Welcome to Gareeb Scientist.
today we will learn why...
ISRO rockets have a big water tank on them
Have you seen this photo anytime
probably seen...
this is the PSLV 2nd stage
the blue round thing is a tank
since it,s in a toroid shape
its called toroidal tank and filled with water.
some might say this water is for when there is a fire on the pad.
nothing like that
this water is required for the Vikas Engine.
Now you might say that the job of the engine is to spit fire
what will it do with water then ?
it has a very important technical reason.
lets learn!
let me brief you on Vikas engine
Vikas engine is a derivative of the french Viking Engine
derivate might be a strong word to use here.
French agency CNES and India's ISRO...
made this Engine together.
you may call it a collaboration
french gave us the knowledge, Know-how and know-why
India in return sent skilled engineers to work and space grade transducers.
Then in India, they made the Vikas Engine.
If you want to know more ...
the scientist who named it Vikas, Sir Nambi Narayan
he has written a book
This book is actually on his story of how he was falsely accused of spying
but the book also mentions the journey on Vikas
recommended read.
link in Description
would love to meet you Nambi Sir !
before the water thing, we need to understand how the Vikas engine works.
This water tank thing is Vikas Engine Specific.
So whichever rocket stage has a Vikas Engine has this ....
basically all active ISRO rockets (GSLV/PSLV)
Now since we can see the PSLV 2nd stage bare..
that is why we can see this toroidal tank
GSLV MK2/MK3 ! it's present inside the body.
So cant be seen easily.
Vikas Engine runs on a Gas generator cycle.
let me explain you in simpler terms
Its fuel is UDMH - Unsymetrical Dimethyl Hydrazine
and oxidiser - N2O4 , Dinitrogen Tertaoxide.
these are hypergolic fuels
so when these two come in contact they burn , but they are poisonous to humans(FORGOT TO MENTION)
So Vikas Engine does not require any ignitors
So engine design is relatively simple.
Let me explain the Gas Generator Cycle in simple words.
A small Chamber where the fuel and oxidizer will mix
gas will be formed
this gas will rotate a turbine
this turbine has a common shaft attached.
pumps on either side of the shaft
one oxidizer and a fuel pump.
these 2 will pump the fuel and oxidizer into the combustion chamber
then combustion and engine working
This is basic
gas generator products are exhausted
if you see gas generator cycle engine tests you will notice this.
so this happens in Vikas engines case too
now how does water help here?
there is another small pump attached apart from the 2
which pumps water
why do we need water ?
the gas generator exhaust is very hot.
if we dont control the heat...
the turbine might melt and freeze the engine''
so engine shutdown
this reference is important for my future video.
So cooling the GG exhaust is important
So this water is used to cool the GG exhaust.
So this is how it works
this water pressure is also used to actuate Hydraulic valves
meaning On/OFF
in Vikings Engine's case
it's Wiki claims
they used to pressurize their tanks with this
But ISRO does not do this
ISRO tanks are pressurized using Helium
here are some images of Viking
You can clearly see the Turbine in between.
the red pipe on the left carries UDMH
the orange golden pipe carries N2O4
and a small blue color pump if you notice
in the right corner
this is the water pump
the round spheres is
the gas generator
water is pumped from below
this is a very different system
dont really know why they choose this
some gas geenrator cycle engines...
they run a fuel rich mixture
so it isn't a perfect combustion ratio
it has less O2 and more fuel
so the exhaust of the GG is cooler relatively
viking Engine technical diagram!!
you can see the pump lines
carrying all the fuels
water pump leading to the GG
hope you learned something new today
Hope i get to meet Nambi sir
Jai Hind Jai Bharat
