Don't be fooled by the accent. He's just a good old country boy teaching in Bristol Raising some chickens studying hamsters and never dating girls wearing crystals I'm telling y'all he's a country boy who loves his mama good Like Batman's got his robin like Doritos our health food I'd tell you more if 3,000 miles to our show you Well, it looks like we're in business here. I hope you've got some image in front of you and if not, I'll just okay way Hey, it is Friday the 13th after all So, uh, it's great to be back here two years ago I talked about my first book Super Sans was all about the way the brain creates these illusions that there are Patterns and energies operating the world and you can understand that this is the basis for supernatural belief So, you know, this would have been a good day to return to that But today I wanted to tell you about a different type of no illusion one Which is actually more pervasive because it's an illusion shared by Believers and non-believers alike and that is the self illusion this idea that we're integrated coherent individuals Who are inside our bodies somehow operating it almost like a puppet master with kind of coherent thoughts and processes I'm going to claim that that sense of the self is not what it seems to most of us So what do you mean by the self? Well, if I was to say to you Do you like vanilla or do you like chocolate ice cream? You have a sense of the self of hearing a question Contemplating an answer and then formulating some some response. Now, that's the sense of the self in Conscious moment awareness.  These are all sorts of bits of information Which are what we call the personal identity of self. So William James called that the me So both the eye and the me are facets of the self, but I think they're both constructed by the brain I'm not denying people have events and Experiences of course, but I would argue that the brain abstracts these and weaves these together into a coherence a coherent characterization of identity and Certainly the idea that it's an illusion don't that doesn't mean it's not real an illusion means that it's not what it seems And we should be wary. I'm not denying you're having the experience What I'm trying to say is that the experience of the self is very different and we should be reminded by this from a classic film If you pop that up there I'm sure most of the geeks in this audience will well recognize this masterpiece of science fiction No slides nothing. Oh, that's a shame. You missed the soundtrack as well. Oh I went to all that effort never mind. Yeah, should I do it again? It's pretty cool soundtrack. Okay. Here we go. Let's try again Yeah, cool Let's walk some leather and dark glasses. It's always gonna be a winner, wasn't it? Now the thing about Neo is of course he thinks that he's a computer programmer But we know that and he like the rest of the civilization has been enslaved by the sentient computers To harvest them for their biochemical energy And the way they keep them enslaved is they feed directly into their brains a simulation this this matrix So that they never know now of course it signs fiction But the principle that if you could ever control the the working of the brain Then you would effectively control the mind is is one which I think is worth exploring Because I have to think that we we're not living in the matrix as such But we are simulating the external world the whole time and I also think we're simulating an internal Character to interact with that world. So for example at the moment You've got this very rich experience of seeing me with my hands and you've got all this detail of this amazing visual field But in fact, you're only processing a small part of it. You're only really processing the central part of your visual field It's colorblind and smeared in the periphery of your vision. You've got two black holes You know which correspond to the blind spots Portions of the retina with our new photoreceptors and yet your brain fills that in all the time very reliably You just would never know now Of course, you can move your eyes all the time to look around and investigate the world But every time you move your eyes your visual scene is literally blanking off You're you're actually blind every time you move your eyes If you don't believe me go to the restroom after the talk and have a look in the mirror And then stare your left eye and then your right eye and then your left eye and you can't see your own eye movements You're effectively blind for two and a half hours of every waking day But you would never know that because your brain creates this this simulation It's all filled in all just seems rich continuous and coherent, but that's not true Now I also think that there's a multitude of unconscious processes Which are really the basis our thoughts and behaviors, but we simulate this character the individual to try and keep track of all The multitude to give it a sense of coherence. So that's what I think the self is I think it's a sort of serial interface if you like between the complexity of the world out there and the multitude of all the unconscious processes So how does this happen? Well, how does this get created? This is this is me by the way This is my brain. I had an image in one of our studies a couple of years ago Everything that I am my anxiety speaking to all you people and my thoughts and my memories somehow are encoded and stored in This three pound lump of tissue, but of course I didn't pop out my mother's womb as Bruce That would have been a bit strange. I had to become I had to develop into Bruce And so there's a developmental processor. How does that happen? Well, you're all familiar now the brain is made up of vast networks of billions of neurons and they all communicate with each other through these electrical impulses and that information is Interpreted coded into these synchronized patterns that we are basically Presentations of the external world or representations representations are are the language of the brain and even thoughts and memories that you dwell upon or bring to consciousness Are representation systems? So how do those representations get there? Well, I think some are built in but a lot of them are required through experience So this is my interest by the way. I'm a developmental neuroscientist The baby brain is a lot smaller, but what you may not appreciate it actually has more or less the full complement of neurons as an adult Around about 86 billion, but what is changing of course is the connectivity between those neurons Basically, there are two processes is a very rapid explosion of connectivity this sort of progressive Wiring up generation of synapses, but there's equally a degeneration or pruning back of experience And the reason this happens It's a way that the environment can literally shape the brain because you don't want to keep connections Which are never going to be lost Never going to be used and in this way You know the brain is literally being shaped and this has some interesting consequences For example, you know that every child has the capability to learn language of the born of Japanese parents and race in the US They will easily effortlessly acquire English, but England quarry In developing expertise you become tuned in to your particular environment and lose the capability and flexibility of hearing and Perceiving other aspects. So this explains for example why it's often difficult to hear the differences in other languages We can test this out Let's have a go. Let's see how good you are with Hindi So I want you to listen very carefully and you'll hear two segments of Hindi You know, this is audience participation, by the way time I'm going to ask you to raise your hands if you think they're the same or different.  