 Hello and welcome to the overview of the NPTEL course on lighter than air systems. I am Professor Rajkumar Panth from Aerospace Engineering Department of IIT Bombay. This course is going to be of a duration of 12 weeks and the content would be approximately 1.5 hours to 2.5 hours per week. Most of the weeks the content that you will get in terms of videos would be around 1.5 hours. But I think there are 2 weeks in which the content will be slightly more and that would be the theoretical part of the course. This course has certain special features which I would like to highlight. First of all, this is a very unique course and it is a pioneering effort. I say that because there is no such course running anywhere else in the world and that is to the best of my knowledge. So, you will not be able to get any dedicated course on lighter than air systems anywhere else except here. This course is based on more than 2 decades of research experience that I have picked up at IIT Bombay and the course notes for this course were developed in 2010 under the curriculum development program of IIT Bombay. But the course could not be offered for a few years. The first delivery of this course was in 2015 and all the lectures were recorded by the Center for Distance Education and Engineering Program of IIT Bombay. Now, these are one and a half hour lectures, two lectures a week, there were approximately 20 lectures which were recorded and these lectures were then used as the course material for the subsequent deliveries of this course. But in 2018, we decided to cut these one and a half hour videos into small 10, 15, 20 minute clips so that it is easier for a student to digest the information. So, those clips are going to be used in conducting this course on NPTEL. The course consists of six capsules. The first one would cover introduction and historical perspective of LTA systems because these are systems about which information and knowledge is very, very limited. In fact, even in aerospace engineering departments, this topic is not covered because it is considered to be obsolete and outdated, but LTA systems have actually bounced back and now they are considered to be good candidates for long endurance, surveillance and aerial photography missions as well as there is a movement now to look at greener aviation in which these systems become far better compared to conventional systems. So, they are coming back in a big way and hence it is important to learn about the historical perspectives. The main parameter in any LTA system is the static lift and it is important to understand various aspects related to static lift and also how it is estimated. So, this topic comes under aerostatics. We will also look at how the static lift varies as a function of various atmospheric conditions such as the humidity of the air or the ambient temperature, ambient pressure, purity of the gas and so many other factors and it makes a big difference to the numerical value of static lift. So, we will look at all these eight or nine factors that affect and how it is calculated and there is a concept called as a pressure height which we will also study. Then we will move on to design methodologies for two of the main LTA systems, the airship and the aerostat. Next we will look at some unique operational issues related to LTA systems and finally we will touch upon some current developments in LTA systems. We will look at for example, high altitude airships or stratospheric airships and we will look at hybrid airships and other emerging technologies in this particular field. Now, you have to be very clear as to what is anticipated as an outcome from this course. So, at the end of the course you should be able to achieve the following points. One is you should be able to clearly understand the differences between a conventional heavier than air system and a lighter than air system, you should be able to estimate static lift generated by an LTA system given its type, its size and the operating scenario. This is a very important part and this part of the course is essentially more to do with formulae and calculations. The other parts are generally descriptive in nature and there is one more section where there are some formulae. Carrying out the conceptual layout and sizing of an LTA system given the customer requirements, operating requirements and maybe some regulatory requirements. You will also learn some technological challenges in the design development operation of LTA system. We have actually made a few of these systems through students and researchers, we have deployed them in the field, we have tested them, all of them will be showcased and finally you should be able to comment on the current developments and predict the future trends of LTA systems based on the learnings that you achieve in this course. So, I hope you will sign up this course after listening about the overview. Best of luck to you and hope to see you in this course. Thank you.