The launch of the GSAT-19 on board ISRO's geosynchronous satellite launch vehicle (GSLV) MK III to take place at 5:28 PM on 5 June 2017 is the first developmental flight of the rocket. The mission is called the GSLV MKIII-D1. The heavy lift vehicle is capable of lifting payloads of 4,000 kg into geosynchronous transfer orbit (GTO), and opens up the possibility of India commercialising launch services for a heavier category of satellites. The rocket can also deploy payloads of 10,000 kg into low Earth orbit (LEO).
In 1980, India joined a select club of countries with satellite launch capabilities with its first generation rocket, the satellite launch vehicle (SLV). The second generation was the Augmented Satellite Launch Vehicle (ASLV). The third generation was the Polar Satellite Launch Vehicle (PSLV) which had its first flight in 1994. The PSLV proved to be one of the most reliable rockets in the world, with a record of 38 successful launches till February 2017, when it was used to launch a record setting 104 satellites in one launch. The GSLV MK II is the heaviest rocket currently being used by ISRO, and was used to launch the South Asia Satellite, and ISRO plans to use it for the Chandrayaan-2 mission as well.
The GSLV MK III is the fifth generation launch vehicle by ISRO. Although currently known as the "Fat Boy", it is expected to replace the PSLV as the "workhorse" rocket. The design and development of the GSLV MKIII was based on ISRO's three and a half decade long experience in handling solid, liquid and cryogenic rocket propulsion technologies. The two S200 strap on motors used by the GSLV MKIII is an evolution of the S139 solid core motor used in both the PSLV and the GSLV MKII. Two clustered Vikas engines used in the PSLV and GSLV MKII. The first suborbital test flight of the GSLV MKIII was conducted on 18 December, 2014. The launch tested a crew re-entry module for future ISRO manned missions, which is expected to use the GSLV.
The C25 cryogenic engine on the GSLV MKIII-D1 mission is the third of three stages in the rocket. It is integrated on top of the L110 stage with Hypergolic liquid propellant. All the three stages are new developments. There are advanced navigation, guidance, control and separation systems on the rocket as well. The cryogenic stage will be ignited 2 seconds after the separation of the L110 stage, which will be 322 seconds into the sixteen minute flight. The c25 will burn for 643 seconds, and this will allow for the insertion of the GSAT-19 into the intended geosynchronous transfer orbit. The indigenous cryogenic engine is intended to replace a cryogenic stage imported from Russia.
ISRO started testing the cryogenic stage back in 2000. The test was conducted at the Liquid Propulsion Systems Centre test complex at Mahendragiri in Tamilnadu. The test had been planned for a 30 second burn, but was aborted after 15 seconds because of anomalies. The test marked the beginning of a series of ground based tests, during which data from the instruments were collected to make corrections and adjustments to the rocket, to ensure smooth functioning in future launches. In March 2002, after a series of tests lasting 10, 40, and 200 seconds, the cryogenic stage was fired for a full 12 minutes, or 720 seconds. In September 2002, the cryogenic stage was fired for 1000 seconds.
An earlier indigenous cryogenic stage with lower capacity, and part of the GLSV MK II uses liquid propellants stored at very cool temperatures. The liquid hydrogen is stored at -250º C and the liquid oxygen is stored at -196º C. In 2006 ISRO verified that all the components of the stage, including the engine, insulated propellant tanks, booster pumps, fill and drain systems, pressurization systems, gas bottles, igniters, cold gas orientation and stabilization system were working as intended in unision. The "Hot Tests" continued into 2008 as well. In 2010, the GSLV-D3 mission conducted the first test flight of the indigenous cryogenic engine. The launch was a failure, and the rocket with the GSAT-4 on board ended up in the sea.
In 2012, the cryogenic upper stage was successfully tested again for a duration of 200 seconds at the Liquid Propulsion Systems Centre (LPSC) test facilities at Mahendragiri. The stage performed as expected, and the test was successful. The GSLV D-5 mission in 2014 successfully flight tested the cryogenic stage with the launch of the GSAT-14. The duration of the flight was 17 minutes and four seconds, about a minute longer than today's mission.
The cryogenic engines developed by India for use on the GSLV MKII were giving about 7 tonnes of thrust. ISRO then developed the high thrust cryogenic engine, giving 19 tons of thrust, which was first tested in 2015. The duration of the test was 800 seconds, which was 25 percent more than the intended burn duration in the flight. This cryogenic engine allowed for four ton class satellites to be placed into GTO, whereas the capacity so far had only been two tons. The cryogenic stage was named as the C25, and the temperature of the liquid propellants was slightly tweaked. The liquid hydrogen was stored at -250º C and the liquid oxygen was stored at -196º C. In January 2017, ISRO sucessfully test fired the cryogenic upper stage for 50 seconds.
The high thrust cryogenic stage was realised by the Liquid Propulsion Systems Centre (LPSC), an ISRO facility dedicated to developing liquid propulsion systems for the Indian space program. Vikram Sarabhai Space Center (VSSC), ISRO Propulsion Complex (IPRC) and the flying saucer shaped Sathish Dhawan Space Centre (SDSC) SHAR contributed to the design of the engine. The upper stage uses a combination of Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) propellants. Indian industries have manufactured the engine and the various sub systems on the cryogenic stage.
ISRO has indicated that it is in the process of developing a semi-cryogenic stage for a future heavy lift rocket. The engine will use a combination of liquid oxygen (LOX) and ISROSENE, which is propellant grade kerosene. The combination of propellants is both environmentally friendly and low cost. Some components meant to be used in the stage have already been tested. The preliminary configuration and engineering details for the stage has been worked out by ISRO scientists.