Editing Liquid rocket booster (section)

==Current usage==
The [[Delta IV Heavy]] consists of a central [[Common Booster Core]] (CBC), with two additional CBCs as LRBs instead of the [[Graphite-Epoxy Motor|GEM-60]] [[solid rocket motor]]s used by the Delta IV Medium+ versions. At lift off, all three cores operate at full thrust, and 44 seconds later the center core throttles down to 55% to conserve fuel until booster separation.<ref name=d4ppg>{{cite web|title=Delta IV Payload Planner's Guide, June 2013|url=http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf|website=United Launch Alliance|accessdate=July 26, 2014|archive-url=https://web.archive.org/web/20140710005717/http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf|archive-date=July 10, 2014|url-status=dead}}</ref> The [[Angara (rocket family)#Angara A5|Angara A5V]] and [[Falcon Heavy]] are conceptually similar to Delta IV Heavy.<ref name="Capabilities & Services">{{cite web |url=http://www.spacex.com/about/capabilities |title=Capabilities & Services |author= |date=2012-11-28 |publisher=SpaceX |access-date=August 21, 2017 |archive-url=https://web.archive.org/web/20131007205105/http://www.spacex.com/about/capabilities |archive-date=October 7, 2013 |url-status=live }}</ref> The Indian [[Geosynchronous Satellite Launch Vehicle|GSLV]] also uses Four [[Geosynchronous Satellite Launch Vehicle#Liquid boosters|L40]] boosters that are attached to the [[S139 Booster|S139 stage]].<ref>{{Cite web |title=Indian Space Research Organisation |url=https://www.isro.gov.in/GSLV_CON.html |access-date=2025-02-09 |website=www.isro.gov.in}}</ref>

The Falcon Heavy was originally designed with a unique "propellant crossfeed" capability, whereby the center core engines would be supplied with fuel and oxidizer from the two side cores until their [[separation event|separation]].<ref name="nss201111">{{cite web |last=Strickland |first=John K. Jr. |title=The SpaceX Falcon Heavy Booster |date=September 2011 |url=http://www.nss.org/articles/falconheavy.html |publisher=National Space Society |access-date=November 24, 2012 |archive-url=https://web.archive.org/web/20130117112834/http://www.nss.org/articles/falconheavy.html |archive-date=January 17, 2013 |url-status=live }}</ref> Operating all engines at full thrust from launch, with fuel supplied mainly from the side boosters, would deplete the side boosters sooner, allowing their earlier separation to reduce the mass being accelerated. This would leave most of the center core propellant available after booster separation.<ref name="prop_cross">{{cite web |url=http://www.spaceref.com/news/viewpr.html?pid=33185 |title=SpaceX Announces Launch Date for the World's Most Powerful Rocket |publisher=SpaceX |date=April 5, 2011 |access-date=April 5, 2011 |archive-date=March 19, 2023 |archive-url=https://web.archive.org/web/20230319120607/https://spaceref.com/press-release/spacex-announces-launch-date-for-the-worlds-most-powerful-rocket/ |url-status=dead }}</ref> Musk stated in 2016 that crossfeed would not be implemented.<ref>{{cite tweet |user=elonmusk |author-link=Elon Musk |number=726561442636263425 |title="Does FH expendable performance include crossfeed?" "No cross feed. It would help performance, but is not needed for these numbers." |date=May 1, 2016 |access-date=June 24, 2017}}</ref> Instead, the center booster throttles down shortly after liftoff to conserve fuel, and resumes full thrust after the side boosters have separated.<ref name="sxfh">{{cite web |title=Falcon Heavy |url=http://www.spacex.com/falcon-heavy |publisher=SpaceX |access-date=April 5, 2017 |date=2012-11-16 |archive-url=https://web.archive.org/web/20170406182002/http://www.spacex.com/falcon-heavy |archive-date=April 6, 2017 |url-status=live }}</ref>