 So let us see what was done in the first world war using airships. So this is the map again, now we will use the same map because not many changes took place. The changes took place actually after second world war. So we will continue to use the same map till that time just for the ease. But the difference is that now the Russian Empire has become Soviet Russia. So that will be the only change that we will see. So the first people to use airships for war again in the world war I were the Italians. They used it against Turkey. Then we heard about bombings of London by the Germans. In fact there was a unanimous feeling that the best bombers of a city would be airships because they could fly very slowly, they could carry large payloads. They could, flying slowly is useful for precision bombing. Getting there is difficult but once you get there, ability to fly slowly is very good because it improves the precision during bombing. So they were also used for scouting, looking around where the enemy has built all its important things, let us say fuel reserves or strategic factories etc. So and also for tactical bombing that is go there and drop bomb wherever and wherever you see the need and necessity without any great planning or great target in mind. However there was a serious problem. Many many airships were shot down because by this time some military aircraft also came into being and most airships were using hydrogen. So all you need to do is there is a huge target in front of you, you have to aim and hit some igniting system onto the envelope and that is it, it will burn itself. So many airships were lost by the Germans and the British to fire from the enemy aircraft. So therefore it was decided that we should not use airships for offensive purposes like this. Before this technology could be developed, so what was done is airships were flown and they were supported in their flight by the aircraft. So there would be one big airship with armament and there would be many many small military aircraft supporting it. They will not allow the enemy aircraft to come near the airship. So you have a big group going, then you could use airships. But if by chance you are supporting aircraft are not able to handle and one fellow sneaks through and does some damage, boom, then it is gone. So therefore many people said that you know it is not worthwhile to use airships. But so much was the terror in London because of the bombing of the city by the Germans that there were ads like this which said you know you can see some burning airships during combat. So it is far better to face bullets than to be killed at home by a bomb. And this bomb is from the Zeppelin, there are many air raids and airships then began its applicability was mostly limited to escorting ships. So you can see there is a ship below which is being escorted by an airship and it will be used to give early warning to the ship about any impeding attack. You can use them as offensive weapon also for damaging ships because a ship is actually completely defenseless when it is floating in the water. Against an airship it has no chance of being protected. So you can use it for protection as well as you can use it for offense. And interestingly some people came up with brilliant idea of having aircraft mounted on airships. So you attach small aircraft on airships and you fly in the ocean and to protect a ship and if you see some enemy aircraft coming you can launch the aircraft from the airship. It would go and bomb the aircraft and then maybe land somewhere because docking onto the airship was very difficult. People attempted it but they said it is very difficult to dock back to the airship. But one can take off with the aircraft attached to the airship and then release it and launch it. So this is the other thing which I want you to search and put on the model page. What was the technology available for docking of aircraft onto airships? And what kind of technical challenges were faced in docking and you know reattachment of was it possible for example for an aircraft to come and attach itself back to the airship? Were there any instances of that type? I am not very familiar myself about this. What I know is and I have seen pictures of aircraft which have been attached to the airship and then it goes for an offensive mission. So British started using beams for anti-submarine warfare and coast patrol. And today we are recommending airships for anti-submarine warfare because of the extreme high endurance which is needed when you want to locate submarines. Then do not forget that the aircraft technology is also picking up in the meantime. From 1993 it is now 15 years since the aircraft has come into being. So for strategic bombing airships were found to be absolutely useless therefore the plane has replaced it and from this point onwards you will not find in history much use of airships as strategic bombers or even bombers. So the offensive role of airships was taken away by aircraft because of much higher manoeuvrability as well as much higher safety that you have in operating aircraft. Even an offensive environment, okay world war is over there is a treaty signed in Versailles. So after that airships are being used only for civilian purposes because the war is over. So the US now realize the importance of airships because they saw the damage caused by the Germans to the British and the