[00:00.000 --> 00:00.900]  My name is Davide.
[00:01.500 --> 00:05.380]  I'm an engineering manager at a space company called ABL Space System.
[00:05.580 --> 00:08.180]  If any of that sounds interesting to you, come and find me after the talk.
[00:09.640 --> 00:14.200]  So, the title of this talk is Celebrating Dead End in the Jet Engine Revolution.
[00:14.600 --> 00:17.980]  And there's kind of a lot to unpack in there.
[00:18.000 --> 00:20.880]  So, let me start by actually asking you a question.
[00:21.100 --> 00:24.680]  How many of you have before been on a plane?
[00:24.820 --> 00:27.200]  Who of you... raise your hand if you've flown on a plane before.
[00:28.600 --> 00:29.160]  All right.
[00:29.580 --> 00:33.620]  How many of you have flown on a plane that was not a jet?
[00:35.320 --> 00:36.100]  That's a good number.
[00:36.300 --> 00:38.860]  How many of you have flown a plane yourselves?
[00:39.160 --> 00:40.160]  How many of you are pilots?
[00:40.500 --> 00:41.780]  This has nothing to do with the talk.
[00:41.780 --> 00:44.240]  I just need to know who I need to look out for.
[00:45.480 --> 00:46.020]  All right.
[00:46.180 --> 00:49.140]  So, there are two things that are interesting about this question.
[00:49.400 --> 00:51.900]  The first is how many of you raised your hand, right?
[00:52.240 --> 00:57.180]  And sure, we are a self-selecting group of nerds that flew in to talk about nerdism.
[00:58.040 --> 01:01.720]  And mind you, 80% of the world has never been on an airplane.
[01:02.060 --> 01:04.840]  And even in America, 10% to 15% of people have never been on an airplane.
[01:04.980 --> 01:08.360]  But in this room, you know, most of us has.
[01:09.180 --> 01:14.380]  And it's almost trite to talk about how familiar that experience is.
[01:14.580 --> 01:21.360]  And, you know, how ubiquitous airplanes are.
[01:22.380 --> 01:26.140]  The other thing that's interesting about that is that I didn't have to define what a jet is.
[01:26.500 --> 01:31.760]  And, again, we're a pretty self-selecting group of nerds that came to a talk that literally has jet in the title.
[01:33.340 --> 01:34.980]  But, actually, that's a good place to start.
[01:35.080 --> 01:36.980]  So, let me ask you, what is a jet?
[01:37.180 --> 01:37.880]  It's a real question.
[01:38.300 --> 01:38.860]  What's a jet?
[01:40.720 --> 01:41.580]  What's a jet for you?
[01:41.580 --> 01:45.880]  It's determined to produce high volumes of thrust.
[01:46.040 --> 01:48.100]  Okay, well, somebody knows what they're talking about.
[01:48.440 --> 01:50.220]  Yeah, it's a type, exactly, it's a type of engine.
[01:50.980 --> 01:51.700]  What else?
[01:52.280 --> 01:53.140]  It's in line.
[01:53.580 --> 01:55.200]  It's in line, yes.
[01:57.960 --> 02:00.220]  It claims to have a single moving part, yes.
[02:01.060 --> 02:02.760]  Yeah, exactly, all of these are correct.
[02:02.960 --> 02:05.320]  It's a type of engine.
[02:05.820 --> 02:06.960]  It's also a type of plane.
[02:07.120 --> 02:09.580]  People will refer to planes as jets, right?
[02:10.040 --> 02:21.320]  And that's interesting and profound because inventing this type of propulsion system really opened up the ability to create new types of airplanes.
[02:21.480 --> 02:32.700]  But, okay, so before we get too much into the weeds here, and we talk about what these dead-ends are, I don't know what, like, I just want to get a little bit on the same page about what is what, right?
[02:33.340 --> 02:34.300]  This is a plane.
[02:34.500 --> 02:37.840]  This is, in fact, the first ever plane, the Wright Flyer.
[02:38.600 --> 02:41.720]  As it's taking flight for the first time in December 1903.
[02:43.040 --> 03:00.580]  And so the way this works is, like, the four forces of flight, if you're not familiar, are simply lift generated by the wings, opposed by the weight generated by the planet, and the thrust generated by the power plant, that gets opposed by the thickness of the air.
[03:00.580 --> 03:06.480]  Or, as the pilots in our myths will know, these are the real, actual four forces of flight.
[03:06.900 --> 03:18.620]  Anyway, so you bring up, so here's the flyer, you got, like, the propellers back there that are pushing it forward, there are the wings that are pulling it up, the whole structure is pulling it down, and the thickness of the air pushing it back.
[03:19.180 --> 03:22.640]  So these forces are opposed pair-wise.
[03:23.580 --> 03:26.040]  So what's interesting about that is actually this guy right here.
[03:26.300 --> 03:32.760]  So that's the engine back there, and that's, like, a big propeller that's pushing the airplane, right?
[03:32.860 --> 03:34.260]  That's the power plant.
[03:34.320 --> 03:37.700]  That's, like, how the first airplane was propelled.
[03:37.740 --> 03:39.720]  It was, like, something that looked like this.
[03:39.720 --> 03:48.120]  And, you know, this is a, at this point in history, this is a very well-understood entity, the opposing piston engine.
[03:49.440 --> 03:58.200]  And what this really did, you know, it attached to, with a chain, to the propellers, spun the propellers, the propellers moved the air forward, and pushed the airplane forward.
[03:59.180 --> 04:14.640]  Something I actually want to clear up here that's sometimes a misunderstanding is that technically all airfoil, so all things that move in a fluid by thrusting it backwards are technically jet engines, right?
[04:14.840 --> 04:21.940]  Technically, every airplane and every boat move by propelling the fluid that they're in backwards and reacting to it.
[04:22.060 --> 04:28.660]  So what really makes a jet engine is not the fact that it's just exhausting air at high velocity.
[04:30.920 --> 04:31.780]  Oh, okay.
[04:31.780 --> 04:44.820]  What makes a jet engine a jet engine is that it does so by exploiting a different set of phenomena.
[04:45.100 --> 04:52.400]  So in an opposing piston-propeller combination, the engine is generating some rotating kind of motion to spin the propeller.
[04:52.520 --> 04:59.020]  Whereas in a reaction engine, in a pure reaction engine, the combustion is more directly generating the propelling force.
[04:59.020 --> 05:08.180]  The simplest of such schemes could be, you know, a balloon or a rocket engine where you just have like some gases that are expanding in a confined space.
[05:08.180 --> 05:14.680]  They get exhausted at the back, pressure drops, velocity increases, and you react against it.
[05:16.140 --> 05:19.840]  There are largely two types of such jet engines.
[05:20.100 --> 05:24.880]  This is basically a rocket engine, and it's non-air breathing.
[05:24.880 --> 05:42.980]  Whereas the air breathing version takes the air from the surrounding environment instead of carrying it, carrying it itself and ignites it, uses combustion to expand the gases and increase the velocity and, you know, react against whatever it's attached to.
[05:43.660 --> 05:44.860]  There is a third type.
[05:45.220 --> 05:46.400]  This is a turboprop.
[05:46.500 --> 05:47.400]  We're going to talk about this later.
[05:47.400 --> 05:57.860]  This is kind of like a mix of the two where you use the part of the energy generated by the reaction engine to spin a shaft.
[05:58.680 --> 06:03.480]  But really, like, when I talk about jet engines, this is what I'm talking about, right?
[06:03.620 --> 06:04.400]  You've all seen this.
[06:04.440 --> 06:24.200]  If you're here, probably, this is the basic idea of a modern engine is you have a compressor that takes the air, squeezes it, it combusts it, and then uses the high-velocity exhaust to spin the turbine, to spin the compressor, and then the remaining of the energy is exhausted through a converging,
[06:24.260 --> 06:30.200]  diverging, the larval nozzle, and that creates a high-velocity flow that you react against.