Let's go sound up on this You ready? duck duck Hands up if you think they're different Hands up if you think they're the same Yep, they're they're different. One's a word. One's a complete non-word. Apparently. Here's another example Dole dole Different you got it. Ah, you get you learn Hindi fast Yeah, they actually are different in general though. It's very very hard to tell these sorts of things It's not just sounds and voices also faces We are wiring in and tuning into the environment. The next one's a really good example I used this last time I talked but it's such a it makes a couple of really interesting points So this is the McGurk effect. So watch carefully and see tell me what you think he's saying ba ba ba ba ba ba Hands up if you heard da da da da da pretty reliable. You probably put money on it Okay, this time close your eyes and listen carefully. You ready? ba ba ba ba ba ba Gotcha. Yeah, he's saying ba ba. He's not saying that at all Why do you hear that? Well, it's because actually what we've done is we've cheated a little bit We're using he's mouthy gaga. Okay, so that shape of that visual information You don't have any representation in your brain for that shape of mouth on that sound so your brain basically Comes up with a solution to make sense of this incompatible information So you don't have any direct contact reality Your brain is giving that to you all the time trying to make sense of the world of ambiguity missing information Now these examples typically have been talked about in the realms of perception You know low-level vision voices stuff like that, but we're increasingly coming to understand that the brain Is really a social brain and it's really important to have very important very enriched social environments Now you can't do these sorts of deprivation deprivation studies Ethically with children, but every so often you do get these examples where children have been raised in terrible conditions of social deprivation The most scientifically studied example. This was the fall of the Chalcescu's Regime the Romanian orphans and they were basically Children who had been dumped by their parents who couldn't look after them So they had the food in the water, but they were kept in isolation and they were then taken out and raised in very nurturing environments But the point was despite that intervention these children still ended up a very severe Deprivation and they're now adults and they're they have social problems in many ways We should have known that anyway because the work of Harry Harlow in the 60s had shown that it's really important to raise To get a social environment. He raised Reese's Monkeys gave them all the food and warmth in the water that they could need But just left them isolated and they ended up socially retarded Normally an environment is pretty good. So but childhood, you know children just love other Other people, you know, that's what they do You know my I thought for example with You know faces are just like magnets to babies. They love other people. They pay that's the most important stimulus to a child It's not a toy or anything. It's other people This is what our brains have evolved to do and we will emulate and copy and in fact a lot of the learning really What only makes sense in the social context? I love this next one actually This is a this is a European MP who took her daughter to a very important vote in the European Parliament I don't know if she got the extra vote there But anyway, you know we emulate and copy our parents and this is what we do to become this strange race I was at DJ growth. He called us the social private sale. You know we congregate we spend a large amount of time Doing things which if you were an alien from another planet would look really bizarre, you know, we need other people I mean there are some of us who don't you who are isolates and try to keep away But for the majority of us we spend in an order amount of time becoming a social animal. So how do we do that? Well, we have to develop a sense of the self because I don't think we're like super social species like ants and bees and that I think that we are we are a very social animal But we're a collections of cells because we need to integrate or interact at an individual base basis We we don't interact with multitudes of unconscious processes. So how does that come about? Well, the sense of self I think is there's developed There I think babies probably have that I notion of the momentary consciousness I think that's probably there, but I don't think they have personal identity. I mean, how could they? That's something which I think they they pick up over the early childhood years. So for example self recognition They don't generally recognize themselves in the mirror. There's a famous rouge test.  It's just another baby But you know from about 18 months onwards, they'll they'll remove it indeed other animals which are social animals also pass this task So there's some controversy about exactly what this test means But I think you know, they're certainly becoming self-conscious aware of others around them looking at them They start to pick up identity some the early identity markers are things like boys do this girls do that Children of this age are very kind of categorical. They don't have very nuanced ideas And that's only as they get older. They understand their set exceptions to the rules They acquire what we call a psychologist call a theory of mind They understand that others have mental states which might be different to their own because prior to that they're fairly Egotistic this assume everyone has the same thoughts as they do And then throughout this period is this increasing Concern about where they are in the pecking order. This is the development of self-esteem You know, they're starting to interact with their peer groups. They're starting to be worried about where they are And of course a lot of childhood is is focused on this concern about where there are where they are in the pecking order The worst thing is being ostracized bullying Then we have the teenage years and an attempt to establish yourself get your own identity separate to your parents Finding oneself. That's what the teenage years are all about and of course the irony is that everyone turns into the parents in the mid 