|GSLV Mk I|
|Launch vehicle||GSLV Mk I|
|Launch site||Satish Dhawan Space Centre, India|
|Date/Time||2006-07-10 12:08 UTC|
|Description||First stage failure|
|Cause||Defunct strap-on booster|
|Desired orbit||Geostationary transfer orbit|
A defective propellant regulator of a strap-on motor caused the failure of ISRO's Geosynchronous Satellite Launch Vehicle (GSLV) F02 mission on 10 July 2006, according to the Failure Analysis Committee (FAC).
The primary cause for the failure was the sudden loss of thrust in one out of the four liquid propellant strap-on stages (S4) immediately after lift-off at 0.2 seconds. With only three strap-on stages working, there was significant reduction in the control capability. However the vehicle attitude could be controlled until about 50 seconds. 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 thrust of the liquid engines used in the strap-on stages is precisely controlled by a set of regulators. Detailed analyses have indicated that in the S4 engine the thrust control was not effective. Instead of stabilising at 5.85 MPa (Mega Pascal) chamber pressure, it reached 7.11 MPa at 2.8 seconds. This was much beyond the design limits and the engine failed at 0.2 seconds after lift-off, that is 5 seconds after its ignition.
The reason for this malfunction could be an inadvertent error in manufacturing of the propellant regulator, 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 FAC has concluded that the design of GSLV is robust and recommended implementation of strict control on fabrication, inspection and acceptance procedures. ISRO said that the FAC conclusions and recommendations have been accepted and necessary action has been initiated to implement all of them.