The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic

rocket stages A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...

used on the Delta III and Delta IV rockets, and on the Space Launch System Block 1. The stage consists of a cylindrical liquid hydrogen (LH₂) tank structurally separated from an oblate spheroid liquid oxygen (LOX) tank. The LH₂ tank cylinder carries payload launch loads, while the LOX tank and engine are suspended below within the rocket's inter-stage. The stage is powered by a single

Aerojet Rocketdyne Aerojet Rocketdyne is an American manufacturer of rocket, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Headquartered in Sacramento, California, the company is owned by Aerojet Rocketdyne Hold ...

- Pratt & Whitney RL10B-2 engine, which features an extendable carbon-carbon nozzle to improve specific impulse.

Delta III

The DCSS first flew on 3 Delta IIIs, failing two out of two times. A booster failed on the maiden flight and the rocket was destroyed by range safety, causing the loss of the DCSS before ignition. On its second flight, the stage tumbled uncontrollably, inserting the payload into a useless orbit. On the third flight, the stage performed the planned burn but fell short of the target orbit due to premature propellant exhaustion. The flight was deemed a failure. An un-flown example is on display outside the Discovery Cube Orange County.

Delta IV

Two different versions are flown, depending on variant. Composite interstages used to mate the first and second stages together accommodate the different configurations. For the Delta IV-M, a tapering interstage that narrows down in diameter from 5 meters to 4 meters is used on the 4-meter DCSS, while a cylindrical interstage is used on the 5-meter DCSS. Since the retirement of the Delta IV-M and Delta IV-M+ rockets, the DCSS is now used solely on the

Delta IV Heavy The Delta IV Heavy (Delta 9250H) is an expendable heavy-lift launch vehicle, the largest type of the Delta IV family. It is the world's third highest-capacity launch vehicle in operation, behind NASA's Space Launch System and SpaceX's Falcon H ...

in its 5-meter variation. , two missions remain before ULA retires the Delta IV Heavy.

Interim Cryogenic Propulsion Stage

The Interim Cryogenic Propulsion Stage, a minimally modified 5-meter DCSS, is used as the upper stage of the Space Launch System Block 1. The ICPS for Artemis I was mated to the SLS launch stack on July 6, 2021.Rosenberg, Zach
"Delta second stage chosen as SLS interim"
''Flight International'', May 8, 2012. The ICPS will be used for the first three Artemis missions before being retired in favor of the in-development Exploration Upper Stage for Artemis IV.

References

Cryogenic Second Stage Space Launch System United Launch Alliance Rocket engines using hydrogen propellant Rocket stages Boeing spacecraft and space launch systems {{rocket-stub