20s So this is this is what happens now along with this This goes back to my first book on on on supernatural beliefs because I think this growing Sentience this growing self-awareness Also fits with the idea of Mind-body dualism, which is I think the most common Position that people assume when you ask them about the mind and the body They think that they're separate that we inhabit our bodies These are vessels which we sign up kind of right around and we control them And you know and they let us down, you know occasionally we say oh my legs given out or something like that We feel that we are separate to our bodies You know we face the mirror on a kind of daily basis We see the ravages of age and we see our external appearance changing But we feel internally that we're still have continuity So I think there is this tendency to assume that we are inhabiting our bodies And then we move with our bodies somehow and this is a There was some discussion of this idea today about the idea of duplication and I just filled around with keynote So please indulge me here we go That was worth it wasn't it? Yeah, I'm a bit of geek So the idea is that we never really questioned about the mind and the body being separate You know it's only when you face with these unusual thought experiments What happens if it malfunctions in episode five? I'm sure there's some start to it, you do remember that episode five? Yeah you're out there, you can't hide Yeah episode five we had James T. Kirk duplicated I prefer actually this film you haven't seen it you really should see as a classic Chris Nolan Batman director This is a film The Prestige about two Victorian dueling magicians And one of the protagonists Hugh Jackman meets up with a real life Nicholas Tesla Who builds them this duplicating machine I won't give the plot away because it's a great film but basically he copies himself And the question is if you could really build a machine which duplicates down to molecular level Then would the mind be duplicated? Michael Sherman mentioned this this morning It's a familiar thought experiment that philosophers talk about And most people think that you couldn't, they think their mind is indivisible Their mind is unique, their mind is something which can't be copied And I think that's a very common intuition but where does it come from? Well we started to as I say I work with children We wanted to know about this and we talked to six-year-olds And it's very difficult to discuss thought experiments with six-year-olds But what you can do is you can actually kind of give them an example And this is how we create the duplication scenario So this is how it goes Here's Mr. Strong, see how nice and squishy he is I'm going to put Mr. Strong in this box like that Then I'm going to close up the box Close up that box Make sure my machine's turned on And then turn it to green, turn this one to green as well And press go And see what happens So here there's Mr. Strong So in this box as well Ah, amazing, huh?  And we show them lots and lots of examples of every toy being copied And they believe this But the real question of interest is what happens if you put a living thing in there Now obviously the box is a little bit too small to put a person in there So what we did was we had the pet hamster And we told them, by the way, this work is coming out next month So I'm quite excited about it I've been talking about this for some time And it was never peer reviewed And now it is, and it's coming out in a good journal But here's what we found The long and short of the story is that We told them that we had this hamster Which had physical properties They couldn't see, it had a marble and a tummy and a broken tooth And then we gave it some mental states So we told the hamster the child's name We showed a picture the child had drawn And then we put it into the machine and then duplicated it And now there are two hamsters And the child's asked, well, does it know your name? Does it have a marble and a stomach? And the bottom line was they basically were quite happy That all the physical properties were copied So there wasn't a problem with that But they were very reluctant to think That the mental states were also copied That was only found in the first hamster In fact, the effect was even stronger If you gave the first hamster a name By calling up Bob So once you have identified an individual Then along with that comes a whole or baggage About unique minds being inseparable We're quite happy to believe that Simple animals without minds like aphids In fact, aphids are clones But simple animals can be duplicated But the idea of sentient and sentience And minds is something which we don't believe Can be manipulated or copied in that way So where is this self? Well, let's think back to the discussion of the eye Of the sense of the conscious awareness At the point in time If you get people to just try and meditate And then point to where they feel Their seed of consciousness is This is generally where they think they are This is based on another study by other people And you think you exist somewhere Inside your head sitting behind your eyes But there can't be a little person Sitting in your head behind your eyes Because that wouldn't make a lot of sense If they're inside your head Who's inside their head and their head And their head and so on So you get into the problem of the homunculus Or that's the infinite regrets That's why you can't have the unified self Inside your head This is probably a little bit more accurate As you can see, I use a lot of popular culture When I'm doing my science This is the num skulls And this is a guy called Ed And he has all these little people Now clearly you haven't got lots of little people In your head And even if you're dead You still have the problem of the homunculus But it is true to think about the mind As being comprised of a multitude of functions That somehow come together To form a coherent sense of self And I think that the evidence strongly supports this This is the work of Roger Sperry The Nobel Prize winner And his student at the time was Michael Kazanaga And they were doing work with these patients With intractable epilepsy One of the treatments for that Is to cut those connections I was telling you about the corpus callosum To separate the hemisphere It stops the epilepsy spreading Now the consequence of that is Because the way that your sensory and motor systems Are organized The left part of your field Is processed by the right side of your brain And the right part of the visual field And motor control is processed by the left hemisphere What you can do And this is what Kazanaga did Is you can present these split brain patients With information which is inconsistent In both hemispheres So in this situation, for example You get them to fixate the middle spot And say what they see on the screen Now language is predominantly in the left hemisphere And they would respond, oh, it's a ring And then you say, well, will your left hand Pick up the object from the table But