[06:30.580 --> 06:36.920]  And if this does not seem like an obvious idea to you, it shouldn't, because it isn't.
[06:36.920 --> 06:40.000]  And it took quite a bit to get here.
[06:40.400 --> 06:46.260]  And, you know, we see these things around all the time, and we're used to them.
[06:46.360 --> 06:49.480]  So to us, this seems obvious, because we have the burden of knowledge.
[06:49.720 --> 06:55.380]  And I selected this specifically just to prove that in the 90s, airlines were cooking on levels never seen before.
[06:55.380 --> 07:00.240]  But, you know, like, stuff today is, like, just as fancy.
[07:00.560 --> 07:10.740]  And, you know, this engine, this technology has become so commonplace that it has become, you know, these are jets, as we were talking about.
[07:10.940 --> 07:12.440]  This was the jet set.
[07:13.120 --> 07:15.860]  There was the jet age.
[07:16.060 --> 07:24.900]  It was a technology that became so impactful that it defined the era in which it happened.
[07:25.640 --> 07:34.660]  And so, I think the question for us here is, how did this come about?
[07:35.020 --> 07:43.880]  And so, if you go and look, if you go and look at the Wikipedia page for, you know, what's the history of the jet engine?
[07:44.040 --> 07:50.440]  And you try and find out, you know, what did this really look like when it came about?
[07:50.440 --> 07:59.580]  What were things like in, you know, early 1900s where you had, like, this very strange contraptions that the Wrights were creating?
[07:59.580 --> 08:03.960]  How did we go from there to the modern airliners that we saw?
[08:04.040 --> 08:08.300]  Well, you're going to get a story that goes something like this.
[08:08.400 --> 08:09.940]  And it doesn't matter if it's Wikipedia.
[08:09.940 --> 08:11.780]  It's, like, some documentary.
[08:11.780 --> 08:12.960]  I watched all of them.
[08:13.380 --> 08:15.140]  And the story goes something like this.
[08:15.280 --> 08:21.000]  So, the Wrights invented this, and then airplanes got, you know, a little bit better, but still kind of clunky during World War I.
[08:21.560 --> 08:26.600]  And then they got a little bit heavier and better during the 20s, and then a little bit better and heavier during the 30s.
[08:26.760 --> 08:33.060]  And then by the time World War II rolled around, we had pretty mean-looking things like this that were, like, shooting at each other.
[08:33.060 --> 08:45.340]  And so, Germany and Britain, on opposing sides of the war, they started designing weird contraptions such as this and such as this to try and outdo each other.
[08:45.680 --> 08:49.380]  And the Nazis, who were meaner, came up with the meanest-looking airplane, which was this.
[08:49.520 --> 08:55.180]  But then somebody else was in town and decided to use a completely different technology to end this particular confrontation.
[08:56.240 --> 09:01.860]  And so, we ended up with a bunch of, like, these jet engines, and we didn't really know what to do with them, and boom, we have the 777.
[09:03.460 --> 09:04.000]  That's it.
[09:04.260 --> 09:05.080]  That's the story.
[09:06.480 --> 09:15.040]  And if you heard the story before, you might be like me, and you might find that this invites more questions than it really answers.
[09:16.400 --> 09:18.080]  It's not all here, right?
[09:18.720 --> 09:28.220]  There have been so many other... there have to have been so many other things happening before we actually landed where we are today.
[09:28.440 --> 09:32.640]  Like, there are, like, you know, what... like, all of these questions, like, what was wrong with piston engines?
[09:32.820 --> 09:34.660]  Why couldn't it make the plane faster?
[09:35.160 --> 09:37.680]  Where did the idea of a reaction engine come about?
[09:38.240 --> 09:38.640]  Why?
[09:38.840 --> 09:39.380]  Who had it?
[09:39.540 --> 09:43.760]  Why did it take 30 years, 40 years, 50 years for it to mature?
[09:44.000 --> 09:45.240]  Why did it mature when it did?
[09:45.780 --> 09:52.720]  And so, I want to try and answer some of these questions today, and I want to try and do the impossible.
[09:53.080 --> 09:54.960]  We have the burden of knowledge.
[09:55.080 --> 09:56.640]  We do know that the systems work.
[09:56.820 --> 10:04.980]  We do know that the systems are wildly successful, and we do know that the modern airplane uses a jet to propel itself.
[10:05.100 --> 10:06.060]  But let's pretend that we don't.
[10:06.400 --> 10:11.920]  Let's go back to the early 1900s, and let's try to invent the jet engine.
[10:13.260 --> 10:14.560]  So, our task is this.
[10:14.720 --> 10:18.140]  We have an airplane, and, man, we just want to go.
[10:18.340 --> 10:20.500]  We just want to go higher and faster.
[10:20.660 --> 10:21.200]  How do we do it?
[10:23.160 --> 10:24.660]  So, we have a couple of options.
[10:25.160 --> 10:26.540]  What power plants do we use?
[10:26.640 --> 10:27.940]  Well, here you see a piston engine.
[10:28.640 --> 10:29.840]  We could try a steam engine.
[10:30.020 --> 10:30.680]  It's been tried.
[10:30.860 --> 10:32.060]  It didn't really work.
[10:32.480 --> 10:33.800]  Why didn't it work?
[10:34.920 --> 10:35.960]  Because it was too heavy.
[10:36.240 --> 10:36.500]  Exactly.
[10:36.940 --> 10:41.480]  Heavy is the single most important thing when we're thinking about stuff that flies, right?
[10:41.640 --> 10:42.780]  You put metal in the air.
[10:42.900 --> 10:44.800]  You have to carry everything.
[10:45.080 --> 10:49.240]  So, actually, what we care about is not exactly absolute weight.
[10:49.900 --> 10:52.640]  Specifically, in terms of the power plant, we care about power density, right?
[10:52.740 --> 10:53.420]  We care about...
[10:53.420 --> 10:56.260]  We can accept a large engine that generates a lot of power.
[10:57.720 --> 11:02.020]  So, what we really care about is power per unit mass.
[11:02.480 --> 11:04.920]  And this was not really good, really good at that.
[11:05.480 --> 11:07.400]  This, however, was a lot better.
[11:07.520 --> 11:11.200]  This is like, in fact, the first engine to ever fly was what was on the right flyer.
[11:11.340 --> 11:14.860]  So, you know, we can try and improve on this.
[11:15.760 --> 11:17.960]  I'm probably stating the obvious here.
[11:18.120 --> 11:18.860]  So, sorry, pilots.
[11:20.140 --> 11:24.260]  But that engine works like this.
[11:24.520 --> 11:27.300]  So, good old sack squeeze, bank blow, right?
[11:27.740 --> 11:32.460]  Or for the more educated amongst us, intake compression, power stroke, and exhaust.
[11:32.720 --> 11:38.360]  So, the idea is you take some air, you squeeze it, you add some fuel to exhaust it, increase the pressure.
[11:38.460 --> 11:40.660]  Pressure pushes down the piston.
[11:40.740 --> 11:46.560]  And you do this in a coordinated fashion and you get, like, something like this, right?
[11:46.560 --> 11:52.900]  So, each cylinder at any given point in time is at a different cycle.
[11:53.200 --> 11:58.400]  And you organize them in such a way that they're all pushing down on this crankshaft.
[12:00.060 --> 12:03.120]  And if all of this goes well, it creates a rotating motion.
[12:03.200 --> 12:04.880]  You attach a propeller to it, you're good to go.
[12:05.480 --> 12:06.960]  So, how can we make this better?
[12:06.960 --> 12:11.260]  Well, obviously, we can add more cylinders, right?
[12:11.560 --> 12:13.300]  We add a lot more cylinders.
