight kill the high liquid oxygen flow rate needed for big rockets and the Falcon 9 is a big rocket so basically those plagues typically Oh straight through the middle of the kerosene tank and that kerosene will quite happily freeze at liquid oxygen type temperatures and to aggravate this the Falcon 9 chiller kerosene is a trick to make it more dense which means they didn't take up so much space so your tanks don't need to be as big it's a sort of weight saving thing for the rocket now I don't know how the Falcon 9 deals with the problems of the kerosene freezing let alone on the second stage but it's an obvious point of failure in the valley here would allow you to get the kerosene and the oxygen in direct contact so for instance if you add the kerosene freezing around the Occident lines they could have stressed and cracked the fuel tank alternatively a failure in the oxygen tank or just an leak in the liquid oxygen could cause similar stressing and failure of the fuel tank if that liquid oxygen ends up on top of the fuel tank and this is one of the things that bugs me about people gush over Elon Musk all problems I've talked about here have been explored in debt and solved long before he or I were born but people still get ecstatic over this [Applause] yeah this is impressive but let's keep this contribution in perspective I mean recovering a rocket actually has a lot of technical drawbacks I mean the first one being is with a rocket you typically hit your best bang for the buck out of the last bit of rocket fuel that's Rockets a typically ninety percent by weight fuel a rocket engine produces very effectively constant thrust so typically when you light up your rocket it's only just powerful enough to lift itself off the ground it's got a very low acceleration when you start six five four three two one zero all engine running liftoff we have a liftoff 32 minutes past the hour liftoff on Apollo 11 then as you burn off progressively more of the fuel the rocky gets lighter and so it's your producing constant thrust you get more and more acceleration as the rocket gets lighter indeed with the Saturn 5 missions have shut down some of the engines early because otherwise the acceleration would have killed the crew well actually maybe not that bad but they were getting up to 3 G which means 100 kilo person would weigh about three times that March and it puts lots more stress on the rocket and so forth the bottom line is when you burn your last bit of fuel did you get a lot more speed out of it than you did for your first bit of fuel now this is of course an advantage that you lose with the Falcon because you have to save enough fuel in your rocket to actually decelerate it and stop it suffering heating but it reinterred the atmosphere and enough fuel to land it now that's not entirely your face burden in that when the rocket lands it only weighs 10% of what it did when it took off I mean where it lands it's basically an empty rocket but it's still a disadvantage and in many ways I'm surprising go.this the way that nasa did with mars that you start off with a couple of parachutes and then only light the rockets for the last little bit of the journey now it's a payoff for this you do recover your rocket engines which is where it again gets tricky I mean this is not the end of the story even if you can recover the engines which isn't a new thing either the shuttle was doing this for over 30 years now you'll recall earlier that I said that the real problem with these things these rocket engines was the fuel pump and I'm not so sure about the economics of this sure it sounds like a great idea but then again it sounded like a great idea with this space shuttle and it still so ended up being one of the most expensive launch vehicles on the market for those who are like rah-rah-rah musk can do anything a nap while they have recovered some of the launch vehicles as of 3/4 of the way through 2016 they've never reused n you plus I can't remember the last time I saw a rocket blow up while fueling because those problems were solved a long time ago I mean wiki actually informs me the last time that NASA had a fuelling explosion with some 40 years ago the possibility that trouble may develop with the Atlas or the redstone during the countdown or during the take-off is looked squarely in the eye by the astronauts and the engineers behind project [Music] I mean for many of the free-enterprise or make space cheap and accessible don't seem to have realized that sure there may be some savings to be had by the free market but organizations like NASA basically wrote the rulebook on this sort of stuff they would never have allowed a design like this off the drawing board where merely making a single mistake in flipping one switch could lead to a catastrophic failure and loss of the vehicle Scaled Composites did not emphasize human factors in the design operational procedures simulator training or hazard analysis for spaceship 2 although a spaceship to program personnel said they were aware that unlocking the feather during transonic flight would be catastrophic there was no warning caution or limitation in the spaceship to pilot operating handbook or on the P fo for test card that specified this risk in addition human factors was not fully considered in spaceship 2 training as the simulator did not replicate the vibration and loads nor did pilots train wearing the same flight gear that they were expected to wear during actual flights in the vehicle scaled missed opportunities to identify design and/or operational factors that could have mitigated the catastrophic consequences of this single human error although scaled engineers referenced some military standards and FAA circulars because commercial spaceflight is an emerging industry no human factors guidance currently exists specifically for commercial space operators so yeah this is impressive but it should be kept in perspective as an incremental development in rocket side just like with other concepts of reusable spacecraft it remains to be seen if this is going to be a profitable [Music] you you

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Channel: Thunderf00t

Views: 534,195

Rating: 4.3293962 out of 5

Keywords: elon, musk, falcon, rocket, explosion, spacex, motor, internal, fire, satellite, million, boom, philip, mason, thunderf00t, lox, shuttle, nasa, orbit, launch, fuel, fuelling, 60, dollars, pad, facebook, youtube, free, sued, reusable, space, vehicles, cape, Canaveral, fireball, smoke, Boeing, astronaut, complex, Mars, hyperloop, testing, test, unmanned

Id: BPv0VZcvm4Q

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Length: 19min 45sec (1185 seconds)

Published: Thu Sep 08 2016

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