Editing Polar Satellite Launch Vehicle (section)

=== First stage (PS1) ===
[[File:PSLV-C44 Integrated upto First Stage inside Mobile Service Tower.jpg|thumb|left|375x375px|[[PSLV-C44]] first stage inside Mobile Service Tower]]

The first stage, one of the largest [[solid rocket boosters]] in the world, carries {{cvt|138|MT}} of [[hydroxyl-terminated polybutadiene]]-bound (HTPB) propellant and develops a maximum thrust of about {{cvt|4800|kN}}. The {{cvt|2.8|m}} diameter motor case is made of [[maraging steel]] and has an empty mass of {{cvt|30200|kg}}.<ref name="sf101">{{cite web|url=http://www.spaceflight101.com/pslv-launch-vehicle-information.html|title=PSLV Launch Vehicle Information|publisher=Spaceflight 101|access-date=February 20, 2015|archive-url=https://web.archive.org/web/20150924115759/http://www.spaceflight101.com/pslv-launch-vehicle-information.html|archive-date=24 September 2015|url-status=dead}}</ref>

[[Aircraft principal axes|Pitch]] and [[Yaw (rotation)|yaw]] control during first stage flight is provided by the Secondary Injection Thrust Vector Control (SITVC) System, which injects an [[aqueous solution]] of [[strontium perchlorate]] into the [[S139 Booster|S139]] exhaust divergent from a ring of 24 injection ports to produce asymmetric thrust. The solution is stored in two cylindrical [[aluminium]] tanks strapped to the core solid rocket motor and pressurised with [[nitrogen]]. Underneath these two SITVC tanks, [[Roll program|Roll]] Control Thruster (RCT) modules with small bi-propellant (MMH/MON) liquid engine are also attached.<ref name=":4">{{Cite web|date=10 October 1993|title=Current Science (Volume 65 - Issue 07) PSLV-D1|url=https://www.currentscience.ac.in/Downloads/article_id_065_07_0522_0528_0.pdf|url-status=live|archive-url=https://web.archive.org/web/20200806072408/https://www.currentscience.ac.in/Downloads/article_id_065_07_0522_0528_0.pdf|archive-date=6 August 2020|access-date=20 December 2019}}</ref>

On the PSLV-G and PSLV-XL, first stage thrust is augmented by six [[strap-on booster|strap-on solid boosters]]. Four boosters are ground-lit and the remaining two ignite 25 seconds after launch. The solid boosters carry {{cvt|9|MT}} or {{cvt|12|MT}} (for PSLV-XL configuration) propellant and produce {{cvt|510|kN}} and {{cvt|719|kN}} thrust respectively. Two strap-on boosters are equipped with SITVC for additional attitude control.<ref name="sf101"/> The PSLV-CA uses no strap-on boosters.

First stage separation is aided by four pairs of retro-rockets installed on inter-stage (1/2L). During staging, these eight rockets help push away the spent stage away from second stage.<ref name=":5">{{cite web|url=https://www.isro.gov.in/sites/default/files/flipping_book/PSLV-C1/files/assets/basic-html/page-3.html|title=PSLV-C1|website=isro.gov.in|access-date=22 February 2020|archive-date=6 August 2020|archive-url=https://web.archive.org/web/20200806063834/https://www.isro.gov.in/sites/default/files/flipping_book/PSLV-C1/files/assets/basic-html/page-3.html|url-status=live}}</ref>