[12:13.520 --> 12:16.060]  Each one of them contributes to the downstroke a little more.
[12:16.240 --> 12:17.420]  And we get more power.
[12:17.560 --> 12:18.880]  More power, we go faster.
[12:19.140 --> 12:20.040]  And that's great.
[12:20.980 --> 12:30.380]  One problem with that is that this engine works by basically a combination of, like, a lot of little explosions.
[12:30.380 --> 12:35.200]  And so, each one of these explosions is responsible for turning the crankshaft by a certain amount.
[12:35.420 --> 12:41.760]  The more cylinders you add, the smaller that amount is, the more complicated the system becomes.
[12:41.980 --> 12:45.280]  And more importantly, there's only 360 degrees in the turn.
[12:46.160 --> 12:48.700]  You have an upper limit to how many cylinders you have.
[12:50.000 --> 12:51.420]  We could make the cylinders bigger.
[12:51.720 --> 12:55.000]  For each cylinder that's bigger, you'll just get, like, more oomph.
[12:55.620 --> 13:01.120]  But that, you know, you can do that to an extent, and then it gets a little harder to cool.
[13:01.600 --> 13:13.120]  You can make the cylinders longer, but then that increases some of the inertial loads on the rotating parts, and then ultimately reduces your power density.
[13:13.280 --> 13:17.140]  So, you can make these things bigger, but up to a point.
[13:17.840 --> 13:19.140]  And then there is another problem.
[13:20.180 --> 13:22.920]  This is what happens when you have, like, 36 cylinders.
[13:22.920 --> 13:26.740]  This is, like, the largest engine in terms of cylinder count ever made.
[13:27.140 --> 13:28.080]  There's another problem.
[13:28.180 --> 13:33.120]  The other problem is that airplanes have this pesky tendency to go up in the air, right?
[13:33.160 --> 13:34.540]  And what happens when you go up in the air?
[13:35.600 --> 13:37.060]  The density drops, right?
[13:37.160 --> 13:39.920]  There is, like, less air to go around.
[13:40.560 --> 13:51.960]  And so, if your main mechanism to generate energy is combustion, you just have, like, less stuff to use to combust.
[13:51.960 --> 13:54.940]  So, this actually was a huge problem in the early 1900s.
[13:55.040 --> 13:59.740]  And this is the first thing that we really need to solve.
[13:59.880 --> 14:03.340]  And it was solved by the use of a compressor.
[14:03.760 --> 14:06.280]  So, this is called the supercharger scheme.
[14:06.540 --> 14:17.460]  And it simply uses some of the power from the crankshaft that would otherwise go directly to the propeller to compress the air before it enters the cylinders.
[14:17.460 --> 14:21.800]  This makes the combustion more efficient and lets the plane fly higher.
[14:22.600 --> 14:23.260]  Isn't that nice?
[14:23.480 --> 14:24.760]  There's only a problem with this.
[14:24.820 --> 14:25.900]  There was a couple of problems with this.
[14:26.220 --> 14:31.160]  The main problem is that, obviously, it takes energy off of the main combustion...
[14:31.160 --> 14:34.940]  Sorry, off of the main rotating shaft.
[14:34.940 --> 14:38.380]  So, this guy right here, a ghost for a tow.
[14:38.640 --> 14:40.020]  He'll come back later.
[14:40.660 --> 14:42.840]  He actually had a pretty good idea.
[14:43.200 --> 14:49.040]  And his idea, in about 1920, he was tasked to invent this.
[14:49.600 --> 14:51.060]  Well, he wasn't tasked to invent it.
[14:51.100 --> 14:54.040]  He was tasked to solve the problem and he invented this.
[14:54.440 --> 14:56.040]  This is called a turbocharger.
[14:56.040 --> 15:01.000]  And this is maybe the first really significant step towards the jet engine.
[15:01.160 --> 15:11.000]  So, the idea here is that you take the exhaust gas from your engine and you stick it through a duct.
[15:11.000 --> 15:21.740]  And then you use that hot and fast gas that's coming out from the engines, from the cylinders like a bed out of hell, to spin the turbine that then compresses the air.
[15:22.540 --> 15:27.800]  This is better because it doesn't absorb any energy from the shaft.
[15:27.960 --> 15:29.300]  And, in fact, it's just using the...
[15:31.320 --> 15:33.800]  Very famously, these engines are extremely inefficient, right?
[15:34.100 --> 15:45.200]  And they are because they convert about 20 to 30 percent, well, at the time at least, 20 or 30 percent of the power into motion and the remaining into noise and heat.
[15:45.340 --> 15:48.840]  So, you capture some of that with the system.
[15:49.400 --> 15:50.060]  That's great.
[15:50.060 --> 15:56.240]  That lets us go really high up and it keeps our fuel consumption the same.
[15:56.360 --> 15:58.460]  So, our specific power has just gone up.
[15:58.580 --> 15:58.900]  That's great.
[15:59.380 --> 16:08.620]  So, one thing that people figured out when doing this was that the amount of exhaust that was coming out of there was actually really significant.
[16:09.020 --> 16:13.160]  And when it was exhausting from that pipe, it still had energy.
[16:13.660 --> 16:18.740]  And so, the next thing that we can do and we can ask ourselves is, how can we use that?
[16:19.020 --> 16:22.180]  What schemes exist to make use of that excess energy?
[16:22.380 --> 16:23.740]  We're already paying for it.
[16:23.820 --> 16:24.680]  We've already burnt it.
[16:24.820 --> 16:26.380]  So, how can we put it to some use?
[16:26.380 --> 16:33.420]  So, there's a lot of these schemes and these became, not all of these were implemented.
[16:33.660 --> 16:47.220]  But the idea behind this, it's called the turbo compounding engine, is to use some of that energy to actually drive... well, in the first iterations, it was to drive the crankshaft.
[16:47.220 --> 16:50.340]  So, this is the first engine in which this was used, the Rolls-Royce C.
[16:51.580 --> 16:58.140]  And what this engine had was a little turbine.
[16:58.420 --> 17:00.400]  It actually was like a Whittle-type turbine.
[17:00.520 --> 17:01.420]  We're going to talk about that later.
[17:02.420 --> 17:13.500]  And even though it didn't really ever fly, it used the entirety of the exhaust to drive this turbine that then added that power to the crankshaft.
[17:13.960 --> 17:20.820]  And by doing this, you know, again, increased the specific power.
[17:21.060 --> 17:38.200]  And so, what's interesting about this idea is that even though it was sort of a dead end, it was interesting when we started realizing that you can use that exhaust not just to drive the compression, but to actually drive... there was enough power in that to drive additional power to the crankshaft.
[17:39.560 --> 17:47.000]  The next... another engine that did this, and that's only worth mentioning because it did this with a different type of compressor.
[17:47.160 --> 17:50.040]  We're going to talk about this later, else it was an actual type compressor.
[17:50.060 --> 17:51.440]  It was the Alizon 1710.
[17:51.700 --> 17:52.680]  This also never flew.
[17:55.260 --> 17:58.560]  The next thing after this was that...
[18:00.100 --> 18:06.940]  you realize that the flow that's coming out of that turbine still has energy.
[18:07.380 --> 18:13.700]  And so, instead of like driving that flow towards the crankshaft, hey, what if we use that flow just to accelerate the airplane forward?
[18:13.920 --> 18:16.740]  It's a little bit of a reaction engine in there, right?
[18:17.160 --> 18:28.460]  And the WASP had such a scheme, but really like the... the goat for this was the Napier 175 Nomad.
[18:29.040 --> 18:31.840]  And this guy... this guy had it all.
[18:32.660 --> 18:35.160]  So, there's a lot going on here.
[18:35.640 --> 18:38.780]  This is one of my favorite contraptions ever invented.
[18:38.940 --> 18:40.860]  Talk about it like a glorious dead end.
