Editing Delta II (section)

=== First stage ===
The first stage of the Delta II was propelled by a Rocketdyne [[RS-27]] or [[RS-27A]] main engine burning [[RP-1]] and [[liquid oxygen]]. This stage was technically referred to as the "Extra-Extended Long Tank Thor", a derivative of the [[PGM-17 Thor|Thor]] ballistic missile <ref>{{cite web |url=http://www.spacelaunchreport.com/thorh12.html |title=Space Launch Report |archive-url=https://web.archive.org/web/20120418063513/http://www.spacelaunchreport.com/thorh12.html |website=spacelaunchreport.com |archive-date=2012-04-18 |access-date=14 August 2024}}</ref> as were all Delta rockets until the [[Delta IV]]. The RS-27 used on the 6000-series Delta II produced {{cvt|915|kN|lbf}} of thrust,<ref>{{cite web |url=http://www.astronautix.com/r/rs-27.html |title=RS-27 |website=astronautix.com |access-date=14 August 2024}}</ref> while the upgraded RS-27A used by the 7000-series produced {{cvt|1054|kN|lbf}}.<ref>{{cite web |url=http://www.astronautix.com/engines/rs27a.htm |title=RS-27A |access-date=14 August 2024 |website=astronautix.com}}</ref> The stage was {{convert|26.1|m|ft|sp=us}} long and {{convert|2.44|m|ft|sp=us}} wide, had a mass of {{convert|101.8|t|lb}} when fueled, and burned for 260 seconds.<ref name="data sheet"/> The main engine, which could not throttle, provided pitch and yaw control for the vehicle during ascent using hydraulic gimballing. In addition, two [[Rocketdyne LR-101-NA-11]] vernier engines provided roll control for the first stage during ascent and continued firing after the main engine shut down to stabilize the vehicle before stage separation.<ref name="D2PG"/><ref name ="Guide"/>

The two first-stage tanks were constructed from aluminum isogrid panels, providing high strength at a lower mass. Nitrogen gas was used to pressurize the tanks. These tanks were stretched a total of {{convert|148|in|m}} from those of the Extended Long Tank Thor that flew on older Delta rockets, providing more propellant. Between the two tanks was the "center body", where first-stage avionics and communications equipment were housed. The solid rocket booster attachment points were located on the outside of the liquid oxygen tank and the aft skirt, the latter of which also contained a [[gyroscope]] for vehicle stability.<ref name ="Guide"/>