Aero Basics- 1
My vacs of third year have started and I have got finally selected to work for an NGO called nirmaan for their grassroot technology group called Parishodh.
With finally some free time for "myself" this time,I would like to continue my aspiration to learn about flight and making a micro-air vehicle.
Got my book "Flight without formula" given by my dear brother ,was lying with dust around in my hostel shelf though and I started reading it since yesterday.
Well,I like mechanics and this book has whole lot of it ,though not mathematically but it does have numbers to relatively compare stuff(but in british metric system :( ).
So reading a few pages I would like to summarize a few important philosophies(as Sheron Sir calls) which I came across.
The most important of these is the Archimedes principle which says a lot in a few words:
Philosophy 1
It states
" A body when partially or fully immersed in a fluid,experiences a upthrust equal to the weight of the fluid displaced by the body".
The author (A.C.Kermode Sir) ,in his lucid language ,explained this in context of airships aka balloon ship carrying passengers.He classifies this "vehicle" in lighter than air category.
Philosophy 2
A body will float in a fluid if the upthrust is > weight of the body
Note:
Now the upthrust ,since it depends on the weight of the fluid,will thus depend on its density.
Consider the case in which a ship is in fresh water and in salt water.
The density of slat water > the density of fresh water
Thus to get the upthrust required to balance the weight of the ship,the ship will have to displace more water when in fresh water than in salt water.
So a ship will be floating higher in salt water than in fresh water :)
Philosophy 3
The density of air is not constant with altitude.It keeps of decreasing as we go high up away from the ground.
So what ?
Well it causes two difficulties:
1.(For airships) As we go higher we will have to displace more air to get the same lift.Thus the ballon will have to be inflated(which is not done) rather we will have to let off some weight from the ship.
2.The airships do have a propulsion system.And this is mostly of internal combustion engine type.And we know that it requires air for combustion which is very rare at higher altitudes.Thus either we need to carry cylinders of air or very need to restrict ourselves at lower altitudes.
Philosophy 4
The temperature of the atmosphere keeps on decreasing as we go higher and higher.
Infact it decreases linearly with altitude upto some point and after that it becomes pretty much constant at around (-57 degree C).This changing temperature gradient is what is infact used to classify various layers of the atmosphere.The layer upto which the tempearture varies linearly is called "Troposphere" and in which the temperature remains constant is called "Stratosphere".The line(rather thin layer) dividing the two is called "Tropopause".Though the classification is not much relevant here but we will try to maintain our flight mostly in the troposphere only as at lower temperatures mostly the engine and also the pilot will have to be provided with proper heating arrangement.
There are some other issues too with airships like how to descend them and safety issues..That is done basically by deflating them.We will now stop discussion of airships and start with aeroplanes- The ones which have a wing and classify into "heavier than air flying objects".
Philosophy 5
Hold a piece of cardboard inclined to the horizontal in your hands.The edge which is held higher is called the leading edge and the lower one is called the trailing edge.If we move this board forward,it will experience two forces by the air.One upward,trying to lift it and the other one backward trying to pull it back.With the resultant of two forces inclined to the board.Well the former one is called "LIFT" and the latter one "DRAG".If we wish to keep of getting lift and counteract drag we will have to keep the board moving ,and for this we require a forward force of the plane called "THRUST".
Thus the three main forces associated with the aero dynamics are :
1.LIFT
2.DRAG
3.THRUST
With finally some free time for "myself" this time,I would like to continue my aspiration to learn about flight and making a micro-air vehicle.
Got my book "Flight without formula" given by my dear brother ,was lying with dust around in my hostel shelf though and I started reading it since yesterday.
Well,I like mechanics and this book has whole lot of it ,though not mathematically but it does have numbers to relatively compare stuff(but in british metric system :( ).
So reading a few pages I would like to summarize a few important philosophies(as Sheron Sir calls) which I came across.
The most important of these is the Archimedes principle which says a lot in a few words:
Philosophy 1
It states
" A body when partially or fully immersed in a fluid,experiences a upthrust equal to the weight of the fluid displaced by the body".
The author (A.C.Kermode Sir) ,in his lucid language ,explained this in context of airships aka balloon ship carrying passengers.He classifies this "vehicle" in lighter than air category.
Philosophy 2
A body will float in a fluid if the upthrust is > weight of the body
Note:
Now the upthrust ,since it depends on the weight of the fluid,will thus depend on its density.
Consider the case in which a ship is in fresh water and in salt water.
The density of slat water > the density of fresh water
Thus to get the upthrust required to balance the weight of the ship,the ship will have to displace more water when in fresh water than in salt water.
So a ship will be floating higher in salt water than in fresh water :)
Philosophy 3
The density of air is not constant with altitude.It keeps of decreasing as we go high up away from the ground.
So what ?
Well it causes two difficulties:
1.(For airships) As we go higher we will have to displace more air to get the same lift.Thus the ballon will have to be inflated(which is not done) rather we will have to let off some weight from the ship.
2.The airships do have a propulsion system.And this is mostly of internal combustion engine type.And we know that it requires air for combustion which is very rare at higher altitudes.Thus either we need to carry cylinders of air or very need to restrict ourselves at lower altitudes.
Philosophy 4
The temperature of the atmosphere keeps on decreasing as we go higher and higher.
Infact it decreases linearly with altitude upto some point and after that it becomes pretty much constant at around (-57 degree C).This changing temperature gradient is what is infact used to classify various layers of the atmosphere.The layer upto which the tempearture varies linearly is called "Troposphere" and in which the temperature remains constant is called "Stratosphere".The line(rather thin layer) dividing the two is called "Tropopause".Though the classification is not much relevant here but we will try to maintain our flight mostly in the troposphere only as at lower temperatures mostly the engine and also the pilot will have to be provided with proper heating arrangement.
There are some other issues too with airships like how to descend them and safety issues..That is done basically by deflating them.We will now stop discussion of airships and start with aeroplanes- The ones which have a wing and classify into "heavier than air flying objects".
Philosophy 5
Hold a piece of cardboard inclined to the horizontal in your hands.The edge which is held higher is called the leading edge and the lower one is called the trailing edge.If we move this board forward,it will experience two forces by the air.One upward,trying to lift it and the other one backward trying to pull it back.With the resultant of two forces inclined to the board.Well the former one is called "LIFT" and the latter one "DRAG".If we wish to keep of getting lift and counteract drag we will have to keep the board moving ,and for this we require a forward force of the plane called "THRUST".
Thus the three main forces associated with the aero dynamics are :
1.LIFT
2.DRAG
3.THRUST