Augmented Satellite Launch Vehicle (ASLV):
SLV-3 is India’s first satellite launch vehicle and was used to place a 35kg. RS-I (Rohini) satellite into a low earth orbit in July 1980. ASLV or Augmented Satellite Launch Vehicle is, an augmented version of SLV-3 with two strap-on boosters designed to augment indigenous satellite launch capabilities to place a 150kg satellite (SROSS) into a 100 km. low earth orbit.
New technologies such as strap on booster motors, bulbous heat shield, close loop guidance system, vertical integration of launch vehicle, S-bandTTC systems have been employed in ASLV. There are plans of five stage rockets of ASLV using solid propellant in all to them. The first ASLV Development Launch (ASLV-D1) was carried out on March 24, 1987.
After a smooth lift off, the launch vehicle had a malfunction in its first stage and could not put the SROSS-1 satellite into orbit. The second developmental lauch was carried out on July 13, 1988 after getting experience from the first flight. Though the lift off of ASLV-D2 was smooth, but it failed soon after 46 seconds of its take off. Excessive load build-up was the main reason.
At last, victory came, when ASLV-D-3, the third development flight of Augmented Satellite Launch Vehicle series was successfully launched to orbit a 106 kg SROSS satellite on May 20, 1992 incorporating necessary modifications based on the data of earlier two flights. Thus, India achieved maturation and self-reliance in launch vehicle technology.
Polar Satellite Launch Vehicle (PSLV):
For launching IRS class of remote sensing satellites, ISRO indigenously started designing and developing Polar Satellite Launch Vehicle (PSLV) to place a 1,000 kg. Satellite in a 900 km. near polar sun synchronous orbit. PSLV is of five stages and includes both solid and liquid propulsion stages to generate the required thrust and control capabilities to precisely orbit the 1999 kg class operational remote sensing satellites into 1000 km observation altitudes.
The first stage has a diameter of 2.8m and carries 125 tonnes of solid propellant. It has six-trap on boosters derived from the SLV-3 first stage. The second stage is a liquid engine using 37.5 tonnes of liquid propellants. The third stage uses solid propellant and the fourth stage uses two liquid engines. Valiamala is the main centre for developing and testing PSLV elements whereas liquid engine tests are to be done at newly established Mahendragiri. The first developed PSLV rocket weighing 275 tones involving both liquid and solid propulsion systems is launched successfully in 1994 carrying IRS-P2 satellite on board.
Geo-Synchronous Satellite Launch Vehicle (GSLV):
The development of Geo-Synchronous Satellite Launch Vehicle (GSLV), maximum utilizing the proven modules of PSLV along the incorporating cryogenic rocket technology for launching of 2,500 kg
INSAT class of satellites into geo-stationary orbit was initiated in 1990. At present it is making rapid progress and its first launch scheduled was in 1996. Initial GSLV Launches were using cryogenic engines supplied by Russia. Now, it is trying to be self-reliant by building total indigenously developed cryogenic engines beyond 1999.