 Moving to the introduction as airship, a high altitude long endurance platform, high altitude is basically a relative term because general airship as you know at the end of this course that they are normally airships used to fly from one place to another place. But this type of system is remains a loft for a particular duration of time and serves as a platform for various purposes that is why it is called high altitude long endurance platform and it is placed around the 20, 25 kilometers. It is not actually in comparison to the other systems it is not a high because satellite we use to, satellite orbit is around may be maximum 35,000 kilometers and even at international space station is the orbit of what is the height of that orbit, anybody knows? What is the height of international space station? So, it is around 400 kilometers and so any few have seen that international space station at the sky, anybody from ground the naked eye, no. You can see because there is a link spot your station and when you will restore your mail ID they will send and also they will send to you whenever it will cross above your city like when you whenever you will enter Mumbai, whenever it will cross over the Mumbai and they will send some duration before as a lot you can see that with the direction and time and the direction of in which direction it will be visible. And especially at the night you can see at the moving light with the very high speed anyway. So, these are the systems which perform which can be used for the various purposes mainly for communications, maybe for surveillance and many other applications will be seen later stage. So, high altitude long endurance platform, long endurance basically is for because it can stay at the at that height for couple of months or 6 month may for even a year that is why it is called a high altitude long endurance platform. And it remains a standstill and serve the purpose a standstill platform and very it is very cost effective relative to the satellite because designing and launching at orbiting at sending at that height is very cost effective let through the satellite because in satellite you know how much risk is there and how much cost involved. So, it is not create it does not create a disturbance to the commercial aviation because you know at what height maximum commercial aviation takes place maximum yeah max 7, 8 kilometers whenever you will fly it you will take a flight they announced you are 35000 feet. So, it does not create any disturbance it is above that the commercial flight. And the defense or fighter jet can go above that that is a different thing. So, why question arises why it is placed only at the 20 or 25 kilometers that is why it is the answer here. So, the wind speed at that height is relatively lower below that the due to the higher wind speed. So, at a wind speed to overcome that drag because the system used to be very big and to overcome that drag you will need a bulky power systems to overcome that drag otherwise it will shift to the another location. So, you can see in the increased volume due to the larger power. So, to produce that large power to overcome that large drag you will need a large volume by large volume can anybody say. So, this system used to be driven by the solar power. So, for large area because you need a large big solar energy to place such large solar area solar cells you will need a large space. So, that the systems size will increase and if you go above that then again size will increase because the density of air will go down further. So, you can see here increased volume due to lower density and buoyancy because you have to take care of payload as well to carry that payload it will need to displace a larger volume of light density of that air. So, you will need a bigger size of air shift for the same payload at higher altitude are you getting my point. So, that is why 20, 25 or 22 kilometers is optimum. So, this is a conceptual image to demonstrate the it is in that had to serve the different purposes. And when you see in India there is a concept of placing around 20 air shifts to cover the entire nation. So, that it can serve the purpose of communication as well as surveillance. Because particularly in India it is very a problematic problem to get a seamless connectivity and you know India is at the bottom in Asian continent while we consider the speed of internet. And it is not fall under the 100 when you consider the entire world. India is beyond that because the low speed and even you move from one location to another location it will not get a seamless connectivity and even nowadays even remote location they are not a feasible 3G connection or a smooth 3G connection. The world is talking about 5G and we are struggling to get a 3G connections. That is why the problem in remote location especially and big cities it is a problem of radiation and towers used to place for better connectivity that is another problem in infrastructure. So, it can serve a very good platform to cover the nation for communication systems especially. So, what are the advantages over the satellite systems? It is self-launchable you do not need a launcher. So, do not need a rocket you can bring it down and then after refurbishing you send it to back which you cannot do in a satellite and that is a big problem actually because after expiry satellite used to be there and create a debris and space debris is a big problem nowadays. So, as you place it in a position it starts serving no global and global infrastructure required. So, these are the benefits of other satellite and the what are the various applications we can see. When you talk about defense you can use at a surveillance or guidance warning to observe border areas and for civilian maybe a communication is a big benefit from these systems. So, we will see a small video which will demonstrate the application of these systems it will be clear. So, let us see the video. It is the video of the Stratobus conceptual video.