 Now, there are also some other types of engines which are popular for airships. One of them is the turboprop type. The turboprop type is basically, it comes in two versions actually. One is this particular figure where we see that a turbine, in this case an axial sort of turbine having a compressor, combustion chamber and turbine. On to the compressor shaft, you attach a gearbox and that drives the propeller. So why do we need a gearbox to reduce the RPM of the propeller? At what RPM does the turbine normally move? In a gas turbine engine, what is the RPM of the turbine? Typical value. Take a guess, no it is more, around 30,000 rpm for a typical turbine. In fact for very high power turbines in commercial aircraft, you can also expect 60,000 rpm. You can. And at what RPM do you rotate the propeller of an aircraft engine? So why do not you guys have any feel for numbers? These are very simple engineering numbers. You can calculate so many things, you can do so many coding but do not you have any feel for basic numbers? No that is less, it goes to 1000, even 2000 sometimes. And small motors with which you play, they go at much higher RPM. What do you think, Amit? What RPM are your small EDFs, 54,000 rpm, correct? So small, small motors but you cannot put a proper RPM, it will break away under the excessively high centrifugal forces plus it will be inefficient, it cannot extract the energy power at that particular RPM. So from 30,000 to 2000 or 1000, you need to bring it down using a gearbox and that makes it very heavy, that brings in maintenance costs. So what is the other variety of engine that can be used? If I want to couple a turbine to a propeller, one is turboprop as shown here. Is there any other type of engine that you have heard of? So now what is happening to the exhaust here? The exhaust here is it giving you some thrust? How much percentage? Correct, 15 to 20 percent sometimes, 10 to 15 percent is a good ballpark, very good. So the exhaust of this engine is also giving you thrust. But suppose you do not need thrust, you need power, thrust is welcome because if you are giving forward force rather than getting from the propeller, you can give from the engine itself, it will give reaction but sometimes you may not need it. So have you heard of something called turbo shaft engine? In that we close the exhaust or we do not use the exhaust for giving thrust, the entire power of the turbine is absorbed by the propeller. Such engines are used on helicopters for example, turbo shaft engines. In airships also we can use turbo shaft engines but they are not normally used, normally we use turboprop engines. Now this is a constant question that gets asked or it comes to the minds of the people who design airships. Now when I say airships, I am talking about now passenger carrying airships. I am not looking of RC airships. So let us have a look at a few comparative matters between turboprop and piston prop for a passenger carrying airship. First we will go for turboprop. So it has a higher initial cost, it is more expensive to buy turboprop. Why is that compared to IC engine, it is much more costlier, correct. The fact that you have a gas turbine, cost will go up because that will have compressor, combustion chamber, turbine, high RPMs, very very careful aerodynamic design. So therefore they are costlier but they give you better power to weight ratio. They give you lesser maintenance man hours per flight hour. This is a term which is used to comment about the maintainability of an aircraft, MMH by FH. So what it means is how many hours have to be spent, man hours in maintenance per unit hour of flight. So what is your, what is your feel? Let us say take an aircraft like MiG-27 which is a you know high speed turbojet with reheat. What would be the maintenance man hours per flight hour? Yes, good good approximation around 20 to 30. That means you fly it for one hour and then 30 hours of maintenance is needed by one person or one hour by 30 people, whatever combination you like in between or 2 hours 15 people. So around 20 to 30 man hours are needed per hour of flight. What kind of number do you expect for a commercial transport aircraft which flies for let us say 16, 17, 18 hours a day, again it is around 8 to 10. So this particular number is lower for turbo prop compared to piston prop. Around 3000 hours is the time between overall for a, now when I say MMH by FH for an aircraft engine is not the only thing, engine is one part of it. There are other parts which consume time. So they will get confused between aircraft MMH by FH and the engine MMH by FH. As far as the engine is concerned, the time between overall and the time required for however maintenance is more important. So that number is lower for this one and it gives you higher speed capability. You can fly with 250 to 300 knots but it has got a higher fuel consumption. However the