Editing Delta II (section)

=== Third stage ===
For low Earth orbit missions, Delta II was not equipped with a third stage. Payloads bound for higher energy orbits such as [[geostationary transfer orbit|GTO]] or to reach Earth escape velocity for [[trans-Mars injection]] or other destinations beyond Earth used an [[HTPB]] solid propellant third stage, situated inside the fairing during launch. This stage was [[spin-stabilized]] and depended on the second stage for proper orientation prior to stage separation, but was sometimes equipped with a hydrazine nutation control system to maintain proper spin axis.<ref name="D2PG"/> The third stage would be spun up using small rocket motors and then released by the second stage to perform its burn. The third stage also included a yo-weight system to induce tumbling in the stage after payload separation to prevent recontact, or a [[yo-yo de-spin]] mechanism to slow the rotation before payload release.<ref name="D2PG">{{cite web |title=Delta II Payload Planner's Guide 2007 |url=http://www.ulalaunch.com/uploads/docs/DeltaIIPayloadPlannersGuide2007.pdf |website=ulalaunch.com |access-date=24 July 2014 |archive-url=https://web.archive.org/web/20110919175556/http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIIPayloadPlannersGuide2007.pdf |archive-date=19 September 2011 |url-status=live}}</ref> The stage would also contain an S-band transmitter, batteries, and a sequencer to command the stage events.

Two third-stage options were available, both consisting of a single solid rocket motor. The most common by far was [[Star 48]], flying on over 70 missions. The Star 48, also referred to as the Payload Assist Module-Delta (PAM-D, PAM-Delta), was the more, powerful of the two options, producing an average thrust of about {{cvt|66.4|kN}} during its 87.1 seconds of burn time. The stage would end up flying primarily on the more powerful Delta variants and never flew on the three-booster configuration.

The other third-stage option was [[Star 37FM]]. This stage flew four times, and only on three- and four-booster configurations of Delta. Star 37FM produced about {{cvt|45.8|kN}} of thrust during its 66.4-second burn.<ref name ="Guide"/>