Geopolitical and economic considerations during the 1960s and 1970s compelled India to initiate its ownlaunch vehicle program.[11] During the first phase (1960s-1970s) the country successfully developed a sounding rockets program, and by the 1980s, research had yielded the Satellite Launch Vehicle-3 and the more advanced Augmented Satellite Launch Vehicle (ASLV), complete with operational supporting infrastructure.[11] ISRO further applied its energies to the advancement of launch vehicle technology resulting in the creation of Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV) technologies
SLV project was started in early seventies and was designed to put 40 Kg payload into a 400Km circular orbit. SLV3 rocket had four solid-propellant rocket motors, inter-stages connecting the forward skirt of one stage with the rear skirt of the next stage, inertial guidance and control systems to steer the vehicle along a predetermined trajectory and a heat shield to protect the fourth stage and the satellite payload[11].
The SLV project was lead by APJ Abdul Kalam[12] who also had the additional responsibility for designing the fourth stage of the SLV. He had Dr VR Gowariker who was the expert in the field of composite propellant.
The milestones consisted of :
- Development & qualification of all subsystems through sounding rockets by 1975
- Sub-orbital flight by 1976
- Final orbital flight in 1978
Wernher von Braun [13] during his visit to ISRO mentioned the American physiological complex of NIH (Not Invented Here) and said, "If you have to do anything in rocketry do it yourself", he commented, "SLV-3 is a genuine Indian design and you may be having your own troubles. But you should always remember that we do not just build on success, we also build on failure"[14].
ASLV - Augumented Satellite Launch Vehicle
The payload capability was thus raised to 150 Kg as compared to SLV-3's 42 Kg capability. Closed loop guidance, active from the ignition of the second stage motor to the separation of the third stage, was employed in ASLV while SLV-3 had used an open loop system.
First Launch Date: 24 March 1987. Last Launch Date: 04 May 1994. LEO Payload: 150 kg. to: 400 km Orbit. Liftoff Thrust: 92,780 kgf. Total Mass: 41,000 kg. Core Diameter: 1.0 m. Total Length: 23.5 m. Flyaway Unit Cost $: 9.00 million. in 1985 unit dollars.
PSLV - Polar Satellite Launch Vehicle
The Polar Space Launch Vehicle is a versatile heavy launcher developed to permit India to launch its own IRS-class 1600Kg satellites in sun-synchronous orbits, though it could also be used for GTO mission. It also served as the stepping-stone for GSLV heavy lift configuration for mainstream GTO orbit.
The basic PSLV configuration is 44.4 meter tall weighing 295 tonne and four stages using solid and liquid propulsion systems alternately.
Of the six strap-on motors (PSOM), depending on mission requirement first two or four of PSOM are ignited on the ground, to augment the first stage thrust. Each of these solid propellant strap-on motors carries nine tonne of HTPB based propellant, burn for 45 seconds and produces 662 kN thrust. The remaining strap-on motors are ignited 25 seconds (at ~3 Km altitude) after lift off.
GSLV (Geosynchronous Satellite Launch Vehicle)
The GSLV has four liquid propellant strap-on indigenous Vikas motors (L40) based on Ariane Viking-2 engine of SEP, which are ignited on the ground, to augment the first stage thrust.
GSLV will be declared operational after one more successful developmental flights (D3). GSLV-D1 successfully launched 1540Kg GSAT-1 satellite into GTO on 18-April-2001 and GSLV-D2 launched 1825Kg GSAT-2 to GTO on 8-May-2003 . Commercial flights C1, C2 & C3 is already budgeted, including long lead-time items for C4, C5 & C6 [43] .
Efforts are already on to improve the payload in GTO in progressive steps of 2,200Kg, 2,300 Kg and 2450Kg by 2006 [44]. Other than GTO missions, GSLV can also perform mission to LEO and polar missions.
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