Editing Geosynchronous Satellite Launch Vehicle (section)

== Variants ==
GSLV rockets using the Russian Cryogenic Stage (CS) are designated as the GSLV Mark I while versions using the indigenous Cryogenic Upper Stage (CUS) are designated the GSLV Mark II.<ref>{{Cite web|date=July 2003|title=Space India, April-June 2003|url=https://www.isro.gov.in/sites/default/files/flipping_book/51-SI-Apr-jun-2003/files/assets/common/downloads/Space%20India%20Apr-Jun%202003.pdf|url-status=live|archive-url=https://web.archive.org/web/20210816025908/https://www.isro.gov.in/sites/default/files/flipping_book/51-SI-Apr-jun-2003/files/assets/common/downloads/Space%20India%20Apr-Jun%202003.pdf|archive-date=16 August 2021|access-date=16 August 2021|page=11}}</ref><ref name=GSLVD3brochure>{{cite web|title=GSLV-D3/GSAT-4 Brochure|url=http://www.isro.org/gslv-d3/pdf/GSLV-D3_GSAT-4%20Brochure.pdf|publisher=ISRO|access-date=15 January 2014|url-status=dead|archive-url=https://web.archive.org/web/20140207165809/http://www.isro.org/gslv-d3/pdf/GSLV-D3_GSAT-4%20Brochure.pdf|archive-date=7 February 2014}}</ref> All GSLV launches have been conducted from the [[Satish Dhawan Space Centre]] in [[Sriharikota]].

=== GSLV Mark I ===
The first developmental flight of GSLV Mark I had a 129 tonne (S125) first stage and was capable of launching around 1500&nbsp;kg into [[geostationary transfer orbit]]. The second developmental flight replaced the S125 stage with S139. It used the same solid motor with 138 tonne propellant loading. The chamber pressure in all liquid engines were enhanced, enabling a higher propellant mass and burn time. These improvements allowed GSLV to carry an additional 300&nbsp;kg of payload.<ref name="cursci-25jul01">{{cite journal|author1=R. V. Perumal|author2=B. N. Suresh|author3=D. Narayana Moorthi|author4=G. Madhavan Nair |title=First developmental flight of geosynchronous satellite launch vehicle (GSLV-D1)|journal=Current Science|date=25 July 2001|volume=81|issue=2|pages=167–174 |url=http://www.iisc.ernet.in/currsci/jul252001/167.pdf|archive-url=https://web.archive.org/web/20160305012149/http://www.iisc.ernet.in/currsci/jul252001/167.pdf|archive-date=5 March 2016}}</ref><ref name="cursci-10sep03">{{cite journal|author1=R. V. Perumal|author2=D. Narayana Moorthi|author3=N. Vedachalam|author4=G. Madhavan Nair|title=Second developmental flight of Geosynchronous Satellite Launch Vehicle |journal=Current Science|date=10 September 2003|volume=85|issue=5|pages=597–601|url=http://www.iisc.ernet.in/~currsci/sep102003/597.pdf|archive-url=https://web.archive.org/web/20180216164833/http://www.iisc.ernet.in/~currsci/sep102003/597.pdf|archive-date=16 February 2018}}</ref> The fourth operational flight of GSLV Mark I, GSLV-F06, had a longer third stage called the C15 with 15 tonne propellant loading and also employed a {{No break|4 meter}} diameter payload fairing.<ref name=GSLVF06>{{cite web|title=GSLV-F06|url=http://www.isro.gov.in/gslv-f06/gslv-f06.aspx|publisher=ISRO|access-date=9 January 2014|url-status=dead |archive-url=https://web.archive.org/web/20130810005704/http://isro.gov.in/gslv-f06/gslv-f06.aspx|archive-date=August 10, 2013}}</ref><ref>{{Cite web|title=GSLV-F06 / GSAT-5P mission brochure|url=http://isro.gov.in/gslv-f06/pdf/GSLV-F06.pdf|url-status=live|archive-url=https://web.archive.org/web/20130909115830/http://isro.gov.in/gslv-f06/pdf/GSLV-F06.pdf|archive-date=9 September 2013}}</ref>