[18:41.140 --> 18:46.940]  So, it had a gigantic opposing piston engine.
[18:47.200 --> 18:52.420]  And the way this worked is that the... so the air would come into here.
[18:52.600 --> 18:53.520]  It would get compressed.
[18:53.660 --> 18:55.020]  The compressor was spun by a turbine.
[18:55.120 --> 18:55.780]  We're going to talk about that.
[18:56.020 --> 18:58.860]  Then it was like the air... you know, the compressed air gets hot.
[18:59.000 --> 18:59.800]  So, it got cooled.
[18:59.820 --> 19:01.820]  So, it was more dense.
[19:01.940 --> 19:07.100]  And then that would go into like this... another compressor that would send it to the engine.
[19:07.240 --> 19:09.320]  The engine would burn, create the exhaust gases.
[19:09.460 --> 19:10.800]  And then here's a new invention.
[19:11.740 --> 19:23.500]  There was a combustion chamber downstream of this engine to further accelerate those gases so that it would go to the turbine, spin it, and keep this whole thing going.
[19:23.920 --> 19:29.540]  After this happened, this turbine wasn't... wasn't just only doing all the compressing.
[19:29.660 --> 19:33.520]  It was also spinning one of the two propellers in the front.
[19:34.420 --> 19:39.720]  And so, you know, you squint here and you're like, have I seen this before?
[19:40.560 --> 19:46.180]  You show in the second day with some of the complication here with the double prop.
[19:46.380 --> 19:50.160]  And it looks even more pure, right?
[19:50.300 --> 19:51.260]  You have an air intake.
[19:51.440 --> 19:59.140]  You have... you have a lot of what looks like a jet engine, but it's just going through this gigantic, super complicated contraption.
[20:00.020 --> 20:02.900]  And this was never developed further.
[20:03.040 --> 20:05.260]  This was like one of the greatest dead ends.
[20:05.740 --> 20:22.120]  And the reason it was at that end is that people started realizing that the amount of thrust that you would get through the... through that little, you know, turbine was starting to compare favorably with the amount of power that you were getting from the piston engine.
[20:22.360 --> 20:29.280]  So if you go this direction, you know, we have like some of the building blocks, but it looks like this is not going to do it.
[20:29.400 --> 20:32.560]  Like, we're not going to get really far by keeping a piston engine in the loop.
[20:32.680 --> 20:34.980]  So let's, let's think about something else.
[20:35.100 --> 20:38.980]  Is there something that we can do that is not like evolving the piston engine, like with the crankshaft?
[20:39.220 --> 20:43.460]  Well, if we roll back to the early 1900s, this is actually a pretty interesting thing.
[20:43.540 --> 20:48.300]  This guy, Loren, he had, he was a French soldier.
[20:48.420 --> 20:50.520]  He actually had a really good, a bunch of really good ideas.
[20:50.600 --> 20:51.840]  He invented a ramjet.
[20:52.400 --> 20:53.720]  We're going to talk about this in a bit.
[20:55.100 --> 21:06.040]  What this is, is a very fascinating dead end where we, we do have a piston engine, but the piston engine is not like the crankshaft is not used for anything.
[21:07.000 --> 21:12.080]  All this is used for is to accelerate air out of those nozzles out there.
[21:12.220 --> 21:23.220]  And the idea of, so in this scheme down here, the idea was to put these on the, on the wings of planes to propel them, only by using the reaction generated by compressing air in the cylinders.
[21:23.220 --> 21:35.640]  Unfortunately, this doesn't work so well because this type of, this type of engine, like it really exhausts high pressure and low velocity, kind of a kind of gas and low volume, more importantly.
[21:36.540 --> 21:38.580]  And you know, it wasn't, it wasn't great.
[21:38.700 --> 21:44.900]  So another scheme that came up in the, in the early 1900s was this.
[21:45.680 --> 21:46.620]  It's still used.
[21:47.480 --> 21:51.940]  A is a, is a motor and B is a compressor.
[21:52.200 --> 21:58.120]  And so it basically uses that to create a, like a steady flow compressed air that goes into a combustion chamber.
[21:58.580 --> 22:15.540]  That's marked with D and the, the compressed air and fuel mix in there, they get, it gets ignited and then goes through, um, what essentially is a venturi that sucks in the air and sort of like multiplies the amount of, uh, um, of, of air going through it, uh, increasing the, increasing the reaction.
[22:18.100 --> 22:27.440]  Um, there was another, there were a couple of like iteration of this with like different, um, architectures for the, for the igniters, but it was the same idea.
[22:27.940 --> 22:37.900]  Um, one problem with this is that, uh, it used like, this sort of like converging, diverging kind of architecture, um, that, uh, is, is not great.
[22:38.160 --> 22:52.740]  And so the, um, the next iteration that like sort of did the opposite, um, used the, a converging, diverging, sorry, diverging, converging, uh, long tube to take, uh, to, to take in the gases.
[22:52.900 --> 23:02.520]  So the idea here is at A you have a motor that's spinning the compressor at B that's taking in the air, uh, in, uh, in the injector C.
[23:02.720 --> 23:11.580]  At C the air gets ignited, uh, creates an area of low pressure and does this low pressure flow accelerates along the tube, uh, and sucks in more air.
[23:11.740 --> 23:19.320]  Uh, and the tube is really long so that like by the time the, the gas gets out, it's at the same temperature as, uh, uh, as the outside air.
[23:19.480 --> 23:20.600]  So it doesn't allow for backflow.
[23:21.520 --> 23:25.220]  Um, uh, this was, this, this never worked.
[23:25.480 --> 23:33.380]  Um, but the general idea here was to try and accelerate gases.
[23:33.600 --> 23:34.140]  I'm not doing time.
[23:34.760 --> 23:40.860]  It was trying to accelerate gases by, um, by exploiting a combination of combustion and low pressure, right?
[23:41.180 --> 24:00.500]  Uh, this is the kind of power, uh, uh, specific power that could have been, uh, used for aircraft, aircraft propulsion.
[24:02.940 --> 24:07.540]  So here's a different idea, different, but similar, but we're, we're starting to go somewhere.
[24:07.700 --> 24:16.540]  Instead of using an, like an engine that is sort of like separate, uh, why don't we put the engine inside the engine, uh, inside our, you know, prime mover.
[24:16.760 --> 24:21.900]  And so you have like a rotating engine here that spins a compressor.
[24:22.760 --> 24:26.820]  And then in line, the airflow gets ignited and gets ejected.
[24:27.380 --> 24:29.780]  This is starting to look a lot more like a jet engine.
[24:29.880 --> 24:34.180]  It's basically a jet engine where the compressor stage is powered by a piston engine.
[24:34.360 --> 24:35.120]  And this has a name.
[24:35.240 --> 24:36.020]  It's called the motor jet.
[24:36.280 --> 24:41.860]  And the first motor jet was this Italian contraption called the Campini Caproni CC2.
[24:42.540 --> 24:45.520]  Uh, and it actually exists.
[24:45.640 --> 24:46.360]  It looks like this.
[24:46.500 --> 24:47.980]  Uh, it's pretty sick, right?
[24:48.120 --> 24:53.540]  Like the uh, uh, when it flew, it actually had like the fire inside, which is even cooler.
[24:53.740 --> 24:55.540]  Uh, and this thing actually took flight.
[24:55.780 --> 25:06.640]  Um, it was incredibly inefficient and, uh, in its own way at that end, but, uh, but a glorious one at that, because it had two or the two of the three components there, right?
[25:06.700 --> 25:07.340]  It had the compressor.
[25:07.560 --> 25:11.840]  It had the ignition on it, that the, the, the turbine, the, uh, it didn't have the turbine actually.
[25:12.020 --> 25:19.400]  No, it didn't have the turbine, but, uh, the main compression happens through, um, through the piston engine.
[25:19.660 --> 25:22.140]  So this wasn't the only one that existed.