Allied forces. So they said let us start building this technology in our country. So they started the extensive airship construction program and what they simply did was what we normally do when we start something is you look at an existing design and you simply copy it, okay. There is nothing wrong in that. You may not be able to improve it but at least you will be able to do it and if someone denies you the technology the only option you have is to first make something similar or same and then you can go for improvements and you can go for enhancements. So this is a very beautiful picture which shows an airship called USS Acron in Lower Manhattan, okay, sorry Upper Manhattan not Lower Manhattan, it is an Upper Manhattan. And then the big names in airship technology are the Zeppelins. We had the LZ1 and LZ2 earlier and there are few more of them. LZ is an airship which was named in honor of its inventor and that airship was actually LZ127, so 127th airship LZ127 that was designed in 1925 and it was operated from 1928 to 1937. So close to 9 years it flew till it met a disastrous end but notice that in these 9 years it has done safely no incident, no accident around 600 flights and it has covered 1.6 million kilometers or more. Interestingly it needed a crew of 40 people, 36 officers and 4 supporters for a crew of only for a passenger capacity of only 20, so very very large on manpower requirements. And what do you think was the main job of these 40 people, why do we need 40 people, why should an airship need 40 people to operate, what are they doing, they are not serving food on board or drinks on board, controlling the, no no no that there is only pilot co-pilot, maybe one more person for navigation. So most of these people are on the ground, they are not in the air, these are the ground handling people. So when this airship comes into land it is a buoyant vehicle, the tendency of it will be to bubble as the wind hits it. So they are there to hold it on the ground, so and that is even today one of the serious limitations of airships that the ground handling staff needed in a conventional airship is very large compared to an aircraft. So now we see that the maximum speed has increased from 17 miles per hour to 80 miles per hour. We have 5 IC engines generating around 550 horsepower each and we have the length as 236 meters now. So from 420 feet it has become 776 feet, much larger almost double in size, almost double in size but it can lift 60,000 kilograms. Now this kilogram is not payload, it is the net lifting force available or the gross lifting force available and if you subtract from this the weight of the self only then you get the payload which was 20 passengers and maybe whatever the cargo that they carry. So here is a very beautiful picture of this airship flying in Rio de Janeiro. For those of you who know about Rio this is a very beautiful place called as Sugar Loaf Mountain and this is the Copacabana beach. So it is a very beautiful place, I have been there recently so when I saw this picture I could not resist putting it here just for my own memories. And then when I went to Rio I actually met an airship expert who said even recently also we have had airship flying over Rio not 1930s, not even born at that time. He did a PhD, he is the first, I mean he is the first PhD in recent times to work on airships and his name is Sergio Gomez and right now he is an investment banker. He works for a bank in Brazil but his work is mostly to do with looking at the merits technical evaluation of various projects. So he did his PhD from Cranfield University in 1960 in which he did wind tunnel testing and the first flood dynamics model of airships in modern times. Many people say that Sergio was in a time when the airship technology was being revived. This is Graz Zappelin, the airship about which we spoke. So notice that such a large airship but people sit only in this portion, this is the gondola. So let us see if we can get some idea about this particular airship. So this is some historical video showing you the aerial view shot from an aircraft or another airship I do not know of the Graz Zappelin flying. Now this airship is flying in Sipol in Amsterdam or it is coming in at Amsterdam Sipol Airport for landing. You can see a small plane on the left side. I think that was one of the sources of the aerial video. It is a very old historical video. You can see at 1120 people are waiting excitedly for this airship to come and land. They fly very gracefully. So they have dropped some parcel. This is mail postage which has been dropped by the airship and then this is being carried into the postal van on the ground. You can look at the fashion of that time, the kind of beautiful dresses ladies are wearing. All of them are wearing actually gown type dresses. There is no audio in this clip. It just has aerial video shot of the air, there you see a parachute has been launched and that parachute was carrying the mail. Did you observe that? There was a parachute which was dropped with the mail. So when you want to drop mail at a particular city you drop it with a small parachute. So it is windy. You can see the flag is fluttering. It is very windy but still the vehicle is magically making its maneuver to approach for perhaps to approach for landing at an airport. Okay, we have many, many more videos to see so probably I will just save some time.