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Monday, September 5, 2016

GSLV F05 Flight .. scheduled for 8th Sept.

India's GSLV-F05 carrying the Insat 3DR comsat is on the Second launch pad awaiting its Sep. 8 launch.  Second Launch Pad with a assembly tower of 82 M hight ( equivalent to about 25 storey building ) can be used to launch both PSLV and GSLV rockets of ISRO. These images show a comparison of GSLV and PSLV both graphically and in images.


NOTE: The rocket is also called as Motor or Engine. We may use these terms interchangeably in the following write up.
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Come Sept 8th, 2016, ISRO will launch INSAT-3DR satellite which  is for Meteorological Imaging applications using a GSLV rocket. This flight is named as GSLV F05 flight.

We will try to give here some facts which may make your viewing of Launch Video  an interesting affair rather than just a clap clap affair. 

INSAT-3DR  is a Meteorological applications satellite,  Imaging in Middle Infrared band and  in two Thermal Infrared bands. It also carries a Data Relay Transponder as well as a Search and Rescue Transponder.
It has a lift-off mass of 2211 kg, ( including 1255 kg of propellant).  The  solar array can generate 1700 Watts of power. 

To give an idea of its weight and size here is a fact sheet comparing it with a popular car:

                The Car                                            INSAT-3DR

  Weight :   1350 Kgs                                       2200 Kgs   ( So it weighs about 1.5 times car )
   Size   :  1.5M x  1.7M  X  3.6M                   1.6M  X 1.5M  X  2.4M

GSLV Rocket :

The GSLV F05 is a 3 stage rocket  with a  Cryogenic Liquid Upper stage.

The 1st stage is made up of a central core and 4 strap-on motors.  The central core is a massive 2.8 M diameter. It contains 138 Tons of solid fuel which can produce a thrust of 4700 kN.  

Each of  4  strap-on rockets ( called L40 )  is  2.1 meters in diameter,  contains 42 Tons of propellant and can produce a thrust of 680 kN.   Thus altogether the 1st stage ( Central core + 4 add-ons ) creates a force of  about 7400 kN to lift the rocket off the pad.
BTW how much fuel do these giants consume? Hold your breath: Altogether the 1st stage consumes more than 2400 Kgs per second. But there is a silver lining to this consumption - every second the rocket is loosing 2400 kgs of dead weight so it aids in  accelerating the rocket in addition to the brute force acceleration generated by the engines! So by the time the 2nd stage ignites, the rocket is lighter by 360,000 kgs. And when the 2nd stage separates the dead-weight of 1st stage also reduces the load  further. 
                                                             The graph here shows the events during launch.    The X Axis is Time in seconds from liftoff. Red line is the height that the rocket reaches and Blue line is the speed of rocket multiplied by 40.    Actual speed is less than 10 Km/s but it appears just as the green line near X axis so it was multiplied by 40 to show the variations as seen in Blue line.
Incidentally, the 1st stage is ignited a bit differently than the PSLV wherein add-on motors are switched on 2 first, and then the remaining 2. In case of GSLV, 4.8 seconds before the actual liftoff time ( referred as To ) , the four L40 boosters  are ignited simultaneously. Notice that the central main core is not yet ignited so the thrust is not sufficient to lift the rocket. After ensuring that these 4 engines are working properly the central core is ignited at To and these five motors together lift the rocket vertically up to clear the height of launch facilities. Then it starts turning ( Technically called Pitching and Rolling maneuvers ) seawards.

After burning the 1st stage for about 2.5 minutes the the second stage is ignited ..  yes, the 1st stage is still attached and is still burning at this time! This method is called Hot-Staging and it helps in pushing off the 1st stage by the exhaust of 2nd stage. The 2nd stage is 2.8 meters in diameter,  contains 45 Tons of propellant and can produce a thrust of 800 kN. 
By this time the rocket would have risen to an altitude of 72 Kms and attained a speed of 2.4 Kms/sec. 
( A bit off topic : remember that the scramjet test of ISRO a few days ago was carried out at 6 Mach speed which is nearly this speed and so it is possible to use the scramjet  engine in place of the current upper stages if required in future. )
While all this is happening the rocket also does maneuvers to turn east and a bit to south so that ultimately  it is possible to release the satellite on equator.

The 2nd stage burns for 140 seconds lifting the altitude from 72 Kms to 132 Kms. The speed also increases from 2.4 Kms/sec to 4.9 Kms/sec.

 In between, at 115 Kms altitude ( 228 seconds from To ) , the cover which protects the satellite from atmospheric drag etc ( Payload fairing ) gets ejected since the rocket has climbed above the atmosphere at this height making the protective cover redundant.

At 132 Kms ( 293 seconds from To) the 2nd stage is shut off and ejected and 3rd Cyogenic Liquid Engine stage is ignited. 
It is fuelled with Liquid Hydrogen and Liquid Oxygen. This stage is also 2.8 meters in diameter.  This Cryo stage has the advantage that its output power can be controlled between 70 kN and 95kN.  

Cryo Stage burns for a long duration ; 293 seconds to 1012 seconds and it increases speed from 4.9 km/s to 9.7 Km/s while the altitude increases from 133 to 220 Kms.

At this time  (  1012 seconds from To ) the cryo is shut off because the the roket is now in the required orbit moving around Earth due to gravitational force on its own.

The satellite is separated a little later from the upper stage 1024.7 seconds from   To  at an altitude of 230 Kms.

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Update : 7sept/2230 IST

In order to avoid the clash with air crafts flying in vicinity of SHAR  the aviation authorities publish Note To Airmen  ( NOTAM ) about the zone to be avoided.

Based on that NOTAM here is a likely path that the rocket will take?

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