Failed mission of the PSLV-XL with IRNSS-1H under the fairing

ISRO PSLV-XL rocket failed during its 39th flight - for the first time since first C1 mission in 1997.

Today, on August 31, 2017 ISRO launched their PSLV-XL rocket from Satish Dhawan Space Center. Mission objective was delivering to orbit IRNSS-1H (Indian Regional Navigation Satellite System) navigational satellite. Satellite should be deployed on 284 km x 20650 km orbit and later in following weeks reach 35800 GEO orbit and pass commissioning process and join constellation of seven other IRSS satellites. Main task for  IRNSS-1H was to replace first IRNSS-1A satellite remaining on orbit since 2013. Satellite placed on 35,706.1 km  km orbit failed after 3 years of service. Most important instruments inside spacecraft, three Rubidium clocks failed one after another with first malfunction noticed on July 2016. Unfortunately today after reaching space by PSLV-XL and IRNSS-1H problems appeared and interrupted deployment of the spacecraft.

PSLV-XL was launched at 19:00 UTC with four hours of delay. Six solid fueled booster launched in ordinary sequence with last pair ignited at T+25'. Boosters were jettisoned after first minute of flight,  what was followed by dropping first stage at T+1'50". Second stage was ignited and was cut off at around T+3'20"; next, third stage was started and burn for another four minutes. It was followed by the ignition of the fourth stage. As first three stages seemed to operate nominally, weighing 2500 kg fourth stage had some problems with two two hydrazine-fueled L-2-5 engines just after ignition. But main problem during this mission appeared in the end of burn of second stage. Payload fairing failed to separate correctly at T+3'23" and satellite was trapped at payload adapter when rocket flight across dense layers of atmosphere to LEO. With additional mass of unreleased fairing fourth stage failed to reach designated orbit of  284 km x 20650 km and it was positioned at 167 km x 6554 km orbit. As ground control center decided to start procedure of deploying satellite 90 seconds earlier than it was planned (T+19'25"), it was impossible to release satellite. Fourth stage with IRNSS-1H remains on orbit probably without any chance of starting its planned for 10 years mission.

PSLV-XL is extended version of Polar Satellite Launch Vehicle which was developed by Vikram Sarabhai Space Centre in the beginning of the nineties with maiden flight of on 20 September 1993. PSLV-XL was upgraded with larger (height is 13.5 m with diameter at 1 m) six strap-on boosters each able to store 30% more fuel (12200 kg) than regular boosters of PSLV. Rocket with length at 44 m weighs 320 t at start (comparing to 295 t of PSLV-G). Central core has four stages: first stage (with mass at 138200 kg, diameter at 2.8 m and length of 20 m) is powered by solid fueled (HTPB) S139 engine with 4800 kN of thrust. Second stage (weight at 24000 kg, diameter at 2.8 m and long for 12.8 m) is equipped with one Vikas engine liquid fueled with N2O4/UDMH and providing 799 kN of thrust. Third stage (mass at 7600 kg, diameter at 2 m and length of 3.6 m) is solid fueled with single HPS3 engine which generates 240 kN of thrust. Fourth stage is powered by two L-2-5 engines with thrust at 15.2 kN fueled with liquid MMH/MON propellant and weighs 2500 kg while its length is at 3 m and diameter at 1.3 m. PSLV-XL is able to lift up to 1425 kg to GTO orbit.

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