 Now, whenever we will go to the design, the output will change according to the requirement because user will give basically in user requirement in two mode. What are the power requirements for the systems and what is the payload he used to take? So, depending upon the power requirement and payload requirement, the shape will change. If power requirement is more important or big power requirement relative to the payload, we will design airship in such a way that it gives a maximum power because profile of the airship systems, the power availability due to that same area will be different. Are you getting my point? Because the angle and orientation of the normal of the solar cells will vary with the profile and that will affect the output. So, it will depend upon what is the more important. You have to trade off between. And if you want to take up only, you have to consider only payload, then you do not have to bother about the solar systems in like in normal airship. But because, but you have to take care of the power input as well and that will drive the shape to take care these effects simultaneously. This is a big problem actually. So, while design, you have to, there are so many research going on to minimize the structural weight because a structural weight is driven by the envelope GSM. And 50% of the systems weight is due to its structure, envelope structure. So, we want to use a very low weight density of the material which can perform same strength as a big one. That is the challenge. And another challenge is it should be you know at the end of the course, you are much aware of the, it should be a UV, UV protection should be there and adhesive to manufacture that envelope, lightning protection as I said external object impact strength, something hit the airship and it should be durable, should be able to stand gas permeability and proper pressurization to maintain the envelope shape and rigidity otherwise the performance will go down to withstand with the temperature variations. These are the challenges. So, when we come to the envelope material choices, actually these are the target which will fulfill our requirement. We want very low density with a high strength material. So, envelope configuration options, different options may be there. We have to take care of the pressurization, takeoff and landing. You need a structure, infrastructure and these are the other requirements for the configuration. Station keeping in thermal consideration, we have to take care of anti-lattening measures because it will affect the systems and whenever it get damaged, then other systems another problem will arise. It is because the envelope is not a big issue. It is not so much of costly, but the systems mounted in that airship is actually a very costly. There is a major advantage over the satellite system because in satellite we do not recover our systems after its expiry, but in this system it can recover actually and envelope is not a big issue implies very cheap material whenever we can compare to the systems and as a payload which will serve our requirement. So, to handle these systems people are working and they are around the globe. You can see it starts at ATG UK, compound propulsion system to enable the airship to hold the station within 1 kilometer of cube. It is designed in such a way that it will not go beyond that cube in 3-dimension, 1 kilometer of cube accuracy is needed and to take care of that they have included in the lateral thrust to counter the prevailing stratospheric wind and other systems. That is a requirement actually otherwise it will shift to some other location and that will create a problem and it will go beyond your radar or main purpose which we want to serve that will go beyond, it will shift it will create a problem. So, thermal consideration is a big issue while designing because the temperature at the day will be higher at the night will be very low and the temperature will affect the buoyancy as well as the energy or output of the systems and because whenever temperature will be high it will try and gases will try to expand and source will not perform very accurately at the high temperature. Its efficiency will go down that is the problem. So, onboard system to because at the daytime we can give directly power to the propulsion system and to the payload system but at night we do not have any power sources. So, we have to keep we have to store that power in a daytime to so that it can serve the power requirement to the payload as well as propulsion system at night as well. So, you will need a storing systems or battery on both batteries and so regenerative fuel cells. So, regenerative fuel cells is another area so many research are going on in the systems because the efficiency is higher than the and it is better with the lithium ion battery in comparison to that. To store same energy lithium ion battery you will need a big lithium ion battery and whenever you use a regenerative fuel cell the system or the battery which will come down but it will cost more it is another area. So, these are the actually a representation of solar regenerative fuel concepts at the daytime the power available is higher and we will need a direct power real low the extra power which is 2 minus 1 is basically stored for the night time which is 3 actually in bow direction and the concept is that you electrolyze the water very simple at least in watching is you separate the hydrogen and oxygen by electrolyzing and then after combination it will create energy and it will be given to the propulsion system propulsion unit and payload systems at the night time. So, any dot in this system fine now. So, this is another pictorial representation we separate hydrogen and oxygen using the energy at the daytime and the same stored energy you can get while combining hydrogen and oxygen. So, it is a recycling of hydrogen and oxygen producing a water then adding in it will separate hydrogen and oxygen it will go on. So, for the protection of from lightning there are methods and it should be with a with a stand at that height because the stratospheric condition is the protection lightning will be there and it might affect it might damage our envelope. So, there are systems available to take care of that launch and recovery and glow handling is another big problem because the size of the such systems is very large. And to handle such systems and it is fragile you know it if you will not take care proper take care it will it kind it might damage the envelope and the recovery of such a big system is another issue and launch as well. So, these are the proposed applied orchid style launch technique for launching. So, these are the another methods by limiting the velocity. So, you can see the while launching in a rocket mode. So, it is very clear to by picture actually you know need any explanation. So, it is showing a recovery to take care of the payload systems by different method may be resting in the water directly or resting in the boat. Ground handling is a big issue actually you need a large infrastructure to handle these type of systems and in later slides we will see how big actually there is a need infrastructure to store these type of systems to handle these type of systems. And you are aware already that there used to be a mast and mooring mast and winching systems that is still get damaged. So, these are the requirements I know you I believe that you are aware of with all these systems at the end of this course. So, these are the another requirement to handle such a fragile vehicle near to ground that is obvious. So, you can see how big is the actually requirement to handle systems. And first airplane hangar you can see the height of man's available with the actually in the systems size you can compare how big is that you know as you can see the height and the height to mast.