[[File:Launch of GSLV F11 GSAT-7A from Second Launch Pad of SDSC SHAR 01.jpg|thumb|upright=1.0|left|Launch of GSLV F11 [[GSAT-7A]] from Second Launch Pad of [[Satish Dhawan Space Centre]]]]

=== GSLV Mark II ===
This variant uses an Indian cryogenic engine, the CE-7.5, and is capable of launching 2500&nbsp;kg into geostationary transfer orbit. Previous GSLV vehicles (GSLV Mark I) have used Russian cryogenic engines.<ref>{{cite web|url=http://www.spaceflightnow.com/news/n1010/12gslv/|title=India may seek international help on cryogenic engine|last=Clark|first=Stephen|date=2010-10-12|quote=Besides the new upper stage, the GSLV Mk.2 launched in April was nearly identical to previous versions of the booster|publisher=Spaceflight Now|access-date=15 July 2011}}</ref>

For launches from 2018, a 6% increased thrust version of the Vikas engine was developed. It was demonstrated on 29 March 2018 in the [[GSAT-6A]] launch second stage. It was used for the four Vikas engines first stage boosters on future missions.<ref name=sfn-20180329>{{cite news|url=https://spaceflightnow.com/2018/03/29/india-tests-upgraded-engine-tech-in-successful-communications-satellite-launch/|title=India tests upgraded engine tech in successful communications satellite launch|last=Clark|first=Stephen|publisher=Spaceflight Now|date=29 March 2018|access-date=30 March 2018}}</ref>

A 4m diameter Ogive payload fairing was developed and deployed for the first time in the [[GEO Imaging Satellite|EOS-03]] launch on 12 August 2021, although this launch was a failure due to technical anomalies with the Cryogenic Upper Stage. This will allow GSLV vehicles to accommodate larger payloads.<ref>{{Cite web|title=GSLV-F10/EOS-03 Brochure|url=https://www.isro.gov.in/gslv-f10-eos-03/gslv-f10-eos-03-brochure|access-date=14 August 2021|website=ISRO}}</ref>

As of October 2024, ISRO has stopped selling GSLV Mk II Rockets. Eight known launches are planned with [[IRNSS|NVS]] Missions, [[Indian Data Relay Satellite System|IDRSS]] Missions, [[NISAR]] Mission, etc.<ref>{{cite web |url=https://x.com/ISROSpaceflight/status/1844724481958334841?t=La5vxZzAvABlXsIcGCoHRQ&s=08 |title=ISRO has stopped selling GSLV Mk II Rockets |work=X (Formerly Twitter) |access-date=11 October 2024}}</ref><ref>{{Cite web |title=Why ISRO chose GSLV for NISAR mission despite the launch vehicle's poor track record? |url=https://www.theweek.in/news/sci-tech/2025/05/20/why-isro-chose-gslv-for-nisar-mission-despite-the-launch-vehicles-poor-track-record.html |access-date=2025-05-27 |website=The Week |language=en}}</ref>

=== RLV-OREX ===
The [[RLV Technology Demonstration Programme|Reusable Launch Vehicle Technology Demonstration program]], is a prototype [[spaceplane]] concept created by ISRO. For the Orbital return Flight experiment, a modified version of the GSLV Mk. II launcher, with the upper Cryogenic Stage replaced with the PS-4 stage from the PSLV is currently in development, as the RLV won't need all the excess energy produced by the CUS .<ref>{{Cite web |title=MSN |url=https://www.msn.com/en-in/news/other/rlv-re-entry-mission-to-use-gslv-with-pslv-last-stage-landing-gear-to-change-more/ar-BB1oSNaF |access-date=2024-06-26 |website=www.msn.com}}</ref><ref>{{Cite news |title=RLV re-entry mission to use GSLV with PSLV last stage; landing gear to change & more |url=https://timesofindia.indiatimes.com/india/rlv-re-entry-mission-to-use-gslv-with-pslv-last-stage-landing-gear-to-change-more/articleshow/111267553.cms |access-date=2024-06-26 |work=The Times of India |issn=0971-8257}}</ref>