Delta Cryogenic Second Stage

The DCSS first flew on three Delta III missions, however it was never successful. On its maiden flight, a booster failed and the rocket was destroyed by range safety, causing the loss of the DCSS before ignition. The second mission saw the DCSS itself malfunction tumbling uncontrollably, inserting the payload into a useless orbit. On the third flight, the DCSS performed its planned burn but fell short of the target orbit due to premature propellant exhaustion, resulting in mission failure. An un-flown example is on display outside the Discovery Cube Orange County. upper stage being tested in January 1998 == Delta IV ==

The Delta IV launch vehicle utilized two distinct versions of the Delta Cryogenic Second Stage (DCSS) to cater to the specific launch needs. These variants are the original DCSS with a diameter that is largely identical to the version used on the Delta III and the larger version with a diameter used to lift larger payloads. These variations necessitated the use of composite interstages, which linked the first and second stages together. For the Delta IV Medium configuration, a tapering interstage was employed to transition between the 5-meter diameter of the first stage and the smaller 4-meter diameter of the DCSS. In contrast, the Delta IV Heavy configuration and some Delta IV Medium+ configurations, with larger payload capacities, utilized a cylindrical interstage that matched the diameter of its 5-meter DCSS. The Delta IV family of rockets has been retired, with a final launch on 9 April 2024. == Interim Cryogenic Propulsion Stage ==

ICPS under construction The Interim Cryogenic Propulsion Stage (ICPS) is the upper stage for the initial configuration of NASA's Space Launch System (SLS). It is a derivative of the 5-meter DCSS, with minimal modifications for SLS integration. Like the earlier DCSS, the ICPS is powered by one Aerojet Rocketdyne RL10 engine and generates of maximum thrust. Like all previous DCSS units, Artemis I used the RL10B-2 engine; however, Artemis II used, and III will use, the RL10C-2. The ICPS for the Artemis I mission was mated to the SLS launch stack on 6 July 2021. It performed as expected, providing the necessary thrust during the successful launch on 16 November 2022. The ICPS is designed as a temporary solution. Prior to February 2026 it was slated to be replaced by the next-generation Exploration Upper Stage for the Artemis IV mission and beyond; however, it is now planned to be replaced by a commercial alternative, the Centaur V. == References ==