After three difficult years, dogged by the bad luck of two back-to-back failures, and after coming tantalizingly close to a return to flight last summer, the Indian Space Research Organisation (ISRO) is primed to fly its Geostationary Satellite Launch Vehicle (GSLV) Mark II on Sunday, 5 January. Liftoff has been postponed repeatedly since October 2012, due to ongoing tests of a home-grown Indigenous Cryogenic Upper Stage, which will be making its second flight, and the need to resolve issues which caused the loss of the previous Mark II mission in April 2010. Finally, last August the vehicle underwent a relatively smooth countdown at the Satish Dhawan Space Centre, on the barrier island of Sriharikota, within India’s southern state of Andhra Pradesh. However, a leak was detected in the UH25 (unsymmetrical dimethyl hydrazine) fuel system of the rocket’s liquid-propelled second stage during the pressurization process, and the launch attempt was scrubbed.
The 29-hour countdown commenced Sunday, 18 August, and encompassed the final loading of liquid propellants—unsymmetrical dimethyl hydrazine and nitrogen tetroxide—aboard the GSLV’s four strap-on boosters and into its cryogenic second and third stages. Both procedures were described by ISRO as “normal,” and it appeared that the detection of the UH25 leak occurred less than two hours ahead of the scheduled liftoff on Monday, 19 August, after which post-scrub efforts to drain the liquid propellants swung into action. Although it was initially reported that the launch window for the GSLV’s “Demonstration-5” (or “D-5”) flight would be kept open for its remaining period from 20 August until 5 September, it soon became clear that the problem would take far longer to resolve.
In the days that followed, ISRO announced that about 1,650 pounds (750 kg) of unsymmetrical dimethyl hydrazine leaked from the second stage, leading to contamination of the area around the launch pad. “It took six days of round-the-clock operations before the contamination could be reduced to a safe level to enable movement of the GSLV-D5 back to the vehicle assembly building,” ISRO explained, and this rollback was not concluded until 26 August, after which the 161-foot-tall (49-meter) vehicle was destacked. A high level task team, chaired by Shri K. Narayana, the former director of the Satish Dhawan Space Centre, was convened, with suspicion centering on “the lower portion of the propellant tank or the fluid lines between the tank and fuel filling system of the second stage.” A new second stage was assembled and all four strap-on boosters were replaced, with the first stage and Cryogenic Upper Stage inspected for discrepancies and preserved.
Should the mission fly without incident on Sunday, it will mark the second flight of the uprated Mark II configuration of the GSLV and will deliver India’s GSAT-14 communications satellite into orbit. Unlike the earlier Mark I, the Mark II does not rely upon a Russian-built third stage, which ISRO has blamed for failing to operate properly on several occasions, triggering multiple mission failures. The new variant is reportedly capable of delivering a payload weighing up to 11,000 pounds (5,000 kg) into low-Earth orbit and up to about 5,000 pounds (2,270 kg) into geostationary transfer orbit, but both types of the GSLV have exhibited a dismal success record. Launched seven times between April 2001 and December 2010, it has suffered four outright Losses of Vehicle and Payload, one mission in which its satellite cargo was inserted into an improper orbit, and only two full successes.
The three-stage GSLV was originally conceived as a means of eliminating India’s reliance upon foreign rockets for its geostationary-orbiting satellites. It utilizes components of the highly reliable Polar Satellite Launch Vehicle (PSLV) and comprises a first stage fed by a single solid-fueled engine and four strap-on liquid-fueled boosters, topped by liquid-fueled second and third stages. The first stage solid fuel is hydroxyl terminated polybutadiene, whilst the Vikas engines of the strap-on boosters are powered by unsymmetrical dimethyl hydrazine and nitrogen tetroxide; combined, these generate 610,000 pounds (276,700 kg) of propulsive yield at liftoff.
After launch, the first stage burns for approximately two minutes. Following the separation of both it and the four boosters, the second stage—fueled by unsymmetrical dimethyl hydrazine and nitrogen tetroxide—will ignite, its Vikas engine burning fiercely with 160,000 pounds (72,580 kg) of thrust for 150 seconds to continue the climb toward orbit. Finally, the cryogenic third stage, which operates on liquid hydrogen and oxygen in a pair of separate aluminum tanks connected by an inter-stage, will burn with 16,500 pounds (7,480 kg) of thrust to propel the GSAT-14 payload into geostationary transfer orbit. Throughout ascent, S-band telemetry and C-band transponders will enable controllers to continuously monitor vehicle parameters, including tracking, range safety, and preliminary orbit insertion.