because that's processed on the right side Which controls the left hand They would then pick up the key And when they're confronted With this inconsistency What they typically do Is they confabulate an account A story which makes sense Of all the incoherent information And I think that's what is going on I think the brain is creating That has a multitude of unconscious influences Which are somehow having to be reconciled I think Stephen Pinker captured that With the notion of the eye consciousness When you say consciousness isn't the master and chief It's the spin doctor of experience So I think that that's what's going on You're basically trying to create a coherent picture And this also goes for those memories Everyone thinks their memory is very reliable John Locke, the philosopher, talked about identity As the culmination of episodic memories Somehow being brought together But of course memories are not that reliable And they're always being reinterpreted Reintegrated with new information And our next speaker, Carol Tavris Is among some of the world's authorities On the way that we reinterpret information To fit with this characterization Of who we think we are We have this notion of an idealized notion Of our self And when we don't do things According to that character You say I wasn't myself Or it was the wine talking Well wine doesn't talk And if you weren't yourself Then where were you? So you know, it's true You must be this culmination of factors And again, if you think back Over the history of social psychology This notion that we are individuals Is always challenged by the fact That we just are so manipulable And sensitive to the cultural context The social context, so obedience Ashes' work Most people would actually administer A lethal electric shock Although most people claim They wouldn't listen to Milgram's work The arbitrarily set people up Into different groups They have in-group, out-group biases Start treating the other group nasty And of course all this work Kind of leads to this sort of explanation For why people do incredibly Inhumane things to other people So the idealized notion of who we are Is somewhat questionable So our brain is a social brain And from the very beginning I think it's one which is very much geared Towards other people and influenced By other people But you know, don't worry About this idea of the illusion Because I think people are concerned Well, illusions means it's not there But if you consider this illusion This is the Kniece illusion You know, you see a square But it's of course an emergent property Of everything there But here's the important point If you went into the brain To the visual processing areas You would find assemblies of cells Which are firing as if the square Really is there So although it's an illusion In terms of the representation It's effectively there In the same way I think the characterization of the self Is one which is an emergent property Of all the influences which have shaped You over your life But you be foolish to think That you exist independently of them In the same way You be foolish to think That the square exists independently Now, I went through that talk rather fast And I'd be wondering, you know Is he on speed or drugs? No, the reason I went through that fast Is because I decided to change The end of the talk I got a phone call on Wednesday night And I know you've already heard about this But it's such an important issue And I had a small role in it I just wanted to remind you And show you maybe some of the stuff You didn't see about Why this is so important I'm talking about the bomb dowsing thing That I was involved in some You know, three years ago You may not know But James Ramney in 2008 Was responsible for having the guys Who perfected this dowsing role This is this piece of equipment That they claim could discover You know, drugs and explosives The SNFACs that have put our business Where did they go? They went to the UK They started up again A whole bunch of companies We had the GT 200, the AD 651 And I would not have known About any of this If it wasn't for the fact That the New York Times Published an expose on Published a report showing The Iraqi government has spent $85 million investing in these devices To be used at checkpoints Rather than doing the appropriate thing Which was to thoroughly search The cars for the bombers The consequence was That hundreds of people Were losing their lives Now I'm an academic I'm not an activist normally And I wouldn't have done Anything about this But it turns out that the company Was just down the road for me And the director, Jim McCormick Was there So I blogged about it This is disgraceful We've got to write to MPs We've got to do something This is really outrageous There's just simply no science For this And to my great surprise Jim McCormick Maybe it was the fact That I was an academic And he was seeking some validation Wrote back to me And invited me to come down And we were going to test it And I thought this was an opportunity Which was too good to miss So I got in touch with the BBC And we did a sting operation Because we wanted to expose Jim McCormick At the time And this is a little bit Of what we did Good evening A news light investigation Has discovered that a supposed bomb Detector produced by a British company And sold for use in Iraq Simply does not work Following our revelations The government has to ban their export To Iraq and Afghanistan The Iraqi government has spent 85 million dollars on the devices Which have been widely used And there are concerns that the Detectors have failed to stop Bomb attacks that have killed Hundreds of people There are some disturbing images In Caroline Hawley's exclusive report Yes, see? Jim McCormick may be hiding From the cameras here in the UK But he did appear at a press conference In Baghdad after last month's bombs Filmed by Iraqi television He and this Iraqi security chief Were trying to persuade local journalists The detectors worked The grenade the device is meant to Detect is placed in full view Of the operator No surprise It points at its target It would be comic If the consequences weren't Potentially so tragic We brought the footage To show to Professor Bruce Hood Okay, well I was on the Look, there's been a lot of people Involved in this campaign I was just involved in the Part of the TV show Because basically this company Had been given an export licence By the British government Which was unbelievable And they would have done nothing If it hadn't been for the fact That we went on to national Television and broadcast that The following day He was arrested And the export order ban Was issued for the sale Of these items to Iraq And Afghanistan Now, at that point We thought that was a major success We then discovered That he was continuing to trade As was GT 200 And the other companies In fact, trading to your neighbours Mexico, where they have been Buying millions of dollars Worth of these pieces of equipment And I have to confess I was pretty upset That in fact we may have Lost the battle in the long run But then February this year The police visited me And I gave a statement And then I got this phone Call on Wednesday night To tell me that in fact They now had sufficient evidence That Jim McCormick was actually Going to face trial And indeed, yesterday morning He appeared in the High Court And not only Jim McCormick But all of them Gary Bolton The Trees Sam Schardt And Andy Rosell And they're all probably Likely to go down The result of the case Won't be probably until February We're going to be working More with the BBC To do a proper story about And I assure you James Randi's definitely Going to get credit for this So thank you very much One of ours One of ours Bruce Hood, ladies and gentlemen, fantastic


