Common Booster Core

{{Short description|American rocket stage}}

{{About|the Delta IV first stage|the Atlas V booster|Common Core Booster}}

{{Infobox rocket stage

|name = Common Booster Core

|image = Delta 342 CBC delivery.jpg

|caption = Delivery of the CBC used as the first stage of Delta 342, which launched GOES 14

|manufacturer = Boeing (1998–2006)
United Launch Alliance (2006—2023)

|country = United States

|rockets = Delta IV (stage 1)
Delta IV Heavy (boosters)

|height = {{convert|40.8|m|abbr=on}}

|diameter = {{convert|5.1|m|abbr=on}}

|mass = {{convert|226400|kg|abbr=on}}

| stagedata =

{{Infobox rocket/stage

| name = Delta IV CBC

| engines = 1x RS-68

| thrust = {{convert|3312.76|kN|abbr=on}}

| burntime = 367 s

| fuel = LOX/LH₂

}}

|status=Retired|launches=45}}

Image:Two Boeing Delta IV first stages on the Launch Complex 37, Cap Canaveral Air Force Station, August 2004.jpg at SLC-37.]]

The Common Booster Core (CBC) was an American rocket stage, which was used on the Delta IV rocket as part of a modular rocket system. Delta IV rockets flying in the Medium and Medium+ configurations each used a single Common Booster Core as their first stage, while the Heavy configuration used three; one as the first stage and two as boosters.{{cite web|url=http://www.nasa.gov/mission_pages/launch/delta_IV_count_101.html|title=Countdown 101: Delta IV|publisher=NASA|accessdate=10 September 2010|archive-date=23 October 2010|archive-url=https://web.archive.org/web/20101023200917/http://www.nasa.gov/mission_pages/launch/delta_IV_count_101.html|url-status=dead}} The Common Booster Core was {{convert|40.8|m}} long, had a diameter of {{convert|5.1|m}} and was powered by a single RS-68 engine burning liquid hydrogen and liquid oxygen.{{cite web|url=http://www.astronautix.com/stages/delars68.htm|title=Delta RS-68|last=Wade|first=Mark|publisher=Encyclopedia Astronautica|accessdate=10 September 2010|url-status=dead|archiveurl=https://web.archive.org/web/20100511220011/http://www.astronautix.com/stages/delars68.htm|archivedate=11 May 2010}}

The first static test-firing of a Common Booster Core was conducted on 17 March 2001, and the final test of the initial program was conducted on 6 May.{{cite web|url=http://www.space.com/missionlaunches/launches/delta4_010509.html|title=Delta 4 Core Booster Rocket Engine Completes Test Program|date=9 May 2001|publisher=Space.com|accessdate=10 September 2010|url-status=dead|archiveurl=https://web.archive.org/web/20090629192958/http://www.space.com/missionlaunches/launches/delta4_010509.html|archivedate=29 June 2009}} Testing was conducted using Test Stand B-2 of the Stennis Space Center,{{cite web|url=http://www.spaceref.com/news/viewpr.html?pid=9691|archive-url=https://archive.today/20120910010027/http://www.spaceref.com/news/viewpr.html?pid=9691|url-status=dead|archive-date=September 10, 2012|title=Stennis Space Center Tours and Briefings on Boeing Rocketdyne's RS-68 engine for the Delta IV|date=30 October 2002|publisher=SpaceRef|accessdate=10 September 2010}} a facility originally constructed for testing of the first stages of Saturn V rockets during the 1960s. The first launch of a Common Booster Core was the maiden flight of the Delta IV, which was launched from Space Launch Complex 37B at the Cape Canaveral Space Force Station on 20 November 2002.{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|last=McDowell|first=Jonathan|publisher=Jonathan's Space Page|accessdate=10 September 2010}}

The first flight of the Delta IV Heavy, featuring three Common Booster Cores, was conducted on 21 December 2004. On this flight all three CBCs malfunctioned, cutting off prematurely due to cavitation in their oxidizer lines, and resulting in the rocket reaching a lower orbit than that which had been planned. In response to the failure, additional pressure valves were installed on future launches.{{cite web|url=http://www.spaceflightnow.com/delta/d310/050410briefing.html|title=Fixes ordered across Boeing's Delta 4 rocket line|last=Ray|first=Justin|date=10 April 2005|work=Delta Launch Report|publisher=Spaceflight Now|accessdate=10 September 2010}}

The Delta IV made 45 flights; 29 in Medium and Medium+ configurations, and 16 in the Heavy configuration, resulting in a total of 77 Common Booster Cores being launched.{{cite web|url=http://www.spacelaunchreport.com/delta4.html#delta4log|title=Delta IV Launch Record|last=Kyle|first=Ed|publisher=Space Launch Report|accessdate=21 January 2023|url-status=usurped|archive-url=https://web.archive.org/web/20220425022016/http://www.spacelaunchreport.com/delta4.html|archive-date=25 April 2022}}{{cite web |last=Graham |first=William |url=https://www.nasaspaceflight.com/2022/09/delta-iv-nrol-91/ |title=Last West Coast Delta IV Heavy launches with NROL-91 |date=24 September 2022 |access-date=25 September 2022 |work=NASASpaceFlight}} Delta IV retired on April 24 2024.

The CBCs were manufactured in United Launch Alliance's {{convert|1500000|ft2|adj=on}} manufacturing facility in Decatur, Alabama and then transported by the RS RocketShip to either Vandenberg Air Force Base or Cape Canaveral Air Force Station where they were integrated with the spacecraft and other components such as strap-on boosters and a Delta Cryogenic Second Stage.[http://www.boeing.com/companyoffices/gallery/images/space/delta_iv/d4_decatur_04.html Boeing: Multimedia - Image Gallery - Delta IV Launch Vehicle Manufacturing - Decatur, Alabama] {{webarchive|url=https://web.archive.org/web/20070203172623/http://www.boeing.com/companyoffices/gallery/images/space/delta_iv/d4_decatur_04.html |date=2007-02-03 }}