ISRO's workhorse PSLV: A timeline of its launch and development

New Delhi, Feb 16: PSLV or Polar Satellite Launch Vehicle, many a times called as 'ISRO's workhorse', has launched most Indian satellites to space and has a great record at it. PSLV earned its title 'the Workhorse of ISRO' through consistently delivering various satellites to Low Earth Orbits, particularly the IRS series of satellites. It can take up to 1,750 kg of payload to Sun-Synchronous Polar Orbits of 600 km altitude.

PSLV is the third generation launch vehicle of India. It is the first Indian launch vehicle to be equipped with liquid stages. After its first successful launch in October 1994, PSLV emerged as the reliable and versatile workhorse launch vehicle of India with 39 consecutively successful missions by June 2017.

Timeline of PSLV's development:

• Studies to develop a vehicle capable of delivering 600 kg payload to 550 km Sun-synchronous orbit from SHAR began in 1978.

• By 1981, confidence grew in remote sensing spacecraft development with launch of Bhaskara-1 and the PSLV project objectives were upgraded to have vehicle deliver 1000 kg payload in 900 km SSO.

• Funding was approved in July 1982 for finalized design employing a single large S125 solid core as first stage with six 9 tonne strap-ons (S9) derived from 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 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 first stage.

• The inertial navigation systems are developed by ISRO Inertial Systems Unit (IISU) at Thiruvananthapuram.

• The liquid propulsion stages for the second and fourth stages of PSLV as well as the Reaction control systems (RCS) are developed by the Liquid Propulsion Systems Centre (LPSC) at Mahendragiri near Tirunelveli, Tamil Nadu.

• 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.

• During 1994-2017 period, the vehicle has launched 48 Indian satellites and 209 satellites for customers from abroad.

• Besides, the vehicle successfully launched two spacecraft - Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013 - that later travelled to Moon and Mars respectively.