Good morning in the last class we had derived the expression for the unsteady variation of pressure in the rocket motor right we had considered the mass balance in the rocket motor to derive this equation in this class let us look at how we can use that to predict what is the time required for ignition what is the time required for extinction okay till now we had looked at only the steady part that is the burning in the steady portion right this class let us look at the other two unsteady portions that is namely ignition and extinction if you look at a typical thrust time curve or a pressure time curve this is ignition time and this is extinction time now in this class let us try and use the relations that we had obtained in the last class to find out how these vary okay if you remember we had derived the equation for pressure variation as if let us say the motor is operating at the equilibrium pressure itself let us say it is operating somewhere here then this PC this PC is a time variant term okay there is not an equilibrium quantity this PC will also be equal to the PC and as a consequence these get cancelled out and you will get this DPC by DTS 0 okay so in this equation we had identified the VC by AT as L star and this entire term as 1 by PC right 1 by characteristic time so we can write this as now let us say how to use this to get what is the time required for ignition okay and what is the time for extinction before we go there we should understand this that why is this important in a rocket motor okay ignition delay let us say if it is a very long time then also it is a problem it is a very short time then you can have a very high pressure burst in the beginning and then therefore affect the structure okay you could actually burst the motor in that time so either either of the two is not what we want we want to operate it in a very narrow window okay typically even in a large motor the ignition should be over within 100 milliseconds okay 100 milliseconds is it time that we are looking for so let us try and derive the expression for the ignition time now during ignition if you look at this portion this is a very small time as I said it is less than 100 milliseconds right so if you are looking at that kind of a time scale one can make this assumption that the chamber volume and the burning surface area and C star do not change in this period okay VC is chamber volume VC changes only because of burning in 100 milliseconds it does not burn too much so VC and AB will be nearly the same and C star if we assume we will assume constant I can write this term VC equilibrium 1-n as follows KN is equal to AB by 80 I should also add here the throat area also does not change with time in this case right during the initial phase of ignition it is a very small time and we are not looking at hundreds of seconds so the burning the throat area also does not change so in this case KN will be also constant this entire term is a constant and I can absorb it as alpha I will call alpha is equal to rho p KN AC star so if I want to find the time for ignition all that I need to do is integrate this equation now the limits of integration need to be identified okay typically the igniter is supposed to give something like 30% of the pressure rise let us say this is this equilibrium pressure is 100 bar the igniter should give something like 30 bar on X1 okay so around 30% of equilibrium pressure so if we integrate this we will get T ignition is equal to integral okay this is the 1 by TC into TC into this is the equation that we need to solve and alpha we have identified what it is so now we need to play a little bit of jugglery here if you look at the denominator we can express this as let us say X is equal to PC to the power of 1-n okay then what will be DX DX will be 1-n into PC to the power of – N DPC this equation I can rewrite this as T ignition is equal to PC PC to the power of – N DPC then I will be left with alpha – PC to the power of 1-n okay so if I use this here this is nothing but the same equation rewritten if I now use this substitute this here I will get I can change it to the X variable integral X ignition to X equilibrium okay this is nothing but DX by 1-n so I will get TC by 1-n and this is alpha – X okay now we can see that this is in the you can integrate it and get a logarithmic function so I will get alpha – this is the form we will get please note alpha is nothing but this one or this is also equal to right alpha is nothing but this this is also equal to PC equilibrium to the power of 1-n now if you put that back in this equation here you will find that the denominator is going to 0 or the time will go to infinity okay so you cannot have infinite ignition time so therefore what is usually done is we try to reach something like 95% of the equilibrium pressure what is the time so we calculate time required to and that will give us a realistic ignition time okay so this is how we calculate ignition time now if we want to look at what are the kinds of ignitors that are used in the industry yes I said 30% of the pressure rise will have to be given by the igniter itself that pressurization is done by the igniter itself if you have the chamber volume 30% of that initial pressure rise has to be given by the igniter itself when the igniter burns it should fill that volume up to the pressure of typically something like 30% so it usually starts from somewhere here so we are looking at this rise only okay now let us look at what are the kinds of ignitors that are available okay there are two kinds of igniter one is called as pyrotechnic pyrogen typically the pyrotechnic igniter is based on gunpowder it is a derivative of the gunpowder and this is nothing but a composite propellant 30 to 40% metal loading if you remember when we discussed about composite propellants we said it has typically 18% of metal loading here the metal loading is increased to something like 30 to 40% so that the way this operates is it is not only the hot gases that come out but also the hot hot metal particulate matter they go and embed themselves on the solid propellant and they start a local ignition process okay so that is why you have a larger fraction of metal content in these propellants and usually they have very high burn rates if you look at very