|Launch vehicle||Proton K with Block DM3 upper stage|
|Launch site||Baikonur, Kazakhstan|
|Description||Fourth stage partial failure|
|Cause||Defective wear-reducing coating on seals|
|Payload||AsiaSat 3 (Television satellite)|
|Desired orbit||Geostationary transfer orbit|
A Russian investigation commission in April 1998 determined that the physical root cause of the failure was use of a defective wear-reducing coating applied to the internal seals of the fourth stage engine high-pressure liquid oxygen pump. The defective seals caused an excessive volume of gaseous oxygen to leak into the liquid oxygen pump's impeller chamber, inducing pump cavitation. The resulting reduced oxygen flow led to an anomalous propellant mix in the engine's gas generator during the startup sequence, thereby triggering a preplanned, automatic emergency shutdown of the engine about one second after the engine restart command.
It was announced that a corrective action plan had been adopted by RSC Energia, builder of the Block DM, and its subcontractors to remove and replace the seals with defective coatings from the Block DM upper stages and to use uncoated seals in all new-build engines.