Polar Satellite Launch Vehicle

The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by ISRO. It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites into Sun-synchronous orbits, a service that was, until the advent of the PSLV in 1993, only commercially available from Russia. PSLV can also launch small size satellites into Geostationary Transfer Orbit (GTO).

Some notable payloads launched by PSLV include India's first lunar probe Chandrayaan-1, India's first interplanetary mission, Mars Orbiter Mission (Mangalyaan), India's first space observatory, Astrosat and India's first Solar mission, Aditya-L1.

PSLV has gained credibility as a leading provider of rideshare services for small satellites, owing to its numerous multi-satellite deployment campaigns with auxiliary payloads, usually ride-sharing along with an Indian primary payload. As of June 2022, PSLV has launched 345 foreign satellites from 36 countries. Most notable among these was the launch of PSLV-C37 on 15 February 2017, successfully deploying 104 satellites in Sun-synchronous orbit, tripling the previous record held by Russia for the highest number of satellites sent to space on a single launch, until 24 January 2021, when SpaceX launched the Transporter-1 mission on a Falcon 9 rocket carrying 143 satellites into orbit.

Payloads can be integrated in tandem configuration employing a Dual Launch Adapter. Smaller payloads are also placed on equipment deck and customized payload adapters.

Studies by the PSLV Planning group under S Srinivasan to develop a vehicle capable of delivering a 600 kg payload to a 550 km sun-synchronous orbit from SHAR began in 1978. Among 35 proposed configurations, four were picked; by November 1980, a vehicle configuration with two strap-ons on a core booster (S80) with 80 tonne solid propellant loading each, a liquid stage with 30 tonne propellant load (L30), and an upper stage called the Perigee-Apogee System (PAS) was being considered.

By 1981, confidence grew in remote sensing spacecraft development with the launch of Bhaskara-1, and the PSLV project objectives were upgraded to have the vehicle deliver a 1000 kg payload into a 900 km SSO. As technology transfer of Viking rocket engine firmed up, a new lighter configuration with the inclusion of a liquid powered stage was selected. Funding was approved in July 1982 for the finalized design, employing a single large S125 solid core as first stage with six 9 tonne strap-ons (S9) derived from the SLV-3 first stage, liquid fueled second stage (L33), and two solid upper stages (S7 and S2.) This configuration needed further improvement to meet the orbital injection accuracy requirements of IRS satellites, and hence, the solid terminal stage (S2) was replaced with a pressure fed liquid fueled stage (L1.8 or LUS) powered by twin engines derived from roll control engines of the first stage. Apart from increasing precision, liquid upper stage also absorbed any deviation in performance of solid third stage. The final configuration of PSLV-D1 to fly in 1993 was (6 × S9 + S125) + L37.5 + S7 + L2.

The inertial navigation systems are developed by ISRO Inertial Systems Unit (IISU) at Thiruvananthapuram. The liquid propulsion for the second and fourth stages of the PSLV as well as the Reaction control systems (RCS) are developed by the Liquid Propulsion Systems Centre (LPSC) at Valiamala near Thiruvananthapuram, kerala. The solid propellant motors are processed at Satish Dhawan Space Centre (SHAR) at Sriharikota, Andhra Pradesh, which also carries out launch operations. The aerodynamic characterization research was conducted at the National Aerospace Laboratories' 1.2m Trisonic Wind Tunnel Facility.

The PSLV was first launched on 20 September 1993. The first and second stages performed as expected, but an attitude control problem led to the collision of the second and third stages at separation, and the payload failed to reach orbit. After this initial setback, the PSLV successfully completed its second mission in 1994. The fourth launch of PSLV suffered a partial failure in 1997, leaving its payload in a lower than planned orbit. In November 2014, the PSLV had launched 34 times with no further failures. (Although launch 41: August 2017 PSLV-C39 was unsuccessful.)