small motors then pyrotechnic is used medium sized you have a pyrogen igniter and in large solid rocket motors like PSLV stage 1 etc what you use is you have this pyrogen igniter is moving on rails from the head end to the nozzle end so as to ignite the entire motor okay now if you look at what happens when the igniter is switched on the if you look at a rocket motor the igniter is placed at the head end okay and as I said it also has particles that go and embed themselves on the propellant when these particles embed themselves on the propellant they cause local ignition in addition to that there is a hot gas flow in the chamber okay so both of these lead to ignition and if you look at the igniter igniter will have something known as both the kinds of igniter will have something called as quib which is made of this is sensitive to current and is usually made from lead or mercury filminate so when the current is supplied this is sensitive to that this starts to burn and then ignites the rest of the igniter and then this igniter will then ignite the rest of the motor okay as I said if you look at a motor like this we said that the ignition time needs to be even for a large motor less than 100 milliseconds right and I said in the beginning that if we let us say do not do this in the 100 milliseconds then what happens if there is a slower ignition then we could get into combustion instability could set in sorry one minute I said this has to be completed within 100 milliseconds now let us say we have a certain igniter mass right if we put in the required igniter mass we can achieve this within a narrow band let us say we put something more than what we should have put okay then what happens there are two things firstly if you look at a motor of this kind okay a port motor if you have a very large L by D right if you have this length of the motor to I will consider this diameter as important and not the overall diameter primarily because this will be the port it gases that are generated here if you remember this equation that we had derived DPC by DT is equal to 1 by TC a this minus portion what is it due to this is because of flow going out through the nozzle this portion is because of burning right mass addition due to burning and this is because of now what happens it takes time for this to occur right if the length is especially large length to diameter is very large then it takes a longer and longer time for the flow to go out and therefore if you look at this equation the term that is contributing in a negative sense is not going to set in for a long time as a consequence you will have in terms of pressure versus time let us not worry about this portion this is going to increase in this direction with increase in L by D right because it is going to take a longer time for the gases to go out and therefore the pressure keeps on rising and this pressure overshoot will become higher and higher and at some point could be detrimental to the motor in some cases of large L by D motors this is known to be one of the modes of failure of motors so one needs to take care of this so as to provide ignition such that this does not happen also the other trouble is with regards to ignition if you look at this figure this is of a simple port yes I am only looking at this it depends on the volume to but if you have the same volume and if you have a long pipe right if you have a stubbier volume the same one and a long pipe then if you look at both of them this is what you will find right that is what I pointed it out this is also in some sense similar to if you have a tank over a tank and if you have a very long pipeline the changes at the other end will be felt after a long time right so that is the reverse problem that is happening here right coming back I was talking about this motor here if you look at the trouble with ignition this is a very simple motor right we have a cylindrical grain but usually we talked about this earlier if you want to get the required thrust time curves in the motor then the grain has to be either a star grain or a phenoscel or something else right which means that you are going to have cuts here and cuts here and you have to ensure that the hot gases or particulate matter flows into all these crevices and ignites the entire motor in the very short time that is available which is not very easy actually okay. So and in addition let us say due to some reason we do not supply the pressure that is required by the igniter let us say we fall short then it is known to go into an instability mode if you do not supply it the required pressure then it goes into the instability mode so either if you give it more pressure you could have a hard start like what we talked about or if you give it a lower ignition it could go into instability mode so we need to have the right amount of ignition energy so as to provide typically something like 30% of the initial pressurized as well as provide a smooth ignition now we can calculate what is the amount of igniter required based on this formula the igniter mass is given by 1-PC ignition now if you look at this relationship the SF stands for solid fraction it is assumed here that the solid fraction does not give rise to the pressure right so you have to count that out and then you will get the pressure rise that we are looking for this has to be typically 30% of the equilibrium pressure this is the chamber volume and this is ignition the temperature at the end of ignition okay so using this we can calculate what is the amount of igniter that needs to be carried so as to get a good ignition now let us look at the other end of the spectrum that is the extinction part okay we have looked at the ignition part the other end of the unsteady process is the extinction let us look at that now if you remember when we discussed about burning of the web and other things we discussed something known as Liver loss and I said this is something called unburned propellant okay now let us find out why certain portions of the propellant do not burn and stay like that although it was burning up to some time and suddenly why does it quench itself okay now if you look at a missile or a launch vehicle both of these have the objective of placing its payload at a particular orbit with a particular velocity right so as I said earlier that it is more so with missiles than with launch vehicles the temperature varies from place to place as well as day and night okay and as a consequence the burn rate also varies now with all this you still have to place it into the orbit at a given velocity and at a given altitude which means that if you could have in some sense a possibility of cutting off the thrust okay then it would be a lot more easier it is very easy in liquid rockets that is you just stop the supply of the liquids or also in hybrids one of them is a liquid so you stop the supply of the liquid you will be able to stop the combustion process but how does that happen in a solid is what comes under extinction but before we do that let us find out