India’s Geosynchronous Satellite Launch Vehicle (GSLV) has ended a run of four consecutive launch failures by deploying the GSAT-14 communications satellite on Sunday, following launch at 10:48 UTC. The mission – from the Second Launch Pad at the Satish Dhawan Space Centre – was a realigned attempt, following the scrub and rollback for repairs on the rocket last year.



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This launch was set to take place in August of last year. However, several problems – not least during its August 19 countdown, when its second stage began leaking large amounts of hydrazine fuel over the launch pad.

A lengthy delay followed, not least because the entire vehicle had been contaminated by the leak. As a result, the vehicle was rolled back and dismantled. It now sports two new stages and refurbished boosters, while the second stage is now utilizing aluminium alloy tankage.

The Geosynchronous Satellite Launch Vehicle, first flown in 2001, is the newest rocket in India’s fleet, designed to place communications satellites into geosynchronous transfer orbits. It is the fourth rocket to be developed by India, following the Satellite Launch Vehicle, Augmented Satellite Launch Vehicle and Polar Satellite Launch Vehicle.

India’s first orbital launch attempt took place on 10 August 1979, with a Satellite Launch Vehicle carrying the Rohini Technology Payload, or RTP. This launch failed to orbit after the rocket’s second stage thrust vector control system malfunctioned. The next launch on 18 July 1980 saw the SLV successfully orbit the Rohini RS-1 satellite.

Two more SLVs were launched; in May 1981 and April 1983, with Rohini RS-D1 and RS-D2 respectively. The 1981 launch was unsuccessful, with RS-D1 being placed into an unusable, rapidly decaying, low orbit, from which it reentered within nine days of launch. The SLV, which is also known as the SLV-3, retired from service with a record of two successes and two failures.

The SLV was replaced by the Augmented Satellite Launch Vehicle, which consisted of a similar core vehicle to the SLV-3, but with an additional first stage consisting of two more S-9 rocket motors. The S-9 was used as the first stage of the SLV, which became the ASLV’s second stage, and is still used as a booster rocket on some PSLV launches.

The first ASLV launched in March 1987, carrying the SROSS-A, or Stretched Rohini A, satellite. The second stage failed to ignite, and as a result the rocket was unable to achieve orbit. The next launch, which occurred in July 1988, fared no better, with the rocket’s attitude control system failing late in first stage flight.

The third ASLV reached low Earth orbit, however the incorrect spin stabilization of the rocket’s fifth stage resulted in the orbit being lower than had been planned, and the SROSS-C satellite could only return limited data for less than two months of a planned six month mission.

The fourth and final ASLV launch carried a replacement for SROSS-C; SROSS-C2. On this mission the ASLV performed successfully, deploying the satellite into its target orbit. SROSS-C2 was able to operate for four years – more than eight times its design life. Following the fourth launch, which took place on 4 May 1994, the rocket was retired in favor of the PSLV, which had made its first test flight the previous year.

The PSLV, or Polar Satellite Launch Vehicle, remains the workhorse of India’s space program. It has achieved 23 successful launches from 25 attempts since its maiden flight on 20 September 1993.

The maiden flight, which carried the IRS-1E satellite, remains the rocket’s only outright failure; the rocket’s attitude control system failed at second stage separation, with the vehicle unable to make orbit.

Following two successful launches, carrying IRS-P2 and IRS-P3 in 1994 and 1996 respectively, the PSLV was declared operational. The payload for the first operational mission was IRS-1D, which was destined for a sun-synchronous orbit.

PSLV C1, as the rocket was designated, lifted off from Sriharikota on 29 September 1997, however a fourth stage helium leak left the rocket unable to reach its target.

Instead, IRS-1D was placed into a lower-than-planned orbit. The satellite was able to reach a usable orbit, still somewhat lower than had initially been planned, at the expense of most of its own propellant supply.

The IRS-1D launch was the most recent failure of a PSLV; in the 20 launches since it has performed perfectly. Most of the PSLV’s flights have placed remote sensing satellites into sun-synchronous orbit; however it has been used for other launches.

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The seventh PSLV launch, in September 2002, carried the METSAT-1 weather satellite bound for geosynchronous orbit. METSAT-1 was later renamed Kalpana-1 after astronaut Kalpana Chawla, who was killed in the Columbia accident.