[25:22.540 --> 25:25.200]  Uh, the Russians also had this idea.
[25:25.740 --> 25:29.700]  Uh, this plane sometimes gets, uh, depicted without the propeller.
[25:29.920 --> 25:38.640]  So, you know, depending on whether you want to use that, that engine to drive only the compressor that then creates the jet that you ejected the back, or if you also want to, um, use an airscrew.
[25:39.180 --> 25:41.460]  Um, okay.
[25:41.880 --> 25:44.060]  So, this is dead end.
[25:44.180 --> 25:45.080]  This is not going anywhere.
[25:45.280 --> 25:46.200]  Like, uh, this was tried.
[25:46.460 --> 25:49.660]  Like, the specific power of this was, was, was not good.
[25:49.780 --> 25:51.000]  So, let's go back to this.
[25:51.080 --> 25:51.800]  Here's another idea.
[25:51.940 --> 26:00.940]  Why don't, instead of, like, um, try to improve or to use the, the piston engine, why don't we, like, try and imitate it?
[26:01.040 --> 26:05.980]  And we just take, like, this idea of, like, um, little explosions, right?
[26:06.480 --> 26:08.340]  Um, that's called a pulse jet.
[26:08.780 --> 26:20.620]  And so, the idea is, this is a very, very simple type of engine where air comes in and you have, like, some kind of flange that creates, like, a sealed area.
[26:20.900 --> 26:22.820]  Um, and so, you then ignite it.
[26:22.940 --> 26:26.220]  Uh, you let, you let the gases exhaust through the back.
[26:26.860 --> 26:31.440]  That creates a vacuum that opens the intake and the cycle begins again, right?
[26:31.720 --> 26:40.820]  Um, this sounds like it shouldn't work, but somehow it famously did work, uh, much to the detriment of a lot of people.
[26:41.060 --> 26:45.820]  Uh, this is a, a V1 flying bomb from, uh, uh, from World War II.
[26:46.840 --> 26:56.020]  Uh, however, no real pulse jet airplane ever, um, ever came to production because also this was extremely inefficient.
[26:56.020 --> 26:58.060]  And so, we come to this guy.
[26:58.320 --> 27:07.800]  Uh, this is a report from, I think it's 1928 or something like that, um, by, uh, Edgar, Edgar Buckingham.
[27:08.200 --> 27:20.840]  Uh, this was, uh, um, commissioned by the government and it concluded that propulsion by the reaction of a simple jet cannot compete in any respect to the air screw propulsion at such flying speeds that are now in prospect.
[27:22.720 --> 27:26.000]  I think it was like, this was like 28, 1920, something like that.
[27:26.500 --> 27:28.760]  Um, so, we're done.
[27:29.480 --> 27:30.860]  No jet engine for us.
[27:31.140 --> 27:34.720]  It's, uh, it's just, this guy said it's impossible, so we should all go home.
[27:34.980 --> 27:37.360]  And this is an important lesson to bear in mind.
[27:37.460 --> 27:39.100]  We're gonna, we're gonna circle back to that later.
[27:41.020 --> 27:43.680]  Um, somebody didn't agree with that.
[27:44.980 --> 27:47.480]  Frank Whittle had, had a few things to say.
[27:47.660 --> 27:51.680]  And, uh, uh, but before we get there, so let's just like think about what we did.
[27:51.760 --> 28:00.080]  We tried to improve the piston engine by making, uh, you know, more, more, more engine, making it bigger and faster.
[28:00.420 --> 28:01.460]  Didn't really go anywhere.
[28:01.600 --> 28:02.800]  It almost converts to a jet.
[28:02.980 --> 28:04.440]  Uh, we tried to imitate it.
[28:04.560 --> 28:08.200]  We try, we tried all of those like weird schemes.
[28:08.380 --> 28:08.940]  None of that worked.
[28:09.060 --> 28:09.760]  They were very inefficient.
[28:09.940 --> 28:12.400]  So let's try, like, let's try a whole new thing, right?
[28:12.580 --> 28:19.660]  Let's try to go back to this guy and focus on, you know, remember it looked like this.
[28:19.820 --> 28:21.940]  Let's focus on the bottom half, right?
[28:22.120 --> 28:25.240]  Like remember we were saying like this thing, it really looks like a jet.
[28:25.400 --> 28:29.280]  It's just like going through this whole big clunky thing.
[28:29.500 --> 28:30.420]  Let's try and get rid of that.
[28:31.780 --> 28:34.700]  You know, it started to look a lot like this.
[28:35.700 --> 28:43.320]  Um, and there are three big ideas that, you know, we need here, like suck and squeeze bang and then blow.
[28:44.080 --> 28:52.840]  Um, the compressor is something that, uh, you know, by the early 1920s, uh, was very well understood.
[28:54.040 --> 28:56.740]  Combustion was also like decently understood.
[28:57.100 --> 29:01.660]  Um, even though, for example, you know, pulse jets never came to fruition because of combustion instability.
[29:02.060 --> 29:07.380]  Um, the turbine, however, that's more interesting story.
[29:07.600 --> 29:14.180]  So Rato right here, we talked about him earlier when he invented for us the supercharger, the turbo supercharger.
[29:14.640 --> 29:22.340]  Um, he also, uh, did a lot of work in, uh, um, in not only the realm of compressors, but also in the realm of turbines.
[29:22.600 --> 29:29.780]  So if you know anything about turbines, uh, you certainly know what this is, right?
[29:29.940 --> 29:32.000]  This is a, this is a water turbine.
[29:32.240 --> 29:34.740]  Uh, this has been around for a really long time.
[29:35.660 --> 29:38.800]  And this is like a great example of an engine.
[29:39.280 --> 29:44.180]  Uh, and we, we like everything is sort of rooted in, in this.
[29:44.300 --> 29:51.080]  Uh, but by the turn of the century, uh, really like the main way to generate power was the steam turbine.
[29:51.740 --> 29:57.660]  And this was also a pretty decently well understood, uh, system.
[29:58.000 --> 30:02.860]  Um, and it, it achieved like pretty significant degrees of, uh, of efficiency.
[30:03.520 --> 30:08.420]  Uh, however, this was kind of a new thing.
[30:08.780 --> 30:14.120]  This is like, after you power your turbine with, uh, with steam, what can you power it with?
[30:14.200 --> 30:17.700]  The big idea is to, you power it with gas, you power it with combustion, right?
[30:17.880 --> 30:22.480]  It's kind of like a jet engine, but you don't use the jet to like move stuff forward.
[30:22.640 --> 30:25.380]  You use that to spin a generator to generate electricity.
[30:25.640 --> 30:30.540]  Um, and the first one to ever come online actually came online in 1906.
[30:30.680 --> 30:35.020]  And it was built by, um, uh, by, by this guy.
[30:35.720 --> 30:37.900]  The problem is this like was a huge thing.
[30:38.020 --> 30:39.700]  Like you definitely cannot put this on a plane, right?
[30:39.820 --> 30:40.240]  It's pretty heavy.
[30:40.440 --> 30:44.880]  Uh, and it barely generated enough electricity to sustain itself.
[30:45.120 --> 30:47.360]  Um, sorry, enough power to sustain itself.
[30:47.700 --> 30:51.680]  And why is this relevant to the, to the, to the history of the jet engine?
[30:51.840 --> 31:06.760]  Well, it's relevant because, you know, somebody in 1921, Guillaume Maxim, had the idea of compressing air, uh, with, with a turbo, with a compressor and then using a turbine to, um, to extract that power.
[31:06.940 --> 31:10.340]  But this was never built because the materials were unavailable.
[31:10.560 --> 31:15.840]  But more importantly, uh, successive attempts to build it never worked.
[31:15.860 --> 31:19.560]  And they led to that report that said, oh, you know, this is impossible.
