India returns PSLV to service with launch of Cartosat-2F
Nearly four and a half months after their last launch ended in failure, the Indian Space Research Organization (ISRO) successfully delivered the Cartosat-2F Earth-observation satellite to on Flight PSLV-C40.
The Polar Satellite Launch Vehicle (PSLV), outfitted in its most powerful XL configuration — lifted off from the Satish Dhawan Space Center at 10:58 p.m. EST on January 11, 2018 (03:59 GMT on January 12), carrying the 1,570-pound (712 kilogram) primary satellite, along with 30 smaller secondary payloads, to a 314-mile (505-kilometer) high, Sun-synchronous orbit.
The countdown proceeded smoothly, with technicians working no issues leading up to the planned launch time. At T-3 seconds, the PSLV’s roll-control thrusters sprang to life, followed shortly thereafter by the ignition of the first stage and four of the six S12 solid-fueled boosters.
With both the first stage’s S139 motor and the strap-on boosters burning a solid mixture of hydroxyl-terminated polybutadiene (HTPB) fuel, the ignition sequence was quick and the vehicle rapidly left the pad.
After clearing the tower, the vehicle rolled to assume a nearly due-South heading and climbed over the Indian Ocean. As the PSLV continued to accelerate, the two remaining boosters were ignited in-flight at T+25 seconds.
Having exhausted their fuel supply, four of the six strap-on boosters burned out 49 seconds after launch and were jettisoned nearly 21 seconds later, less than a second after the two remaining boosters consumed their solid propellant. The two air-lit boosters were discarded just over 90 seconds after liftoff in a lead-up to the first stage’s burnout at T+105 seconds.
Following a short coast, the first stage separated and the second stage’s Vikas engine came to life. The liquid-fueled engine — burning a mixture of unsymmetrical dimethylhydrazine and nitrogen tetroxide — provided 180,000 pounds-force (799 kilonewtons) of vacuum thrust, and powered the vehicle for the next 2 minutes and 38 seconds.
Though the mission had been nominal to this phase, it was quickly reaching the previous launch’s fault point — payload fairing separation. That flight, designated PSLV-C39, ended in failure when the vehicle’s fairing — also known as the heat shield — did not separate and detach from the rocket. That extra mass was never intended to reach orbit and caused the final stage to reach a significantly lower orbit than intended. Additionally, the still-attached shield prevented any of the payloads from being deployed.
However, engineers appeared to have addressed the issue in the time between the two flights and the fairing separated on-time and without incident.
The second stage, with its Vikas now starved of fuel, separated 4 minutes and 20 seconds after liftoff, allowing the penultimate stage to continue the task of delivering the Cartosat-2F satellite, and its 30 companions, to orbit.
Two down, two to go…and 31 satellites deployed
With half the vehicle’s stages discarded, and nearly half the needed velocity for orbit already achieved, it fell to the third stage to continue the climb to a Sun-synchronous orbit. The HPS3 solid-fueled motor, providing 54,000 pounds-force (240 kilonewtons) of vacuum thrust, performed nominally for its 83 seconds of operation and burned out at T+345 seconds.
The mission then began a nearly two-and-a-half minute coast phase before the spent third stage separated. After allowing approximately 10 seconds for the discarded stage to separate from the fourth stage, the twin L-2-5 engines sprang to life.
Providing up to 3,400 pounds-force (15.2 kilonewtons) of thrust over the next seven-and-a-half minutes, the pair of liquid-fueled engines placed the vehicle precisely where needed for payload deployment. Following a short coast phase to allow for engine outgassing to cease, Cartosat-2F was successfully deployed.
The Earth-observation satellite will undergo a series of checkouts and will join its Cartosat brethren in providing India with detailed imaging for use urban development, infrastructure planning, and other governmental needs once it becomes operational.
Following the successful deployment of the primary payload, the 30 co-passengers separated in relatively short order. The secondary payloads, representing interests from the United States, Finland, South Korea, Canada, India, and the United Kingdom, all cleared the launch vehicle nominally and marked the second-highest number of satellites deployed on a single ISRO mission.
India’s next launch will be their Geosynchronous Satellite Launch Vehicle (GSLV) on Flight GSLV-F08. The mission, slated for later in January, will deliver the GSAT 6A telecommunications satellite to a geosynchronous transfer orbit, and the rocket will feature an upgraded indigenous cryogenic upper stage.
Video courtesy of ISRO / DoordarshanNational
Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.