The launcher & propulsion represents the ISRO's largest single development area. The launcher program has seen a gradual evolution (from the all-solid SLV-3 to solid, liquid and cryogenic fuelled stages currently used in PSLV series (Delta class launcher) and GSLV (Ariane-class)

Satellite Launch Vehicle (SLV) - An all solid four stage satellite launch vehicle built as a proof of launch capabilities. Its payloads were mainly the Rohini Satellites.

• Satellite Launch Vehicle (SLV) : 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. The SLV project was lead by APJ Abdul Kalam  who also had the additional responsibility for designing the fourth stage of the SLV.
• Augmented Satellite Launch Vehicle(ASLV) - Keeping in view the long-term goal for realizing polar and geo-synchronous launch capability for operational class of satellites, development of Augmented Satellite Launch Vehicle (ASLV), was undertaken to act as a low cost intermediate vehicle for demonstrating critical technologies. ASLV was configured as a five-stage solid propellant vehicle, weighing about 40 tonne and having a length of about 23.8 m. The strap-on stage consisted of two identical 1 m diameter solid propellant motors similar to SLV-3 first stage, other stages being the same as in SLV-3. The payload capability was thus raised to 150 Kg as compared to SLV-3's 42 Kg capability. Its payloads mainly included Stretched Rohini Satellite Series (SROSS) satellites.
• Polar Satellite Launch Vehicle (PSLV) - a five stage booster with liquid and solid stages. The main stage is one of the largest solid rocket boosters in the world. The PLSV can place 1200 kg into Polar Sun Synchronous Orbit (SSO). After the initial breakthrough of sending a small satellite launch vehicle called simply SLV3 in 1980, the ISRO experienced a string of failures while trying to augment the nation’s rocket capability. It was not till the early 1990s and that too after the first failed launch of PSLV that ISRO recov­ered and notched up a string of successes on. On15 October 1994, the organisation mastered the technology of building a launcher that could eject a one-tonne satellite into an orbit around the poles at an altitude of 800 km, called the Polar Satellite Launch Vehicle (PSLV).It was important for sending up remote sensing satellites. The first commercial launch of the PSLV, which took off from Sriharikota on 26 May 1999, carried an Indian remote sensing satellite Oceansat, and a Korean and a German Satellite. For the first time an Indian launch vehicle had been used to launch satellites of other countries. With Indian costs being much lower than those charged by the Russian, European and American space agencies, Indian launch facilities could become attractive, especially for launching satellites of Third world countries.
• Geosynchronous Satellite Launch Vehicle (GSLV) - a three stage booster with liquid and solid stages. The GSLV can place 2000 kg into Geo-synchronous Transfer Orbit (GTO). On April 18, 2001 India joined exclusive club of space powers that have as its members only Russia, US. China, Japan and a consortium of European nations led by France by successfully launching Geostationary Satellite Launch Vehicle (GSLV) which has the capability to launch communication satellites into the geos­tationary transfer orbit. The launch vehicle has been officially named as GSLV-D1. The Indigenous Cryogenic Upper Stage was successfully flight-tested onboard GSLV-D5 launch vehicle on January 05, 2014 from Satish Dhawan Space Centre SHAR, Sriharikota. In this successful flight of GSLV-D5, a communication satellite - GSAT-14 - was launched very precisely to its intended Geosynchronous Transfer Orbit.

India is also developing following space launch vehicles: GSLV Mk-I, GSLV Mk-II, GSLV Mk-III

GSLV -Features

• GSLV is the most powerful rocket designed and built by India’s space scientists so far and is capable of lifting a 2,500-kg INSAT class satellite into the geosynchronous transfer orbit.
• The GSLV, an acronym for Geostationary Satellite Launch Vehicle, is a giant rocket, standing almost 50 metres tall, with a lift-off weight of more than 400 tonnes. It is a three-stage rocket.
• The first stage is a 129-tonne solid propellant core motor with four liquid propellant strap-on engines, each carrying 40 tonnes of propellant.
• The second stage is a liquid propulsion system with 37.5 tonnes of propellant.
• The third stage has a propellant loading of 12 tonnes in the form of liquid oxygen and liquid hydrogen. 
• On its maiden flight, the GSLV will place an experimental communication satellite ‘G-Sat’ in the geosynchronous transfer orbit (GTO). From the GTO, the satellite will be moved to the geostationary orbit, 36,000 kilometers above the equator by controlled firings of its apogee boost motor.
• GSLV is the culmination of more than two decades of work by scientists and technologists of the Indian Space Research Organi­sation (ISRO) in developing rockets for launching satellites. Today all the Indian satellite launch vehicles are fabricated at the Vikram Sarabhai Space Centre in Thiruvananthapuram.