fuel is ATF, aviation turbine fuel which is nothing but a refined type of kerosene with some additives. This is much cheaper than the gasoline. Those of you who listened carefully to my case study on airships of Uttaranchal, we realized that the consumption of fuel was more in case of the piston props but in case of airships compared to helicopters but the cost was, I mean the, they were different because of the cost. Turbo props have lower engine cost but they have lower power to weight ratio. Higher MMH by FH, oh this is a mistake, it should be 2000 hours. I will correct this. So this is 2000 hours. Speeds never more than 200 knots to airspeed. Fuel is costlier. The fuel used is F gas or aviation gasoline which is petrol plus additives. So since kerosene is cheaper than petrol therefore the cost of ATF is generally lower than cost of F gas also availability. So that is why turbo prop may actually have high fuel consumption but they may turn out to be cheaper to use because of the lower cost of the fuel. So what is the cost of petrol today in the market? Around 64-65 rupees. What will be the cost of ATF? It will be approximately 100. Then air gas, that is basically air gas, refined petrol, kerosene. What is the cost of kerosene? The market much lower, 25-30 rupees and therefore if you use ATF it will be also relatively cheaper. But these costs are artificial I must always say because of the consumption. Okay, so the first airship to use turbo prop as its principal powering system was the Sky Ship 600. So I have to show you a small film about this airship. Maybe I have shown you this film before, do not know but let us just see. This is the launch video of the Sky Ship 600 made in flight. The world's media were out in force to witness the 600 made in flight reflecting the global interest in this multi-purpose craft. The 600 is a stretched version of the earlier Sky Ship 500 with passenger capacity doubled from 10 to 20 seats, cruising speed increased to 55 knots, airborne endurance to a remarkable 48 hours and virtually any other aspect of the craft refined and upgraded. You have all the four-generation systems. Yes, one by one. When it was fired with the running of the twin turbo-charged Porsche engines, she inspired Commander Nick Bennett was now ready for takeoff. Only a blown power-setting the 600 executed a perfect zero-roll takeoff and climbed skimply and quietly into the sky. She had entered her element and was performing to the highest expectations of the airship industry's team. The Sky Ship 600's ability to stay airborne for 48 hours gives her unique operational flexibility and the non-combustible helium lift gas has eliminated the five-hazards normally associated with hydrogen. In her civil role, the ship can be transformed into an eye-catching aerial advertisement. She can be used for emotional and pleasure flights and she provides a perfect platform for aerial photography without any of the vibration and operational problems usually associated with conventional craft. As an eye in the sky, the 600-pack fulfilled many defense roles. With slow front and parallel endurance, a large parallel volume emits a horrifying sky-ship for coastal and maritime patrol, including cushioning protection, navigation monitoring and pollution control, as well as everyone early morning, anti-submarine warfare and mine sweeping. Already defense and coast guard agencies for Britain, America and France are conducting technical evaluations on Sky Ship 600. After a million hours trying, pilot Nick Bennett makes a steep approach to the airfield, then brings the ship to a stable hover prior to landing. The vetted thrust engines allow total control and positioning of the craft and the rate of descent can be accurately adjusted to suit any pilot. This capability to take off and land vertically takes the craft unique on my airships. Gone are the days when vast tracts of runway were needed for their operation. The sky ship's evasion industries can easily take off and land on unprepared ground the size of a football pitch. Once on the ground, the ship docks quickly and easily. Secured to the mast, she is no further tethering nor restraint. The main flight have been an unqualified success. The concept has been to take a jolly good old idea of boiling flight. And then to use new materials to the best advantage in order to get the structure well down as low as possible. And this is not achievable. So the use of the new materials is enabling us to save weight. And weighting an airship is absolutely fundamental because the gas has got to lift the structure and the formula. We can get the structure well down to nothing, obviously, and more payload. That's exactly what airship industries have done. Already the sky ship 500 is in service in the United States and Japan. And after this tremendously successful maiden flight, the 600 is heading for even wider markets.