[31:19.860 --> 31:23.960]  And the reason is that all of those turbines were flying stalled.
[31:24.180 --> 31:39.740]  And the problem is we didn't have an, an, um, um, aerodynamic model of the turbine until the mid 20s, mid to late 20s, uh, by this guy, Arnold Griffith, uh, who wrote an aerodynamic theory of turbine design.
[31:39.960 --> 31:46.860]  And this is the seminal pivotal point that allowed Frank Whittle to invent the jet engine.
[31:47.000 --> 31:49.200]  And, you know, from, okay, I should caveat that.
[31:49.700 --> 31:52.460]  Uh, but, so this is Frank Whittle.
[31:52.760 --> 31:59.460]  He is the guy who we usually, especially on this side of the, of World War II, uh, we credit for inventing the jet engine.
[31:59.620 --> 32:03.860]  Um, and the first one, you know, the first design, this was actually never built, looked like this.
[32:04.040 --> 32:08.720]  But, uh, his first jet engine, uh, wanted a good, like, readily put something like this.
[32:08.860 --> 32:12.520]  It's a pretty scary looking contraption, not something that could, like, readily put on the plane.
[32:12.700 --> 32:17.020]  But the second one looked something more acceptable and compact.
[32:17.460 --> 32:21.260]  And it worked by sucking in the air from, from the sides here.
[32:21.480 --> 32:34.420]  This, um, this was a double impeller, uh, kind of, kind of design, uh, a centrifugal double impeller, uh, and send that compressed air into the combustion cans and then exhaust it through, through the back.
[32:34.760 --> 32:40.280]  Uh, at this point, you know, uh, this, this should be, uh, should be pretty well understood.
[32:40.520 --> 32:42.840]  And obviously, you know, there were two sides to the war.
[32:43.000 --> 32:44.580]  There was also, like, the evil guy.
[32:45.000 --> 32:49.220]  Um, and, uh, we all know that wards are good against evil.
[32:50.060 --> 32:56.620]  Uh, and interestingly enough, Hans von Heinz's first, uh, jet engine actually didn't run on petrol.
[32:56.900 --> 33:06.120]  It ran, or diesel, or, um, uh, but it ran on, um, uh, what's called hydrogen, which was an interesting choice.
[33:06.240 --> 33:09.360]  Hydrogen is a pretty difficult, uh, propellant to work with.
[33:09.520 --> 33:12.560]  And, uh, uh, uh, there's gonna be an interesting sidebar to that.
[33:12.660 --> 33:14.840]  Like, that I was at that end and it didn't work out for him.
[33:15.080 --> 33:24.500]  Um, but he iterated on this, and the first engine that actually made it on a plane, um, was the Henkel S3.
[33:24.900 --> 33:27.320]  Uh, and it looked like a lot like Whittles, right?
[33:27.320 --> 33:34.520]  They both had a centrifugal, uh, impeller, and, uh, um, you know, exhausted in the air through the back, single-stage combustion.
[33:34.820 --> 33:35.760]  Pretty simple thing.
[33:36.060 --> 33:38.840]  Um, and it looks something like this, pretty cool.
[33:39.200 --> 33:43.820]  Um, and so the first time that he flew, he flew on the Henkel 178, 1939.
[33:44.200 --> 33:49.840]  That's important to remember that when World War II started, Germany already had a flying jet.
[33:51.540 --> 33:56.200]  And, uh, however, you know, this is not, this is not that scary.
[33:56.560 --> 34:02.620]  Uh, what made the, the, the scary stuff was the, the successive evolution, the Jumo, uh, 004.
[34:02.840 --> 34:07.240]  Uh, you can see, like, it's obvious that this is, like, a pretty different contraption than this, right?
[34:07.300 --> 34:10.680]  This is, like, short and stubby, uh, and this is, like, long and slender.
[34:10.900 --> 34:13.900]  And it's long and slender because it's used, it's using an actual compressor.
[34:13.980 --> 34:19.940]  Instead of compressing the air by spinning it and accelerating it, like, sideways, uh, it accelerates it, like, forward.
[34:20.620 --> 34:25.040]  Um, and it was mounted on the Messerschmitt, uh, 262.
[34:25.940 --> 34:26.940]  Pretty mean-looking airplane.
[34:26.940 --> 34:34.640]  Um, and there is a little bit of a story about, you know, if Germany had this thing, why didn't Germany win the war?
[34:34.860 --> 34:36.780]  Well, it's a little more complicated than that.
[34:36.900 --> 34:38.220]  I hope we all understand that.
[34:38.420 --> 34:52.900]  Um, but there are a couple of reasons why, uh, this didn't actually reach the level of, uh, uh, of production and, uh, um, reliability that, um, you know, could have made, could have made a difference for Germany.
[34:53.480 --> 35:06.040]  Um, one of them... Hitler cited that these, like, the jet engines were meant for bombers, um, instead of, like, for, for fighters.
[35:06.860 --> 35:08.360]  Um, weird choice.
[35:08.740 --> 35:13.860]  Um, but more importantly, these engines were not nearly as reliable as the British equivalent.
[35:14.080 --> 35:14.240]  Why?
[35:14.540 --> 35:24.640]  Because Germany, because of the wartime economy, did not have access to these guys, which were really important to make the, the blades inside, uh, inside of the turbine.
[35:25.220 --> 35:25.640]  Why?
[35:25.920 --> 35:31.520]  Because this blade, like, the, the combustion generates gases at, like, six, seven, eight hundred Celsius.
[35:32.020 --> 35:41.760]  And there was a time, especially in the, up to the 20s and 30s, when it wasn't even thought that materials could exist that could withstand these, these temperatures.
[35:42.260 --> 35:45.840]  Um, but, never mind that, we did it.
[35:46.040 --> 35:47.520]  We invented the jet engine.
[35:47.720 --> 35:49.760]  We went through a couple of dead ends.
[35:49.980 --> 36:00.640]  We, you know, attached some very weird contraptions to, um, uh, some combustion engines, but, uh, some pistons engines, but, uh, we, we're there.
[36:00.820 --> 36:01.300]  We did it.
[36:02.680 --> 36:04.360]  It's not the end of the story, though.
[36:04.540 --> 36:06.100]  Because let me ask you something else.
[36:06.300 --> 36:08.740]  So, this is a B58 Hustler.
[36:09.180 --> 36:11.680]  Um, I'm just putting it there because it looks so cool.
[36:11.680 --> 36:15.840]  Um, what's the difference, like, between this?
[36:16.100 --> 36:18.780]  So, this is, like, an engine of the time, but, like, we can take this too.
[36:18.940 --> 36:21.400]  What is the difference between these engines and these engines?
[36:23.640 --> 36:24.080]  Okay.
[36:24.280 --> 36:24.440]  Wow.
[36:24.600 --> 36:25.840]  Everybody knows everything here.
[36:26.340 --> 36:27.140]  Um, yeah.
[36:27.380 --> 36:30.200]  So, these are a lot chunkier, right?
[36:30.340 --> 36:38.220]  One of my favorite facts is that, uh, the diameter of G19 or 777X is as large, if not larger, than the fuselage of 737.
[36:39.180 --> 36:41.200]  Um, and what, what does that mean?
[36:41.520 --> 36:44.740]  Well, the thing is, first of all, this image goes so hard.
[36:45.260 --> 36:58.400]  Uh, second of all, like, at the turn of, uh, um, of 1950s, uh, of 1950, after the war, war was won, um, there was still an understanding that, you know, like, the piston engine had a lot going for it.
[36:58.400 --> 37:06.880]  At this point, they were extremely powerful, had, like, great fuel, uh, and, um, uh, specific fuel consumption and, uh, uh, efficiency.
[37:07.700 --> 37:11.540]  And they were very well understood, albeit they were maybe a little bit complex.
