Lack of pressure may have led to Chandrayaan-2 mission abortion

Chennai Two retired official of Indian space organisation said that nonbuilding of sufficient pressure in the helium tanks in the Bahubali rocket could be the reason for calling off the moon landing mission Chandrayaan2 one hour before the rockets take offThe rocket Geosynchronous Satellite Launch VehicleMark III GSLVMk III was supposed to lift off at 251 am on Monday with Indias second moon mission spacecraft Chandrayaan2A technical snag was observed in launch vehicle system one hour before the launch As a measure of abundant precaution Chandrayaan2 launch has been called off for today Revised launch date will be announced later ISRO tweeted and didnt elaborate furtherA technical snag was observed in launch vehicle system at 1 hour before the launch As a measure of abundant precaution Chandrayaan2 launch has been called off for today Revised launch date will be announced latermdash ISRO isro July 14 2019Retired officials of Indian Space Research Organisation ISRO said that there should be proper pressure in the liquid fuel tanks so that there is a continuous flow of fuel to the combustion chamber A retired ISRO official said While the fuel is fed into the combustion chamber from the bottom helium gas is filled from the top It seems sufficient pressure was not being built up and hence the launch was called off According to him the flow of fuel to the combustion chamber should be uniform for the rocket to flyIn 2006 the GSLVF02 a different variant of GSLV went out of control less than a minute after liftoff and had to be destroyed in the air after it started breaking up The reason for the failure an expert committee in its failure analysis report said was that a propellant regulator in one of the four strapon liquid motors had much higher discharge coefficient in its closed conditionThe reason for this could be an inadvertent error in manufacturing which escaped the subsequent inspection and acceptance test procedures This regulator has functioned satisfactorily in all the previous 50 engines manufactured and tested so far the report saidThe primary cause for the failure was the sudden loss of thrust in one out of the four liquid propellant strapon stages S4 immediately after liftoff at 02 sec With only three strapon stages working there was a significant reduction in the control capability the report saidHowever the vehicle attitude could be controlled till about 50 sec At the same time the vehicle reached the transonic regime of flight and the vehicle attitude errors built up to large values resulting in aerodynamic loads exceeding the design limits thus leading to break up of the vehicle the report addedAccording to that report the thrust of the liquid engines used in the strapon stages is precisely controlled by a set of regulatorsDetailed analyses have indicated that in S4 engine the thrust control was not effective Instead of stabilising at 585 MPa Mega Pascal chamber pressure it reached 711 MPa at 28 sec This was much beyond the design limits and the engine failed at 02 sec after liftoff that is 5 sec after its ignition the report saidThe larger flow of propellant led to higher operating pressure in the gas generator 47 MPa against design specification of 36 MPa Due to this higher operating pressure of the gas generator the water flow rate into it got reduced The combined effect of larger flow of propellants and reduced flow of water led to a very high gas temperature of 1823 K against design specification of 900 K and pressure of 47 MPa against the design specification of 36 MPaThe very high operating pressure and temperature resulted in the structural failure of the gas generator The consequent abrupt stopping of the turbo pumps that feed propellants at very high pressures to the engines led to loss of thrust of S4 engineThe water calibration tests conducted simulating the malfunction of the propellant regulator hardware could closely reproduce the flight phenomenon thereby confirming the larger flow area the report saidAt that time ISRO ruled out any sabotage theories and said the quality checks and inspections has been strengthened Incidentally even the very first flight of GSLV slated for 2832001 was automatically aborted seconds before the liftoffThat launch was aborted with the automatic shutdown of the main engine just a second before the lift off That too after the four liquid propulsion strapon boosters started burning The automatic shut off system was activated when it sensed that one of the strapon boosters did not develop the required thrust The vehicle was immediately disarmed The rocket was later flown on 1812001 carrying GSAT1 satelliteEdited by midday online desk with inputs from IANSCatch up on all the latest Crime National International and Hatke news here Also download the new midday Android and iOS apps to get latest updates