On the 31st of July 2023, United Launch Alliance delivered the Artemis 3 Interim Cryogenic Propulsion Stage, also called ICPS, to its Rocket Ship. Aboard this ship, the final Interim Cryogenic Propulsion Stage will head to Cape Canaveral, Florida, and wait to be attached to the final Space Launch System, SLS, Block 1 core stage. As part of the Artemis 3 Space Launch System, this will be the last Delta-derived stage to fly.
What is the Interim Cryogenic Propulsion Stage?
The Interim Cryogenic Propulsion Stage is built by United Launch Alliance and is derived from the Delta Cryogenic Second Stage. The Stage is a modified 5-meter Delta Cryogenic Second Stage that has lengthened the liquid hydrogen tank, added hydrazine bottles for attitude control, minor avionics changes, and a modified liquid hydrogen vent and relief valve that supports RL10 in-flight engine restart. The Stage is powered by one Aerojet Rocketdyne RL10 engine and generates 11 tons of thrust burning liquid hydrogen and liquid oxygen.
What is the history of Delta?
The original Delta rocket started out as a modified PGM-17 Thor ballistic missile with a variety of different upper stages until it was commonly used with the Thor upper stage. With Thor, it was commonly called 'Thor-Delta' until it eventually was shortened to just 'Delta'. 'Thor-Delta' first flew on the 13th of May 1960.
The second Delta rocket was called Delta II and began design after President Ronald Reagan changed course for future rocket launches after the Challenger Disaster. Delta II first flew in 1989 and was last launched in 2018 for a total of one-hundred and fifty-five flights with only two failures.
The third Delta rocket was Delta III which began design in 1995 as a larger and more powerful rocket than Delta II. Delta III flew from 1998 to 2000 and flew three times with no successful launches.
The fourth Delta rocket was Delta IV and is the final Delta rocket. Delta IV was designed to meet the requirements of the United States Air Force's Evolved Expendable Launch Vehicle program. Delta IV was also flown as a three-core heavy-lift launch vehicle using three Delta IV common-core boosters. Delta IV has so far launched forty-four times with only one failure and is currently planning to make its final launch in March 2024.
Part of the Delta rocket family will fly as the Interim Cryogenic Propulsion Stage on the three Block 1 Space Launch System for Artemis 1 to 3. Some online have unofficially called the Space Launch System Delta V due to this use of the Interim Cryogenic Propulsion Stage.