[37:11.880 --> 37:15.940]  Um, and they were, they worked really well, for example, at low altitudes.
[37:16.060 --> 37:28.400]  And so, for, um, big military applications, for example, it was thought that, you know, the jet would work very well at high altitudes, uh, and the, the piston engine would work well at low altitudes.
[37:28.560 --> 37:32.960]  So, you know, it wasn't like a, uh, a slam dunk victory of the jet.
[37:33.160 --> 37:39.660]  Um, whereas today, most of the, the planes that you fly on, they're jets.
[37:40.280 --> 37:46.320]  Um, and so, the difference is bypass, somebody, more, more than somebody said it.
[37:46.780 --> 37:59.620]  Uh, the thing is, the turbojet in itself was almost kind of a dead end, in the sense that, the fuel efficiency of a, um, of a, of a turbojet only really makes sense for the military.
[37:59.880 --> 38:02.500]  Um, and, or, and for, and for the Concorde.
[38:03.040 --> 38:09.140]  Um, but for, um, real life commercial applications, what you want is something like this guy.
[38:09.380 --> 38:20.080]  Um, and the idea of a, uh, of a high by, high bypass turbofan is that the center core is your jet engine, but what it's really doing, it's spinning a propeller.
[38:20.080 --> 38:21.580]  We're back to square one, right?
[38:21.720 --> 38:23.840]  Like, we're, we're, we're back to the air screw.
[38:24.100 --> 38:26.260]  The only difference is the propeller is ducted.
[38:26.560 --> 38:31.660]  That, like, gives it, like, some nice properties around, like, limiting the, the tip of vortices and whatnot.
[38:31.760 --> 38:36.220]  But, um, you know, we're, uh, we're recycling old ideas.
[38:36.220 --> 38:43.320]  And that's what's interesting here is that these are ideas that come back and then return and, like, re-implemented in, um, in different ways.
[38:43.580 --> 38:44.620]  All right, let's do another one.
[38:45.540 --> 38:47.360]  Uh, who knows what this is?
[38:49.700 --> 38:50.180]  No?
[38:52.060 --> 38:52.760]  Come on.
[38:54.460 --> 38:57.160]  No, uh, this is a CL 400.
[38:57.840 --> 39:01.600]  And this is, uh, was part of something called Project Sumpton.
[39:02.380 --> 39:04.960]  Uh, this was a project that the U.S.
[39:05.020 --> 39:10.140]  Air Force, at the time SAC, started in the, uh, I think late, mid fifties.
[39:10.360 --> 39:20.700]  Um, and it was essentially, um, the idea was to build a high altitude reconnaissance fighter, uh, reconnaissance airplane.
[39:20.920 --> 39:23.560]  And if that sounds familiar, yes, please bear with me.
[39:23.740 --> 39:32.220]  Um, this airplane was, um, supposed to fly at Mach 2 or 3, really high up in the atmosphere where there isn't a lot of air.
[39:32.500 --> 39:35.020]  Um, and it was supposed to fly on hydrogen.
[39:35.220 --> 39:43.680]  And so, um, a, uh, request went out to Pratt & Whitney to design an engine to power this thing.
[39:44.000 --> 39:46.820]  And they came up with this.
[39:46.940 --> 39:48.760]  This is the Pratt & Whitney 304.
[39:48.960 --> 39:50.380]  This engine was actually built.
[39:50.480 --> 39:51.900]  It never flew, but it was actually built.
[39:52.060 --> 39:56.320]  And it was, um, uh, hydrogen powered.
[39:56.720 --> 39:58.480]  It's a pretty standard jet.
[39:58.720 --> 40:01.380]  It only has two things that are sort of interesting.
[40:01.760 --> 40:09.620]  One is that pump over here, pulls in liquid hydrogen and sends it down to a very big heat exchanger.
[40:09.700 --> 40:21.520]  The heat exchanger, uh, vaporizes the hydrogen, which expands, uh, and then, you know, accelerates, gets into the turbine, accelerates further as it's, uh, uh, ignited.
[40:21.660 --> 40:24.560]  And, you know, we have our, um, our old jet going.
[40:24.560 --> 40:28.200]  So, um, the heat exchanger looked something like this.
[40:28.540 --> 40:30.220]  And I did the math.
[40:30.400 --> 40:39.400]  I think, like, per unit time, I think, like, per minute, this exchanged as much heat as, like, would be necessary to heat up 700 houses.
[40:39.400 --> 40:40.760]  Something ridiculous like this.
[40:41.060 --> 40:42.500]  Uh, I mean, it was, it was huge.
[40:43.060 --> 40:47.860]  So this was the, the engine that this was built and it was tested in West Palm Beach, Florida.
[40:48.320 --> 40:50.360]  Um, but then, yeah, okay.
[40:50.580 --> 40:52.200]  So, but then this, like, never came to be.
[40:52.300 --> 41:02.180]  Kelly Johnson realized that, uh, hydrogen propulsion was never gonna work because of the low, um, you know, hydrogen has high power density, but low absolute density.
[41:02.500 --> 41:03.880]  And also, it's cryogenic.
[41:03.880 --> 41:04.540]  It's a mess.
[41:04.760 --> 41:07.580]  Uh, so, you know, for, for the same reason, it's hard on rockets.
[41:07.580 --> 41:09.280]  It was even harder on a plane.
[41:09.700 --> 41:12.400]  Um, and so project Santan was canceled.
[41:12.780 --> 41:16.340]  And I think project, project Archangel, uh, took its place.
[41:16.860 --> 41:21.780]  And, uh, project Archangel, initial letter A, there were 12 iterations of these.
[41:22.040 --> 41:30.920]  And A, a number 12 was this guy, the A12, the grand, the father or the brother, um, of the SR-71.
[41:31.920 --> 41:52.720]  Uh, and so while, you know, the hydrogen powered jet engine that was initially invented by, uh, von Hein wasn't, you know, a working alternative then, and it wasn't a working alternative even in the 50s with, uh, the budget of the U.S. military, um, not all was lost because this particular dead end actually gave us something else that's great.
[41:55.100 --> 41:56.180]  See that little pump over there?
[41:56.640 --> 41:58.440]  That was developed by Pratt & Whitney.
[41:58.680 --> 42:11.180]  Um, and it went on to become the foundational pump that powered the RL10, uh, engine, which to this day is the OG Stage 2, um, engine.
[42:11.360 --> 42:14.140]  Like, they're still, they're still launching this thing on the, on the center.
[42:14.920 --> 42:17.820]  And, uh, so, you know, you have a dead end somewhere.
[42:18.020 --> 42:20.980]  You get, you get something good, um, on the other side.
[42:21.100 --> 42:25.760]  So, all right, we've gone through a lot of stuff.
[42:25.980 --> 42:27.720]  And I just want to bring it back a little.
[42:27.940 --> 42:34.380]  So, uh, a lot of things had to come together for the jet engine to become a reality.
[42:34.640 --> 42:50.200]  The idea of jet propulsion, the, the, a working compressor, the power generating gas turbine, one that, you know, didn't stall, the whole notion and construction of, uh, aerodynamic theory around it, uh, the materials, the metallurgy, uh, and even, you know,
[42:50.440 --> 42:54.340]  the war economics that, that drove the development of some, of some of these technologies.
[42:55.220 --> 43:03.980]  And the reason why this is important is that, to me, at least, no one idea mattered.
[43:04.320 --> 43:06.600]  They all mattered at different points in time.
[43:06.780 --> 43:08.380]  They all mattered in different ways.
[43:08.720 --> 43:12.580]  But, um, ideas alone weren't quite cutting it.
[43:12.700 --> 43:22.200]  The intuitions of, that were underpinning the jet engine were available decades before the jet engine came to fruition.
[43:22.920 --> 43:26.220]  And yet, you know, this didn't accelerate things one bit.