Two other launches have been made to geosynchronous transfer orbit; a communications satellite, GSAT-12, in 2011, and the IRNSS-1A navigation satellite last month. In October 2008, India used a PSLV to launch its first mission to the Moon, Chandrayaan-1.

The first commercial PSLV launch took place in April 2007, carrying the AGILE gamma-ray astronomy satellite for the Italian space agency. The next launch, in January 2008, orbited Israel’s TecSAR radar reconnaissance satellite. The PSLV has also launched two radar imaging satellites for the Indian military; RISAT-2 which was built with assistance from Israel, and later RISAT-1, which India developed independently.

A launch last year carried the SPOT-6 satellite for the French space agency, CNES, and two Franco-Indian scientific satellites, Megha-Tropiques and SARAL, have also been launched.

The most recent PSLV mission lofted the Mars Orbiter Mission (MOM) in November.

PSLV launches have carried a number of secondary payloads, including the SRE-1 satellite which was recovered after several days in orbit in 2007. In recent years, many CubeSats have found launch opportunities on the PSLV. One launch carried ten payloads – the most an Indian rocket has launched to date, although not the most of any launch by any country.

With the PSLV operational, India looked to develop a rocket capable of launching its communications satellites to geosynchronous orbit. While the PSLV has been able to launch geosynchronous satellites, it has only been able to place very small satellites into fairly low transfer orbits, whereas the GSLV can launch larger payloads into more typical, higher, transfer orbits.

The maiden flight of the GSLV was conducted on 20 April 2001, carrying an experimental communications satellite named GramSat-1, or GSAT-1. The first two stages performed well, however the third stage underperformed leaving the payload in a lower orbit than had been planned.

Despite attempts to recover the satellite, using its own propulsion system to make up the shortfall, a design fault stemming from the satellite having been partially constructed from spare parts led to it running out of fuel short of geostationary orbit.

After the initial failure, the next flight in May 2003 fared better, placing GSAT-2 into its planned transfer orbit. Following this, the GSLV was declared operational, and its third flight successfully orbited GSAT-3, also known as HealthSat in September 2004.

The fourth GSLV, launched in July 2006, was expected to place the INSAT-4C communications satellite into orbit. Before the rocket even launched, a thrust regulator in one of the four booster rockets failed, resulting in that booster producing more thrust than it was designed to withstand, which caused the engine to fail less than a second after launch.

The rocket flew on for around a minute before disintegrating as is approached the area of maximum aerodynamic pressure.

A replacement for INSAT-4C, INSAT-4CR, was carried by the fifth GSLV, F04, which flew in September 2007. This launch also failed to reach its target orbit – suffering a similar shortfall to the GSAT-1 mission, however unlike GSAT-1; INSAT-4CR was able to correct its own orbit.

The GSLV Mk.II, which features a new upper stage with an Indian-built engine, made its first launch in April 2010 with the GSAT-4 satellite as its payload. While the first and second stages performed well, the new third stage engine failed 2.2 seconds after it ignited, and the rocket did not achieve orbit.

This failure has been attributed to a problem with the Fuel Boost Turbopump (FBTP), which appeared to lose speed a second after ignition. Following the failure, ISRO opted to conduct further tests on the new third stage, with two leftover GSLV Mk.Is flying in the interim.

The first of these rockets was launched on 25 December 2010 with GSAT-5P. Bound for geostationary transfer orbit, the rocket was destroyed by range safety 53 seconds after a loss of control.

An investigation determined that connectors in a Russian-built interstage adaptor had snapped, leaving the strap-on boosters uncontrollable, however Russian officials blamed a structural failure of the payload fairing.

It was later reported that problems with the connectors had occurred before – including one snapping during the launch of INSAT-4CR which was responsible for the underperformance of that launch.

Owing to the disagreement between India and Russia over the cause of the GSAT-5P failure, the final GSLV Mk.I has not yet flown. It is unclear whether it will ever be launched, or if ISRO will focus instead on the Mk.II. Because of these failures, currently the GSLV is statistically the least reliable rocket in service, with a success rate of 28.6%.

GSLV is a three-stage rocket, with four liquid-fuelled boosters augmenting the first stage. The first stage, or GS-1, is powered by an S-139 solid rocket motor, burning hydroxyl-terminated polybutadiene (HTPB) propellant. The stage can deliver up to 4,800 kilonewtons (1.1 million pounds) of thrust.