Benefits for India

• With GSLV, the country would not only be able to save an average Rs. 100 crore on every INSAT launch
• Also the country will compete for a share in the $10 billion (Rs. 47,000 crore) global communications space business. The cost factor is certainly a plus for India because its launches are on average cheaper by 15 per cent than comparable Western launchers. The world market for communications launchers is dominated by Ariane which accounts for close to 60 per cent of the total launches annually.

India's first reusable Space Shuttle- RLV-TD

ISRO successfully test launched the first indigenous Reusable Launch Vehicle-Technology Demonstrator (RLV-TD). It was launched from first launch pad at Satish Dhawan Space Centre, Sriharikota in Andhra Pradesh. It was a part of a series of Technology Demonstration Missions, which is considered as first step towards realising a Two Stage To Orbit (TSTO) fully reusable vehicle.

Some Salient features of RLV-TD:

1) RLV-TD is a 6.5m long and has an aero plane like structure. It weighs about 1/75 tonnes and is very similar to the retired US Space Shuttle.

2) It has been built by a team of scientists over five years at Vikram Sarabhai Space Centre in Thiruvananthapuram. 

3) RLV-TD is a winged body aerospace vehicle that operated in hypersonic flight regime. It is capable of launching satellites into orbit around Earth and then re-enter the atmosphere.

4) It has been configured to act as a flying test bed to evaluate various technologies, including hypersonic flight, automatic landing and powered cruise flight

5) It was launched using a 9 ton Solid Rocket Motor (SRM) which is designed to burn slowly to accommodate the vertical lifting of winged body.  

Significance of the Demonstration:

1) RLV is the unanimous solution to achieve low cost, reliable and on—demand space access. Scientists at ISRO believe that they could reduce the cost by as much as 10 times if reusable technology succeeds, bringing it down to $2,000 per kg from the present $20,000 per kg.

2) This flight will test the capability of the vehicle to survive a re-entry at speeds higher than that of sound.

3) The solution to reducing cost of launching satellites into orbit is to recycle the rocket or make it reusable.

Cryogenics

Cryogenics, study and use of materials at very low temperatures. The upper limit of cryogenic temperatures has not been agreed on, but the National Bureau of Standards has suggested that the term cryogenics be applied to all temperatures below -150° C (-238° F or 123° above absolute zero on the Kelvin scale). Some scientists regard the normal boiling point of oxygen (-183° C or -297° F), as the upper limit.

Applications

• Among the many important industrial applications of cryogenics are the large-scale production of oxygen and nitrogen from air. The oxygen can be used in a variety of ways, for example, in rocket engines, for cutting and welding torches etc. The nitrogen goes into the making of ammonia for fertilizers.
• Cryogenics has also made possible the commercial transportation of liquefied natural gas.
• Without cryogenics, nuclear research would lack liquid hydrogen and helium for use in particle detectors and for the powerful electromagnets needed in large particle accelerators.
• Such magnets are also being used in nuclear fusion research. Infrared devices, masers, and lasers can employ cryogenic temperatures as well.
• Cryogenic surgery, or cryosurgery, is being used for the treatment of Parkinson’s disease, the technique being based on the selective destruction of tissue by freezing it with a small cryogenic probe. A similar technique has also been employed to destroy brain tumors and to arrest cervical cancer.
• A cryogenic engine is a liquid propellant rocket motor which uses liquid oxygen and liquid hydrogen as propellants. It is an essential part of any rocket used to launch geostationary satellites. Indian scientists have already developed a prototype of a small cryogenic engine.
• For GSLV, ISRO had to master the ultra-sophisticated cryogenic fuel technology. In 1992, Russia agreed to sell a few engines and transfer the technology.
• But the US, worried that the cryogenic engine would equip India with Inter-Continental Ballistic Missile (ICBM) technology, stopped saying the deal violated the Missile Technology Controls Regime (JMTCR) to which Russia was a signatory.
• Russia reneged on the deal and agreed to supply India only seven such cryogenic engines for future launches and refused to transfer the technology.