[43:26.560 --> 43:37.940]  Um, and I decided to call this talk, uh, Flights of Fancy, after I found this article, um, from, I think this was like 43, 44, um, jet propulsion from fancy to fact.
[43:37.940 --> 43:52.580]  And it had, like, this, uh, this blurb that, uh, that talked about how, um, you know, it's, uh, other, regarded as, uh, one of the newfangled ideas, uh, and people think that it's very futuristic and, uh, it's not gonna work.
[43:52.780 --> 44:03.920]  I think, um, what, what I find interesting, I guess, like, the point here is that, um, if you asked, well, first of all, this kind of critiques never matter.
[44:04.300 --> 44:09.180]  Uh, but there was no way of knowing what was gonna work out.
[44:09.860 --> 44:20.680]  And if you had asked Whittle in, uh, you know, 19, 1910, uh, if he had an idea for a jet propulsion, uh, power plant, he probably would have said yes.
[44:20.820 --> 44:27.500]  But, you know, the, the, the, uh, conditions around him weren't, uh, weren't quite ready.
[44:27.680 --> 44:39.380]  And if I had asked you, like I did today, uh, to invent, invented the jet engine in 1903, 1910, sorry, 1909, um, you would have not done any better than the people who did it.
[44:39.600 --> 44:44.220]  And the reason that matters is that ideas don't matter.
[44:44.580 --> 44:45.860]  Only execution does.
[44:46.420 --> 44:54.760]  And the reason we have the jet engine is because we had all of these ideas compete and all of these people build them at different points in time.
[44:55.420 --> 45:06.620]  And as technologists, as, uh, inventors and hackers, the only thing that we can do is continue building.
[45:07.120 --> 45:10.960]  Thinking about ideas and not following up has no merit.
[45:11.140 --> 45:18.080]  Because if in 1903, you knew exactly what was gonna happen with the history of the engine, you would still not be able to build it yourself.
[45:18.080 --> 45:26.700]  Because much like with computation, some of the things that really matter, you can only find a result about if you go through the motions of doing it.
[45:27.040 --> 45:43.360]  And so, if there is something that this tells me, is that for us, for the self-selecting group of nerds that care about this stuff, for us that are, we are, again, hackers, inventors, people interested in technology, the only thing that matters is to continue building,
[45:43.600 --> 45:47.440]  and to remind ourselves that, you know, the course of technology never ran smooth.
[45:48.960 --> 45:49.500]  Thank you.
[45:57.900 --> 45:59.620]  All right, we got three minutes.
[46:00.700 --> 46:01.440]  Who has questions?
[46:01.580 --> 46:01.740]  Go ahead.
[46:02.020 --> 46:07.740]  Yeah, if you, uh, if you have a new technology you're trying to develop, there could be many, many different ways to do it.
[46:07.960 --> 46:13.500]  You're a manager, you've got to figure out where to put the chips on, uh, weird, weird, trying things.
[46:13.620 --> 46:14.720]  There's many different ways to go.
[46:14.940 --> 46:16.440]  What advice would you give?
[46:16.900 --> 46:18.640]  Well, what are the lessons learned here?
[46:18.840 --> 46:20.180]  Like, do you try everything?
[46:20.460 --> 46:22.860]  Do you try some things that work in making good models?
[46:23.820 --> 46:25.080]  What do you recommend?
[46:25.220 --> 46:25.920]  What are the lessons learned?
[46:26.100 --> 46:27.020]  That's a great question.
[46:27.280 --> 46:38.340]  Uh, so the question was, as a, uh, you know, somebody who is, uh, uh, in the business of creating technology, when you are faced with the problem of deciding where you put the resources, how do you do it?
[46:38.420 --> 46:39.320]  Do you go wide?
[46:39.620 --> 46:40.420]  Do you go narrow?
[46:40.900 --> 46:53.160]  Um, and I think this is an especially poignant question now that, you know, we are asked to sometimes weigh in on the development of, I don't know, AI, or some of these, like, really hard to parse technologies.
[46:53.500 --> 46:56.020]  Um, I don't know that I have the answer.
[46:56.160 --> 47:01.880]  I can tell you what I do, which is, like, I choose my bets and, like, sort of, I prefer to go a little bit wide.
[47:02.180 --> 47:06.460]  Um, I don't know that there is, like, um, one answer, unfortunately.
[47:09.000 --> 47:09.480]  Go ahead.
[47:09.920 --> 47:09.960]  Yeah.
[47:10.300 --> 47:20.900]  So the question is, did I look into antiquity items and, like, things that the, the Greeks, uh, or, um, you know, before, like, this modern era did to, uh, to harness, uh, jet power?
[47:21.000 --> 47:21.460]  The answer is yes.
[47:21.920 --> 47:23.860]  Uh, there are, there are a couple of disc contraptions.
[47:24.000 --> 47:31.380]  There was this thing that was used to, uh, to barbecue stuff that used, like, the heat of the barbecue to, like, spin the, the, yeah.
[47:31.960 --> 47:39.440]  Uh, uh, obviously there is this famous, like, the rotating ball from, uh, from Greece that, uh, you fill it with water.
[47:39.580 --> 47:40.300]  It has two nozzles.
[47:40.700 --> 47:42.660]  Uh, those things did nothing.
[47:42.880 --> 47:44.220]  They, they didn't have the right idea.
[47:44.320 --> 47:52.900]  Like, it, it, it was so, there were so many other things that were missing around it, uh, that to me there was almost no point, right?
[47:53.040 --> 47:57.000]  It's a, um, actually, that, that's a great question, because it, it's exactly the point.
[47:57.300 --> 48:04.800]  If, um, even if you had the right idea, the right idea in isolation without everything else around it didn't really matter.
[48:05.780 --> 48:06.360]  Go ahead.
[48:07.980 --> 48:09.520]  Am I familiar with a prop fan?
[48:09.640 --> 48:10.160]  Yes, I am.
[48:13.040 --> 48:16.760]  The prop fan is an interesting contraption because it, it fits really well.
[48:16.900 --> 48:21.420]  I also almost thought about it including it because that's kind of a dead end and it, it sort of keeps coming back.
[48:21.560 --> 48:28.680]  The prop fan is basically like a jet engine with a propeller outside, but like at the back and kind of like really swirled.
[48:29.260 --> 48:37.220]  Um, it made a, like, it was like big in the late seventies with the oil crisis when they were trying to make like more efficient jet engines.
[48:37.440 --> 48:41.000]  Um, I, I mean, it, it looks cool.
[48:41.240 --> 48:45.060]  Uh, I, I, I don't know that it will be really successful.
[48:45.060 --> 48:45.760]  I hope so.
[48:45.900 --> 48:46.660]  Like, it looks cool.
[48:46.840 --> 48:58.200]  But, uh, the, the, the value proposition seems weird to me, but we never know, you know, I have a specific question about some of the diagrams.
[48:58.420 --> 48:58.620]  Yeah.
[48:59.480 --> 49:01.420]  A cooler after the initial compression.
[49:02.020 --> 49:02.220]  Yes.
[49:02.400 --> 49:04.340]  Why did they cool the air immediately after compressing it?
[49:04.480 --> 49:05.220]  Doesn't that lose energy?
[49:05.660 --> 49:06.360]  Uh, no.
[49:06.480 --> 49:08.680]  Cause after you compress compressing air, it heats it up.
[49:08.780 --> 49:13.100]  And if you heat it up, the hair, the air is going to be like less like thick.
[49:13.260 --> 49:16.880]  So if you cool it down, you can have like more molecules of air per unit volume.
[49:19.420 --> 49:19.860]  All right.
[49:19.920 --> 49:20.560]  I think that's a wrap.
[49:20.680 --> 49:21.320]  Ooh, look at that.
[49:21.420 --> 49:21.940]  Right on time.
[49:23.000 --> 49:23.580]  Thank you guys.