The four L40H boosters, which are powered by Vikas engines burning UH25 – a mixture of three parts unsymmetrical dimethylhydrazine and one part hydrazine hydrate, which is oxidized by dinitrogen tetroxide. The Vikas engine is derived from the French Viking engine, which was developed for the Ariane family of rockets. Each booster provides 680 kilonewtons, or 150,000 pounds-force of thrust.

The second stage, designated the GS-2 or L-37.5H, also uses a Vikas engine; delivering 720 kilonewtons (160,000 lbf) of thrust. The third stage, or GS-3, is a CUS-12 powered by the Indian Cryogenic Engine, or ICE. Burning liquid hydrogen propellant with liquid oxygen as an oxidiser, the ICE will deliver 75 kilonewtons (17,000 lbf) of thrust.

The launch began with the ignition of the four boosters, 4.8 seconds ahead of the planned liftoff time. The solid-fuelled core stage ignited at T-0 and burn for 100 seconds. Once it completed its burn, the first stage remained attached as the boosters burn for slightly longer than it does. Around 149 seconds after launch, the booster engines shut down, with the second stage igniting half a second later, and stage separation occurring two seconds after cutoff.

The second stage burned for 139.5 seconds. About 75 seconds into the burn, fairing separation occurred, with the shroud which protects GSAT-14 during its ascent through the atmosphere separating from the nose of the rocket. Once the second stage completes its firing, it coasted for three and a half seconds before separating.

The third stage ignited a second after staging, beginning a 12-minute, 1.5-second burn to reach the planned geosynchronous transfer orbit.

Spacecraft separation, which targeted an orbit of 180 by 35975 kilometers (112 by 22,354 statute miles, 97 by 19,425 nautical miles) with an inclination of 19.3 degrees, occurred 13 seconds after the end of the third stage burn – seventeen minutes and eight seconds after liftoff.

Allowable error margins for the launch are plus or minus 5 kilometers (3.1 mi, 2.7 nmi) in perigee altitude, 675 kilometers (420 mi, 365 nmi) apogee altitude, and a tenth of a degree inclination.

Compared to previous launches, GSLV D5 incorporates several modifications intended to increase its reliability.

The interstage between the second and third stages was redesigned to allow it to handle greater loads, while the tunnel containing electrical connections between the stages has also been made more durable. The FBTP has been modified to allow it to perform better at the low temperatures it is expected to operate under.

The flight’s aerodynamic profile and third stage ignition sequence were also adjusted. In addition, the rocket carried cameras for the first time, to record its operation.

GSAT-14 is a 1,982 kilogram (4,370 lb) satellite, which was constructed by ISRO and is based on the I-2K bus. It is equipped with six C and six Ku-band transponders, powered by twin solar arrays which generate up to 2,600 watts of power and charge lithium ion batteries. In addition to its communications payload, the satellite carries two Ka-band payloads which will be used for an investigation of how weather affects satellite communications.

GSAT-14 will be positioned at a longitude of 74 degrees east, and is expected to operate for at least 12 years. Most of its mass is fuel, much of which will be expended by maneuvers to raise itself from the initial transfer orbit into geostationary orbit. It has a dry mass of 851 kilograms (1,876 lb).

The Satish Dhawan Space Center, located in Sriharikota, India, has been the site of all of India’s orbital launches. Originally known as the Sriharikota High Altitude Range, or Sriharikota Range, it was named after ISRO’s second chairman, Satish Dhawan, following his death in 2002. The launch took place from the Second Launch Pad at the center.

The somewhat confusingly named Second Launch Pad (SLP) at the Satish Dhawan Space Centre is actually the fifth launch complex to be built at the site – following a sounding rocket complex to the north, disused SLV and ASLV complexes to the south, and the nearby First Launch Pad.

The GSLV can launch from either the First Launch Pad, which was built in the 1990s for the PSLV, or from the Second Launch Pad. Since the completion of the Second pad, all GSLV launches have used it. D5 is the fifth GSLV and twelfth rocket overall to fly from the Second Launch Pad.

The Second Launch Pad was constructed in the early 2000s, and first used for a PSLV launch in May 2005, with the CartoSat-1 satellite. Like the First Launch Pad both the PSLV and GSLV can launch from it.

Rockets are assembled vertically in an integration building some distance from the pad, and then moved to the launch pad atop a mobile platform running on rails.

(Images via ISRO).