what is the time it takes for the extinction after extinction the depressurization right if you look at the pressure time curve we are talking about this time okay what is observed here is that the combustion is completed we will see why should the combustion get completed at that point a little later now if the combustion is completed what happens to the burning surface area burning surface area we can assume it as 0 a b is 0 then what happens to a in the equation that we had derived in this equation what happens to a a is nothing but to p a b by a t a c star if a b goes to 0 a also goes to 0 so a equal to 0 then if you look at this equation what do we have this term goes off and we are left with minus pc by tc so we get the equation as now we can integrate the equation and find out what is the time it is a very simple you get ln pc must be equal to minus t by tc please remember that the tc there is a constant okay so you will get this which means that pc follows an exponential curve pc we can write it as pc equilibrium exponential of minus t by tc that is the pressure here decoys in an exponential fashion and please remember this equation is valid up to what point of this drop up to the point where the throat is choked okay if you remember the equation that we had is for a choke nozzle right so this is valid up to the condition where the throat is choked now this time is of importance because if you look at either a multi-stage launch vehicle or a multi-stage missile when you cut off the stage right if it is still burning like this because the weight is very small it could accelerate and come back and hit the mother vehicle the remaining portion of the vehicle so you would not want that to happen and you would want to know what is this time in this time it can still be thrusting right the pressure is decaying so it could still be thrusting and you do not want it to come back and hit the vehicle right so in that sense this time is of importance now coming back to the question why should propellants quench when they are depressurized or why does it quench or why should there be a sliver loss right if you remember our discussions earlier we had said that there will be some portions of the propellant that will remain unburnt if you look at the if let us say this is the cross sectional view of the rocket motor there will be some portions that will remain unburnt now to ask ourselves this question why should it not burn up to this point it was burning right and why does not it certainly or why should it suddenly stop burning the answer lies in this fact that suddenly the burning surface area decreases if you look at it it was earlier occupying the entire this entire circumference and suddenly it ceases and becomes only in some portions that you have a propellant right so what happens the burning surface area AB suddenly changes if AB changes suddenly and if you have a propellant with high N or a medium N also I mean burn rate pressure index N is moderately high right not we are not looking at 0.8 or something we are even if it is 0.3 or 0.4 what happens to the equilibrium chamber pressure when this happens when the AB suddenly changes or it is a larger burning surface area and suddenly it decreases to a smaller burning surface area if you look at our expression for equilibrium pressure right so if AB changes suddenly then the pressure also changes suddenly and if AB drops pressure drops suddenly in a sense you are depressurizing the motor okay so people have done this experiments and try to find out what happens in this case what happens when the motor is depressurized or when a propellant is depressurized this is one of the ways in which you can stop the propellant from burning further if you depressurize it prevents the burn propellant from burning or it inhibits the propellant from burning later on let us see why this should happen it is something like this let us say a propellant is this is the burn rate versus time that I have let us say a propellant is burning at some rate here suppose you depressurize it okay then at the lower pressure which you bring it to let us say it has a burn rate something like this right it has been known that if you do this process in a very small time that is if your DPC by DT is large right then the propellant tends to quench if you do it very slowly it will go to this burn rate if you do it very rapidly at some point it could do this okay if you do it further rapidly it is seen to quench like this okay. So there is a critical DPC by DT beyond which the propellant ceases to burn and people have kind of done the study wherein to find out if let us say you have an initial pressure and this is the DPC by DT the curve follows something like this if for an initial pressure somewhere here if you are using let us say this depressurization rate then it will it will quench but let us say if you are for the or it will not quench and let us say if you are this is not quench and let us say you are here this will lead to quenching in a sense this line defines the boundary at which the quenching or the not quenching happens okay so this line defines the boundary at which quenching and no quenching takes place so if you are above that it will quench if you are below that it will not quench and also please remember this quenches still even when there is a burning possible at that lower pressure it is not as if we are taking it below a pressure where the propellant ceases to burn right. The answer for this is in some sense in the characteristic time of characteristic conduction time scale that is the for the solid the characteristic time scale is much much greater than the characteristic time scale for the gas we will discuss this a little later as to why it should be for the solid it should be higher than the gas so in a sense the gas responds very quickly to the changes whereas the solid is very very slow and responding to changes typically it is of the order of a 100 times or 1000 times 100 to 1000 now what happens in this case is if you have these gas respond very quickly let us say we have the situation wherein the propellant is burning in this fashion let us say there is a flame here now if you depressurize this the flame tends to move up because the pressures have reduced and the flame tends to move away from the surface when this happens but the solid tends to feel that it is operating at the previous condition itself and tends to pump in more gases as a consequence you are filling in more inerts in a sense and this causes the flame to move even further away whereas if you look at what happens inside the solid the solid will need more and more heat to operate at a lower and lower temperature so in a sense you are moving away from the situation where at the point where it was burning the solid was getting the ample heat that is required for it to continue burning you are now moving into a situation wherein it needs more heat than what it is getting and the heat is also decreasing so in a sense you are pulling away from the stable point and therefore it tends to quench okay that is the reason in some sense for this quenching we will stop here and continue in the next class the next class we will discuss erosive burn okay thank you.