Sunday’s launch, as with all previous GLSVs, will occur from the Satish Dhawan Space Centre. According to ISRO, liftoff is scheduled for 4:18 p.m. India Standard Time (12:18 p.m. UTC) and the GSLV was rolled out from its assembly building to the launch pad’s umbilical tower on 28 December. The 29-hour countdown is due to commence at 11 a.m. IST (7 a.m. UTC) tomorrow (Saturday).
The vehicle will have much to prove on its first foray in more than three years. Its maiden (“Development-1,” or “D1”) voyage in April 2001, flying in the Mark I(a) configuration, suffered an engine shortfall when its Russian-built upper stage burned for 12 seconds less than planned. This delivered the GSAT-1 payload into an improper orbit, whose apogee was 2,500 miles (4,000 km) lower than intended. Although ground controllers managed to nudge the satellite toward geostationary orbit, they did so at the expense of using all of its attitude control propellant, and GSAT-1’s tasks of digital audio broadcasting, compressed digital television signal transmission, and associated internet services could not be achieved.
Success was finally achieved two years later, in May 2003, when a second Mark I(a) vehicle flew the “D2” mission and placed GSAT-2 into geostationary orbit. Perhaps a little prematurely, the GSLV was declared operational, and in September 2004 it carried the EDUSAT/GSAT-3 payload into orbit to handle India’s demands for an interactive satellite-based education system. However, success and failure went hand in hand, and in July 2006 the uprated Mark I(b) configuration veered outside permitted limits during ascent and had to be remotely destroyed over the Bay of Bengal by the range safety officer. Its primary payload—the Insat-4C multi-purpose satellite—was lost in the accident.
Another Loss of Vehicle event occurred in September 2007, when a Mark I(b) suffered an underperformance of its third stage and failed to deliver Insat-4CR into geostationary orbit, due to a guidance system error. The satellite was eventually maneuvered into its proper orbit by ground controllers, but at the expense of reducing its operational lifetime from 10 to five years. Two more failures followed. The first flight of the new Mark II vehicle (“D3”) in April 2010, with its ISRO-designed cryogenic third stage, developed a turbopump fault and resulted in the loss of the GSAT-4 communications and navigation satellite. This would have been India’s first spacecraft to utilize ion propulsion. Most recently, on the “D4” mission in December 2010, a Mark I(c) was lost when its four liquid-fueled boosters failed to respond to commands, and the vehicle and GSAT-5P communications satellite payload had to be destroyed by the range safety officer.
Late in 2011, S. Ramakrishnan, head of ISRO’s Liquid Propulsion Systems Centre (LPSC) at Mahendragiri, declared that the GSLV-D3 turbopump fault had been isolated, corrective actions taken, and computer simulations concluded and validated. “We did a thorough analysis of the D3 flight and identified the reasons behind its failure,” explained P.S. Veerarghavan, director of Vikram Sarabhai Space Centre, quoted in 2012. “The analysis called for a redesign of certain components in the cryogenic propulsion system and the same has now been addressed and is being put through multiple testing.” Key focuses included high-altitude “hot-fire” tests to verify the performance of the third stage turbopump. Other recommended steps included strengthening the payload shroud. In early May 2013, the Indian-built Indigenous Cryogenic Upper Stage for the GSLV-D5 mission was transferred from LPSC Mahendragiri to Sriharikota for final checkout. On 5 July, the process of integrating the upper stage with the lower two stages of the GSLV got underway.
Assuming a successful climb to orbit, the rocket will deliver GSAT-14 as a replacement for the EDUSAT/GSAT-3, which has been operational in orbit for almost a decade. The 4,400-pound (2,000-kg) satellite is equipped with six Ku-band and six C-band transponders, which will cover the entire subcontinent of India, together with Ka-band beacons for studying the impact of climate on the Ka-band satellite communications links in the region.
Although Sunday’s GSLV-D5 mission is scheduled to last barely 17 minutes and eight seconds, from liftoff through payload separation, its criticality of success cannot be understated. India has expressed its urgent requirement for a reliable cryogenic upper stage to boost its large satellites to geostationary altitudes. This will serve to end its reliance upon foreign launch vehicles, most notably Europe’s Ariane, and success will stand the GSLV in better stead to serve as the carrier for the long-awaited Chandrayaan-2 mission in 2015. The latter will place a spacecraft into orbit around the Moon and deploy a landing craft and a single roving vehicle to touch down on the surface. Although this will be India’s second mission to the Moon, it will be markedly more complex than its predecessor, the 2008-launched Chandrayaan-1.