Imperial Highness, the Crown Prince of Japan. Imperial Highness, it is a great honor to welcome you to our country in two months. Thank you very much. Thank you. Thank you. Please add one more. And that's another. Ambassador Okawara, who is that? That's a great reporter. Nice to see you. Nice to see you. Nice to see you. And Mr. Yasajima. How do you do? Get in my house. Well... And that's Ambassador Okawara. Nice to see you there. Imperial Highness, I think you're going to do it this way. I have a few photographs and so forth, and then we'll get back in here for a few minutes. I agree. I agree with you. Yes. Well, it's easy. No, it's not easy. I'm just a few minutes here on the wheel. We were very sorry to hear about this majesty, all of these receptions from his operation, and we regret that it's shortened your visit here. Thank you very much, Mr. President. Thank you very much, Mr. President. Before I departed Japan, I met my father, the Emperor, and he sent you the best regards. Oh, well, please return mine to him. We remember with great pleasure, the warmth from the hospitality that he extended to us when we were there. I got the presents from my taxis, and I got the gifts from the inspector. And we call all the students. Oh, so you can do that when that returns to you. Our first meeting was long before I was president. I was there as Governor of California and been sent to represent the president. Again, the way... Hi, Mr. President. Hi, how are you? It's certainly nice to see you again. Good to see you. Pleasure, thank you. You look excellent as usual. Well, I feel good. Thank you, Mr. President. The chair is there. Thank you. I've already seen your good friend. That's just been warmed up by a crown prince. Well, I'll try to act appropriately. He's a crown prince of Cook County. Actually, I'm not from Cook County, Howard. Did you know that? Yeah, I did not know that. I'm from Belmont, across from Belmont. You also told me that you were the third best tennis player on your block. You must have had relatives in my hometown, Dixon. You know, the funny thing, the Dixons are all very dear friends. And sure with Dixon was Lieutenant Governor of Illinois when I was a freshman in the Illinois House. He was Lieutenant Governor under Adley Stevenson. And that whole family had been very dear friends. But I'm not sure that those Dixons are relations. Well, a Dixon, they were all descended from Father Dixon. They called him Father Dixon. He wasn't a priest. But he had the ferry across the river there, and that grew into a town. Judge Mike Kinney from Madison County. Pretty good. The walk-in gets more distinguished for the day. Crown Prince of Japan was there. He's the Interstin Fellow, Mr. President. Yes, he is. He seemed to be genuinely interested in the conversation. As I figured out, he's about 59 years old. And I kept thinking. I'm the first time I saw him some years ago there at the palace. Well, I remember some pictures of him when he was a young fellow. When he was a kid. I don't remember seeing any pictures of him. Wait a minute. I said 59, 57. I'm sorry, 57. But you know the other unique thing about him? This is the oldest royal family in the world. When he becomes the emperor, he will be the 125th emperor of that family. To be emperor. 125th. Isn't that something? Well, listen. You know what I want to talk to you about. I just would like to. All right. Bob Graham from Florida. I know. Let's see what you've got. Right? Yeah. Let's chair over there. No, you're just a puzzler. Well, I was telling Mr. Baker that I think I need to talk about it. I'd also like to chat a bit about the speech that I am going to give tomorrow to the OAS on the Central National Peace Force. All right. But do you want to go first? Well, it's your agenda, so why don't we do your subject first? Well, you know what I wanted to do. And I know you understand appointing judges, which is you're the 300th governor. Yes. And you're the governor. We didn't have the Senate confirmation before. Did you in California do the Senate confirmed tradition? No. No, I just did. But I had filed with someone who had kind of politicized the whole appointment process. And I made up my mind and made the declaration that I would take the appointment of them out of politics. So I set up a whole set up of groups, like the legal profession in the district where everything was, and a panel of judges, and then finally the governor or the states, our association board of governors. And none of them knew about each other. And I would get a rating from all of them. And then they would put them down on like a scorecard here, which group it was and what was the rating. And the rating was from not qualified, not through qualified, to well qualified, to ex-mig qualified. And I went by that score in appointing them. Sometimes there would be some that would be virtually tied. Well, then I could have the lead way to say, well, if you're going to take it and end it. They're going to try to show questions at me about domestic matter, and I'm going to try to shut them on that. Yes, sir. Oh. Yeah, well, thank you. Thank you. Thank you. Yes, sir. Well, because I would like to hear if you were better than the person. No.  The work pulled out, or is he going to meet with you today, or has he met with you? Kevin, I'm not changing my position, but I'm not going to take any questions out of you. You may not change your position, but has he changed his? Would you accept his withdrawal, Mr. President? I start answering. I've broken my word. Should we expect an announcement today? Are you going to be pleased? This way, please. Thank you. Sir, if you have a message of Mr. Kovachev. I shall transmit the deal to the personal blood and the blood message that Mr. Kovachev has made. It is a very positive in content. About the summit? At the Austrians in the Worship World. That subject is not only of concern to press men, it is of concern to the entire world. Thank you. That is their position. That is their profession. Mr. President, please allow me to welcome you to the summit. Ladies and gentlemen, I wish you the best of health, and good luck to the Americans, and to the people of my country. Thank you. Our country is here. Very good. We just kicked the Russian political bureau from out there. Is that right? It all warmed up for him. I know it's your governor up there who won't start commuter traffic between Russia and Alaska. We used to have. Is that right? Yeah. And the Ford administration we have. Yeah, it was a really popular thing. It moved from Nome over to Abarask and to Leningrad in Moscow, and then back to Abarask and then to Nome again. It was a great trip. I never get to take it myself. I wanted to talk to you about our Dreyfus case. Our Dreyfus case? I'll say that I'm teed off is an understatement of the year and injustice of the income.